Solar Collector Size Research Articles

Study on indoor temperature and thermal performance of a novel solar coupled floor and Kang heating system

Coupled floor and Kang surface heating terminals have significant advantages in meeting the differentiated indoor thermal requirements of Northwest rural dwellings in winter. A novel solar coupling floor and Kang surface heating system is proposed, a mathematical analysis model of thermal performance is established, and experimental validation is carried out. The solar coupling floor and Kang surface heating systems can effectively meet the differing heating requirements of indoor and bedding thermal environment. The solar fraction can reach 59.4 %, showing good energy-saving capability. The solar coupled floor and Kang surface heating system were simulated and optimized. The more suitable scheme is a solar collector size of 7.0 m2 and a water tank capacity of 0.35 m3. This configuration better meets the differing heating requirements of indoor and bedding thermal environment when the nighttime water supplier temperature is inferior to the daytime water supplier temperature. The solar coupling floor and Kang surface heating system has a 20.4 % increase and can recover the payback period in 2.3 years compared with traditional solar heating system. The results of the study support the use of solar energy to enhance the indoor thermal demands of rural dwellings in Northwest China.

Green synthesized clove-treated carbon nanotubes/titanium dioxide hybrid nanofluids for enhancing flat-plate solar collector performance

Green synthesizing carbon-based hybrid nanofluids has the potential to drive innovation in both renewable energy technologies and nanomaterial applications. In this regard, the current experimental work focuses on enhancing the thermal performance of flat-plate solar collectors (FPSCs) using working fluids made of nanocomposite materials via an eco-friendly technique (clove). Conventional methods of synthesizing nanofluids frequently involve using hazardous chemicals, raising concerns about the environment and human health. This experimental work examined the energy efficiency, exergy efficiency, and hydrothermal performance of FPSC using clove-treated carbon nanotubes/titanium dioxide (CT-MWCNTs/TiO2) nanocomposites by the ratio of (60 % to 40 %) dispersed in distilled water (DW). The test conditions were in the following ranges: hybrid nanofluid in different weight concentrations (0.025, 0.05, 0.075, and 0.1 wt%), different flow rates (0.3, 0.6, 0.9, and 1.2 L/min), heat flux intensities (400, 600, 800, and 1000 W/m2) and inlet temperature (30, 35, 40, 45 °C). The experimental results revealed that, the maximum enhancement in the energy efficiency (20.6 %) and exergy efficiency (22.9 %) were achieved at 0.1 wt% and 1.2 L/min, relative to the base fluid. In addition, the solar collector size was reduced by 20.5 % due to using a hybrid nanofluid. To conclude, the hybrid nanofluid outperformed the mono nanofluids regarding overall thermal evaluations. The novel hybrid nanofluids generally showed promising results for managing and conserving energy applications.

Design of a Parabolic Trough Collector Solar Field for a Pilot CO2 Capture Plant from Natural Gas Combined Cycle Power Plant Flue Gas.

A parabolic trough collector solar field was designed to supply the heat needed to regenerate the CO2-rich monoethanolamine in a solar-assisted carbon capture system. Process design modeling was performed for 90% of the CO2 removal from 1% of the flue gas produced by a 255 MWe natural gas combined cycle power plant. Calculations with and without 24 h of thermal energy storage by increasing the solar collector size needed and providing a buffer vessel to store hot heat transfer fluid were performed. A dynamic analysis of the solar field using the hourly solar forecast was performed to investigate how heat transfer fluid mass flow changes during January and June to maintain the desired parabolic solar field outlet temperature needed for CO2 reboiler operation. The calculations provided here present an explicit method to calculate relevant solar field design parameters that can be scaled up and used in solar energy-assisted gas capture processes.

Optimizing solar-assisted industrial heating and cooling system for cost-effective installation

Integrating solar thermal collectors into industrial processes could be a viable way to replace the use of conventional fuels and achieve economic and environmental goals. However, there is a need to consider the detailed dynamic operation of a system with storage on a systematic control scale to fully optimize realistic system performance under variable conditions by minimizing excess energy production and maximizing annual life-cycle cost savings. In this study, we developed a TRNSYS-based dynamic statistical optimization model and evaluated FPC-based solar-assisted heating systems to develop a cost-effective system design for two industries: MOHA soft drinks and Sheba leather factories in the Tigray region, Ethiopia. Three operating loads were compared: process heat, utility heat, and utility heat and chilled water. The optimized designs resulted in significant annual life-cycle cost savings, high solar fractions, and a good margin on temperature trends where solar collector size has a greater impact. Annual cost savings per unit area of solar collector for process and utility heat were in the range of $51–90/m2 for a collector mass flow rate and storage volume of 0.01–0.02 m3/h-m2 and 0.04–0.08 m3/m2, respectively. For the utility heat and chilled water loads, the values were $49/m2 for a mass flow rate of 0.04 m3/h-m2 and a storage volume of 0.07 m3/m2. Thus, the study supports the transient analysis of solar-assisted industrial heat. The case studies have shown that the method provides optimal solutions for the use of solar thermal energy. As investment and financial sourcing remain a priority challenge, the model and case study results could help in decision-making for similar and other production capacities, regions, industries, and solar technologies.

