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Photovoltaic (PV) panels convert a portion of the incident solar radiation into electrical energy and the remaining energy (>70 %) is mostly converted into thermal energy. This thermal energy is trapped within the panel which, in turn, increases the panel temperature and deteriorates the power output as well as electrical efficiency. To obtain high-efficiency solar photovoltaics, effective thermal management systems is of utmost. This article presents a comprehensive review that explores recent research related to thermal management solutions as applied to photovoltaic technology. The study aims at presenting a wide range of proposed solutions and alternatives in terms of design approaches and concepts, operational methods and other techniques for performance enhancement, with commentary on their associated challenges and opportunities. Both active and passive thermal management solutions are presented, which are classified and discussed in detail, along with results from a breadth of experimental efforts into photovoltaic panel performance improvements. Approaches relying on radiative, as well as convective heat transfer principles using air, water, heat pipes, phase change materials and/or nanoparticle suspensions (nanofluids) as heat-exchange media, are discussed while including summaries of their unique features, advantages, disadvantages and possible applications. In particular, hybrid photovoltaic-thermal (PV-T) collectors that use a coolant to capture waste heat from the photovoltaic panels in order to deliver an additional useful thermal output are also reviewed, and it is noted that this technology has a promising potential in terms of delivering high-efficiency solar energy conversion. The article can act as a guide to the research community, developers, manufacturers, industrialists and policymakers in the design, manufacture, application and possible promotion of high-performance photovoltaic-based technologies and systems.

The main aim of this work is to propose an integrated optical, thermal and electrical model to obtain the overall performance of a concentrated photovoltaic-thermal system (CPV/T). Monte Carlo ray-tracing (MCRT) simulations are done to obtain the flux profile on the absorber of a compound parabolic concentrator (CPC) for various angles of incidence. The obtained heat flux is mapped onto the solar cell in the finite volume method (FVM) to obtain its temperature profile. The modelling is done for both glazed and unglazed compound parabolic concentrator-photovoltaic/thermal (CPC-PV/T) systems using uniform (average heat flux) and non-uniform heat flux distribution. The obtained numerical results are compared with experimental results available in the literature. The results show that the prediction is accurate, with a maximum deviation in solar cell temperature of less than 3%. The deviations obtained when using non-uniform heat flux are much less than when using average heat flux. The temperature contours show that the temperature profile of the photovoltaic module obtained by using local non-uniform heat flux is different from the temperature profile obtained by using average heat flux, and these results will have a greater impact when designing a cooling system. The absorbed radiation from the optical analysis and average cell temperature from the thermal analysis are given to the five parameter electrical model of a solar photovoltaic cell to obtain the electrical power output. With the results of the integrated optical-thermal and electrical model, the overall useful power from both glazed and unglazed CPC-PV/T systems is calculated. The results show that the performance of the unglazed CPC-PV/T system is superior to the glazed CPC-PV/T system in terms of electrical and overall system output. This work demonstrates the need for a local heat flux profile and a coupled multi-physics model to accurately predict the performance of a concentrated photovoltaic/thermal (CPV/T) system.

Multi stage solar distillation units are well known for their higher distillate productivity and are capable of fulfilling the potable water requirements of families in remote, rural, and coastal regions. In this article, active multiple stage series flow solar distillation unit has been proposed for desalting saline water and its performance, environmental benefits and economic feasibility were assessed by carrying out 3E (Energy-Environment-Economic) analyses using the developed mathematical model. Better performance was observed for the distillation unit with five distillation stages, two solar collectors connected in parallel configuration and saline water mass flow rate of 135.0 kg/d and 75.0 kg/d, during summer and winter seasons. Low-pressure operation in combination with evaporative cooling of condenser of last stage has enhanced the annual average daily distillate productivity from 12.60 kg/d to 48.80 kg/d. Distillate production was found to drop from 48.80 kg/d to 38.90 kg/d with the increase in salt concentration of saline water from 0 wt% to 10 wt%. Energy payback time of the unit desalting saline water with 5 wt% salt concentration was within 1.0 yr and the unit can mitigate nearly 221.80 tons of CO 2 emission, 1594.73 kg of SO 2 emission and 651.37 kg of NO emission from Indian coal based power plants during its 20 yrs lifespan under 250 clear day operation. Increased salt concentration in saline water reduces the emission mitigation potential and increases the energy payback time of the proposed distillation unit. Distillate production cost was increased by 16.0% for every 5 wt% increase in salt concentration. Amount invested in the unit can be regained with in 3.56 yr irrespective of interest rate for distilled water selling price of 0.06 USD/L (Rs. 3.91/L).

Compound Parabolic Concentrators (CPC) have non-uniform distribution of flux when integrated to a Photovoltaic-Thermal (PVT) module. The non-uniform distribution of flux deteriorates the electrical and thermal performance of the solar panel. To reduce this effect, optimized homogenizers are integrated to CPC of concentration ratio 3X truncated to 2.5X and 2X. The study aims to demonstrate the effect of integration of homogenizer on the electrical performance of the system. Optical simulations carried out for full scale model (1 m × 2 m solar PVT panel area) with homogenizers, referred as Elongated Compound Parabolic Concentrators (ECPC), showed a reduction in the peak local concentration of 55% and 66% for the 2.5X and 2X cases at normal angle of incidence. Optically coupled electrical simulations are carried out, which are further validated using a scaled down prototype tested under solar simulator. The experimental results show peak electrical efficiency of 13.9% (2X) and 13.6% (2.5X) for CPC and 14.1% (2X) and 13.9% (2.5X) for ECPC. Further, benefits of homogenizer are evident near half acceptance angle, when improvement in electrical efficiency by ~23 ± 2% and ~37 ± 2% is observed for ECPC of concentration ratio 2X and 2.5X in comparison to CPCs of similar configuration. In addition, the effect of temperature on electrical performance has also been studied by conducting experiments for actively cooled and uncooled condition. A reduction in 10% electrical efficiency is reported for uncooled condition compared to actively cooled condition.

