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A solar cooling and heating plant with a 1000 l hot water storage tank has been operated since 2018. Two main problems were observed: (1) a fluctuating operation of the absorption chiller due to a high number of stat-up and shut-down procedures; (2) high electricity consumption caused by a low solar fraction SFn of 50.9% during the cooling period. In 2021, the solar plant was retrofitted by employing a shell and tube heat exchanger based on a PCM melting at 64 °C and by adjusting the control strategy. The system performance was evaluated and compared before and after retrofitting based on the operational data in 2021 and 2022. The total number of switch-on times of the chiller shrank by 33.5% and the operation time was increased by 65% in 2022 due to the stable hot water inlet temperature. Contributing to the high heat storage capacity of the PCM storage, more solar thermal energy was utilized and the average SF n reached 75.6% during the cooling period in 2022, leading to a 24.4% reduction in the total electricity consumption compared to 2021. • A fluctuating operation of the absorption chiller was observed before retrofitting due to a higher number of stat-up and shut-down procedures. • A high electricity consumption was caused by a low solar fraction SF n of 50.9% during the cooling period before retrofitting. • After retrofitting, the total number of switch-on times of the chiller shrank by 33.5% and the operation time was increased by 65% due to the stable hot water inlet temperature. • Contributing to the high heat storage capacity of the PCM storage, the average SF n reached 75.6% during the cooling period in 2022, leading to a 24.4% reduction in the total electricity consumption compared to 2021. [ABSTRACT FROM AUTHOR]

• Advanced LCOS method to compare electricity and thermal energy storage. • Parametric storage sizing to analyse self-sufficiency and LCOS. • Evaluation of an office, a hotel and a warehouse scenario in Singapore. • Thermal energy storage offers lower LCOS, but achieves low self-sufficiency. • Battery storage needs to be well-sized. In this paper, we propose an advanced Levelised Cost of Storage (LCOS) model to compare electricity and thermal energy storage for cooling applications. The proposed model is applied to evaluate the LCOS for Lithium-Ion (Li-Ion) battery, chilled water and ice storage for Photovoltaic (PV) powered cooling for an office, a hotel, and a refrigerated warehouse scenario in Singapore. Parametric energy simulations varying the storage size were carried out to analyse the optimal storage size for different applications and technologies. The thermal energy storages were found to cause a lower chiller plant Coefficient of Performance (COP), which leads to an increased energy consumption. As a result, the battery can achieve a better performance in terms of self-sufficiency. The LCOS for the thermal energy storages are generally lower than that of the battery, at 23–47 USD ct / kWh el for all the analysed storage sizes. However, a well-sized battery can only achieve LCOS of 55 USD ct / kWh el for the office scenario, 71 USD ct / kWh el for the hotel scenario, and 55 USD ct / kWh el for the refrigerated warehouse, due to high investment cost. This work also highlights that thermal energy storage has a better potential for applications that require a larger shift of energy, such as in the investigated hotel and refrigerated warehouse scenario. [ABSTRACT FROM AUTHOR]

Thermal energy storage has been shown to improve the efficiency of solar absorption cooling systems by capturing excess insolation during peak to meet cooling demand in low insolation periods. While water is the most commonly used thermal storage medium in solar cooling applications, the small operating temperature range of solar cooling systems limits its energy density. In contrast, Phase Change Materials maintain a high energy density under limited temperature ranges, and are ideally suited for such applications. Methods to select and size appropriate thermal storage technologies in solar cooling applications vary between studies with no standard methodology being utilized across the literature. Moreover, there is limited quantification of the influence of thermal storage on system performance to motivate the additional capital investment in these systems. This study provides an analytical framework to quantify the benefit of the thermal energy storage. Predictions from the analytical model are compared to the results from a validated transient system simulation. The paper gives an engineering approach for predicting the expected benefit from both water and phase change materials based thermal storage for applications with limited temperature ranges. [ABSTRACT FROM AUTHOR]

