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The industrial sector is one of the biggest oil consumers in Cyprus, corresponding to 20% of the fuel consumption. A parabolic trough collector (PTC) system seems the best option to produce clean thermal energy at higher temperatures than those that can be achieved from the already widely used flat plate collectors on the island. This paper presents a simulation model built to investigate the performance of the first industrial PTC system in Cyprus, installed at the Cyprus biggest soft drinks factory. The simulation model is built in TRNSYS and is validated using data from the real PTC system installed at the factory. The results show a very good fitting between the operating parameters and the power output of the Solar Field (SF), Concrete Thermal Storage System (CTES), and the Steam Generator (SG). The average percentage relative error of the system's contribution to the process is less than 6.32% for the daily steam production and during a week did not exceed 6.45%. The novelty of this study is the development of a design tool that can be used by potential interested industries to identify the suitable system that fits their needs. All data are provided in the form of graphs and allow anyone to use as input data the thermal energy demand and required steam temperature of the industry to retrieve information about the size of a suitable system which satisfies these requirements depending on each case. The payback period for all cases examined varies from 2 to 6 years, depending on the size of the system.

In this paper, we provide a comprehensive overview of the state-of-the-art in hybrid PV-T collectors and the wider systems within which they can be implemented, and assess the worldwide energy and carbon mitigation potential of these systems. We cover both experimental and computational studies, identify opportunities for performance enhancement, pathways for collector innovation, and implications of their wider deployment at the solar-generation system level. First, we classify and review the main types of PV-T collectors, including air-based, liquid-based, dual air–water, heat-pipe, building integrated and concentrated PV-T collectors. This is followed by a presentation of performance enhancement opportunities and pathways for collector innovation. Here, we address state-of-the-art design modifications, next-generation PV cell technologies, selective coatings, spectral splitting and nanofluids. Beyond this, we address wider PV-T systems and their applications, comprising a thorough review of solar combined heat and power (S–CHP), solar cooling, solar combined cooling, heat and power (S–CCHP), solar desalination, solar drying and solar for hydrogen production systems. This includes a specific review of potential performance and cost improvements and opportunities at the solar-generation system level in thermal energy storage, control and demand-side management. Subsequently, a set of the most promising PV-T systems is assessed to analyse their carbon mitigation potential and how this technology might fit within pathways for global decarbonization. It is estimated that the REmap baseline emission curve can be reduced by more than 16% in 2030 if the uptake of solar PV-T technologies can be promoted. Finally, the review turns to a critical examination of key challenges for the adoption of PV-T technology and recommendations.

The challenge of integration of large scale RES to islands seems infeasible when the islands have isolated energy systems without primary fuel sources, with limited sources of RES and without energy storage systems. Cyprus island is one of these cases, which covers 93% of the energy demand using imported fossil fuels. Building sector is the second biggest energy consumer accounting for 19% of the final energy consumption. A net-metering scheme is introduced recently to promote the installation of small PV systems in buildings. This paper therefore takes the approach of analyzing various scenarios for installation of PV roof systems in existing and future households of Cyprus island until 2050. The goal is to achieve 100% renewable energy production to cover the needs of the households sector. Results show that the electricity demand of the domestic sector can be 100% covered when over 70% of the existing residential stock install 3 kW roof PV system. Even if 50% of the existing residential stock install a 3 kW PV system the required capacity from other applications (eg. PV parks) to make domestic sector 100% renewable is 191 MW, which is feasible. To ensure a smooth transition to 100% renewable energy in all sectors, significant actions should be taken for the development of renewable energy systems, sector coupling, smart grid system planning and storage technologies. The present study examines only the potential of the further use of net-metering scheme in the domestic sector and discusses the barriers to full energy transition as well.

In recent years many Renewable Energy Sources (RES) power plants have been connected to power networks throughout Europe, in order to meet the EU's objectives for sustainable energy supply. As far as RES residential applications are concerned, the grid-connected photovoltaic (PV) systems constitute the most important representative of RES, because PVs can be easily installed even in densely built-up areas. In this context, small residential PV systems utilising Building Integrated PV (BIPV) modules are going to gain ground mainly at newly built or rebuilt building structures. That is because a BIPV module operates as a multi-functional building construction material; it generates energy and serves as part of the building envelope. This paper highlights the energy benefits of residential buildings in Southern Europe with Fibre Reinforced Composite BIPV modules under Net Metering Scheme and proposes suitable grid-connected PV inverter structures in case of BIPV systems with multiple orientation and inclination profiles.

