Effects of nonuniform incident illumination on the thermal performance of a concentrating triple junction solar cell

PublishedJournal ArticleA numerical heat transfer model was developed to investigate the temperature of a triple junction solar cell and the thermal characteristics of the airflow in a channel behind the solar cell assembly using nonuniform incident illumination. The effects of nonuniformity parameters, emissivity of the two channel walls, and Reynolds number were studied. The maximum solar cell temperature sharply increased in the presence of nonuniform light profiles, causing a drastic reduction in overall efficiency. This resulted in two possible solutions for solar cells to operate in optimum efficiency level: (i) adding new receiver plate with higher surface area or (ii) using forced cooling techniques to reduce the solar cell temperature. Thus, surface radiation exchanges inside the duct and Re significantly reduced the maximum solar cell temperature, but a conventional plain channel cooling system was inefficient for cooling the solar cell at medium concentrations when the system was subjected to a nonuniform light distribution. Nonuniformity of the incident light and surface radiation in the duct had negligible effects on the collected thermal energy. © 2014 Fahad Al-Amri and Tapas Kumar Mallick.This work was supported by King Abdulaziz City for Science and Technology in Saudi Arabia

Experimental comparison of micro-scaled plate-fins and pin-fins under natural convection

This is the final version of the article. Available from the publisher via the DOI in this record.The present work analyses, for the first time, the heat transfer from pin micro-fins. The scope of the present paper is comparing thermal performance of plate micro-fin and pin micro-fin arrays under natural convection conditions in air. Two fin geometries are considered: plate and pin fin arrays with the same thermal exchanging surface are tested. The investigation shows that the pin micro-fins can improve the thermal performance compared to plate micro-fin arrays. Indeed, pin micro-fins are found to have higher heat transfer coefficients and lower thermal resistances, as well as a better material usage. This makes pin micro-fins able to achieve both thermal enhancement and weight reduction. The radiative heat transfer is calculated: a new model to determine the radiative view factors of pin fins is proposed and is used in the analysis. The effect of the orientation is considered as well.The financial support provided by the EPSRC-DST through the BioCPV project (Ref No: EP/J000345/1) is duly acknowledge

Plate Micro-Fins in Natural Convection: Experimental Study on Thermal Effectiveness and Mass Usage

This is the author accepted manuscript. The final version is available from the publisher.International Conference on Polygeneration 2015 (ICP 2015), Chennai, India, 18-20 February 2015Every year, micro-technologies are gaining more attention among researchers and industries. Although they are already applied for cooling purposes in several installations, the researches on the thermal performance of micro-fins in natural convective conditions are yet limited. The correlations between heat transfer coefficients and geometry have already been investigated. The present study merges the results of an original experimental investigation with the data available in literature, in order to give an overview of the behavior of micro-fins in terms of different heat sink metrics: the fin effectiveness and the mass specific heat transfer coefficient. The introduction of micro-fins is found not to be always beneficial in terms of heat transfer, although always positive in terms of the material usage and can be considered advantageous in those applications that requires a minimized weight of the heat sinks.The financial support provided by the EPSRC-DST through the BioCPV project is duly acknowledged

Plate micro-fins in natural convection: an opportunity for passive concentrating photovoltaic cooling

This is the final version of the article. Available from Elsevier via the DOI in this record.70th Conference of the Italian Thermal Machines Engineering Association, ATI2015The raise in temperature is a non-negligible issue for concentrating photovoltaics (CPV), where the sunlight is concentrated up to thousands of times and a large amount of heat is collected on the solar cells. Micro-fins have been identified as one of the most promising solution for CPV cooling: despite its potentials, the number of publications on this subject is still limited. The present paper resumes the state-of-the-art of the research on micro-fins, in order to identify the most convenient fin geometry for CPV applications. The results of the investigation conducted in this work show that, compared to a conventional heat sink, micro-fins can improve the thermal performance and, at the same time, lower the weight of a system. For this reason, they are particularly beneficial for tracked systems, such as CPV, where a reduced weight means a reduced load for the tracker. The heat transfer coefficients measured through an experimental setup are used to predict the performance of a micro-finned CPV system in natural convection: an optimized fin array is found able to enhance the mass specific power up to 50% compared to an unfinned surface.This work was financially supported by the EPSRC-DST funded BioCPV project (EP/J000345/1)

