Solar Water Heating Research Articles

Optimizing Energy Yield and Economic Benefit of Renewable Energy Technologies for Urban Mediterranean Dwellings

Mediterranean European cities are characterized by high population density and limited space for large-scale implementation of renewable energy installations. This paper addresses the optimization of renewable energy installations in Mediterranean dwellings with the scope of increasing their energy contribution and cost-effectiveness. In a case study for Malta, the three technologies studied were solar photovoltaics, solar water heating, and heat pump water heating. Technical and economic analyses were performed on a number of reference configurations using Polysun software (version 2022.8). Sensitivity analyses were also conducted to study the impact that different technical and economic factors have on the performance of the configurations considered. Finally, comparisons were made between the techno-economic results obtained from the reference and sensitivity analyses. Based on data collected, the presence of renewable energy source (RES) technologies in the residential sector of Malta was characterized and correlated with the types of dwellings considered. Among the results obtained, it was found that although a solar RES installation may experience some shading, this does not mean that it is rendered economically unfeasible. Moreover, from the simulations conducted, electrical energy storage technology was considered as too premature unless strongly subsidized, making economic sense only in specific circumstances. On the other hand, although heat pump water heating technology is also relatively modern, it was concluded to be the most beneficial in terms of both energy yield and economic benefit, generally speaking. Furthermore, it was determined that in a higher occupancy dwelling, solar water heating (SWH) and heat pump water heating (HPWH) result in considerably more attractive energy savings.

Performance Improvement of an Integrated Collector Storage Solar Water Heater by Using an Additional Glass Cover: A Numerical Study

This paper describes the analysis of a solar storage water heating system, emphasizing its cost-effectiveness and integrated design. The study employs numerical analysis to assess and optimize the performance of a rectangular solar collector with an added glass cover and an internal horizontal barrier. Using COMSOL software, a three-dimensional modeling study was conducted in the Kufa-Najaf climate on May 9th. The analysis focused on fundamental convection equations governing mass, momentum, and energy conservation. Temperature and velocity distributions were obtained at 13:30 PM, revealing a peak storage water temperature of 56.3 °C. The additional glass cover-barrier storage collector, set at a 60° angle, exhibited the highest stored energy at 2065.6 W, surpassing the conventional storage collector at 1007.06 W. Furthermore, the model demonstrated an increased instantaneous efficiency of 58.3%, compared to 28.4% for the conventional collector. The simulation results align well with previous findings, showing a maximum mean absolute percent error (MAE) of 4.5%.

Storing Excess Solar Power in Hot Water on Household Level as Power-to-Heat System

PV technology has become widespread in the Netherlands, reaching a cumulative installed capacity of 22.4 GWp in 2023 and ranking second in the world for solar PV per capita at 1268 W/capita. Despite this growth, there is an inherent discrepancy between energy supply and demand during the day. While the netting system in the Netherlands can currently negate the economic drawbacks of this discrepancy, grid congestion and imbalanced electricity prices show that improvements are highly desirable for the sustainability of electricity grids. This research analyzes the effectiveness of a Power-to-Domestic-Hot-Water (P2DHW) system at improving the utilization of excess PV electricity in Dutch households and compares it to similar technologies. The results show that the example P2DHW system, the WaterAccu, compares favorably as a low cost and flexible solution. In particular, for twelve different households differing in size (1–6 occupants), PV capacity (2.4–8 kWp), and size of hot water storage boiler (50–300 L), it is shown that the total economic benefits for the period 2024–2032 vary from −€13 to €3055, assuming the current net metering scheme is abolished in 2027. Only for large households with low PV capacity are the benefits a little negative. Based on a multi-criteria analysis, it is found that the WaterAccu is the cheapest option compared to other storage options, such as a home battery, a heat pump boiler, and a solar boiler. A sensitivity study demonstrated that these results are overall robust. Furthermore, the WaterAccu has a positive societal impact owing to its peak shaving potential. Further research should focus on the potential of the technology to decrease grid congestion when implemented on a neighborhood scale.

