Energy Conversion and Management 159 (2018) 398–412

Contents lists available at ScienceDirect

Energy Conversion and Management

journal homepage: www.elsevier.com/locate/enconman

Integrated approach for sustainable development of energy, water and T

environment systems
⁎
Goran Krajačića, , Milan Vujanovića, Neven Duića, Şiir Kılkışb, Marc A. Rosenc,
Moh'd Ahmad Al-Nimrd
a
University of Zagreb, Faculty of Mechanical Engineering and Navala Architecture, Ivana Lučića 5, 10000 Zagreb, Croatia
b
The Scientific and Technological Research Council of Turkey, Atatürk Bulvarı No: 221, Kavaklıdere 06100, Ankara, Turkey
c
Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, Oshawa, Ontario L1H 7K4, Canada
d
Jordan University of Science and Technology, Ar Ramtha, Irbid, Jordan

A B S T R A C T

The Conferences on Sustainable Development of Energy, Water and Environment Systems (SDEWES) at the
beginning of the 21st century have become a significant venue for researchers to meet, and initiate, discuss,
share, and disseminate new ideas in various disciplines of sustainable development. In 2002, the first conference
was organised in Dubrovnik, Croatia and since then, 10 more successful conferences were realised. Following the
success of international conferences in Dubrovnik, the organizing committees decided to organize the main
conference and regional conferences all over the world in even years. In 2016, the second regional SDEWES
conference, namely the 2nd South East European Conference on Sustainable Development of Energy, Water and
Environment Systems, was held June 15–18 in Piran/Portorose, Slovenia while the 11th SDEWES conference was
organised in Lisbon, Portugal on September 4–8. There were 10 special sessions dedicated to various sustain-
ability topics organised in both conferences.
This special issue is based primarily upon a collection of 35 papers selected from among 538 scientific
contributions presented at the 2nd SEE and 11th SDEWES Conferences. Moreover, this editorial summarises
SDEWES published articles that have addressed and identified problems or provided the background for the
research that is reported in the current special issue. The main topics of the selected papers address sustainable
combustion technologies, renewable energy sources and sector integration, including the integration of re-
newable technologies in the urban environment, the integration of heat, cold, electricity and fuel production in
buildings and industrial applications, heat exchangers and heat exchanger networks, the development and in-
tegration of energy storage for concentrated solar power plants, and sectorial integration of bioenergy resources
and biorefineries with a particular focus on system integration for efficient and low-carbon systems.

“Sustainable development is development that meets the needs of 1. Editorial introduction to special issue of the 11th SDEWES and
the present without compromising the ability of future generations 2nd SEE SDEWES conferences
to meet their own needs.”
Our Common Future, Report of the Brundtland Commission, 1987 The Brundtland Commission clearly expressed the goal of sustain-
able development and the necessity to understand, accept and ac-
“An integrated approach is essential for a sustainable energy future”
knowledge the needs of future generations for normal life and devel-
- Energy Technology Perspectives 2017 - Catalysing Energy Technology
opment. 30 years after, the set of 17 Sustainable Development Goals
Transformations, IEA, 2017
(SDGs) and 169 targets which are to be achieved by 2030 delineates an
inclusive agenda to address the challenges and complexities of sus-
tainable development. The Sustainable Development of Energy, Water
and Environment Systems (SDEWES) conference series with presented
papers, special sessions, panels, debates and publications, meetings and

⁎
Corresponding author.
E-mail addresses: Goran.Krajacic@fsb.hr (G. Krajačić), Milan.Vujanovic@fsb.hr (M. Vujanović), Neven.Duic@fsb.hr (N. Duić), siir.kilkis@tubitak.gov.tr (Ş. Kılkış),
marc.rosen@uoit.ca (M.A. Rosen), malnimr@just.edu.jo (M. Ahmad Al-Nimr).

https://doi.org/10.1016/j.enconman.2017.12.016

Available online 28 December 2017

0196-8904/ © 2017 Published by Elsevier Ltd.
G. Krajačić et al. Energy Conversion and Management 159 (2018) 398–412

networking ensures that a wide range of technical and other solutions their connections to previous SDEWES papers. As the fourth special
are provided that will stimulate actions in areas of critical importance issue of SDEWES in Energy Conversion and Management interlinkages
for humanity and the planet. between those in the current and previous special issues [3–5] are
Protecting the “Mother Earth’s” climate and combating climate emphasised.
change is just one of the 17 SDGs but one of the most crucial for long
term sustainability of life on the planet in its current form. Almost all 2. Sustainable combustion technologies
countries in the world have achieved agreement to cut the emissions of
greenhouse gasses and hold the increase in the global average tem- The dependence of the world’s energy production on fossil and al-
peratures to well below 2 °C above pre-industrial levels and to pursue ternative fuels, and related environmental pollution, remain among the
efforts to limit the temperature increase to 1.5 °C above pre-industrial greatest challenges today. The use of novel alternative fuels and new
levels. The Paris Agreement entered into force on 4 November 2016, efficient combustion technologies for sustainable utilizations of energy
thirty days after the date on which at least 55 Parties to the Convention production is essential to achieve a smooth transition to low carbon
accounting in total for at least an estimated 55% of the total global energy technologies. In this context, a special session at SDEWES 2016
greenhouse gas emissions have deposited their instruments of ratifica- on “Sustainable Combustion” was organised by Prof. Vujanović and
tion, acceptance, approval or accession with the Depositary. Prof. Costa and the current SDEWES special issue brings several papers
Actions following the agreement should reduce the risks of global on combustion science and technologies from that session.
warming and climate change and ensure that most of the places in the Among greenhouse gas emissions, methane takes an important place
world will not be hit by its impacts, while the planet, humanity and life due to its high global warming potential. In the current special issue,
as we know will continue to exist. Fossil fuels and industrial processes Bargiel et al. [6] concentrates on the negative environmental impact of
are the primary sources of anthropologic CO2 emissions that have re- natural gas released during failures of transmission and distribution
mained at about 34 Gigatons in 2016 [1]. The stability in global CO2 networks, especially in cases of remotely located pressure letdown
emissions for the last three years is promising that humanity will soon stations. In such cases, information about system malfunction is not
bend the curve of increasing CO2 emissions that must be reduced ra- immediately reported to the dispatching centre. The aim of their study
pidly thereafter to attain carbon neutrality by mid-century. Advances in was to address this problem by providing small-scale local electric
and diffusion of efficient energy conversion technologies and integrated supply using abundantly available natural gas from a distribution net-
energy management approaches are critical in meeting the reductions work as an energy vector, in order to enable installation of relevant
that are deemed necessary. communication technologies. This work represents the continuation of
The Conferences on Sustainable Development of Energy, Water and a project whose initial phase was reported in a previous SDEWES spe-
Environment Systems (SDEWES) at the beginning of the 21st century cial issue [7], where the preliminary computational model of the
have become a significant venue for researchers to meet, and initiate, thermoelectric generator (TEG) fired with natural gas was established
discuss, share, and disseminate new ideas in various disciplines of based on mass and energy balances. Simplified models are useful in
sustainable development. In 2002, the first conference was organised in early stages of design, but in order to include all relevant flow phe-
Dubrovnik, Croatia and following the new approach for even years, the nomena and its influence on spatial distribution of physical quantities
2nd South East European (SEE) Conference on SDEWES took place from that are necessary for the design of a prototype, computational fluid
June 15–18 in Piran/Portorose, Slovenia while the 11th SDEWES dynamics (CFD) should be employed [8]. In the present work of Wang
Conference took place in Lisbon, Portugal from September 4th to 8th et al. [8], a CFD model of a vertical configuration of a TEG generator
2016. The 538 contributions that were presented in the scientific pro- was generated in order to perform sensitivity analysis of design para-
gramme of these conferences have broadened the wealth of pioneering meters on the solution and to provide a set of design parameters for the
knowledge in these disciplines with a particular emphasis on system optimization procedure. Subsequent optimization was done using re-
integration for efficient and low-carbon systems. sponse surface optimization method. The objective function was max-
In previous SDEWES Conferences in Dubrovnik, Prof. Carvalho et al. imizing the temperature difference over the generator surface and the
[2] had defined the outlook for a new post carbon society and the main constraint was put on maximum hot side temperature of thermoelectric
features of future energy systems. According to this outlook, future generator module. The Central Composite Design has been used as the
energy systems will be based on renewable energy sources (RES), Design of Experiments type. The non-parametric regression has been
buildings as positive power plants, smart grids and electric vehicles, used for the response surface generation and Non-linear Programming
and energy storage. In addition to numerous distributed renewable by Quadratic Lagrangian (NLPQL) method has been utilized as the
energy solutions and opportunities, a crucial issue for achieving the optimization algorithm. As a result, three candidate points, represented
post carbon society and decarbonised economy at least cost, least en- by a set of optimum values of the design parameters, have been iden-
tropy production and exergy destruction is the integration of sectors, tified and are currently under consideration in the project phase of
processes, energy production and consumption. Integration allows prototype testing. The final choice of the optimum configuration will
many RES forms to be combined with different storage options and also take into account economic issues related to the quantity of ma-
enhances the flexibility of system operation through digitalisation, terial per type and the resulting cost of production.
advanced use of information and communications technology (ICT) and Coal power plants emit large quantities of NOx and SOx into the
artificial intelligence. atmosphere. NOx can be reduced by employing gas aftertreatment
The 35 papers in this special issue address key topics in the field of technologies, such as selective catalytic reduction [9] or selective non-
energy conversion and management and also sustain the series of sci- catalytic reduction [10], whilst SOx can be reduced by wet or dry de-
entific contributions that head towards realizing this future outlook and sulphurization process. Dry desulphurization process generates large
achieving many of the SDGs. The main topics of the selected papers quantities of sulphites compared to wet desulphurization process. Sul-
address sustainable combustion technologies, renewable energy sources phites are susceptible to reemitting SO2 to the atmosphere [11], so the
and sector integration, including the integration of renewable tech- disposal process of desulfurization residues is not suitable. As indicated
nologies in the urban environment, the integration of heat, cold, elec- previously by Mikulčić et al. [12], the use of alternative raw materials
tricity and fuel production in buildings and industrial applications, the could be one of the measurements in an effort to reduce CO2 emission in
integration of heat exchangers and heat exchanger networks, the de- the cement industry. Examples of these alternative raw materials in-
velopment and integration of energy storage for concentrated solar clude semi-dry flue gas desulfurization residues from coal-fired power
power plants, and sectorial integration of bioenergy resources and plants. Unfortunately, sulphites also degrade the cement quality and
biorefineries. This editorial is organised into these main groupings and lead to costs of landfill disposal. The work carried out by Castro et al.