The energy situation in tropical insular regions, as is found in French Polynesia, presents a number of challenges, including heavy dependence on imported fuel, high transport costs from the mainland and weak electricity grids. By contrast, these regions possess a variety of renewable energy resources, which are favorable for the exploitation of smart micro grids and energy storage technologies. With regards to electrical energy demand, the high temperatures commonly seen in these regions throughout the entire year implies that a large proportion of electricity consumption (∼40%) is used for space cooling, even during evening hours. Framed within this context, this paper presents an air conditioning system driven by photovoltaic electricity that combines a mechanical vapor refrigeration system and a thermochemical storage unit. Thermochemical processes enable the storage of energy in the form of chemical potential with virtually no losses, which can be used to produce cold during the evening hours without running a compressor. These processes are implemented using thermochemical reactors, in which a reversible chemical reaction between a solid compound and a gas takes place. The solid/gas pair used in this study is barium chloride salt (BaCl 2 ) reacting with ammonia (NH 3 ), which is also the coolant fluid in the refrigeration circuit. In the proposed system, the photovoltaic-driven electric compressor is used during the day either to run the refrigeration circuit when a cooling demand occurs or to decompose the ammonia-charged salt and to remove the gas from the thermochemical reactor when there is no cooling requirement. During the evening, when there is no electricity from solar sources, the system changes its configuration and the reactor reabsorbs the ammonia gas from the evaporator to produce cold. The efficiency of this hybrid system is evaluated in this work and compared with alternative processes which utilize either electrochemical (lead-acid, lithium-ion batteries) or thermal storage (ice, chilled water) for cold production. [ABSTRACT FROM AUTHOR]

The paper presents the realization and experimental characterization of a lab-scale latent heat storage, specifically developed for solar cooling applications. The latent heat storage is based on a compact fin-and-tube stainless steel heat exchanger (HEX) and a commercial paraffin blend, having a nominal melting temperature of 82 °C, suitable for solar cooling plants employing non-concentrating solar collectors technology. The realised heat storage has been experimentally characterised in lab, by means of a test rig able to simulate the working boundary conditions of a solar cooling plant. Charging and discharging tests have been performed both simulating a completed charge phase followed by a complete discharge phase, to analyse system efficiency and achievable energy storage density. Furthermore, dynamic tests, simulating short consecutive charge/discharge phases (with incomplete phase change), have been accomplished, to analyse the heat transfer efficiency inside the reactor. Main results confirmed that the heat storage density increases of about 50%, compared to sensible water storages. Satisfactory discharge efficiency, ranging between 45% and 60% has been obtained under analysed working conditions. Average discharging power between 0.7 and 1.2 kW has been measured, which confirms the necessity to further optimize the HEX efficiency as well as the thermal conductivity of the employed PCM. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) plays an important role in ensuring continuous heat supply to solar powered thermal systems such as solar cooling plants. Various sensible and latent heat storage material options are available when designing a solar cooling system. Latent heat materials are known to have higher energy density resulting in lower storage volume. However, it is unclear if there are any energy benefits due to these materials while used in a typical solar cooling application. In this paper we investigate the system performance of different storage materials while delivering cooling to a typical commercial building in Australia. This system uses high efficiency triple effect absorption chiller as the cooling delivery system. Heat requirement for this chiller is provided through parabolic trough collectors delivering heat over 200 °C. A suitable approach for storage system design that enables direct comparison of sensible and latent heat storage benefits is described in this paper. In order to simulate the latent heat storage system, a new numerical model has been developed, validated with experimental data and implemented in the simulation environment as an external library. Commercially available liquid sensible storage materials have been compared against latent heat materials with a phase change temperatures suitable for triple effect chiller operation. A parametric analysis of the system design parameters such as the collector area, storage volume has been carried out. Results from annual simulations have been presented for fixed cooling load and variable cooling load scenarios. Latent heat storage systems functioned with high storage efficiency compared to sensible heat storage systems, a reflection of low heat losses due to reduced storage sizes. It is seen that the collectors have higher yield while functioning with a sensible heat storage medium. As a result, for the chosen configuration, the sensible heat storage materials provided higher annual performance than the latent heat material choices. [ABSTRACT FROM AUTHOR]

Small scale (solar-) thermally driven cooling systems suffer from two important drawbacks: firstly, the systems usually offer no means of adapting the chilling capacity to the actual load; secondly constantly running pumps and fans lead to high auxiliary electricity consumption even when the available driving and cooling water temperatures only allow a reduced chilling capacity. To solve these problems a generic approach for controlling the main parasitic electrical devices – the cooling water pump and the heat rejection fan - as a function of the actual boundary conditions was developed. Different variants of control strategies are analyzed in different system configurations under a variety of climates and load conditions by means of dynamic system simulations in TRNSYS. The most typical combinations of ab- and adsorption chillers with dry cooler and wet cooling tower are covered. The results show that capacity modulation can be realized well by this approach. Additionally electricity savings of up to 25% can be achieved for reasonably sized systems compared to a reference control strategy with fixed pump speed and fixed cooling water set temperature. Yet it becomes obvious that the concrete savings depend strongly on the system configuration and boundary conditions. [ABSTRACT FROM AUTHOR]

