SITIS Topic Details |
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| Proposals Accepted: | |
| Program: | STTR |
| Topic Number: | AF10-BT05 (AirForce) |
| Title: | High Efficiency Flexible Photovoltaics | Research & Technical Areas: | Materials/Processes |
| Objective: | The development and integration of high-efficiency photovoltaics into foldable/rollable blankets to reduce solider borne weight by reducing battery requirements.
| Description: | Soldiers currently are forced to carry significant battery loads to accomplish many missions without being resupplied. In addition, unattended devices must often be visited to allow for battery changes. The frequent trips to the unattended devices puts soldiers at risk and can also either compromise the unattended device or identify it as a target. High efficiency flexible solar blankets would allow soldiers to recharge their batteries to enable longer duration missions and soldiers could eliminate battery changeouts for unattended devices. The blankets must be robust, lightweight, and be high efficiency to minimize their detectability.
Amorphous silicon based flexible photovoltaics are currently 6% efficient and optimistic estimates are that this technology can ultimately reach 10% efficiency. Recent advances in inverted metamorphic multi-junction (IMM) photovoltaics have shown efficiencies greater than 30%. IMM photovoltaics are grown upside down on a rigid germanium or gallium arsenide substrate. A secondary carrier is attached to the top surface and the cell is lifted off the substrate. The secondary carrier can be engineered to optimize its properties. For example if the if the substrate is a polymer sheet it would result in high efficiency flexible solar cells. The substrate can also be tuned for optical properties and heat conductivity. The integration of IMM cells into a robust rollable/foldable photovoltaic blankets has not been demonstrated to date. Challenges include electrical connections, encapsulation of the photovoltaic, thermal management, and toughening of the overall system.
The goal of this research is to achieve lightweight flexible photovoltaic blankets with conversion efficiencies greater than 25% and specific power and reliability that are significantly improved compared to existing flexible photovoltaic technologies. Because reducing the mass and maintaining flexibility are key focuses of this topic, solar concentration is not expected to be feasible. Flexible blanket power generation capability should scale from 50 to 1000 Watts with minimal reductions in overall device efficiency. Fully integrated blankets are expected to exceed 125 W/kg specific power under AM 1.5 (air mass) conditions and ambient temperatures. 50 to 250 W blankets should generate 30 V DC.
| PHASE I: Evaluate photovoltaic materials, device design, and processing and integration technology options to achieve flexible blanket conversion efficiencies of >25%. Define specifications and testing protocols for Phase II experimental prototype.
| PHASE II: Apply the designs developed in Phase I to fabricate prototype working photovoltaic blankets at 60-250 scales to demonstrate scalability of cell integration onto flexible photovoltaic blankets. Conduct appropriate tests to demonstrate photovoltaic (electrical) and mechanical performance in a laboratory environment. Conduct detailed experimental and theoretical analysis of system performance.
| PHASE III | DUAL USE COMMERCIALIZATION:
Military Application: Develop flexible photovoltaic blankets for integration into expeditionary and special forces equipment. Blankets will enable longer unsupplied mission lengths due to reduced battery requirements.
Commercial Application: High efficiency flexible photovoltaic civilian applications include solar rechargers for portable power applications, including flexible battery-charging covers for hybrid electric vehicles etc.
| References: |
1. "Monolithic, Ultra-Thin GaInP/GaAs/GaInAs Tandem Solar Cells," M. W. Wanlass, S. P. Ahrenkiel, R. K. Ahrenkiel, D. S. Albin, J. J. Carapella, A. Duda, J. F. Geisz, Sarah Kurtz, T. Moriarty, R. J. Wehrer, and B. Wernsman, Proc. 31st IEEE PVSC, Lake Buena Vista, FL, 1/3 -7/05, IEEE Catalog No. 05CH37608C, ISBN: 0-7803 -8708-2. 2. "40.8% efficient inverted triple-junction solar cell with two independently metamorphic junctions," J. F. Geisz, D. J. Friedman, J. S. Ward, A. Duda, W. J. Olavarria, T. E. Moriarty, J. T. Kiehl, M. J. Romero, A. G. Norman, and K. M. Jones, Appl. Phys. Lett. 93, 123505 (2008). URL: http://link.aip.org/link/?APL/93/123505 <http://link.aip.org/link/?APL/93/123505> 3. "High-efficiency quadruple junction solar cells using OMVPE with inverted metamorphic device structures," M. Stan, D. Aiken, B. Cho, A. Cornfeld, V. Ley, P. Patel, P. Sharps, T. Varghese, J. Crystal Growth (2009), doi:10.1016/j.jcrysgro.2009.10.059. |
| Keywords: | Photovoltaics, power generation, IMM, blanket |
Questions and Answers: |
No questions posed on this topic at this time |
As of midnight September 1, questions for solicitations SBIR 10.3 and STTR 10.B will no longer be accepted.
To read the solicitation for full proposal preparation and submission details click here. |