Conventional Solar Water Heater Research Articles

Experimental analysis of the performance of a solar flat plate water heater with and without internal fins

Generally increasing, an increase in the surface area will increase the heat transfer capability of a solar collector and possibly its efficiency. Conventional solar water heaters have longitudinal fins attached externally to the collector tubes for reaping the benefits of enhanced heat transfer. Attempts have been made towards providing internal fins (spirally grooved copper tubes), in addition to the existing external fins for analysing its influence on efficiency and outlet temperature. Two identical solar water heaters with a capacity of 25 L per day were designed and fabricated, one with a collector with plain (unfinned) internals and another with internal grooving (finned tube). The paper details the temperature profile observed in the two collectors, variation of thermo-siphon mechanism and change in efficiency of the solar water heaters with respect to time. It has been observed that providing internal fins had led to an increase in efficiency of about 4.5% as compared to conventional plain tubes.

Performance Analysis of Solar Water Heater at Possible Flow Rates with and Without Phase Change Material

To store excess solar energy from the sun, in this project we pro-vide phase change materials (PCM) at the bottom of the absorber plate.Experiments were conducted in the cascaded solar water heater withand without phase change materials at different flow rates. During thesun-shine hours, the phase change material (PCM) absorbs latent heatof solar energy and stores the same energy up to its melting point. Simi-larly during off-sunshine hours, the phase change material releases theenergy, which is used to heat the water. The set up can result a higherefficiency of the solar collector system. In this work, the paraffin waxhas been selected as a phase change material due to its low cost, easilyavailability and considerable thermo-physical properties. The PCM unitstores the heat during the sun-shine hours and supplies hot water dur -ing the night and overcast periods. An attempt was made to producehot water even after sun-shine hours every day. The performance of thisPCM based thermal energy storage system is compared with conven -tional latent heat storage system and the conclusions drawn from themare presented. The conventional solar water heater gives better efficiencyduring day time because of the energy absorbed by phase change mate-rial. Thus a solar water heater integrated with phase change materialunit gives little better efficiency during off sun-shine hours due to thepresence of thermal energy storage system.

Performance Evaluation of a low cost integrated collector storage solar water heater with independent plane reflectors

High initial cost is one of the reasons why consumers think twice before investing on the conventional solar water heating systems, especially in low income countries. Integrated collector storage systems are available at a lesser cost, but with a penalty of decreased efficiency. In this paper, yet another attempt to reduce cost of solar water heating system has been made by using independent plane reflectors along with an insulated storage tank provided with a heat absorbing aperture. With no tracking arrangement, this system uses only the intense beam radiation available from 9:00 AM to 3:00 PM with a concentration factor of 10. A theoretical study was conducted using commercial computational fluid dynamics software which was followed by an experimental validation of the results. The theoretical results were in agreement with the experimental results. The efficiency of this system was less than collector storage systems reported in the literature by about 10-15%. Maximum average tank temperature of 350 K and efficiency of 0.61 was obtained. Overall loss coefficient was identical with that of existing integrated collector storage systems. DOI: http://dx.doi.org/10.3329/bjsir.v49i3.22128 Bangladesh J. Sci. Ind. Res. 49(3), 147-154, 2014

Performance Analysis of Solar Water Heater in Multipurpose Solar Heating System

Of all the renewable sources of energy available, solar thermal energy is the most abundant one and is available in both direct as well as indirect forms. In order to increase the thermal performance of solar collectors, the multipurpose solar collectors were investigated experimentally by the storage tank of the conventional solar water collector is modified as riser tubes and header. It is fitted in the bottom of the solar air heater as an absorber in the normal air heater. The thermal performance of thermosyphon flat plate solar water heater was investigated on both summer and winter seasons. The maximum daily average of 72.05%, 0.0316 kg/sm2 and 0.873 m/s were recorded for the relative humidity, mass flow rate and wind speed at summer season respectively. Corresponding figure at for winter was 19.5 % 0.0295 kg/sm2 and 0.722 m/s respectively. A minimum daily average of 11.23% and 0.384 m/s for the relative humidity and wind speed respectively. These results show that the mass flow rate obtained was a function of solar radiation and relative humidity. The less humid the ambient air becomes, the higher the heat gained by the system hence higher water flow rate. The maximum value of relative humidity obtained is due to low solar radiation on winter season. The heat removal factor (FR) and collector efficiency factor (Fo) were found to be higher for Multipurpose solar water heater as compared to conventional solar water heaters for summer as well as winter season. These factors for Multipurpose solar water heater were more during summer and winter.

