Design improvements for a collector/generator/adsorber of a solid adsorption solar refrigerator

A study of the effects of different collector design parameters on the performances of a solar powered solid adsorption refrigerator is presented. The refrigerator uses activated carbon/methanol as the adsorbent/refrigerant pair. The study was undertaken using a computer simulation program developed from a transient analysis of the system. The parameters tested are the collector plate emissivity/absorptivity combination, adsorbent packing density, tube spacing, outer tube outside diameter, adsorbent thermal conductivity, heat transfer coefficient at adsorbent/tube interface, and adsorbent tube/collector plate materials combination. Two performance indicators namely, condensate yield and coefficient of performance (COP) were used in the study as figures of merit. A multiple regression technique was used to correlate the performance indicators with the collector parameters through a quadratic relation. Consequently an objective function, suitable for selecting optimal values of the parameters is defined, subject to specified constraints. Selecting the COP as the preferred indicator parameter, optimization was then carried out. Improvements in the ranges of 29–38% for COP and 26–35% for condensate yield were obtained with optimal choices of tube spacing, adsorbent packing density and collector plate/adsorbent tube material combinations.     

Experimental investigation and analysis on a thermoelectric refrigerator driven by solar cells

Experimental investigation and performance analysis on a solar cell driven, thermoelectric refrigerator has been conducted. Research interest focused on testing the system performance under sunshine. Experiment results demonstrated that the unit could maintain the temperature in the refrigerator at 5–10°C, and have a COP about 0.3. Further analysis indicated that the performance of the system is strongly dependent on intensity of solar insolation and temperature difference of hot and cold sides for the thermoelectric module, etc. There exist optimum solar insolation rates, which let the cooling production and COP achieve maximum value, respectively. It was expected that the refrigerator would be potential for cold storage of vaccine, food and drink in remote area, or outdoor conditions where electric power supply is absent.     

Study of solar energy powered transcritical cycle using supercritical carbon dioxide

In this paper, the performance of solar energy powered transcritical cycle using supercritical carbon dioxide for a combined electricity and heat generation, is studied experimentally. The experimental set‐up consists of evacuated solar collectors, pressure relief valve, heat exchangers and CO₂ feed pump. The pressure relief valve is used to simulate operation of a turbine and to complete the thermodynamic cycle. A complete effort was carried out to investigate the cycle performances not only in summer, but also in winter conditions. The results show that a reasonable thermodynamic efficiency can be obtained and COP for the overall outputs from the cycle is measured at 0.548 and 0.406, respectively, on a typical summer and winter day. The study shows the potential of the application of the solar energy powered cycle as a green power/heat generation system. Copyright © 2006 John Wiley & Sons, Ltd.     

Preliminary investigation of a transcritical CO2 heat pump driven by a solar‐powered CO2 Rankine cycle

In this paper, a transcritical carbon dioxide heat pump system driven by solar‐owered CO₂ Rankine cycle is proposed for simultaneous heating and cooling applications. Based on the first and second laws of thermodynamics, a theoretical analysis on the performance characteristic is carried out for this solar‐powered heat pump cycle using CO₂ as working fluid. Further, the effects of the governing parameters on the performance such as coefficient of performance (COP) and the system exergy destruction rate are investigated numerically. With the simulation results, it is found that, the cooling COP for the transcritical CO₂ heat pump syatem is somewhat above 0.3 and the heating COP is above 0.9. It is also concluded that, the performance of the combined transcritical CO₂ heat pump system can be significantly improved based on the optimized governing parameters, such as solar radiation, solar collector efficient area, the heat transfer area and the inlet water temperature of heat exchange components, and the CO₂ flow rate of two sub‐cycles. Where, the cooling capacity, heating capacity, and exergy destruction rate are found to increase with solar radiation, but the COPs of combined system are decreased with it. Furthermore, in terms of improvement in COPs and reduction in system exergy destruction at the same time, it is more effective to employ a large heat transfer area of heat exchange components in the combined heat pump system. Copyright © 2012 John Wiley & Sons, Ltd.     

