Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “PV performance”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Long-term photothermal/humidity testing of photovoltaic module polymer insulations and cover films

The life expectancies of Tedlar and other polymer films considered for use as cover materials in terrestrial photovoltaic (PV) modules were investigated by exposing them for more than 13,000 h on an outdoor test stand and for up to 10,000 h in several accelerated multistress environments. Visual observations and diagnostic analyses of weight and mechanical strength losses were periodically conducted to assess the nature and rate of degradation of mechanical properties and to assess the effects of film thickness and UV stabilizer content. Spectroscopic analyses of pristine and degraded materials linked weight and mechanical property losses to the underlying photothermal/photooxidation chemistry. It is shown that heavy doses of UV stabilizers prolong, while elevated temperatures shorten, the useful life of these materials; humidity plays only a minor role. The most heavily UV-stabilized films are expected to operate usefully in a PV module front-cover application for only five to ten years. The performance of none of the tested films appears consistent with the 20-30 year life goals of the PV industry.

Mon, G.↗
NASA NTRS1993

Space Station Freedom electrical performance model

The baseline Space Station Freedom electric power system (EPS) employs photovoltaic (PV) arrays and nickel hydrogen (NiH2) batteries to supply power to housekeeping and user electrical loads via a direct current (dc) distribution system. The EPS was originally designed for an operating life of 30 years through orbital replacement of components. As the design and development of the EPS continues, accurate EPS performance predictions are needed to assess design options, operating scenarios, and resource allocations. To meet these needs, NASA Lewis Research Center (LeRC) has, over a 10 year period, developed SPACE (Station Power Analysis for Capability Evaluation), a computer code designed to predict EPS performance. This paper describes SPACE, its functionality, and its capabilities.

Hojnicki, Jeffrey S.↗
NASA NTRS2007

Initial Results from the Floating Potential Measurement Unit aboard the International Space Station

The Floating Potential Measurement Unit (FPMU) is a multi-probe package designed to measure the floating potential of the 1nternational Space Station (ISS) as well as the density and temperature of the local ionospheric plasma environment. The role oj the FPMU is to provide direct measurements of ISS spacecraft charging as continuing construction leads to dramatic changes in ISS size and configuration. FPMU data are used for refinement and validation of the ISS spacecraft charging models used to evaluate the severity and frequency of occurrence of ISS charging hazards. The FPMU data and the models are also used to evaluate the effectiveness of proposed hazard controls. The FPMU consists of four probes: a floating potential probe, two Langmuir probes. and a plasma impedance probe. These probes measure the floating potential of the ISS, plasma density, and electron temperature. Redundant measurements using different probes support data validation by inter-probe comparisons. The FPMU was installed by ISS crewmembers, during an ExtraVehicular Activity, on the starboard (Sl) truss of the ISS in early August 2006, when the ISS incorporated only one 160V US photovoltaic (PV) array module. The first data campaign began a few hours after installation and continued for over five days. Additional data campaigns were completed in 2007 after a second 160V US PV array module was added to the ISS. This paper discusses the general performance characteristics of the FPMU as integrated on ISS, the functional performance of each probe, the charging behavior of the ISS before and after the addition of a second 160V US PV array module, and initial results from model comparisons.

Wright, Kenneth H., Jr.↗
NASA NTRS1991

The status of lightweight photovoltaic space array technology based on amorphous silicon solar cells

Ultralight, flexible photovoltaic (PV) array of amorphous silicon (a-Si) was identified as a potential low cost power source for small satellites. A survey was conducted of the status of the a-Si PV array technology with respect to present and future performance, availability, cost, and risks. For existing, experimental array blankets made of commercial cell material, utilizing metal foil substrates, the Beginning of Life (BOL) performance at Air Mass Zero (AM0) and 35 C includes total power up to 200 W, power per area of 64 W/sq m and power per weight of 258 W/kg. Doubling of power per weight occurs when polyimide substrates are used. Estimated End of Life (EOL) power output after 10 years in a nominal low earth orbit would be 80 pct. of BOL, the degradation being due to largely light induced effects (-10 to -15 pct.) and in part (-5 pct.) to space radiation. Predictions for the year 1995 for flexible PV arrays, made on the basis of published results for rigid a-Si modules, indicate EOL power output per area and per weight of 105 W/sq m and 400 W/kg, respectively, while predictions for the late 1990s based on existing U.S. national PV program goals indicate EOL values of 157 W/sq m and 600 W/kg. Cost estimates by vendors for 200 W ultralight arrays in volume of over 1000 units range from $100/watt to $125/watt. Identified risks include the lack of flexible, space compatible encapsulant, the lack of space qualification effort, recent partial or full acquisitions of US manufacturers of a-Si cells by foreign firms, and the absence of a national commitment for a long range development program toward developing of this important power source for space.