Performance study on evacuated tube solar collector using therminol D-12 as heat transfer fluid coupled with parabolic trough

Fossil fuels and electrical energy are widely used for instant hot water generation in rural and urban areas. Also, conventional solar water heaters do not support instant hot water generation because of various problems. A new system with evacuated tube collector using synthetic oil as heat transfer fluid coupled with parabolic trough is developed and studied experimentally for instant hot water generation in the presence of low solar irradiance. Among the different grades of therminol, therminol D-12 is chosen for the study because of its thermal stability. Parabolic trough is coupled to evacuated tube to enhance the flow as well as heating characteristics of therminol. Heating efficiency and temperature characteristics are determined for the newly developed system under low solar irradiance conditions. Instant hot water can be produced by the new system at a temperature of 60°C in the presence of low solar radiation. This newly developed system has the ability to check the fossil fuel consumption and electrical energy consumption for instant hot water generation in household applications. The stability of the heat transfer fluid is also ensured by repeated experiments.

Experimental Study With Analytical Validation of Thermally Driven Flow in Risers of Solar Water Heaters Under Varying Scale Thickness and Heat Flux

This paper investigates the deterioration in the performance of thermosiphon flat plate solar water heaters (SWH) with water side scaling. The study presents the analytical and experimental variation of mass flow rate of water with scale thickness in risers of conventional solar flat plate water heater for different electrical power inputs (covering the full range of solar incident radiation up to 1 kW/m2). This information is extended further to determine the drop in efficiency characteristics represented by the Hottel–Whillier–Bliss (H–W–B) constants for full–fledged SWH. To simulate scaling in risers in the absorber plate of a SWH, an artificial method of coating has been used to create single pipe riser of different uniform scale thicknesses. Four such risers are created with scale thickness of 0 mm, 0.7 mm, 1.7 mm, 2.7 mm, and 3.7 mm. The observed drop in mass flow rate through the range of risers between 0 mm and 3.7 mm scale thickness is 58.5% for the thermal input power (supplied through electric heating) of 129.5 W (corresponding to a solar incident radiation of 980 W/m2). In comparison, the analytical results show a corresponding drop of 70.12%. A comparison of the coated riser with a cut tube of an actually scaled riser indicates excellent matching of thermal conductivity. The divergence between experimental and analytical mass flow rate in the case of a riser of the highest scale thickness, viz., 3.7 mm, is the lowest because of increased pressure gain in the flow region together with higher temperature than predicted by the general equation. The experimental data of various energy parameters from the single tube scaled riser studies are matching with analytical values for the different input electrical power levels (corresponding to the different solar radiation levels). As identical conditions are used in the experimental analysis, the results for risers of various scale thicknesses and electrical power inputs are applicable to corresponding full–fledged SWH.

Results of the development of a solar accumulation-type water heater made of polymer and composite materials

Results of the development and preliminary tests of a solar water heater completely made of polymer and composite materials are presented. The combination of a solar collector and storage tank into a united construction in combination with the application of modern fabrication technologies of bulk units made of polymer materials makes it possible to considerably decrease the expenses per area unit of the receiving surface of the heater with maintaining high-energy conversion characteristics of the solar energy into low-potential heat. This increases the competitiveness of such installations in comparison with conventional solar water heaters with separate solar collectors and a storage tank.

Experimental assessment of two-phase bubble pump for solar water heating

The research goal is to develop a new solar water heater system (SWHS) that uses a solar bubble pump instead of an electric pump. The pump is powered by the steam produced from an evacuated tube collector. Therefore, heat could be transferred downward from the collector to a hot water storage tank. The designed system consists of two sets of heat-pipe evacuated tube collectors, a solar bubble pump installed at an upper level and a water storage tank with a heat exchanger at a lower level. Discharge heads of 1 and 5 m were tested. The bubble pump could operate at the collector temperature of about 90–100 °C and vapor gage pressure of 80–90 kPa. It is found that water circulation within the SWHS depends on the incident solar intensity and system discharge head. Experimental investigations are conducted to obtain the system thermal efficiencies from the hourly, daily and long-term performance tests. The thermal performance of the proposed system is compared with conventional solar water heaters. The results show that the proposed system achieves system characteristic efficiency of 10% higher than that of the conventional systems using electric pump if taking the consumption of electric power into account. And the former is a zero carbon system.