Performance of an adsorption cooling system driven by solar thermal energy was studied under different climatic conditions. The effects of solar collector area, collector slope, hot water temperature and flow rate on the system performance were investigated using the real-time weather data of two cities: Perth, Australia (a representative city in the southern hemisphere) and Amman, Jordan (a representative city in the northern hemisphere). The simulation results showed that the two cities had similar solar radiation during the summer period and that the solar adsorption chiller could reliably provide cooling at a reasonably high system COP. For residential cooling with a total CPC (Compound Parabolic Collector) solar collector area of 36.22 m 2 , the average system COP was 0.491 for Perth weather conditions and 0.467 for Amman weather conditions, respectively while the cooling capacity was 10.3 kW for Perth and 8.46 kW for Amman, respectively at peak times. Optimum performance occurred when the system run with the CPC collector slope of around 30°, the solar water storage tank volume of 1.4 m 3 , inlet hot water temperature of 80 °C, and a hot water flow rate of 0.33 kg/s. An economic analysis was further investigated and the results showed that the solar driven adsorption cooling system could reduce the electricity consumption for Perth and Amman cities by 34% and 28%, respectively in comparison to a conventional vapour compression cooling system. [ABSTRACT FROM AUTHOR]

Solar driven air conditioning systems can cope with solar collectors working in a wide range of temperatures. Sorption systems, including absorption and adsorption refrigeration systems, are among the best choices for solar cooling. Five systems including modular silica gel–water adsorption chiller, single/double effect LiBr–water absorption chiller, 1. n effect LiBr–water absorption chiller, CaCl 2 /AC (activated carbon)–ammonia adsorption refrigerator, and the water–ammonia absorption ice maker with better internal heat recovery were presented. The above five sorption chillers/refrigerators work under various driven temperatures and fulfill different refrigeration demands. The thermodynamic design and system development of the systems were shown. All these systems have improvements in comparison with existing systems and may offer good options for high efficient solar cooling in the near future. [ABSTRACT FROM AUTHOR]

We designed, built and experimentally assessed the cooling power and the coefficient of performance (COP) of a chemisorption chiller that used a consolidated composite made of NaBr impregnated in expanded graphite as sorbent and ammonia as refrigerant. The influence of the operation conditions on the COP and the cooling power was calculated through the values of inlet and outlet water temperature and water mass flow across the chiller’s heat exchangers. From the experimental results, we concluded that the utilization of mass recovery simultaneously to heat recovery improved the COP and cooling power up to 11.7% and 15.4%, respectively, when compared to the values obtained when only heat recovery was employed. Regarding the influence of the heat source temperature, maximum cooling power and COP were obtained when that temperature was, respectively, 75 °C and 65 °C. As for the influence of the cycle time, the highest values of COP were obtained with an 88 min cycle, whereas the highest values of cooling power were obtained at different cycle time, depending on the value of other operation conditions. When the chiller was driven by hot water at 70 °C, and the inlet water temperature in the evaporator was not kept constant, it cooled water from 23 °C to 10 °C in 90 min with mean cooling power of 1400 W and COP 0.33. [ABSTRACT FROM AUTHOR]

