Difference between revisions of "Stratospheric solar array"
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===Parabolic solar receivers=== | ===Parabolic solar receivers=== | ||
| − | Photovoltaic cells are still very expensive, especially ones with high efficiencies (>20%). | + | Photovoltaic cells are still very expensive, especially ones with high efficiencies (>20%). Paintable high-efficiency photovoltaic surface may become possible, in which case this could cover the surface of the blimps (both top surface for direct sunlight and underneath for reflected sunlight). However it may be better to use parabolic reflectors aiming the light onto a thermal converter such as a {{wp|Stirling_engine|stirling engine}}. These have been developed at [http://www.sandia.gov/Renewable_Energy/solarthermal/nsttf.html Sandia National Laboratories] in the US, the [http://ec.europa.eu/research/energy/pdf/stpp_solair_en.pdf EU's SolAir project] and by companies such as [http://www.stirlingenergy.com/whatisastirlingengine.htm Stirling Energy Systems] and [http://news.com.com/Dishing+out+power+with+a+solar+engine/2100-1008_3-6129168.html?tag=nefd.lede Infinia]. |
Stirling Energy Systems say that using their system "a solar farm 100 miles by 100 miles could satisfy 100% of the America’s annual electrical needs". | Stirling Energy Systems say that using their system "a solar farm 100 miles by 100 miles could satisfy 100% of the America’s annual electrical needs". | ||
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# Blimps carry just the parabolic reflectors underneath (or on top or held between other blimps) which point focused sunlight at a separate thermal receiver perhaps held by a much larger aerostat which gathers energy from many reflectors. Blimps would be in herds comprising of many reflector carriers and motherships. {{br2}} | # Blimps carry just the parabolic reflectors underneath (or on top or held between other blimps) which point focused sunlight at a separate thermal receiver perhaps held by a much larger aerostat which gathers energy from many reflectors. Blimps would be in herds comprising of many reflector carriers and motherships. {{br2}} | ||
# The envelopes of the blimps themselves could be the inflatable spheroid dishes mentioned towards the end of option 1 above. Weights with adjustable positioning are hung underneath to adjust the angle of the reflective surface inside the envelope so as to point in the right direction. Blimps could simply be reflectors pointing at a receiving blimp or each blimp has stirling engine at their focal point. If there are significant aerodynamic issues of having a flattened spheroid angled at the sun, the blimp could instead be spherical and clear with a parabolic reflector (or flat fresnel reflector) held inside. Spherical airships are being developed by [http://www.21stcenturyairships.com 21st Century Airships]. | # The envelopes of the blimps themselves could be the inflatable spheroid dishes mentioned towards the end of option 1 above. Weights with adjustable positioning are hung underneath to adjust the angle of the reflective surface inside the envelope so as to point in the right direction. Blimps could simply be reflectors pointing at a receiving blimp or each blimp has stirling engine at their focal point. If there are significant aerodynamic issues of having a flattened spheroid angled at the sun, the blimp could instead be spherical and clear with a parabolic reflector (or flat fresnel reflector) held inside. Spherical airships are being developed by [http://www.21stcenturyairships.com 21st Century Airships]. | ||
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| + | ''(After writing this I discovered Cool Earth Solar are creating earth-bound [http://www.coolearthsolar.com/technology inflatable concentrators] very much along the lines of that described above).'' | ||
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===Station keeping ideas=== | ===Station keeping ideas=== | ||
| − | #Could be tethered to ground with ultrafine, ultra strong fibre. Could get in the way of trans-ocean traffic and might be vulnerable to storms, although if was in remote part of ocean and well publicised this may be less of an issue. Cables could be reeled in with warning and there are parts of the world where storms are infrequent. The advantage over a tetherless array is there are no energy losses due to station keeping and energy conversion processes at the transmitter and receiver ends. Tethered aerostat would tend to rotate around anchor point and lose altitude with | + | #Could be tethered to ground with ultrafine, ultra strong fibre. Could get in the way of trans-ocean traffic and might be vulnerable to storms, although if was in remote part of ocean and well publicised this may be less of an issue. Cables could be reeled in with warning and there are parts of the world where storms are infrequent. The advantage over a tetherless array is there are no energy losses due to station keeping and energy conversion processes at the transmitter and receiver ends. Tethered aerostat would tend to rotate around anchor point and lose altitude with increasing wind speed, but if buoyancy envelope was a {{wp|Lifting_body|lifting body}} then could use angle of attack to create lift to combat this, much like a kite. High altitude tethers also feature in the {{wp|Airborne_wind_turbine|jet-stream sky windmill}} concept. {{br2}} |
#Divert some of the received energy to power ducted propellers or other kind of thruster and virtually anchor using GPS positioning {{br2}} | #Divert some of the received energy to power ducted propellers or other kind of thruster and virtually anchor using GPS positioning {{br2}} | ||
#Stay in same general region by varying altitude via buoyancy control to take advantage of different wind directions at different altitudes similar to the way hot air balloons can have a small amount of control over their direction of travel. {{br2}} | #Stay in same general region by varying altitude via buoyancy control to take advantage of different wind directions at different altitudes similar to the way hot air balloons can have a small amount of control over their direction of travel. {{br2}} | ||
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*Depends on configuration of collectors. Cables connecting each blimp receiving direct solar energy, then mothership blimps carrying high voltage cable down to floating ground station. | *Depends on configuration of collectors. Cables connecting each blimp receiving direct solar energy, then mothership blimps carrying high voltage cable down to floating ground station. | ||
| − | *Or use principle from | + | *Or use principle from {{wp|Solar_power_satellite|solar power satellite}} and generate relatively low energy density microwave beam directed at a {{wp|Rectenna|rectenna}} floating on the sea surface. |
====From sea to land==== | ====From sea to land==== | ||
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*Array could perhaps be sea-based although vulnerable to storms, although could sink below surface based on windspeed and amplitude of waves. Moving sea surface perhaps more difficult for aiming reflectors. Potential cloud cover and full atmospheric attenuation of sunlight reduces efficiency. | *Array could perhaps be sea-based although vulnerable to storms, although could sink below surface based on windspeed and amplitude of waves. Moving sea surface perhaps more difficult for aiming reflectors. Potential cloud cover and full atmospheric attenuation of sunlight reduces efficiency. | ||
| − | *Perhaps Buckminster Fuller's [http:// | + | *Perhaps Buckminster Fuller's [http://www.cjfearnley.com/fuller-faq-5.html#ss5.2 Cloud Nine] concept could be used as the aerial floating platform, and no hydrogen would be required. |
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Latest revision as of 00:02, 19 July 2010
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