In this study, an efficient cooling technique for concentrator photovoltaic (CPV) cells is proposed to enhance the system electrical efficiency and extend its lifetime. To do this, a comprehensive three-dimensional conjugate heat transfer model of CPV cells layers coupled with the heat transfer and fluid flow model inside jet impingement heat sink is developed. Four different jet impingement designs are compared. The investigated designs are (A) central inlet jet, (B) Hypotenuse inlet jet, (C) staggered inlet jet, and (D) conventional jet impingement design with side drainage. The effect of coolant flowrate on the CPV/T system performance is investigated. The model is numerically simulated and validated using the available experiments. The performance of CPV system is investigated at solar concentration ratios of 20 and coolant flowrate up to 6000g/min. It is found that increasing the flowrate from 60 g/min to 600 g/min decrease the maximum cell temperature by 31°C for the configuration D while increasing the flowrate from 600 g/min to 6000 g/min reduce the cell temperature by 20.2°C. It is also concluded that at a higher flowrate of 6000g/min, all the investigated configurations relatively achieve better temperature uniformity with maximum temperature differences of 0.9 °C, 2.1 °C, 3.6 °C, and 3.9 °C for configurations A, B, C, and D respectively.

The goal of a recent study was to design, and determine the effectiveness of, a fixed-tilt solar panel module that contains strands of photovoltaic cells, which are rotated by a very small motor to track the sun. The motivation was that such a configuration enjoys the advantage of increased energy collection over static solar panels due to sun tracking ability, while it mitigates some key difficulties associated with stabilizing and rotating bulky panels as current active and passive tracking systems need to do. Most critically, such a module allows the benefits of sun tracking to be reaped by sloped roof panel installations, which at present almost always consist of fixed-tilt solar panels rather than rotating tracking panels. The study’s result is an active tracking system design in a fixed-tilt module configuration that generated over 10% more daily energy typically, during the test period, compared to a static panel, thus substantially offsetting its added complexity and higher initial cost.

Excess temperatures in photovoltaic panels may cause degradation in the panels’ electrical performance in short term. Moreover, photovoltaic cells may be damaged in the long term due to high operating temperatures. Therefore, photovoltaic thermal collectors (PVT)s have been proposed in order to solve these issues. PVT collectors allow the cooling of photovoltaic panels by heat extraction using a working fluid such as water or air. PVT collectors provide higher electrical output than standalone Photovoltaic (PV) panels while occupying a smaller area compared to a single solar thermal and a PV panel for the same capacity. In this study, the performance of a liquid cooled flat PVT collector under the climatic conditions of the United Arab Emirates is going to be investigated. The transient system simulation software (TRNSYS) is used to simulate the PVT system. The PVT system includes the PVT collectors, thermal storage tank, electrical storage, DC/AC inverter, pumps, and controllers. The effect of various design variables on the PVT electrical and thermal output is going to be studied. The design variables are the collector azimuth angle, slope of the collector, volume of the storage tank, and water mass flow rate through the PVT collector. The electrical and thermal outputs of the sized PVT system will be compared to that of a standalone PV panel electrical output and a standalone flat plate collector thermal output. Based on the obtained results, conclusions on the feasibility of using PVT collectors, under the weather conditions of the United Arab Emirates, will be deduced.

The present study introduces fundamental aspects of a novel concentrated photovoltaics (CPV) technology. The technology is based on combining CPV/T receiver along with a solar thermal receiver. The combination is referred to as a High Concentrated Photovoltaic/Thermal - Combined receiver or HCPV/T-CT. The receiver is allocated in lieu of the conventional solar thermal receivers in the solar tower power plant schemes. The plant is designed to generate electricity and thermal energy simultaneously prior to integration with the conventional water desalination plant. The centralized generation in the CPV/T-CT receiver will remarkably simplify the complexity of the conventional solar power plants, and eliminate the piping networks’ energy losses in the CPV/T Dish tracking plants. The viability of the HCPV/T-CT power tower plant has also been investigated by; firstly, designing and simulating the plant performance using the System advisor model (SAM) software, and secondly, designing a prototype receiver and then deriving a mathematical model. The Levelised Cost Of Electricity/Energy (LCOE) was found to be 0.119 $/kWhe and 0.021 $/kWhe for electricity and energy generation, respectively, while the photovoltaic cells temperature maintained below the 90 °C.

