Experimental characterization and multi-physics simulation of a triple-junction cell in a novel hybrid III:V concentrator photovoltaic–thermoelectric receiver design with secondary optical element

A lattice-matched monolithic triple-junction Concentrator Photovoltaic cell (InGa(0.495)P/GaIn(0.012)As/Ge) was electrically and thermally interfaced to a Thermoelectric Peltier module. A single optical design secondary lens was bonded to the CPV-TE receiver. The hybrid SILO-CPV-TE solar energy harvesting device was electrically, thermally and theoretically investigated. The electrical performance data for the cell under variable irradiance and cell temperature conditions were measured using the integrated thermoelectric module as both a temperature sensor and as a solid-state heat pump. The cell was electrically characterised under standard test conditions (1000 W/m2 irradiance, 25°C temperature and AM1.5G spectrum) for comparison with literature data. Transient multiphysics simulations in ANSYS CFX 15.0 were carried out to calculate cell temperatures and to determine the short circuit current and temperature coefficient in a scaling law. The optimization was used to determine 15 model parameters for the component sub-cells within the triple-junction cell at STC with a MATLAB scaling law. The root-mean-square error in electrical currents between measurement and simulations was 0.66%

Conceptual design and performance evaluation of a hybrid concentrating photovoltaic system in preparation for energy

Concentrating sunlight and focussing it on smaller sized solar cells increases the device's power output per unit active area. However, this process tends to increase the solar cell temperature considerably and has the potential to compromise system reliability. Adding a heat exchanger system to regulate this temperature rise, can improve the electrical performance whilst simultaneously providing an additional source of low temperature heat. In this study the performance of a low concentrator photovoltaic system with thermal (LCPV/T) extraction was conceptualised and evaluated in depth. An experimental analysis was performed using a first-generation prototype consisting of 5 units of Cross Compound Parabolic Concentrators (CCPC) connected to a heat extraction unit. A bespoke rotating table was used as experimental apparatus to effectively evaluate the optical performance of the system, as a function of its angular positions to replicate the motion of actual sun. Key design performance parameters for the LCPV/T collector are presented and discussed. This work also provides a useful technique to effectively calculate system performance, as a function of the orientation-dependant electrical characterisation parameters data. Finally, a Computational Fluid Dynamics (CFD) model was also applied to investigate the efficacy of the heat exchanger and hence estimate the overall co-generation benefit of using such optimisation techniques on realistic CPV systems. It was highlighted through these simulations that the water flow rate had the potential to be a critical power-generation optimisation criterion for LCPV-T systems. The maximum power output at normal incidence with concentrators and no water flow was found to be 78.4 mW. The system was found to perform with an average electrical efficiency ranging between 10 and 16% when evaluated at five different geographic locations. Experimental analysis of the data obtained showed an increase in power of 141% (power ratio 2.41) compared to the analogous non-concentrating counterpart. For example, in the case of London which receives an annual solar radiation of 1300 kWh/m2 the system is expected to generate 210 kWh/m2. This may reduce further to include losses due to temperature, reflectance/glazing losses, and electrical losses in cabling and inverter by up to 36% leading to an annual power output of 134 kWh/m2 of module

Studying the outdoor performance of organic building-integrated photovoltaics laminated to the cladding of a building prototype

The outdoor dependence of module orientation and diurnal climatic conditions on the performance of Organic Photovoltaics (OPVs) configured for Building Integrated PV (BIPV) arrays is reported. The study focuses upon a Northern European climate and the significance of module orientation upon energy yield across diurnal, seasonal change and climatic conditions are discussed. It is shown that the optimum position of a BIPV facade depends upon season and that a south facing BIPV facade provides the greatest energy yield during winter months. The results also show how west-facing modules can significantly contribute to power generation during peak power periods (5–8 p.m.), which is imperative for balancing energy demand for buildings of the future and in particular supply the energy needs of buildings during peak hours in Northern Europe. Electrical characteristics under standard and part-load conditions were collated from laboratory scale OPV module experimental data and scaled for commercial-size modules in order to simulate BIPV arrays based upon OPVs. The simulated data is compared to experimental data and the closeness shows that BIPV systems based upon OPVs can be accurately simulated prior to installation. The system simulations compare typical energy demand profiles of small commercial buildings and illustrate that OPV arrays show strong potential to be used with excess energy generation for 8 months of the year based upon a 4.22kWp OPV system. Four 4.22kWp OPV systems scenarios have been investigated for (1) the highest annual energy generation, (2) architecturally evenly-spaced around the building (avoiding a North façade), (3) grid-balancing and (4) East-West split. Whilst Scenario 4 shows the lowest overall energy yield over the course of the year, energy production during peak hours is substantially higher than in other scenarios. The options presented show that OPVs are viable to use in BIPVs and can adequately meet the energy demand of a small commercial building during spring, summer and autumn in Norther Europe and can be adapted to end user's needs