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[11] had dealt with the conversion of sulphite residues from coal power investigated the physical, chemical, thermogravimetric and combustion
plants desulfurization units by means of fluidized bed treatment. An properties for different biomass fuel types. The combustion tests were
experimental pilot plant was built to oxidize residues with hot air performed in a multi-fuel boiler, showing the difference in the max-
converting sulphites to sulphates, turning them into an acceptable ce- imum output, energy conversion efficiency, gaseous emission profiles
ment feedstock. It consisted of a fluidized bed reactor, an air heater, a and ash residues produced from the fuels. It was concluded that some of
cyclone and a heat recovery exchanger. The effect of independent the combustion results could be directly correlated with the inherent
variables, residence time and temperature, was investigated and sul- properties of the different fuels. Branco and Costa [23] in this special
phite conversions up to 89.4% were observed. Experimental data were issue focus on an experimental analysis of rice husk and wheat straw
used to generate response surface of sulphites to sulphates conversion, combustion. The authors used a drop tube furnace to combust different
which allowed an estimation of independent variables influence on particle sizes of rice husks and wheat straw and to analyse combustion
conversion and optimal oxidation conditions. It has been proved that efficiency and particle matter concentration. They reported tempera-
reactor time has lower influence to conversion compared to tempera- ture profiles, particle burnout, particle matter concentration and size
ture. Finally, it was pointed out that proposed model serves only as an distribution measured along drop tube furnace. It was identified that
indication of the industrial potential for sulphites oxidation, since it was rice husk size classes present higher burnout values than the wheat
based on a small scale pilot facility. straw ones, while the particulate matter emission is similar for both
In the current special issue, Kun-Balog et al. [13] investigates the agriculture residues. It was observed that particle fragmentation occurs
pollutant emissions including nitrogen oxides of various aqueous in the last stage of combustion of wheat straw.
ethanol solutions in liquid and gaseous forms. Pollutant emission in- Previously, Mladenović et al. [24] proposed the biomass boiler
vestigations were performed using two 15 kW lean premixing swirl concept for combustion of large soya straw bales. Different biomass
burners equipped with a plain-jet airblast atomizer. One of the research fuels were tested by Duncan et al. [25] which proposed new biomass
findings was that the evaporation process does not require external pellets and provided experimental tests of tensile strength, ultimate and
energy in a heat engine application since hot exhaust gasses can be used proximate analysis, abrasion resistance, moisture sensitivity, and mass
for evaporating the ethanol and injecting it in gaseous form to the and dimensional characteristics. Combined pellet biomass and solar
combustion chamber. The authors showed that all tested alcohols are in boiler was proposed and tested for apartment buildings in Latvia [26].
line with the present Hungarian standards, and that for an upcoming After small scale laboratory testing, the authors proposed optimization
regulation in 2018. Ethanol-water 90–50% solutions when they are of the 100 kW pellet boiler. It is important to design efficient biomass
injected in a liquid form and 80–50% evaporated alcohols when they boilers so Rajh et al. [27] had advanced modelling and testing of a
are introduced in gaseous form are in line with the limitations. 13 MWth waste wood-fired grate boiler with recycled flue gas. As pre-
Renewable solid fuels, such as biomass, substitute more and more viously shown, numerical modelling is widely used in industry for de-
fossil fuels for heat and electricity production and therefore, an un- tailed understanding of the combustion process and for appropriate
derstanding of the chemical and physical properties as well as the design and optimization of biomass/waste-fired boilers. The overall
combustion of different renewable solid fuels is essential for an im- modelling strategy, the new sub-models and the use of recycled flue gas
provement of process efficiency and reduction of environmental effects. are all of great benefit or reference for modelling and design of grate-
There are even several boiler types that can accept various fuels so that fired boilers.
biomass co-firing must be optimized for each one to have similar or Striūgas et al. [28] presented in the current special issue a method
better efficiencies. Previously, Kazagic and Smajevic [14] investigated for estimating the fuel moisture content of biomass in grate fired fur-
synergy effects of co-firing wooden biomass with coal from Bosnia and nace with a boiler and a flue gas condensing economiser. All the
Herzegovina, while Smajevic et al. [15] presented results of experi- parameters of the furnace were recorded and the moisture content in
mental studies on a laboratory-scale furnace and 110 MWe power unit. the fuel and in the flue gas exiting the smokestack was measured. Based
The authors provided evidence for certain benefits in co-firing of bio- on thermodynamic equations, the heat balance of the economizer was
mass until 7%/wt of brown coal was replaced with sawdust. There was established and an algorithm was developed to automatically control
also no risk to the efficiency decrease and negative impacts to the the furnace fired with wet biomass, which estimates the moisture
combustion process. Furthermore, they showed that no modification to content in the feedstock and predictively adjusts the furnace parameters
the existing coal transport system and boiler equipment is necessary to for the optimal fuel combustion.
achieve the reported outcome. Kuprianov et al. [16] also researched Another development is put forth by Kokalj et al. [29] who de-
effects of operating conditions and fuel properties on emission perfor- monstrated that by interconnecting excess renewable power and
mance and combustion efficiency of a swirling fluidized-bed combustor sewage sludge gasification, an alternative energy storage in the form of
fired with a biomass fuel, while similar studies have been conducted by syngas can be obtained. The main objective of this study in the current
Mehmood et al. [17] where authors used simulation of combinations special issue was to find a corresponding set of gasification process
based on two coals (bituminous coal, lignite) and four types of biomass parameters of sewage sludge with known composition to ensure the
(rice husk, sawdust, chicken litter, refused derived fuel). They con- production of syngas for application in combined heat and power
cluded that net CO2 emissions should decline significantly, while the generation systems. The efficiency of power conversation to syngas
reductions in emissions of nitrogen and sulphur oxides are dependent produced from higher moisture sewage sludge was studied using an
on the contents of nitrogen and sulphur in the biomass. Comparison of equilibrium thermodynamic model for the gasification process pro-
cofiring and biomass combustion by LCA method is provided in [18] viding the calculated prediction of the syngas amount and composition.
where authors concluded that a 29% net electric efficiency biomass- This study showed a good potential of utilizing excess low priced re-
fired power plant would be required to achieve the same global GHG newable power to treat waste sewage sludge and produce renewable
emissions decrease as biomass cofiring. In recent work Kazagić et al. syngas that can be stored and with existing and proven technology
[19] provided multicriteria sustainability assessment and single criteria turned back again to renewable power.
analysis for three scenarios of biomass co-firing in Bosna and Herze- Efficient heat transfer is a prerequisite for overall efficiency of en-
govina while Moiseyev et al. [20] studied the substitution of coal with ergy conversion process. Heat exchangers still remain system compo-
biomass as a CO2 mitigation option at the EU level. Previously, Hoff- nents where energy efficiency could be further improved. Therefore, it
mann et al. [21] studied the co-combustion of coal and eucalyptus from should not come as a surprise that a large number of papers presented
energy forests in power plants in the Brazilian state of Rio Grande do at SDEWES conference series is dedicated to heat exchangers. For ex-
Sul focusing on the limits given by biomass and water availability. ample, Wang et al. [30] reviewed recent research of three kinds of
Beyond biomass and coal co-combustion, Forbes et al. [22] had surface heat exchangers. Stanek et al. [31] optimized a heat exchanger