The photovoltaic output power is directly proportional to the solar radiation and inversely with the cell temperature. The higher the photovoltaic temperature is, the lower the electrical efficiency is with possible damage to the cell. To improve the electrical efficiency and to avoid the possible damage, a concentrating PV system associated with an effective cooling technique is of great importance. In the present study, a new cooling technique for concentrated photovoltaic (CPV) systems was introduced using various designs of micro-channel heat sinks. The suggested configurations included parallel flow, counter flow single and double layer micro-channels, and single layer flat micro-channel integrated with CPV system. A comprehensive three-dimensional thermo-fluid model for photovoltaic layers integrated with microchannel heat sink was developed. The model was simulated numerically to estimate the solar cell temperature. The numerical results were validated with the available experimental and numerical results. In the meantime, the effects of different operational parameters were investigated such as solar concentration ratio and cooling mass flow rate. Performance analysis of CPV using different microchannel configurations was implemented to determine the average and local solar cell temperature, pumping power, and temperature uniformity. Results indicated that the use of microchannel heat sink was a very effective cooling technique which highly attained temperature uniformity, viz., eliminated the hot spots formation with a significant reduction in the average temperature of CPV. The single layer parallel flow achieved the minimum solar cell temperature while the counter flow attained the most uniform temperature distribution compared with other configurations. Furthermore, the double layer parallel flow microchannel attained the minimum pumping power for a given cooling mass flow rate.

A study of the state of solar energy development in Taiwan has been performed. In this work, general energy use, solar research issues, and solar manufacturing status and applications were surveyed in late 2011. It was found that there are active research efforts underway in a variety of solar technologies, primarily in photovoltaics, and to a limited extent in solar domestic water heating. Significant manufacturing capabilities in photovoltaic cells have developed within the last decade, and this has grown rapidly, such that Taiwan has edged out Germany for the number two spot in the list of top manufacturers. Very little in the line of photovoltaic installations are found on the island, however. Another characteristic in terms of solar water heating manufacturing and application is that not much is found in Taiwan in contrast to what has taken place on the mainland of China. Some government efforts to stimulate the Taiwanese consumer market both in photovoltaics as well as water heating are outlined, but goals for the PV installations seem overly optimistic based upon recent history.

Solar energy will be an important source of energy for a sustainable energy system whether or not it is directly collected (solar thermal, photovoltaics) or indirectly collected (wind, wave, etc). This project focused on increasing the efficiency of the direct conversion of solar energy into electricity, which is also known as photovoltaics (PV). It has long been known that photovoltaic cells perform less efficiently at higher temperatures. In fact, solar modules under concentration are frequently cooled either actively or passively. The current study, however, focused on cooling modules under no concentration. The goal of the current project was to answer the question: Can the energy gained by cooling a photovoltaic module with groundwater be greater than the energy used by the cooling system and is there an economic benefit? A digital simulation of a simple photovoltaic module under groundwater cooling was performed in order to answer the research question. The simulation was performed for Phoenix, AZ and assuming certain control parameters it was found that the overall system produced over 9% more electricity than a system without groundwater cooling. While the groundwater cooled system increased overall electrical production, the economics of the system will also be presented. Recently, an Arizona utility APS introduced time of use pricing for electricity. Because groundwater cooling provides the most benefit during very hot days with high electrical demand, cooling is more economically attractive. A simple economic analysis will be presented including estimated costs of the cooling system and added value of the excess electrical energy produced under different APS rate plans.

Concentrated solar radiation can be utilized to generate electrical power from photovoltaic cells, but it increases the photovoltaic cell temperature. This can lead to a degradation of the cell efficiency and too high of a temperature can damage the cell integrity. This is particularly important in dish and tower systems where a maximum uniform flux may be difficult to achieve. While a variety of approaches have been used to the keep the cells cool, most are based upon removal of heat from the back (opposite to the incident flux) of the cell. This paper reports on an immersion cooling technique for the cells, where a coolant is circulated over the complete cell including the front surface. An analysis is given where the cells are placed in a cylindrical glass tube where a liquid is circulated. The impacts of the various thermal processes that result from this approach are described here. A comparison is made to limited experimental data.