New insights into the scientific configuration of a sheet heating system applied in Chinese solar greenhouse

• The shadow range on the north wall were analyzed though the perspective of solar radiation. • Theoretical basis for the solar collector size and installation position was proposed. • Daily average heat collection per unit collector area is 5.6 MJ/m 2 . • The control system can be regulated flexibly according to the indoor microclimate. • The solar water heating system is cost effective in terms of investment and energy saving. The traditional Chinese solar greenhouse (CSG) cannot meet the overwinter production of warm-season plants in the cold north of China. At present, a sheet heating system on the north wall is often used to solve the problem of low temperature in the CSG. However, there is a lack of a theoretical basis for the design of collectors in current research. To address this problem, a theoretical basis for the collector size and installation position of the system from the perspective of solar radiation was proposed in this study. A sheet heating system on the north wall was installed in a CSG in Beijing, which is a solar water recycling system (SWRS). To evaluate the thermal performance of the SWRS, field tests and theoretical verification were carried out. The results indicated that the minimum nighttime indoor temperature increased by 3.1 ℃ on average. The duration of nighttime indoor temperatures greater than 8.0 ℃ accounts for 80.0% in cold January. When the indoor temperature was the minimum, the indoor, north wall, north roof, south roof and ground temperatures increased by 3.4 °C, 2.0 °C, 1.8 °C, 1.0 °C and 1.9 °C, respectively. The indoor temperature could be maintained above 6.0 °C on continuous overcast days. The tomato yield increased by 34%, and the plant morphological parameters were better than those in the control greenhouse. The results of the economic analysis indicated that the SWRS is cost-effective in terms of investment and energy savings.

Investigation of solar assisted air source heat pump heating system integrating compound parabolic concentrator-capillary tube solar collectors

Solar assisted air source heat pump heating systems are capable of achieving green heating where solar availability essentially affects its operation performance and application potentials, especially in higher-latitude regions, such as UK. Compound parabolic concentrator solar collectors can achieve high collector efficiency at high hot water temperature, benefitting to improve solar collection and corresponding thermal energy storage capacities. Though compound parabolic concentrator solar collectors have been widely investigated, application of such collector for solar assisted air source heat pump system is not studied yet. The paper reports numerical simulations of solar assisted air source heat pump heating systems that integrate compound parabolic concentrator-capillary tube solar collectors for domestic heating in the UK. The results show that, for the same seasonal performance factor, the size of the concentrated solar collector required is 12 m2 whereas the size of the flat plate solar collector required is 18 m2. This suggests one third reduction in the size of solar collector, significant reduction in cost and convenience for installation. The results also show the potential to further reduce the size of the concentrated solar collector to 9 m2 or less. The high collector efficiency of the compound parabolic concentrator-capillary tube solar collector enables much small size of solar collector, significantly lower cost and convenient for installation and wide rollout of solar assisted air source heat pump heating system to locations where solar irradiance is relatively lower.

Surface Microlenses for Much More Efficient Photodegradation in Water Treatment

The global need for clean water requires sustainable technology for purifying contaminated water. Highly efficient solar-driven photodegradation is a sustainable strategy for wastewater treatment. In this work, we demonstrate that the photodegradation efficiency of micropollutants in water can be improved by ~2-24 times by leveraging polymeric microlenses (MLs). These microlenses (MLs) are fabricated from the in-situ polymerization of surface nanodroplets. We found that photodegradation efficiency ({\eta}) in water correlates approximately linearly with the sum of the intensity from all focal points of MLs, although no difference in the photodegradation pathway is detected from the chemical analysis of the byproducts. With the same overall power over a given surface area, {\eta} is doubled by using ordered arrays, compared to heterogeneous MLs on an unpatterned substrate. Higher {\eta} from ML arrays may be attributed to a coupled effect from the focal points on the same plane that creates high local concentrations of active species to further speed up the rate of photodegradation. As a proof-of-concept for ML-enhanced water treatment, MLs were formed on the inner wall of glass bottles that were used as containers for water to be treated. Three representative micropollutants (norfloxacin, sulfadiazine, and sulfamethoxazole) in the bottles functionalized by MLs were photodegraded by 30% to 170% faster than in normal bottles. Our findings suggest that the ML-enhanced photodegradation may lead to a highly efficient solar water purification approach without a large solar collector size. Such an approach may be particularly suitable for portable transparent bottles in remote regions.

