Conventional Solar Water Heater Research Articles

Latent Heat Storage in a Two-Phase Thermosyphon Solar Water Heater

This article experimentally studies the thermal performance of latent heat storage in a two-phase thermosyphon solar water heater, which utilizes the superior heat transfer characteristics of boiling and condensation, and eliminates drawbacks found in the conventional solar water heater. Experimental investigations are first conducted to study the thermal behavior of tricosane (paraffin wax 116), water, and sodium acetate (NaCH3COO∙3H2O) used as energy storage materials. The results indicate that tricosane provides many advantages to be the energy storage material in the latent heat storage system. This study also examines the functions of charge and discharge thermal behaviors in a two-phase thermosyphon solar water heater. The results show that the system gives optimum charge and discharge performance under 40% alcohol fill ratio and with tricosane used as the energy storage material, and displays an optimum charge efficiency of 73% and optimum discharge efficiency of 81%.

Long-term performance of solar-assisted heat pump water heater

A long-term reliability test of an integral-type solar-assisted heat pump water heater (ISAHP) was carried out. The prototype has been running continuously for more than 13,000 h with total running time >20,000 h during the past 5 yr. The measured energy consumption is 0.019 kWh/l of hot water at 57 oC that is much less than the backup electric energy consumption of the conventional solar water heater.

Optimisation of minimum backup solar water heating system

Current flat plate solar water heaters overproduce slightly in summer and have poor performance in winter at the time of maximum load. They use an expensive absorber plate over the entire absorbing aperture of the collector and fail to use the backside of the absorber. They often have under insulated tanks and are not optimised as integrated systems. This paper describes a design approach taken to use existing commercial flat plate absorber and tank components in a new way to maximise solar contribution and minimise material usage in the construction of the system. The design criterion used is not maximum peak efficiency, but minimum annual backup energy supplied to the system to meet an annual load. This corresponds to meeting a minimum greenhouse emissions requirement in both invested pollution during manufacture and pollution from backup energy supplied. Two new designs are shown which allow the solar fraction of systems to be increased to approximately 80–90% in Sydney Australia using a standard model of domestic hot water usage specified in Australian Standard AS4234. Pollution from fuel use drops to as little as 40% of that of conventional flat plate solar water heaters. These new designs use one absorber plate instead of two and a smaller and better insulated tank. Comparisons of solar fraction are evaluated for a range of climatic conditions. An important insight is that with such a performance optimised system the ultimate solar fraction is limited by occasional long duration cloud cover at the site of installation and making the system larger only increases dumped energy, not utilisable energy. Technical efficiency improvements only reduce the required collector area. However, some additional backup fuel reductions can be made through manual control of backup energy use, because this allows finer control of backup relative to real demand. Pollution from backup fuel usage may be able to be reduced to 1/4 that of current flat plate solar water heaters.

Experiments of a solar flat plate hybrid system with heating and cooling

Based upon the prior research of the solar hybrid water heater and refrigerator, a new flat plate solar hybrid system with heating and cooling was proposed and experimental prototype device was constructed. With this new hybrid system, the heat and mass transfer can be improved effectively both in desorption process and adsorption process. The conventional flat plate solar water heater collector absorber is immersed inside adsorbent bed in the new hybrid system. The experimental results show that not only the cooling effect can be obtained, but also both the sensible heat of the adsorbent bed and the adsorption heat can be recovered effectively to produce hot water for domestic use. The COP of this new flat plate hybrid system can reach 0.11 and the heat efficiency is about 0.45, this achievement has demonstrated an efficient way of the application of solar energy.

Performance evaluation of solar photovoltaic/thermal systems

The major purpose of the present study is to understand the performance of an integrated photovoltaic and thermal solar system (IPVTS) as compared to a conventional solar water heater and to demonstrate the idea of an IPVTS design. A commercial polycrystalline PV module is used for making a PV/T collector. The PV/T collector is used to build an IPVTS. The test results show that the solar PV/T collector made from a corrugated polycarbonate panel can obtain a good thermal efficiency. The present study introduces the concept of primary-energy saving efficiency for the evaluation of a PV/T system. The primary-energy saving efficiency of the present IPVTS exceeds 0.60. This is higher than for a pure solar hot water heater or a pure PV system. The characteristic daily efficiency η s* reaches 0.38 which is about 76% of the value for a conventional solar hot water heater using glazed collectors ( η s*=0.50). The performance of a PV/T collector can be improved if the heat-collecting plate, the PV cells and the glass cover are directly packed together to form a glazed collector. The manufacturing cost of the PV/T collector and the system cost of the IPVTS can also be reduced. The present study shows that the idea of IPVTS is economically feasible too.

