|Acquisition Program: ||DDR&E EPTI|| Objective: ||Develop and demonstrate high-specific power, flexible, electric power generation technologies for DOD terrestrial, near space, and space platforms.
|| Description: ||High efficiency solar cells are needed to reduce solar array mass and stowed volume, and increase specific power, at reduced cost and with quicker design and fielding on demand for DOD missions. Thin-film solar cell (TFSC) technology has high potential to meet a number of future DOD power systems needs. While TFSC efficiencies are low compared to state-of-the-art (SOA) crystalline solar cells, they can be manufactured in large scale on lightweight, flexible substrates at low cost. The primary impediment to market acceptance and wide usage of TFSCs in both terrestrial and space systems is the relatively low efficiency. For space systems, higher efficiency results in smaller arrays which reduce drag and lower the complexity needed for deployment systems. For terrestrial use, higher efficiencies also translate into reduced cost per watt which makes the technology more competitive with other forms of terrestrial power. When integrated into mobile and deployable structures, TFSCs have the potential to provide efficient and reliable mobile electric power generation for military and commercial operations. TFSCs are expected to cost a tenth of today’s SOA multijunction solar cells yet are expected to be 3 to 5 times lighter and can be deposited on flexible substrates. The flexibility and low mass of TFSCs are particularly advantageous because they allow innovative solar array support structures. In particular, thin-film solar arrays and modules could potentially provide much greater stowage efficiency (45-60 W/m3 vs. 10-15 W/m3), much greater specific power (250-500 W/kg vs. 70 W/kg), and much lower cost (~$250/W vs. ~$1000/W) than rigid flat panel solar arrays based on SOA multijunction solar cells. Typical efficiencies for TFSCs are ~9-12 % in manufacturable processes. Development of TFSC technologies, based on, but not limited to, amorphous silicon and copper indium gallium diselenide materials that exhibit significantly higher efficiencies while maintaining low cost, lightweight, and flexibility are sought. Performance degradation caused by environmental factors and durability should also be addressed. Areas of interest include (but are not limited to): (1) increasing conversion efficiency to 15% or greater, (2) implementation of multijunction structures, (3) monolithic integration with development of suitable lightweight substrates, and (4) increasing durability and environmental stability under both, the space and terrestrial environments as well as increasing efficiency in actual operating environments. Increased conversion efficiency over SOA combined with low cost and higher manufacturability will enable high power platforms for space missions and efficient reliable stationary or mobile electric power generation for both military and commercial applications across all DOD services. System level array integration issues should also be considered.
|| ||PHASE I: Design and validate innovative approaches for producing high efficiency thin-film solar cells and their modules with efficiencies 15% or greater (under AM0 solar spectrum or equivalent AM1.5 efficiency) on lightweight substrates and establish feasibility of proposed concepts. The contractor will identify key technical challenges and establish a plan to address and overcome those challenges. The contractor will also develop a Phase II program plan, including (but not limited to) a development of suitable lightweight materials, monolithic integration, and large scale manufacturing. Address space environment concerns (UV radiation, electron and proton radiation, atomic oxygen, space plasma, and thermal cycling).
|| ||PHASE II: Build subscale prototypes of high efficiency TFSC. The prototypes should be functionally tested in representative environments to characterize performance and to assist in developing a Phase II design strategy. Using the results of phase I, design, fabricate, and optimize large area prototypes. The contractor should keep in mind the goal of commercialization of this innovation for the Phase III effort, to which end they should have working relationships with, and support from large-scale manufacturers.
|| ||PHASE III: The technologies developed as a result of the Phase II contract(s) will be applicable to many other military and commercial applications that can benefit from the enhanced capabilities, as well as mass and cost savings associated with this technology.
|| ||PRIVATE SECTOR COMMERCIAL POTENTIAL: The commercial potential for increased performance, thin-film based electric power sources is very high. Commercial satellite vendors are a significant fraction of the space market and are continually looking for ways to reduce system mass, decrease costs, and increase spacecraft reliability and lifetime. Compact and lightweight solar electric power sources for DOD terrestrial operations will also benefit from this technology.
|| References: ||1. P. E. Hausgen, P. Tlomak, J. Merrill, J. E. Granata, and D. Senft, “AFRL Thin Film Solar Cell Development and Upcoming Flight Experiments”, 2nd IECEC, Providence, RI, August 16-19, 2004
2. J. E. Granata, P. Tlomak, P. Hausgen, R. Walters, and S. Messenger, “Thin-Film Photovoltaic Radiation Testing & Modeling for a MEO Orbit (Both long and short abstract),” The 31st IEEE PVSC Lake Buena Vista, FL, 3-7 Jan 05.
|Keywords: ||Solar Electric Power Generation, Space Power, Solar Cells, Thin-Film Solar Cells|