Solar Water Heating Research Articles

An experimental investigation of various trickle collector structures to enhance solar water heater efficiency

This study aimed to enhance the efficiency of the solar water heater (SWH) due to the increasing demand of renewable energy. It compared use three different solar collector models, namely Model A (square-shaped polycarbonate), Model B (v-corrugated zinc), and Model C (trapezoidal aluminium) to identify the most cost-effective configuration. The models were subjected to experiments in real operating conditions during the summer season in Indonesia. Various parameters, including solar radiation intensity, wind speed, inlet and outlet temperatures, and flow rate, were measured every 10 min from morning to afternoon. Additionally, the study employed a trickle and one-way flow rate system. The results showed that Model B achieved the highest total efficiency at 50%, followed by Models A and C at 47% and 34%, respectively. The 120 Lph flow rate exhibited better performance in absorbing useful heat energy than the 240 Lph flow rate. Based on these findings, all three models were recommended for the household-scale SWH applications. Model A showed the most promising economic value but had a shorter lifespan due to the tendency of polycarbonate to deform. In contrast, Model B and Model C, using zinc and aluminium, offered longer lifespans.

Deep retrofitting toward net zero energy building in the Mediterranean region: A case study of Albania

Like many other Mediterranean countries, Albania faces unique challenges and opportunities to achieve an efficient and fully decarbonized household sector by applying real energy efficiency measures and numbers toward nearly zero-energy buildings. The study findings showed that nZEB in 2030 can be achieved by combining active and passive energy efficiency measures. Behind the study's state-of-the-art stands a multivariable regression analysis of both electricity consumption and electricity generation executed for three validated consecutive years, 2021, 2022, and 2023, including demand side (electricity bills) and supply side generation provided from a nearby existing onsite PV with an installed capacity of 5.5 kWp. A good mathematical correlation is carried out using Durbin – Watson criteria on statistics using RETScreen software to correlate electricity consumption and generation as a function of weather parameters for the tested household and selected region. The goals to meet the nZEB concept require the insulation of the existing exterior wall and window replacements in compliance with the Energy Performance Methodology on Building and installing rooftop Solar Water Heating (SWH) panels of 3.73 m2 as expostulated in scenario 7. The simulation results show that integrating a rooftop PV system with an installed capacity of 5.5 kWp would provide enough electricity to convert residential buildings into Positive Energy Buildings in 2050 based on the selected dwelling and location (Mediterranean region). At the national level, the proposed model would reduce the national annual electricity import level by 1.64 %, saving annually around €31,021,162 and reducing at least 0.068 MtCO2 per year. Subsidizing passive energy efficiency measures at a rate of 3 % per year coupled with onsite renewable energy sources schemes and other incentivization pathways from the government and other interested parties at a rate of 80 % in the roadmap towards nZEB and PEB is mandatory.

Experimental study of the thermal performance of spiral flow solar water heating system

Experimental study of the thermal performance of spiral flow solar water heating system

Assessing homeowners’ awareness of green technologies in residential housing development: evidence from Ghana

PurposeUsing and promoting green technologies in residential buildings might be a far more practical strategy for developing a sustainable built environment. The primary goal of this study is to examine homeowners' knowledge and awareness of the different green technologies and concepts that can be adopted to improve the quality of their homes.Design/methodology/approachThe study employed a sequential mix technique methodology in order to accomplish its goal. A total of 156 respondents were chosen for a survey within the research areas using a simple random sample approach, while interviewees were chosen using a purposive sampling approach methodology. Descriptive and inferential statistics as well as content analysis were used to analyze the quantitative and qualitative data, respectively.FindingsThe findings indicate that homeowners have moderate knowledge of green technologies. It was also evident that print and electronic media are excellent at capturing and reaching a diverse range of homeowners interested in learning about sustainable development issues. Furthermore, the top three green technologies that most homeowners are aware of are using local materials over imported materials, grey water reclaiming and reuse technology and solar water heating technology. Subsequently, the homeowners in the three communities have differing opinions about the majority (82%) of the green technologies examined.Originality/valueThe findings will serve as a useful guide to assist practitioners and policymakers in implementing appropriate methods to integrate green technologies into housing projects and subsequently encourage their adoption.