Application of heat pump assisted solar evacuated tube water heater operated within passive solar house in severe cold region

Replace coal with solar energy to low-cost heating in severe cold regions can improve indoor air quality, but indoor thermal comfort is not fully guaranteed. Therefore, a dual-source heat pump (DSHP) assisted solar evacuated tube water heater heating system was used in a house with sunspace to meet the heating stable and cleaning. TRNSYS model verified by experiment was used to research performance and economy of system. Results found the higher ambient temperature and solar radiation, the more heat from sunspace, solar assisted heat pump (SAHP) and solar water heater, conversely, the longer heating time of air-source heat pump (ASHP). During heating season, solar fraction of heating was 51.6 %, solar heat collection efficiency was 46.0 %, EER was 3.35, COP were 2.81 (ASHP) and 3.65 (SAHP). Heating time proportion of ASHP, SAHP and solar water heating were 15.0 %, 40.3 %, 44.7 %, ASHP heating was accounting for 22 % and 50 % in November and January. The system, sunspace supplied 16707.1, 2307.6 kW h of heat for room, solar effective heat collection was 10107.0 kW h, power consumption was 5164.7 kW h, CO2 emission reduction was 14232.4 kg. The dynamic payback period of system was 6.78 years, as will be shortened with support of clean energy heating policy.

Experimental study on thermal performance of reverse flow solar collector for dual heating applications

AbstractThe present study investigated the performance of dual function reverse flow solar collector (RFSC). The impact of the mass flow rate of air and water on outlet temperature, thermal performance, and overall performance of dual‐function solar air heater (SAH) has also been investigated. An experimental investigation of three different working models namely, Model‐A: SAH, Model‐B: solar water heater (SWH), and Model‐C: integrated solar air‐water heater (SAWH) for dual heating applications was performed to analyze the actual performance of these models. The investigation of the impact of time intervals on the water inlet and outlet temperatures at various mass flow rates of water is conducted to analyze the time‐varying efficiency of SWH systems. Furthermore, the effect of solar intensity on the performance of the dual‐function heating system has also been explained. The result reveals that the maximum thermal efficiency of Models: A and B can be achieved at about 78.8% and 67.9%, at a mass flow rate of 0.0644 and 0.10 kg/s, respectively, according to the experimental findings. The maximum temperature rise of air and water reaches about 52.4 and 55.58°C for Models A and B, respectively. The total efficiency of Model C reaches 81.69%, exceeding that obtained in Models A and B individually. The efficiency, outlet temperature of the fluid, and heat transfer effectiveness of the system strongly depend on the mass flow rate. The increase in heat removal factor is negligible for a higher flow rate (more than 0.10 kg/s).

Sun-powered solutions: Investigating productivity and economics of small-scale solar desalination system

Freshwater demand is one of the most critical challenges facing many countries in the world. Jordan is a country in the middle east that is considered one of the poorest countries for renewable freshwater supplies in the world. Though desalination may be one of the solutions to the problem, the cost and energy expenses could be an obstruction. However, with an abundance of annual solar irradiance in Jordan, solar desalination systems, particularly small-scale ones, are considered better alternatives. In this study, a residential-scale solar desalination system is investigated. The design includes evacuated-tube solar heaters with a heat pipe, and flashing units comprising three desalination stages. The experiments included single-stage, double-stage, and triple-stage desalination. The results showed that production rates of 2.2 kg/m2 using single-stage, 4.7 kg/m2 using double-stage, and 6.4 kg/m2 using triple-stage desalination were obtained from the system. The solar water heater used in the system exhibited an average thermal efficiency of 73 %. The economic analysis revealed that the payback period for the triple-stage desalination system is 8 years. The annualized rate of return was calculated to be 2.2 %, assuming the system operates for 4 h per day and 300 days per year.

