Solar Domestic Water Heating Systems Research Articles

Thermal analysis of a cascaded latent thermal storage tank in a solar domestic water heating system

AbstractTo enhance the thermal characteristics of a solar collector storage system, this study investigates the performance of a rectangular thermal energy storage (TES) tank by incorporating cascade phase change materials (cascade‐PCMs). Three different commercially available PCMs (RT44HC, RT54HC, and RT62HC) with distinct melting temperatures are employed. These cascade‐PCMs are utilized as slabs in vertical rectangular modules, which are integrated into the water TES tank. The heat transfer fluid (HTF) in the flat‐plate solar collector captures solar energy and transfers it to the TES tank, where it is stored as latent thermal energy. A two‐dimensional (2D) numerical model, utilizing the enthalpy‐porosity approach and conservation equations, is developed to analyze the melting and heat transfer processes within the TES tank. The model is validated against previous experimental and numerical data. Performance evaluation of the cascade‐PCMs tank is conducted during a 9‐h charging period (from 8:00 am to 5:00 pm) under Marrakesh weather conditions in Morocco. An optimization study is carried out to determine the optimal height of each cascade‐PCM. The results suggest that an optimal design with heights of 23, 16, and 11 cm for RT44HC, RT54HC, and RT62HC respectively, offers improved melting and storage quality. The thermal characteristics of the TES tank incorporating cascade‐PCMs are compared to those of a TES tank filled with a single phase change material (single‐PCM) during the charging period. The findings indicate that the cascade‐PCMs achieve complete melting, while the single‐PCM only reaches a melting fraction of 0.903 at the end of the charging process. Furthermore, the optimal configuration of the cascade‐PCMs storage tank exhibits slightly higher sensible and latent thermal energy storage capacity compared to the single‐PCM tank. The combination of the solar collector with the cascade‐PCMs storage tank results in a 3.47% higher average collection efficiency when compared to the single‐PCM tank.

Türkiye'de Ankara ili için düz plaka kollektör güneş sıcak su sisteminin TRNSYS yazılımı ile incelenmesi

A domestic solar water heating system using a flat plate collector is modeled for the domestic hot water requirement of a residential unit in Ankara, Turkey. The necessary design parameters were determined and the analysis was carried out using the TRNSYS simulation program. In the modeled system, the domestic water temperature was determined as 55 °C and water withdrawals were carried out at different flow rates during the day according to the usage intensity. The water withdrawal rates were determined as 80 kg/h between 07.00-09.00, 100 kg/h between 12.00-13.00 and 50 kg/h between 17.00-22.00. According to the results obtained, the designed system was able to meet the hot water need in summer and winter months by using solar energy through auxiliary heaters. While the collector efficiency reached its highest value with 40% in September, it reached the lowest efficiency value with 8% in December.

Optimization of collector area and storage volume in domestic solar water heating systems with on–off control—A thermal energy analysis based on a pre-specified system performance

Numerical simulations of solar water heating systems using on–off control were performed for four locations in the Portuguese territory, two collector types, and a wide range of parameters. Two main design parameters were considered: the collector area and the storage volume. An innovative technique was used to investigate the relationship between system performance and system parameters: a pre-specified annual solar fraction is selected and the optimal parameters needed to achieve this solar fraction are then computed. The optimum collector area is almost always higher for a double-glazed than for a single-glazed collector, suggesting that in Portugal, the single-glazed type is more effective for most solar water heating applications. This fact is more significant for lower solar fractions and warmer climates. A small increase in the optimum collector area leads to a very strong decrease in the optimum storage volume (an area increase of 1% leads to a volume decrease of 27%). Collector flow rate and storage volume increments result in lower collector areas. However, high flow rates lead to high pumping losses and lower collector efficiencies, and when the storage tank losses are significant, higher tank sizes may lead to higher collector areas. The solar fraction has a very strong impact on the collector area and storage volume (when the solar fraction increases from 0.5 to 0.99, the optimum collector area and storage volume increase about 17 and 56 times, respectively).

