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Solar heating and cooling (SHC) systems are currently attracting attention, especially in times of increasing energy prices and supply crises. In times of lower energy prices, absorption SHC systems were not competitive to compression cooling supported by photovoltaic (PV) modules due to the high investment costs and total energy efficiency. This paper aims to discuss the current changes in energy supply and energy prices in terms of the feasibility of the application of a small absorption SHC system in a mild Mediterranean climate. The existing hospital complex restaurant SHC system with evacuated tube solar collectors and a small single-stage absorption chiller was used as a reference system for extended analysis. Dynamic simulation models based on solar thermal collectors, PV modules, absorption chillers and air-to-water heat pumps were developed for reliable research and system comparison. The results showed that primary energy consumption in SHC systems designed to cover base energy load strongly depends on the additional energy source, e.g., boiler or heat pump. Absorption SHC systems can be price competitive to air-to-water heat pump (AWHP) systems with PV collectors only in the case of reduced investment costs and increased electricity price. To reach acceptable economic viability of the absorption SHC system, investment price should be at least equal to or lower than a comparable AWHP system. [ABSTRACT FROM AUTHOR]

This study presents a novel cavity receiver for parabolic trough concentrators, incorporating a triangular envelope, a trapezoidal cavity, and a semi-circular flow channel. A total of 5120 designs were examined by tuning the rim angle of parabolic mirrors, the width and angle of the receiver's opening, and the depth of the absorber for different operating flow rates and temperatures. Batch simulations of these designs were automated by coupling newly developed and validated models of Monte Carlo ray tracing and semi-analytical 1-D energy balances in SOLTRACE® and MATLAB® to determine the heat fluxes and surface temperatures of the receiver, respectively. The results show that the rim angle must be reduced to maximize sun rays' interception, and the opening angle has the largest impact on performance. All dimensions must be decreased when operating at low flow rates and high temperatures to avoid excessive thermal losses. This results in maximum energy and exergy efficiencies of 74.7 % and 40.7 %, respectively. When operating at low temperatures and large flow rates, the largest energy and exergy efficiencies increase and decrease to 80.5 % and 27 %, corresponding to optimal rim angle, absorber depth, opening width, and opening angle of 60°, 85 mm, 200 mm, and 100°, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

In the context of the global energy transition, governments design and apply renewable energy policies as tools to replace fossil fuel sources for the heating end-use sector, which represents half of the global total final energy consumption (TFEC). In the last two decades, large deployments of solar thermal technologies, such as solar water heaters (SWH), have helped renewable energy penetrate the heating sector. To be successful, their adoption must be supported by effective policies; however, measuring the effectiveness of a particular policy is a complex task. Some studies design and propose indicators to measure this effectiveness but are difficult to replicate or adapt to specific markets. This work submits a novel policy-outcome effectiveness indicator, the Solar Water Heater Effectiveness Indicator (SWHEI), based on equipment deployment (installed capacity per capita, installed capacity growth) and the solar energy potential of each country, constructed using publicly available data to ensure replicability and universal utilization. The overall SHWEI values for the period 2003-2019 are low, reflecting the current low adoption of solar technologies, but show regional clusters of good performance, such as in Europe. Barbados achieved the maximum value of 6.9, which reflects its outstanding performance, driven by its installed capacity per capita. The analysis shows that the SWHEI is particularly useful to determine policy ineffectiveness while confounding factors could camouflage policy effectiveness. The SWHEI-active SWH policies matrix can help policymakers identify courses of action. Policymakers could 1) use market-entry policy instruments in undeveloped SWH markets (segment C, no policies in place); 2) review and improve failing SWH policies (segment D); 3) propose randomized controlled trials to study causal relationships between SWH policies and large SWHEI (segments A and B with policies in place); and 4) regulate successful markets, allowing for continued organic growth (segment A, no policies). [ABSTRACT FROM AUTHOR]

Solar heating and cooling (SHC) systems are currently attracting attention, especially in times of increasing energy prices and supply crises. In times of lower energy prices, absorption SHC systems were not competitive to compression cooling supported by photovoltaic (PV) modules due to the high investment costs and total energy efficiency. This paper aims to discuss the current changes in energy supply and energy prices in terms of the feasibility of the application of a small absorption SHC system in a mild Mediterranean climate. The existing hospital complex restaurant SHC system with evacuated tube solar collectors and a small single-stage absorption chiller was used as a reference system for extended analysis. Dynamic simulation models based on solar thermal collectors, PV modules, absorption chillers and air-to-water heat pumps were developed for reliable research and system comparison. The results showed that primary energy consumption in SHC systems designed to cover base energy load strongly depends on the additional energy source, e.g., boiler or heat pump. Absorption SHC systems can be price competitive to air-to-water heat pump (AWHP) systems with PV collectors only in the case of reduced investment costs and increased electricity price. To reach acceptable economic viability of the absorption SHC system, investment price should be at least equal to or lower than a comparable AWHP system.

