Difference between revisions of "Solar Power"
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The first small scale bases on the Moon with either use solar power or nuclear power (or both). | The first small scale bases on the Moon with either use solar power or nuclear power (or both). | ||
| − | Solar power can be thermal (e.g. [[Brayton Cycle]] or [[Stirling Cycle]]), or [[Photovoltaic]]. | + | Solar power can be thermal (e.g. [[Brayton Cycle]] or [[Stirling Cycle]]), or [[Photovoltaic]] (PV). |
| − | + | The problem with solar power is that PV conversion efficiency is only about 20% efficient, for rather high priced PV cells. Plus PV cells are rather heavy to ship from Earth and soft land on luna, rather expensive to do. | |
| − | + | Until [[ISRU]] manufacturing is online, [[Solar Power Satellites]] (SPS) represent a more economic means of supplying large scale basebar power on the Moon in the early days. | |
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| + | A SPS rectenna, on the other hand, is lightweight and has a conversion efficiency of over 90%. | ||
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| + | Let us assume a PV array is 10 times heavier per watt than a rectenna. | ||
| − | + | That means we can get 5*10 = 50 times as much power per kilogram for a rectenna than for a PV array. That means a rectenna will be be at least 50 times cheaper per watt of useful power than PV array. "At least" because the manufacturing cost of a rectenna will be much cheaper than for PV array. | |
| − | + | Soft landing hardware on to the Moon is very expensive, so weight is at a premium. | |
The distance from L1 to Luna is about the same as the distance from Earth to a geostationary satellite. | The distance from L1 to Luna is about the same as the distance from Earth to a geostationary satellite. | ||
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All these factors permit the smallest rectenna at that location. | All these factors permit the smallest rectenna at that location. | ||
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Without making any modifications at all to that very SPS, it could easily be maneuvered from L1 to GEO to feed a terrestrial ground based rectenna. The antenna design for L-1 to Luna will work equally well from GEO to Earth | Without making any modifications at all to that very SPS, it could easily be maneuvered from L1 to GEO to feed a terrestrial ground based rectenna. The antenna design for L-1 to Luna will work equally well from GEO to Earth | ||
Revision as of 06:26, 27 January 2007
The first small scale bases on the Moon with either use solar power or nuclear power (or both).
Solar power can be thermal (e.g. Brayton Cycle or Stirling Cycle), or Photovoltaic (PV).
The problem with solar power is that PV conversion efficiency is only about 20% efficient, for rather high priced PV cells. Plus PV cells are rather heavy to ship from Earth and soft land on luna, rather expensive to do.
Until ISRU manufacturing is online, Solar Power Satellites (SPS) represent a more economic means of supplying large scale basebar power on the Moon in the early days.
A SPS rectenna, on the other hand, is lightweight and has a conversion efficiency of over 90%.
Let us assume a PV array is 10 times heavier per watt than a rectenna.
That means we can get 5*10 = 50 times as much power per kilogram for a rectenna than for a PV array. That means a rectenna will be be at least 50 times cheaper per watt of useful power than PV array. "At least" because the manufacturing cost of a rectenna will be much cheaper than for PV array.
Soft landing hardware on to the Moon is very expensive, so weight is at a premium.
The distance from L1 to Luna is about the same as the distance from Earth to a geostationary satellite.
So one could put an SPS at lunar-L1 and beam microwaves from there to supply one or more rectennas on the Moon as a very efficient way to provide energy to a power hungry moon base.
The ideal site for the lunar rectenna would be in Sinus Medii at the Lunar 0-Longitude point on the Lunar Equator, in the middle of the side which faces the Earth.
1) Because it is directly below the L-1 point, 2) it is the closest point on the lunar surface to the L-1 point, 3) Because at that point the lunar surface is at right angles to the incoming microwave beam.
All these factors permit the smallest rectenna at that location.
Without making any modifications at all to that very SPS, it could easily be maneuvered from L1 to GEO to feed a terrestrial ground based rectenna. The antenna design for L-1 to Luna will work equally well from GEO to Earth
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