Thermal energy storage properties, thermal conductivity, chemical/and thermal reliability of three different organic phase change materials doped with hexagonal boron nitride

Myristic acid (MA), Lauric Acid (LA) and Polyethylene Glycol (PEG) are promising organic Phase Change Materials (PCMs) for Thermal Energy Storage (TES). However, low thermal conductivity (TC) negatively affects their heat transfer efficiency during the heat storage/release periods in TES systems. In this regard, hexagonal Boron Nitride (h-BN) was chosen as a filler for TC enhancement. The present study targets to improve the TC of MA, LA and PEG by adding h-BN nanoparticle at different weight amounts, 0.5, 1.0, 1.5 and 2 %, along with a systematic examination of other chemical and thermal properties. Scanning electron microscopy (SEM)/Energy dispersive X-Ray spectroscopy (EDX), Fourier-transformed infrared (FTIR) and X-Ray diffraction (XRD) analysis results demonstrated that the dispersion of h-BN in the PCMs was fairly homogeneous and had no damaging influence on their chemical/crystalline structures. Differential scanning calorimetry (DSC) results indicated that the addition of h-BN (2wt%) marginally shifted their phase change temperatures and slightly decreased the LHS capacities compared to pure PCMs. The h-BN/PCM composites exhibited good chemical stability and thermal reliability after 500 heating/cooling cycles. The addition of h-BN (2 wt%) resulted in 1.40, 1.27 and 1.30 times-enhancement in TC values of MA, LA and PEG, respectively. This improvement was also displayed in the T-History curves. All findings revealed that 2 wt% h-BN addition could be enough for satisfactory TC enhancement without affecting the LHS properties of the selected PCMs significantly. Thus, h-BN enhanced PCMs could be used for thermal management of electronic equipment, solar collectors, solar PV systems and domestic water heating systems etc.

Energy, exergy, environmental impact, and economic analyses of evacuated tube compound parabolic concentrator–powered solar thermal domestic water heating system

In the reported study, a dynamic analytical model is developed to propose the energy, exergy, environmental impact, and economic analyses of the water heating system at Jaipur (India) with an evacuated tube compound parabolic concentrator field of a total area of 81 m2. Consequently, the model is used to perform parametric studies to report the effect of operating and meteorological parameters on the productivity and performance of the system. Moreover, the system's performance, environmental impact, and economic aspects have been investigated and compared under different meteorological conditions at four different Rajasthan (India) locations using TMY2 weather data files. Results clarified that Jodhpur receives the highest solar radiation intensity from these four locations. The model results were validated with the experimental data, and a good agreement has prevailed. Consequently, the results indicate the highest annual energy and exergy gain for Jodhpur with 79.72 MWh and 9.311 MWh, respectively, followed by Jaisalmer, Barmer, and Jaipur. The economic analysis results clarified that the simple payback period ranged from 4.5 to 4.75 years and the discounted payback period ranged from 6.6 to 7 years based on a 6% discount rate. At the same time, the levelized cost of heating for the given system is around 0.023 $/kWh which is very economical closest to that of CNG as a fuel which costs around 0.059 $/kWh. The internal rate of return is reported to be 16.76, 16.82, 16.77, and 16.75% for Barmer, Jodhpur, Jaipur, and Jaisalmer, respectively, and savings of 74.4, 78.1, 75.4, and 73.8 tonnes of CO2 emission to the environment.

Effect of simultaneous & consecutive melting/solidification of phase change material on domestic solar water heating system

The foremost challenges in heat pipe ETC are low heat transfer rate between absorber tube & heat pipe, overheating of heat pipes, and its inability to supply hot water during off-pick hours. The incorporation of latent heat storage material (LHSM) between absorber tube and heat pipe is the efficient solution to overcome these challenges. Also, along with energy and exergy analysis, economic & environmental analysis to be done to ensure whether utilization of LHSM with ETC system is viable for the commercial utility. Thereby, in this study, energy, exergy, economic & environmental analysis of stearic acid integrated ETC for two different modes (ETC/Mode-I & II) have been done and distinctly in comparison to the reference system. The daily energy efficiency of ETC/SA for ETC/Mode-I and ETC/Mode-II improved by 37–45 and 65–81% respectively, whereas, improvement in exergy efficiency was observed by 21–29 and 57–73% respectively. The positive value of NPV shows that investment in ETC/SA will be highly profitable. The ETC/SA mitigated CO2 emission in the range of 26–37 and 8–12 tCO2/lifetime based on energy and exergy approach respectively. Thus, ETC/SA working for ETC/Mode-II system was found to be more economical, highly energetic & exergetic efficient, and more environmentally friendly.