Solar heating and cooling (SHC) systems can be relevant in the achievement of energy and climate European goals. The benefits of these technologies should be evaluated taking into account their life-cycle energy and environmental impacts, calculated by applying the Life Cycle Assessment (LCA). The development of a complete LCA can be difficult and time-consuming particularly for non-experts in LCA, discouraging them in developing the life-cycle assessments. To overcome this issue, the paper presents "ELISA - Environmental Lifecycle Impacts of Solar Air-conditioning systems", a user-friendly simplified tool for estimating the life-cycle energy and environmental benefits/impacts of solar technologies for heating and cooling in different geographic contexts and comparing them to conventional systems. The tool was applied to analyse three systems (thermal SHC, conventional and PV assisted system) in Greece and to identify the one characterized by the best life-cycle performances. The results revealed that the impacts of PV assisted system are about 60% lower than those of the others, highlighting the advantage of using renewable electricity for building air-conditioning in locations with high solar radiation availability. ELISA can be used by researchers, designers and decision-makers to introduce the life-cycle thinking in the early design phase of heating and cooling systems. • ELISA is a tool for developing a simplified LCA of solar heating and cooling technologies. • ELISA calculates the impacts of heating and cooling systems in a specific geographic context. • Three systems installed in Athens (Greece) are examined by combining ELISA with a simulation tool. • The PV assisted system is the best one in terms of life-cycle energy and environmental performance. [ABSTRACT FROM AUTHOR]

This paper presents a case study experimental validation of PISTACHE which is a new presizing tool intended for designers and planners. It facilitates pre-design and allows the evaluation of annual performance and the integration potential of solar heating, cooling and domestic hot water closed systems. This new tool has been performed in order to standardize the sizing methodology and the comparison of the SHC&DHW closed systems. The comparison framework used in PISTACHE has been performed using seasonal performance indicators that were issued and gathered from experimental data provided by several operating plants. Thus, PISTACHE is an easy graphical user interface and free downloadable tool. In order to check the reliability of the new developed tool, two configuration modes are investigated in this experimental study: a simple cooling mode (RAFSOL plant) and a double cooling and heating mode (SONNENKRAFT installation). The whole validation process is performed using the GenOpt optimization program to determine the optimum set of internal parameters for PISTACHE tool.

In this paper, an integrated system aiming for heating and cooling production using solar energy is investigated. The system consisting of a solar driven adsorption chiller and radiation heating coupled with thermal energy storage is analysed thermodynamically, and its overall performance is assessed through energy and exergy efficiencies. The main goal is to compare performances of the system equipped with different thermal energy storage tank. Two thermal storage tank arrangements - a water TES and PCM TES - are discussed. These cases are later compared with the reference system without a storage tank. The results of the energy and exergy analyses of the reference case without thermal storage show that the seasonal energy and exergy efficiencies are 24.2% and 10.5%. Furthermore, by introducing thermal storage, energy and exergy performances of the system have improved significantly compared to the reference case. The annual energy and exergy efficiencies of the integrated system with water TES were 31.9% and 14.3%, respectively. Moreover, it was observed that the annual energy and exergy efficiencies of the system with PCM TES are slightly higher than for the system with water TES (1.5 and 0.7% points, respectively) for the same storage capacity. • System consisting of a solar driven adsorption chiller and radiation heating coupled with storage tank is investigated. • Energy and exergy analysis were performed on system and component level. • Annual energy and exergy analyses of the reference case without thermal storage were 24.2% and 10.5%. • Improvement of the performance by introducing the thermal storage. • Annual efficiencies of the phase change material storage tank are higher than for the sensible water tank system. [ABSTRACT FROM AUTHOR]

Highlights • Transient model was built to analyze unsteady thermal behaviors of PTCs. • It was validated with experiment data measured from a utility-scale loop of PTCs. • Parametric studies were made to analyze essential impact factors. Abstract Solar resources are inherently unsteady and their energy density on the earth is low. Thereby, when the solar energy is converted into thermal energy through concentrating the sunlight, how to predict the transient performance of parabolic trough solar collectors under the operating conditions is necessary for the steady useful output and the efficient use of the energy. So this paper describes a mathematical model of the transient thermal behaviors of parabolic trough solar collectors. Then, to validate this transient model, its numerical results are compared with the experimental data. These data were collected from a utility-scale loop of parabolic trough solar collectors. The comparison between the model predictions and the experimental data shows a consistent and reasonable agreement. Furthermore, the primary interest of this study is to determine how the temperature distributions of the absorber, the glass envelope and the heat transfer fluid evolve from initial conditions with specified optical and thermal parameters. Thus, this model is used to carry out parametric studies to make analyses of essential impact factors on transient behaviors of parabolic trough solar collectors. These factors include the temperature of the heat transfer fluid at the inlet, the initial conditions, and the optical efficiency. Moreover, this model has the function of continuous adjustment of the flow rate to satisfy the requirement of the temperature of the heat transfer fluid at the outlet according to varying boundary conditions. Hence, another analysis is performed to investigate transient processes when the flow rate is continuously adjusted at various DNI ramp rates. [ABSTRACT FROM AUTHOR]

Energy needs of air conditioning systems are constantly growing worldwide, due to climate change and growing standards of buildings. Among the possible systems, solar heating and cooling based on reversible heat pumps and thermally driven chillers are a viable option for ensuring space heating and cooling for different users. The high installation costs are a limit to their diffusion, however, under specific circumstances (climate, type of the building, type of the user, etc.), the investment in this technology can be profitable in a long term. The presented paper describes an energy-economic assessment of a solar heating and cooling system integrating a solar dish concentrator with thermal collectors coupled with a reversible heat pump and an absorption or adsorption chiller. The system integrated with a household building is developed and dynamically simulated in the Transient System Simulation (TRNSYS) environment under different circumstances –adoption of absorption or adsorption chiller, use of auxiliary thermal energy to drive the sorption chillers, and locality. The results show that space cooling demand in Cracow is matched by solar energy, in a range between 49.0 and 97.6%, while for Naples the space cooling demand is provided by solar heat from 46.1 to 99.1% depending on the adopted sorption chiller and or the use of auxiliary heat for a natural gas boiler. The proposed system is not profitable in case Cracow, since a Simple Pay Back period of about 20 years is achieved. Conversely, case of Naples, the same index achieves a value between 8 and 12 years showing that the proposed system may be a viable solution for heating and cooling installation.