Second law analysis of the 160 Wp standalone solar photovoltaic system

The demand for solar photovoltaic (SPV) systems is growing all over the world due to the continuous increase in the cost of conventional means of power. India has the advantage of around 300 clear sunny days in a year. However, the biggest problem is conversion efficiency. In this paper, an attempt has been made for evaluating the second law efficiency of 160?Wp stand-alone SPV systems installed in RKGIT Ghaziabad premises. The performance of a SPV system depends on climate conditions like temperature, air velocity and a number of sunny days. The solar energy striking the solar panels gets converted into electric and thermal energy. In this work, we have considered the effect of ambient temperature and air velocity on the efficiency of solar panels. The average second law efficiency of SPV systems was found to be 10.7%, whereas maximum second law efficiency was 13.8% at 9am on the same day. The efficiency of the SPV system can be improved by maintaining the temperature of the module.     

The study and performance of a modified conventional refrigerator to serve as a PV powered one

This paper describes the design and development stages to convert a conventional refrigerator to a solar powered one. The development of such a system was effected and the results of this work to provide a cost effective version are given.A conventional refrigerator was chosen and some changes were introduced to reduce the cooling load and consequently the power required. Tests were carried out to study the performance of the refrigerator components and especially the compressor's, as well as the refrigerator as a whole. The latter tests are the well-known pull down tests.The cost effective final product was searched via a PV sizing package developed for the purpose of this project incorporating the LCC analysis.     

Optimal COP prediction of a solar intermittent refrigeration system for ice production by means of direct and inverse artificial neural networks

A direct and inverse artificial neural network (ANN and ANNi) approach were developed to predict the required coefficient of performance (COP) of a solar intermittent refrigeration system for ice production under various experimental conditions. Ammonia/lithium nitrate was used as a working fluid considering different solution concentrations. The configuration 6-6-1 (6 inputs, 6 hidden and 1 output neurons) presented an excellent agreement (R > 0.986) between experimental and simulated values. The used inputs parameters were: the solution concentration, the cooling water temperature, the generation temperature, the ambient temperature, the generation pressure and the solar radiation. The sensitivity analysis showed that all studied input variables have effect on the COP prediction but the generation pressure is the most influential parameter on the COP, while the rest of input parameters were less significant. COP performance was also determined by inverting ANN to calculate the unknown input parameter from a required COP. Because of the high accuracy and short computing time makes this methodology useful to simulate and to optimize the solar refrigerator system.     

Field experience study and evaluation for hydrogen production through a photovoltaic system in Ouargla region,Algeria

An experimental study on small-scale for solar hydrogen production system via a Proton Exchange Membrane electrolysis under a desert climatic condition in Ouargla region (South-East of Algeria) has been carried out, the target of this study has been first to evaluate hydrogen production by water analysis and to store the solar energy which has had the form of a hydride-metal hydrogen, after that, to investigate the performance of sophisticated commercial electrolyser (HG-60)powered by photovoltaic panels via the Power Management Unit (PMU) as a power conditioner, this paper has also a mathematical models based on real-time experiments were used to simulate both the photovoltaic system and PEM electrolyser work, along with attempting to direct linking strategy with the same experimental components of photovoltaic panels and commercial electrolyser, it was found through this study, the addition of the number of commercial electrolyser with the bank of four HG-60 stacks in series. More effective considering the improving voltage matching, with power transfer efficiency reach to 99%, also another factor is the photovoltaic panels slope on panel output power and hydrogen productivity are theoretically examined, where the proper selection of optimal tilt angle has an importance for collecting the maximum hydrogen amount, eventually, over the experiment span, the real-amount of hydrogen vented over experiment course is around 92.54l.     