Hanak, Joseph J.↗
NASA NTRS2015

Space Environment Testing of Photovoltaic Array Systems at NASA's Marshall Space Flight Center

To successfully operate a photovoltaic (PV) array system in space requires planning and testing to account for the effects of the space environment. It is critical to understand space environment interactions not only on the PV components, but also the array substrate materials, wiring harnesses, connectors, and protection circuitry (e.g. blocking diodes). Key elements of the space environment which must be accounted for in a PV system design include: Solar Photon Radiation, Charged Particle Radiation, Plasma, and Thermal Cycling. While solar photon radiation is central to generating power in PV systems, the complete spectrum includes short wavelength ultraviolet components, which photo-ionize materials, as well as long wavelength infrared which heat materials. High energy electron radiation has been demonstrated to significantly reduce the output power of III-V type PV cells; and proton radiation damages material surfaces - often impacting coverglasses and antireflective coatings. Plasma environments influence electrostatic charging of PV array materials, and must be understood to ensure that long duration arcs do not form and potentially destroy PV cells. Thermal cycling impacts all components on a PV array by inducing stresses due to thermal expansion and contraction. Given such demanding environments, and the complexity of structures and materials that form a PV array system, mission success can only be ensured through realistic testing in the laboratory. NASA's Marshall Space Flight Center has developed a broad space environment test capability to allow PV array designers and manufacturers to verify their system's integrity and avoid costly on-orbit failures. The Marshall Space Flight Center test capabilities are available to government, commercial, and university customers. Test solutions are tailored to meet the customer's needs, and can include performance assessments, such as flash testing in the case of PV cells.

Phillips, Brandon S.↗
NASA NTRS1982

Reliability and performance experience with flat-plate photovoltaic modules

Statistical models developed to define the most likely sources of photovoltaic (PV) array failures and the optimum method of allowing for the defects in order to achieve a 20 yr lifetime with acceptable performance degradation are summarized. Significant parameters were the cost of energy, annual power output, initial cost, replacement cost, rate of module replacement, the discount rate, and the plant lifetime. Acceptable degradation allocations were calculated to be 0.0001 cell failures/yr, 0.005 module failures/yr, 0.05 power loss/yr, a 0.01 rate of power loss/yr, and a 25 yr module wear-out length. Circuit redundancy techniques were determined to offset cell failures using fault tolerant designs such as series/parallel and bypass diode arrangements. Screening processes have been devised to eliminate cells that will crack in operation, and multiple electrical contacts at each cell compensate for the cells which escape the screening test and then crack when installed. The 20 yr array lifetime is expected to be achieved in the near-term.

Ross, R. G., Jr.↗
NASA NTRS2008

Vertical Jump Height is more Strongly Associated with Velocity and Work Performed Prior to Take-off