Study of the performance of an individual solar water heater

Study of the performance of an individual solar water heater

Exergetic characterization of flat plate solar collector using genetic algorithm

With the rapid advancement of technology, the global demand for energy is increasing exponentially. It is crucial to focus on energy conservation and conversion across all sectors. This study conducted a second law or exergy analysis on a solar water heating system to uncover hidden losses during the process. To optimize exergetic efficiency, a genetic algorithm was employed to control the overall loss coefficient of a solar flat plate collector. Four decision variables were used in the genetic algorithm—heat flux rate, glass cover temperatures at the inlet and exit, and collector plate temperature to minimize the overall loss coefficient. Energy efficiency, entropy generation, and exergy destruction were estimated for various mass flow rates using thermodynamic equilibrium equations. Exergy correlations were developed concerning mass flow rate (0.001–0.009 kg/s), inlet temperature (300 K–360 K), collector plate area (1–10 m²), incident solar energy (400–900 W/m²), optical efficiency (0.4%–1%), and ambient temperature (300–315 K) under a range of initial conditions. It was found that exergy efficiency slightly increased (0.01%–0.08%) over a 12-h period. Although this increase is small, it can significantly contribute to energy conservation over the long term. The genetic algorithm predicted the minimum loss coefficient occurring during peak hours (12–14 p.m.) with respect to four decision variables. The results of this study were compared with existing literature and showed good agreement. In addition to the exergy analysis, an uncertainty error analysis was performed to assess the reliability and accuracy of the experimental measurements and computational predictions. By quantifying these uncertainties, the study ensured that the reported enhancements in exergy efficiency and the optimization results obtained through the genetic algorithm are robust and credible. This rigorous error analysis adds confidence to the findings, highlighting the potential for improved energy conservation in solar water heating systems.

Efficiency-aware machine-learning driven design of solar harvester for renewable energy application

Although MIM structures have been studied for solar thermal applications for decades, the multilayer MI-MIM structure is the subject of this study's investigation for batter absorption. In order to identify an effective solar absorber, two configurations Gold-MgF2-Gold (GMGSA) and Gold-MgF2-Gold-MgF2-Gold (GMGMGSA) are examined in this work. By using machine learning approaches, this research was able to get an MSE of 2.8091 × 10−5 and an R2 value of 0.998836. The optical response and parameter optimization analysis have been examined in this work in the wavelength range of 0.4 μm–1.6 μm. When exposed to AM 1.5 spectrum radiation, the GMGMGSA absorbs 93.10 % of the radiation, compared to 88.30 % for the single-layer GMGSA. Furthermore, both structures show steady absorption that is independent of polarization up to a 70° incidence angle. The aforementioned discoveries render the structure a plausible contender for solar thermal uses, including battery-integrated photovoltaic (BIPV), commercial solar power (CSP), and solar water heating. This might lead to a future where energy is more sustainably produced.

Study the effect of adding rectangular fins along the riser pipe on the thermal performance of the flat‐plate solar water heater system

Study the effect of adding rectangular fins along the riser pipe on the thermal performance of the flat‐plate solar water heater system

Transparent insulation integration in solar thermal collector: Advancing performance for domestic water heating in oceanic climates of Western Europe

Decarbonizing residential hot water demand requires efficient solar collectors. Conventional flat plate collectors are widely available but experience high heat losses in colder climates. This work investigates the performance of a modified flat plate collector that incorporates honeycomb transparent insulation to reduce convective heat loss, offering a cost-effective alternative to energy-efficient evacuated tube collectors. The thermal performance of the modified flat plate collector was obtained using the finite element method in COMSOL Multiphysics, revealing a significant reduction in convective heat loss. The obtained thermal performance was then incorporated into a transient simulation to assess the year-around performance of the modified flat plate collector in a solar domestic hot water system for Irish climate. The transient simulation accounted for variations in the transparent insulation’s transmission with incidence angle which was overlooked in previous studies. Over a year-long simulation, the modified flat plate collector generated a total useful energy of 532.45 kWh m−2, while requiring 1640 kWh of auxiliary energy to meet the hot water demand of a single-family house in Ireland. An economic analysis of solar domestic hot water system revealed that the modified flat plate collector could yield savings of 443.44 € more than the standard flat plate collector and 3281.03 € more than the evacuated tube collector for homeowners. Consequently, the simple payback period for the solar domestic hot water system decreased from 3.72 years with a standard flat plate collector and 8.37 years with an evacuated tube collectors to 3.56 years with a modified flat plate collector. In addition to its economic viability, the modified flat plate collector could result in a CO2 savings of 901.85 kgCO2 per year. The study concludes with a sensitivity analysis to identify the market conditions that maximize the profitability of the modified flat plate collector based solar domestic hot water system.

