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Shepard, N. F.

Publications and source records attributed to Shepard, N. F..

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Design, fabrication, test, and qualification and price analysis of third generation design solar cell modules

The Block 4 shingle type module makes it possible to apply a photovoltaic array to the sloping roof of a residential building by simply nailing the overlapping hexagon shaped shingles to the plywood roof sheathing. This third-generation shingle module design consists of nineteen series connected 100 mm diameter solar cells which are arranged in a closely packed hexagon configuration to provide in excess of 75 watts/sq m of exposed module area under standard operating conditions. The solar cells are individually bonded to the embossed underside of a 4.4 mm thick thermally tempered piece of glass. An experimental silicone pottant was used as the transparent bonding adhesive between the cells and glass. The semi-flexible portion of each shingle module is a composite laminate construction consisting of an outer layer of FLEXSEAL bonded to an inner core of closed cell polyethylene foam. Silaprene is used as the substrate laminating adhesive. The module design has satisfactorily survived qualification testing program which includes 50 thermal cycles between -40 and +90 C, a seven day temperature-humidity exposure test, and a wind resistance test.

Shepard, N. F.↗
NASA NTRS1978

Development and testing of shingle-type solar cell molecules

The details of a shingle module design which produces in excess of 97 watts/sq m of module area at 1 kW/sq m insolation and at 60 C are reported. This selected design employs a tempered glass coverplate to provide the primary solar cell structural support. The fabrication and testing of a preproduction module of this design has demonstrated that this selected approach will meet the environmental testing requirements imposed by the contract.

Shepard, N. F.↗
NASA NTRS1976

Definition study for photovoltaic residential prototype system

A site evaluation was performed to assess the relative merits of different regions of the country in terms of the suitability for experimental photovoltaic powered residences. Eight sites were selected based on evaluation criteria which included population, photovoltaic systems performance and the cost of electrical energy. A parametric sensitivity analysis was performed for four selected site locations. Analytical models were developed for four different power system implementation approaches. Using the model which represents a direct (or float) charge system implementation the performance sensitivity to the following parameter variations is reported: (1) solar roof slope angle; (2) ratio of the number of series cells in the solar array to the number of series cells in the lead-acid battery; and (3) battery size. For a Cleveland site location, a system with no on site energy storage and with a maximum power tracking inverter which feeds back excess power to the utility was shown to have 19 percent greater net system output than the second place system. The experiment test plan is described. The load control and data acquisition system and the data display panel for the residence are discussed.

Shepard, N. F.↗
NASA NTRS1973

Feasibility study of a 110 watt per kilogram lightweight solar array system

The feasibility of a 10,000 watt solar array panel which has a minimum power-to-mass ratio of 110 watt/kg is discussed. The application of this ultralightweight solar array to three possible missions was investigated. With the interplanetary mission as a baseline, the constraining requirements for a geosynchronous mission and for a manned space station mission are presented. A review of existing lightweight solar array system concepts revealed that changes in the system approach are necessary to achieve the specified 110 watt/kg goal. A comprehensive review of existing component technology is presented in the areas of thin solar cells, solar cell covers, welded interconnectors, substrates and deployable booms. Advances in the state-of-the-art of solar cell and deployable boom technology were investigated. System level trade studies required to select the optimum boom bending stiffness, system aspect ratio, bus voltage level, and solar cell circuit arrangement are reported. Design analysis tasks included the thermal analysis of the solar cell blanket, thermal stress analysis of the solar cell interconnectors/substrate, and the thermostructural loading of the deployed boom.

Shepard, N. F.↗
NASA NTRS1972

Feasibility study of a 110 watt per kilogram lightweight solar array system

An investigation of the feasibility of a solar array panel subsystem which will produce 10,000 watts of electrical output at 1 A.U. with an overall beginning-of-life power-to-weight ratio of at least 110 watt/kg is reported. A description of the current baseline configuration which meets these requirements is presented. A parametric analysis of the single boom, two blanket planar solar array system was performed to arrive at the optimum system aspect ratio. A novel concept for the stiffening of a lightweight solar array by canting the solar cell blankets at a small angle to take advantage of the inherent in-plane stiffness to increase the symmetric out-of-plane frequency is introduced along with a preliminary analysis of the stiffening effect. A comparison of welded and soldered solar cell interconnections leads to the conclusion that welding is required on this ultralightweight solar array. The use of a boron/aluminum composite material in a BI-STEM type deployable boom is investigated as a possible advancement in the state-of-the-art.

Shepard, N. F.↗
NASA NTRS1972

The 110 watt per kilogram lightweight solar array system

This ultralightweight solar array system is applied to three generic mission types: (1) interplanetary, (2) geosynchronous, and (3) manned space station. The requirements of each of these missions, as they pertain to the solar array, are presented. Existing lightweight solar array system concepts are reviewed, along with conclusions regarding the applicability of this technology to the feasibility of the ultralightweight solar array system. Several system concepts are included for further evaluation. The existing technology base, as it pertains to solar cells, solar cell covers, interconnects and substrates, and deployable booms, is reviewed. The attitude control of spacecraft with large flexible solar arrays is also discussed.

Shepard, N. F.↗