Internally-Heated Thermal and Externally-Cool Photovoltaic Cascade Solar System For The Full Solar Spectrum Utilization

Technology

This invention incorporates a PV cell and an aerogel-based spectrally-selective thermal absorber/transmitter into a traditional CSP setup. These components are organized in a stacked configuration. This enables the same concentrating optical components to be used for both solar thermal and PV systems, thus reducing the complexity and overall cost of the converter. At an optical concentration of 50 suns and a working fluid temperature of 375°C, the entire system can achieve exergetic efficiencies as high as 70%. At this efficiency, 60% of the exergy is dispatchable heat and 40% is chemical energy stored in the PV cell. When this system is incorporated into a large-scale CSP trough plant, the anticipated price estimate would be lower than 1$/Watt. The layers are ordered as follows: an upper layer of optically transparent and thermally insulating (OTTI) aerogel, a spectrally-selective thermal absorber that heats the CSP working fluid, a lower layer of OTTI aerogel, and a PV cell at the bottom. Solar energy passes through the upper OTTI aerogel layer and into the thermal absorber, which absorbs ultraviolet (UV) and infrared (IR) radiation above and below the PV cell bandgap. The photon energy collected from these frequencies heats the working fluid, which is sandwiched between the UV and IR absorber materials. Photon energy transmitted through this band-pass filter travels through the lower layer of OTTI aerogel and is collected by the PV cell at the bottom. The upper and lower layers of OTTI aerogel suppress radiative thermal losses and insulate the hot region surrounding the working fluid. They also keep the environment surrounding the PV cell near ambient temperature. Aerogel insulation also eliminates the need for traditional vacuum gap insulation, which can extend the lifespan of a CSP trough plant to beyond 25 years. The thermal absorber, comprised of aerogel doped with spectrally-selective nanoparticles, maximizes the efficiency of the PV cell and reduces the cooling required to keep the PV cell at an ambient temperature.    

Problem Addressed

Solar power is currently captured by either photovoltaic (PV) cells, which are relatively efficient, or CSP driven heat engines, which have greater dispatchability and, as a result, the potential to replace traditional base load power sources. Introducing an additional PV cell component to a traditional CSP system would greatly increase exergy output with only a small increase in manufacturing and assembly costs.  

Advantages 

• Low complexity and easy incorporation into pre-existing CSP systems
• Highly dispatchable power generation
• High exergetic efficiency (70%) and low cost of power (<1$/W)
• Reduction of radiative thermal losses and cooling for PV cell
• Increased lifespan of CSP trough plants