Experimental evaluation of a membrane distillation system for integration with concentrated photovoltaic/thermal (CPV/T) energy

PublishedConference Proceeding4th International Conference on Advances in Energy Research (ICAER 2013)Results are presented for a concentrated solar photovoltaic and thermal powered membrane distillation (MD) system for seawater desalination. Solar intensity data was input into a mathematical model for the solar energy system and outlet temperature from the energy system was calculated. The MD module was tested for a fluctuating inlet temperature, as would be produced from a solar energy source. A maximum distillate flux of 3.4 l/m2h was recorded, though this did not correspond to the highest inlet temperature. An observed delay in the modules response to the fluctuations in temperature was due to the thermal mass of the MD unit. The conductivity of the distillate was measured to assess the effects of transient operation on the quality of the distillate produced. It was determined that although the quantity and quality of the distillate varied with the fluctuations in power supplied to the module, the effects were not significant enough to rule out the integration of the MD module with solar energy. © 2014 The Authors

Effect of climate on electrical performance of finned phase change material integrated solar photovoltaic

This is the final version. Available on open access from Elsevier via the DOI in this recordIn support of open access research, all underlying article materials (such as data, samples or models) can be accessed upon request via email to the corresponding author.Photovoltaic (PV) cells absorb the incident solar radiation while operation of which, majority part causes heating leading to the hampered electrical efficiency. PVs can be integrated with phase change material (PCM) to maintain cell temperature within desired limits and the effect can be improved by deploying fins. The current work aims at analysing the effect of climate on the electrical performance of finned PCM integrated PV. Modelling of system has been done which has been validated using experimental results. For the study, fins with various spacings, thicknesses and lengths are used. The main conclusions of the study are, (a) for less alterative climate, the improvement in the PV electrical output (using finned PCM) is 9.7%, 10.8%, 11.3%, 11.6% and 11.6% respectively for a spacing of 1 m, 1/2 m, 1/3 m, 1/4 m and 1/5 m. For highly alterative climate, the respective values reduce to 6.6%, 7.6%, 8.1%, 8.4% and 8.4%, (b) for warmer climate, the output increases by 10.1%, 11.3%, 11.8%, 12.1% and 12.1% while for colder climate, it increases only by 5.4%, 6.1%, 6.5%, 6.7% and 6.7%, (c) for windy climate, the power increments are significantly lesser as compared to the other case, (d) climate having higher wind azimuth results in better performance of finned PCM, and (e) for clear sky climate, performance of finned PCM is better.Engineering and Physical Sciences Research Council (EPSRC

Colour properties and glazing factors evaluation of multicrystalline based semi-transparent Photovoltaic-vacuum glazing for BIPV application

This is the final version of the article. Available from Elsevier via the DOI in this record.In support of open access research, all underlying article materials (data, models) can be accessed upon request via email to the corresponding author.Low heat loss vacuum glazing offers high heat insulation for indoor space, which reduces the building's heating energy demand. However, the transparent nature of this glazing allows similar daylight to double glazing that creates discomfort glare. Double pane semi-transparent type photovoltaic (PV) glazing introduces control of solar heat gain, daylight and generates clean electricity. The transparent portion between regularly distributed PV cells allows light penetration. Addition of these two technologies can offer low heat loss PV-vacuum glazing that will control heat loss, heat gain, and daylight and generate renewable power. In this work, two different areas of multicrystalline PV cells were employed to form 35% and 42% transparent PV-vacuum glazing. Spectral characterisation, glazing factor and entering light quality through the transparent part of this PV-vacuum glazing were evaluated. Colour rendering and correlated colour temperature of this glazing were compared with an electrically actuated switchable suspended particle device glazing.This work has been conducted as part of the research project ‘Joint UK-India Clean Energy Centre (JUICE)’ which is funded by the RCUK’s Energy Programme (contract no: EP/P003605/1)

Optimization of finned solar photovoltaic phase change material (finned pv pcm) system