"Optimization of Solar Collector Size to Achieve The Heat Requirement Along Certain Period".(Dept.E)

This paper presents a complete analysis and a numerical application for deducing the optimum solar collector size to satisfy the heat requirement per year for certain estimated life-time of the heating system. Total cost of the heating systems (collector and auxiliary one) is computed for various collectors areas. The collectors area corresponding to the minimum total cost yields the optimum collector size. This goal is very significant since with increasing collector size, the solar contribution will be greater but certain heat collected will wasted if there is no simulataneous demand. On other hand, it is unequivocal that a small collector of only a few square meters would be utilized all year round. Various collector cost functions are assumed to establish its influence on both optimum and maximum collector size beyond which the estimated life-time cost would be more than a conventional one.

Improving crop production in solar illuminated vertical farms using fluorescence coatings

A solar illumination design with fluorescent coatings to change in crop growth in vertical farms was investigated using simulations based on numerical analysis. The fluorescent reflectors were used as part of the lighting system to improve the irradiation for photosynthesis over the shelves. The reflectors were based on optical glass (BK7) embedded with fluorescent pigments (K2SiF6:Mn4+) and were used in the light distribution system to increase crop production by improving spatial light distribution and altering the solar spectrum. The optimum number of shelves was identified for three different latitudes, considering a fixed size of solar collector. It was estimated that introducing fluorescent reflectors to the system could lead to an increase in crop production exceeding 35%.

Designing and Optimizing Heat Storage of a Solar-Assisted Ground Source Heat Pump System in China

The cold accumulation problem can lead to performance degradation of heat pumps. This paper presents the design and optimization of a solar-assisted storage system to solve this issue. A ground source heat pump (GSHP) project was established using the transient system simulation program (TRNSYS) based on a ground heat exchange theoretical model, which was validated by a previously established experiment in Beijing. The Beijing, Harbin, and Zhengzhou regions were used in numerical simulations to represent three typical cities where buildings require space heating (a cold region, a severe cold region, and a hot summer and cold winter region, respectively). System performance was simulated over periods of ten years. The simulation results showed that the imbalance efficiencies in the Beijing, Harbin, and Zhengzhou regions are 55%, 79%, and 38%, respectively. The annual average soil temperature decreases 7.3°C, 11.0°C, and 5.3°C during ten years of conventional GSHP operation in the Beijing, Harbin, and Zhengzhou regions, respectively. Because of the soil temperature decrease, the minimum heating coefficient of performance (COP) values decrease by 23%, 46%, and 11% over the ten years for GSHP operation in these three regions, respectively. Moreover, the simulation data show that the soil temperature would still be decreasing if based on the previous solar energy area calculation method. Design parameters such as the solar collector size are optimized for the building load and average soil temperature in various cold regions. Long-term operation will test the matching rate of the compensation system with the conventional GSHP system. After the system is optimized, the solar collector area increases of 20% in the Beijing region, 25% in the Harbin region, and 15% in the Zhengzhou region could help to maintain the annual average soil temperature balance. The optimized system could maintain a higher annual average COP because of the steady soil temperature. It provides a method for the design of a solar collector area which needs to be determined in the seasonal heat storage solar ground source heat pump system.

Dynamic simulation and parametric analysis of solar assisted desiccant cooling system with three configuration schemes

Evaporative cooling of the dehumidified air in a desiccant cooling system with the aid of solar energy is an attractive energy saving option to cool the process air for air conditioning purposes. This paper is concerned with the dynamic simulation and performance analysis of three configuration schemes of a solar-based ventilation mode desiccant cooling system energized by a photovoltaic-thermal (PV/T) solar collector for the weather conditions of Lahore (31.52°N, 74.36°E). In configuration-1 (C-1), the auxiliary heater is installed in the air conditioning loop to heat the return air up to the desired regeneration temperature. In configuration-2 (C-2), the auxiliary heater is installed in the solar heating loop to raise the temperature of the liquid water to a certain elevated temperature. The configuration-3 (C-3) is similar to C-2 except there are no evaporative coolers and all the cooling is achieved via conventional vapor compression chiller. The primary energy savings, solar fraction, and the thermal efficiency of the solar collector are the energetic performance parameters which are used to compare the performance of three configuration schemes and to analyze the influence of various parameters such as regeneration temperature, solar collector size and tilt, flow rates, and storage volume. The simulation results demonstrated that the C-1 scheme performs best in terms of solar fraction and primary energy savings while C-3 schematic resulted in the least values of primary energy savings.