Combining renewable energy with building energy supply is an effective way to pivot the building sector to carbon–neutral. This paper proposes a novel solar-assisted energy supply system which is applied in residential buildings for heating, cooling and domestic hot water. The heating/cooling output of the proposed system is mainly contributed by a vapor compression system to address the supply–demand mismatch of solar energy supply system, and the other part is assumed by a solar driven absorption system that is operating with lower generation temperature and higher evaporation temperature to assist the vapor compression system. Therefore, a solar-assisted absorption-compression system (SAACS) exploits the full potential of solar heat for annual energy supply by improving the contribution of per unit solar collection area, with considerable electricity-saving compared to air-source heat pumps. A thermodynamic model is established and validated by the results of the built experimental prototype which is testing. Solar-assisted heating mode and solar-assisted cooling mode are compared in comprehensive evaluation criteria to illustrate the performance differences caused by the assisted solar energy. The results indicate that solar heat at 60 °C is feasible for heating and cooling, revealing the great potential for efficient conversion from solar energy for heating and cooling. Due to the introduction of solar energy, the cooling and heating COP ele increases by 10.3 % ∼ 17.6 % and 32.3 % ∼ 56.3 %, respectively. Despite the lower increase in COP ele , electricity-saving ratio shows greater value at low hot water temperatures, varying from 24.3 % to 19.6 % for cooling and from 44.1 % to 39.7 % for heating as hot water temperature increases from 60 °C to 85 °C. The maximum SCOP is 0.63 for cooling, and 1.14 for heating. Yearly investigation shows that the SAACS combined with 20 m2 CPC collector has an annual average solar fraction of domestic hot water of 0.85 and a discounted payback period of 3.12 years. These results demonstrate the feasibility and flexibility of the SAACS applied to residential buildings toward decarbonization. • Flexible modulation of solar energy enable application for residential buildings. • Thermodynamic model and experimental prototype are implemented. • Both heating and cooling supply make use of solar energy. • Heat driven temperature is as low as 60 °C. • Discounted payback period is 3.12 years. [ABSTRACT FROM AUTHOR]

This work describes an installation in Madrid, Spain, designed to test a new solar-powered air-cooled absorption refrigeration system. This installation essentially consists of a-48 m 2 field of flat-plate solar collectors, a 1500-L hot water storage tank and a single and-double effect air-cooled lithium bromide absorption prototype. Designed and built by our research group, this prototype is able to operate either as a single-effect unit (4.5 kW) or as a double-effect unit (7 kW). In operation as single-effect mode, the prototype is driven by solar energy, whereas in operation as a double effect mode, an external energy source may be used. The prototype's evaporator is connected to a fan-coil placed inside an 80-m 2 laboratory that represent the average size of a Spanish housing unit. In August 2009, the cooling system was tested in the single-effect operation mode. The results show that the system is able to meet approximately 65% of the laboratory's seasonal cooling demand, although 100% may be reached for a few days. The prototype can also operate in double-effect mode to meet the cooling demand. In that case, the prototype is fed by thermal oil, which is warmed until it reaches the process temperature in the high-temperature generator. The prototype can operate in either single-effect mode or in double-effect mode or can also operate simultaneously both modes using the components common to both modes, namely, the absorber, evaporator, condenser, solution pumps and control equipment. This paper reports the experimental results from the prototype operating separately in single-effect and double-effect mode. [ABSTRACT FROM AUTHOR]

Highlights: [•] New-structure finned-tube adsorption bed for enhancing heat and mass transfer. [•] Temperatures on different parts of the adsorption tubes differ little. [•] Maximum COP of 0.122 and maximum daily ice-making of 6.5kg are achieved by experiments. [•] Cooling efficiency of system with valve control higher than that without valve control. [ABSTRACT FROM AUTHOR]

Abstract: This work presents a combined optimization system to use solar energy as support for the ethanol industry. Solar radiation is used to produce energy in order to assist the cooling systems in the fermentation process. The experiments have been performed following a hardware in the loop technique by mixing the solar cooling plant in the Centro de Investigación de Energía Solar (CIESOL) located at the University of Almería (Spain), and a simulator of ethanol fermentation processes in Brazilian factories. The results are analyzed in detail to show the main advantages (important increment in ethanol production and use of clean energies) compared to the mode of operation of the current factories in Brazil. [Copyright &y& Elsevier]

Abstract: In this paper, we present a solar cooling installation located at the Center of Researches and Energy Technologies (CRTEn), in Bordj-Cédria, Tunisia. It is composed mainly of parabolic trough solar collectors, a 16kW LiBr double effect absorption chiller associated with a cooling tower, a backup heater, two tanks for storage and drain-back storage and a set of fan-coils installed in the building to be conditioned. The system was run in the summers 2008 and 2009 using a water solution as heat transfer medium (HTF) without storage. In summer 2010, thermal oil was used as a HTF instead of water and two tanks were added, one for temperatures stabilities and the other one as a backup tank for night storage. Two running strategies of the installation were adopted; starting with or without backup heater. The site specifications, the building loads, the chillier temperatures and heat flows, the parabolic trough solar collector efficiencies, the installation powers and performances were analyzed. It was found that the coefficient of performance COP was ranged between 0.8 and 0.91 during the installation running while the solar coefficient of performance SCOP was between 0.1 and 0.43. The maximum output of the absorption chiller was around 12kW. The drain backup night storage has improved the average solar fraction SF of the system which increased from 0.54 to 0.77. The avoided CO2 emission during a cooling season was estimated to be about 3000kg corresponding to an equivalent energy saving of 1154l of gasoil. [Copyright &y& Elsevier]

