Flat Plate Solar Water Heater Research Articles

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.

Intensification of thermal characteristics of flat plate solar water heater using triangular perforated wavy tape

The efficiency of the flat Plate Solar water heater has improved experimentally using passive methods. Experiments have shown that the addition of wavy tape (WT), 6 mm perforated wavy tape (PWT), and 9 mm perforated wavy tape (PWT) to a forced circulation solar water heater improves rate of heat transfer (Nu), friction factor (f), and effectiveness. Wavy tape inside the pipes induces secondary swirl flow, which improves mixing and increases heat transfer coefficients. The heat transfer rate (Nu) is increased by the incorporation of wavy tape; FPC with 6 PWT was higher than FPC without WT, FPC with plain WT, and FPC with 9 PWT by 20.83%, 14.85% and 6.25%, respectively. The maximum temperature difference of FPC with 6 PWT was higher than FPC without WT, FPC with plain WT, and FPC with 9 PWT by 61.9%, 22.9%, and 12.62% respectively. The maximum efficiencies value observed was 37.55%, 49.46%, 54.013%, and 51.03% for FPC without WT, FPC with plain WT, FPC with 6 PWT, and FPC with 9 PWT, respectively.

Study on the photothermal conversion enhancement performance and application of the metal-polyphenol phase-change microcapsules modified by molybdenum disulfide

Aiming to improving photothermal conversion and heat storage efficiency, layered molybdenum disulfide (MoS2) was prepared with hydrothermal method, which was used as the thermally conductive and photothermal conversion material to modify metal-polyphenol (MPN) /paraffin (PA) microcapsules. The fabricated phase-change microcapsules (MoS2/MPN@PA-MEPCM) exhibits excellent thermal conductivity, photothermal conversion and heat storage performance. The effect of the additive amount of MoS2 on the leakage performance, microstructure, thermal conductivity, heat storage capacity, thermal stability and photothermal conversion performance of MoS2/MPN@PA-MEPCM was investigated. Furthermore, the enhancement mechanisms of the thermal conductivity and photothermal conversion were analyzed. The results show that when the additive amount of MoS2 is 10 wt%, the phase-change enthalpy of MoS2/MPN@PA-MEPCM reaches 127.1 J/g with an encapsulation ratio of 53.74 %. Compared to MPN@PA-MEPCM, the thermal conductivity of MoS2/MPN@PA-MEPCM increases by 88.45 % and the photothermal conversion and heat storage efficiency reaches 90.78 %. When the solar radiation intensity is 800 W/m2 and 1000 W/m2, the thermal efficiency of PFPSC is 57.17 % and 59.45 % respectively, which is higher than that of FPSC. The operation time of PFPSC is extended by 2435 s and 2750 s, respectively, improving the operational stability of flat plate solar water heaters. The developed microcapsules in this study demonstrate significant potential for highly efficient solar energy utilization and thermal energy storage in the fields of seawater desalination, solar water heating system and building heating.

Investigation on thermo-fluid behavior of flat-plate solar water heater employing titanium dioxide-water nanofluid: An experimental and computational approach

Investigation on thermo-fluid behavior of flat-plate solar water heater employing titanium dioxide-water nanofluid: An experimental and computational approach

Energetic and exergetic study of a flat plate collector based solar water heater - investigation of the absorber size

Small sized absorber in a flat plate solar collector is beneficial in terms of cost and minimum heat losses. However, its detailed thermal performance compared to standard size collector is still not fully understood. There is a paucity of research to appreciate thermal performance of solar water heating collector with consideration of a small absorber size (below 1m2) and a standard absorber size (2 m2). The present study attempts to investigate the energy and exergy efficiencies of flat plate solar water heating collector with two absorber plate areas (2 m2 and 0.74 m2) to enumerate size of the absorber required for improved first and second law thermal efficiencies of the collector. The efficiencies of these two collector designs are experimentally compared with the help of a test facility available in the site for given operating temperatures and rate of flow. The combined experimental uncertainty due to the measuring instruments and the measured parameters is also ascertained. The obtained results highlight the significance of the larger absorber size (2m2) for higher thermal efficiency, and lower absorber size (0.74m2) for higher exergetic efficiency. The highest thermal efficiency obtained is 77.38% for larger absorber size, and the highest exergy efficiency of 13.21% is obtained for lower absorber size collector. It is demonstrated that larger and lower absorber size of the collector have higher thermal efficiency and higher exergy efficiency, respectively, than some of the published works.