دراسة عملية لاداء سخان ماء شمسي ذو الدوران الطبيعي المتصل على التوالي

This research paper presents an experimental study on the performance of a natural circulation solar water heater system with two typical collectors connected in series. The paper provides a comprehensive analysis of the system's thermal performance under different load conditions, including no-load, intermittent, and continuous load. Mean storage tank, solar collector means plate (the left) temperature and thermosyphon flow rate in a vertical tank were measured. Results showed that there was variation in solar water tank and collector plate temperature under load and no-load conditions. Analysis of thermal performance of the system was conducted for each condition. The highest plate temperature (100 ˚C or even more) with no circulation of both collector and load conditions, indicate the high quality of the solar collectors even during the cold season. The collector’s arrangement in series connection is of highest gain in energy and higher storage tank mean water temperature. Several characteristic equations obtained to represent the performance of the present natural circulation system under collector connection arrangement in series. In fact, when large amount of hot water was required for a certain purpose (Industrial sector for example - MSF plant or central heating), multiple collectors are to be deployed in series and in parallel to produce the required amount (quantity) and desired temperature (quality) at the same time. Key words: Thermosyphon solar water heater, storage tank profile temperature, Solar Water Heaters (SWHs), instantaneous efficiency, collector flow factor, collector efficiency factor, collector heat removal factor

Performance testing of an innovative integrated zenithal daylight guide with solar water heater under real-weather conditions

Zenithal Daylight Guides (ZDG) and Solar Water Heaters (SWH) are individual energy-saving solutions utilized across diverse building types. This study proposes an innovative integrated power-saving system, uniting ZDG and SWH into a single model. The integration concept is rooted in leveraging the available space surrounding the daylighting device's pipe to incorporate a solar heater via a serpentine collector. The primary aim of this amalgamation is to optimize solar energy savings, minimize spatial demands, and alleviate manufacturing expenses. Moreover, the impetus behind this study stems from the recent emergence of daytime power outages in Egypt, attributed to heightened consumption surpassing production capacities. The ZDG is still not well known in Egypt. This is the only study until the year 2022/2023 in Aswan, Egypt, that analyzes the performance of this device under extreme sunlight conditions (with maximum global illumination reaching approximately 118 Klux). Across various seasons, the lighting and thermal efficacy of the current model underwent experimental testing and analysis to assess its practical utility. The integrated system effectively elevated the water temperature and achieved adequate light transmission, as indicated by the obtained results. The average transmitted indoor illumination on the work surface reached approximately 2470 lux. The reliance on electrical lighting could be mitigated for up to 5 hours. On the other hand, the highest water temperature and maximum instantaneous efficiency reached are about 70°C and 37%, respectively. Throughout the experiments, the proposed solar heater achieved a maximum daily thermal efficiency of 31.5%. The findings are deemed satisfactory and promising.

Mathematical Study of a Double-Slope Passive Solar Distiller with Water Heater Condenser

In this article, the inevitable condensation losses from the back-side glass cover of a passive single-basin double-slope distiller (PSDD) were recovered in heating water inside a glass solar water heater (SWH) to produce hot water as an auxiliary product of the distiller. The transient thermal performance of the PSDD-SWH was mathematically modeled and compared to a conventional PSDD in actual weather circumstances. Compared to a conventional PSDD, the results revealed that the thermal efficiency of the PSDD-SWH increased by 18% to 83% during the day. In addition, increasing the water mass inside the water heater from 3kg to 18kg increased the thermal efficiency of the PSDD-SWH by about 50% despite decreasing the total distillate by less than 1%. Moreover, the thermal performance of the PSDD-SWH, in terms of distillate production, hot water temperature, and thermal efficiency boomed in hot climates with high solar irradiation and high ambient temperatures. Furthermore, insulating the glass covers of the PSDD-SWH during off-sun hours significantly enhanced the thermal performance of the PSDD-SWH.