During the last years, special attention has been paid to renewable polygeneration technologies, able of simultaneously producing thermal, cooling, electrical energy and desalinated water from seawater. This paper focuses on an innovative polygeneration system driven by renewable energy sources, including the following technologies: hybrid photovoltaic/thermal collectors, concentrating parabolic trough (CPVT), a biomass heater, a single-stage absorption chiller and a multiple-effect distillation desalination system. The system is designed to cover the base load of an isolated small community. In previous papers, the dynamic simulation model about plant operation is discussed. In this paper, a detailed exergy, economic and environmental analysis of the plant is presented. In addition, the plant was optimized using different objective functions, applying the Design of Experiment (DoE) methodology which evaluates the sensitivity of the different objective functions with respect to the selected design parameters. The results show that an increase of the storage volume is generally negative, whereas increasing the solar field area involves an increase of the exergy destruction rate, but also an improvement of the CPVT exergy output provided; the final result is an increase of both the exergy efficiency and the economic profitability of the polygeneration system.

Highlights • Operational frequency deduced both analytically and computationally. • Previously untested cooling configuration found to be the optimal. • Development of validated computer model of physical system. • Liquid piston instability linked to Rayleigh-Taylor phenomenon. • Liquid piston maximum acceleration limit identified. Abstract The objective of this research project is to develop a solar-powered refrigerator in the lower capacity range of up to 5 kW of cooling power. With the use of liquid pistons and one of the most efficient thermodynamic cycles known, the Stirling cycle, this product has the potential to outperform rival solar cooling technologies while providing inexpensive, reliable, quiet, environmentally-friendly, and efficient solar cooling for residential use, due to its straightforward manufacturing, simple design and inert working gas. Presented in this paper are the newest results of the theoretical and experimental investigation into deducing the key design parameters and system configuration of the so-called Liquid Piston Stirling Cooler (LPSC), which will help lead to optimal performance. Computer models of the complex unconstrained system have been constructed and validated using the modelling software Sage and shown to replicate system behavior with reasonable accuracy in experiments. The models have been used to predict system improvements and identify limitations imposed by the use of liquid pistons. The results to date provide a unique insight into a relatively little studied area in Stirling cycle research. [ABSTRACT FROM AUTHOR]

Solar heating and cooling systems for space heating and cooling are experiencing a growing trend and interest. However, the actual energy and environmental performance of small/medium size installations is not clearly foreseeable. In this paper, an analysis of such systems using adsorption chillers in different European climates is presented. Solar systems have been simulated in TRNSYS and compared to a conventional system employing a vapour compression unit. The results have been used for a Life Cycle Assessment (LCA) study, determining the potential impact during the whole life of the system, from raw materials supply to its end-of-life. The LCA has been carried out by using the LCA tool developed in the framework of the International Energy Agency SHC Task 48. Results showed that the useful life of the system is a key parameter: for a useful life of 10 years, the conventional system performs better than the renewable-based one for almost all the locations. However, if a longer life is achieved (15 or 20 years), solar systems show environmental advantage under almost all the climatic conditions: the environmental benefits of using a solar system during the operation step counterbalance the additional impact generated during the other life-cycle steps. [ABSTRACT FROM AUTHOR]

The energy demand for the air-conditioning of buildings has shown a very significant growth trend in the last two decades. In this paper three alternative hygroscopic materials for desiccant wheels are compared considering the operation of the air handling unit they are installed in. The analyses are performed by means of the TRNSYS 17® software, simulating the plant with the desiccant wheel made of: silica-gel, i.e., the filling actually used in the experimental plant desiccant wheel of the University of Sannio Laboratory; MIL101@GO-6 (MILGO), a composite material, consisting of graphite oxide dispersed in a MIL101 metal organic framework structure; Campanian Ignimbrite, a naturally occurring tuff, rich in phillipsite and chabazite zeolites, widespread in the Campania region, in Southern Italy. The air-conditioning system analyzed serves a university classroom located in Benevento, and it is activated by the thermal energy of a solar field for which three surfaces are considered: about 20, 27 and 34 m2. The results demonstrate that a primary energy saving of about 20%, 29%, 15% can be reached with silica-gel, MILGO and zeolite-rich tuff desiccant wheel based air handling units, respectively.