Real-time outdoor experiment and performance analysis of dual-coil heat exchanger integrated thermal energy storage

Integrating a thermal energy storage system into a solar water heater enables a continuous heat supply to ensure hot water is available for household uses throughout the day. This research emphasizes integrating TES units into solar water heating systems. The overall performance of flat plate solar water heaters for a regular (conventional) solar water heating system and a solar water heating system integrated with TES using phase change material (PCM) are analyzed. This innovative design ensures efficient heat capture from the sun, storing it in the phase change material for later use, guaranteeing a sustainable and cost-effective solution for hot water needs. A split PCM tank is integrated within the solar water heating network for the second scenario and is made of a 25 L filled with a phase change material that acts as the thermal storage medium. The PCM tank has a dual-coiled heat exchanger to aid the heat transfer process with paraffin wax as the phase change material. The parameters that are looked into from the conventional and TES-integrated solar water heating systems include the water temperature profiles throughout the entire solar water heating networks and the PCM's temperature distribution throughout the day. A customized water draw schedule is adapted to represent the average hot water usage of a typical household in Kuala Lumpur. Findings reveal that the TES-integrated solar water heating system can be 21 % more efficient than the conventional system due to the lesser heat losses and prolonged hot water supply. The maximum efficiency obtained is about 82 %, and energy can be saved about 50 % from the electric heater. The maximum energy storage is at the 50 °C temperature controller's setting and is feasible for the existing conventional solar water heaters.

Experimentally validated axisymmetric simulation for thermo-fluid performance of an active flat-plate solar water heater at low flow rates

ABSTRACT In this work, the thermo-fluid performance of a liquid flat-plate collector (FPC) has been analyzed using experimental and computational methods. A closed-loop active flat-plate solar water heater (AFPSWH) was tested under quasi-static and laminar flow operating conditions, where a maximum instantaneous collector efficiency of 62.82% and an outlet temperature of 45.2°C were attained in the winter with flow rates of 0.012 and 0.004 kg/s, respectively. Raising the flow rates from 0.004 kg/s to 0.008 and 0.012 kg/s reduces the energy loss parameter [FRUL] by 23.77% and 34.61%, whereas the absorbed energy parameter [FR(τα)n] improves by 10.48% and 21.55%, respectively. The suggested axisymmetric numerical model was validated with outcomes of an in-house developed lab scale experimental setup, with less than 1.5% deviations for all studied cases. In addition, the overall thermal efficiency of the solar thermal system (STS), Nusselt number (Nu), and friction factor (f) have been analyzed for a comprehensive understanding of the system’s thermo-fluid performance.

Numerical analysis with experimental validation for thermal performance of flat plate solar water heater using CuO/distilled water nanofluid in closed loop

Numerical analysis with experimental validation for thermal performance of flat plate solar water heater using CuO/distilled water nanofluid in closed loop

Critical operating parameters of solar flat plate collectors using CuO nanoparticles of different volume fractions subjected to natural convection

AbstractA flat plate solar water heater is investigated for its efficiency when water and the copper oxide (CuO) of 20 nm size nanoparticles of varying volume fractions and their performance are studied. A solar water heater with a flat plate collector of dimensions 1 × 0.45 m2 with 25 liter per day storage tank capacity, which works on the thermo‐syphon principle, is fabricated. The collector is run with a base working fluid of deionized water and then with CuO nanoparticles for different volume fractions of 0.2% and 0.4% with a surfactant to study the collector's efficiency. The surfactant used in cetyltrimethylammonium bromide of 1% in working fluid. The rise in temperature and the collector efficiency is compared for different volume fractions of CuO nanoparticles in the collector. The mixing of nanoparticles thus improves the efficiency of the collector. The experimental result shows that the collector with a 0.4% volume fraction of CuO with water as a working fluid has the maximum rise in temperature and efficiency compared with that of 0.2% and water. During the test, CuO without surfactant showed a slight decrement in heat transfer due to the agglomeration. The collector efficiency for 0.4% volume fraction achieves 63.28%, for 0.2% is 61.58%, and for water 54.15%. The overall efficiency was increased by up to 9.1% compared with base conventional fluid water for lower volume fractions of CuO nanoparticles for a smaller collector area.

Potential of simple and hybrid nanofluid enhancement in performances of a flat plate solar water heater under a typical North-African climate (Tunisia).

