Julie A. Rodiek

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

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.

Solar array reliability in satellite operations

Providing reliable power over the anticipated mission life is critical to all satellites; therefore solar arrays are one of the most vital links to satellite mission success. Solar arrays are exposed to the harshest environment of virtually any satellite component causing a significant amount of documented anomalies. It is clear that solar array reliability is a serious, industry-wide issue. This paper will document a statistical analysis that was undertaken to deduce the factors affecting satellite reliability. Suggestions to improve the reliability of the solar arrays will be included. Solar array reliability is an issue that must be addressed to both reduce costs and ensure continued viability of the commercial and government assets on orbit.

Comparison of solar modeling data to actual PV installations: Power predictions and optimal tilt angles

Solar tracking mechanisms were developed to maximize the energy yield of solar cells. Software models can help predict the optimum tilt angle to point the single axis tracker for maximum energy output for the entire year. We used modeling programs to predict the optimal angle and for this region they do not agree. In 2009 Auburn University designed and built a test structure that allowed us to conduct comparison of these models. There are six test panels, five panels are rotated in a single axis azimuthally at the tilt angles of 20°, 25°, 32° (latitude), 40°, and 50°. Another panel is a fixed control panel facing south at latitude tilt. The system has collected data for over one year. Also data collected at the Lee Countys T.K. Davis Justice Centers 16.6 kW grid-connected solar array system is compared to the performance data to the results of three photovoltaic modeling programs used before and during installation of the system. This research will shed light on the accuracy of modeling programs and discuss reasons behind program results variations.

Accomplishments and objectives of the Stretched Lens Array Technology Experiment (SLATE)

This study presents the design and fabrication of the Stretched Lens Array Technology Experiment (SLATE). SLATE is a radiation-hardened solar array flight experiment to be flown in the Van Allen radiation belts and provide flight validation for the Stretched Lens Array (SLA). TacSat 4 is due to be launched in September, 2009 into a high radiation orbit (700 km × 12,050 km, 63.4°). This orbit will provide valuable solar cell degradation information along with proving flight validation for the Stretched Lens Array. In addition, a photovoltaic curve tracer Data Acquisition System (DAS) prototype was designed and built using a new flexible architecture. This project is part of Phase II of a MDA STTR project entitled, “Radiation-Hardened Stretched Lens Array,” with Entech Solar, Inc.

Stretched lens array: The answer to improving solar array reliability

Solar array anomalies are a serious issue affecting the satellite industry and are responsible for increased insurance premiums and a negative perception. It is well known that the reliability of solar arrays needs to be improved. This can be accomplished through the use of a solar array that is inherently designed to withstand the most common modes of failures. The stretched lens array (SLA) overcomes traditional solar array anomalies and is reliable and affordable. This paper will focus on orbital array failures and approaches to design against such anomalies. Theoretical modeling and SLA ground testing results will be presented to prove the SLAs resistance to arcing, micrometeoroid impact, and radiation exposure along with its ability to support high voltage operation. The SLA can overcome solar array anomalies and improve the reliability and cost affordability of solar arrays.

Solar-powered, modular, emergency/disaster response housing

This paper discusses the use of solar-powered modular housing for nationwide disaster relief. Auburn University has performed a design study that demonstrates its feasibility for a stand-alone power system on 398 ft2 “Katrina Cottages”. As a result of Hurricane Katrina, the concept of a “Katrina Cottage” to house residents temporarily was funded. They are equipped with energy star appliances and quality insulation to minimize heating and cooling requirements. The Park Model 1A comfortably houses up to four people and can be installed anywhere in less than one day with no special site preparation or licensing. Modeling done using PV Design Pro-S and -G and DoEs Energy 10 shows a solid business model and payback time for inclusion of solar power systems on the Park Model 1A Katrina Cottage. This paper discusses energy payback time, stand-alone operation, system effectiveness, and economic viability of the Model 1A equipped with a 2 kW photovoltaic power system and a 32 ft2 solar hot water heating system.

Comparison of Photovoltaic Modeling Analysis and Actual Performance Data of Lee County Justice Center Solar Power Installation Project

This paper will discuss the installation of photovoltaic panels to Lee County’s TK Davis Justice Center (LCJC) in Lee County, Alabama in the city of Opelika. This project consists of installing a 16.6 kW grid-connected solar-powered system that will be used to offset the energy costs of electricity used by the LCJC. The project monitors the performance of the system along with weather and environmental factors. Information gathered through the system’s design, installation, and monitoring provides valuable information concerning photovoltaic alternative energy systems on public facilities. By using different mounting options and tilt angles the project is a learning tool and showcase for potential solar array installations at other facilities. This paper will take the data collected at the Lee County’s T.K. Davis Justice Center 16.6 kW grid-connected solar-powered system and analyze it to find trends and anomalies. The analyses will include performance with insolation, especially early and late in the day, average overall operating efficiency and AC performance. Most importantly it compares the performance data to the results of photovoltaic modeling programs that were used before and during installation of the system. We wish to determine how accurate these modeling programs are and to determine the reasons behind variations between program results. We are also documenting the success story of Alabama’s first State Government sponsored PV energy project. It serves as a model of how local governments can be a leading example of how to increase energy-efficiency, be environmentally friendly, and reduce operational costs over the long-term.

A Liquid Sheet Radiator for a Lunar Stirling Power System

This paper will propose a new lunar based power system consisting of a concentrated sunlight heat source (without detail), a Stirling convertor, and a liquid sheet radiator. Radiative effects are calculated and presented for both a spherical and a planar liquid sheet radiator using the waste heat rejection demands of the 25 kW Stirling convertor. The design of the liquid sheet radiator is evaluated on the effects of dust propagation, system cost, specific power, overall weight, and efficiency.

Data analysis of solar power installation project for Lee County'S T.K. Davis Justice Center

In the spring of 2009, Lee Countys T.K. Davis Justice Center (LCJC) installed a 16.6 kW grid-connected solar-powered system to help offset the energy costs of electricity used by the facility. Detailed analysis of the PV array performance is being executed. Data analysis consists of efficiency with intensity, monthly and yearly performance comparisons of roof and pole arrays with PV modeling simulations, and the effect of weather, temperature, and different orientations on overall performance. This paper will also document the success story of Alabamas first State Government sponsored PV energy project. It can serve as a model of how local governments can be an example of how to increase energy-efficiency, be environmentally friendly, and reduce operational costs over the long-term.

The Feasibility of a Stretched Lens Concentrating Solar Array Direct‐Driving an Electric Thruster

As space exploration continues to be a primary focus of NASA, solar electric propulsion (SEP) becomes a forerunner in the mode of transportation to reach the moon and other planets in our solar system. The Stretched Lens Array (SLA) is a unique ultra‐high‐performance, ultra‐light, cost‐effective photovoltaic concentrator array using refractive concentrator technology. The SLA is capable of high voltage operation and sustainability in a high radiation environment and can be specifically optimized for SEP by the ability to direct‐drive Hall‐effect thrusters. Auburn University has performed a “direct drive” experiment using a high‐voltage (600 Voc) ENTECH SunLine concentrator array powered with multijunction solar cells coupled to a Russian T‐100 Hall Effect Thruster (HET). This appears to be the first time a Hall thruster has been run directly from III–V‐based multi‐junction solar cells and at this high voltage. This paper discusses the set‐up and testing results. Testing includes the inclusion of ENTECH’s ...