Residential Solar Thermal Performance Considering Self-Shading Incidence between Tubes in Evacuated Tube and Flat Plate Collectors

The performance of solar thermal technology under high-altitude equatorial climatic and solar path conditions has not been determined. Evacuated tube solar collectors are more efficient than flat plate collectors in cold and cloudy regions; however, due to their dependence on orientation, the irradiation incidence between the tubes of these collectors can be blocked. In this study, the performance of these types of collectors was analyzed to determine the implications of their orientation under these specific climate conditions. Four solar thermal systems were installed: two of the systems used evacuated tube collectors, and two used flat plate collectors. Each collector was connected to storage and discharge points to simulate residential consumption when observing the real performance of the four systems in terms of irradiation availability. The evacuated tube collectors were more efficient and reduced the backup energy requirement by up to 20.6% more on average than the flat plate collectors. In addition, the performance of the evacuated tube collectors increased by up to 9.8% when the tubes were arranged parallel to the solar path, compared to when they were arranged perpendicular to the solar path, verifying that the blockage effect is an important parameter to consider for evacuated tube technology. The main novelty of this research is the comparison of these two technologies under different orientations, with perpendicular and parallel dispositions toward the solar path, in a high-altitude equatorial location where solar collectors are not typically oriented in any particular orientation. To the best of our knowledge, this is the first complete analysis of real systems deployed under these conditions.

Performance Evaluation of an Evacuated Tube Collector with a Low-Cost Diffuse Reflector

In order to increase the overall solar energy gain of evacuated tube collectors, rear-side reflectors are used. In this way, the otherwise unused incident radiation between the tubes can be reflected back to the absorber, and the performance of the collector can be improved. In this paper, the use of a low-cost, diffusely reflecting, trapezoidal roof covering made from a galvanized metal sheet is investigated and compared to a high-quality, specularly reflecting plane reflector made of aluminum. For this purpose, ray-tracing analysis and TRNSYS simulations were carried out. In the ray-tracing analysis, the experimentally determined zero-loss collector efficiency η0 as well as the incident angle modifiers for each reflector can be reproduced with an error lower than 7.5%. Thermal system simulations show that the performance of both reflectors is comparable. The use of the low-cost reflector leads to an increase in annual collector output of around 30% compared to an increase with the specular reflector of around 33%. Considering a typical domestic hot water system, both reflectors enable an increase in the solar annual yield of approx. 11%.

Design Optimization and Simulation of an Ice Plant Working by Solar Adsorption Technology

This research presents a design optimization of a solar adsorption ice plant using activated carbon and methanol as working pairs in the climate of Makkah to produce a ton of ice per day. The plant consists of six adsorption refrigeration units. Each unit has 72 separate cylindrical adsorbent beds connected with its own condenser, valve, and evaporator. The unit is heated by seven evacuated-tube collectors connected in parallel. Then the total number of collectors are 42 collectors. The beds are filled by estimated amount of 540 kg of activated carbon with 178 kg of methanol. Selection and dimensioning of each component were carried out based on previous recommended values. A mathematical model and simulation were developed to validate the system performance along the year. The results showed that plant could produce up to ton of ice daily along the year. The coefficient of performance can reach 0.9 with condenser and evaporator temperatures of 35°C and -5°C respectively. The performance of the system is greatly affected by ambient temperature than solar radiation. Therefore, the best performance and largest amount of ice was found in the winter season.

Investigating the Effect of Changing Ratios and Flowrates on Photovoltaic Thermal and Evacuated Tube Collector Array Performance for Different Building Types

Photovoltaic thermal and/or evacuated tube collectors on building roofs can be effectively used to reduce fossil fuel use for heating and reliance on the electrical grid. To evaluate the potential of this reduction, a set of models were created for rooftop photovoltaic thermal and evacuated tube collector energy production, both thermal and electricity, and tested using a series of potential layouts. Five collector area ratios, two layout options, and three working fluid flowrates were investigated using five reference buildings as case studies. From these case studies it was determined that in Toronto’s climate, the exclusive use of photovoltaic thermal collectors produces the most total energy, while using only evacuated tube collectors maximally offsets greenhouse gasses. The results suggest that district heating would be highly effective to reduce the carbon footprint of city cores like the Toronto 2030 District.

Investigating the Effect of Changing Ratios and Flowrates on Photovoltaic Thermal and Evacuated Tube Collector Array Performance for Different Building Types

Photovoltaic thermal and/or evacuated tube collectors on building roofs can be effectively used to reduce fossil fuel use for heating and reliance on the electrical grid. To evaluate the potential of this reduction, a set of models were created for rooftop photovoltaic thermal and evacuated tube collector energy production, both thermal and electricity, and tested using a series of potential layouts. Five collector area ratios, two layout options, and three working fluid flowrates were investigated using five reference buildings as case studies. From these case studies it was determined that in Toronto’s climate, the exclusive use of photovoltaic thermal collectors produces the most total energy, while using only evacuated tube collectors maximally offsets greenhouse gasses. The results suggest that district heating would be highly effective to reduce the carbon footprint of city cores like the Toronto 2030 District.