This work aims to quantify the long-term performance improvement of solar water heater system by using both simple and hybrid nanofluids. For this purpose, transient system simulations of a flat plate solar collector have been carried out and discussed using titanium oxide, magnesium oxide, and copper oxide/multiwalled oxide-carbon nanotube nanofluid-based nanoparticles. Tunisian climatic conditions witha typical household need has been considered, and the investigations have been established in terms of energy amounts, solar fractions, and harmful CO2 emission avoidance. Results showed an increase in the collector performances using the considered nanofluids. In particular, using 0.2v% and 0.6v% TiO2 homogeneously dispersed in water reduced the auxiliary energy up to 47.6 and 60.9%, respectively, compared to the reference case using water. The flat plate solar collector has an annual production of 1294 kWh for a need of 1998 kWh, which equates to an annual coverage rate of roughly 65%. Additionally, it was shown that when MgO with MWCNT were used instead of MgO nanofluid-based nanoparticles, the solar fraction increased by 5.14%. The use of 0.6 volume percent TiO2 nanoparticles in water reduces hazardous CO2 emissions by up to 0.829 tons annually.

Numerical and experimental analysis of the flat plate solar water heater systems' thermal performance

AbstractIn this paper, improving the thermal performance of flat plate solar water heater systems by inserting different tube configurations inside the riser pipes has been numerically and experimentally studied. This study is focused on increasing the moving of energy from riser pipes to the operating fluid within the riser pipes. To achieve that, the diameter of the riser pipes was increased along with the insertion of different tube configurations within them, namely, smooth, helical, and wavy tubes, keeping the same amount of the operating liquid. A comparison was performed to determine the best in terms of coefficient of heat transfer of the operating liquid, mass flow rate of the operating liquid, pressure drop, and water temperature in the storage tank, as a thermal performance indication of the system under study. The findings show the model consisting of a straight tube inside the riser pipe provides the best thermal performance. In terms of thermal performance, the straight model outperforms the conventional model by 12.3%. An experimental and numerical comparison between the optimum model (straight model) was conducted. The study proves that the average difference between numerical results and experimental findings is 7.2%.

Experimentally Investigating the Flat Plate Solar Water Heating System (FPSWHS) for South Indian Climate

The heat transfer performance of a flat plate solar water heating system was investigated experimentally in this paper (FPSWHS). The main objective of this investigation is to analyze the behaviour of FPSWHS with a 1.5 m2 receiver surface area in South Indian weather conditions and to calculate the heat energy created by the receiver for residential usages, which lessens electricity usage and assists the nation in conserving energy acquired from carbon fuels. Water was employed as the working medium in this investigation. The trials have been conducted in the first week of March 2021 at 13.0827° North, 80.2707° East. The findings confirmed that the solar thermal system's estimated average efficacy remained 44.3%, and the system's maximum output temperature of water was 67°C.

Exergy and thermoeconomic analyses of serpentine tube flat-plate solar water heaters coated with CuO nanostructures

This study aims to evaluate the effect of cuprous absorber plate coated with copper oxide nanoparticles (CuO NSs) on exergy and economic changes and performance of flat plate collector solar water heater and compare the absorber performance with simple and black painted absorber. For this purpose, three solar water heaters were fabricated with the simple flat copper absorber plate, black painted copper absorber plate, and copper absorber plate coated with CuO NSs. All the three water heaters were tested together under the same conditions. The results revealed the performance of water heaters coated with CuO NSs improved compared to that of water heaters with black and simple copper absorber plates. The efficiency of water heaters coated with nanoparticles improved by 18.8% and 35.8% compared to that of water heaters with black and flat absorber plates, respectively. Analyzing exergy efficiency indicated nanostructures coating on the absorber surface increased absorption of incoming solar radiation and outlet fluid temperature and, consequently, improved exergy efficiency of solar collector by 11.2% compared to matte black absorber. Using solar water heaters coated with nanostructures saved more cost and electricity and shortened the payback period by 0.6 years compared to solar water heaters with simple cuprous absorber.

Thermal Enhancement of Solar Energy Storage Using Phase Change Materials

Solar energy (SE) is a renewable and clean energy source. However, the intensity of solar radiation varies due to seasonal changes, weather conditions, and night and day. Thermal energy storage (TES) has the potential to accumulate energy that can be employed later for various purposes. First of all, this study aimed to improve system efficiency and maintain high water temperature (HWT) for a longer period by utilizing phase change materials to save energy (PCMs). An experimental rig of a flat plate solar water heating system (FPSWHS) with TES based on 17 percent (62 kg) of cylindrical encapsulated paraffin wax type RT42 as a PCM was built. Furthermore, 18 aluminum cylinders were used to increase the surface area of PCM and reduce the time required for charging and discharging PCM. Finally, this research was used to identify a suitable PCM for SWHS based on the climatic conditions in the Erbil-Kurdistan region. Incorporating RT42 in a water-PCM storage tank resulted in electricity savings of up to 4.75 kWh at 50℃ inlet water temperature and 0.1 kg.s-¹ mass flow rate, with a total system energy savings of 30.2 kWh as the operation time of the electric heater was reduced. According to the final results, system efficiency increased by 25%, and the system's average daily carbon footprint was reduced by 27 kg of CO2.