The Effect of Radiation Intensity on the Performance of Direct-Expansion Solar PVT Heat Pump Systems

The objective of this study was to investigate the impact of solar radiation intensity on the performance of direct-expansion solar PVT heat pump systems. To this end, an experimental setup was constructed for direct-expansion photovoltaic (PVT) solar heat pump water heating systems and photovoltaic (PV) power generation systems. The system performance and main parameters were analyzed and discussed under different solar radiation intensities. The winter experiments in southern China revealed that the exhaust temperature of the heat pump unit varied considerably under clear conditions, while the back temperature remained stable, fluctuating between approximately −13.5 °C and 24 °C. In contrast, the power generation of PVT panels increased with the increase in radiation intensity, from 78.33 W to 122.68 W, for an increase of 56.6%. Furthermore, the total electricity generation of the PVT panels was higher than that of PV panels, with an increase of 8.7–8.3%. Nevertheless, discrepancies between experimental and theoretical data were observed, particularly under overcast conditions, where the back panel temperature error was pronounced. Additionally, the system exhibited enhanced stability at elevated temperatures in comparable environments, accompanied by an improvement in the system’s coefficient of performance (COP) by 5.67%.

Experimental Study of a Prototype Solar Water Heater Used in Sahelian Homes

Environmentally-friendly, low-cost energy supplies are the backbone of sustainable development. Development must not only meet current needs, but must also look to the future and consider environmental issues as a challenge. Solar power as an environmentally-friendly energy source is a promising way of reducing greenhouse gas emissions. One of the most important applications of solar energy is the production of hot water using solar water heaters. These solar water heaters, which can provide between 100 and 200 l/d of hot water over a temperature range of 40-70°C., are of the separate-element and integrated-storage types. In the Saharan environment, hot water requirements are concentrated in winter. It is therefore necessary to develop efficient systems adapted to this reality. It is then necessary to develop effective systems adapted to this reality. There is a need to propose a new design to boost the solar irradiation absorbed by the collector-storage while reducing nighttime thermal losses. For greater user-friendliness and with the aim of adapting them to the Saharan environment, it is also necessary to offer solar water heaters integrated into the building and operating mainly in the winter period. The present work represents an experimental study of a solar water heater with separate elements and a simple design, in a Burkinabe climate. This is a separate element solar water heater with a capacity of 200 liters with an aluminum collector as absorber designed at the Research Institute of Applied Sciences and Technologies (IRSAT). The water in the tank forms a loop with the sensor. In the tank, donut a copper coil of a length equal to 15m with a diameter of 16mm. They use the principle of thermosyphon (cold water pressure) to circulate and store heat and are simpler and less expensive, but can only be installed in sunny countries and have limited efficiency. During the measurement period from 11:25 a.m. to 4:05 p.m., the maximum temperature of the hot water was around 57°C at 11:45 a.m., and that of the cold water was around 27°C at 12:15 p.m.. The experimental results showed acceptable thermal performance despite the simplicity of the sensor. Finally, an improvement can easily be made whether by perfecting the thermal insulation or using selective collection surfaces.

Modelling and performance evaluation of a parabolic trough solar water heating system in various weather conditions in South Africa

