Sourav Khanna

Explicit Analytical Expression for Solar Flux Distribution on an Undeflected Absorber Tube of Parabolic Trough Concentrator Considering Sun-Shape and Optical Errors

The absorber tube of the parabolic trough receives the concentrated sun-rays only on the portion facing the reflector. It leads to nonuniformity in the temperature of absorber tube. Thus, the material of tube expands differentially and the tube experiences compression and tension in its different parts. It leads to bending of the tube and the glass cover can be broken. The bending can be reduced by (i) reducing the circumferential nonuniformity in absorbers temperature (using material of high thermal conductivity) and (ii) reducing the nonuniformity in solar flux distribution (using appropriate rim angle of trough). In most of the available studies, Monte Carlo Ray Tracing software has been used to calculate the distribution of solar flux and few studies have used analytical approach. In the present work, an explicit analytical expression is derived for finding the distribution of solar flux accounting for the sun-shape and optical errors. Using it, the design calculations can be carried out in significantly lesser time and lesser computational effort. The explicit expression is also useful in validating the results computed by softwares. The methodology has been verified with the already reported results. The effects of optical errors, rim angle, and aperture width of trough on the solar flux distribution and total flux availability for absorber tube have also been studied. From the calculations, it is found that for Schott 2008 PTR70 receiver (absorber tube with 70 mm outer diameter), 126 deg, 135 deg, and 139 deg, respectively, are the appropriate rim angles corresponding to minimum circumferential nonuniformity in solar flux distribution for 3 m, 6 m, and 9 m aperture width of trough. However, 72 deg, 100 deg, and 112 deg, respectively, are the appropriate rim angles corresponding to the maximum solar flux at absorber tube for 3 m, 6 m, and 9 m aperture width of trough. Considering both the circumferential nonuniformity and the total solar flux availability, 100 deg, 120 deg, and 130 deg, respectively, are the best rim angles.

Multiple Phase Change Material (PCM) Configuration for PCM-Based Heat Sinks—An Experimental Study

A small-scale phase change material (PCM)-based heat sink can regulate the temperature of electronics due to high latent-heat capacity. Three different heat sinks are examined to study the effects of PCM combination, arrangement of PCMs in multiple-PCM heat sink, PCM thickness, melting temperature and intensity of heat source on the thermal behavior of heat sink. Results are obtained for the temperature distribution across the heat sink and the PCM melting profile. It is concluded that (i) PCM combination RT50–RT55 increases the thermal regulation period and also reduces the heat sink temperature at the end of the operation, (ii) the RT58–RT47 arrangement slightly reduces the maximum temperature as compared to RT47–RT58, (iii) As PCM thickness increases from 30 mm to 60 mm, the thermal-regulation-period increases by 50 min, (iv) As the PCM melting temperature increases, the thermal-regulation-period and the heat sink temperature increase and (v) The thermal-regulation-period decreases as the power rating increases from 1 to 2 W.

Electricity enhancement and thermal energy production from concentrated photovoltaic integrated with a 3-layered stacked micro-channel heat sink

The thermal effectiveness of three types of heat sink hsssas been investigated experimentally using a flexible kapton heater to simulate the generated heat from a CPV system for various heating loads. The three heat sinks are an air cooled flat aluminum heat sink, an air cooled finned aluminum heat sink and a water cooled 3-layered stacked micro-channel heat sink. It is shown that the temperature of the heater surface is reduced dramatically by using the finned heat sink compared to the flat plate heat sink. Also, the 3-layered stacked micro-channel heat sink is able to reduce the heater surface temperature below 50°C for 5.5W heater power. The work also studies numerically the effect of the 3-layered stacked micro-channel heat sink in a single solar cell receiver for a 500× concentration in enhancing the solar cell electrical efficiency and production of the thermal energy. The study uses a three dimensional modelling approach for real weather conditions. The results show a high solar cell electricity performance.The thermal effectiveness of three types of heat sink hsssas been investigated experimentally using a flexible kapton heater to simulate the generated heat from a CPV system for various heating loads. The three heat sinks are an air cooled flat aluminum heat sink, an air cooled finned aluminum heat sink and a water cooled 3-layered stacked micro-channel heat sink. It is shown that the temperature of the heater surface is reduced dramatically by using the finned heat sink compared to the flat plate heat sink. Also, the 3-layered stacked micro-channel heat sink is able to reduce the heater surface temperature below 50°C for 5.5W heater power. The work also studies numerically the effect of the 3-layered stacked micro-channel heat sink in a single solar cell receiver for a 500× concentration in enhancing the solar cell electrical efficiency and production of the thermal energy. The study uses a three dimensional modelling approach for real weather conditions. The results show a high solar cell electricity pe...

Photovoltaic system integrated with phase change material for South west UK climate

In photovoltaic (PV) cells, a fraction of the incident solar energy is transformed into electrical energy. Most of the part is transformed into heat which elevates the cell temperature resulting in reduced electrical efficiency. A box containing phase change material (PCM) can be attached on the dark side of the PV panel to reduce the operating temperature of the PV which elevates the electrical efficiency. In the current work, a mathematical model is presented for analyzing the electrical and thermal performances of only PV and PV-PCM systems at South West UK. Ansys-Fluent software has been used for carrying out the calculations. The results show that, for the June month at Cornwall, UK (50.17°N, 5.12°W), (a) the integration of PCM box at the back of a roof integrated 4kWp PV system decreases the PV temperature by 20°C near noon, (b) the electrical output is improved from 2.6kW to 2.9kW using PCM near noon and (c) the total daily electrical output is increased from 17.7kWh/day to 18.9kWh/day using PCM.In photovoltaic (PV) cells, a fraction of the incident solar energy is transformed into electrical energy. Most of the part is transformed into heat which elevates the cell temperature resulting in reduced electrical efficiency. A box containing phase change material (PCM) can be attached on the dark side of the PV panel to reduce the operating temperature of the PV which elevates the electrical efficiency. In the current work, a mathematical model is presented for analyzing the electrical and thermal performances of only PV and PV-PCM systems at South West UK. Ansys-Fluent software has been used for carrying out the calculations. The results show that, for the June month at Cornwall, UK (50.17°N, 5.12°W), (a) the integration of PCM box at the back of a roof integrated 4kWp PV system decreases the PV temperature by 20°C near noon, (b) the electrical output is improved from 2.6kW to 2.9kW using PCM near noon and (c) the total daily electrical output is increased from 17.7kWh/day to 18.9kWh/day using PCM.