Value chain · CLM-1116
In plain terms
Thirty years of radiation behind a hair-thin glass cover was expected to take a third of the cell's power; a cover three times thicker would give about 16 per cent more power after thirty years but weigh twenty thousand tonnes more across the satellite. The design took the thin cover and planned to anneal.
The claim as recorded
Boeing's 1977 degradation analysis puts the 30-year GEO damage fluence for its silicon cell at 6 x 10^15 1-MeV electron equivalents behind a 2-mil (50 um) fused silica cover, falling to 2.7 x 10^15, 1.8 x 10^15, 8.5 x 10^14 and 4.6 x 10^14 behind 3, 6, 12 and 20 mils; extrapolating Comsat's published nonreflective-cell data it takes the 2-mil cell to have "dropped to 63.1 percent of its" original maximum power (the page prints the word as "orih-inal", a typesetting slip), and assumes the 18 per cent cell degrades alike; Table 3.2-10 then gives output after 30 years of 158.2, 174.6, 183.6, 192.7 and 208.9 W/m2 for the five covers, maximum-power voltage at 115 C of 0.297 to 0.328 V, 149,390 to 135,488 cells in series for 44,440 V, and 49.11 to 64.74 MW per 650 by 496 m module; the 2-mil module "generates after 30 years 13.7 percent less power than the module with cells protected by" 6 mils, against "a saving of 20 million kg of mass" on a 100 km2 array, and damage "increases rapidly" once covers are thinned below 50 um.
Evidence behind this: T3-contractor degradation analysis: a stated fluence model, an extrapolation of published 1975 cell data, and a tabulated string design by cover thickness.
Scope and limits
AN EXTRAPOLATION TO 6 x 10^15 OF 1975 DATA, WITH NO TEST OF THE CELL ASSUMED; the report says so. The table's outputs are at 115 C under CR 2 illumination and are not the 1-sun figures of Table 3.2-5. The fluence is a 1977 environment model (Webber's averaged solar-proton data, the report noting that Cycles 22 to 24 had no predictions, PDF 131). Table 3.2-10 prints 18.27 mW/cm2 in the 12-mil column against 192.7 W/m2 in the row beneath, the other four columns agreeing tenfold and the W/m2 row running monotonic; a suspected transcription error in the mW/cm2 cell, the W/m2 row being the one carried here.
What it assumes
Webber's average solar-proton fluence and the TRW electron damage coefficient; Comsat's 1975 nonreflective cell as the proxy for the 1987 cell.
Where it comes from
PDF 137 / printed 132, Table 3.2-10 render read, columns 2, 3, 6, 12, 20 mils: "Fluence after 30 years in geosynchronous orbit 6 x 10^15, 2.7 x 10^15, 1.8 x 10^15, 8.5 x 10^14, 4.6 x 10^14"; "Power output after 30 years (mW/cm2) 15.82, 17.46, 18.36, 18.27, 20.89; W/m2 158.2, 174.6, 183.6, 192.7, 208.9"; "Maximum-power voltage at 115 C (V) 0.297, 0.302, 0.308, 0.318, 0.328"; "Cells in series for 44,440 volts 149,390, 147,153, 144,286, 139,743, 135,488"; "Cells in one string, 4 cells wide 597,560 ..."; "String length (5 + 0.1 cm/cell) (km) 7.62 ... 6.91"; "Power per module (MW) 49.11, 54.05, 56.90, 61.10, 64.74". PDF 135 / printed 130, raw: "nonreflective solar cell with a 2-mil cover has dropped to 63" .1 percent of its original maximum power (render reading of the rest; the page prints "orih-inal"); "1987 solar cells which are predicted to have an efficiency of 18 percent"; the 63.1 per cent assumption sentence and "when covers are thinned below 50 um, the damage increases rapidly" as render readings; the fluence basis (Webber's average solar-proton fluence, TRW handbook electron coefficient) on PDF 131. PDF 138 / printed 133, normalised: "generates after 30 years 13.7 percent less power than the module with cells protected by" 150 um; raw: "a saving of 20 million kg of mass"; normalised: "the thinner covers represent in a 100" km2 satellite. Recomputed: 44,440 / 0.2975 = 149,378 (printed 149,390); 4 x 149,390 = 597,560; 149,390 x 5.1 cm = 7.62 km; 597,560 x 50 cm2 = 2,988 m2 x 158.2 W/m2 = 472.7 kW / 44,440 V = 10.64 A (printed 10.657); 104.74 x 10.657 = 1,116 A (printed 1,117.7); 104.74 x 10.657 A x 44.0 kV = 49.11 MW, the printed module power, and 108.45 x 11.923 x 44.0 = 56.90 for 6 mils, so the module power is strings x string current at the 44.0 kV load in every column (the printed 1,117.7 A is 0.13 per cent above 104.74 x 10.657); 49.11 / 56.90 = 0.863, the 13.7 per cent; 20 million kg over 100 km2 = 0.2 kg/m2, which is 4 mils of fused silica at 55.88 g/m2 per mil x 0.966 = 0.216 kg/m2, consistent.
Basis: 1-MeV electron equivalent fluence per cm2 over 30 years in GEO; W/m2 after 30 years; volts per cell; cells per string
Related records
- Answers question
- QST-018 not published in this release
Cite this
energyaperture.com/c/clm-1116
CLM-1116, Energy Aperture, as of 1977-07.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-475
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