Effects of Different Target Solar Fractions on Providing Heat Required for Space Heating, Sanitary Hot Water, and Swimming Pool in Iran: A Case Study in Cold Climate

Due to limited fossil fuel resources, population growth, and the need to save energy and prevent the emission of pollutants, solar heating is of great importance as a strategic solution. Due to these cases, in the present work, for the first time, the use of flat plate solar water heaters (SWHs) in Shahrekord located in the cold climate of Iran has been studied. The aim is to supply heating for space, sanitary hot water, and swimming pool of a residential apartment. Also, technical-economic-energy-environmental analyses have been done. Three low, medium, and high solar fraction scenarios have been selected for evaluations, and one-year dynamic analysis has been performed by TSOL 2018 commercial software. The required climatic data have been extracted by Meteonorm 7.3 software. The results showed that in most cases of heat supply, i.e., high solar fraction scenario, the percentage of solar heat supply for sanitary hot water, space heating, and swimming pool is 97.8%, 22.3%, and 44.3%, respectively, and the total solar fraction is 41%. Also, in this case, the release of more than 4 tons of CO2 pollutants has been prevented. Energy balance diagrams for different scenarios showed that 60% of losses are optical and thermal and also the highest rate of losses was related to the swimming pool. The lowest cost of heat generated and the lowest payback time were $ 0.028/kWh and 11.4 years, respectively, which were related to the high solar fraction scenario.

Assessment of the performance of solar water heater: an experimental and theoretical investigation

Abstract This study aims to evaluate the performance of a flat plate solar water heater (SWH) theoretically and experimentally. The thermal performance of the SWH was predicted using Fortran 90 programming language. SWH was designed as a square shape with dimensions of 110 cm length, 120 cm width and 10 cm depth and tested by integrating with a modified solar distiller to increase the water temperature in the basin at a constant mass flow rate of 1.2 l/min. The tests were conducted under the weather condition of Yekaterinburg city, Russia, from June to September of 2019, and a typical day was chosen for each month (19 June, 17 July, 22 August and 15 September). The study revealed that the highest efficiency of the solar water collector obtained at the highest value of the intensity of solar radiation at mid-day. The maximum thermal efficiencies achieved on 17 July of 2019 were ~67% and 66% based on theoretical and experimental analyses, respectively. A simultaneous increase in the water temperature and the intensity of solar radiation has been observed. During the four typical days of the experiment, the highest water temperatures of the solar collector were recorded during midday, i.e. $57.2{}^{\circ}\mathrm{C},64.4{}^{\circ}\mathrm{C},52.4{}^{\circ}\mathrm{C}\kern0.5em \mathrm{and}\ 49{}^{\circ}\mathrm{C}$ at the inlet, and $62.8{}^{\circ}\mathrm{C},71{}^{\circ}\mathrm{C},57.4{}^{\circ}\mathrm{C}$ and $53.2{}^{\circ}\mathrm{C}$ at the outlet for 19 June, 17 July, 22 August and 15 September 2019, respectively, while the solar radiation intensities recorded are $957,1022,840\kern0.5em \mathrm{and}\ 723\ \mathrm{W}/{\mathrm{m}}^2$ for the test days.

Study on the performance of a flat plate solar water heater using a hybrid nanofluid

Solar thermal energy-based water heating system is an efficient approach for meeting industrial and household hot water needs. Solar water heater systems rely heavily on the efficacy of the solar collectors. In the present investigation, the impact of using a hybrid nanofluid containing copper oxide (CuO) as well as magnesium oxide (MgO) nanoparticles as the heating absorbing liquid on the operational effectiveness of a flat-plate solar collector-based water heater (FPSH) was examined. The nanomaterials volume proportion have been fixed to 0.2 % (0.1 % CuO nanoparticles and 0.1 % MgO nanoparticles) and the two different rate of flow such as 0.0167 and 0.0334 kg/sec was used. The trials were piloted at the location 27.1767° N, 78.0081° E in North India during April 2021. The findings indicate that using hybrid nanofluid as solar collector circulating fluid boosts the FPSH's performance in contrast to using water. The outlet water temperature as well as efficacy of the system had shown a better improvement with the help of hybrid nanofluid. Further, the hybrid nanofluid with a flow rate of 0.0167 kg/sec improved the FPSH efficacy by 43.3 %.

