Saturday, October 04, 2008
3. The sum of $12 billion to be paid for construction and maintenance of a Lunar base in which no fewer than 31 Americans have continuously resided for a period of not less than four years and one day.
4. The sum of $10 billion to be paid for construction and maintenance of a solar power satellite system which delivers at least 800 megaWatts of electric power to a receiving station or stations in the United States for a period of at least two years and one day.
Politicians tell us that the era of cheap & readily available energy is over. There is, if not unlimited power available, enough going to waste passing through the area between Earth & Moon, to turn this planet into incandescent gas. Not suggesting that as a policy but lets not have any rubbish about having to make do with less. Once we start building such satellites we can keep turning them out forever at a much lower marginal cost. Since there is no wind or rain in space they can be designed to work almost forever. We have to assume a relatively cheap cost to orbit but even so to make them in quantity will almost certainly be cheaper using lunar materials for mirrors & all large parts which is why I have included mention of the lunar base X-Prize as well.
The solar energy collected by an SPS would be converted into electricity, then into microwaves. The microwaves would be beamed to the Earth's surface, where they would be received and converted back into electricity by a large array of devices known as a rectifying antenna, or rectenna. (Rectification is the process by which alternating electrical current, such as that induced by a microwave beam, is converted to direct current. This direct current can then be converted to the "slower" 50 or 60 cycle alternating current that is used by homes, offices, and factories.),....
It is interesting to compare the availability of sunlight in space with that on Earth. A solar panel facing the sun in near-Earth space receives about 1400 watts of sunlight per square meter (130 watts per square foot). (Of course, only a fraction of this is usable due to conversion inefficiencies.) On Earth, the day-night cycle cuts this in half. The oblique angle of the sun's rays with respect to the ground (except at noon in the tropics) cuts this in half again for a typical spot on the Earth. (Solar panels on the ground can be angled upward to circumvent this, but they must then be spread out over more ground to avoid casting shadows on each other.) Clouds and atmospheric dust cut the available sunlight in half again. Thus, sunlight is about eight times more abundant in geostationary orbit than it is on the Earth....
a design for an SPS which consisted of a 5 x 10 kilometer (3 x 6 mile) rectangular solar collector and a 1-kilometer-diameter (0.6 mile) circular transmitting antenna array. The SPS would weigh 30,000 to 50,000 metric tons. The power would be beamed to the Earth in the form of microwaves at a frequency of 2.45 GHz (2450 MHz), which can pass unimpeded through clouds and rain. This frequency has been set aside for industrial, scientific, and medical use, and is the same frequency used in microwave ovens. Equipment to generate the microwaves is therefore inexpensive and readily available, though higher frequencies have been proposed as well. The rectenna array would be an ellipse 10 x 13 kilometers (6 x 8 miles) in size. It could be designed to let light through, so that crops, or even solar panels, could be placed underneath it. The amount of power available to consumers from one such SPS is 5 billion watts. (A typical conventional power plant supplies 500 million to 1 billion watts.)
The Japanese recently put up a small experimental power satellite.