The efficiency of Building Integrated Photovoltaic/Thermal (BIPV/T) systems depends on various parameters such as the location, amount of incident radiation, orientation of the collector surface, slope of the system and the type of ventilation of the air gap between the Photovoltaic (PV) panels and the secondary skin of the building. However, in order to examine the performance of the system, apart from the energy efficiency, the exergy efficiency needs to be estimated as well. There are numerous studies about energy and exergy efficiency of PV systems, however, most of them are based on PV/T systems, water systems and mechanically ventilated air systems. This paper examines theoretically and experimentally the energy and exergy analysis of a naturally ventilated BIPV/T system. Experimental procedure is carried out to record the temperature distribution of a naturally ventilated BIPV/T system. The results from the experimental procedure are used to estimate the energy efficiency and exergy efficiency of the system. It is proved that the energy efficiency of the system varies from a minimum of 26.5% to a maximum of 33.5%, and the exergy efficiency varies from a minimum 13% to a maximum of 16%. It is also observed that the exergy input to the system is much higher than the exergy output of the system.

As part of the transnational research project EDITOR, a parabolic trough collector system (PTC) with concrete thermal energy storage (C-TES) was installed and commissioned in Limassol, Cyprus. The system is located on the premises of the beverage manufacturer KEAN Soft Drinks Ltd. and its function is to supply process steam for the factory's pasteurisation process [1]. Depending on the factory's seasonally varying capacity for beverage production, the solar system delivers between 5 and 25 % of the total steam demand. In combination with the C-TES, the solar plant can supply process steam on demand before sunrise or after sunset. Furthermore, the C-TES compensates the PTC during the day in fluctuating weather conditions. The parabolic trough collector as well as the control and oil handling unit is designed and manufactured by Protarget AG, Germany. The C-TES is designed and produced by CADE Soluciones de Ingenieria, S.L., Spain. In the focus of this paper is the description of the operational experience with the PTC, C-TES and boiler during the commissioning and operation phase. Additionally, innovative optimisation measures are presented.

Thermal processes account for 70% of the EU industry final energy, with 30% thereof being wasted through losses. This fact has been a motivating factor toward applying various technologies and methods for waste heat recovery. Already such technologies exist and are applied in many industrial sectors, while some “new” technologies have also been tested or suggested. It is therefore useful to obtain insight information into such processes, together with their temperature ranges and, hence, assess the potential market for each industrial sector. Here such an attempt is made, based on existing literature. Estimates on the total energy that can be recovered through the EU industry are given and a special case study on the important Iron and Steel industry is presented. This kind of information can be useful for the improvement of existing and the development of “new” technologies or techniques.

Cyprus covers 93% of the energy demand using fossil fuels which are fully covered from imports. This does not only stand as a barrier to the various European Directives and measures which apply for all EU members, but it is also a drawback for the economy of Cyprus. Around 1000 tons of heavy fuel oil is required every year by the Electricity Authority of Cyprus to cover the energy demand. The household electricity prices including taxes paid in Cyprus are the 7th highest in Europe. From 2009, renewable energy systems have started to be used, but due to the price of the systems they were limited. However, price was not the main problem of the systems to explain why they didn’t expand more. Many other parameters are still affecting the use of RES in Cyprus; the public acceptance, the education of people, the environmental consciousness, but the most important is the motivation and ease of the applications and licensing from the government parties. Here in this study, an overview of the current energy situation is discussed and suggestions to increase the use of RES are mentioned as well. These include the use of electricity production RES for the domestic needs and measures for the improvement of energy efficiency of the building sector in general, which is the second biggest energy consumer in Cyprus after the commercial sector.