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on the basis of a thermo-ecological objective function. Vertical U-tube combustion of IC engines, specifically on combusting alternative fuels
ground heat exchangers were optimized in [32] by employing mini- and observing various engine operating strategies. Biogas produced
mization of entropy generation and genetic algorithm. The paper in this during anaerobic digestion of sewage sludge is considered as a renew-
SDEWES special issue by Shi et al. [33] is concerned with non-uni- able energy source and as such, can be used as partial or complete fossil
formity of fluid flow in a microchannel ceramic heat exchanger. The fuel substitute for internal combustion engines. Previous work pub-
inlet part was optimized using surrogate model coupled with genetic lished in special issues of SDEWES conferences dealt with the applica-
algorithm. First, Latin hypercube sampling method was utilized for the tion of biogas in a HCCI engine [43] and dual fuel diesel engine [44].
design of sampling points which were then calculated by computational The investigation of Faria et al. [45] in the current issue addresses the
fluid dynamics. Sample data was used to establish radial basis neural performance of spark ignition engine-generator unit fuelled with biogas
network which was employed to predict the specific fluid flow dis- produced in a sewage plant. Experimental emissions and performance
tribution within design space as a surrogate model. The novelty of the measurements that were obtained during varying of the equivalence
research is reflected in the fact that the surrogate model predicts the ratio and spark ignition indicate that the penalties to engine perfor-
specific flow distribution instead of a single target value of non-uni- mance were more significant than emission reduction in the operating
formity. Finally, the genetic algorithm was implemented to find the range tested, which is in agreement with the literature. In addition, zero
optimum solution. Geometry generated by optimization procedure re- dimensional simulation model was employed to predict performance
duced by 68.2% non-uniformity of fluid flow, at the same time in- characteristics. The solution procedure was separated into three dif-
creasing the pressure drop by only 6.6%, compared to the initial solu- ferent steps, which were compression, combustion and expansion. The
tion. input to this model includes engine geometric data, engine design in-
SDEWES conferences have paid a special attention to contribute to formation, fuel data, combustion parameters and engine operating
the internal combustion engine efficiency improvement. Various in- parameters. Specific fuel consumption and indicated power were se-
vestigations have been performed for that cause, such as combusting lected as output parameters and were compared to experimental data
alternative fuels, detailed 1D/3D CFD modelling, and investigation of with discrepancies lower than 5%. The model can be adapted for use
different engine operating strategies. For example, the research in [34] with different biogas compositions and could prove to be a valuable
deals with the 3D CFD modelling of biofuel addition to the conventional tool to guide experimentation and to extract maximum performance
diesel engine where authors pointed out difficulties in comparing pol- from engines, while simultaneously reducing harmful emissions to the
lutant emissions while using different fuel blends. In the research of atmosphere.
[35], authors performed 3D CFD simulations by employing the Large- In the research of Vihar et al. [46], the authors analysed the pos-
eddy simulation (LES) approach for investigating the influence of dif- sibilities of extending the operating range of the automotive Diesel
ferent gas species on the turbulent flame speed and consequently, on engine powered with an alternative liquid fuel produced by pyrolysis of
the flame-induced turbulence. The research of [36] deals with experi- waste tires. In order to extend the operating range to low-load condi-
mental analyses of engine powered by diesel fuel blended with palm tions, authors proposed a novel approach by combining the use of ex-
and/or coconut biofuels. The authors found that biodiesel blends pro- haust gas recirculation and tailored main injection strategy. In addition,
duce a low brake torque and a high brake-specific fuel consumption. authors focused their research on the investigation of particulate
However, all emissions, except for NOx, are significantly reduced. In emissions arising from combusting tyre-pyrolysis fuel by employing two
addition, authors revealed that the diesel blending with both the palm different measuring methods, the photoacoustic method and the
and with the coconut biofuel shows superior performances over in- gravimetric method. This research pointed out that the tyre pyrolysis
dividual biodiesel blends. The influence of the bioethanol and diesel fuel can be used without the use of cetane improvers or external energy
fuel blending on the engine performance was discussed in [37] where addition. A significant contribution of this work was achieved by ela-
authors pointed out that the given fuel blend, with different bio- borating on the differences in measurement of soot emissions by em-
component concentrations, reduced the overall particulate matter ploying two different methods.
emissions. It is known that internal combustion engines can operate in a The research of Wang et al. [47] deals with the LES CFD modelling
dual fuel mode, combusting two different types of fuel, and therefore, of fuel injection and combustion processes in a direct-injection natural
researchers are constantly developing new ideas in that direction. The gas engine. The authors analysed the influence of fuel injection timing
research of [38] is focused on the experimental investigation of dual and positioning of the ignition process on the total kinetic energy,
fuel combustion of bioethanol and gasoline fuel in a redesigned diesel pressure traces and released heat. They have noticed that the main
engine. The authors pointed out the influence of biocomponent addi- mechanism of how fuel injection timing influences the combustion is
tion on the maximum pressure, NOx, soot, HC, and CO emissions. the influence of velocity field and formation of relatively richer fuel-air
Multiple papers dedicated to SDEWES conferences deal with 3D CFD mixture around the ignition position. Furthermore, the authors pointed
modelling of processes occurring within the internal combustion out that the ignition position determines the background distribution of
chamber. For example, in the research of [39], authors showed a de- the velocity magnitude and confines the available space for flame de-
tailed investigation of a single cylinder engine by calculating pollutant velopment.
emissions for different engine operating points. This research was later In contrast, the research of Wang et al. [48] deals with the effects of
extended in [40], where the authors used an advanced modelling ap- exhaust gas recirculation at various loads on diesel engine performance
proach capable of describing the processes in the near-nozzle region. In and exhaust particle size distribution using different fuel blends. This
the research of [41], authors combined experimental research and the research deals with the problem of emitting a vast amount of ultra-fine
3D CFD approach to calculate the low pressure and high-pressure cycle particles when compression ignition engine is powered by gasoline-like
and to investigate the influence of various combustion parameters on fuels. The authors tested several fuel blends under different engine
the cycle efficiency. An interesting research of [42] showed the results loads and exhaust gas recirculation (EGR) composition. An ultimate
of direct injection engine operating in a dual fuel mode powered by the conclusion of this paper is that when using gasoline fuel blended with
used transformer oil and acetylene blend. The authors showed that the various additives and in a high EGR rate, a nearly zero soot emissions
usage of the used transformer oil, in the observed engine configuration, could be achieved. However, the authors noticed that, for all fuel
can lead to lower nitric oxide and higher smoke emissions, compared to blends, a higher amount of smaller particles are emitted compared to
the pure diesel fuel. They also revealed that the smoke emissions can be the combustion of conventional diesel fuel.
further reduced by blending the used transformer oil with acetylene In the current special issue, Pirker and Wimmer [49] presented a
loaded into the combustion chamber with specific flow rates. review of the technologies that can be used in large internal gas com-
In this SDEWES special issue, several papers deal with the bustion, and the technological challenges and requirements that the

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next generation of internal gas combustion engines will meet during the revolution: How photovoltaics will change electricity markets in Europe
transition from conventional to carbon free fuel sustainable power fundamentally” [52]. A year after, similar work has presented how solar
generation systems. It was identified that alternative fuels and waste energy can decarbonize the power sector [53]. The authors gave the
gases consumption is rising and present new challenges in the research economic potential of photovoltaics and concentrating solar power to
and technological developments in gas engines. They identified dif- conclude that solar power will play a paramount role in the long-term
ferent technologies required to meet these challenges, such as im- transformation of the electricity system. As prices of PV technology are
provements in robustness and dynamic behaviour, which will enable rapidly dropping, more installations have been added and many au-
gas engines to compete with standard diesel engines. Development of thors envisaged a high penetration of technologies for intermittent re-
advanced ignition concepts and combustion concepts itself for en- sources. Options for high penetration of PVs integration are discussed in
hanced fuel flexibility and the simulation of transient multi-cylinder [54] where authors concluded that high penetration of PVs in a de-
engine behaviour on single cylinder research engines test bed are ad- velopment area is feasible and may even reduce grid infrastructure
dressed as one of the primary development goals for the gas engine costs. There are also benefits in system operation and voltage quality
applications in future. improvement when PVs are installed. As concluded by Galzina in [55]:
Wang et al. [50] brings another perspective on oxy-fuel combustion “Even though PV systems are said to be the cause of many disturbances,
based on thermogravimetric analysis. The catalysis extent is affected by operational results are in contradiction to that hypothesis. Using modern
potassium type, doping concentration, oxygen concentration, and at- active filters with controllers and voltage source converters, PV systems can
mosphere. Results show that the catalytic role of potassium in oxy-fuel produce flawless energy, and even improve the condition of the grid at the
combustion is lower than that in air combustion. The promotion degree point of common coupling by its operation, making solar energy clean, not
of potassium doping presents the minimum value at around a 15% O2 only ecologically, but also from a technical point of view.” Bottom-up in-
concentration. The catalytic effect of K2SO4 will not change and even itiative of citizen-funded and citizen-operated photovoltaic power
decreases at 375 μmol(K)/g(soot) for K2SO4 while the catalytic role of plants are important for further integration of PV plants [56]. However,
KCl keeps increasing even at 600 μmol(K)/g(soot) for KCl. In the O2 as concluded in [57] it is very important to study the right tariff me-
concentration range of 5–30%, the accelerating degree from K-doping chanisms and benefits to avoid financial disturbances on the market
presents the minimum value around 15%. This phenomenon strongly and to promote integration in a real competitive market.
approves potassium as the oxygen carrier accelerating the oxygen Large scale integration of different intermittent renewable sources
transportation, because in the cases without K-doping and at a high O2 has received even greater attention during SDEWES conferences by
concentration, there is no additional active site for more O2 adsorption, many authors with a particular focus on the integration of wind and
thus inducing the slow accelerating degree. The kinetic analysis in- solar energy. Electrifying Greece with solar and wind energy was pre-
dicates the first order reaction for soot oxidation and also a good sented in [58]. The authors proposed a scenario to install wind capacity
compensation relation between apparent activation energy E and of 5825 MW which is about 1 GW more than the official business as
logarithmic frequency factor A. E is generally reduced with the atmo- usual scenario (BAU), which aims at the installation of an additional
sphere changing from O2/N2 to O2/CO2, with K-doping, and with 4834 MW wind turbines until 2020. The authors’ proposal for addi-
O2 concentration decreasing. tional PVs installation in their Green scenario reaches almost 2000 MW,
In addition to sustainable combustion, making current systems for which is 2 GW more than the official BAU scenario. With a cumulative
exploitation and production of existing natural and fossil fuel resources installed capacity of 7500 MW of wind and 2200 MW of PVs and after
more efficient is also crucial for sustainable development. Dehydration replacing 19,509 GWh of lignite and oil based electricity generation, it
is a critical operation in natural gas conditioning as it reduces the po- is estimated that CO2 emissions will be in 2020 almost 19 Mt less than
tential for corrosion, hydrate formation and freezing in process equip- emissions in 2010. Similarly, the authors in [59] analysed many sce-
ment and transportation pipelines. In the current SDEWES special issue, narios for the development of the Croatian energy sector until 2030
Santos et al. [51] investigates the impact of increasing carbon dioxide with different wind and solar penetration levels. All of the scenarios
content in natural gas dehydration by molecular sieve in offshore were subjected to a multiple criteria decision analysis in order to find
plants. The study evaluates the impact of the CO2 composition of the the best overall scenario, which showed to be 1.65 GW of wind power
natural gas on the performance on dehydration by solid adsorbent plants and 1.6 GW of installed PV capacity. Previously, many authors
through process simulation. The results reveal that although adsorption also modelled energy systems with combined wind and solar energy
meets water removal specification in a condensation free operation, the gross shares of up to 100% of the total demand. 100% RES penetration
high fugacity of CO2 penalizes the dehydration performance due to was studied in the case of Ireland [60] with description of the first steps
adsorption competition with water, impacting desiccant volume re- to be taken, similar study was done for Portugal [61]. Recent work
quirement. The evaluated scenario is challenging – ultra deep-waters investigated investment needs in the case of 40–100% renewable en-
and varying CO2 concentration due to the destination of CO2 (separated ergy shares for power supply in France by 2050 [62]. Similarly, the
on the topside of offshore processing unit - FPSO) to enhanced oil re- authors in [63] showed that the potential for arbitrage of wind and
covery. Water dew point adjustment is particularly challenging in the solar surplus power in Denmark is very limited for a 100% share if wind
remote ultra-deepwater natural gas reserves of the Brazilian Pre-Salt energy is used alone as surplus energy grows rapidly beyond gross
fields due to their very high carbon dioxide contents – from 30% up to shares of about 50%. A scenario with a wind-solar energy mix of 80/20,
90% in raw natural gas. The results in paper [51] fill a gap in the lit- on the other hand, both decreases the total amount of surplus and has a
erature and are relevant as dehydration impact area of the FPSO, which significantly higher potential for arbitrage of the remaining surplus.
is constrained in footprint/weight. However, beyond gross shares of about 75%, only large-scale seasonal
storage, e.g. hydrogen, enables the use of Danish surplus wind and solar
3. Renewable energy sources and sector integration energy to cover the residual Danish electricity demand in both sce-
narios. In the case of 100% penetration, the request for storages and
As shown by many authors during SDEWES conferences, renewable system balancing could be reduced if larger areas, energy efficiency
energy sources, particularly solar energy and technologies used for its measures and technologies are integrated as showed by the authors for
harvesting, are crucial for enabling the transition to more sustainable the case of area of South East Europe in [64] or as Schlachtberge et al.
energy systems as systems that will be able to withhold average global [65] explained for Germany and Europe.
temperature rise below 2 °C. Integration of intermittent renewables could be easier when energy
The impacts of photovoltaic (PV) uptake on the prices in electricity sector is connected to the water use and production, such as in the case
markets had been characterised in the paper on “The looming of Jordan [66], where authors studied the impacts of reverse osmosis