In recent years, various energy sources and methods have been used to heat water in domestic and commercial buildings. Water heating methods for large households or commercial buildings include electrical heating elements, gas heaters, and solar energy (solar concentrators, flat plate collectors, evacuated tube collectors, etc.). In recent decades, the focus of water heating has shifted to solar energy, which is abundantly available in most African countries. The weather condition of a region has a huge impact on the system's performance. South Africa is characterised by four different weather seasons (winter, spring, summer, and autumn), unlike most African countries. Therefore, this study focuses on the impact of weather seasons on the system's performance for water heating through the combined use of solar energy and solar concentrator techniques. The system performance was modelled by using Matlab Simulink®, where historical weather data for Pretoria, South Africa, was fed into the model. Based on the weather data input, the system behaviour varied per season due to the change in solar intensity. The average outlet temperatures of the absorber, in the order of magnitude, were 333, 332, 328, and 325 K during the autumn, summer, spring, and winter seasons, respectively. Similarly, the average storage tank temperatures, in the order of magnitude, were 366, 364, 363, and 360 K in spring, summer, autumn, and winter, respectively. From this study, it is concluded that the different weather seasons in South Africa, have a direct impact on the performance of the system. Irrespective of the season, the system produced the required volume of hot water required throughout the year.

Correlation to predict thermal characteristics of pulsating heat pipes with long evaporator section

In terms of employing closed-loop pulsating heat pipes as heat transfer devices in solar water heaters, the evaporator should be extremely long according to the length of the solar collector. However, there is a noticeable shortage of Semi-Empirical Correlations for predicting the thermal performance of extra-long closed-loop pulsating heat pipes utilized for heat absorption within solar collectors. The primary objective of this study was to formulate a Semi-Empirical Correlation specifically designed for predicting the thermal efficiency in extra-long closed-loop pulsating heat pipe configurations. This study extensively examined the thermal efficiency of a comprehensive design of closed-loop pulsating heat pipe samples when implemented in an evacuated-tube solar water heater system strategically designed for individual households. The specified maximum length for the evaporator section of the closed-loop pulsating heat pipes is set at 1.50 m, in contrast to the conventional design, which typically features an evaporator section of approximately 0.15 m. Furthermore, the investigation encompasses a number of sets, varying as one, two, and four. Therefore, a Semi-Empirical Correlation derived from the experimental data concerning seven pertinent non-dimensional parameters is presented, demonstrating a standard deviation percentage of 4.4 %. Among these parameters, the number of sets emerged as the most influential, inducing a maximum percentage change in the heat rate of water of 20.47 %. Moreover, compared with other studies utilizing pulsating heat pipes in solar water heaters, the correlation exhibited a 1.52 % error. These findings suggest that the developed Semi-Empirical Correlation is a valuable tool for predicting the thermal performance of an extra-long closed-loop pulsating heat pipe. It is particularly well suited for estimating the thermal behavior of closed-loop pulsating heat pipes with extended configurations, showcasing its enhanced accuracy and relevance in capturing the distinction of heat transfer in extra-long closed-loop pulsating heat pipe systems.

Parametric study of low‐temperature solar‐assisted flash evaporation desalination systems using two‐phase water–steam ejector

AbstractThis study aims to investigate a two‐phase subsonic ejector added to a flash evaporation desalination system to increase the system productivity of distilled water. The flash evaporation was of low‐temperature condition that it could be powered by a flat and evacuated tube solar water heater. A parametric study of superheat degree (range 5°C–25°C), back pressure (range 10–30 kPa of absolute pressure), primary fluid flow rate (range 1–3 L/min), nozzle diameter (range 1–3 mm), and salinity concentration (range 0%–7%) were investigated to examine the system productivity and the ejector performance in terms of its entertainment ratio under different operating conditions. Results show that the inclusion of the ejector led to an average of 99% improvement in system productivity, primarily through the efficient secondary flow. Moreover, the effect of the studied parameter was more pronounced in the considered flash evaporation desalination system as it has two places where flash evaporation occurs, compared with the normal system where the flash evaporation occurs at one place. All in all, the application of the ejector could enhance the system's productivity significantly under different operating conditions.