With the increase of the energy crisis and environmental pollution, the solar energy as a clean and renewable energy is paid more attention. The photovoltaic cells are being widely used, and many researchers are studying the light and heat integration of photovoltaic systems (PV/T). PV-water cooling system and PV-SAHP system are all the integration of solar photovoltaic systems and thermal utilization system, which use the solar energy to supply the electric power and space heating or daily hot water. Due to the difference of the equipment installations and application conditions, two systems are different from their system efficiencies. To analyze the system exergy is of great significance, as the energy loss and utilization deficiency can be identified through the exergy analysis, and based on the analyzed results the system efficiency can be improved. Furthermore the system can be optimized by the exergy efficiency calculation. In this paper the exergy values of two systems are analyzed, the energy loss and utilization deficiency are analyzed, and the exergy efficiencies are obtained. The work will be good references for the application and optimization of solar photovoltaic systems and thermal utilization system.

The idea of this study is to investigate possibilities to use sunlight as the main energy source to generate and store electrical energy via different methods and technologies. Several systems consisting of photovoltaics, photoelectrolytic converters and solarthermal reformers in combination with fuel cells have been investigated in terms of efficiency and costs. A simple energetic approach would not account for these different kinds of energy and their differing availabilities (radiant, thermal, chemical, and electrical energy). To consider different forms of energy and compare them in a fair manner, exergy as the useful part of energy (the part that can theoretically be completely converted to work) provides a perfect instrument for dealing with complex energy conversion systems. In this study, four different scenarios have been investigated: Scenario A describes the direct conversion of sunlight to electricity by photovoltaics. The electric power is used in a Polymer Electrolyte Membrane (PEM) electrolyzer to split water to hydrogen which is stored in a pressure tank. A PEM fuel cell converts hydrogen to electricity on demand. Scenario B deals with a photoelectrolytic cell splitting water to hydrogen by solar irradiation combined with a storage tank and a fuel cell. In Scenario C, solar radiation is converted by photovoltaic cells to electricity which is stored in different types of batteries. Scenario D combines a methanol steam reformer heated by solar power with a PEM fuel cell to generate electricity. The reformate gas mixture can be stored at elevated pressure in a gas tank. In contrast to routes A–C, scenario D has two exergy inputs: Solar radiation and chemical exergy in form of methanol as fuel. All systems are analyzed for an average day in July and February in Central California, including a storage device sufficient to store the energy for one week. Scenario D reaches an overall exergetic efficiency of more than 25% in summer at the expense of an additional exergy input in the form of methanol. The exergetic efficiency of scenario C amounts to 10–17% in summer (4–6% in winter) depending on the battery type and scenarios A and B achieve less than 10% efficiency even in summer. The systems of scenarios A and C would cost around $20k–$45k per 1 kW average electricity generation during the day in July. Scenario D leads to significantly lower costs and scenario B is the most expensive design due to the current immaturity of photoelectrolytic devices.

In this paper the feasibility of using photovoltaic cells to reduce electricity generation from fossil fuels in North Cyprus (N. Cyprus) was studied. In this work it is proposed to use photovoltaic systems to power heating and cooling systems (i.e., mainly heat pumps) in household units and it was found that this is economically feasible. It was also discovered that despite the extensive use of solar water heaters in N. Cyprus, the awareness of photovoltaic cells is still very low and few house owners take advantage of its economic and environmental friendliness. It was also observed that PV cells are not widely available in the local market; coupled with the fact that formal awareness of energy friendly electricity means is not well promoted in developing countries. The result of this work shows that about 40% of yearly electricity consumption in N. Cyprus, which is mainly generated from plants using fuel oil no. 6, can be reduced if all household units use PV systems to heat or cool the house depending on the weather conditions. According to the electricity forecast carried out in this paper it was observed that the annual net electricity consumption is expected to increase by 30.65% in the year 2015. This means that the utility company will need to augment its current facilities to accommodate the increment; by expanding its facilities or opting for energy conservation policies. The latter has proved to be inefficient in this part of the world; the former will increase the use of fossil fuel thereby increasing the CO 2 emission. This work also provides economic analysis for PV systems investment for household owners and policies to help increase availability of PV cells in N. Cyprus market.