Performance evaluation and comparison of a novel “retro-fit” heat exchanger and a conventional solar water heater with a single coiled heat exchanger

The performances of solar water heating systems have improved steadily over recent years due to improved component quality and design. Solar water heating systems in Northern Maritime climates, however, are still not viable economically. In order to make a significant impact on the domestic hot water heating market, solar water heaters must be innovative, cost-effective, and adaptable for retro-fit installation. This paper investigates experimentally the performance of a novel heat exchanger (the “Solasyphon”) designed and developed for external connection to an existing traditional single-coil hot water cylinder. The connection of the novel heat exchanger to an existing system reduces the cost of installation as it avoids the need to replace the existing single-coil hot water cylinder with a twin-coil system. However, the connection of this Solasyphon to a solar water heating system has negative effects on heat losses especially at higher temperatures based on the size of the solar collector. The experimentation was carried out under outdoor and indoor control operating conditions. This paper presents the monitored performance of the Solasyphon compared with that of a conventional solar water heater with a coiled heat exchanger and the negative effects regarding the heat losses resulting from the small size of the solar collector especially at high inlet temperatures (greater than 70 °C).

Experimental and theoretical study of the efficiency of a dual-function solar collector

A design of solar collector that is able to provide both hot water and hot air has been proposed to increase annual thermal conversion ratio of solar energy. By modifying the conventional flat-plate solar water heater, the collector with L-shape fins can also function as a double-flow solar air heater. Experiments have been conducted to investigate the dual functions of the collector. It is shown that the thermal efficiency of the collector reached 50% in water heating, and varied from 41% to 55% in air heating depending on the ambient condition and flow rate. Mathematical model has been presented for the collector working in air heating mode. The theoretical results are in good agreement with the experiment results. Theoretical results show that the air flow rate is a dominant factor to determine the efficiency. The enhancement of the L-shape fins on the performance of the collector in air heating is also proved from the theoretic results.

Thermal performance analysis and economic evaluation of roof-integrated solar concrete collector

This paper examines the thermal performance of a roof-integrated solar concrete collector for reducing heat gain to a house and providing domestic hot water. The solar concrete collector is made of PVC pipes embedded in deck slab or concrete roof. No glazing on the top of the solar concrete collector or insulation at the back has been used as in conventional solar water heaters. To compare the energy saving, two test rooms of 2.3m width, 2.5m length and 2.5m height were built. In the first room, the reinforced cement concrete (R.C.C.) slab was used as deck slab whereas the second room was equipped with a cement concrete solar collector. The experimental results showed that the cement concrete solar collector is extremely interesting as it can produce up to 40l of hot water per day at water temperatures ranging from 40 to 50°C. A mathematical model based on the conservation equations of energy is developed to predict the performance of the cement concrete solar collector. There is reasonable agreement from the comparison between measured data and predicted results. The economic analysis indicates that the payback period is rather fast.

Experimental characterisation and technical feasibility of a closed two-phase vs a conventional solar water heating thermosyphon

The present paper deals with Domestic Solar Water Heating Systems (DSWHS) for sanitary purposes. A Phase Change System (PCS) was designed and built. The PCS consists of a solar collector – thermo tank set that use a working fluid to indirectly transfer heat to the water. In some regions of Mexico, the high concentrations of minerals in the water accumulate to obstruct the pipes, preventing the solar collector from working. Using a suitable working fluid (different from water) avoids this problem, as well as freezing, corrosion, fouling and scaling, usually presented in conventional DSWHS. A conventional DSWHS with the same dimensions and geometry than the PCS was installed to compare their performance in simultaneous tests. Tests in the PCS were performed using three working fluids: R134a, R410A and acetone, under the actual field conditions of Temixco, Mexico. The technical feasibility of the three working fluids was investigated. Experimental data indicate that the PCS, loaded with either R134a or R410A, has equivalent performance than the DSWHS. However, high pressures and some difficulties to load the working fluid have to be dealt with. Lower performance was shown using acetone, but with the advantages of an easy load and low working pressure. ► A phase change solar system to heat water is compared to a conventional system. ► The stages of operation of the phase change system were recognised and explained. ► A phase change system prevents corrosion, fouling and freezing, increasing lifetime. ► Efficiencies equivalent to the conventional system are reached.

