The final frontier: Solar power from space

Pacific Gas & Electric is going to great lengths--all the way to space--in its quest for renewable energy.

The California utility on Monday said that it will seek approval from regulators to purchase 200 megawatts worth of solar energy delivered from stealth space solar power company Solaren over 15 years.

(Credit: Space Energy)

The idea of space-based solar power (SBSP) is to place a device in space that can convert solar energy into a usable form and have it transmitted wirelessly to Earth. Scientists have thought to capture solar energy from space for decades but has it has never been done commercially.

Solaren proposes placing solar panels on a satellite to generate electricity that is converted to radio frequency energy on-board and sent to a ground station in California. The receiver then converts the radio frequency energy to electricity and it is fed into the power grid.

The goal of the project is to provide electricity to PG&E by 2016, said Solaren CEO Gary Spirnak in a Q and A posted on PG&E's company blog.

"While a system of this scale and exact configuration has not been built, the underlying technology is very mature and is based on communications satellite technology. For over 45 years, satellites have collected solar energy in earth orbit via solar cells, and converted it to radio frequency energy for transmissions to earth receive stations. This is the same energy conversion process Solaren uses for its (space solar power) plant," he said.

PG&E, which has significant investments in different forms of renewable energy, said that there is no risk to the utility since it only pays for power produced.

The advantage of space solar power is that energy can be harnessed at all times, even at night or when it's cloudy. Solaren's contract calls for it to deliver baseload power, the electricity needed to meet customer demand.

In its posting, PG&E executives said that generating space solar power cost effectively is a major challenge, but the people at Solaren have a lot of experience in space and satellites. The field also can also draw on years of research.

Another company called Space Energy has been formed to also tap solar energy from space using a similar technique as Solaren.

[Kesteral]

This sounds like a very inefficient way to transmit power from space. Silicon solar cells have a theoretical efficiency limit of about 28%. Then it will need to be be transformed into radio signals, which will cause some loss, transmitted through earth's atmosphere, which also attenuates the radio signal energy, then converted back into electrical enery, where more loss is seen. So, at the end, only a small fraction ofd the suns energy is being changed into useable energy. Couple this with the cost of putting solarcells into orbit, and the cost of the energy jumps even higher. <br /> <br />If you wnat to get solar energy from space to earth, the cheapest way I can think of doing it is to put mirrors up in geosynchronous orbit that reflect down to a mirrior farm here in the ground. The cost of putting stuff in orbit is the same, but some most reflective materials are much cheaper than fabricated solar cells. Also, the energy goes through fewer energy conversions, leading to less loss that way.

[Joe Real]

It is all about funding.

[cwlqwp]

don't worry so much about the efficiency, solar cells on earth only get an efficiency of 2%. this is more efficient because radio waves aren't dispersed as much in the atmosphere as long as converting to radio waves has an efficiency greater than 15~20% it could actually be profitable.

[Kesteral]

RE cwlqwp: <br /> <br />I'm curious where you got your 2% efficiency number. I have trouble believing that the Earth's atmosphere blocks 90% of the light coming at it. True, converting from electicity to radio is fairly efficient, but this efficiency is inversely proportional to the amount of power you are transmitting. So with a high voltage transmission, you will loose 5% to 10% of your power (depending of your frequency, amount of power, and quality of components) . Remember, you are doing this twice, once to transmit, and once to recieve. <br />Finally, a massive amount of power will be lost through attenuation in the atmosphere. Most people don't realize how much energy it take to transmit a radio signal. True, there are UHF and VHF transmitters out there that can cover thousands of miles on 1 watt, but this is more due to the high quality of the equipment recieving the signal than the amount of power. Most of the power is lost within a few hundered feet of the transmitter. If you don't believe this there is a simple experiment you can do that will prove it. Get a chrystal radio, you can find kits for them online, and go to a local radio tower. Chrystal radios are great because they use the transmitted signal as the power source, much like this power from space idea. Get close to the tower and turn your radio on. You should be getting a pretty strong (loud) signal. Now move back about 300 yards. Your radio will be noticeably quieter. Note that chrystal radios only work within a few miles of a commercial broadcast transmitter... Also note that the smallest commercial broadcast transmitter broadcasts at about 20,000 Volts. <br />A radio laser (Raser?) will be able to get much more energy to one spot than a general broadcast tower, but there is still a massive amount of loss from atmospheric attenuation (Think 60% to 95%).

