Value chain · CLM-1234
In plain terms
A second NASA-funded study in 1980 imagined the standard power satellite with its microwave transmitters swapped for about twenty very large infrared lasers. On paper, about one-seventh of the electricity made on the satellite would reach the grid, a bit more on mountain sites. The receivers would again turn the beam into heat.
The claim as recorded
Rockwell's 1980 study for NASA Marshall defines a GEO laser SPS that replaces the microwave transmitters with 20 or 24 supersonic closed-cycle CO electric-discharge lasers of about 100 MW each (109.8 MW each for 20). They are fed by the 9.4 GW photovoltaic array and beamed 42,700 km at a 50 degree zenith angle to heat-engine receptors of about 30 m aperture. System efficiency (grid over array output) is estimated at 14 per cent for CO and 10 per cent for CO2 to 0.5 km sites, and about 16 per cent to mountain-top sites. The chain takes the laser at 0.2337 overall (discharge 0.50), transmitting optics at 0.992, atmospheric transmission at 0.84 to 0.97 and the receptor at 0.40 to 0.73. Its CO laser lines run from 1852.7 to 2025.1 cm-1 (about 4.94 to 5.40 um). The two receptor concepts "project laser energy conversion efficiencies of 40 to 73%".
Evidence behind this: A NASA Marshall contractor study (Rockwell) defining a laser SPS concept from calculated subsystem efficiencies; nothing measured.
Scope and limits
ESTIMATED EFFICIENCIES FOR A LASER THAT DID NOT EXIST AT THIS SCALE: "SIGNIFICANT TECHNOLOGY IMPROVEMENT IS NECESSARY" (p.74). The efficiency is measured from the array output, not from sunlight, so it is not comparable with CLM-1232's sun-to-busbar figure. The receptor's 40-73 per cent range includes the Lockheed energy-exchanger figure, cited from SRC-547. No receiver irradiance at the ground is stated beyond about 35 kW/m2 on the absorber's inner wall.
What it assumes
That "about 5 um" is a fair label for the CO lines. The page gives wavenumbers, and p.40 [2-31] speaks of "5-um or 9-um laser radiation".
Where it comes from
PDF p.8 [1-1], raw: "capable of consuming, as input power, the entire power output of the baseline photoelectric power source (9.4 GW). Slant ranges to typical receptor sites in the U.S. from a laser in GEO at an altitude of 35,786 km will be taken to be 42,700 km. The zenith angle of the laser beam pointing at earth, 8, is taken to be 50[deg]." PDF p.41 [2-32], raw: "Initial system designs utilize a LOtal of 20 or 24 laser transmitters, each radiating power levels of about 100 MW."; "Using a receptor aperture of approximately 30 m in diameter". PDF p.42 [2-33] Figure 2.5-1 labels, raw: "Transmitting Optics .992", "Atmospheric Transmission .84-.97", "Receptor .40-.73"; text, raw: "nd 0.50", "TlL 0.2337". PDF p.43 [2-34] Table 2.5-1, raw: "Laser Output Power, PL 109.8 MW"; text, raw: "then values of 14% and 10% are estimated for the CO and C02 EDL's, respectively, for propagation to 0.5-km-elevation receptor sites. For mountain-top receptor sites, the laser-SPS system efficiency improves to about 16% for the CO EDL". PDF p.36 [2-27] Table 2.3-5, raw: "Spectrum 12 2025.0794- ... 1852.7092". PDF p.74 [5-1], raw: "Two viable receptor concepts were identified which project laser energy conversion efficiencies of 40 to 73%,". Arithmetic: 10^4 / 2025.0794 = 4.938 um; 10^4 / 1852.7092 = 5.398 um; 20 x 109.8 = 2,196 MW of laser output; 2,196 / 9,400 = 23.4 per cent (matches 0.2337); 9.4 GW x 0.14 = 1.32 GW at the grid (drafter's arithmetic).
Basis: per cent system efficiency (grid power over photovoltaic array output); MW per laser; range in km; wavenumber in cm-1 (wavelength derived)
Related records
- Answers question
- QST-036 not published in this release
Cite this
energyaperture.com/c/clm-1234
CLM-1234, Energy Aperture, as of 1980-11.
Connected records
Other published records linked to this one. A list, not a judgement.