Towards Strategic Plan for Wide Spreading of Solar Water Heaters in Libya

Solar water heaters have been in use for decades in many countries in the world that have less favorable climatic conditions for solar energy as compared with Libya. However, still there is no usage of such technologies in the country. This could be attributed to many factors including, among others, lack of clear policy and/or serious plans to establish such technology, cheap prices of conventional energy, and lack of environmental awareness. The Center for Solar Energy Research and Studies (CSERS) of Libya has developed an excellent research and development program on a national scale for domestic solar water heating systems. The national program started in the early 1990’s aiming at increasing publicawareness. The program utilizes different ways such as pilot projects, studies, workshops, and reports to convince people and decision-makers of Libya about this subject and its benefits.This paper attempts to suggest a strategic plan (win-win situation between government and people) for encouraging and helping widespread (replacement) of solar water heaters nationwide based on economic and environmental pointers in favour of the replacement. Th suggested strategic plan is to provide 25% of existing houses in 2013 with solar water heating systems by 2022, with a governmental subsidy of up to 65% of the system cost. The study has shown that every L.D. paid by the government will return with at least 2 L.D. after 10 years of investment without considering the money saved from the fuel savings, powerplant installations to fulfill the demand, and the environmental benefits.

Experimental and numerical analysis of thermal performance of shape stabilized PCM in a solar thermal collector

A typical solar domestic water heating system suffers from low energy efficiency due to multiple heat transfer process among components, i.e., the solar thermal collector and the thermal energy storage. In this work, a compact design of storage-integrated solar thermal collector and its compatible phase change material (PCM) storage material were explored. The salt hydrate based composite PCM, the sodium acetate trihydrate (SAT), was used to create a shape stabilized PCM (ssPCMs) for a feasible PCM by its low leakage and high thermal conductivity. The developed ssPCMs has been tested experimentally and a numerical model has been developed to obtain the effective thermal property of the developed ssPCMs by comparing the predicted results with the measurements. Furthermore, the model has been used to study the (dis)charging behavior of PCM in a storage-integrated solar thermal collector which is composed of an evacuated tube and a double spiral coils heat exchanger. A geometrical optimization has been performed to achieve 2.6 times longer of discharging period with a minimum outlet temperature of 55 °C. Moreover, the circulating water is found useful in increasing the PCM charging rate with 9% by transferring the heat from the surface to the center of tube.

MgO-Nano Coating Consequences on the Performance of Domestic Solar Water Heating System

Nowadays, government around the world confining to usage of fossil fuels as they are emitting more harmful emissions to the nature. Thereby, some novel approaches which curbs the fossil fuel addiction and environmental degradation plays an imperative role in present days. The technologies which helps to effective utilization of solar energy is too urge. In line with this an effort is made to use solar energy effectively by doing some changes in solar water heating system. In this current study Magnesium Oxide (MgO) nano particles are prepared in house and characterized. Later, study unfolds the effect of reflective coatings on the performance of solar water heating system. From the learn, it is cleared that solar water heating system with MgO nano coated reflective plate has shown the better performance (heat flux & Reynolds no.) when compared to without reflective plate, with reflective plate and reflective plate with micro coatings.

Automatic Testing Design for Thermal Performance of Domestic Solar Water Heating Systems Based on PLC

This paper mainly introduces the method of using PLC to realize the automatic test for the thermal performance of the domestic solar water heating systems, including 4 functional modules as automatic water temperature control, automatic water supply control, automatic circulation control, and automatic data collection control. Through verification, it can meet the test requirements of the standard GB/T18708-2002 “Test Methods for Thermal Performance of Domestic Solar Water Heating Systems”.

Energetic, economic and environmental analysis of domestic solar water heating systems under the African continent

Given the abundance of solar irradiation in Africa, different types of Solar Water Heating technologies can offer practical and reasonable solutions that are valuable for African people and their environment. However, these technologies' impacts were not quantified, and lack of studies could be in part attributed to the weak implementation of solar water heating systems on most countries in Africa. The aim of this paper is first, a model was developed and validated to investigate and analyze the energy performances of the two most domestic used technologies in the African continent: the flat plate collectors and the evacuated tube collectors. Next, the economic and environmental aspects of these systems are also presented. The study was carried out for 43 countries divided in 5 regions: North Africa, West Africa, Central Africa, East Africa and Southern Africa. The energy analysis, in terms of solar fraction, shows that the solar production of domestic hot water varies between 25 and 88% for the evacuated tube and between 10 and 60% for the flat plat collector and this according to the 5 regions mentioned above. Based on the Net present worth, the Benefit–Cost Ratio and the Discounted payback period, the economic analysis shows that these two technologies are beneficial for 16 of the 43 countries studied. That is due to the abundance of other energy resources in the remaining countries.