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desalination on integration of electricity from wind and PV. As ex- respectively.

plained in the paper [67], it may be also integrated with large scale The integration of photovoltaic and thermal collectors is not just
pump storage with desalination. proposed for off grid small applications in processing of agricultural
Such papers referenced above analysed integration of intermittent products as shown in [75]. Previously conducted analyses of the energy
sources from the point of large scale energy or interconnected power and economic performance of roof and façades building integrated flat-
systems while there are many developments on a small scale where plate photovoltaic and thermal (BIPVT) collectors showed their possible
benefits of renewable sources are more visible and higher penetrations application in residential applications. Buonomano et al. [77] calcu-
could be achieved sooner. In both grid and off grid applications, small lated that the adoption of BIPVT panels could produce a decrease of the
or large systems, it is important to take into account possibility for primary energy demands from 67% to 89% for different weather lo-
integration of PVs as close as possible to the centre of consumption. cations and the building-plant configuration. Moreover, the passive
Previously, the advantage of building integrated PVs had been effects of the BIPVT system are visible in both the winter and summer
studied for the Canary islands archipelago by Schallenberg in [68]. One seasons in all investigated climate zones and the calculated pay back
limitation in the archipelago is the lack of available land. Considering periods vary from 11 years for South European weather zones to 20 for
both issues, land scarcity and energy goals, it was crucial to determine North European ones.
the PV potential on roofs for further integration. Another study of Pa- In a new work described in the current SDEWES special issue,
lermo city on Sicily tested the level of integration of the photovoltaic Buonomano et al. [78] provided a calculation of an even more in-
technology in urban areas [69]. After classifying roofs according to tegrated BIPVT system. The authors combined an innovative poly-
their shape, orientation and pitch by means of satellite images provided generative system layout based on a building integrated photovoltaic
by Google Earth, the ratio of the productivity of the PV systems and the thermal system coupled to an adsorption chiller and to an electricity
consumption of electricity of the households was analysed. However, storage system. For the assumed configuration, they made a dynamic
there are also authors that argue that the optimal inclination and or- simulation model used for the energy, economic and environmental
ientation of PV systems in urban areas is not as crucial as the effective analysis. The electricity produced by BIPVT is used to satisfy the
utilization of rooftop space which might be scarce. As the cost of building needs while the eventual extra-production is delivered to the
photovoltaic systems has fallen radically in recent years, while the grid or stored in lead-acid batteries. It is important that simulation
output decrease per capacity installed is within single-digit percentage results show that the obtained simple pay back times, the primary en-
points for tilt angles lower than “optimal,” an accordingly small in- ergy saving for electricity and domestic hot water production, and the
crease in levelized cost of electricity should most definitely be accep- equivalent CO2 avoided emissions range between 10.6 and 11.3 years,
table compared to the described increase in electricity production 58.5–68.8% and 76.3–90.2%, respectively.
achieved per area unit of rooftop or other space utilized [70]. There are As previously shown by authors of papers presented at SDEWES
many parameters to be analysed in the deployment and design of PV conferences, it is important to use real measured data in the evaluation
systems, such as density of peak power, final system yield, density of of installed equipment for heating and cooling in buildings, including
energy, yearly energy per unit of collection area, internal return factor, renewable energy technologies, as results obtained by applying stan-
NPV, energy payback time, energy return factor, energy surplus, and dardised methods could differ significantly from the measured ones. In
avoided CO2 emissions. The study methods that can analyse different another SDEWES special issue, Horvat and Dović [79] had presented a
parameters for the owners, designers or promoters of the PV installation new approach for the estimation of buildings technical system energy
has been shown in [71] while also presenting an implementation case performance. The authors developed new methods consisting of a
study based on the central flat roof of the Torres Quevedo building of mathematical model for an accurate prediction of indoor temperature
the University of Zaragoza (Spain). and heat losses of the space heating and domestic hot water system
On the contrary to grid connected urban areas, PVs are effectively components. The results are compared against those obtained from EN
integrated into off-grid applications and used in electrification of dif- ISO 13790 and standard series EN 15316. Similar to Herrando et al.
ferent areas as showed for renewable energy based electricity genera- [80], the comparison shows significant differences in determination of
tion for isolated grids in Croatia's rural areas [72] or for electrification the annual delivered energy to the heating system (33%), as a con-
using solar photovoltaic systems in Nepal [73]. Among other technol- sequence of the difference in estimation of the energy need for heating
ogies, stand-alone photovoltaic pumping systems are often installed in (15%) and calculation of the technical systems recoverable heat losses
remote areas where the grid is not available: they are used for irrigation utilization factor, which seems to be underestimated. The delivered
and/or other local water needs and can supply also electricity to small energy to the space heating and DHW system differs by 25%.
consumers. In [74], a particle swarm optimization based model for the A configuration of an integrated polygeneration system with pho-
optimal management of a small PV -pump hydro energy storage in a tovoltaic/thermal collectors, solar assisted heat pump, adsorption
rural dry area has been presented. Smaller hybrid solutions of photo- chiller, and electrical energy storage is analysed in the current SDEWES
voltaic/thermal solar collector suitable for drying of agriculture pro- special issue. Calise et al. [81] present the system model that includes a
ducts have been previously modelled and presented by Slimani et al. more detailed electrical energy model for user storage and exchange
[75]. with the grid along with a detailed building model. In particular, the
Evidently, PV systems are becoming integrated into many applica- analysis focuses on the real electrical demands of several types of users
tions like agriculture production where they can provide energy ne- including the analysis of the comfort of building users. The work bases
cessary for heating, cooling, water pumping, etc. In the current the calculations on measured electrical demands of real two users of the
SDEWES special issue the concept of using grid connected PV in the service sector. The system performance is analysed with two different
Mediterranean climate to achieve nearly zero energy greenhouse for electricity supply contracts: net metering and simplified purchase/re-
production of three agriculture crops, cucumber, tomato and lettuce sale arrangement. Daily, weekly and yearly results are presented to-
was presented in [76]. The authors calculated monthly and annual gether with the results of sensitivity analysis. Results for a net metering
heating, cooling and lighting energy load of the greenhouse for these contract achieve better economic profitability compared to the simpli-
agricultural products and made an analysis of a ground source heat fied purchase/resale arrangement.
pump system coupled to PV. The simple payback time of the crop BIPVT systems are also the focus of the work presented by
cultivations was also computed between 7.0 and 7.4 years. The energy Fernandes et al. [82] in the current SDEWES special issue. The authors
payback time of the system was found to be 4.9 years and the green- evaluate possible ways of minimizing the effect of the shading prop-
house gas payback time value of 5.7 years while 2.6 years were calcu- erties inherent to concentrating collectors that are fixed to building
lated based on natural gas and coal based electricity generation, structures. Several solar cell string configurations in the photovoltaic