Abstract: The most commonly employed technology for cold production is vapour compression, mainly due to the high efficiency of such devices. However, a major operating issue is the strong dependency of system efficiency and capacity on ambient temperature, which in turn leads to low yearly performance and to a low capacity factor. On the other hand, solar cooling is gaining an increasing appeal as a way to locally exploit renewable energy sources and reducing carbon footprint. Many thermally driven systems are being currently studied, among these the ejection reverse cycle is being proposed as an interesting alternative due to its simplicity, low cost and reliability. The present paper aims to analyse a complex system in which the solar powered ejection machine is used to increase the efficiency of a traditional vapour compression machine by subtracting heat from the condenser. By means of a transient analysis, performed with a reference building and with climate data corresponding to four different system locations worldwide, the year-round performance of such a system in a space cooling application is estimated in terms of energy balance and savings on power costs with respect to the traditional solutions, in order to evaluate its potential benefits and to highlight some issues related to system design and operation. A sensitivity analysis is also performed with respect to solar collector area and equipment sizing, showing how the latter is an important optimisation parameter when designing the system. [Copyright &y& Elsevier]

Abstract: The water vapor adsorption properties of raw and hydrothermally treated fly ashes with NaOH and their application prospect as evaporative coolers of roof surfaces were studied. Initially, samples were characterized through techniques like elemental analysis, X-ray diffraction, thermogravimetry, reflectance measurements and water vapor adsorption isotherms. Moreover, the water adsorption properties and the associated temperature variations were determined in a specific wind tunnel with controllable environmental conditions. The adsorption isotherms for fly ash were of type III indicating hydrophobic material with low water vapor adsorption. The hydrothermal treatment in an alkaline solution transformed the fly ash in hydrophilic material of type IV. Moreover, the treated samples were capable of lowering their surface temperatures due to water evaporation and the release of the latent heat. The maximum difference of temperature increase under simulated solar irradiation was observed between the treated fly ash and the concrete with values of 5.0, 5.4 and 7.5°C for the surface, middle and bottom position, respectively. The results indicate that the zeolitic materials prepared from the fly ash samples have a significant potential for solar cooling applications. [Copyright &y& Elsevier]

Abstract: An experimental study of a thermochemical compressor with ammonia–lithium nitrate solution as working fluid has been carried out. This compressor incorporates a single-pass adiabatic absorber and all the heat exchangers are of the plate type: absorber subcooler, generator and solution heat exchanger. The thermochemical compressor has been studied as part of a single-effect absorption chiller hybridized with an in-series low-pressure compression booster. The adiabatic absorber uses fog jet injectors. The generator hot water temperatures for the external driving flow are in the range of 57–110°C and the absorber pressures range between 429 and 945kPa. Experimental results are compared with a numerical model showing a high agreement. The performance of the thermochemical compressor, evaluated through the circulation ratio, improves for higher absorber pressures, indicating the potential of pressure boosting. For the same circulation ratio, the driving hot water inlet temperature decreases with the rise of the absorber pressure. The thermochemical compressor, based on an adiabatic absorber, can produce refrigerant with very low driving temperatures, between 57 and 70°C, what is interesting for solar cooling applications and very low temperature residual heat recovery. Efficiencies and cooling power are offered when this hybrid thermochemical compressor is implemented in a chiller, showing the effect of different operating parameters. [Copyright &y& Elsevier]