[CorwinB]

Where are you getting this 28% figure from? It is extremely theoretical considering the fact that there are solar cells that go above 40% efficiency. Don't believe me here is a source.<br /><br />http://www.energy.gov/news/4503.htm<br /><br />Or perhaps you should read cnet more thoroughly?<br /><br />http://news.cnet.com/Solar-cell-breaks-efficiency-record/2100-11395_3-6141527.html<br /><br />This is news that is over 2 years old. Why not try to stay up to date on topics before you decide you are smart enough to comment on them<br /><br />I don't know of a term for a theory that has been shown false before the theory is stated. Perhaps you are a little behind on your knowledge of solar technology. But I guess that happens all the time because some people cannot seem to get their minds to wrap around the fact that technology has changed since the 1950s. Or the fact that technological knowledge CAN change at all

[markdoiron]

Kesteral wrote: "This sounds like a very inefficient way to transmit power from space. "<br /><br />It does, at first blush, doesn't it? Fortunately, the concept was proved in the 1970s at the Jet Propulsion Laboratory's Goldstone facility. ATT, participating engineers spoke of 60-70 percent transmission efficiency. <br /><br />The concept of power from the sun was first conceptualized in a "Science" article in 1968 ("Power from the Sun: It's future"). It's nice that someone is putting up a little money to take some risk. Maybe the naysayers will be proved correct, but it's certainly a worthy effort. --mark d.

[7egend]

Transmitting by Radio is hardly the way they actually plan to do it. The japanese have invested large amounts of money of a Low Orbiting Space Elevator which would not only be used in transporting people from Earth to Spice but also Vice Versa. The idea is to build a ring around the Earth connecting Solar Panels connected to this ring together and build several of these "Elevators" to connect to the ring. These "Elevators" would also serve as conduits to transfer this power.<br /><br />As for your mirror idea, this fails tremendously on a cloudy day, the idea of putting the solar panels in low orbit would get the panels into the open space where the sun is not obstructed by cloud cover. Plus the mirrors would have to constantly adjust themselves and maintenance costs would be extremely high for these satellites. Where as an orbital ring would allow for living quarters in stations along the ring to maintain it.<br /><br />Sure initial costs would be very very high, but over all it would allow us to have a large source of energy for all the continents, as well increase our reach into space by living in Low orbit.

[Joe Real]

Here we are, scrambling with ideas to cool off the planet, some of the ideas involved floating reflectors in space to deflect some of the sun's rays away from earth. This one does exactly the opposite. It beams back energy which will ultimately be converted to heat, trapped within the planet. Yes, the scale of this one is negligible to matter at all. And we hope, that in case we really need to lose heat, they can also use these energy collectors to deflect the extra heat away from the earth to help cool it.

[LuvThatCO2]

The scale for one reflector would be negligable... but for thousands and thousands of them, if this ever became mainstream?

[monterini]

Note to Corwin B: Thanks for the link to the Boeing Spectrolab story. You are right; the story and the feat happened 2 years ago. Why then, at the Spectrolab site do they only refer to their latest achievement of 28.3% ? My guess is that the process is not easy, nor is it cheap to scale up. There is a solar company called OptiSolar that recently closed it's doors because of overstaffing in the shadow of the economic tsunami. They sold watts to PG&#38;E. That's it. Not solar panels, nor anything else. The average efficiency for the amorphous Silicon product was 6 to 7% efficiency. Upper 20's and 30's are very difficult and expensive, and are probably a long way off in the quantities needed to make a big impact.