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modules are simulated using a simulation program LTPSPICE for in- having in mind that it does not represent the generality of the possible
tegrated circuits, looking for a mitigation of the effects of shading and/ applications of pumps running as turbines. Previously, similar in-
or non-uniform illumination of the solar panel. The results show which tegration of renewable hydropower generation as a co-benefit of ba-
of the simulated configurations that use overlapping by-pass diodes can lanced urban water portfolio management and flood risk mitigation was
ensure improvements in solar collector performances. presented in [86]. The study also provided evidence that Sydney’s in-
terdependent goals of deferring capital intensive flood storage works,
4. Integration of renewable technologies in the urban maintaining water security, better utilizing existing desalination and
environment hydropower assets, and increasing renewable energy generation can be
achieved through applying systems thinking to a complex citywide
Solar collectors are not just successfully integrated into various water planning problem [86]. Interesting concept of integration of
parts of buildings. They can be effectively integrated into other urban ground source heat collectors in the base of individually water har-
infrastructure. In the current SDEWES special issue, Nasir et al. [83] vesting tank as part of rainwater harvesting system was given in [87].
emphasised the capabilities of the road pavement solar collector system It is important to enhance the integration of renewable energy
to dissipate high temperature from the pavement/road surfaces not sources, PV, BIPVT, and water networks in order to reduce consumption
only to expand its lifecycle but also to reduce the Urban Heat Island or ensure self-sufficiency. In the urban context, buildings represented
effect. The authors used Computational Fluid Dynamics models in order 146 EJ or about 40% of the total of 365 EJ energy use for all sectors in
to better understand the complicated connection of the urban en- cities in which 94 EJ was for electricity and heating and 52 EJ was for
vironment and the road pavement. Results show the impact of the the direct usage of energy resources [88]. Such an energy use corre-
urban form on the performance of the road pavement solar collector sponded to 8 Gigatons of CO2 emissions from buildings in the urban
focusing on comparing symmetrical and asymmetrical height of the context alone [88]. For this reason, in addition to transport and in-
urban street canyon. The simulation was carried out based on the dustry within urban areas, solutions for buildings are a vital component
summer month of June in Milan urban centre, Italy. The method pre- for improving urban self-sufficiency and environmental performance. In
sented in this research could be useful for studying the system in- a future outlook, as explained by Prof. Carvolho [2], buildings in future
tegration in various urban forms. energy systems should be energy positive, which means that they can
Another interesting integration of novel technology for utilization of generate more energy than they consume within a certain timeframe,
renewable energy sources in buildings and urban environment is pro- usually over one year.
posed in the current SDEWES special issue by Aquino et al. [84]. The Solutions presented for the increased penetration of renewable en-
work focuses on the low energy harvesters such as the aero-elastic belts ergy sources in the energy networks of cities can be effective in the
that are suitable for integration with wireless sensors and other small- development of net-zero energy (NZEB) buildings and neighbourhoods.
scale electronic devices. These devices operate in the microWatt to Previously at SDEWES conferences, the target for a net-zero exergy
milliWatt power range and will play a significant role in the future of district based on the quality of energy was defined by Kılkış [89] in
smart cities providing power for extended operation with little or no which the Rational Exergy Management Model was used to match the
battery dependence. In their work, the authors use Computational Fluid grade/quality of energy resources (exergy) on the supply and demand
Dynamics to model a flow around the building integrated with aero- sides to near the proposed target. Net-zero exergy districts produce as
elastic belts (electromagnetic transduction type). Results show the im- much energy at the same grade or quality as consumed on an annual
pact of the belt locations and wind direction on speed and related basis. The work on net-zero districts was extended by Kılkış in [90]
power output which is determined in the study by regression analysis where a 4 step approach for the design of net-zero exergy districts was
and experimental data. The authors of another paper [84] also describe proposed for a district in Sweden. In [91] improvements for the phases
the current status of vibration energy harvesting technologies, scopes, of the same district, including exergy per capita, was compared with the
advantages and limitations. Finally, the important conclusion from the city in which the district is located. Previously, the urban energy
paper is that there is a potential for further scaling up the system in challenge was also addressed by Assoumou et al. [92] based on the case
terms of size and configuration, with the plausibility of constructing an study for the city of Bologna's energy system transformation by 2050.
array of aero-elastic belts. The authors proposed a method that combines a bottom-up dis-
Future smart energy systems will depend on successful integration aggregation of energy demands by fuel type and end-uses at sub urban
between different smart networks placed in the urban environment. level with the simulation of a large number of discrete long term al-
These networks represent smart electrical grids, smart thermal net- ternatives. The best options found by the authors could reduce Bolog-
works for district heating and cooling, smart gas and water networks, na's final energy consumption by 52% and its CO2 emissions by 83.5%
smart telecommunication networks, smart sewage system, etc. The ef- [92].
fective way to integrate water networks and electrical grids is to install The labelling of energy positive neighbourhoods as proposed by Ala-
in the water networks turbines that can operate as pumps. In the cur- Juusela et al. [93] is another essential step towards promoting districts
rent special issue, Barbarelli et al. [85] made a contribution to the so- with sufficient or beyond sufficient annual energy supply from local
lution of this subject both through experimental and theoretical activ- renewable energy sources. Contrary to the neighbourhood level, the
ities. The experimental activity is carried out by the characterisation of certification and eco-labelling of buildings has been studied more fre-
12 pumps measured, at test rig both in their natural operation, as quently. Previously, Franzitta et al. [94] described holistic and by-
pumps, and in reverse mode, as turbines. The numerical activity starts components approaches to European Eco-label brand for residential
from the definition of correlations regarding the heads and capacities buildings, while in the same SDEWES special issue, Malmqvist at al.
conversion factors, useful for the preliminary selection of a suitable [95] described a Swedish environmental rating tool for buildings. With
pump to run as a turbine in a microplant for a given hydropower site. the other group of co-authors, Malmqvist at al. [96] provided methods
Then, a statistical method involving polynomials was implemented, and guidelines for Life cycle assessment (LCA) in buildings. More work
allowing the performance curves to be provided. The agreement be- on classification and energy consumption of large residential buildings
tween experimental data and numerical results is comparable to that stocks was provided by Filogamo et al. [97].
obtained by others authors. Finally, a comprehensive procedure has
been set up, refining the selection by evaluating likewise if the effi- 5. Integrating heat, cold, electricity and fuel production into
ciency of the selected pump to use as a turbine, at the operating point of buildings and industrial applications
the proposed plant, is acceptable. The results related to a study case are
shown with the aim to highlight the easiness of the proposed method, It is important to integrate solutions for heat, cold, electricity and

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fuel production into buildings at the beginning of the planning process consisted of a solar field equipped with flat-plate photovoltaic/thermal
of construction. In their previous works, Kovacic et al. [98] provided a collectors, coupled with a water-to-water electric heat pump/chiller.
possible approach to the optimization of building construction. They The electrical energy produced by the hybrid collectors is entirely
showed that the early building design phases play a crucial role for the supplied to the building. The results showed that thermal and electrical
determination of building's life cycle performance in terms of resources efficiencies are above 40% and 10%, respectively. The Coefficient of
and energy consumption and development of LCC (life cycle costs). Performance of the reversible heat pump resulted above 4 for both
Similar conclusions were provided by Russell-Smith et al. [99] as they heating and cooling modes. For the base case, a Simple Pay Back period
combined LCA and target value design (TVD) to rapidly produce more of 5.36 years was found.
sustainable building designs. By establishing site-specific sustainability In the current SDEWES special issue, Calise et al. [112] develops a
targets and using dynamically-updating LCA, they demonstrated that novel tool for thermoeconomic analysis of trigeneration. Detailed nu-
buildings can be designed to perform at higher environmental standards merical analysis of a Combined Cooling, Heating and Power system is
than those designed without a target in place. Their paper analysed the presented, aiming at determining its optimal operating strategy in a real
trade-offs between design and operational decisions. In a previous industrial application. The authors studied three different cases: base-
SDEWES special issue, Marinakis et al. [100] presented an integrated load operation, electric load tracking and a new hybrid strategy based
system for buildings’ energy-efficient automation. Their system was on the simultaneous tracking of electric and thermal-loads. The results
based on a prototype software tool for the simulation and optimization showed that the optimal capacity of the system was lower than that
of energy consumption in the building sector, enhancing the inter- selected by the designers of the real unit to be installed. The hybrid
activity of building automation systems. control strategy obtained the best profitability, achieving a simple pay-
Even highly efficient cogeneration or trigeneration units should be back period equal to 3.8 years, compared to 4.1 years achieved in case
applied whenever possible to maximise the utilization of primary re- of electric-load tracking.
sources, such as biomass. Trigeneration systems could provide self Polygeneration systems can also integrate production of important
sufficiency for buildings or neighbourhoods and cities so it is important commodities for communities, such as water production, with pro-
to optimise the size of equipment, construction and operation strate- duction of electricity, heat and cold. In the current SDEWES special
gies. issue, an exergy analysis and thermoeconomic cost accounting of a
Previously, Usón et al. [101] presented a thermoecological evalua- Combined Heat and Power steam cycle integrated with Multi Effect
tion of a trigeneration module based on an Internal Combustion Engine Distillation-Thermal Vapour Compression plant is performed by Catrini
fuelled with selected fuels of various origin. Another optimization of a et al. in [113]. The goal of the study is to show how methodologies
trigeneration system in the building sector was previously addressed by provide a rational criterion to allocate production costs on electricity
Piacentino et al. [102]. The authors provided an upgrade for the soft- and freshwater in a dual purpose system. After a brief overview on the
ware that simultaneously optimizes the plant layout, the sizes of the methodology and a description of a reference plant, exergy analysis is
main components and their operation strategies. Optimization of a carried out to calculate exergy flows and exergy efficiencies at the
trigeneration plant and its economic viability related with external component level. A detailed description of the adopted thermo-
conditions like energy prices and support mechanisms was also ad- economic model is provided and tested on two scenarios. In the first
dressed previously in [103,104]. The authors in [102] used a specific scenario, cost accounting is performed assuming that the concentrated
building in the hotel sector in order to identify the most promising plant brine is disposed back to sea, while in the second scenario, conversely,
configuration, in terms of the type of cogeneration unit (either micro- part of brine exergy is used in a Reverse Electrodialysis unit to produce
turbine or diesel oil/natural gas-fueled reciprocate engine) and an ab- additional electricity. In both cases results show that high unit costs are
sorption chiller. Similar configurations were proposed by Dominković obtained for the material streams or energy flows which involve major
et al. [105] while applications of trigeneration systems in tertiary sector exergy destruction along their production process, particularly fresh-
was proposed by Carvalho et al. [106]. As shown recently, Di Palma water in the former configuration and Reverse Electrodialysis electric
et al. [104] provided an economic analysis of trigeneration systems output in the latter one.
through a calculation model developed for applications in the field of In contrast, in the aspect of micro cogeneration, previously Sornek
large retail sector. Furthermore, an optimization problem of binary co- et al. [114] presented original results in the field of determining the
generative power plant with high temperature solid oxide fuel cells possibility of the use of a thermoelectric generator to achieve self-suf-
(SOFC) on solid fuel with a higher power was investigated in [107] ficient operation of the stove-fireplace with accumulation. The results
while Rokni et al. [108] provided thermodynamic and thermoeconomic provided a good basis for developing a micro cogeneration system
investigations of a small-scale integrated gasification SOFC and Stirling powered by renewable energy sources. The maximum power of the
engine for combined heat and power (CHP) with a net electric capacity generator would not exceed ca. 30 We and currently there is no eco-
of 120 kWe. Woodchips are used as gasification feedstock to produce nomic justification for such a device. In the presented units, the tem-
syngas, which is then utilized to feed the anode side of the SOFC stacks. perature of the flue gas should be kept at a certain level for the purposes
A thermal efficiency of 0.424 (lower heating value) for the plant is of storing heat, which results in certain limitations for the thermo-
found so that 89.4 kg/h of feedstock is used to produce the above electric generators.
mentioned amount of electricity. Recently, Angrisani et al. [109] pre- As industrial applications, the integration of geothermal energy into
sented an index framework for analysing performance of polygenera- an industrial, food processing plant has been analysed in the current
tion energy systems, together with thermo-economic analysis and sen- SDEWES special issue by Yildirim and Genc in [115]. The authors
sitivity analysis. The work included results from the IEA Annex 54 provide energy and exergy analysis of a milk powder production line
project on the Integration of Micro- Generation and Related Energy that uses geothermal fluid. They also provide the fundamental mass,
Technologies in Buildings. A brief review of micro-trigeneration sys- energy and exergy balance equations and calculated exergy destruc-
tems for residential applications was reported in [110]. An innovative tions and exergetic parameters of the system for steady state and steady
building-integrated micro-trigeneration system based on a natural gas- flow process. The exergy destruction and exergetic performance in-
fueled internal combustion engine was also proposed in [110]. Pre- dicators of each component and the whole system were estimated for
viously, Calise et al. [111] had provided a thermoeconomic optimiza- processing of 1 kg/s pasteurized milk. The overall exergetic efficiencies
tion of a solar-assisted heat pump based on transient simulations and of the milk powder production system were found between 50% and
computer design of experiments. The plant simulation model was based 71%, for the geothermal fluid temperature of 150 °C and 90 °C, re-
on TRNSYS and designed to supply electricity, space heating or cooling spectively. Calculated improvement potential rate is the highest for the
and domestic hot water for a small residential building. The system evaporator at 191.1 kW followed by the heater at 54.4 kW and the spray

