Friday, April 17, 2009

Sun Power from Space, an old idea returns

There is a new company called Solaren, that has just signed an agreement with the California-based utility Pacific Gas and Electric in which the utility will buy 200 MW of power that will come from solar panels located in space.

And this is mildly frustrating, because somewhere in the files of my last 40-years, there is a whole set of reports from NASA reporting on, and looking into the economics of doing this very thing. Now that was back about 30-years ago, and at the time I remember writing a fairly long report explaining why it would not work. Part of it was based on the overall economic figures that NASA had used, and part more specifically on the relative cost of the panels to make significant power levels. (At the time they were to be made of gallium arsenide, and the entire arsenic production of the United States was less than 25 tons if my memory serves, and I made some disparaging remarks about those who might like to have an arsenic mine next door).

Well move ahead those 30 years and things have changed a bit. Not only do we now have solar panels in space, delivering power to the space station, but they can be made smaller, lighter and of other materials.

At the time of the NASA work, the intent was to send the energy back to Earth in the form of microwaves, with large areas being cordoned off to receive the energy (since it would likely cook anyone or any animal or bird that entered the receiving zone). That particular form of transmission also raised some ribald remarks, and the odd cartoon as I recall, and the current method proposed is to convert it into radio frequency energy for transmission.

Because the satellites can be mounted out in space beyond the Earth’s shadow they can receive energy from the sun all the time, and thus not be affected by either clouds or the day/night shift, so that they could provide baseload power to the utility (as is the intent). This will require that the panels be some 22,000 miles from the Earth - a range now achievable by rocket.

A second company, called Space Energy, is also advancing the idea. NASA checked out the transmission idea back in 2008, but what is not part of the story is that apparently the test was a failure, not a success
Unfortunately for Space Energy, Inc and the entire concept of space based solar power, the actual test results conducted for a Discovery channel documentary proved a total failure. The former NASA executive and physicist who organized the experiment, John Mankins, admitted in a press conference that the $1 Million budget spent of the experiment resulted in less than 1/1000th of 1% of the power transmitted being received on the other island.

The most successful test of wireless power transmission over any distance at high efficiency was conducted by Bill Brown in 1975. Using a NASA deep space tracking dish they transmitted 30kw over 1.6 km (1 mile) at 82.5% efficiency at the Goldstone Deep Space Communication Complex. A Since Geostationary orbit is 36,000 km (22,500 miles) away from earth the space based power station needs to efficiently transmit power over twenty thousand times further than has ever been achieved to date.

Apparently the idea was one of the early ideas submitted to the “Change.Gov” website, where it can be commented on by the public. However, having just dropped by to find the reference I see that after 699 comments, the site has been closed for further comment.

Given that the plan is now to for the utility to get approval from state regulators it should be interesting to see how this project unfolds over the summer. There is some talk of seeing the first return of power in the 2016 time frame. The ground receiving station being located somewhere in Fresno County.

In the meanwhile I am going to go and start digging through some of those old boxes in the back of the office. There is a video of the possible project here (you might note the size of the field array on Earth to receive the signal.)

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