Technology Description

The Pratt & Whitney Rocketdyne (PWR) led team has selected Edwards Air Force Base in Southern California as the venue for this demonstration. The plant features a 200 kWe solar power field on an acre of land and consists of a dozen commercial scale solar tracker units. Each tracker supplies approximately 17.5 kWe of 480 V three phase power to a single step-up transformer that feeds the base electrical grid. A short-duration power-leveling battery system will be included. Detailed electrical performance characterization data along with complete nonrecurring acquisition and recurring operations and maintenance cost data will be collected to support future DoD infrastructure investment decisions.

PWR will develop and execute a comprehensive hardware demonstration and test plan to generate the data that will be used to update existing PWR solar cost and performance optimization models. These models are currently mature based on development for solar-thermal field layout and power optimization, extensive PV optimization for the International Space Station, and a recent small (3.5kWe) high concentrated photovoltaic (HCPV) demonstration of this technology in Huntsville, Alabama.

The HCPV module, manufactured by Semprius, has a concentration ratio of 1100 suns and a demonstrated world record module efficiency of 33.9%. The modules use micro-cells, printed by a proprietary technology, to enable a short optical path and robust totally-passive thermal management with no heat sinks or spreaders. Combined with unique two-stage high efficiency refractive optics, the resulting module geometry is light and thin, enabling reduced cost of materials. The low-temperature thin-film metal interconnects which provides high reliability and enables a capital efficient automated manufacturing process. This high level of power output and low production cost for this module provides the combined economic advantage to more than offset the tracker cost of ownership.

The demonstration system will use modified commercially available dual-axis solar trackers, providing optimum solar alignment with high angular accuracies as tight as 0.1 degrees, allowing for the maximum capture of the solar energy throughout the day. This high accuracy is necessary for HCPV applications in high direct normal irradiance (DNI) regions in providing lowest solar electricity production cost. A full-rated-capacity (approximately 200kWe) short-duration power-leveling lithium ion battery system, manufactured by A123 Systems will be integrated with the solar tracker units to reduce power fluctuations. Although not critical to the HCPV demonstration, successful integration will provide system interface data and experience for application to longer-duration storage systems with HCPV sources or for interfacing with micro grid architectures.