Henry W. Brandhorst

Development of the ultra-light stretched lens array

At the last IEEE-PVSC, the new stretched lens array (SLA) concept was introduced. Since that conference, the SLA team has made significant advances in the SLA technology, including component-level improvements, array-level optimization, space environment exposure testing, and prototype hardware fabrication and evaluation. This paper will describe the evolved version of the SLA, highlighting the improvements in the lens, solar cell, rigid panel structure, and complete solar array wing. The near-term SLA will provide outstanding wing-level performance: >180 W/kg specific power, >300 W/sq.m. power density, >300 V operational voltage, and excellent durability in the space environment.

The stretched lens ultralight concentrator array

This paper describes a new type of space photovoltaic array, including test results for the first fully functional prototype panel. The stretched lens array (SLA) is a high-efficiency, ultralight, stowable, folding-blanket concentrator array. A prototype SLA panel has been performance tested at NASA GRC, with results confirming 27.4% net efficiency (375 W/sq.m areal power) under AM0 sunlight at room temperature. Furthermore, the total prototype panel areal mass, including stretched membrane Fresnel lens concentrators, fully assembled triple-junction cell receivers, and graphite cloth composite radiators, was 0.99 kg/sq.m, resulting in a specific power of 378 W/kg at the fully functional panel level. This is the first space solar array panel of any kind to simultaneously achieve over 300 W/sq.m and over 300 W/kg. In addition, the new SLA has been integrated into a relatively mature flexible blanket platform (ABLEs Aurora(R) array), with near-term array-level performance of 300 W/sq.m and 170 W/kg.

Ultralight stretched Fresnel lens solar concentrator for space power applications

A unique ultra-light solar concentrator has recently been developed for space power applications. The concentrator comprises a flexible, 140-micron-thick, line-focus Fresnel lens, made in a continuous process from space-qualified transparent silicone rubber material. For deployment and support in space, end arches are used to tension the lens material in a lengthwise fashion, forming a cylindrical stressed membrane structure. The resultant lens provides high optical efficiency, outstanding tolerance for real-world errors and aberrations, and excellent focusing performance. The stretched lens is used to collect and focus sunlight at 8X concentration onto high-efficiency multi-junction photovoltaic cells, which directly convert the incident solar energy to electricity. The Stretched Lens Array (SLA) has been measured at over 27% net solar-to-electric conversion efficiency for space sunlight, and over 30% net solar-to-electric conversion efficiency for terrestrial sunlight. More importantly, the SLA provides over 180 W/kg specific power at a greatly reduced cost compared to conventional planar photovoltaic arrays in space. The cost savings are due to the use of 85% less of the expensive solar cell material per unit of power produced. SLA is a direct descendent of the award-winning SCARLET array which performed flawlessly on the NASA/JPL Deep Space 1 spacecraft from 1998-2001.

The stretched lens array (SLA) [spacecraft solar power]

At IECEC 2001, this team presented a paper on the new stretched lens array (SLA), including its evolution from the successful SCARLET array on the NASA/JPL Deep Space 1 spacecraft. Since that conference, the SLA team has made significant advances in SLA technology, including component-level improvements, array-level optimization, space environment exposure testing, and prototype hardware fabrication and evaluation. This paper describes the evolved version of the SLA, highlighting recent improvements in the lens, solar cell, photovoltaic receiver, rigid panel structure, and complete solar array wing. In addition to excellent durability in the space environment, the near-term SLA will provide outstanding wing-level performance parameters: 180 W/kg specific power; 300 W/m/sup 2/ power density; 300 V operational voltage; 85% savings in cell area (cm/sup 2//W) and cell-related cost (

The stretched lens array (SLA): a low-risk cost-effective concentrator array offering wing-level performance of 180 W/kg and 300 W/m/sup 2/ at 300 VDC

/W) compared to planar arrays; 9 kW/m/sup 3/ stowed power at launch.

Recent technology advances for the stretched lens array (SLA), a space solar array offering state of the art performance at low cost and ultra-light mass

This work presents a new stretched lens array (SLA), as a concentrator array used in the space environment. The recent improvements in the lens, solar cell, photovoltaic receiver, rigid panel structure, and complete solar array wing are described. In addition to excellent durability in the space environment, the SLA provides outstanding wing-level performance.

Direct-Drive Performance of a T-100 HET Powered by Triple Junction, High-Voltage Concentrator PV Array

The stretched lens array (SLA) is a unique, ultra-light, high-performance space concentrator array. SLA is also modular, scalable, adaptable, and mass-producible. SLA can be configured as either a conventional rigid-panel solar array wing (near term, low risk, conservative), or as a flexible-blanket solar array wing (longer term, higher risk, higher power, higher performance metrics). The SLA concept was introduced in a paper at the 28th PVSC, the initial development of SLA was described at the 29th PVSC, and ground test results from an automatically deploying subscale rigid-panel SLA wing were presented at the 30th PVSC. In the past 1 1/2 years, many important technology advances have been made for SLA. In addition, a long-term technology roadmap has been generated for SLA, showing a path to MW-class arrays with 1,000 W/kg specific power. Recent SLA technology advances and the roadmap to unprecedented performance metrics are described below.

The Stretched Lens Array SquareRigger (SLASR) for Space Power

Auburn University’s Space Research Institute working with Entech Solar, Inc. has been conducting a “direct drive” experiment using a high-voltage (600 Voc), III-V multijunction Entech Solar SunLine concentrator array coupled to a Russian T-100 Hall Effect Thruster. This possibly is the first time III-V-based multi-junction solar cells have been used to run a Hall thruster powered directly at high voltage. This paper will discuss the set-up and testing results. Testing included the addition of Entech Solar’s Stretched Lens Array hardware in a vacuum chamber to measure plume impingement effects at various positions relative to the exhaust axis of the thruster.

Initial results from the TacSat-4 solar cell experiment

For the past three years, our team has been developing, refining, and maturing a unique solar array technology known as Stretched Lens Array SquareRigger (SLASR). SLASR offers an unprecedented portfolio of state-of-the-art performance metrics, including areal power density, specific power, stowed power density, high-voltage capability, radiation hardness, modularity, scalability, mass-producibility, and cost-effectiveness. SLASR is particularly well suited to high-power space missions, including solar electric propulsion (SEP) space tugs, major exploration missions to the Moon and Mars, and power-intensive military spacecraft. SLASR is also very well suited to high-radiation missions, since the cell shielding mass penalty is 85% less for the SLASR concentrator array than for one-sun planar arrays. The paper describes SLASR technology and presents significant results of developments to date in a number of key areas, from advances in the key components to full-scale array hardware fabrication and evaluation. A summary of SLASR s unprecedented performance metrics, both near-term and longer term, will be presented. Plans for future SLASR developments and near-term space applications will also be outlined.

Recent space PV concentrator advances: More robust, lighter, and easier to track

The TacSat-4 spacecraft carries a solar cell experiment characterizing a string of 3 triple-junction 1-sun solar cells and a string of triple junction solar cells under a flexible, linear Fresnel lens providing approximately 6 times solar concentration. TacSat-4 flies in a highly elliptical, four hour orbit, passing through proton and electron radiation belts 12 times per day. The damage to solar cells in this environment is severe. In this paper we examine the solar cell damage rates of the two solar cell strings.