Experimental investigation on a thermoelectric refrigerator driven by solar cells

Experimental investigation and relevant analysis on a solar cell driven, thermoelectric refrigerator has been conducted. To make the device portable, daytime use and nighttime use of the refrigerator are treated in different ways. Solar cells are applied to power the refrigerator in the day. Storage battery, assisted by an a.c. rectifier, is used to provide electric energy in the night and in cloudy or rainy days. Experiment results demonstrate that the unit can maintain the temperature in the refrigerator at 5–10 °C, and have a COP about 0.3. It is expected that the refrigerator would be potential for cold storage of vaccine, foodstuffs and drink in remote area, or outdoor applications where electric power supply is absent.     

Experimentation of a solar adsorption refrigerator in Morocco

For countries with a high potential of solar energy, producing cold using solar energy is a promising way to sustainable development since the energy used is free and not harmful for the environment.This work proposes a solar adsorption refrigerator using the pair activated carbon–methanol, which has been totally built and is under experimental tests in the solar laboratory of the Faculty of Sciences of Rabat, the capital of Morocco with Mediterranean climate.The solar adsorption refrigerator is mainly composed of a collector containing the adsorbent, an evaporator and a condenser. The results show that the refrigerator gives good performance in Rabat. The unit produces cold even in rainy and cloudy days and the temperatures achieved by the unit can be less than −11 °C for days with a very high irradiation. The solar coefficient of performance (COP) (cooling energy/solar energy) ranges between 5% and 8% for an irradiation between 12,000 and 28,000 kJ m⁻² and a daily mean ambient temperature around 20 °C.     

Performance analysis of a PV-powered health clinic with multi-stagedual priority regulator

The performance of a photovoltaic powered health clinic system designed, built, and evaluated at the University of Lowell is investigated. This system uses two separate batteries, one to power a vaccine refrigerator and the other to power auxiliary loads. The two batteries were sized according to the demand of their loads. The power control system utilizes a five-stage dual priority controller to charge the two separate batteries from a single modular photovoltaic array. The main refrigerator battery always has priority over the auxiliary battery; therefore, the use of auxiliary loads will never jeopardize the reliability of the critical load. This system provides power for auxiliary loads while utilizing the same number of photovoltaic modules as systems which power only a vaccine refrigerator. The performance of this system was evaluated using a data acquisition system, and the experimental results are compared with theoretical values     

Effect of load pattern on solar-boosted heat pump water heater performance

The performance of a solar-boosted heat pump water heater (HPWH) operating under full load and part load conditions was determined in an outdoor experimental study. The system utilised flat unglazed aluminium solar evaporator panels to absorb solar and ambient energy. Absorbed energy was transferred to the water tank by means of the heat pump and a wrap around condenser coil on the outside of the tank. The system COP was found to be in the range of 5–7 under clear daytime conditions and 3–5 under clear night-time conditions. Using part load testing of the HPWH system it was found that concentrating the coils in the lower portion of the tank could increase the efficiency of the condenser coil. It was also shown that there exists a generalised linear relationship that can be used to describe the system COP in terms of the temperature difference between the water in the storage tank and the ambient air.     

Adsorption cooling driven by solar collector: A case study for Tokyo solar data

An analytical investigation has been performed to study the possibility of application of solar cooling for the climatic condition of Tokyo, Japan. Silica gel–water adsorption cooling system has been taken into consideration for the present study and lumped parameter model is used to investigate the performance of the system. Based on the solar radiation data it is found that at least 15 collector (each of 2.415 m²) is required to achieve the required heat source temperature (around 85 °C) to run the cooling unit. It is also observed that the solar powered adsorption cooling unit provides cooling capacity around 10 kW at noon with base run conditions, while the system provides solar COP around 0.3, however, the solar collector size can be reduced by optimizing the cycle time.     