Evaluating the Performance of Two Solar Domestic Hot Water Systems of the Archetype Sustainable Houses

This thesis is focused on the performance of the two SDHW systems of the sustainable Archetype houses in Vaughan, Ontario with daily hot water consumption of 225 litres. The first system consists of a flat plate solar thermal collector in conjunction with a gas boiler and a DWHR. The second SDHW system consists of an evacuated tube collector, an electric tank and a DWHR. The experimental results showed that the DWHRs were capable of an annual heat recovery of 789 kWh. The flat plate and evacuated tube collectors had an annual thermal energy output of 2038 kWh and 1383 kWh. The systems were also modeled in TRNSYS and validated with the experimental results. The simulated results showed that Edmonton has the highest annual energy consumption of 3763.4 kWh and 2852.9 kWh by gas boiler and electric tank and that the solar thermal collectors and DWHRs are most beneficial in Edmonton.

Evaluating the Performance of Two Solar Domestic Hot Water Systems of the Archetype Sustainable Houses

This thesis is focused on the performance of the two SDHW systems of the sustainable Archetype houses in Vaughan, Ontario with daily hot water consumption of 225 litres. The first system consists of a flat plate solar thermal collector in conjunction with a gas boiler and a DWHR. The second SDHW system consists of an evacuated tube collector, an electric tank and a DWHR. The experimental results showed that the DWHRs were capable of an annual heat recovery of 789 kWh. The flat plate and evacuated tube collectors had an annual thermal energy output of 2038 kWh and 1383 kWh. The systems were also modeled in TRNSYS and validated with the experimental results. The simulated results showed that Edmonton has the highest annual energy consumption of 3763.4 kWh and 2852.9 kWh by gas boiler and electric tank and that the solar thermal collectors and DWHRs are most beneficial in Edmonton.

Effect of Reflecting Material on CPC to Improve the Performance of Hybrid Groundwater Solar Desalination System

Water-energy nexus is a crucial and challenging concern that addressing it is noteworthy for the future of human beings. In addition, freshwater production is a highly energy-intensive procedure. Therefore, developing a suitable solution for this problem is of importance. In the present scenario, solar energy is one of the suitable options for desalination because solar energy is available at a low cost, is clean for the environment, and is widely available. Generally, solar collectors such as flat plate collectors (FPC) and evacuated tube collectors were experimented for desalination applications. This work presents an experimental investigation of a single-stage hybrid (ETC-CPC) groundwater solar desalination system. A compound parabolic concentrator (CPC) is placed below the evacuated tube collector (ETC) for collecting solar radiations to transfer heat to evacuated tubes which improves performance in the case of different weather conditions of Pune city in India. Experimental results show that the hybrid solar groundwater desalination system, by maintaining the optimum distance of 20 mm between ETC and CPC with Mylar as the reflecting material, could offer a drinking water production rate of up to 3.4 l/(m2h)/day. However, the proposed single-stage hybrid (ETC+CPC) groundwater solar desalination system with aluminum foil as a reflecting material could generate 1.9 liters of soft water per day. Further, the use of Mylar as a reflecting material could generate 3.5 liters of soft water per day.

Thermo-Economic Comparisons of Environmentally Friendly Solar Assisted Absorption Air Conditioning Systems

Absorption refrigeration cycle is considered a vital option for thermal cooling processes. Designing new systems is needed to meet the increasing communities’ demands of space cooling. This should be given more attention especially with the increasing conventional fossil fuel energy costs and CO2 emission. This work presents the thermo-economic analysis to compare between different solar absorption cooling system configurations. The proposed system combines a solar field, flashing tank and absorption chiller: two types of absorption cycle H2O-LiBr and NH3-H2O have been compared to each other by parabolic trough collectors and evacuated tube collectors under the same operating conditions. A case study of 200 TR total cooling load is also presented. Results reveal that parabolic trough collector combined with H2O-LiBr (PTC/H2O-LiBr) gives lower design aspects and minimum rates of hourly costs (5.2 $/h) followed by ETC/H2O-LiBr configuration (5.6 $/h). H2O-LiBr gives lower thermo-economic product cost (0.14 $/GJ) compared to the NH3-H2O (0.16 $/GJ). The absorption refrigeration cycle coefficient of performance ranged between 0.5 and 0.9.