An experimental investigation into the performance of a domestic forced circulation solar water heater under varying operating conditions

An experimental investigation is carried out on a forced circulation solar water heater to assess its performance under various operating conditions. The system consisted of two identical collectors of total absorber area of 3.45 m² and a storage tank of 200 litre capacity. Experiments were carried out during clear days with and without system loading for two water mass flow rates through the collector; namely 0.1305 kg/s and 0.06525 kg/s. The system was operated without thermostat control and with thermostat control at maximum and minimum settings. The collector efficiency improved with system loading. The improvement was better with increased hot water withdrawal from the system.     

Performance and testing of large-size solar water heater cum solar cooker

The performance of a novel device has been tested. The device can be used as a collector cum storage type solar water heater during the winter, and, with minor adjustments, it can be used as a hot-box solar cooker. The device can provide hot water at 50–60°C in the evening, which can be maintained at 40–45°C until the following morning. It can also be used for cooking food for about 40 people. The efficiencies of the device as a solar water heater and as a solar cooker have been found to be 67.7% and 29.8%, respectively. The payback period varies between 1.64 to 5.90 years depending on the fuel it replaces. The payback periods are of increasing length with respect to the fuels firewood, coal, electricity, LPG and kerosene.     

Refrigerant-charged integrated solar water heater

The performance of two R-11-charged integrated solar water heater collectors was investigated experimentally for forced and natural circulation water flows. The heat transfer from the refrigerant loop to the hot water storage tank took place through a condenser of novel design integrated within the collector frame. The effect of the condenser inclination on the system efficiency was remarkable for natural circulation water flow but had no significant effect for forced circulation flow. The difference in thermal response between the refrigerant and water loops caused buildup of stored energy in the condenser. This energy affected the buoyancy forces and generated flow pulsation that caused a harmonic-like variation of the system efficiency. This effect vanished with forced water circulation flow. The system efficiency varied between 20 and 50% depending on the solar insolation.     

Experimental and analytical performance study of a thermosyphon water heater

The performance of a thermosyphon solar water heater was studied analytically and experimentally. A finite-difference model was used to predict year-round performance. Tests were conducted on an experimental heater subjected to acutal weather conditions in Benghazi, Libya. Satisfactory qualitative and quantitative agreement was found between experimental and predicted results. A storage volume of 60 liters per unit collector area was found to be optimum for Benghazi conditions. The day-end temperature was found to vary between 23° and 51°C for the test period, which occurred in winter, with an average of 41°C.     

A new type of solar water heater

This investigation reports a new type of solar water heating system without water pipes on the collector surface or a separate storage tank. The water to be heated continuously flows perpendicularly from an upper transparent cover to a porous absorber and is stored in a small volume beneath this assembly. Three different systems were designed, manufactured and tested but only one proved to be successful; this design indicated higher thermal efficiency compared to conventional collectors at high flow rates whereas at low flow rates the opposite is true.     

Year-round performance of an improved collector-cum-storage type solar water heater

Systematic studies have been carried out on collector-cum-storage type solar water heaters, and efforts were made to minimise heat losses so that this type of water heater can be used for getting hot water at 40°–45°C for taking baths in the early morning hours of the next day. This paper reports year round performace, the performance equation and economics of this new improved solar water heater. This heater can supply 100 litres of hot water at 60°–70°C in the afternoon, and 40°–45°C temperature can be retained till next day morning. Its efficiency is 70.1%.     

Performance prediction of a solar water heater with intermittent output

A solar water heater constructed from readily available materials in the countryside has earlier been discussed in the continuous flow mode. Water flows in the tubes at a constant rate throughout the day. In any realistic situation, however, the rate of flow will be a function of time depending on the requirements of the user. In this paper a theoretical method is developed which is used to predict the outlet water temperature of the time dependent flows. The effect of various design parameters like the position of the water pipes, choice of sensible heat storage material etc. are discussed taking different functions of rate of flow. The inexpensive water heater can provide hot water for a small household even in the late evening hours provided no heat is withdrawn from the system during the day time.     

Experimental observations on a continuous flow type domestic solar water heater

The operation of a continuous flow type domestic solar water heater is explained with the help of a schematic diagram. Steady state thermal analysis of such a water heater is carried out. A water heater of this type with a collector area of 1 m² is subjected to tests. The experimental results are compared with predicted results. The experimental results have also been compared with those obtained from a water heater operating on thermosiphon flow. The performance of the continuous flow type water heater is shown to be comparable to that of the thermosiphon flow type. It is concluded that, in the Indian context, the continuous flow type water heater has more advantages than the thermosiphon flow type water heater in view of its low capital cost and the ease of operation and maintenance.     