Industrial processes are currently responsible for almost 26% of European primary energy consumptions (275 Mtoe/yr). Furthermore, most of the energy sources that drive the industrial sector are fossil fuel based. Every industrial process is characterised by a multitude of waste heat streams at different temperature levels whose recovery would undoubtedly contribute to the enhancement of the sustainability of the industrial sites and their products. Waste heat recovery systems can offer significant energy savings and substantial greenhouse gas emission reductions. For the latter to materialise technological improvements and innovations aimed at improving the energy efficiency of heat recovery equipment and reducing installation costs should take place. This paper outlines the opportunities and the potential for industrial heat recovery in the European Union by identifying and quantifying primary energy consumption in the major industrial sectors and their related waste streams and temperature levels. Through a systematic analysis considering waste heat and Carnot’s potential estimation, detailed results are given for all industrial sectors, temperature ranges and EU countries. The ‘big picture’ is rather promising with regards to the estimated total waste heat potential. The research presented in this paper has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 680599. Aspects of the work are also funded by the Centre for Sustainable Energy Use in Food Chains (CSEF). CSEF is an End Use Energy Demand Centre funded by the Research Councils UK, Grant No: EP/K011820/1.

In the European Union (EU), industrial sectors use 26% of the primary energy consumption and are characterized by large amounts of energy losses in the form of waste heat at different temperature levels. Their recovery is a challenge but also an opportunity for science and business. In this study, after a brief description of the conventional Waste Heat Recovery (WHR) approaches, the novel technologies under development within the I-ThERM Horizon 2020 project are presented and assessed from an energy and market perspectives. These technologies are: heat to power conversion systems based on bottoming thermodynamic cycles (Trilateral Flash Cycle for low grade waste heat and Joule-Brayton cycle working with supercritical carbon dioxide for high temperature waste heat sources); heat recovery devices based on heat pipes (flat heat pipe for high grade radiative heat sources and condensing economizer for acidic effluents). European Union’s Horizon 2020 research and innovation programme, the Centre for Sustainable Energy Use in Food Chains (CSEF) and the Engineering and Physical Sciences Research Council (EPSRC) funded project ‘Optimising Energy Management in Industry-OPTEMIN’

In this paper the design and the energy performance investigation of a new flat-plate solar thermal air collector prototype is presented. The adoption of cost-effective materials and simple design solutions represent the main novelties of the proposed device when compared to existing commercial collectors. In addition, the prototype is suitably designed to be integrated into the building envelope (facade), which is a key feature for the market uptake of building integrated solar thermal systems. The paper includes the description of the dynamic simulation model, developed for the energy and economic performance analyses of the whole building-prototype system. The simulation model, implemented with a computer code written in MatLab, is able to predict both active (hot air production for building space heating) and passive (winter free heating and summer overheating) effects due to the building integration of the proposed solar collector. By such tool, indoor comfort investigations can also be carried out. The dynamic simulation models of both the building and the collector prototype were successfully validated. In order to show the features of the developed simulation code, a suitable case study was carried out. It refers to an office space, part of a high-rise multi-use building, simulated as located in three different weather zones (Freiburg, Naples and Almeria). The examined solar collector is modelled as vertically integrated into the building facade, and three different orientations (East, South-East and South) were taken into account. Interesting results for the energetic, economic and occupants comfort points of view are obtained. By taking into account an initial cost of the system of about 5 k€, the primary energy savings achieved by the proposed system against the traditional buildings range between 1.9 and 8.0 MWh/y (depending on the selected weather zone and backup system). The shortest payback for all the investigated weather zones is obtained for Naples, which is equal to 6.2 years.

This paper presents a new TRNSYS Type (called Type 99) which can be used for the energy assessment of thermosiphon Flat-Plate solar thermal Collectors (FPCs) for water heating. The accuracy of this new type is higher than the standard type (Type 45a) available in TRNSYS library, since the density and specific heat of water are estimated according to the operating fluid temperature. The results of a suitable experimental campaign are also presented for different commercial FPCs system layouts. The developed Type 99 is successfully validated, proven by the very good agreement achieved between the simulation and experimental results. By the new Type 99 a suitable Design of Experiment (DoE) analysis is carried out with the aim to assess the design and operating parameters mostly affecting the energy and economic performance of two types of FPCs. Specifically, collector pipe diameters, slope, storage tank volume, and thermal insulation thickness are investigated. The analysis is carried out for three case studies which refer to residential Domestic Hot Water (DHW) production applications and to three different European weather zones (Freiburg, Naples and Larnaca). For these case studies an optimization procedure is also carried out by varying the same design and operating parameters for two different objective functions: best energy behaviour [maximum Primary Energy Saving (PES)] and best economic performance [minimum Simple Pay Back (SPB)]. Interesting novel design criteria and encouraging economic results are obtained.