Experimental analysis of the effect of copper dimple tube with aluminum coating on the performance of parabolic solar water heater using helically twisted tape

In this research, a parabolic trough solar water heater (PTSWH) having helically twisted copper tubes and dimple texturing with an aluminum (AlC) coat was experimentally examined to identify the solar collector’s efficiency, friction factor, convective heat transfer, Nusselt numbers variations, and uncertainty during the test. For this purpose, helical copper dimple tubes with Al coating were used to pass water through it at mass flow rates of 0.5–2.5 kg/min, with 0.5 kg/min increments. Experimental tests were conducted using specific datasets to investigate the efficacy of PTSWH. These experiments aimed to evaluate the efficiency and performance of solar collectors in harnessing solar energy for various applications, such as space heating, water heating, and industrial processes. The results of these experiments are recorded and analyzed to assess the practical viability of solar thermal systems. The results showed that solar collector effectiveness was improved by about 31.2% at flow rates of 1.5 kg/min, while the friction factor was raised by approximately 0.23%. The convective heat transfer coefficient was enhanced by about 7%, and the Nusselt numbers were enhanced to nearly 298. The overall uncertainty of ±2.3% was also observed, indicating that the findings were within the permissible range. Moreover, the PTSWH system recorded an elevated pressure drop of 2.32 kPa. This approach of dimple texturing with Al coating may be best suited for the PTSWHs used in moderate and low solar intensity regions.

Solar Water Heater Using an IoT

Abstract: Traditional water heaters use a lot of electricity to heat water. Traditional water heaters require a heating coil to heat water, which uses at least 2000 watts. It also requires human intervention. For this reason, we utilize solar energy. Solar energy is not only a clean and renewable alternative to fossil fuels, but it is also environmentally friendly, has a wide range of applications, and has low maintenance costs. Therefore, the aim of this project is to convert solar energy into electrical energy and utilize solar energy to heat water. The solar hot water system includes IoT, solar panels, various modules and various sensors. Based on this measurement, we provide a smart hot water system through a combination of Internet of Things technologies and business processes and decision support systems. Maintaining a traditional water system is inconvenient but often effective when regular human intervention is required. In this project work, the complete workflow of the system is presented.

Assessing the Feasibility and Techno-economic potential of Residential Solar Water Heating System in Hayatabad, a Township in Peshawar, Pakistan

Assessing the Feasibility and Techno-economic potential of Residential Solar Water Heating System in Hayatabad, a Township in Peshawar, Pakistan

Solar photovoltaic refrigeration system coupled with a flexible, cost-effective and high-energy-density chemisorption cold energy storage module

Owing to the environmental pollution and high costs associated with lead-acid batteries, this paper proposes a solar photovoltaic (PV) refrigeration system coupled with a flexible, cost-effective and high-energy-density chemisorption cold energy storage module. Its operation mode includes daytime solar PV refrigeration/cold energy charging mode and nighttime cold energy discharging mode. A novel composite sorbent SrCl2 is developed using expanded natural graphite as matrix and carbon coated aluminum as additive, exhibiting superior heat and mass transfer performance. A sorbent performance test bench is constructed, demonstrating that the cold energy storage density reaches 503.6 kJ/kg at an evaporating temperature of −15 °C, 1.5 times of ice storage. Compression-assisted desorption is adopted to regulate desorption temperature, so that 75–90 °C solar hot water from low-cost non-concentrating solar collectors can be utilized as the driving heat source. For an evaporating temperature of −10 °C and a solar hot water temperature of 90 °C, the electrical coefficient of performance for cold energy storage unit reaches 3.72, representing a 33 % improvement compared to conventional solar PV refrigeration systems. This novel system features characteristics such as low cost, high efficiency and eco-friendliness, offering a promising solution for solar refrigeration.