We present an analysis of combined efficiencies in a coupled photovoltaic/thermal concentrating solar collector. The calculations take into account the drop in efficiency that accompanies the operation of photovoltaic cells at elevated temperatures along with a detailed analysis of the thermal system including all losses. An iterative numerical scheme is described that involves a coupled electro-thermal simulation of the solar energy conversion process. In the proposed configuration losses in the photovoltaic cell due to reduced efficiencies at elevated temperatures and the incident solar energy below the PV bandgap are both harnessed as heat. This thermal energy is then used to run a thermodynamic power cycle. The simulations show that it is possible to optimize the overall efficiency of the system by variation of key factors such as the solar concentration factor, band gap of the photovoltaic material, and the system thermal design configuration.

Dye sensitized solar cells (DSSCs) offer many advantages in comparison to their Si-based counterparts, including lower cost of raw materials, faster manufacturing time, and the ability to be integrated with flexible substrates. Although many advances have been made in DSSC fabrication over recent years, their efficiency remains lower than commercially available Si photovoltaic cells. Here we report improved efficiency of TiO 2 /anthocyanin dye solar cell using aligned arrays of carbon nanotubes (CNTs) as a counter electrode. Dense vertically oriented CNT arrays are grown directly on the counter electrode using microwave plasma chemical vapor deposition and a tri-layer (Ti/Al/Fe) catalyst. The resulting arrays are 30 micrometers in height and have a number density of approximately five hundred million per square millimeter. By directly growing the CNTs on the counter electrode substrate, electrical interface conductance is enhanced. The performance of both as-grown and N-doped (using a nitrogen plasma) CNT arrays is reported. The fabricated DSSCs are tested under AM1.5 light. Increased short circuit current is observed in comparison to graphite and Pt counter electrodes. We attribute this improvement to the large surface area created by the 3D structure of the arrays in comparison to the planar geometry of the graphite and Pt electrodes as well as the excellent electrical properties of the CNTs.

Computer simulation models to accurately predict the electrical performance of photovoltaic modules are essential. Without such models, potential purchasers of photovoltaic systems have insufficient information to judge the relative merits and cost effectiveness of photovoltaic systems. The purpose of this paper is to compare the predictions of a simulation model, developed by Sandia National Laboratories, to measurements from photovoltaic modules installed in a vertical wall fac¸ade in Gaithersburg, MD. The photovoltaic modules were fabricated using monocrystalline, polycrystalline, tandem-junction amorphous, and copper-indium diselenide cells. Polycrystalline modules were constructed using three different glazing materials — 6 mm low-iron glass, 2 mm ethylene-tetrafluoroethylene copolymer (ETFE), and 2 mm polyvinylidene fluoride (PVDF). In order to only assess the simulation model’s ability to predict photovoltaic module performance, measured solar radiation data in the plane of the modules is initially used. Additional comparisons are made using horizontal radiation measurements. The ability of the model to accurately predict the temperature of the photovoltaic cells is investigated by comparing predicted energy production using measured versus predicted photovoltaic cell temperatures. The model was able to predict the measured annual energy production of the photovoltaic modules, with the exception of the tandem-junction amorphous modules, to within 6% using vertical irradiance measurements. The model overpredicted the annual energy production by approximately 14% for the tandem-junction amorphous panels. Using measured horizontal irradiance as input to the simulation model, the agreement between measured and predicted annual energy predictions varied between 1% and 8%, again with the exception of the tandem-junction amorphous silicon modules. The large difference between measured and predicted results for the tandem-junction modules is attributed to performance degradation. Power measurements of the tandem-junction amorphous modules at standard reporting conditions prior to and after exposure revealed a 12% decline. Supplying post-exposure module parameters to the model resulting in energy predictions within 5% of measured values.