Experimental study on the performance of solar Rankine system using supercritical CO2

An experimental study is carried out to investigate the performance of a solar Rankine system using supercritical CO₂ as a working fluid. The testing machine of the solar Rankine system consists of an evacuated solar collector, a pressure relief valve, heat exchangers and CO₂ feed pump, etc. The solar energy powered system can provide electricity output as well as heat supply/refrigeration, etc. The system performance is evaluated based on daily, monthly and yearly experiment data. The results obtained show that heat collection efficiency for the CO₂-based solar collector is measured at 65.0–70.0%. The power generation efficiency is found at 8.78–9.45%, which is higher than the value 8.20% of a solar cell. The result presents a potential future for the solar powered CO₂ Rankine system to be used as distributed energy supply system for buildings or others.     

Design optimization of the flat plate collector for a solid absorption solar refrigerator

A study of the effects of various collector design parameters on the performance of a solar powered solid absorption refrigerator is presented. The refrigerator uses specially treated CaCl₂ as absorbent and NH₃ as refrigerant and operates intermittently in a diurnal cycle. The study is undertaken using version 4.0 of a simulation programme, COSSOR, developed from a transient analysis of the system. A large number of simulations was undertaken to test the performance of the refrigerator for various choices of the collector design parameters. The latter include the plate emissivity and material; absorbent pellet diameter, thermal conductivity and packing density; collector tube size, spacing and material; and number of glazing. The refrigerator performance indicators, namely total condensate yield, mass of ice produced, coefficient of performance and effective cooling, are presented for the range of values of the collector parameters of interest. Using a multiple linear regression technique, the performance indicators are correlated with the collector parameters by simple linear polynomial expressions. An objective function, suitable for selecting optimal values of the parameters, is defined, subject to specified constraints. Optimization was then carried out for the objective function. For the collector with steel tubes and steel plate, the refrigerator coefficient of performance obtained with optimal choices of tube size, spacing and plate emissivity is 0.073, representing an improvement of at least 30% with respect to the reference collector. A similar level of improvement was obtained for a collector with aluminium tubes and plate.     

Photovoltaic‐powered cold store and its performance

A photovoltaic‐powered cold store plant, the first of its kind, has been developed to store 10 tons of frozen fish at ?15°C. It consists of a photovoltaic array (4 kW peak), a battery bank (96 V DC, 180 A H), a vapour compression refrigeration system (1 ton), electronic controls for automatic operation of plant and an insulated cold chamber. Experiments were conducted on the system to evaluate its performance with no heat load (frozen fish at ?15°C) and with different heat loads. It is observed that the system can be operated with a maximum heat load of 2350 W to maintain the walk‐in‐cooler temperature below the freezing point of fish (?2°C). The performance studies conducted on these subsystems viz., photovoltaic array and battery bank showed that their output has deteriorated in 5 years. Copyright © 2001 John Wiley & Sons, Ltd.     

Optimally sizing of solar array and battery in a standalone photovoltaic system in Malaysia

Size optimization of solar array and battery in a standalone photovoltaic (SPV) system is investigated. Based on the energy efficiency model, the loss of power supply probability (LPSP) of the SPV system is calculated for different size combinations of solar array and battery. For the desired LPSP at the given load demand, the optimal size combination is obtained at the minimum system cost. One case study is given to show the application of the method in Malaysian weather conditions.     

Experimental study and analysis on novel thermo-electric cooler driven by solar photovoltaic system

Experimental study and analysis on thermoelectric cooler driven by solar photovoltaic system has been carried out. Here the research attention is on testing of system performance under solar insolation. Experimental results revealed that unit could maintain the temperature in the cooler at 10–15°C and have a coefficient of performance (COP) of about 0.34. Analysis of thermoelectric cooling system has been conducted on the basis of COP, cooling capacity and environmental issues. Further investigations verified that the performance of the system is a function of solar insolation rate and temperature difference of hot and cold sides of thermoelectric module etc. There subsist most favorable solar insolation rate which allows COP and cooling production to be maximum value respectively. It is anticipated that the cooler would have prospective for cold storage of vaccine, food and drink in remote and rural areas or outdoor conditions where electricity is not available.