In situ performance evaluation of a solar water heating system for a hospital laundry in the Sahel

There is a limited number of empirical studies on the actual energy output of solar water heating systems (SWHSs). In the Sahel, where solar potential is abundant, the transition to sustainable energy solutions requires comprehensive evaluations of SWHSs, including their economic viability. Such assessments are crucial for informed decision-making by stakeholders and for facilitating the widespread adoption of SWHSs, including their integration into industrial processes. This paper presents a year-round experimental study assessing the real-world performance and economic viability of a SWHS integrated into a hospital laundry in Ouagadougou, Burkina Faso. The primary aim of the study is to analyse the practical performance of the integrated collector storage (ICS) SWHS and evaluate its economic viability. The performance of the ICS SWHS is monitored over the course of a year. Data collection included measurements of solar irradiation, ambient temperature, inlet and outlet water temperatures, and energy output of the SWHS. Economic assessments considered factors such as installation costs, energy savings, and payback periods. Environmental implications were evaluated through the estimation of avoided CO2 emissions. The ICS SWHS achieved an efficiency of 38 % and a solar fraction of 17 %, resulting in approximately 1.3 t of avoided CO2 emissions annually. Economic assessments revealed extended payback periods, leading to exploration of alternatives. Subsequently, a water-in-glass evacuated tube collector (ETC) system, deemed more cost-effective, was selected and it indicated superior energy production. Preliminary results suggest compelling payback periods for the ETC system, ranging from 3.1 to 4.5 years under realistic scenarios. The study underscores the significance of practical experimentation, appropriate technology selection, and improved market regulations for informed decision-making. SWHSs present a promising avenue for sustainable energy solutions in the Sahelian region and beyond, offering both economic benefits and environmental impact.

Thermal Assessment of Evacuated and Flat Plate Collector Solar Water Heater for the Enhancement of Collector Area

Thermal Assessment of Evacuated and Flat Plate Collector Solar Water Heater for the Enhancement of Collector Area

Investigation of a dual-spiral flat plate solar water heater under natural convection: an experimental study

In residential and industrial areas, a flat plate solar collector (FPSC) is an important technology that allows for direct solar energy utilisation for heating water. Conventional FPSCs have relatively low efficiency. More study is needed to increase the efficiency of FPSC by using novel designs. Modifications to the design of solar collectors are always a viable option for improving thermal efficiency significantly. In this study, dual spiral-shaped flow tubes were constructed instead of the usual flat plate solar collector's number of riser tubes and headers and tested with three different mass flow rates (0.0058, 0.0083, and 0.0117 kg/s). The optimum instantaneous efficiency achieved is 70.8% at a flow rate of 0.0117 kg/s, representing a 13.7% improvement in efficiency compared to the conventional collector. The modified collector achieves its highest instantaneous efficiency when the outlet water temperature is measured at 53.4°C. The modified collector improves heat transfer by increasing surface contact area of water and increasing the flow residence time. This results in a higher absorption of heat by the water, leading to a significant enhancement in the efficiency. When all other parameters are kept the same as in a conventional design, highly encouraging results in modified solar collector have been recorded.

Performance Optimization and Techno-Economic Analysis of an Organic Rankine Cycle Powered by Solar Energy

Abstract To improve the performance of traditional solar power generation systems, a new solar organic Rankine cycle system that can generate electricity and heat is proposed. The system incorporates the separation-flash process, regenerator, and ejector to enhance its efficiency. The optimization of the working fluid, pinch point temperature difference, evaporator outlet dryness, flash dryness, and entrainment ratio is conducted to achieve optimal performance. Aiming at maximum exergy efficiency and minimum levelized energy cost, the operating parameters are further optimized using a multi-objective optimization algorithm. R245fa is the optimal working fluid for the system, offering maximum net output power and thermal efficiency. The optimal performance can be achieved when the pinch point temperature difference is 1 K, evaporator outlet dryness is 0.6, flash dryness is 0.44, and entrainment ratio is 0.29. Moreover, the photovoltaic subsystem can further increase the net output power and thermal efficiency by 15.52% and 15.45%, achieving a maximum net output power and thermal efficiency of 33.95 kW and 10.61%. Additionally, when the solar hot water temperature is 100 °C, pinch point temperature difference is 1.8 K, evaporator outlet dryness is 0.6, flash dryness is 0.65, and entrainment ratio is 0.16, the system can achieve the optimal state of both performance and economy, exhibiting an optimal exergy efficiency and levelized energy cost of 64.1% and 0.294 $/kWh, respectively. Finally, the payback period of system is 3.43 years, indicating the potential for significant economic benefits.