The Effect of Added Wire Mesh on The Thermal Efficiency of the Flat Plate Solar Water Heater Collector

The current study looks into the effects of using wire mesh to expand the flat plate solar collector (FPSC) on the system's thermal efficiency under transient heat-flux without changing its dimensions and its placement to minimise the shadows cast on the collector while utilising passive methods to circulate the working fluid. Thus, the traditional model was investigated numerically (using ANSYS fluent) and experimentally to establish the accuracy of simulation results. Then, the three models, A, B, and C, were tested numerically. In model A, the mesh is used to cover the riser pipe. In model B, the mesh covers the collector plate; in model C, the mesh is placed on both the riser pipe and the plate. The wire mesh placement in all three models improved the thermal efficiency of the FPSC. In addition, model C proved to be paramount to all models under study, classical models A and B, by having a higher thermal efficiency of 41.4%, 14%, and 31.2%, respectively.

Fabricated of Photovoltaic Thermal System with Phase Change Material

At present, solar energy is widely recognized as one of the primary sources of renewable energy. Nonetheless, conventional solar photovoltaic (PV) panels suffer a significant decrease in efficiency when exposed to extreme temperatures, making them unsuitable for long-term operation. To address these limitations, hybrid photovoltaic thermal (PVT) systems with phase change materials (PCM) have emerged as sophisticated solutions, leveraging thermal energy for water heating and PCM for thermal energy storage. This work aims to evaluate key economic parameters of fabricated PVT system (with and without PCM) against commercial solar water heaters and electric heaters, using metrics such as payback period and annual worth. The calculations are carried out using Microsoft Excel spreadsheets. The results reveal that the payback period for PVT systems, both with and without PCM, exceeds 25 years, primarily due to the high initial costs associated with PVT technology. In contrast, solar water heaters and electric water heaters offer shorter payback periods. Specifically, after 25 years, the annual worth for the fabricated PVT system is MYR 923.12. Essentially, the economic analysis suggests that the PVT system has a longer operational lifetime than solar water heaters and electric heaters, despite the extended payback period. This economic analysis has the potential to encourage the large-scale fabrication and installation of efficient PVT-PCM systems. It provides consumers with a viable alternative to consider installing PVT and PVT-PCM systems instead of PV and solar thermal systems separately. Additionally, this study contributes to reducing carbon emissions and advancing the Sustainable Development Goals (SDGs).

Thermal Performance Solar Flat Plate Collector and Influence of Flow Pipe Design

Flat plate collectors are commonly utilized in both domestic and industrial applications to minimize energy consumption. In this study, solar flat plate collector (SFPC)) with corrugated flow pipe with ten turns placed over flat absorber plate and covered with single glass layer was fabricated and tested, in Al-Mussiab city, Babylon, Iraq (latitude 32.5◦N and longitude 44.3◦E). This research presents the effect flow pipe shape about the SFPC's thermal performance. The designed solar collector utilized employing of 12.5 mm-diameter corrugated copper tubing that extended 19500 mm in total length. According to different rates of water flow namely (50, 100, and 150 L/h). The results indicated that the working fluid's greatest temperature differential between the inlet and outlet of solar collector (12.9°C) at volumetric flow rate (50 L/h). The maximum thermal efficiency (Ƞth) rate of solar flat plate collector was (77%) at (150 L/ h). These results encourage the development of solar collector system and eventually help the sustainable use of solar power in home applications, including solar water heating system.