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drier at 9.3 kW. surface heat exchanger as one of the most promising candidates for
microturbine recuperators. The authors conducted naphthalene sub-
6. Integration of heat exchangers and heat exchanger networks limation experiments to investigate the heat transfer and pressure drop
performance in CW primary surface channels. Developed numerical
The growth of industrial production can challenge projected levels model with the multi-periodic boundary conditions and the linearly
of CO2 emissions. Previously, Akashi et al. [116] showed the im- decreasing wall temperature boundary is suitable for numerical simu-
portance of research on future trends in emissions from the industry and lations of the CW primary surface channels. The authors also found that
possibilities for their reduction potentials in order to make a plan for a friction factor obtained from the enlarged CW channels are suitable for
low carbon society. Even though many emission savings could be rea- the prediction of similar CW channels with the small size.
lised by fuel switching, the integration of many processes in order to Recently, Grabowski et al. [130] presented numerical simulation
increase efficiency is also a way for achieving the decarbonisation of the and experimental verification of heat transfer from a finned housing of
industrial sector. Many authors have addressed this issue in previous an electric motor. The authors investigated heat conduction in the
SDEWES conferences, emphasizing that energy efficiency, efficiency of finned housing of an electric motor and compared results of numerical
energy transformations and energy recovery should be ensured through analysis with experimental data to verify the suitability of numerical
different integration to avoid unnecessary entropy production and to simulation as an engineering tool for motor design improvements. 3D
make processes more cost effective and environmentally friendly. geometrical model of the motor rated 7.5 kW was imported to COMSOL
Heat exchangers and heat exchangers networks are the key com- Multiphysics software package to investigate the temperature dis-
ponents for integration between sectors not only using heat and cold tribution. Measurements were carried out using FLIR SC7600 thermo-
energy but also thermal storages as well as providing different trans- vision camera and steady-state temperature distribution on the surface
formations like power to heat or enhancing efficient power to fuel of housing of the motor run in idling conditions was recorded. Relative
processes and different fuel production in biorefinery systems. differences between simulated and termographically measured tem-
Thus, optimising heat exchangers in industrial processes have been peratures of the fin surface did not exceed 10% after which authors
prioritised by many SDEWES authors. Recently, Pintarič et al. [117] concluded that the temperature distribution may create a convenient
presented a robust computational methodology for the synthesis and basis for structural analysis of the housing accounting for thermal
design of flexible HEN (Heat Exchanger Networks) having large num- stresses.
bers of uncertain parameters. Their methodology combined several It is clear that research in heat exchangers and HEN were the im-
heuristic methods, which progressively lead to a flexible HEN design at portant topics at previous SDEWES conferences. In the current special
a specific level of confidence. Previous work on HEN was also focussed issue, several papers also addressed the problem of efficient and cost
on optimization approaches for improving energy recovery in retro- effective heat exchangers.
fitting HEN as showed by Pan et al. [118], optimization of the entire life In the current issue, Shi et al. [33] show the importance of new
economy of HEN as given by Nemet et al. [119] and simultaneous materials for integration of heat exchangers in various processes. High-
synthesis of process water and HEN by Ahmetovic and Kravanja [120]. temperature resistance and corrosion resistance make ceramic materials
Moreover, pinch or similar methods have been used to optimise HEN. available for heat exchangers operating under high temperature or
For example, Zhang et al. [121] reported on sustaining high energy harsh chemical conditions. The authors show how the reduction of
efficiency in existing processes with advanced process integration nonuniformity of fluid flow can improve the performance of a micro-
technology while Boldyryev et al. [122] provided a methodology for channel ceramic heat exchanger. The inlet part of a microchannel
decreasing the capital cost for Total Site heat recovery by use of dif- ceramic heat exchanger is optimized using surrogate model coupled
ferent utility levels. Wan Alvi et al. [123] presented an approach that with genetic algorithm. The genetic algorithm is implemented to search
considers heat losses and heat gains during the establishment of for the optimal point. The nonuniformity of fluid flow is reduced by
minimum utility targets. 68.2% and pressure drop is increased by 6.6% by the optimization,
Although optimization of HEN is important, it is also essential to which means the uniformity of fluid flow in the heat exchanger is im-
optimize the design of a single heat exchanger. Previously, the influence proved significantly with just a little cost of pressure drop.
of plate corrugations geometry was researched by Arsenyeva et al. In the current special issue, a new method for determining the op-
[124]. The authors developed a mathematical model of plate heat ex- timal heat-exchanger layout in a heat recovery steam generator to-
changer (PHE) using decomposition of the plate on its main corrugated gether with the operating parameters is given by Čehil et al. [131]. The
field, which causes a major effect on heat transfer, and distribution authors developed a robust mathematical model capable of arbitrary
zone, which influences mostly the hydraulic performance. The model is setting of the steam-pressure and steam-reheating levels. The method
validated on experimental data for some commercial plates. Heat considers all the possible heat-exchanger layouts, in both serial and
transfer intensification for shell and tube heat exchangers was pre- parallel arrangements of steam pressure levels or steam reheating le-
sented by Pan et al. [125], while Ma et al. [126] studied local ther- vels. The maximum thermodynamic efficiency of the steam-turbine
mal–hydraulic performance and optimization of zigzag-type printed cycle is set as the objective function. Results show that it is justified to
circuit heat exchanger at high temperatures up to 900 °C. Masiukiewicz use a parallel heat-exchanger arrangement from a thermodynamic
and Anweiler [127] described a method of two-phase flow structure viewpoint in the case of similar water or steam temperature profiles in
evaluation for minichannels of mini heat exchangers and concluded the heat exchangers of different steam pressure levels or reheating
that for each flow structure, there is a set of stereological parameters, level.
enabling the quantitative estimation of the two-phase flow. They also The results of work from [131] could also lead to better design of
found out that the interrelation of stereological parameters, during the systems as proposed in the current issue by Tańczuk et al. in [132]
change of the flow structure, can be used for controlling the operating where authors proposed the repowering of coal-fired municipal district
conditions. Wang et al. [30] presented a review of three kinds of surface heating source by a gas turbine. Furthermore optimal size of gas turbine
heat exchangers, i.e., shell-and-tube heat exchangers with helical baf- was found and it has been proven that the retrofitting coal-fired district
fles, air-cooled heat exchangers used in large air-cooled systems, and heating positively affects the feasibility of the plant operation. An al-
primary surface heat exchangers. At prior SDEWES conferences, there gorithm of techno-economical optimization of repowering and simula-
were also many papers representing the optimization of heat recovery tion of operation of different size of gas turbines was carried out. For
and HEN design for a single plant or facility as showed by Anastasovski 210 MW of peak heat demand, the optimal size of gas turbine is 5 MW.
et al. [128] for analysis of heat recovery system in a bioprocess plant. In The authors in [90] modelled heat recovery boiler with many para-
addition, Ma et al. [129] described the Cross-Wavy (CW) primary meters, however, they did not in detail modelled system processes so