Solar energy can play a leading role in reducing the current reliance on fossil fuels and in increasing renewable energy integration in the built environment, and its affordable deployment is widely recognised as an important global engineering grand challenge. Of particular interest are solar energy systems based on hybrid photovoltaic-thermal (PV-T) collectors, which can reach overall efficiencies of 70% or higher, with electrical efficiencies up to 15–20% and thermal efficiencies in excess of 50%, depending on the conditions. In most applications, the electrical output of a hybrid PV-T system is the priority, hence the contacting fluid is used to cool the PV cells and to maximise their electrical performance, which imposes a limit on the fluid’s downstream use. When optimising the overall output of PV-T systems for combined heating and/or cooling provision, this solution can cover more than 60% of the heating and about 50% of the cooling demands of households in the urban environment. To achieve this, PV-T systems can be coupled to heat pumps, or absorption refrigeration systems as viable alternatives to vapour-compression systems. This work considers the techno-economic challenges of such systems, when aiming at a low cost per kW h of combined energy generation (co- or tri-generation) in the housing sector. First, the technical viability and affordability of the proposed systems are studied in ten European locations, with local weather profiles, using annually and monthly averaged solar-irradiance and energy-demand data relating to homes with a total floor area of 100 m 2 (4–5 persons) and a rooftop area of 50 m 2 . Based on annual simulations, Seville, Rome, Madrid and Bucharest emerge as the most promising locations from those examined, and the most efficient system configuration involves coupling PV-T panels to water-to-water heat pumps that use the PV-T thermal output to maximise the system’s COP. Hourly resolved transient models are then defined in TRNSYS, including thermal energy storage, in order to provide detailed estimates of system performance, since it is found that the temporal resolution (e.g. hourly, daily, yearly) of the simulations strongly affects their predicted performance. The TRNSYS results indicate that PV-T systems have the potential to cover 60% of the combined (space and hot water) heating and almost 100% of the cooling demands of homes (annually integrated) at all four aforementioned locations. Finally, when accounting for all useful energy outputs from the PV-T systems, the overall levelised cost of energy of these systems is found to be in the range of 0.06–0.12 €/kW h, which is 30–40% lower than that of equivalent PV-only systems. [ABSTRACT FROM AUTHOR]

The amount of energy for air conditioning in the summer time in Mediterranean Area is very high because of hot weather and high temperature values. Solar cooling technology is interesting because strong sunlight covers the cooling requirement. The heat energy from the sun it is available when the demand of electricity has high peaks for the strong use for air conditioning devices. In this work, an analysis by means of NEGST software (New Generation of Solar Thermal System) on a solar cooling and heating system located in the southern part of Italy has been carried out. The building is a Quality Assurance Office of a chemical industry. It is 48 m long, 23 m wide and 3.5 m high, and about 200 people work inside. Thermal loads from people, PC, machines etc. have been estimated by means of Energy Plus code. Three different type of collectors (FPC, ETC and PTC) and two different chillers have been considered: single effect for collectors FPC and ETC and double effect (H2O-BrLi) for the collectors PTC. Results in terms of solar fraction and PE-Saving for three different configurations are shown. Besides, the payback period for the best configuration is estimated. [ABSTRACT FROM AUTHOR]

Life Cycle Assessment (LCA) is an effective methodology to assess the energy and environmental impacts of energy systems during their life cycle, including manufacturing, operation and end-of-life. The aim of the paper is the application of a simplified LCA tool, developed in the framework of the International Energy Agency Solar Heating and Cooling Task 48, for comparing different typologies of solar assisted heating and cooling systems. In detail, solar thermal heating and cooling systems located in Palermo (southern Italy) and in Zurich (Switzerland) were compared with conventional systems assisted by grid connected and stand-alone photovoltaic plants. A validation of the tool was also carried out by comparing the obtained results with those of in-depth LCA studies. The results showed that the best system configuration in Palermo is the conventional system assisted by a grid-connected photovoltaic plant. Its impact on global energy requirement is about 83.7% and 74.5% of the corresponding impact of the solar thermal heating and cooling and the conventional system assisted by a stand-alone photovoltaic system, respectively. Different considerations can be made for Zurich, where the solar heating and cooling system performs better than the others; it is characterized by a global energy requirement that is 85.3% and 81.2% of the grid-connected and stand-alone photovoltaic assisted conventional systems, respectively. A similar trend is traceable for the global warming potential indicator. The validation of the LCA tool proved it to be reliable since deviations with a detailed LCA of the same system are contained below a 5% difference in all the comparable systems. [ABSTRACT FROM AUTHOR]

In this paper a new simulation model of a novel solar heating and cooling system based on innovative high temperature flat plate evacuated solar thermal collector is presented. The system configuration includes: flat-plate evacuated solar collectors, a double-stage LiBr-H2O absorption chiller, gas-fired auxiliary heater, a closed loop cooling tower, pumps, heat exchangers, storage tanks, valves, mixers and controllers. The novelty of this study lies in the utilization of flat-plate stationary solar collectors, manufactured by TVP Solar, rather than concentrating ones (typically adopted for driving double-stage absorption chillers). Such devices show ultra-high thermal efficiencies, even at very high (about 200 °C) operating temperatures, thanks to the high vacuum insulation. Aim of the paper is to analyse the energy and economic feasibility of such novel technology, by including it in a prototypal solar heating and cooling system. For this purpose, the solar heating and cooling system design and performance were analysed by means of a purposely developed dynamic simulation model, implemented in TRNSYS. A suitable case study is also presented. Here, the simulated plant is conceived for the space heating and cooling and the domestic hot water production of a small building, whose energy needs are fulfilled through a real installation (settled also for experimental purposes) built up close to Naples (South Italy). Simulation results show that the investigated system is able to reach high thermal efficiencies and very good energy performance. Finally, the economic analysis shows results comparable to those achieved through similar renewable energy systems. [ABSTRACT FROM AUTHOR]

