Hybrid concentrator photovoltaic-thermal (CPV/T) systems generate both electricity and process heat by splitting concentrated sunlight onto CPV cells and a thermal receiver utilizing a heat-transfer fluid. Such energy co-generation increases total conversion efficiency and reduces system costs to compete with more widely used electricity and heat-generation methods in target markets. Here, we design and prototype a sunflower-like CPV/T system that collects a portion of the incoming sunlight using triple-junction CPV cells operating with an average temperature of <85°C. In the same receiver, thermal output >245°C may be generated from both waste heat from the CPV cells and a spatially separated fraction of the incoming concentrated light illuminating a heat-exchanger coil. In total, >65% of incident sunlight is converted to electricity or process heat. On-sun field tests validate this model and guide future development, and a techno-economic model demonstrates a US average levelized cost of heat of 2.5 ¢/kWth.

Hybrid concentrator photovoltaic-thermal systems can cogenerate electricity and heat by beam-splitting incoming concentrated light onto photovoltaic cells and a thermal receiver to increase total conversion efficiency and potentially reduce system cost. To demonstrate this, we have designed and prototyped a transmissive spectrum-splitting concentrator photovoltaic module that maximizes solar energy conversion by utilizing the entire solar spectrum. Visible light is collected using infrared-transmissive triple-junction photovoltaic cells to achieve an in-band module efficiency of 43.3% for light of wavelength lambda < 873 nm, while 44.2% of out-of-band light with lambda > 873 nm is transmitted through for collection by a thermal receiver. During testing on a dual-axis tracked parabolic concentrator dish at up to 166 suns, cell temperatures were maintained at 119 degrees C or below via a novel active cooling method. This cooling system strictly flows silicone oil directly across both sides of the cells, without inhibiting optical transmission, as verified through experimentation and simulation. The module was validated outdoors for 572 sun?hrs, and achieved a maximum thermal receiver temperature of 180 degrees C. 86.1% of incident solar power is collected at 166 suns average concentration collectively among the electrical, cooling, and thermal receiver subsystems. The remaining 13.9% is lost to mirror reflectivity, dish shadowing, receiver reflection, and thermal losses. The ability to directly cool the cells with an inert silicone oil offers the potential for reduced system cost relative to previous transmissive hybrid concentrator photovoltaic-thermal systems, including microfluidic-cooled designs. This solar cogeneration capability is valuable in a wide range of commercial and industrial applications.

A hybrid receiver composed of a concentrator photovoltaic (CPV) module and a thermal receiver is developed for a photovoltaic-solar thermal (CPV/T) cogeneration system. The receiver has the appearance of a flower and is referred to as a sunflower receiver. The unique nature of this design uses both waste heat from the CPV cells and intentional spillage of a large fraction of the concentrated solar energy to generate very high temperature thermal output (up to 250°C) from a single heat transfer fluid, while the temperature of the cells is maintained below 110°C as they convert part of the solar spectrum into electricity. The exit temperature of the heat transfer fluid is adjustable according to the requirements of commercial or industrial process heat application. Early prototype results are discussed.

A spectrum-splitting photovoltaic module is developed for hybrid photovoltaic-solar thermal energy conversion using direct fluid cooling (DFC) of partially transmissive concentrator photovoltaic cells. The waste heat generated in photovoltaic cells can be more efficiently extracted by flowing a heat transfer fluid in direct contact with both sides of the cells. The module also acts as a beam splitter, dividing the incident light into two parts. Photons with higher energy than the bandgap of the cells are absorbed in cells, while photons with lower energy are passed through the infrared-transmissive module to a thermal receiver. Optical modeling (experimental) shows 63.2% (34.3%) out-of-band transmittance through the cell regions and 90.4% (89.0%) full spectrum transmittance through the surrounding bypass region. Thermal modelling verifies the direct cooling fluid method is an effective way to maintain cell temperature <; 110°C. Electrical power conversion efficiency in a first prototype module is 79% of the bare cell efficiency. Fluid flow characterization shows laminar flow. The modules are currently undergoing field testing.