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there can be additional benefits to optimize heat exchange network utilization (CCU) assisted by Solar Thermal Power. The process relies
within HRB in order to increase integration, increase efficiencies and on carbon dioxide absorption using a dry carbonate process and its
lower the system costs. conversion to sodium bicarbonate using as raw material trona. The
additional heat required in the CCU process penalizes the global system
7. Development and integration of energy storage for CSP plants efficiency by a 10.2%, which is reduced just to the electricity parasitic
consumption for solids transport and CO2 compression (∼3%) if re-
In previous research work for concentrated solar power plants, newable energy sources are integrated. From the economic point of
Ruelas et al. [133] developed and applied a new mathematical model view, the penalty in electricity consumption is fully compensated by the
for estimating the intercept factor of a Scheffler-type solar concentrator new by-product sales. Taking into account the reduction of electricity
(STSC) based on the geometric and optical behaviour of the con- sales and current prices for trona and NaHCO3, a return of investment is
centrator in Cartesian coordinates. The incorporation of a thermal obtained in the range between 3 and 8.7 years with an Internal Rate of
model of the receptor was performed using numerical examinations to Return (IRR) over 12%. These values improve the current forecast for
determine the technical feasibility of attaching the STSC to a 3 kWe any other CCS process up to date, which suggests a high interest of the
Stirling engine. The authors used numerical simulations and experi- proposed conceptual integrations for regions where trona is available.
mental data to validate the mathematical model. Another study for In the manuscript, authors provided the current state of the art tech-
better design of solar concentrators was provided by Przenzak et al. nology for sodium bicarbonate production from trona decomposition
[134]. The analysis included a high temperature heat receiver, which is together with the description of the concept of CO2 capture and sodium
part of a concentrating solar radiation helio-energetic installation. bicarbonate production for CO2 integration in a valuable chemical
Surface and spatial distribution of temperature in the heat receiver and product. The integration scheme is detailed in the application to a 15
the changes of medium temperature, among others, were presented. MWel coal power plant as a case study. The results show the high en-
The conducted research contributes to optimising the concentrating vironmental and economic benefits of the novel concept proposed.
solar radiation system and increasing the efficiency of the high-tem- In a new paper presented in the current SDEWES special issue, Ortiz
perature heat receiver. et al. [140] explored the integration of the calcium looping process
In addition, Chacartegui et al. [135] studied the integration of two based upon the reversible carbonation/calcination of calcium oxide as
heat storage layouts for small-mid size Organic Rankine Cycle Parabolic thermochemical energy storage into concentrated solar power plants.
trough solar power plants (ORC-PTSPP). Full system performance at After calcination, the stored products of the reaction (calcium oxide and
design and off design conditions was presented from thermal and eco- carbon dioxide) are brought together in a carbonator reactor whereby
nomic points of view operating with different organic working fluids. the high temperature exothermic reaction releases the stored energy for
The best results were achieved with 10 h capacity of indirect thermal efficient power production when needed. The authors proposed ad-
storage, while LCOE was reduced to 16.3c€/kW. As the solar field is the vanced analyses of several power cycle configurations with the main
most expensive part of the plant and its dimensions can have significant goal of optimising the performance of the overall system integration.
impact on the LCOE, authors analysed 8 solar fields for their application Possible integration schemes are proposed in which power production
with share of these fields in the total costs of the plant between 43% is carried out directly (using a closed carbon dioxide Brayton power
and 63%. The presented results showed the competitiveness of the cycle) or indirectly (by means of a steam reheat Rankine cycle or a
proposed integrated solutions in small size parabolic trough designs for supercritical carbon dioxide Brayton cycle). The results obtained show
off grid solutions, which can be further combined with other renewable that the highest plant efficiencies (up to 45–46%) are achievable using a
technologies. Chacartegui et al. [136] had further analysed the in- closed carbon dioxide Brayton power cycle.
tegration of a Humid Air microturbine and an ORC in a combined cycle
for distributed generation. The analysis was based on several sets of 8. Sectorial integration of bioenergy resources and biorefineries
organic fluids and recovery temperatures. The results showed that the
optimal integration was achieved using toluene and R245fa for the There have been many studies showing how to increase the energy
medium and low temperature ORC respectively. efficiency in a certain type of industry or industrial processes by using
Beside the solar field, energy storage can have a significant impact new methods or integrating new methods with existing tools and ap-
on cost and operation of solar power plants [135]. For this reason, in plying them in a new environment.
previous SDEWES conferences, there were several proposals for suitable For example, La Madrid et al. [141] in the previous special issue had
high efficient storage solutions that will combine sensible and latent presented a numerical simulation of heat transfer phenomena in the
heat storage with phase change materials (PCMs) to provide high en- open heat exchangers used in a Jaggery production. The integrated
ergy density storage. The authors in [137] discussed energy develop- approach allowed to simultaneously achieve energy savings and en-
ments and storage techniques, with special emphasis on thermal energy vironmental benefits that are not only represented by reductions in
storage and the use of PCM. They showed results obtained when en- GHG emissions. Tańczuk et al. [142] had optimized the size of a waste
capsulating NaNO3/KNO3-PCM in an AISI 321 tube, as an example of a heat recovery unit for a municipal sewage sludge drying plant supplied
storage application using a multi-tubular exchanger filled with PCM. with heat generated in CHP units fuelled with natural gas. Grosser and
More recently, another contribution to the development of thermal Neczaj [143] investigated how co-digestion of sewage sludge with other
energy storage technologies was provided by Urschitz et al. [138]. The organic waste (for example fat rich materials) can enhance the per-
authors proposed a novel bimetallic heat exchanger tube for a latent formance of anaerobic digestion. They studied the effects of adding
thermal energy storage application that can stand temperatures up to fatty rich materials on the performance and stability of semi-continuous
340 °C. Their solution can be applied in concentrated solar power plants anaerobic digestion of sewage sludge. The results of the laboratory
and other heat exchanger tubes where fins, high temperature differ- study revealed that the use of grease trap sludge as a co-substrate is an
ences and high pressures are present. Storing heat energy is important interesting method for the intensification of methane production from
not only for use in CSP plants but also for capturing and recovery of sewage sludge [143]. Matuszewska et al. [144] evaluated the biological
waste heat from industrial processes. Current CSP plants and linked methane potential of various feedstock for the production of biogas to
energy storage are technically more advanced and there are significant supply agricultural tractors. They present results of biological methane
reduction in their installation and operational costs so they are be- potential of agriculture raw materials available in Poland and devel-
coming interesting solutions for integration in industrial processes. oped a simple mathematical model of methanogenic fermentation.
In the current SDEWES special issue, Bonaventura et al. [139] Results of emission tests on the dual-fuel tractor engine that is supplied
proposed a novel technology integration for carbon capture and with biogas and diesel oil showed the higher concentrations of

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hydrocarbons and carbon oxide and lower concentrations of particulate Medina-González et al. [148] proposed a new method of designing a
matter in exhaust gases. supply chain network in process system engineering. The authors de-
In order to lower the pressure to waste and wastewater collection veloped a mathematical multi-objective optimization model, suggested
and treatment systems, it is important to minimize the amount of waste a procedure to solve it by generation of several possible solutions, and
coming from the industries or to find a new value for these wastes. In finally proposed multi-criteria decision method to select the optimal
the current SDEWES special issue, Lazaroiu at al. [145] studied energy solution. The authors argue that strategies for supply chains besides
recovery of animal waste from leather industry. The authors analysed economic, environmental and social objectives should include un-
two approaches to process the animal waste from the tanneries. The certain strategies to respond against unpredictable situations. The no-
first proposal is to use animal fats that represent around 10% of waste velty in their approach is in the evaluation of the influence of the raw
as fuel for the diesel engine and the rest of animal wastes to be used for material on the performance of the process (uncertainty in the avail-
biogas generation for heat production. The energy recovery technolo- ability and the quality of the biomass). The main part of the paper is a
gies of the animal waste, which are analysed in this paper, can be easily case study used for verification and justification of this approach based
integrated in a current production system. At the same time, through on a bio-based energy supply chain in Ghana. The authors presented
this utilization, the animal waste problem can be solved, being used for results of a previous deterministic model and identified the gap in re-
replacing the fossil fuels. The effects of animal waste usage on the search on which they proposed their stochastic model. Based on results
pollutant emissions level, exhaust gas temperature, indicated mean of the comparison, the conclusion is that a deterministic model is effi-
effective pressure, maximum pressure, and engine efficiency are ana- cient only for known parameters. Although stochastic approach derives
lysed. Results of the experimental testing showed that the animal fats worse result in the case of deterministic conditions, it could increase
can be considered as a very good alternative fuel for the diesel engines average performance for the entire uncertain space. Issues of un-
without major constructive modifications. certainty were also undertaken by Rosengart et al. [149] in the context
As shown by Lazaroiu et al. [145], some wastes such as fats can be of estimating the cost of downstream biorefineries in which the de-
used directly as fuels in different fuel mixtures while many others must veloped ultrafiltration predictive model was benchmarked with data
be pre-treated or processed to be suitable as some secondary or trans- from a biorefining pilot plant. All these approaches may help to solve
formed energy source. Biorefineries represents a new concept that en- the major barriers for a expansion of biofuels that had been identified
sures the highest sustainability if it is integrated in industries, agri- previously by Ajanovic and Haas in [150]. The barriers identified for
culture or other processes that deals with biomass conversion to Brazil, the US and EU were high costs (compared to fossil fuels),
valuable materials, fuels or energy. A novel biorefinery integration moderate ecological performances, limited feedstocks for biofuel pro-
concept for lignocellulosic biomass is presented in the current special duction and their competition with food production. To enable in-
issue by Özdenkçi et al. [146]. The authors described a novel integra- tegration of new generation of algal-based biorefinery into energy
tion concept for bio-economy aspect and a hydrothermal process for systems, it is also important to make the techno-economic assessment
biomass conversion. A detailed review on biorefinery concepts and even in the early stage of technology development [151]. In recent
conversion processes is provided at the beginning of the paper fol- work, Thomassen et al. [152] reviewed even more studies of multiple
lowing the proposal for a sectorial integration concept: utilizing the environmental and economic assessments of biorefineries for algal-
waste or side streams from all biomass sectors and targeting multi- based bioenergy products. With developed algal-based biorefinery the
product. The sectorial integration concept has the potential for sus- competition for land between the biodiesel and food commodities
tainable production from biomass: pre-treatment at the biomass sides, would become irrelevant [153].
regional distributed conversion of biomass from various sectors (e.g. Biorefineries may be composed of many processes, such as com-
black liquor, sawdust, straw) and centralized upgrading/separation of bustion, gasification, pyrolysis, hydrothermal processing, anaerobic
crude biofuels. The proposed solution represents an enhanced version digestion, fermentation, and esterification that are used to convert raw
of a distributed-centralized network. Furthermore, authors also propose materials or intermediate products into biofuels, biogases, heat, steam,
a novel hydrothermal process for biomass conversion, multi-feed-mul- electricity, hydrogen etc. Pyrolysis of lignocellulosic biomass for bio-
tiproduct and flexible process to adapt the variety in market demand fuels production has already become an important research topic
and feedstock. The conversion process composes the vital part of such a among many researchers. Biomass pyrolysis can be used to extract
concept. The new conversion involves partial wet oxidation (PWO) – or various compounds from different types of biomass. Previously,
simultaneous dissolution with PWO for solid biomass- followed by Medrano et al. in [154] proposed to use catalytic steam reforming in
lignin recovery with acidification and a reactor that can function hy- fluidized bed to produce hydrogen from aqueous fraction of biomass
drothermal liquefaction or supercritical water gasification. Finally, pyrolysis liquids. Opatokun et al. [155] assessed the energy potential of
sustainability analysis is presented regarding the integration concept food waste energy harvesting system (digestion followed by pyrolysis of
and the hydrothermal process. This manuscript presents a concept digestate). Digestate with increased calorific content was produced
which can be a potential solution for renewable energy policy. The after a commercial one stage anaerobic digestion of the raw food waste.
sectorial integration ensures the feed supply and the conversion process The authors concluded that transitional energy base products (biogas
is suitable for biomass having high moisture content. The new concept and bio-oil) are generated through the energy harvesting system of food
can contribute to social development of rural areas and reduce the waste, while energy rich solid fuels can be produced through pyrolysis
emissions in a profitable way. at 500 °C. Previously, Kim et al. [156] proposed the thermal and ex-situ
As explained by Budzianowski and Postawa [147] biorefineries are catalytic pyrolysis of different citrus peels. They studied four types of
increasingly important commercial facilities for the production of bio- peels by thermogravimetric, evolved gas analysis–mass spectrometry
fuels, biopower and various biomaterials from biomass. Furthermore, and tandem micro-reactor–gas chromatograph/mass spectrometry
biorefinery systems consist of biorefinery facilities and their entire analyses. Mesoporous MFI was found to be a more effective catalyst for
value chain. Integration of biorefinery systems aims at optimising the the production of mono aromatic compounds (benzene, toluene,
use of energies and materials in the total chain from biomass planta- ethylbenzene, and xylene; 3.06–4.17C%) and light olefins (ethene,
tions to end product utilization and is therefore capable of successfully propene, butene, and butadiene; 8.13–9.13C%) than Al-MCM-41 (mono
improving economic viability and sustainability of biorefineries [147]. aromatic compounds 0.67–0.93C% and light olefins 3.61–4.58C%) be-
Optimization of logistic of supply chains is important for sustainability. cause of its higher catalytic activity in deoxygenation and aromatiza-
As some biomass sources have large quantities of water, the supply tion due to the stronger acidity of mesoporous MFI. A similar thermo-
chains may play a crucial role for ensuring low cost input materials and gravimetric analysis was presented by Ferreiro et al. [157]. The authors
profitability of production in biorefineries. In the current special issue, provided a study with a two-step fitting procedure to estimate the