The present work investigates the feasibility of solar heating and cooling (SHC) absorption systems based on combining three types of LiBr–H 2 O absorption chillers (single-, double-, and triple-effect) with common solar thermal collectors available on the market. A single-effect chiller is coupled with evacuated tube collectors (ETCs) – SHC1. A double-effect chiller is integrated with parabolic trough collectors (PTCs), linear Fresnel micro-concentrating collectors (MCTs) and evacuated flat plate collectors (EFPCs) respectively – SHC2, SHC3, and SHC4. PTCs are employed to provide high-temperature heat to a triple-effect absorption chiller (SHC5). Although triple-effect chillers have been around for a while, this paper represents the first system-level analysis of these chillers coupled with high-temperature solar concentrating collectors for air-conditioning applications. A simulation model for each configuration is developed in a transient system simulation environment (TRNSYS 17). Furthermore, a unique, comprehensive perspective is given by investigating the impact of characteristic solar beam radiation to global radiation ratios on the techno-economic performance of the proposed SHC plants for a wide variety of climatic regions worldwide. The results of parametric study suggest that a storage volume of around 70 L/m 2 is a good choice for SHC1, while 40–50 L/m 2 storage capacity is sufficient for the other configurations (SHC2 to SHC5). The simulation results reveal that when the fraction of direct normal irradiance (DNI) is less than 50%, SHC2, SHC3, and SHC5 require larger collector area compared to SHC1, showing there is no advantage in using concentrating collector powered multi-effect chillers over solar single-effect chillers in climates with low DNI level. However, in climates with DNI fractions above 60%, the smallest solar field is achieved by SHC5, followed by SHC2. SHC4, which benefits from both relatively high COP of double-effect chiller and the diffuse component in the solar field, results in the most reasonable trade-off between energetic and economic performance of the system in a wide range of climatic conditions. [ABSTRACT FROM AUTHOR]

A great interest has recently arisen for the sustainable supply of energy and fresh water, due to the growing demand from developing countries. Facing this demand by traditional technologies implies evident risks related with the high cost of fossil fuels and their environmental impact. Then, alternative solutions based on the use of renewable sources and innovative technologies must be considered. In this paper a renewable polygeneration system is examined, which includes a solar field based on parabolic trough photovoltaic/thermal collectors, a biomass heater, an absorption chiller and a Multiple Effect Distillation desalination unit. Plant operation under dynamic conditions has been analysed in previous papers; in this paper an exergetic and exergoeconomic analysis is carried out. The exergetic analysis is intended to identify the steps that mostly affect the overall plant exergy efficiency, so as to propose possible improvements. The exergoeconomic cost accounting is aimed at assigning a monetary value to each energy or material flow, thus providing a rational basis for price assignment. Both the exergetic and exergoeconomic analyses are applied to integral values of energy flows, comparing the results obtained in the summer and winter season. Finally, economic viability of the system in different context scenarios is discussed. [ABSTRACT FROM AUTHOR]

A solar-heating-and-cooling (SHC) system, consisting of a flat-plate solar collector array, a hot water storage tank, and an absorption chiller unit is designed and modeled to satisfy thermal loads (space heating, domestic hot water, and space cooling). The system is applied for Nicosia, Cyprus, a location with prolonged summer-like conditions, where heating demand is moderate, while space cooling demand is comparatively very high. The study investigates the potential of a solar system installed and operated onsite in a detached single-family household to satisfy all necessary thermal loads. The hot water storage tank is also connected to an auxiliary heater (diesel-fired boiler) to supplement solar heating, when needed. The main purpose of the study is to model the overall system and contact a parametric study that will determine the optimum economic system performance in terms of design parameters. The system is compared, through a cost analysis, to an electric heat pump (EHP) system. It is found that the optimum system combination of solar collector area and volumetric capacity of the hot water storage tank is 70 m 2 and 2000 L, respectively. The total annualized cost (in USD) for the optimum SHC system is $3,719. The sensitivity analysis showed that the SHC system would be unfavorable to compete with EHP technology, if the solar collector cost is above $360/m 2 . [ABSTRACT FROM AUTHOR]

During the last years, special attention has been paid to renewable polygeneration technologies, able of simultaneously producing thermal, cooling, electrical energy and desalinated water from seawater. This paper focuses on an innovative polygeneration system driven by renewable energy sources, including the following technologies: hybrid photovoltaic/thermal collectors, concentrating parabolic trough (CPVT), a biomass heater, a single-stage absorption chiller and a multiple-effect distillation desalination system. The system is designed to cover the base load of an isolated small community. In previous papers, the dynamic simulation model about plant operation is discussed. In this paper, a detailed exergy, economic and environmental analysis of the plant is presented. In addition, the plant was optimized using different objective functions, applying the Design of Experiment (DoE) methodology which evaluates the sensitivity of the different objective functions with respect to the selected design parameters. The results show that an increase of the storage volume is generally negative, whereas increasing the solar field area involves an increase of the exergy destruction rate, but also an improvement of the CPVT exergy output provided; the final result is an increase of both the exergy efficiency and the economic profitability of the polygeneration system. [ABSTRACT FROM AUTHOR]