Abstract: The performance of solar cooling systems with building-integrated (BI) solar collectors was simulated and the results compared with those having the solar collectors installed conventionally on the roof based on the weather data in Hong Kong. Two types of solar collectors and the corresponding cooling systems, namely the flat-plate collectors for absorption refrigeration and the PV panels for DC-driven vapour compression refrigeration, were used in the analysis. It was found that in both cases, the adoption of BI solar collectors resulted in a lower solar fraction (SF) and consequently a higher primary energy consumption even though the zone loads were reduced. The reduction in SF was more pronounced in the peak load season when the solar radiation was nearly parallel to the solar collector surfaces during the daytimes, especially for those facing the south direction. Indeed, there were no outputs from the BI flat-plate collectors facing the south direction between May and July. The more severe deterioration in the system performance with the BI flat-plate type collectors made them technically infeasible in terms of the energy-saving potential. It was concluded that the use of BI solar collectors in solar cooling systems should be restricted only to situations where the availability of the roof was limited or insufficient when applied in sub-tropical regions like Hong Kong. [Copyright &y& Elsevier]

Abstract: This paper presents the analysis of the performance of a solar cooling facility along one summer season using a commercial single-effect water–lithium bromide absorption chiller aiming at domestic applications. The facility works only with solar energy using flat plate collectors and it is located at Universidad Carlos III de Madrid, Spain. The statistical analysis performed with the gathered data shows the influence of five daily operational variables on the system performance. These variables are solar energy received along the day (H) and the average values, along the operating period of the solar cooling facility (from sunrise to the end of the cold-water production), of the ambient temperature (), the wind velocity magnitude (V), the wind direction (θ) and the relative humidity (RH). First order correlation functions are given. The analysis of the data allows concluding that the most influential variables on the daily cooling energy produced and the daily averaged solar COP are H, V and θ. The period length of cold-water production is determined mainly by H and . [ABSTRACT FROM AUTHOR]

Abstract: A methodology for assessing solar cooling technologies is proposed. The method takes into account location specific boundary conditions such as the cooling demand time series, solar resource availability, climatic conditions, component cost and component performance characteristics. This methodology evaluates the techno-economic performance of the solar collector/chiller system. We demonstrate the method by systematic evaluation of 25 feasible combinations of solar energy collection and cooling technologies. The comparison includes solar thermal and solar electric cooling options and is extended to solar cooling through concentrated solar power plants. Solar cooling technologies are compared on an economic and overall system efficiency perspective. This analysis has implication for the importance of solar load fraction and storage size in the design of solar cooling systems. We also stress the importance of studying the relation between cooling demand and solar resource availability, it was found that overlooking this relation might lead to overestimations of the potential of a solar cooling system in the range of 22% to over 100% of the actual potential. [ABSTRACT FROM AUTHOR]

Abstract: A solar-powered adsorption chiller with heat and mass recovery cycle was designed and constructed. It consists of a solar water heating unit, a silica gel-water adsorption chiller, a cooling tower and a fan coil unit. The adsorption chiller includes two identical adsorption units and a second stage evaporator with methanol working fluid. The effects of operation parameter on system performance were tested successfully. Test results indicated that the COP (coefficient of performance) and cooling power of the solar-powered adsorption chiller could be improved greatly by optimizing the key operation parameters, such as solar hot water temperature, heating/cooling time, mass recovery time, and chilled water temperature. Under the climatic conditions of daily solar radiation being about 16–21MJ/m2, this solar-powered adsorption chiller can produce a cooling capacity about 66–90W per m2 collector area, its daily solar cooling COP is about 0.1–0.13. [Copyright &y& Elsevier]

Abstract: In this paper, the simulation of the performance of solar-assisted heating and cooling systems is analyzed. Three different plant layouts are considered: (i) the first one consists of evacuated solar collectors and a single-stage LiBr–H2O absorption chiller; here in order to integrate the system in case of insufficient solar radiation, an electric water-cooled chiller is activated; (ii) configuration of the secondly considered system is similar to the first one, but the absorption chiller and the solar collector area are sized for balancing about 30% of the building cooling load only; (iii) the layout of the thirdly considered system differs from the first one since the auxiliary electric chiller is replaced by a gas-fired heater. Such system configurations also include: circulation pumps, storage tanks, feedback controllers, mixers, diverters and on/off hysteresis controllers. All such devices are modelled for maximizing the system energy efficiency. In order to simulate the systems’ performance for dynamic heating/cooling loads, a single-lumped capacitance building is also modelled and implemented in the computer code. A cost model is also developed in order to calculate the systems’ operating and capital costs. All the models and the relative simulations are carried out by TRNSYS. A design of experiment procedure is also included. By such tool the effects of the system operating parameters’ variation on the relative energy efficiency are analyzed. In addition, the set of synthesis/design variables maximizing the system’s energetic performance can be also identified. The annual primary energy saving is chosen as the optimization objective function, whereas collector slope, pump flows, set-point temperatures and tank volume are selected as optimizing system design variables. A case study was developed for an office building located in South Italy. Here, the energetic and the economic analysis for all the three considered system layouts are carried out. The simulations’ results are referred to both the initial and the optimized systems configurations. The highest primary energy saving vs. the reference traditional HVAC system is reached by the first considered system layout. The economic performance of the investigated solar heating/cooling systems is still unsatisfactory. The economical profitability of the considered solar heating and cooling systems can be improved only by significant public finding. From this point of view, the best results were achieved by the second above mentioned system configuration. [Copyright &y& Elsevier]