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kinetic parameters of two distinct pyrolysis models to study the pyr- basis) with other fuels at two Portuguese coal-fired power plants (Sines
olysis of pine bark, wheat straw, and rice husk. Thermogravimetric and Pego).
curves were obtained for the three biomass fuels for heating rates of 5, As shown in previous work on biomass, biorefineries, well in-
10 and 15 K/min in an inert atmosphere of Argon to investigate the tegrated logistics and optimization of biomass conversion processes
impact of the type of biomass in the pyrolysis behaviour under different could lead to more sustainable systems. Optimization of feed stock
heating conditions. biomass and sustainable supply chains are also important. However,
As discussed by Kim et al. [158] in the current special issue, al- beside properly planned logistics it is very important to have accurate
though the yield and quality of bio-oil obtained from the pyrolysis of statistics on biomass cultivation, production, and use.
biomass have been improved by innovative and intensive researches, its Implementation of a new statistics approach on final energy con-
direct use as a liquid fuel or petrochemical feedstock is still difficult sumption of biomass in household sector in three countries, namely,
owing to its low quality caused by large amounts of unstable oxygen Croatia, Bosnia and Herzegovina and Macedonia, is analysed in [162].
containing pyrolyzates and high water content. To overcome these The main aim of this paper presented by Kos Grabar Robina and Kin-
limitations of bio-oil, catalytic upgrading of bio-oil and catalytic pyr- derman Lončarević [162] is to show an improved way of collection and
olysis of biomass have been extensively studied with various kinds of compilation of data about solid biomass consumption in households in
catalysts. It has been shown that by applying the proper catalyst to the order to improve the accuracy of official energy statistics data. Accu-
pyrolysis process, the large amounts of oxygen containing compounds rate, timely and reliable energy data significantly contribute to the
in bio-oil can be converted into value-added products, such as furans consistency in national energy statistics, energy balance, as well as
and aromatic hydrocarbons. However, the low yields of aromatic hy- many other obligatory reporting procedures, which are requested and
drocarbons and short lifetime of catalysts have to be improved for the prescribed by national and international standards. When compiling
actual commercialization of the process. The short lifetime of the cat- energy statistics, statistics on renewables, particularly biomass con-
alyst during the catalytic pyrolysis of biomass is originated from the sumption, is often the most questionable as little or no available official
large amounts of coke formation. Large amounts of oxygen compounds data exists in the country. In this process, biomass consumption is often
and phenolics are the main coke precursors, which can eventually block estimated and based on the reports on fuel woodcuts and official bio-
the pore of catalysts and lead to the severe decativation of catalyst mass production, although from experience it is known that consump-
[158]. tion is much higher. Over the past two decades, Energy Institute Hrvoje
Recently, co-feeding of plastics as the hydrogen donor into the Požar (EIHP) from Croatia worked intensively on the energy con-
catalytic pyrolysis system of biomass was suggested as a good method sumption data collection and particularly on the development of the
to decrease the formation of coke. The synergistic formation of aro- tailored-made surveying methodologies for different final energy con-
matic hydrocarbons was also achieved by the catalytic co-pyrolysis of sumption sectors, particularly for the household sector. The similar
biomass with plastics. The use of plastics as the co-feeding materials (or methodology was recommended to National Statistics Institutes in the
tyers) is also a sustainable approach because large amounts of plastic- countries in the region when providing technical assistance in devel-
based polymeric products, such as polymer films, is still being land- oping energy statistics.
filled. Another method to improve the formation efficiency of aromatic
hydrocarbons is the torrefaction of biomass. It was reported that the 9. Conclusions
carbon density of biomass can be increased by the torrefaction and
torrefied biomass can produce larger amounts of aromatic hydro- This editorial is based primarily upon 35 papers selected from
carbons from the catalytic pyrolysis. among 538 contributions presented at the 2nd SEE SDEWES and 11th
Yellow poplar (YP) wood is the typical biomass occupying the lar- SDEWES Conferences. The papers cover an extensive scope of tech-
gest harvesting area in Korea and has large amount of cellulose in its nologies and concepts related to energy as well as management ap-
structure. As Kim et al. [158] argued, many researchers reported the proaches that have the potential to support future integration of energy
thermal and catalytic pyrolysis of YP but there are only a few reports on systems and prepare the ground for the development of a post carbon
the catalytic co-pyrolysis of YP and plastics. It is important to point out society.
that the application of torrefied YP as the reactant for the catalytic co- These papers also underline the need for the sustainable develop-
pyrolysis of biomass and plastics was not reported yet. The authors ment of energy, water, and environment systems in designing more
performed the catalytic co-pyrolysis of torrefied YP and high-density effective and efficient solutions.
polyethylene (HDPE) over two kinds of catalysts, microporous HZSM-5 The papers presented in the current special issue are multidisciplinary
and mesoporous Al-MCM-41. The effects of biomass torrefaction, co- and cover many aspects of sustainable development. While they have been
feeding of HDPE, and reaction type (in-situ or ex-situ) were discussed grouped into three main topics, there is constructive overlap between
together with the effect of the applied catalyst. It was concluded that them. The effective integration of renewable energy sources, including for
the torrefaction, co-feeding of HDPE, and in-situ catalytic pyrolysis can sustainable combustion, can increase efficiencies across systems. There are
provide the beneficial effects on the yield increase of aromatic hydro- 15 papers [6,8,11,13,23,28,29,33,45–51] under the topic of sustainable
carbons during the catalytic pyrolysis of biomass. Strong acidity and combustion in the current special issue. Moreover, 14 new papers
proper pore structure of catalyst were also required to provide enough [76,78,81–85,112,113,115,131,132,139,140] are grouped under the topic
reaction efficiency for the formation of aromatic hydrocarbons. on renewable energy sources and sector integration while the last 6 new
Poplar trees can be cultivated as short rotation woody crops. papers [145,146,148,149,158,162] fall under the topic on sectorial in-
Previously, Pfeifer et al. [159] analysed large areas of agricultural land tegration of bioenergy resources and biorefineries.
that remain unused for food crops and concluded that they represent The guest editors believe that the selected papers and addressed
significant potential for growing short rotation biomass that could also issues considerably extend the knowledge body published in Energy
be used as raw materials for pyrolysis in biorefineries or as fuel in CHP Conversion and Management and will be of interest to readers, parti-
plants. Similarly, Kuppens et al. [160] proposed willow trees cultivated cularly in the areas of sustainable combustion technologies, renewable
in short rotation to serve as a phytoextracting crop to be used in the fast energy sources and sector integration, the integration of renewable
pyrolysis as it has lower process temperature that prevents metal vo- technologies in the urban environment, the integration of heat, cold,
latilization. Pereira et al. [161] researched the potential of poplar short electricity and fuel production in buildings and industrial applications,
rotation coppice cultivation for bioenergy in the Alentejo region of heat exchangers and heat exchanger networks, the development and
Southern Portugal. The authors did not suggest pyrolysis as they studied integration of energy storage for concentrated solar power plants, and
cofiring technology. The biomass should be co-fired up to 10% (energy sectorial integration of bioenergy resources and biorefineries.

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The guest editors thank the authors of the papers that comprise this several high-efficiency surface heat exchangers for energy conversion and utili-
special issue for their high quality and important contributions. We also zation. Appl Energy 2014;135:748–77.
thank the many reviewers who provided valuable and highly appre- [31] Stanek W, Czarnowska L, Szczygiel I, Rojczyk M. Exergo-ecological evaluation of
heat exchanger. Therm Sci 2014;18:853–62.
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