An experimental investigation into the performance of a domestic thermosyphon solar water heater under varying operating conditions

An experimental investigation has been carried out on a thermosyphon solar water heater. The system consisted of a flat-plate collector of 1.5 m² absorber area with 21 tubes/m width and storage tank of 125 litre capacity. Experiments were carried out for both cloudy and clear weather conditions in winter and summer. The hourly system performance was evaluated for all test conditions. The final mean tank temperature was measured daily which enabled the calculation of the possible contribution of solar energy for domestic hot water supply in Basrah, Iraq (latitude 30.76°N). The system was tested at both no-load and loading conditions. Intermittent and continuous load was imposed, and system performance was evaluated for each condition.     

Study of a solar water heater using stationary V-trough collector

There are various types of solar water heater system available in the commercial market to fulfill different customers’ demand, such as flat plate collector, concentrating collector, evacuated tube collector and integrated collector storage. A cost effective cum easy fabricated V-trough solar water heater system using forced circulation system is proposed. Integrating the solar absorber with the easily fabricated V-trough reflector can improve the performance of solar water heater system. In this paper, optical analysis, experimental study and cost analysis of the stationary V-trough solar water heater system are presented in details. The experimental result has shown very promising results in both optical efficiency of V-trough reflector and the overall thermal performance of the solar water heater.     

A simplified approach for evaluating performance of a solar water heater with side losses

We present a simplified method which could be used to calculate, to a first approximation, the energy losses from the sides of a solar collector/water heater. The inclusion of energy losses through the side walls of a reasonable thickness reduce the efficiency of the system by about 5%. The integrated side energy losses for the whole day are not equal for the various segments of the wall. Hence, it will be economical to construct wedge shape walls, thickness decreasing downward, instead of usual rectangular walls.     

Flat-plate collector construction and system configuration to optimize the thermosiphonic effect

Thermosiphon systems heat potable water or heat transfer fluid and use natural convection to transport it from the collector to storage. This type of technology is applied extensively in countries with good sunshine potential. One such example is Cyprus, which is currently the leading country in the world with respect to the application of solar water heaters for domestic applications, with more than 93% of the houses equipped with such a system. The performance of such a system depends on many factors including the collector construction and the arrangement of the system, mainly with respect to the distance between the top of the solar collector and the bottom of the storage tank and the solar collector slope, which affects both the energy collected and the hydrostatic pressure of the system. A typical system in Cyprus uses 3 m² of collectors, 160 l storage, its collectors are usually inclined at 45° from horizontal and has 15 mm copper riser tubes and header tubes with a diameter of 28 mm. The collector absorber plate is also made from copper. The main objective of this paper is to investigate through modeling and simulation possible configurations, which will optimize the performance of the system. For this purpose, a number of riser and header tube diameters were considered ranging from 6 mm to 35 mm, slopes from 20° to 90° and distances between the top of the collector to the bottom side of the storage tank ranging from ±15 cm. The system is modeled using TRNSYS and simulated with the Typical Meteorological Year (TMY) of Nicosia, Cyprus. The results showed that the best-optimized system is obtained for small header and riser pipe diameters and very close performance is obtained for various combinations. Therefore, the decision on the optimum system should depend on cost issues, which are currently very important because of the increased price of copper and operational problems depending on the hardness of the water in the area of installation, which could cause scale deposits that could clog the riser pipes. The optimum slope is found to be equal to the latitude plus 10°, i.e., 45°, although a smaller slope does not affect the performance a lot, and the optimum distance between the top of the collector and the bottom of the storage tank is −15 cm. These findings should prove valuable for the collector and systems designers and manufacturers.     

家用太阳热水器与太阳热水系统的技术经济比较

分析了户用太阳热水器和太阳热水系统工程的经济技术特点,对两者成本构成、项目财务净现值、投入回收期和财务内部收益率等有关指标进行了经济技术比较.分析比较表明,太阳热水系统与家用热水器相比,节省安装占地,与建筑相结合得好,在降低成本,缩短投资回收期,提高经济效益方面有明显的优势.     

Experimental studies of a new solar water heater system using a solar water pump

The research goal was to develop a new solar water heater system (SWHS) that used a solar water pump instead of an electric pump. The pump was powered by the steam produced from a flat plate collector. Therefore, heat could be transferred downward from the collector to a hot water storage tank. The designed system consisted of four panels of flat plate solar collectors, an overhead tank installed at an upper level and a large water storage tank with a heat exchanger at a lower level. Discharge heads of 1, 1.5 and 2 m were tested. The pump could operate at the collector temperature of about 70–90 °C and vapor gage pressure of 7–14 kPa. It was found that water circulation within the SWHS ranged between 12 and 59 l/d depending on the incident solar intensity and system discharge head. The average daily pump efficiency was about 0.0014–0.0019%. Moreover, the SWHS could have a daily thermal efficiency of about 7–13%, whereas a conventional system had 30–60% efficiency. The present system was economically comparable to a conventional one.     