Abstract: The use of solar energy in buildings is an important contribution for the reduction of fossil fuel consumption and harmful emissions to the environment. Solar thermal cooling systems are still in their infancy regarding practical applications, although the technology is sufficiently developed for a number of years. In many cases, their application has been conditioned by the lack of integration between cooling and heating systems. This study aims to evaluate the potential of integrated solar absorption cooling and heating systems for building applications. The TRNSYS software tool was used as a basis for assessment. Different building types were considered: residential, office and hotel. The TRNSYS models are able to run for a whole year (365 days), according to control rules (self-deciding whether to operate in heating or cooling modes), and with the possibility of combining cooling, heating and DHW applications. Three different locations and climates were considered: Berlin (Germany), Lisbon (Portugal), and Rome (Italy). Both energy and economic results are presented for all cases. The different local costs for energy (gas, electricity and water) were taken into account. Savings in CO2 emissions were also assessed. An optimization of solar collector size and other system parameters was also analysed. [Copyright &y& Elsevier]

Abstract: Performance variations of a solar-powered ejector cooling-system (SECS) using an evacuated-tube collector are presented for Antalya, Aydin, Konya and Urfa cities located in the southern region of Turkey by means of hourly and monthly average ambient temperature and solar radiation meteorological data. A SECS, based on a constant-area ejector flow model and using R-123, was considered. The cooling season and period were taken into account for the 6 months (May–October) and the hours 8:00–17:00, respectively. It was found that the evacuated-tube collector efficiency depending upon the ambient temperature and solar radiation within the day was remarkably varied. However, for all the cities, the cooling capacities of the SECS were very similar. When generator, condenser, and evaporator temperatures were taken, namely, 85°C, 30°C and 12°C, the maximum overall coefficient of performance and the cooling capacity were obtained as 0.197 and 178.26W/m2, respectively, at 12:00 in August for Aydin. The evacuated-tube collector area per ton cooling was found to be around 21m2 at noontime in August for all the cities. Furthermore, at the off-design conditions, a performance map of the system was derived and discussed. It was determined that the SECS could be used for office-cooling purposes during the hours (8:00–15:00) in the southern region of Turkey. [Copyright &y& Elsevier]

• A new elastocaloric cooling system is proposed to harvest low-grade heat. • Transition temperature gradient facilitates cascade utilization of low-grade heat. • Transition temperature gradient improves system COP by a factor of more than 5. • Optimizing transition temperature profile can further boost performance for 20%. • Solar thermal air-conditioner and refrigerator are two potential applications. Unlike the conventional elastocaloric cooling system that depends on electricity, the coupled elastocaloric power and cooling cycle proposed in this study exploits low-grade thermal energy in a cascade manner, which opens a new paradigm for the caloric cooling community. Cascade utilization of heat relies on a gradient of transition temperature inside the shape memory alloy actuator that best matches the temperature profile of the material during operation. A transient numerical model is developed to simulate the performance of this new system, and the model is experimentally validated. The transition temperature gradient should exceed 60 K for optimum utilization of input heat. At the same gradient, the distribution of transition temperature can be optimized, where at least 10% improvement over linear profile can be expected in terms of efficiency and cooling power density. Based on the superior performance, this technology could be powered by solar thermal collectors working at 110 °C and could be applied to residential air-conditioners and off-grid refrigerators. The novel system proposed in this study not only complements the existing library of heat-activated cooling technologies, but also provides a new pathway for the expansion of caloric cooling at large. [ABSTRACT FROM AUTHOR]