Vertical jump (VJ) height is commonly used as a measure of athletic capability in strength and power sports. Although VJ has been shown to be a predictor of athletic performance, it is not clear which kinetic ground reaction force (GRF) variables, such as peak force (PF), peak power (PP), peak velocity (PV), total work (TW) or impulse (Imp) are the best correlates. To determine which kinetic variables (PF, PP, PV, TW, and Imp) best correlate with VJ height. Twenty subjects (14 males, 6 females) performed three maximal countermovement VJs on a force platform (Advanced Mechanical Technology, Inc., Watertown, MA, USA). VJ jump height was calculated as the difference between standing reach and the highest reach point measured using a Vertec. PF, PP, PV, TW, and Imp were calculated using the vertical GRF data sampled at 1000 Hz from the lowest point in the countermovement through the concentric portion until take-off. GRF data were normalized to body mass measured using a standard scale (Detecto, Webb City, MO, USA). Correlation coefficients were computed between each GRF variable and VJ height using a Pearson correlation. VJ height (43.4 plus or minus 9.1 cm) was significantly correlated (p less than 0.001) with PF (998 plus or minus 321 N; r=0.51), PP (1997 plus or minus 772 W; r=0.69), PV (2.66 plus or minus 0.40 m (raised dot) s(sup -1); r=0.85), TW (259 plus or minus 93.0 kJ; r=0.82), and Imp (204 plus or minus 51.1 N(raised dot)s; r=0.67). Although all variables were correlated to VJ height, PV and TW were more strongly correlated to VJ height than PF, PP, and Imp. Therefore, since TW is equal to force times displacement, the relative displacement of the center of mass along with the forces applied during the upward movement of the jump are critical determinants of VJ height. PV and TW are key determinants of VJ height, and therefore successful training programs to increase VJ height should focus on rapid movement (PV) and TW by increasing power over time rather than focusing on PF alone.

Bentley, J. R.↗
NASA NTRS1994

Hypervolemia in men from drinking hyperhydration fluids at rest and during exercise

To test the hypothesis that drink composition is more important than drink osmolality (Osm) for maintaining and increasing plasma volume (PV) at rest and during exercise, six men (22-39 yr, 76.84 +/- 16.19 kg, 2.99 +/- 0.45 L/min VO2 peak) each underwent six treatments while sitting for 90 min (VO2 = 0.39 L/min) and then performed upright ergometer exercise for 70 min (VO2 = 2.08 +/- 0.33 1/min, 70% +/- 7% VO2 peak). Drink formulations (10 ml/kg body weight, X = 768 ml) for the sitting period were: P1 (55 mEq Na(+), 365 mOsm/kg H2O), P2 (97.1 mEq Na(+), 791 mOsm/kg), P2G (113 mEqNa(+), 80 ml glycerol, 1,382 mOsm/kg, HyperAde (HA) (164 mEq Na(+), 253 mOsm/kg), and 01 and 02 (no drinking). The exercise drink (10 ml/kg, 768 ml) was P1 for all treatments except 02. Plasma volume at rest increased (p less than 0.05) by 4.7% with P1 and by 7.9% with HA. Percent change in PV during exercise was +1% to +3%0(NS) with HA; -6% to 0% (NS) with P1, P2, P2G, and 01; and -8% to -5% (p less than 0.05) with 02. HyperAde, with the lowest osmolality (253 mOsm/kg), maintained PV at rest and during exercise, whereas the other drinks with lower Na(+) and higher osmolality (365 to 1,382 mOsm/kg) did not. But Performance 1 also increased PV at rest. Thus, drink composition may be more important than drink osmolality for increasing plasma volume at rest and for maintaining it during exercise.

Greenleaf, J. E.↗
NASA NTRS1979

Photovoltaic system criteria documents. Volume 4: Review criteria for photovoltaic applications

Guidelines are provided for the organization, preparation and conduct of program reviews for photovoltaic applications. These criteria apply to all photovoltaic applications. They include, but are not limited to, the following: (1) Conceptual design review; (2) Preliminary design review; (3) Critical design review; and (4) Operational readiness review. Contract goal's and objectives are met through program monitoring for cost, schedule, and performance for both managerial and technical elements for all PV applications activities.

Koenig, John C.↗
NASA NTRS1991

Update on results of SPRE testing at NASA Lewis

The Space Power Research Engine (SPRE), a free-piston Stirling engine with a linear alternator, is being tested at NASA Lewis Research Center as part of the Civilian Space Technology Initiative (CSTI) as a candidate for high capacity space power. Results are presented from recent SPRE tests designed to investigated the effects of variation in the displacer seal clearance and piston centering port area on engine performance and dynamics. The impact of these variations on PV power and efficiency are presented. Comparisons of the displacer seal clearance tests results with HFAST code predictions show good agreement for PV power, but show poor agreement for PV efficiency. Correlations are presented relating the piston midstroke position to the dynamic Delta P across the piston and the centering port area. Test results indicate that a modest improvement in PV power and efficiency may be realized with a reduction in piston centering port area.