Theoretical and experimental investigations of a two-phase thermosyphon solar water heater

This article experimentally and theoretically investigates a two-phase thermosyphon solar water heater. The performance of this innovative solar water heater at different solar radiation intensities and tilt angles are experimentally discussed. The results show the best charge efficiency of the system is 82%, which is higher than the conventional solar water heaters. The theoretical model is also developed using the thermal resistance-capacitor method. The simulation predictions agree well with the experimental data within an average error deviation of ±6%. Two methods for improving the performance of this heater, double fin tubes and nano particle, are proposed. The results show that charge efficiencies can increase 3% and 4%, respectively, according to the theoretical model.

Optimum configuration of compound parabolic concentrator (CPC) solar water heater types for dwellings situated in the northern maritime climate

SYNOPSIS For northern maritime climates with a high diffuse component of solar radiation, non-imaging CPC solar collectors with concentration ratios of up to 2 can be used to concentrate direct as well as diffuse incident solar radiation without tracking. Due to the concentrated solar flux incident on the absorber, these systems can produce temperatures in excess of those produced by conventional solar water heaters, thus reducing the auxiliary energy requirement. Additionally, a smaller absorber area is required, reducing the cost of the solar collector and making these systems more economically attractive. Two CPC solar collectors with an identical cavity profile were fabricated, one utilising a heat-pipe absorber and the other a simple direct flow absorber. Both collectors were tested under steady state operating conditions at inlet temperatures of 20°C, 30°C 40°C and 50°C, to simulate the conditions experienced by a typical domestic solar water heater. It was found that the direct flow CPC performed better at higher solar intensities and lower inlet temperatures, as the heat-pipe CPC had a much higher absorber plate temperature. Thus, for domestic applications, simple direct flow CPC systems would be preferred due to their higher efficiency and lower cost.

Experimental investigation on the use of water-phase change material storage in conventional solar water heating systems

This paper presents an experimental investigation of the performance of water-phase change material (PCM) storage for use with conventional solar water heating systems. Paraffin wax contained in small cylindrical aluminum containers is used as the PCM. The containers are packed in a commercially available, cylindrical hot water storage tank on two levels. The PCM storage advantage is firstly demonstrated under controlled energy input experiments with the aid of an electrical heater on an isolated storage tank, with and without the PCM containers. It was found that the use of the suggested configuration can result in a 13–14 °C advantage in the stored hot water temperature over extended periods of time. The storage performance was also investigated when connected to flat plate collectors in a closed-loop system with conventional natural circulation. Over a test period of 24 h, the stored water temperature remained at least 30 °C higher than the ambient temperature. The use of short periods of forced circulation was found to have minimum effect on the performance of the system. Finally, the recovery effect and the storage performance of the PCM was analyzed under open-loop operation patterns, structured to simulate daily use patterns.

Energy and cost analysis of a solar-hydrogen combined heat and power system for remote power supply using a computer simulation

A simulation program, based on Visual Pascal, for sizing and techno-economic analysis of the performance of solar-hydrogen combined heat and power systems for remote applications is described. The accuracy of the submodels is checked by comparing the real performances of the system’s components obtained from experimental measurements with model outputs. The use of the heat generated by the PEM fuel cell, and any unused excess hydrogen, is investigated for hot water production or space heating while the solar-hydrogen system is supplying electricity. A 5 kWh daily demand profile and the solar radiation profile of Melbourne have been used in a case study to investigate the typical techno-economic characteristics of the system to supply a remote household. The simulation shows that by harnessing both thermal load and excess hydrogen it is possible to increase the average yearly energy efficiency of the fuel cell in the solar-hydrogen system from just below 40% up to about 80% in both heat and power generation (based on the high heating value of hydrogen). The fuel cell in the system is conventionally sized to meet the peak of the demand profile. However, an economic optimisation analysis illustrates that installing a larger fuel cell could lead to up to a 15% reduction in the unit cost of the electricity to an average of just below 90 c/kWh over the assessment period of 30 years. Further, for an economically optimal size of the fuel cell, nearly a half the yearly energy demand for hot water of the remote household could be supplied by heat recovery from the fuel cell and utilising unused hydrogen in the exit stream. Such a system could then complement a conventional solar water heating system by providing the boosting energy (usually in the order of 40% of the total) normally obtained from gas or electricity.

