| Ground vs. Space Solar Energy by Dave Dietzler 2009 The USA in 2005 used about 100 quadrillion BTUs (105 exajoules, or 29000 TWh) in 2005. In simpler terms, 29,000/8760h = 3.3 TW years. This is for all forms of energy use-transportation, residential, commercial and industrial, from all sources-oil, coal, gas, nuclear, hydro, and renewables like wind, biomass and solar. If we envision an all electric zero carbon emission economy of the future, say in 2050 CE, with electric cars, furnaces, stoves, etc. powered by ground based solar using only as much energy as we did in 2005 by the use of radical conservation measures and population growth stabilization, we would need to cover 33,000 square kilometers or 8,250,000 acres of land with solar panels generating 100 w/square meter. However, this does not account for cloudy days, night and reduced output in the morning and evening. A good guess is that we would need three times as much solar panel area or 99,000 sq. km. and extensive energy storage systems for times when the sun doesn't shine. Let's round that up to 100,000 sq. km. or 25,000,000 acres. At $10,000 an acre the cost would be 250 billion dollars for the land alone! Add the cost of the actual solar panels, supports, cables, switches, invertors and manpower to clear land of trees (imagine the impact on our forests), grade the land flat, dig post holes, and set up all the panels and the cost increases to an extent that I can only guess at. Let's say 500 billion to a trillion dollars. To make matters worse, energy storage systems would be needed like pumped hydro reservoirs, batteries in cellars, hydrogen tanks and hydrogen fired turbogenerators, and perhaps compressed air storage. A whole new power grid would also be needed to handle all the power demand from recharging vehicles, furnaces, stoves, etc. This revolution to an all electric zero carbon emission economy would have to come about gradually as we upgraded the power grid, retooled factories to make electric cars, people switched from gas to new electric furnaces and stoves, and commerical and industrial users switched from gas to electric furnaces and stoves. While today we are generating more power with renewables, learning to conserve and paying to conserve by installing more insulation and designing better buidlings, driving more hybrid cars and using cleaner burning natural gas, the time will come when we go to an all electric economy with no carbon combustion except for biomass. Winds, biomass, geothermal, waves, tides, roof top solar and hydro will all be sources of energy. Nuclear fission is undesirable for many reasons. Nuclear fusion using deuterium and tritium might appear in the next few decades but nobody knows for sure and nobody knows if fusion will be an economical source of power. The DT fusion reaction releases floods of high energy neutrons that cause the formation of some radioative waste, though not nearly as much as fission, and these neutrons will also damage the reactor thereby limiting its lifetime. Fusion reactors will be very expensive and if their lifetimes are shortened greatly by neutron bombardment compared to fission reactors or conventional power plants then they will never meet the demands of the market and fail. Solar energy looks like the best bet, but do we want ground based solar or space based solar? We wouldn't have to cover 25 million acres of land and the space solar power plants would last for a long time compared to ground based solar plants as there is no extreme weather- snowfalls, thunderstorms and lightning strikes, tornadoes, hurricanes, and hail storms in outer space. There is no rust, corrosion, or erosion of land (forget about solar panels on hillsides) in space. There are no earthquakes, local wars, endangered species, indigent populations that have to be relocated, terrorists, tropical diseases that could effect workers or unstable governments in outer space nor are there likely to be socialist revolutions and nationalization of space solar power plants after private entities have invested billions of dollars. Space solar power satellites would outlast ground based solar power plants and return more on investment, even if the initial outlay for space solar was higher than ground solar perhaps. Finally, the Sun shines 24/7 in GEO and space solar can supply constant power to meet demand that exists 24/7 without expensive power storage systems. A new grid would still be required. Many homes might need rewiring as well as new electric furnaces and stoves but at least people wouldn't have to install battery banks in their cellars. The change must occur gradually as all electric new homes capable of handling recharging two cars are built and old homes are improved. Expensive fuel prices will motivate such change. The question becomes not "Why" but "How?" Clever scientists and engineers will figure out the technology, but the question "How?" becomes "How will we ever afford it given the high price of space travel?" It costs about $10,000 to put a kilogram in LEO for the Space Shuttle. The Russian Proton rocket can do it for about $4300 and the Space X Falcon 9 is projected to do that for $3300.* To reach the Moon based on the costs of Apollo and the Saturn V we are looking at about $30,000 a pound to the Moon! We should not use Apollo and the Saturn V as our benchmark. A Falcon 9 could orbit a payload and for little extra cost use ion drives or solar sails to head for the Moon. However, the payload will be at least half rocket fuel for the retros that soft land the payload on the Moon. The lander would be cannibalized for economy. Let's just make a wild guess that cargo could be landed on the Moon for $10,000 a pound. That's probably too high but it will do for the sake of argument. At this price it would cost $20 billion to land a thousand english tons of telerobotic industrial seed machinery on the Moon. That's a far cry from $250 million for land alone! A thousand tons is one heck of a lot of cargo and if it is carefully selected it could use lunar materials to replicate itself and build Moon mining, regolith refining and lunar manufacturing devices. The main cost after landing the seed on the Moon would be payroll for Earthside teleoperators and workers at the radio stations that communicate with the robots on the Moon, in addition to taxes. Perhaps the government will give tax breaks to space businesses to foster their growth and a new era of solar energy. The seed would grow until industry existed on the Moon that could produce millions of tons of materials every year and launch them with mass drivers made on the Moon into space for solar power satellite construction. Habitat for humans would also be built. Rocket fuel would be produced on the Moon for Moon Shuttles that landed manned spacecraft and unmanned cargo carrying craft arriving in lunar orbit. Fuel would also be produced for rockets that convey humans back to Earth. This would reduce costs. Regolith could be mined freely without paying for land use rights or property taxes. Materials and manufactured items made on the Moon would be launched into space, probably to L5, and combined with cargoes from Earth to build solar power satellite construction space stations with large crews of teleoperated robots and smaller crews of human supervisors. The only thing that's really absent in this scenario from O'Neill's original vision is the Bernal Sphere space colony. Most of us would agree that teleoperated AI robots should do most of the work. The resources of the Moon are basically free. Most costs beyond rocket freight costs will be payroll for groundside and space side workers. There will also be costs for building rectennas on Earth that could be built over corn fields. There will be the cost of the seed itself but once the seed is producing metals and solar panels on the Moon the only real cost will be payroll for teleoperators and crews on the Moon. Transporting humans to the Moon, L5 and GEO will be expensive. The pricetag for developing the technology such as the Ares rockets and CEV to return humans to the Moon circa 2020 CE and carry out missions on the Moon for a number of years is estimated to be $100 billion. Perhaps space entrepeneurs will copy this rocket technology and produce it on the cheap. Once fuel is produced on the Moon the fraction of manned payload sent to the Moon that consists of fuel for landing on the Moon and returning to Earth will be slashed and the number of humans sent to the Moon can be increased for the same price. We will need a larger space capsule and a reusable lander or Moon Shuttle. An international effort should be made to develop all this technology rather than have nations competing to see who will be the next to land on the Moon by imitating the Apollo program. The long range view of space solar energy for the whole world must be taken or we will have nothing but flags and footprints on the Moon for an enormous cost to the citizens of the world. *see: http://en.wikipedia.org/wiki/Comparison_of_heavy_lift_launch_systems |
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