Small object change detection in UAV imagery via a Siamese network enhanced with temporal mutual attention and contextual features: A case study concerning solar water heaters

Small object change detection (SOCD) based on high-spatial resolution (HSR) images is of significant practical value in applications such as the investigation of illegal urban construction, but little research is currently available. This study proposes an SOCD model called TMACNet based on a multitask network architecture. The model modifies the YOLOv8 network into a Siamese network and adds structures, including a feature difference branch (FDB), temporal mutual attention layer (TMAL) and contextual attention module (CAM), to merge differential and contextual features from different phases for the accurate extraction and analysis of small objects and their changes. To verify the proposed method, an SOCD dataset called YZDS is created based on unmanned aerial vehicle (UAV) images of small-scale solar water heaters on rooftops. The experimental results show that TMACNet exhibits strong resistance to image registration errors and building height displacement and prevents error propagation from object detection to change detection originating from overlay-based change detection. TMACNet also provides an enhanced approach to small object detection from the perspective of multitemporal information fusion. In the change detection task, TMACNet exhibits notable F1 improvements exceeding 5.96% in comparison with alternative change detection methods. In the object detection task, TMACNet outperforms the single-temporal object detection models, increasing accuracy with an approximately 1–3% improvement in the AP metric while simplifying the technical process.

Optimization of vacuum membrane distillation and advanced design of compact solar water heaters with heat recovery

With the escalating global population, freshwater scarcity has become a pressing challenge. To address this issue, this paper presents a novel compact solar water heater (CSWHT) system incorporating heat recovery and submerged-membrane filtration. The research aims to develop an efficient desalination method that reduces water production costs and maximizes output. The system comprises a feed storage tank, a vacuum membrane distillation (VMD) system positioned atop the submerged CSWHT, a liquid ring vacuum pump (LRVP) utilizing waste heat from the outlet to preheat the feed, and hollow fiber membranes.Three critical parameters, namely the mass of the feed in the storage tank, the number of hollow fiber membrane rows, and the feed volumetric flow rate, were optimized using a multi-objective non-dominated sorting genetic algorithm II (NSGA II) to minimize water production cost (WPC) while maximizing water production. Subsequently, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) was employed to identify the optimal scenario from among the selected best solutions.For Mediterranean seawater and a 6 m2 solar collector area, the multi-objective NSGA II algorithm identified 20 membrane rows per collector, 334.4 kg feed mass in the storage tank, and 0.027 kg.s−1 feed mass flow rate as the optimal system parameters. Under these optimized conditions, the system exhibited a daily production capacity of 92.5 kg water, 4.6 kg chloride, and 0.03 g bromide, while achieving a production cost of 12.2 USD.m−3 and a gain output ratio (GOR) of 1.6. These results highlight the system's remarkable potential for desalination with high efficiency and low cost. Future research should focus on scaling up the system and exploring its applicability in various geographical locations.

Electrochemistry of Phase-Change Materials in Thermal Energy Storage Systems: A Critical Review of Green Transitions in Built Environments

This article reviews recent research on phase-change materials (PCMs) used in thermal energy storage systems with the aim of enhancing their performance. The study explores various methods to improve heat transfer in PCMs, such as microencapsulation, infill materials, fins and nanofluids. Additionally, it evaluates techniques to boost heat transfer in latent heat thermal energy storage (LHTES) systems and investigates ways to increase thermal conductivity using porous and low-density materials. PCMs store thermal energy, making them suitable for use in solar energy systems when solar energy is not available. The need for eco-friendly alternatives to conventional heating and cooling in global construction and the significant energy consumption of buildings has driven research on this topic. As such, this study additionally examines current advancements in free cooling systems with latent heat storage to identify the key factors affecting their effectiveness. The findings show that using PCMs for overnight cooling maintains the room temperature within the comfort zone and reduces the cooling loads in various climates. Using machine learning methods, this study also compares recent advancements in the use of PCMs in various solar energy systems, including solar thermal power plants, solar air purifiers, solar water heaters and solar appliances. Results derived feature key factors crucial for the optimal selection of PCMs and the challenges associated with sustainable green transitions in built environments. HIGHLIGHTS This review provides an in-depth examination of PCM thermal energy storage systems. This study investigates the use of fillers, nanofluids, and nanoparticles for enhanced heat transfer. Analytical methods for boosting the PCM thermal conductivity are briefly outlined. Geometric design and thermal conductivity enhancement affect the Latent Heat Thermal Energy Storage (LHTES). The assessment also evaluates advanced free-cooling systems using the LHTES. PCMs help to store heat energy in solar systems and bridge supply gaps. GRAPHICAL ABSTRACT