On-demand dynamic performance of a thermal battery in tankless domestic solar water heating in the tropical region

This paper reports an experimental investigation of a new design of solar water heater (SWH) employing evacuated tube heat pipe solar collectors (HPSCs) and latent heat storage (LHS) as a thermal battery. In this design, the solar energy incident on the HPSC is collected and stored in the LHS tank via a heat pipe with fins attached to the condenser ends. The stored solar heat is then transferred to the domestic hot water supply via another set of finned-tube heat exchangers located inside the LHS tank. The experimental results of the on-demand performance of the latent heat thermal storage were reported under three different modes, which are weather condition, the daily volume of hot water production, and draw-off starting situation. Results indicated that this design of the thermal battery is able to provide the demanded hot water for households in any weather condition in a tropical climatic region like Malaysia. For a domestic application with solar collector size of about 2 m2, this design can provide at least 112–170 L per day in the worst weather condition. In a fully/partially sunny day, the thermal battery is able to provide much more hot water for domestic demands. It was also found that low thermal conductivity of the Paraffin is useful here, by preventing heat loss of the tank to ambient for long-term heat storage. Therefore, the system is able to provide hot water for the next morning normal usage.

Solar thermal desalination as a nonlinear optical process

The ever-increasing global need for potable water requires practical, sustainable approaches for purifying abundant alternative sources such as seawater, high-salinity processed water, or underground reservoirs. Evaporation-based solutions are of particular interest for treating high salinity water, since conventional methods such as reverse osmosis have increasing energy requirements for higher concentrations of dissolved minerals. Demonstration of efficient water evaporation with heat localization in nanoparticle solutions under solar illumination has led to the recent rapid development of sustainable, solar-driven distillation methods. Given the amount of solar energy available per square meter at the Earth's surface, however, it is important to utilize these incident photons as efficiently as possible to maximize clean water output. Here we show that merely focusing incident sunlight into small "hot spots" on a photothermally active desalination membrane dramatically increases--by more than 50%--the flux of distilled water. This large boost in efficiency results from the nearly exponential dependence of water vapor saturation pressure on temperature, and therefore on incident light intensity. Exploiting this inherent but previously unrecognized optical nonlinearity should enable the design of substantially higher-throughput solar thermal desalination methods. This property provides a mechanism capable of enhancing a far wider range of photothermally driven processes with supralinear intensity dependence, such as light-driven chemical reactions and separation methods.

An experimental study of solar thermal system with storage for domestic applications

Building sector consumes a greater portion of energy for heating and cooling applications. The utilization of fossil fuels for space and water heating in buildings cause a negative effect on the environment by producing larger CO2. In this study solar thermal water heating system for building application have been analyzed from the first and second law perspectives of thermodynamics considering various scenarios and water consumption pattern. The solar flat collector is very commonly used to extract energy from sunlight. Therefor energy and exergy efficiency curves for the solar flat collector were presented. The energetic and exergetic values for the system were calculated based on the experimental values for the overall system, the heat exchanger and the pumps using the approach of exergetic product/fuel basis. The greatest and lowest relative irreversibility’s occurred at the solar collector and the heat exchanger with values of 85.73% and 2.45%, respectively, and the system overall exergy efficiency was determined to be 20.28%. The energy and exergy efficiencies of the solar collector were analyzed at three different cases depending on the mass flow rates in the solar collector and the secondary circuit of the system. Three different mass flow rates were applied to the inlet of the secondary circuit to observe the efficiency effect on the solar collector circuit. This study can assist in selecting a proper solar collector and storage size for buildings of various capacity and possible improvement in the design of the system components.

Designing an optimal solar collector (orientation, type and size) for a hybrid-CCHP system in different climates

The purpose of this research is to determine the optimum orientation and size of a solar collector to be integrated with a basic-CCHP system. The basic-CCHP includes an internal combustion engine; absorption chiller and possible auxiliary boiler but the hybrid-CCHP is the basic-CCHP plus a solar collector to provide a portion of the thermal energy demand of the consumer. Maximum rectangle method is used to size the prime mover. Size of other components depends on the engine size and building demands. The building which the hybrid-CCHP is supposed to be designed for is a residential building. The optimum conditions for the solar collector are determined in five different climates, and the privileges of using a hybrid-CCHP system instead of the basic-CCHP system are discussed. Furthermore, the impact of full load and partial load operation of engine on the fuel energy saving ratio (FESR) of the basic-CCHP and hybrid-CCHP is discussed. The results showed that for the hybrid-CCHP more FESR is achieved in partial load operation of engine, on the contrary, for the basic-CCHP the FESR is higher when the engine operates in full load.