Within the finished Singular Strategic Project about Bioclimatic Architecture and Solar Cooling (SSP-ARFRISOL), five buildings were built or restored – Research and Development Buildings – using bioclimatic architectural designs and solar based HVAC and DHW systems. This article is about the overall operation of the HVAC and DHW system installed in the building number 70 of CIEMAT in Madrid. It consists of a solar collector field, linked with absorption machines to obtain cold water, “Solar Cooling”, as well as the support of conventional means. The system and its operation are described, and then an eleven-month period of operation, under real use conditions, is analyzed from an energetic point of view. The methodology described in this article allows detecting energy sinks and abnormal operations, where the critical points are, and eases to make corrections. We also include an example of optimization using this methodology applied to this system and, after the changes were made in the configuration and the operation, a further energy analysis for the next four months. [ABSTRACT FROM AUTHOR]

This paper investigates the integration of solar and geothermal energy in a novel polygeneration system producing simultaneously: electricity, thermal energy, cooling energy and fresh water. The polygeneration system under analysis includes concentrating photovoltaic/thermal solar collectors (CPVT), a Geothermal Well (GW) a multi-effect distillation (MED) system for seawater desalination, a single-stage LiBr–H 2 O absorption chiller and additional components, such as: storage tanks, heat exchangers and balance of plant devices. The CPVT produces simultaneously electrical energy and thermal energy, at a maximum temperature of about 100 °C. The electrical energy is delivered to the grid, whereas the thermal energy can be used for different scopes. First, the thermal energy can be used for heating purposes and/or Domestic Hot Water production. As an alternative, solar thermal energy can be used to drive an absorption chiller, producing chilled water for space cooling. Finally, solar energy, in combination with the thermal energy produced by low-enthalpy (about 80 °C) geothermal wells, may be used by the MED system to convert seawater into desalinated water. Geothermal energy is also used to produce Domestic Hot Water at 45 °C. The system is dynamically simulated by means of a zero-dimensional transient simulation model. The simulation model also includes detailed control strategies, for the management of the different technologies included in such a complex system. The system is assumed to be operated in some of the several small volcanic islands in the Mediterranean Sea, assuming Pantelleria (Trapani, Italy) as main case study. Here, the availability of solar and geothermal energy is high whereas the availability of fresh water is scarce and its cost consequently high. Results show an excellent energetic performance of the system under investigation. From the economic point of view, the profitability of the system dramatically increases when user Domestic Hot Water demand is high. [ABSTRACT FROM AUTHOR]

Abstract: A field of transparent solar thermal façade collectors (TSTC) was installed in a pilot building in Ljubljana, Slovenia. This paper presents the first measurement results from the installation. During the heating season, the transparent façade collectors contribute to the heating of the pilot building, while they provide heat to an adsorption chiller during the cooling season. Despite the different loads and surrounding conditions, the monthly solar gains of both seasons are similar. The heat flux between the collector and the interior as well as the temperatures seem comparable to a conventional solar control façade. [Copyright &y& Elsevier]

Abstract: A solar collector field of 250 m2 is being set up for cooling and adding to the heating of a building of 4000 m2 with mixed use, which includes offices, laboratories, computing and electronics facilities, and a public area. Novel solar thermal collectors will be used, which reach excellent performances, thanks to vacuum-insulation and innovative assembly techniques. This allows the efficient operation of an absorption cooling unit. The thermal concept combines the warm and cold streams and gives priority to solar energy. [Copyright &y& Elsevier]

Abstract: This paper analyzes different control strategies for the thermal storage management in Solar Heating and Cooling systems (SHC) for different Italian climates. This novel thermal storage system consists in a variable volume storage tank system, which includes three separate tanks and a number of mixers and diverters. Such devices are managed through two different control strategies, based on combinations of series/parallel charging and discharging approaches. Thus, it is possible to vary the thermal storage capacity as a function of the combinations of solar radiation availability and user thermal/cooling energy demands. The system allows one to either increase or reduce the number of active tanks when the occurring mismatch between the solar energy supply and the user demand is either high or low, respectively. In addition, the surplus of solar energy is used through a heat exchanger included in the solar loop for the production of Domestic Hot Water (DHW). This novel variable-volume storage system, in all the proposed configurations, is also compared with a constant-volume storage system from the energetic and economic points of view. In addition, in order to determine the set of the synthesis/design variables which maximize the system profitability, a parametric analysis is implemented. A case study developed for an office building located in different Italian climatic areas is also presented. Simulation results show that the analyzed SHC systems system configurations may be profitable for all those cases and weather locations in which a sufficiently high solar fraction is achieved. [Copyright &y& Elsevier]

Abstract: The paper is focused on the dynamic simulation of a Photovoltaic/Thermal collector (PVT) integrated in a high-temperature Solar Heating and Cooling (SHC) system. The system is based on the following main components: concentrating parabolic PVT (photovoltaic thermal) collectors, a double-stage LiBr-H2O absorption chiller, storage tanks, auxiliary heaters, balance of plant devices. The PVT is made-up by a parabolic dish concentrator and a triple-junction receiver. The polygeneration system provides electricity, space heating and cooling and domestic hot water for a given building, whose simulation is also included in the model. In particular, PVT produces electric energy, which is in part consumed by the building loads (lights and equipments), in part by the system parasitic loads, whereas the eventual excess is sold to the public grid. Simultaneously, the PVT provides the heat required to drive the absorption chiller. The system was simulated by means of a zero-dimensional transient model, that allows the evaluation of temperature profiles and also heat/electrical energy flows for whatever period of the year. It is also possible to evaluate the overall energetic and economic performance on whatever time basis (day, week, month, year, etc.). The economic results show that the system under investigation can be profitable, if a proper funding policy is available. The paper also includes an extensive parametric analysis aiming at evaluating the set of design and operating parameters (solar field area, tank volumes, set point temperatures, etc.) that maximize the energetic and/or economic performance of the system. [Copyright &y& Elsevier]