The authors regret to realise a typing mistake on page 3, line 9. The number of 280 kWth should be 280 kWhth. Additionally, there is a problem in Fig. 5. The correct figure and the correct legend of the figure are as shown below: [Figure presented] Fig. 5. (a) Steam generator (b) feed water tanks (c) variable speed pump (d) control valves. The authors would like to apologise for any inconvenience caused. Manufacturing is responsible for 60% of the fuel consumption in Cyprus and the industrial sector is the second biggest fuel consumer, mainly for steam production. Thus, the use of parabolic trough collector (PTC) systems for the production of steam or hot water can be a promising solution for the industrial sector. This study presents the first industrial PTC system in Cyprus, installed at the biggest soft drinks factory. The system consists of 288 m2 of PTC, a steam generator and concrete thermal energy storage (CTES) in order to keep the system dispatchable. To achieve that, two operation strategies are developed which are controlled automatically by the main processor of the system. The first strategy is enabled when there is a steam demand and the second when the energy can be stored directly to the CTES. Both strategies are tested, and it is shown that under Strategy 1 the PTC system can produce 940 litters of steam per day, and under Strategy 2 it can store 107.3 kWhth. In two months period tests, it is proved that it can supply the required amount of steam to the factory even when solar radiation is low, with the support from the CTES.

This article presents the state of the knowledge on the thermal analysis of double skin facades with integrated photovoltaic (PV) panels called the Building Integrated Photovoltaics (BIPV) in terms of the published studies carried out on these systems. The idea of integration of the PV panels by replacing building elements, increase the prospects of the renewable energy systems. Taking also into account the need to use more renewable energy systems in buildings, the investigation of the BIPV systems to improve their performance is of a great importance. The literature studies are separated into experimental and theoretical for naturally ventilated systems and mechanically ventilated with external means e.g. fan use. It is concluded that most researchers studied the systems with mechanical ventilation rather than the systems with natural ventilation because the latter are more complex in terms of the air flow behaviour in the air duct. Additionally, various researchers proposed Nu number correlations and convective heat transfer correlation under several assumptions and conditions every time, for different range or Ra number which are presented and compared in this paper.

Many countries apply measures for the limitation of the conventional energy technologies and try to expand the use of renewables. As the building sector accounts for almost 40% of the energy consumption in Europe, building integrated photovoltaic (BIPV) systems gain peoples’ interest lately concerning the replacement of the conventional construction materials of the buildings envelope with photovoltaic (PV) panels which can serve at the same time as construction material and energy producer. The aim of this study is to present an overview of the available published research on the BIPV systems and identify the barriers and risks associated with the application of BIPV and discuss the future perspectives and solutions through recommendations for future research and development. The most important barriers of the BIPV systems are the feed in tariff implementation, the public acceptance, the governmental economic support in terms of subsidies and technical aspects like the power losses and the architectural considerations. The future perspectives of the BIPV systems proposed are based on the barriers discussed. It is stated that new solutions in the PV industry are many and various and there is room for improvement regarding design, configuration, ventilation, positioning, guidelines, monitoring and performance prediction. In total, more than 100 articles have been identified and analysed since 2000. Many of these articles have a predominant focus on the investigation of the performance of the system, and the ventilation of the PV panels in BIPV applications for electricity production, due to the negative role of the temperature on PVs electrical efficiency, and the heat transfer behavior of the system. This paper shows that although research in the adoption of BIPV systems in terms of their performance and optimization is fairly new, it has gained attention in the last decades. However, their practical applications have been slow in comparison with the conventional rack-mounted PV panels.