Energy Management for Households With Solar Assisted Thermal Load Considering Renewable Energy and Price Uncertainty

In this paper, we investigate the energy scheduling problem for a household equipped with a solar assisted heating, ventilation, and air conditioning, and water heating system in the real-time pricing environment. Our objective is to minimize the electricity cost while maintaining user's thermal comfort requirements. We consider different types of loads with different characteristics, detailed modeling of thermal dynamics, and uncertainty in electricity price and solar energy. The advantage of the proposed design lies in the exploitation of the solar assisted thermal system that can flexibly utilize the energy from the solar source or from the grid during low-price periods to support the home hot water demand, user thermal indoor temperature preference while reducing the electricity cost. We present numerical results to illustrate the effectiveness of our proposed design. Specifically, we show that the proposed design can achieve significant cost saving, allow flexible tradeoff between user comfort tolerance and electricity cost reduction, and efficiently adjust the electricity consumption load profile. We also analyze the influence of solar assisted thermal system factors such as the water tank temperature limit, solar collector size, and weather condition on the achievable cost.

Numerical simulation of solar enhanced natural draft dry cooling tower

A Solar Enhanced Natural Draft Dry Cooling Tower (SENDDCT) is an air-cooled hybrid cooling system that uses solar energy to enhance the cooling efficiency of natural draft dry cooling. In this paper, a three-dimensional numerical analysis was carried out using commercial software ANSYS FLUENT to investigate the effects of the introduction of a partial blockage on the cooling performance of the SENDDCT and to determine the upper limitation of increasing the solar collector size in the SENDDCT design with a fixed area of heat exchangers. In the simulations, the cooling capacities of SENDDCTs with the same geometric and operating parameters, such as the heat-exchanger areas and tower heights, except for different collector sizes and blockage ratios (the ratio of the blocked area to the area offered at the collector outer edge), were evaluated and a comparative analysis was performed. The results showed that for an SENDDCT with fixed heat-exchanger area, the upper limitation of increasing the solar collector size is that corresponding to a blockage ratio reaching 50%, above which the heat dump capacity of the SENDDCT decreases with a further increase in the solar collector size owing to vortices generated at the back of the heat exchangers reducing the effective heat transfer area. In addition, with a distribution of small-unit heat exchangers, this effect can be significantly reduced.

Design of a renewable energy based air-conditioning system

This paper presents the design of a solar-biomass hybrid system for air-conditioning. Three possible overall system configurations were first considered, based on which the most suitable configuration considered for the design. The principles of component selection of a flat plate solar collector with storage, biomass gasifier with boiler, and a LiBr–H2O absorption system has been described, and the design criteria for the proposed system elaborated. The design was to satisfy a cooling load of 4.5kW, and solar to auxiliary heat ratio of at least 0.7. Simulation at various solar collector size and storage tank volume for the weather conditions at Bangkok indicate the most suitable design and specifications for the size/capacity of the solar collector, storage tank, set point temperature of the absorption generator and biomass-gasifier boiler.

Evaluation of solar thermal storage for base load electricity generation

In order to stabilize solar electric power production during the day and prolong the daily operating cycle for several hours in the nighttime, solar thermal power plants have the options of using either or both solar thermal storage and fossil fuel hybridization. The share of solar energy in the annual electricity production capacity of hybrid solar-fossil power plants without energy storage is only about 20%. As it follows from the computer simulations performed for base load electricity demand, a solar annual capacity as high as 70% can be attained by use of a reasonably large thermal storage capacity of 22 full load operating hours. In this study, the overall power system performance is analyzed with emphasis on energy storage characteristics promoting a high level of sustainability for solar termal electricity production. The basic system parameters, including thermal storage capacity, solar collector size, and annual average daily discharge time, are presented and discussed.

Adsorption cooling driven by solar collector: A case study for Tokyo solar data

An analytical investigation has been performed to study the possibility of application of solar cooling for the climatic condition of Tokyo, Japan. Silica gel–water adsorption cooling system has been taken into consideration for the present study and lumped parameter model is used to investigate the performance of the system. Based on the solar radiation data it is found that at least 15 collector (each of 2.415m2) is required to achieve the required heat source temperature (around 85°C) to run the cooling unit. It is also observed that the solar powered adsorption cooling unit provides cooling capacity around 10kW at noon with base run conditions, while the system provides solar COP around 0.3, however, the solar collector size can be reduced by optimizing the cycle time.