Analysis of Exergy of an Experimental Domestic Scale Solar Water Heating System Situated in Owerri

Analysis of Exergy of an Experimental Domestic Scale Solar Water Heating System Situated in Owerri

Evaluation of Optical Transmissivity of Transparent Materials on the Performance of Solar Flat Plate Collectors

Abstract The energy gain of domestic solar water heating systems is determined by solar to thermal energy conversion and glazing optical efficiency. For this study, solar transmission properties of different transparent glazing materials such as acrylic, low-iron, medium-iron, and high-iron glasses were measured. The collector thermal efficiency under natural convection mode was compared for different transparent covers determined by numerical simulation using the Hottel–Whillier–Bliss equation. The low-iron glass (LiG-12 mm) has 16.3% and 20% higher thermal efficiency than medium- (MiG-12 mm) and high-iron glasses (HiG-12 mm), respectively, for a peak summer day. The effect of glass thickness on thermal performance is noteworthy in glasses than in acrylic glass sheets. Low-iron content glass with 6 mm thickness has the highest thermal and optical efficiency of 63.2% and 75.65%, respectively, for the collector optimum tilt for Vellore city in Tamil Nadu, India. The results are useful in the selection of glass covers for energy-efficient solar flat plate collectors.

Towards Strategic Plan for Wide Spreading of Solar Water Heaters in Libya

Solar water heaters have been in use for decades in many countries in the world that have less favorable climatic conditions for solar energy as compared with Libya. However, still there is no usage of such technologies in the country. This could be attributed to many factors including, among others, lack of clear policy and/or serious plans to establish such technology, cheap prices of conventional energy, and lack of environmental awareness.The Center for Solar Energy Research and Studies (CSERS) of Libya has developed an excellent research and development program on national scale for domestic solar water heating systems. The national program started in the early 1990’s aiming at increasing public awareness. The program utilizes different ways such as pilot projects, studies, workshops, and reports to convince people and decision- makers of Libya about this subject and its benefits.This paper attempts to suggest a strategic plan (win-win situation between government and people) for encouraging and helping wide spread (replacement) of solar water heaters nationwide based on economic and environmental pointers in favour of the replacement.The suggested strategic plan is to provide 25% of existing houses in 2013 with solar water heating systems by 2022, with governmental subsidy of up to 65% of the system cost. The study has shown that every L.D. paid by the government will return with at least 2 L.D. after 10 years of investment without considering the money saved from the fuel savings, power plant installations to fulfill the demand, and the environmental benefits.

Ign and Control Analysis Of An Automatic Active Domestic Solar Water Heating System

Solar water heating technology is one of the cost-effective ways of heating water in residential and public buildings. This study presents the design technique for an automatic active domestic solar water heating system (ADSWHS) to meet the hot water demand for a residence in Wum (10.43°E, 6.23° N) with a daily hot water demand of 500 litres at 70 o C, using flat plate solar collectors and an arduino microcontroller. The solar data used in this analysis were obtained from Photovoltaic Geographical Information System (PVGIS) and the method used is the active direct roof mounted solar water heating. The system design process consist of evaluating the optimum collector tilt angle, the thermal analysis of the flat plate collector and hot water storage tank and finally modelling a low cost automatic controller for the system using an Arduino in the Proteus software. The optimum annual average solar radiation on the tilted solar collector was obtained following the calculation of the conversion ratios of the direct , diffuse and reflected radiations. At annual time scale, the appropriate tilt angle (I²) that maximizes the collection of solar energy was 11 o and the corresponding optimum average irradiance of 432 W/m 2 wasobtained. The analytical results presented for the performance of the heater indicate that the system operates at an annual thermal efficiency of 55.49%. The control system simulation results indicate that the system uses 4.5kWh and 2.075kWh of energy to run the pump and the auxiliary heater respectively and produces 26.187kWh of energy to heat up the cold water from 25 o C to 70 o C for a single day.

Determination of Heat Losses from the Pipeline in SDHW System during the Continuous Change of the Supply Temperature

In this article, the research object is the solar domestic hot water (SDHW) heating system that has been in operation since 2015 and is located on the campus of the Bialystok University of Technology (Poland). The thermal performance of solar collectors are thoroughly investigated so far. Therefore, special attention was paid to the issue of the heat loss from pipes. The measurements showed that the heat transfer in circulation pipes is quite complex due to continuous fluctuations in water temperature at the supply of this loop. As it turned out, the application of the classical method of energy balancing and the readings from heat meters gave inaccurate results in this case. The main aim of this study was to develop a different approach to solving the problem of determination of heat losses. The method presented in this article is based on computational fluid dynamics (CFD) and measurement results as the input data. The practical result of this study was the development of two relationships for calculating the heat loss from pipes. A separate issue, that is discussed in this paper, concerns the impact of the time intervals used in numerical simulations on the accuracy of calculation results.