Solar water heaters based on concrete collectors

In the present paper, a study has been carried out on the solar concrete collectors providing domestic hot water. The cement concrete collectors are made up of thin cement concrete slabs with a network of aluminum pipes embedded over its surface. No glazing on the top of the cement collector solar collector or insulation at the back have been used as in conventional solar water heaters. Although concrete collectors without glazing at the top are less efficient they can provide moderate hot water to meet the various requirements of the building during the day. The cement concrete solar collectors have been tested for water heating for several years and the results are presented. This knowledge can be used by architects for designing the roof of the building which may serve as a low cost solar collector to provide hot water at moderate temperature in buildings for meeting various purposes during the daytime.

Integrated collector-storage systems with suppressed thermal losses

Stationary concentrating solar devices, of the integrated collector and storage (ICS) type, that consist of a cylindrical tank placed horizontally in a properly shaped, curved mirror envelope, were designed. Prototype models were constructed, tested, and compared with conventional solar water heaters. In this article we describe the design of the ICS solar units with respect to the minimization of thermal losses from the absorber to the ambient. Experimental results were derived from the constructed models, a conventional concentrating stationary ICS prototype, and flat plate collectors of the thermosiphon type. Finally some conclusions regarding the practical application of the integrated units are presented.

Studies on collector-cum-storage type solar water heaters under arid zone conditions of india

Conventional natural circulation type solar water heaters are very costly. Though manufactured in India, they are beyond the reach of the common man. To reduce the cost, a collector-cum-storage type solar water heater has been developed and its detailed study has been carried out and reported. The heater can provide 100 1 of hot water at a temperature of 55–60°C in the evening which can be retained at 40–45°C until the next morning. The efficiency of the heater varies from 57.4 to 66.0 per cent depending on design parameters.

Performance and testing of improved natural circulation type solar water heater in Arid areas

A conventional natural circulation type solar water heater has been improved upon by eliminating the float valve and using a sealed pressure tank instead of an open tank. Performance of the improved natural circulation type solar water heater has been compared with and without solar-selective surfaces. The detailed design, fabrication and testing have been reported in this paper. The efficiency of the improved natural circulation type solar water heater with and without solar-selective surfaces is 57.5 and 51.0%, respectively.

Upgrading heat by a reversed absorption heat pump

Analysis of a reversed absorption heat pump's performance for upgrading low temperature waste-heat from industrial processes and solar heat from a flat-plate solar collector has been carried out. In the case of upgrading waste-heat, the ratio of output to input heat decreases as the temperature at which the output heat is needed increases. For water heating, the performance of the conventional solar water heating system is better than that of the heat pump system because in the latter case, heat is rejected from the condenser.

A Recuperative Solar Collector

This investigation is a theoretical and experimental study of a recuperative type solar water heater where water is allowed to pass through the two upper transparent covers in channel flow before flowing through the tubes of the collector. The water in the channel will be first heated by solar insolation absorbed in the fluid layer and by the upper heat losses from the absorber plate before being heated in the main collector tubes. The performance of this collector was analytically studied under various environmental and operating conditions, in addition, an experimental apparatus was built, commissioned and tested. The analytical model, confirmed by experimental results, indicated that the proposed design was superior to the conventional solar water heater within a certain range of mass flow rates and environmental conditions.

Advances in solar water heating for domestic use in Australia

A method enabling retrofitting of solar collectors to existing domestic, low pressure electric water heaters has been developed and tested. The performance of the proposed system was found to be comparable with the performance of conventional solar water heaters when the size of the solar collectors is suitably matched to the average daily consumption of hot water. Other developments described are a solar energy operated pump and an airlift pump, both suitable for circulation of water in domestic solar water heaters, and an electronic controller for the circulating pumps.