A ground-breaking new paper on space solar power has just been added to the online NSS Space Solar Power Library. The paper is: “Financial and Organizational Analysis for a Space Solar Power System: A Business Plan to Make Space Solar Power a Reality,” May 18, 2009, 179 pages, 10.7 MB PDF.
Lt. Col. Peter Garretson, NSS Director and one of the principal authors of the Department of Defense report Space-Based Solar Power As an Opportunity for Strategic Security writes:
“This is the first modern paper to include a stakeholder analysis, an in-depth discussion of international organizational aspects (including intellectual property and separation of manufacture and operator companies), and Net Present Value calculations of niche systems (such as front-line military power).”
Authors of the paper are Sun Xin, IT Director of the China Academy of Space and Technology; Evelyn Panier, Finance Application Consultant; Cornelius Zund, Control Systems Engineer at Pratt & Whitney Canada; and Raul Gutierrez Gomez, Lieutenant Colonel in the Colombian Air Force and Planning Director of Military Aeronautical Institute.
The paper was a multicultural team project submitted in partial fulfillment for the degree of Master of Business Administration in Aerospace Management at Toulouse Business School, Toulouse, France.
This paper shows a dramatic reduction in size (and hence cost) can be achieved using 38GHz for downlink, instead of the old 2.5 GHz from the old reference studies.
Key quotes:
“There is a minimum of atmospheric signal attenuation in the range of
2.45-5.8GHz, and also 35-38GHz. Specifically we might expect losses of
2-6%, and 8-11% respectively. We will use a transmission frequency of
38GHz since this allows us to transmit the most energy into the
smallest space, even when accounting for transmission losses.”
“7) We will use a transmitter diameter of 141m.
8) The combination of transmitter size and frequency result in a
relatively small rectenna diameter when compared against the ESA
reference system”
“Linked to the cost of the launcher is the needed mass of the system.
The satellite mass value of 3137Kg/Tm used in our calculations added a
considerable amount of mass for larger transmitter diameters, leading
us to select a higher frequency of transmission (38GHz).
This choice allowed us to afford a smaller antenna / rectenna
combination, however substantially increased energy transmission
density. The diffuse energy density offered with a 2.45GHz system
required a massive increase in rectenna size, and offered no benefits
in terms of cost.”
This should mean that a demo SSPS, as is proposed, in the not too distant future could actually give a useful yield of solar photovoltaic energy, and make the case more convincingly for fullscale development.
what a lot of hog wash. Can anyone actually believe the costs can be recovered by sending 3 tonne payloads into space.
Madness
Yes, solar cells in space can produce 7 times more energy as those on the ground and deliver energy to when ever it is needed.
Also the trap we are in with launch costs is they are high because launch rates are low so launch facilitites can’t use mass production techniques. If space solar power becomes a reality launch costs will drop because the number of launches will go up dramtically.
Hi Karen,
You’ve made some good points on cost reductions in relation to increased launches.
Concerning the other topic, In my reading so far I have not founnd the factor of seven that you mentioned in terms of space based solar output over ground based ouput. The best I have read about so far was a factor of two but that was only refering to the amount of energy striking the panels. If you could tell me where I could read up on the remaining increase in effeciency then I would like to do so.
Jim
Hi Karen,
I’ve answered my own question concerning the factor of seven you mentioned. It seems as though this would refer to the lower terrestrial figure during winter rather than the best case scenario of summer mid day.
The factor of 7 is derived from 4 factors I believe.
1. a factor of 2 from the diurnal cycle(Day and Night). In GEO solar cells are nearly always in sunlight.
2. Sun angle. On earth Solar cells are fixed and sun angle is not always optimum. In space solar cells will always be at the optimum angle.
3. Weather
4. Atmosphere
Insolation is 1435W/M^2 in orbit, and as little as 1100 on the ground in an equatorial desert. It’s less elsewhere. The capacity factor from weather, night, sun angle, etc. is about 20%. In geosynchronous orbit the capacity factor is better than 99%. Eclipses are still a problem in low earth orbit.
In the early stages of our research we clearly understood that we didn’t have neither the time nor the technical knowledge to perform an in-depth study from that perspective. Besides, it was evident that a lot of research have been done with better means than those available to us. Instead we questioned ourselves, “aside from the evident reasons (expensive R&D and launch, as well as lack of appropiate infrastructure for setting up in space such a system) why SSPS hasn’t become a reality?.” So we studied and proposed some financial and organizational strategies that could help solving part of the actual and foreseable problems of bringing SSPS to life. We are proud that our work has found some acceptance. At the same time we ask for feedback both in the technical ground as well as from the “business” point of view. This way we can better reach our goal of contributing to solve the stated question.
Yes, you would still get some dark time with “low earth orbit” but very little with “geosynchronous orbit”. Remember that the Earth is about 24,000 miles circumference, which is very close to the GEO orbit distance – so if you take a globe and wrap a piece of string around the equator, and then stretch that piece of string out FROM the equator, it’s easy to see that the axis tilt of the earth will keep the end of the string in daylight 24 hours a day (except for just a few hours during the equinox, which happens twice a year).
You can achieve 100% power in LEO, so the idea that only GEO will work is not correct. To get 100% power in LEO you put the SBSP satellite in a Sun-synchronous, Dusk to Dawn orbit. Here the satelite will ride the devide between day and night and the solar panels will always face the sun. The canadian satellites Radarsat 1 and 2 use this orbit. To further solve the problem requires that you place reflector satellites in an equatorial 2,000km orbit. So the power produced by the SBSP satellite is not sent directly to the ground, instead it is beamed to the reflector satellite and then to the ground. Doing this allows you to get the same benefits as GEO without the in-space transporatation cost or massive space infrastructure.