Multi-criteria decision-making and artificial bee colony algorithm for optimization of process parameters in pyramid solar still

This study focuses on optimizing process parameters for pyramid solar still using Multi-Criteria Decision-Making Grey Relational Analysis (MCDM-GRA) and bio-inspired metaheuristic Artificial Bee Colony (ABC) algorithm. The objective is to enhance the performance of the pyramid solar still (PSS) performance integrated with a peripheral solar water heater under different operational parameters, including saline water flow rate, temperature, and solar intensity. Experiments are designed using Taguchi's L9 (33) orthogonal array (OA), and the outputs are optimized with MCDM-GRA. The optimum conditions for maximized productivity and system efficiency are a solar intensity of 1000 W/m2, a saline water mass of 3 kg, and a saline water temperature of 40 °C. With these settings, the system achieves an efficiency of 65.33 % and produces 1.96 kg of potable water. The ABC Algorithm, on the other hand, suggests that the optimal conditions for achieving maximum productivity and system efficiency involve a solar intensity of 1000 W/m2, a mass of 3 kg for the saline water, and a water inlet temperature of 30 °C. In this scenario, the system produced 1.92 kg of potable water with an efficiency rate of 64 %. Analysis of variance (ANOVA) shows that solar intensity contributes significantly towards productivity by 81.72 % with an error of 3.82 % and regression coefficient of 96.18 %. Regression models are developed from the results obtained and fed to ABC for further optimization, yielding results similar to MCDM-GRA.

Multi-objective optimization of a novel phase-change thermal storage unit based on theoretical modeling and genetic algorithm

Phase-change thermal storage technologies are becoming increasingly indispensable in the field of renewable energy, and researchers have been striving to achieve high thermal storage performance in storage devices. To enhance the application potential of phase-change thermal storage units based on micro heat pipe arrays, theoretical analysis is applied to optimize the operating parameters and the fin structure, addressing the research gap caused by insufficient theoretical analysis. Therefore, an accurate thermal resistance network model is developed, and machine learning algorithms are employed for the multi-objective optimization of the fin structure. The optimal heights, widths, and thicknesses in two directions of the fins are 42.2, 3.7, 0.3, and 0.8 mm, respectively, resulting in a 15.8 % increase in charging power compared to the initial structure without increasing metal consumption. Additionally, it is recommended that the design flow rate be increased by 26 kg/h for each additional thermal storage unit connected in series. Finally, a phase-change thermal storage device is designed for a solar water heating system, and its applicability is simulated and analyzed. This study provides design guidance for this novel thermal storage device and promotes its application in the field of renewable energy.

Performance evaluation of combined passive/active thermal charge/discharge latent heat tank with stabilized-solid-liquid storage material for intermediate thermal storage system

This study proposes a new model operation for an intermediate thermal storage (ITS) tank for solar water heater system. It combines passive-charge active-discharge (PCAD) in a single storage tank, potentially reducing the number of components of the system and improving the net energy balance. The charge process is done by heating the storage material using an electric heater, which is also suitable for direct photovoltaic heating. The temperature profile of stabilized storage material in this stage shows a close plateau line in the solid-liquid transition, indicating a steady phase transition takes place. It minimizes the temperature deviation between the solid/liquid region, which is advantageous for determining the operation protocol. For the discharge process, the working fluid circulates from the mantle side and continues to the inner side of the tank, resulting in two-consecutive heating. It allows the fluid to harness the stored heat up to 72.8%. It is also achieved by the stabilized storage material, which has a better solidification mechanism. Thus, the proposed PCAD tank is able to meet the criteria of an ITS tank, which requires energy exchange during the charge/discharge stage. The finding demonstrates that a simplification of the ITS tank is achievable. The implication of the finding can be used as a fundamental basis for developing new solar water heating systems, including for direct charge operation using photovoltaic-heating systems where the heat is taken as alternative energy storage instead of electricity.