New facades of high-rise buildings often include renewable energy converters to allow “green building” operation. At the same time, numerous tenants value visual transparency. Transparent solar thermal collectors (TSTCs) aim at decreasing the non-renewable primary energy demand and increasing the visual transparency at the same time. On the one hand, this paper presents the main modelling challenges that arise when considering building facades and especially integrated TSTC systems. New transient systems simulation (TRNSYS) [Beckman, W. A., L. Broman, A. Fiksel, S. A. Klein, E. Lindberg, M. Schuler, and J. Thornton. 1994. “TRNSYS The Most Complete Solar Energy System Modelling and Simulation Software.”Renewable Energy5 (1–4): 486–488] types have been especially developed for this purpose. A simplified model is presented for comparison purposes. On the other hand, the overall performance for a building with facade-integrated TSTC, as measured by its non-renewable primary energy demand, is treated. This is achieved by considering a complete simulation model coupling the TSTC, building and heating, ventilation and air conditioning operation. Possibilities for primary energy savings are investigated using the building mass as additional thermal storage. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a novel purposely designed dynamic simulation model for the performance analysis of solar heating and cooling systems is presented. The investigated system layouts are based on single stage LiBr–H2O absorption chillers and on both evacuated tube and concentrating photovoltaic thermal solar collectors. Furthermore, both electric chiller and gas fired heater backup system are considered. Such model is implemented in a computer code written in MATLAB. Here, the optimisation of several system design and operating parameters in terms of energy saving is also carried out. A code to code analysis is performed comparing the obtained simulation results vs. those achieved by a TRNSYS model available in literature. The simulation code for the concentrating photovoltaic thermal solar collectors is validated by experimental data. A good agreement among results is observed in both the cases. A suitable case study referred to a building including both offices and dwellings located in Northern and Southern Italy is presented. High primary energy savings are obtained for some of the investigated system layouts. By evacuated tube collectors solar field such savings can reach 74%, while shifting to concentrating photovoltaic thermal solar collectors they often surpass 100%. The system economic profitability strongly depends on future scale economies and eventual public funding. [Copyright &y& Elsevier]

Abstract: This paper presents a solar field configuration to supply thermal energy to the heating and air conditioning system of a hotel located in Almería (Southern Spain). The solar collector technology selected for the solar field is parabolic trough collector (PTC) technology, in particular a small sized PTC prototype especially designed for industrial process heat and air-conditioning systems. Each PTC collector is 8m long and its aperture length is 1m. The heat transfer fluid in the solar field is pressurized hot water. Considering the space available for the solar collector field just close to the hotel and its thermal energy demand profile, the solar field configuration proposed consists of 8 parallel rows, north-south oriented, composed of 32 PTCs connected in series. With this solar field configuration, 25% of the cooling demand is covered the hottest day of the summer and 76% of the heating demand is covered the coldest day of the winter. [Copyright &y& Elsevier]

Abstract: In this paper, a Solar Heating and Cooling (SHC) system including photovoltaic/thermal (PVT) collectors is considered, implementing a novel polygeneration system producing electricity, space heating and cooling and domestic hot water. In particular, PVT collectors operating up to 80°C are considered. A case study for a university building located in Naples (Italy) is developed and discussed. The system is mainly composed by: PVT collectors, a single-stage LiBr–H2O absorption chiller, storage tanks and auxiliary heaters. The system also includes additional balance-of-plant devices: heat exchangers, pumps, controllers, cooling tower, etc. The PVT produces electricity which is utilized in part by the building lights and equipments and in part by the system parasitic loads; the rest is eventually sold to the grid. Simultaneously, the PVT system provides the heat required to drive the absorption chiller. The system performance is analyzed from both energetic and economic points of view by means of a zero-dimensional transient simulation model, developed with TRNSYS. The economic results show that the system under investigation can be profitable, provided that an appropriate funding policy is available. In addition, the overall energetic and economic results are comparable to those reported in literature for similar systems. [Copyright &y& Elsevier]

Abstract: In this paper the integration of vegetable oil-fed reciprocating engines with solar thermal collector is investigated, seeking to design a novel polygeneration system producing: electricity, space heating and cooling and domestic hot water, for a university building located in Naples (Italy), assumed as case study. The polygeneration system is based on the following main components: concentrating parabolic trough solar collector, double-stage LiBr–H2O absorption chiller and a reciprocating engine fed by vegetable oil. The engine operates at full load producing electrical energy which is in part consumed by the building lights and equipments, in part used by the system passive loads and the rest is eventually sold to the grid. In fact, the engine is grid connected in order to perform a convenient net metering. The system was designed and then simulated by means of a zero-dimensional transient simulation model, developed using the TRNSYS software. The simulation tool developed by the authors allows one to analyze the results for different time basis (minutes, days, weeks, months and years), from both energetic and economic points of view. The economic results show that the system under investigation is profitable, especially if properly funded. [Copyright &y& Elsevier]