Effect of thermal trap on the performance of an underground shallow solar pond water heater

A simple analysis of an underground shallow solar pond water heater has been presented. The effect of a thermal trap at the top of the system has also been incorporated in the analysis. Using the model, the effect of various system parameters, viz. thermal trap thickness, heat capacity of water mass, flow rate and duration of flow rate have been studied in detail. Numerical calculations have been made for a typical winter day at New Delhi (India). It is concluded that the system with thermal trap gives better performance in comparison with a system with a movable insulation system.     

Year round performance of a cylindrical solar water heater

A cylindrical collector-cum-storage type solar water heater has been designed, developed and tested. Its year round performance has been carried out and reported in this paper. The heater can provide 50 litres of hot water at 50–60°C in the afternoon and a temperature of 35°C can be retained till the next day for early morning use. The heater receives approximately 30% more radiation as compared to a flat surface. The economics of the heater has been worked out and it has been found that the cost can be recovered within one year.     

Heat-pipe enhanced solar-assisted heat pump water heater

A heat-pipe enhanced solar-assisted heat pump water heater (HPSAHP) is studied. HPSAHP is a heat pump with dual heat sources that combines the performance of conventional heat pump and solar heat pipe collector. HPSAHP operates in heat-pump mode when solar radiation is low and in heat-pipe mode without electricity consumption when solar radiation is high. HPSAHP can thus achieve high energy efficiency. A prototype was designed and built in the present study. An outdoor test for a HPSAHP in the present study has shown that COP of the hybrid-mode operation can reach 3.32, an increase of 28.7% as compared to the heat-pump mode COP (2.58).     

Performance of an inexpensive underground shallow solar pond water heater

In this communication, an inexpensive underground shallow solar pond (SSP) water heater has been suggested, and its performance has also been studied in detail. An explicit analytical expression for temperature has been obtained. The effect of various parameters, viz duration of covering the system by insulation, duration of flow rate, flow rate, insulation thickness, water mass, etc. have also been discussed. Numerical calculations have been made for a typical cold day.     

A solar water heater with a built-in latent heat storage

In this paper, we have investigated the performance of a novel built-in storage type water heater containing a layer of PCM-filled capsules at the bottom. The PCM layer is introduced with a view of getting hot water during off-sunshine hours. The moving solid-liquid boundary layer problem for the PCM material is simplified to a stationary boundary layer problem, and the effect of latent heat is included in the specific heat by replacing the semi-melted PCM by a fictitious solid. The performance of the water heater is then predicted analytically for two depths of PCM and for different flow rates, both constant and intermittent. The case of sudden withdrawal of water over very short periods is also studied.     

Capital cost and economic viability of thermosyphonic solar water heaters manufactured from alternate materials in India

Many companies in India manufacture solar water heaters but these are not becoming popular in the domestic sector because of their high cost. The Ministry of Non-Conventional Energy Sources (MNES), New Delhi is recommending flat-plate collectors with copper (Cu) risers, headers and plate. Therefore, their cost is high. Long term studies have been carried out at the Central Arid Zone Research Institute, Jodhpur, to reduce the cost by replacing copper tubes with galvanised steel (G.S.) tube and copper plate with aluminium (Al) plate. The aluminium plate is wrapped over the G.S. tube by a special wire wound technique so that good contact of plate with risers and headers has been maintained. In this paper performance and testing of solar water heaters having G.S.–Al fin, Cu–Al fin and Cu–Cu fin in flat-plate collectors have been compared. It has been found that performance of all the three heaters is almost similar. The heater can provide 100 litres of hot water at an average temperature 62.0°C at 4 pm that can be retained to 50.4°C when average tap water temperature was 23.9°C. The efficiency of the heater is 51.9%. The cost of the heater with G.S.–Al collector is only Rs. 8,000.00 while it is Rs. 10,250.00 for solar water heaters with Cu–Cu collectors. The payback period of a solar water heater with G.S.–Al collector has been worked out by considering 10% compound annual interest, 5% maintenance cost, 5%, inflation in fuel prices and maintenance cost. The payback period varies between 2.92 years to 4.53 years depending upon which fuel it replaces. The payback periods are in increasing order with respect to fuels: electricity, firewood, LPG, charcoal, and kerosene.