Cairelli, James E.↗
NASA NTRS1991

Update on results of SPRE testing at NASA Lewis

The Space Power Research Engine (SPRE), a free-piston Stirling engine with a linear alternator, is being tested at NASA Lewis Research Center as part of the Civilian Space Technology Initiative (CSTI) as a candidate for high capacity space power. Results are presented from recent SPRE tests designed to investigate the effects of variation in the displacer seal clearance and piston centering port area on engine performance and dynamics. The effects of these variations on PV power and efficiency are presented. Comparisons of the displacer seal clearance test results with HFAST code predictions show good agreement for PV power but poor agreement for PV efficiency. Correlations are presented relating the piston mid-stroke position to the dynamic Delta P across the piston and the centering port area. Test results indicate that a modest improvement in PV power and efficiency may be realized with a reduction in piston centering port area.

Cairelli, James E.↗
NASA NTRS1999

Solar Power System Analyses for Electric Propulsion Missions

Solar electric propulsion (SEP) mission architectures are applicable to a wide range of NASA missions including human Mars exploration and robotic exploration of the outer planets. In this paper, we discuss the conceptual design and detailed performance analysis of an SEP stage electric power system (EPS). EPS performance, mass and area predictions are compared for several PV array technologies. Based on these studies, an EPS design for a 1-MW class, Human Mars Mission SEP stage was developed with a reasonable mass, 9.4 metric tons, and feasible deployed array area, 5800 sq m. An EPS was also designed for the Europa Mapper spacecraft and had a mass of 151 kg and a deployed array area of 106 sq m.

Kerslake, Thomas W.↗
NASA NTRS2018

Calculation Method for Predicting AM0 Isc from High Altitude Aircraft Flight Data

High altitude aircraft have been used by by the space photovoltaic (PV) community to determine the Air Mass Zero (AM0) performance of solar cells for over fifty years. Relative to in-space measurement opportunities, these methods are generally cheaper and more readily available. The data obtained, however, must be corrected for residual atmospheric effects. This paper details the correction method currently being used for the calculation of the AM0 short-circuit current (Isc) for photovoltaic devices flown on the NASA ER-2 (Earth Resources-2) calibration platform. This method would also be applicable to any other high altitude method where Isc data is collected over a sufficiently large range of altitudes.

Myers, Matthew G.↗
NASA NTRS2018

Calculation Method for Predicting AM0 Isc from High Altitude Aircraft Flight Data

High altitude aircraft have been used by the space photovoltaic (PV) community to determine the air mass Zero (AM0) performance of solar cells for over fifty years. Relative to in-space measurement opportunities, these methods are generally cheaper and more readily available. The data obtained, however, must be corrected for residual atmospheric effects. This paper details the correction method currently being used for the calculation of the estimated AM0 short-circuit current (Isc) for photovoltaic devices flown on the NASA ER-2 calibration platform. This method would also be applicable to other high altitude methods where Isc data is collected over a sufficiently large range of altitudes. An initial comparison with a four junction (4J) cell flown on the CASOLBA high altitude balloon platform showed an agreement to 0.2%.

AM0↗
NASA NTRS2000

Blood Volume: Importance and Adaptations to Exercise Training, Environmental Stresses and Trauma/Sickness