Experimental study on a hybrid solar photothermic and radiative cooling collector equipped with a rotatable absorber/emitter plate

Taking the frigid outer space as the heat sink, a terrestrial body can cool itself to a sub-ambient temperature via radiative sky cooling (RC) scheme. However, poor seasonal and regional adaptabilities and low cooling power density of the RC technology confine its effective applications only in hot seasons and regions with RC-friendly ambient conditions. Similarly, a solar thermal collector cannot work at night and is of little value when heat is needless. To tackle these challenges, a hybrid solar photothermic and radiative cooling (PT-RC) collector equipped with a rotatable absorber/emitter panel is proposed and experimentally investigated. This dual-mode collector can flexibly switch between PT and RC to match specific energy demands in different scenarios. The daily solar thermal efficiency of the PT-RC system at zero-reduced temperature reached 50.4%, a typical level of flat-plate solar water heating systems. The PT-RC system could not provide cooling energy during most daytime hours. However, the system could easily achieve nighttime cooling, with the cooling power of the collector decreasing from about 60 to 50 W/m2 as the circulated water being continuously cooled down from around 20 to 12 °C. The average nocturnal cooling power of the PT-RC collector ranged from 30.5 to 57.5 W/m2 in a multi-night RC test. This rotatable PT-RC collector offers a new strategy to flexibly deliver heat and coldness in a renewable and environmental-friendly manner and shows the potential of smart thermal management in buildings, vehicles, agriculture, etc.

Experimental and Numerical Study of Thermal Performance for Flat Plate Solar Water Heater in Najaf

This work presented the numerical and experimental study of the thermal performance of a flat plate collector (FPC). This study focuses on analyzing the performance of (FPC) in the climatic conditions of Najaf and calculating the thermal energy produced by the collector for domestic use, which reduces the electricity consumption that Iraq is witnessing a severe shortage in its supply. Also, various working fluids (water, oil engine, ethylene glycol-water mixture) were tested to determine the best working fluid that improves the collector’s efficiency. The experiments were performed in Najaf, Iraq (32° 2’ N / 44° 18’ E) on January 9, 2019. The simulation study of the (FPC) is performed by COMSOL Multiphasic 5.3 software. The numerical results were validated with experimental results and there was good convergence between them. The results showed that the average daily efficiency of the solar collector (FPC) was 37.17%, and the highest outlet water temperature of the collector was 57.1Co. The collector achieved a useful cumulative useful heat during the day of about 3.3557 MW, this contributes to reducing the use of electricity and achieving the required economic feasibility of use (FPC). Finally, the engine oil gave better results in improving efficiency compared to other working fluids.

Cradle-to-grave life cycle assessment of an air to water heat pump: Case study for the Lebanese context and comparison with solar and conventional electric water heaters for residential application

This study investigates the environmental performance of the air source heat pump (ASHP) technology. The life cycle assessment (LCA) methodology is used. An LCA analysis provides a clear understanding of the environmental impacts of a product throughout its life cycle. This paper aims to i) determine and analyze the environmental impacts of the ASHP and ii) compare the impacts of the ASHP with those associated with a flat plate (FP) solar water heater (SWH) and a conventional electric water heater (CEWH). The functional unit is “heating 416,100 L of water to 60 °C”. The software used is SimaPro and the impact assessment method is IMPACT 2002+. Results show that the copper pipes of the ASHP are the highest contributors to 6 out of 15 impact categories for the assembly. Moreover, the refrigerant inside the pump is the highest contributor to ozone layer depletion (90.25%). The life cycle results of the three systems show a large contribution of the use phase to the total life cycle impacts. This leads to a need for improving the refrigerant, the Lebanese electricity grid and if possible changing the material of the heat pump pipes. The comparative LCA proves that the ASHP is the best alternative due to its low power requirement during the use phase: Lebanese households could save 1668.45 kg CO2eq and 16983.25 kg CO2eq by installing an ASHP instead of the solar water heater and the electric water heater, respectively. This work encourages installations of this better alternative across Lebanon's residential sector and in the world in order to mitigate the harm to the environment and further improve the use of renewable energy.