Long-term thermal performance of a two-phase thermosyphon solar water heater

This article investigates experimentally the long-term thermal performance of a two-phase thermosyphon solar water heater and compares the results with the conventional systems. Experimental investigations are conducted to obtain the system thermal efficiencies from the hourly, daily and long-term performance tests. Different heat transfer mechanisms, including natural convection, geyser boiling, nucleate boiling and film-wise condensation, are observed in the two-phase thermosyphon solar water heater while solar radiation varies. The thermal performance of the proposed system is compared with that of four conventional solar water heaters. Results show that the proposed system achieves system characteristic efficiency 18% higher than that of the conventional systems by reducing heat loss for the two-phase thermosyphon solar water heater.

Potential application of solar thermal systems for hot water production in Hong Kong

This paper presents the evaluation results of conventional solar water heater (SWH) systems and solar assisted heat pump (SAHP) systems for hot water production in Hong Kong. An economic comparison and global warming impact analysis are conducted among the two kinds of solar thermal systems and traditional water heating systems (i.e. electric water heaters and towngas water heaters). The economic comparison results show that solar thermal systems have greater economic benefits than traditional water heating systems. In addition, conventional SWH systems are comparable with the SAHP systems when solar fractions are above 50%. Besides, analysis on the sensitivity of the total equivalent warming impact (TEWI) indicates that the towngas boosted SWH system has the greatest potential in greenhouse gas emission reduction with various solar collector areas and the electricity boosted SWH system has the comparative TEWI with the SAHP systems if its solar fraction is above 50%. As for SAHP systems, the solar assisted air source heat pump (SA-ASHP) system has the least global warming impact. Based on all investigation results, suggestions are given on the selection of solar thermal systems for applications in Hong Kong.

Broadband communication enables sustainable energy services

Australias electricity supply infrastructure requires investments exceeding $100b over the next 25 years to maintain quality of service to domestic users. Being careful to distinguish energy service needs from electricity delivery, the case is made for distributed energy services which offer improved sustainability outcomes to the traditional monolithic generation model. A key enabling technology for commercial success of the proposed paradigm is a broadband communication infrastructure. Broadband is essential in meeting the cost reduction and performance targets that would allow a distributed energy service model to succeed. Using broadband, a large number of novel business opportunities arise. A case study on solar water heaters is presented showing that a broadband enabled smart controller can realise 20% greenhouse gas savings for a conventional solar water heater and 75% savings for an electrical water heater. Copyright 2007 Mike Dennis and Haley M Jones. No part of this article may be reproduced by any means without the written consent of the publisher.

Temperature distributions in trapezoidal built in storage solar water heaters with/without phase change materials

Built in storage solar water heaters (BSSWHs) have been recognized for their more compact constructions and faster solar gain than conventional solar water heaters, however, their water temperatures quickly go down during the cooling period. A trapezoidal BSSWH without PCM storage unit was used as the control heater (reference) to investigate the effect of two differently configured PCM storage units on the temperature distributions in water tanks. In the first design, myristic acid was filled into the PCM storage tank, which also served as an absorbing plate. In the second design, lauric acid was filled into the PCM storage tank, which also served as a baffle plate. The water temperature changes were followed by five thermocouples placed evenly and longitudinally into each of the three BSSWHs. The effects of the PCMs on the water temperature distributions depended on the configuration of the PCM storage unit and the longitudinal position in the water tanks. The use of lauric acid lowered the values of the peak temperatures by 15% compared to the control heater at the upper portion of the water tanks because of the low melting temperature of lauric acid, but it did not have any consistent effect on the retention of the water temperatures during the cooling period. The ability of the myristic acid storage unit to retain the water temperatures got more remarkable, especially at the middle portion of the water tank. The myristic acid storage increased the dip temperatures by approximately 8.8% compared to the control heater. In conclusion, lauric acid storage can be used to stabilize the water temperature during the day time, while the myristic acid storage unit can be used as a thermal barrier against heat loss during the night time because of its relatively high melting temperature and low heat conduction coefficient in its solid phase. The experimental results have also indicated that the thermal characteristics of the PCM and the configuration of the PCM storage unit can result in advantageous control of the water temperature rise and drop during both day and night time.