Environmental, technical and financial feasibility study of domestic solar water heating system in India

The basic aim of this research work is to investigate the environmental, technical, and financial viability of evacuated tube type solar water heating (SWH) systems at different geographical locations across seven cities of India. The RETScreen SWH project model is used to evaluate the energy production and savings, solar fraction, costs, greenhouse gas (GHG) emission reductions, financial viability and risk factors for the SWH projects at the various locations. The financial viability of the SWH project is demonstrated by the parameters like simple payback period (SPP), equity payback period (EPP), internal rate of return (IRR), and modified internal rate of return (MIRR). The study shows that all sites have more than 60% of solar fractions and the gross GHG emission reduction for 25 years of project life is 739 tCO2. The payback period obtained for seven occupants for the typical household is between 7 and 10 years except for Delhi and Indore. It can be also concluded that at least 50% incentives must be provided by the government to make such installation feasible.

A Comparative Study on the Performances of Flat Plate and Evacuated Tube Collectors Deployable in Domestic Solar Water Heating Systems in Different Climate Areas

Using TRNSYS software, a comparison of the energy performances of flat-plate collectors (FPCs) and evacuated-tube collectors (ETCs) in domestic solar water heating systems located in different climate areas was carried out in order to ascertain solar energy utilization. Investigations were carried out on single FPCs and ETCs and also for strings of four panels connected in series. Tests were conducted using simulations for water as heat transfer fluid with a fixed fluid flow rate and varying the temperature of the collector’s returning fluid. The maximum power peak decreases with the increase in the inlet temperature of the fluid to the collector in the FPC. The maximum outlet temperature of the FPC is higher than the ETC, most of the time. The evacuated-tube collector performs better only in cold climate areas. Simulations suggest that the use of the FPC is strongly discouraged in cold climatic areas due to thermal losses, whereas the ETC works well with reduced dispersion of heat. In warm seasons, on the contrary, the FPC takes advantage of the high environmental temperature which heats the fluid. The maximum yearly outlet temperature and useful power peak predicted in different climatic areas were investigated by varying the temperature of the fluid inlet fed to the two strings of four FPCs and ETCs. In all cases, the outlet temperature is higher in the ETC technology.

Energy, economic and emissions avoided contribution of domestic solar water heating systems for Mexico, Costa Rica and the Democratic Republic of the Congo

In order to determine the energy, economic and emissions avoided contribution of Domestic Solar Water Heating Systems based on the Thermosyphon Principle (DSWHS-TP) in a country, a detailed methodology was designed. The methodology was applied to three countries (Mexico, Costa Rica, and Democratic Republic of the Congo (DRC)) to show its versatility. Results showed that the annual average energy supplied by a DSWHS-TP (150 L with a collector gross area of 2 m2) in Mexico, Costa Rica, and DRC is 5.27, 4.15, and 4.67 GJ, respectively, which represents a solar fraction of 86.6, 98.9, and 76.1%. Consequently, annual money savings of 428, 249, and 614 USD, respectively could be realized. The CO2 avoided emissions are affected by the conventional energy source used to heat water. Costa Rica and DRC have an annual average of CO2 avoided emissions per house of 0.049 and 0.006 tons due to the use of electricity produced largely by renewable energy sources compared to Mexico with 0.55 tons of CO2 per house due to the use of the Liquefied Petroleum Gas. Hence, the methodology presented can be an essential tool to establish the benefits of using DSWHS-TP and the avoided emissions of CO2 in the environment.

Key performance indicators (KPIs): Assessing the process integration of a shell-and-tube latent heat storage unit

In this research, a multi-tube heat exchanger filled with phase change material (PCM) is constructed and investigated experimentally to evaluate its capability to serve as a heat storage unit in solar domestic water heating (SDWH) systems. Several operational conditions comprising the PCM initial temperature and the water discharge flowrates are included in the test as external factors to evaluate the performance of the proposed shell-and-tube latent-heat storage unit (STLHS) as a part of a SDWH system. The STLHS unit is assessed according to several quantitative, qualitative, and economic key performance indicators extracted from the Egyptian plumbing code (EPC). Firstly, the quantitative results show that the proposed STLHS unit increased the water temperature by a range of 7–12 °C and maintained a constant hot water supply for extended periods, 2–3 h. Secondly, from the qualitative point of view, the achieved heating levels are insufficient to fulfill the domestic needs according to the benchmark water temperature established by the EPC. Thirdly, evaluating the STLHS unit on an economic basis shows that the annual fuel saving increases by increasing the unit initial temperature, where the annual fuel consumption savings reach 130 m3 of natural gas. Finally, the acquired techno-economic performance measurements emphasize that the proposed unit has a notable possibility for several design modifications to achieve more improvements in its performance.