In the present study, optimization of two parabolic trough solar thermal power plants integrated with thermal energy storage (TES), and fuel backup system (FBS) has been performed. The first plant uses Therminol VP-1 as heat transfer fluid in the solar field and the second plant uses molten salt. The optimization is carried out with solar multiple (SM) and full load hours of TES as the parameters, with an objective of minimizing the levelized cost of electricity (LCOE) and maximizing the annual energy yield. A 4E (energy-exergy-environment-economic) comparison of the optimized plants alongside the Andasol 1 as reference plant is studied. The molten salt plant resulting as the best technology, from the optimization and 4E comparative study has been chosen for the viability analysis of ten locations in Algeria with semi-arid and arid climatic conditions. The results indicate that Andasol 1 reference plant has the highest mean annual energy efficiency (17.25%) and exergy efficiency (23.30%). Whereas, the highest capacity factor (54.60%) and power generation (236.90 GW h) are exhibited by the molten salt plant. The molten salt plant has least annual water usage of about 800,482 m3, but demands more land for the operation. Nevertheless the oil plant emits the lowest amount of CO2 gas (less than 40.3 kilo tonnes). From the economic viewpoint, molten salt seems to be the best technology compared to other plants due to its lowest investment cost (less than 360 million dollars) and lower levelized cost of electricity (LCOE) (8.48 �/kW h). The viability study proposes Tamanrasset, as the best location for erection of a parabolic trough solar thermal power plant with a low LCOE of 7.55 �/kW h, and a high annual power generation (more than 266 GW h). According to the feasibility analysis, the semi-arid and arid Algerian sites are suitable for realization of PTSTPP with integrated TES and FBS, especially the southern locations (19 N-32 N, 8 W-12 E). � 2015 Elsevier Ltd. All rights reserved.

A steady, three-dimensional model considering all the layers of a solar photovoltaic-thermal collector with sheet and tube heat exchanger is developed. The model takes the solar heat loading as the thermal input to estimate the temperature distribution in the collector for variation in incident radiation, ambient temperature, wind velocity, flow rate and inlet water temperature. Based on the numerical results, the parameter that highly influences collector performance is the coolant mass flow rate. For the range of flow rates considered, a maximum efficiency of 93.01% is obtained for 44 LPH. Further, a techno-economic comparison of the photovoltaic-thermal system is made with a photovoltaic system and a flat plate thermal system. The increase in electrical efficiency of the photovoltaic-thermal system is only marginal to that of the photovoltaic system but the overall efficiency of the former is high. The annual cost of energy that the photovoltaic-thermal system can supply is found to be 0.13 USD/kWh from economic analysis.

Artificial Neural Network (ANN) based models for estimation of monthly mean daily and hourly values of solar global radiation are presented in this paper. Solar radiation data from 13 stations spread over India around the year have been used for training and testing the ANN. The solar radiation data from 11 locations (six from South India and five from North India) were used for training the neural networks and data from the remaining two locations (one each from South India and North India) were used for testing the estimated values. The results of the ANN model have been compared with other empirical regression models. The solar radiation estimations by ANN are in good agreement with the actual values and are superior to those of other available models. The maximum mean absolute relative deviation of predicted hourly global radiation tested is 4.07%. The results indicate that the ANN model shows promise for evaluating solar global radiation possibilities at the places where monitoring stations are not established.

This paper presents the design, development and performance characteristics of a low cost solar steam generating system which incorporates recent design and materials innovations of parabolic dish technology. The concentrator is a deep dish of rather imperfect optics, made of silvered polymer reflectors fitted in the aluminum frame of a satellite communication dish. Conventional cavity receivers tend to be inadequate for this concentrator. Semi-cavity and modified cavity receivers, thermally optimised, with the fuzzy focal image have, therefore, been investigated. Preliminary field measurements and cost, as well as performance analyses of the system, indicate a solar to steam conversion efficiency of 70–80% at 450°C and a collector system cost of Rs 8000–9000/m2 (US$1=Rs, 40.0).

The solar gain characteristics of an absorber parallel slab of Transparent Insulation Material placed between the absorber plane and the glass cover of a solar collector/storage system are investigated. The transmittance of the cover system to solar beam radiation is determined by taking into account the absorption and reflection by the slab. The sky and ground diffuse radiation transmittances are computed by a numerical technique. Steady state one dimensional conduction with internal heat generation in the Methyl Methacrylate (MMA) slab is considered to compute the solar gain. The results are compared with such transparent insulation materials as honeycombs, double glazing and single glazing. The honeycomb cover system shows the best performance, characterized by about 12% higher solar gain than the MMA slab.