Abstract: There is a feasible case study of constructing some buildings free from fossil fuel in Iran. The proposed guideline is replacing of solar energy with different types of energies in a building such as electrical energy for lightening and cooling, energy obtained out of combustion of fuels for heating of building and so on. Regarding the high rate of energy consumption in our country for supplying of required cases of residential buildings, if it is possible to supply this type of energy from among limitless energy sources such as solar energy it is possible to have a considerable economy in fossil fuels. Some of the results of this research are parallel improvement of solar energy with economic development of Iran through real economy in costs and providing new job opportunities. Finally it is resulted that with regard to high rate of primary costs, there will be no more request for benefiting from solar energy, provided that we consider suitable subsidies for applying the solar equipment. [Copyright &y& Elsevier]

Abstract: In the paper, the optimal thermoeconomic configuration of Solar Heating and Cooling systems (SHC) is investigated. In particular, a case study is presented, referred to an office building located in Naples (south Italy); for such building, three different SHC configurations were analyzed: the first one is based on the coupling of evacuated solar collectors with a single-stage LiBr–H2O absorption chiller equipped with a water-to-water electrical heat pump, to be used in case of insufficient solar radiation; in the second case, a similar layout is considered, but the capacities of the absorption chiller and the solar field are smaller, since they are requested to balance just a fraction of the total cooling load of the building selected for the case study; finally, in the third case, the electric heat pump is replaced by an auxiliary gas-fired heater. A zero-dimensional transient simulation model, developed in TRNSYS, was used to analyze each layout from both thermodynamic and economic points of view. In particular, a cost model was developed in order to assess the owning and operating costs for each plant layout. Furthermore, a mixed heuristic–deterministic optimization algorithm was implemented in order to determine the set of the synthesis/design variables able to maximize the overall thermo-economic performance of the systems under analysis. For this purpose, two different objective functions were selected: the Pay-Back Period and the overall annual cost. Possible public funding, in terms of Capital Cost Contributions and/or feed-in tariff, were also considered. The results are presented on monthly and weekly basis, paying special attention to the energy and monetary flows in the optimal configurations. In particular, the thermoeconomic analysis and optimization showed that a good funding policy for the promotion of such technologies should combine a feed-in tariff with a slight Capital Cost Contribution, allowing to achieve satisfactory Pay-Back Periods. [Copyright &y& Elsevier]

Abstract: Hybrid photovoltaic–thermal (PV/T) collectors consist of a thermal collector in which a photovoltaic laminate is attached as a thermal absorber. In addition to their improved electrical efficiency, due to the decrease of the photovoltaic temperature, PV/T collectors have also thermal efficiency, which is the main issue of this research. The theoretical study of a photovoltaic–thermal system for domestic heating and cooling has led to the result that the system can cover a remarkable percentage of the domestic heating and cooling demands. Furthermore, the performance of the PV/T collector with respect to the variation of geographical region as well as to different total surface areas of the system was also investigated. According to the results in both cases, the variation of the above-mentioned parameters has notably affected the solar coverage percentage of the system. As a conclusion it could be claimed that the photovoltaic–thermal technology offers a remarkable solution to the problem of domestic heating and cooling, hence contributing to the reduction of energy consumption in houses. [Copyright &y& Elsevier]

Energy needs of air conditioning systems are constantly growing worldwide, due to climate change and growing standards of buildings. Among the possible systems, solar heating and cooling based on reversible heat pumps and thermally driven chillers are a viable option for ensuring space heating and cooling for different users. The high installation costs are a limit to their diffusion, however, under specific circumstances (climate, type of the building, type of the user, etc.), the investment in this technology can be profitable in a long term. The presented paper describes an energy-economic assessment of a solar heating and cooling system integrating a solar dish concentrator with thermal collectors coupled with a reversible heat pump and an absorption or adsorption chiller. The system integrated with a household building is developed and dynamically simulated in the Transient System Simulation (TRNSYS) environment under different circumstances –adoption of absorption or adsorption chiller, use of auxiliary thermal energy to drive the sorption chillers, and locality. The results show that space cooling demand in Cracow is matched by solar energy, in a range between 49.0 and 97.6%, while for Naples the space cooling demand is provided by solar heat from 46.1 to 99.1% depending on the adopted sorption chiller and or the use of auxiliary heat for a natural gas boiler. The proposed system is not profitable in case Cracow, since a Simple Pay Back period of about 20 years is achieved. Conversely, case of Naples, the same index achieves a value between 8 and 12 years showing that the proposed system may be a viable solution for heating and cooling installation. [ABSTRACT FROM AUTHOR]

Multi-energy system is currently under rapid development due to their potential to reduce the use of fossil fuel resources and improve system stability. A systematic simulation-based, multi-objective optimization model of for solar hybrid heat pump heating and cooling system is presented. A combined energy, economic and environmental analysis of the system is conducted to calculate the primary energy use as well as the levelized total annual cost. A multi-objective optimization model is formulated using a genetic algorithm to simultaneously minimize these objective. Linear programming technique for multidimensional analysis of preference (LINMAP) is used to select the optimal point from the Pareto front. A sensitivity analysis is also performed to assess the influence of fuel cost, capital cost of innovative components and the annual interest rate on the Pareto front of the optimal solution. • Systematic simulation and MOO model for solar hybrid heat pump system are presented. • Genetic algorithm is used for the model to minimize energy and economic objectives. • Sensitivity analysis of the influence of parameters on the Pareto front is made. [ABSTRACT FROM AUTHOR]