The purpose of this two-part study is to present the experimental analysis carried out on a naturally ventilated Building Integrated Photovoltaic (BIPV) system and the new correlations developed for the estimation of the convective heat transfer coefficients (CHTC) in the air gap, and use the developed correlations to construct a simulation model which is validated with the experimental data. In BIPV systems the air gap is responsible to cool the PVs and remove excess heat to avoid building overheating. The ventilation of the air gap can be natural or mechanical. However, naturally ventilated systems are less studied although they have important advantages over the mechanically ventilated ones, such as the avoidance of extra energy of the fans, maintenance and noise. The present Part I of this study presents an experimental based thermal analysis of a naturally ventilated vertical BIPV system. A series of experiments on a custom made BIPV system were carried in real outdoor conditions as well as indoors with the use of a large scale solar simulator to measure the thermal characteristics of the system and its thermal behaviour. Indoor experiments were performed to avoid external disturbances from wind that may occur outside. The results show that an open-ended air gap of 0.1 m can create adequate air flow on naturally ventilated systems and can ensure low PV temperatures to avoid PV efficiency decrease. The experimental data are then used to estimate the convective heat transfer coefficients to fit the real conditions of the BIPV systems. Then two correlations are proposed for the estimation of the Nusselt number that fits best the thermal characteristics of a naturally ventilated BIPV system.

This is the second part of a two-part study based on the thermal behaviour of a naturally ventilated BIPV systems. In the first part an experimental analysis of the thermal behaviour of a naturally ventilated BIPV system is presented and two new correlations for the estimation of the convective heat transfer coefficients in the air gap between the PV panel and a second skin are given, for windy and non-windy conditions. The present study (second part) presents a simulation based thermal analysis of a naturally ventilated vertical BIPV system. The simulation model is created using the developed equations for the estimation of the convective heat transfer coefficients presented in the first part of the present study, and the model is validated with the use of experimental data shown in the first part as well. The experimental based correlations are imported in the mathematical model, in order to be able to investigate the effect of other parameters on the thermal behaviour of the system such as the height of the system, the size of the air gap and the air velocity in the duct. These parameters are not easy to be investigated experimentally and their investigation would be very time consuming. The simulation model has a good agreement with the experimental results. The results shown that an air gap of 0.1 m can create adequate air flow on naturally ventilated systems and can ensure low PV temperatures to avoid efficiency decrease. This can be done when the air gap has bottom and top openings to allow air circulation. In taller systems, the temperatures are higher and there is a drop of the efficiency of the system.

A Building Integrated Photovoltaic (BIPV) facade is formed by PV panels integrated to a second skin forming an air gap between the two skins. The air gap is responsible for cooling the PVs and for removing the excess heat, to avoid building overheating. The ventilation of the air gap can be natural or mechanical. The system investigated in this study is a vertical, naturally ventilated system. This has a number of advantages, the most important being the avoidance of energy to power the fans, the operation with no noise and the avoidance of overheating which can happen when the fan stops in an active system. A BIPV system is designed in COMSOL simulations software in 3D geometry and tested by varying the temperature on the various surfaces of the system for different air velocities from 0.02 m/s to 2.5 m/s. Additionally, experimental tests are carried out to validate the model. The results show a good agreement between the simulated and measured values.

This paper presents a study of the characteristics of three types of PV panels: monocrystalline, polycrystalline and amorphous silicon and the effects of soiling on their performance using on-site measurements. The total system consists of the three types of panels in pairs. Initially, the characterization of the PV panels is carried out to prove the similarity of the two pairs. Another test performed is the degradation of PV's performance under extreme soiling conditions caused by the artificial deposition of dust on the panels when their surface was dry and when it was wet before the dust deposition. The results showed that especially the artificial soiling on the wet PV surface presents a serious degradation of the PV performance. Finally, the effect of natural dust deposition on the panel's surfaces for a year is investigated. During this period a total of three dust episodes were recorded. These dust episodes concern the transfer of dust from the Sahara desert and these episodes usually end with a light rain which sticks the dust on exposed surfaces including PVs. Due to the exceptionally wet weather that we had during the testing period all episodes were followed by heavy rain, but even in this case a serious degradation of the performance of about 13% of the affected PV panels was recorded. The first finding of this study is that in winter the occasional rain is adequate to keep the PV surfaces clean whereas when a dust episode occurs, the panels should be cleaned manually. This is not the case for the summer time, which for Cyprus lasts for more than 8 months. The recommended cleaning is immediately after a dust episode and every 2–3 weeks in summer time according to how much loss the owner of the PV is willing to accept and the associated cleaning cost.