This paper reviews the influence of several perturbations (physical exercise, heat stress, terrestrial altitude, microgravity, and trauma/sickness) on adaptations of blood volume (BV), erythrocyte volume (EV), and plasma volume (PV). Exercise training can induced BV expansion; PV expansion usually occurs immediately, but EV expansion takes weeks. EV and PV expansion contribute to aerobic power improvements associated with exercise training. Repeated heat exposure induces PV expansion but does not alter EV. PV expansion does not improve thermoregulation, but EV expansion improves thermoregulation during exercise in the heat. Dehydration decreases PV (and increases plasma tonicity) which elevates heat strain and reduces exercise performance. High altitude exposure causes rapid (hours) plasma loss. During initial weeks at altitude, EV is unaffected, but a gradual expansion occurs with extended acclimatization. BV adjustments contribute, but are not key, to altitude acclimatization. Microgravity decreases PV and EV which contribute to orthostatic intolerance and decreased exercise capacity in astronauts. PV decreases may result from lower set points for total body water and central venous pressure, which EV decrease bay result form increased erythrocyte destruction. Trauma, renal disease, and chronic diseases cause anemia from hemorrhage and immune activation, which suppressions erythropoiesis. The re-establishment of EV is associated with healing, improved life quality, and exercise capabilities for these injured/sick persons.

Sawka, Michael N.↗
NASA NTRS1986

Low-background InSb array development

Photovoltaic indium antimonide (PV InSb) detector technology has matured over the past several years to enable a wide variety of applications to use this high-performance detector material to advantage. The operating conditions for most of the applications to date for back-side illuminated PV InSb arrays have encompassed focal plane temperatures ranging from 40 to approximately 95 K, with the majority in the narrower range between 60 and 80 K. Background flux conditions have ranged from 10 to the 10th power ph/sq cm/sec to 10 to the 16th power ph/sq cm/sec, most typically between 10 to the 12th power and 10 to the 14th power ph/sq cm/sec. Appropriately, the array parameters were optimized for maximum performance over these temperature and background ranges. The key parameters which were peaked in this process were the resistance-area product of the detectors and their quantum efficiency. The Space Infrared Telescope Facility (SIRTF) Infrared Array Camera requirements, however, present very low temperature and background operating conditions, plus the need for very high signal to noise ratios. Preliminary analysis indicates that back-side illuminated PV InSb arrays can be optimized for operation under these conditions, and some performance projections will be presented.

Thom, R. D.↗
NASA NTRS1999

The Impact of TRMM on Mesoscale Model Simulation of Super Typhoon Paka

Tropical cyclone Paka formed during the first week of December 1997 and underwent three periods of rapid intensification over the following two weeks. During one of these periods, which initiated early on December 10, Paka's Dvorak-measured windspeed increased from 23 to 60 m/s over a 48-hr period. On December 18, during the last rapid deepening episode, Paka became a supertyphoon with a maximum wind speed of about 80 m/s. In this study, the Penn State/NCAR Mesoscale Model (MM5) with improved physics (i.e., cloud microphysics, radiation, land-soil-vegetation-surface processes, and TOGA COARE flux scheme) and a multiple level nesting technique (135, 45 and 15 km horizontal resolution) will be used to simulate supertyphoon Paka. We performed two runs initialized with Goddard Earth Observing System (GEOS) data sets. The first GEOS data set does not incorporate either TRMM (tropical rainfall measuring mission satellite) or SSM/I (sensor microwave imager) observed rainfall fields into the GEOS's assimilation system while the second one does. Preliminary results show that the MM5 simulated surface pressure deepened by more than 25 mb (45 km resolution domain) in the run initialized with the GEOS data set incorporating TRMM and SSM/I derived rainfall, compared to the one initialized without. However, the track and precipitation patterns are quite similar between the runs. In our presentation, we will show the impact of TRMM rainfall upon the MM5 simulation of Paka at various horizontal resolutions. We will also examine the physical processes associated with initial explosive development by comparing MM5 simulated rainfall and latent heat release. In addition, budget (vorticity, PV, momentum and heat) calculations and sensitivity tests will be performed to examine the upper-tropospheric and SST mechanisms responsible for the explosive development of Paka.

Tao, W.-K.↗
NASA NTRS1985

Photovoltaic array performance and life-cycle cost simulation using new software tools

The three computer models, SAMICS, PVARRAY, and LCP can be used together as a single analytical tool to compare the lifetime economic value of a photovoltaic (PV) array. This evaluation can be used to compare various module and array configurations and the performance characteristics of different module manufacturing technologies.

Daniel, R. E.↗