Plans for solar power from outer space move forward
bySep 26th 2009 7:00AM
A California technology startup is rapidly pushing forward with plans to build the first space-based solar power station to beam 200 megawatts of electricity back to Earth via microwaves to a receiving station near Fresno. The firm, Solaren Space, has been pushing for space-based power since 2001 and it secured a Power Producing Agreement with PG&E Corp.in April 2009. PG&E (PCG) hasn't put any money into the project but its willingness to sign shows that Solaren must be doing something interesting.
The concept is not novel. Satellites floating outside the atmosphere can capture solar energy round the clock and without power-reducing cloud cover or atmospheric interference. The satellites use photovoltaic panels, much like what goes on rooftops, to capture energy and convert it to microwaves. A large antenna on Earth recaptures the energy of the microwaves and converts them back into electricity. In fact, space-based power appears to be quickly moving towards reality. The Japanese government announced earlier in September a massive project to build a space based power-plant producing two gigawatts of electricity.
I interviewed Solaren's Director of Energy Services Cal Boerman about the project.
Daily Finance: What has changed over to make space-based power technically feasible today? Have there been any breakthroughs that have made this possible?
Boerman: Actually, not really. The technology is fairly well developed. if you look at today's communications satellites, they have solar cells that generate the electricity they need. These satellites convert the electricity into radio waves, then signal to your home to your television. That's what DirecTV does. Except unlike them, we don't throw away the center part of the beam where all the energy is located. They only want to signal around the edges. So there is no novel technology development required. It's an engineering problem. Our challenge is to make the surface areas a little bigger and lighter but not to develop a key technology that makes or breaks the project. What we have done differently is keep the weight of our satellites down. Unlike other projects, we won't have to build them in space. That's a big difference.
How many launches will it take to the get the whole system up and orbiting?
We can do it with a small number of launches, only four. To get that, we had to come up with a design that was lightweight and innovative. We're still using a big rocket. Each launch will have a satellite or a piece of our system that will go up. Once we are up there, we will rely on concentrating the suns energy with mirrors to improve efficiency. We'll have a large footprint but it's not acres of solar cells like NASA has depicted. We have to use space-qualified photovoltaic solar cells that have a proven track record. We'll use mylar or some other lightweight reflective material to construct mirrors to concentrate the sun's energy.
How much will this project cost?
A few billion dollars to get it done. We are looking for private investment. We're not seeking any government funding or utility funding.
It seems a little risky. Aren't investors nervous?
There are some large investor trusts who are willing to try this for humanitarian uses. These institutions are looking to make significant improvements in the world's way of life and so I think they might be willing to take a bit more risk. But yes, everyone is worried about that. We'll buy launch insurance and cover ourselves. But its a new technology and people are apprehensive.
Won't the signals hurt birds or knock down planes?
Not at all. The effects of RF signals on the human beings and birds and airplanes are well understood. We know what the safety standards are. We've been transmitting things this way for a long time. We need to make sure that our signal is controlled. The effect of RF energy on the human body is a heating effect. The energy levels we'll be working with are a lot less than you might feel if you were sitting out in the midday because the beam will be spread out over a very wide areas. The receiving antenna on the ground will be a couple of square miles. It's a big area but that means the beams are at lower concentration. As for airplanes, they would feel more heat coming out from under clouds than they would entering our beam. Remember, the satellites are 22,000 miles up, far above where planes or birds fly. We're so high up that even space junk is not an issue.
The antennae sound huge.
We actually try to keep a fairly controlled beam. But it will go from one kilometer in diameter in space to a circular mile on the ground. So the beam does spread a little bit. These antennaes have been built and tested in the lab and we know they can receive microwaves and convert them back into electricity. Nothing as big as what we need has been tested but scientists know the efficiency and the behavior of these antennae.
Why is this better than terrestrial solar farms?
There are a number of reasons. The first question we are addressing is how much solar energy there is at 22,000 miles off the Earth. If you took a one kilometer strip surrounding the planet, it captures enough solar power to create a generation capacity of one trillion watts. If you filled that area with satellites, you'd generate a really significant portion of the Earth's electricity. What we're offering is clean renewable energy 24 hours day, seven days a week. Most renewables cannot be used for so-called baseload power because their generation capability is variable. Space-based solar power is clean renewable energy that is capable of meeting baseload power needs. For utilities, 80 percent of their electricity needs to be baseload power that is always on. We believe we can address and maybe replace baseload coal plants. Our technology can be looked at as true replacement for that over time.
It would seem like you could move the beam to different locations that needed power, almost like a science fiction movie.
That's correct. If you have a satellite in orbit, we can move the beam from location A to location B if there was another antennae to receive the signal. From the location we plan for our satellites you can "see" one-third of the Earth. So you could move the beam, say, from New York to Chicago to Denver to San Francisco to match peak demand.