This is the final version. Available on open access from the publisher via the DOI in this recordHeat generation during the operation of the photovoltaic (PV) cell raises its temperature and results in reduced electrical output. The heat produced in the process can be removed by attaching phase change material (PCM) at the back of the PV panel which can contain the PV temperature substantially and increase its efficiency. Fins can be used inside the PCM container to enhance the heat transfer. In literature, it is observed that as soon as PCM is melted completely, the heat extraction rate of PCM reduces which again leads to increase in PV temperature. However, the study carrying out the optimization of Finned-PV-PCM system to keep PV temperature low during operation for different solar irradiance levels is not available in literature. Thus, in the current study, the most suitable depth of PCM container is calculated for different solar irradiance levels. In addition, how it is affected with spacing between successive fins, fin length and fin thickness has been studied. The best fin dimensions are also calculated. The results show that the most suitable depth of PCM container is 2.8 cm for ∑I T = 3 kWh/m 2 /day and 4.6 cm for ∑I T = 5 kWh/m 2 /day for the chosen parameters. The best spacing between successive fins (to keep PV temperature low) is 25 cm, best fin thickness is 2 mm and best fin length is the one when it touches the bottom of the container. PV, PV-PCM and Finned-PV-PCM systems are also compared. For PV-PCM system (without fins), the most suitable depth of PCM container is 2.3 cm for ∑I T = 3 kWh/m 2 /day and 3.9 cm for ∑I T = 5 kWh/m 2 /day.The authors gratefully acknowledge the financial support from EPSRC-DST funded Reliable and Efficient System for Community Energy Solution - RESCUES project (EP/K03619X/1

Speed control of synchronous machine by changing duty cycle of DC/DC buck converter

Global Conference on Energy and Sustainable Development, 2015-02-24, 2015-04-26, Coventry, UKRenewable energies such as wind or solar energy are naturally intermittent and can create technical challenges to interconnected grid in particular with high integration amounts. In addition, if wind or solar is used to supply power to a stand-alone system, continuous power supply will be met only if sufficient energy storage system is available. The global penetration of renewable energy in power systems is increasing rapidly especially wind and solar photovoltaic (PV) systems. Hybrid wind and solar PV generation system becomes very attractive solution in particular for stand-alone applications. It can provide better reliability since the weakness of one system could be complemented by the strength of the other one. When wind energy is integrated into grid, maximum power point tracking control could be used to optimize the output of wind turbine. In variable speed wind turbine, the turbine speed is varied according to the wind speed. This paper presents a comparison between two methods of controlling the speed of a wind turbine in a microgrid namely; Proportional-Integral (PI) control of the tip speed ratio and stored power curve. The PI method provides more controllability, but it requires an anemometer to measure the wind speed. The stored power curve method, however, is easier to implement, but the amount of energy extracted can be less. The system has been modelled using Matlab/Simulink.The work is financially supported by the Government of Oman, which provides a PhD grant for Rashid Al Badwawi. Also, financial support from EPSRC-DST funded RESCUES project (EP/K03619X/1)

Numerical investigation of micro-channel based active module cooling for solar CPV system

PublishedConference Proceeding4th International Conference on Advances in Energy Research 2013, ICAER 2013Concentrating photovoltaic (CPV) technology is one of the fastest growing solar energy technologies achieving higher electrical conversion efficiencies. The increase in temperature of solar CPV cell significantly reduces the performance; the efficiency of a CPV system can be improved by introducing effective thermal management or cooling system. This paper presents the design and numerical analysis of a heat sink based on micro-channels for efficient cooling of a commercial high concentration photovoltaic (HCPV) cell. A combinatory model of an array of micro-channels enclosed in a wide parallel flow channel design is developed. The optimized geometry of the micro-channel heat sink was found by using commercial CFD software ANSYS 13. Based on numerical simulations, it is found that the optimum configuration of micro-channel with 0.5mm width and aspect ratio of 8. The micro-channels provided high heat transfer over heat generations spots and parallel flow channels resulted in lower pressure drop. The temperature rise across the micro-channel is estimated as10K in CPV module of 120 × 120 mm2 and with a pressure drop of 8.5 kPa along a single channel with six such channels in each modules at a flow rate of 0.105 liter/s. © 2014 The Authors