[josmor]

Why not to send the energy from one the day side of the earth to the other... it might be cheaper.

[blueshore]

Did someone remembers Simcity 2000 (http://en.wikipedia.org/wiki/SimCity_2000)? It has a nice satellite microware power plant. Very clean and cute... except for the ocassional satellite misalignment that usually fried half the city. <br /> <br />And regarding the mirrors, there is a funny story too(http://en.wikipedia.org/wiki/Crimes_of_the_Hot). <br /> <br />But how about a rotaring sterling engine and a quite large nanotube wire? Since the rotation make a nice 200+ degrees change, a sterling engine might be able to move a generator and its output can be send via nanowire to a couple of repeater stations down to Earth.

[cwlqwp]

because the light will be transmitted as radio waves you don't need to worry about laser beams frying everyone in its path(well at least directly from the power transmission).

[jwmpc]

Perhaps laser transmission would be more efficient? Less spread of the signal for one thing. However, it would probably be more efficient to have portable solar farms that could cover a couple acres of desert for a few weeks, then move on. Transmission of the power is still an issue, but distance traveled is far less(assuming the temporary transmission is to a local grid node).

[cwlqwp]

this is sort of like a laser transmission, since radio waves are a type of light. however you probably meant a form with a higher frequency, but lower frequency is better so it is safer and does not get dispersed in the atmosphere.

[hador_nyc]

They'll use a MASER. Microwave "Lasers" actually predate light "lasers" by a few years.

[LuvThatCO2]

If only we had a clean, emission-free way to generate massive amounts of cheap energy. <br /> <br />Oh wait, we do. Its called nuclear power. <br /> <br />We do not have a shortage of electricity - we have a shortage in the political will needed to stand up to the extreme eco-whacko movement that has stifled nuclear power despite it being the cleanest form of energy available.

[Michichael]

I agree completely. Nuclear fusion power is incredibly safe. Fission is dangerous, yes, but fusion power is very safe and effective.

[alfarid23]

Very interesting. So yeah, HI I'm the eco-whacko , and I would like to know when Chernobyl2 will happen again? And also please tell me where it will happen too, just so I know not to live with 2000 miles next to that place.

[Michichael]

Alfarid - considering that fusion power has zero potential for an uncontrolled "meltdown" like fission does? Never.<br /><br />Fusion reaction only goes on as long as there is fuel and a very controlled environment. Any disruption to this environment results in a collapse of the reaction - not an explosion such as what can occur in a fission reaction.

[alfarid23]

@Michi<br /> Thanks, I'm aware that fusion is clean source of energy and nobody is opposed to it. However "nuclear power" term is still reserved for fission, because of its wide adoption around the world. Risks of running fission plants are extremely high, when even minor accidents are devastating to entire areas. So i don't understand how people can still advocate its use. If fission was so nice to use, why don't we have fission powered cars then?<br />Unless, of course, they want their burgers to come from 3-headed cows.

[DavyCrocket2003]

Radiation from nuclear energy is way hyped up. It makes a good scare-tactic. It's nowhere near as dangerous as people think. There are people living in Chernobyl right now and they are perfectly fine. Sure, you have some increased risks for thyroid cancer. But smoking cigarettes is a lot more carcinogenic. Anyway, there are two reason we don't have more nuclear power plants. First is because it costs so much right now. It isn't profitable. Maybe more research and development could make it more profitable. Second, because whenever someone tries to build a nuclear power plant, people like you freak out like we're trying to poison the planet. There's a fight just like that going on right now in my state of Utah. Anyway, it doesn't really matter to me. Solar will soon leave its competitors behind. Power for a dollar per watt production. High tech, long-life, super energy-dense sulfur batteries combined with thin-film solar will pave the way to a new energy age.

[dougjake]

Isn't the title of this article redundant? After all, from where else would we get solar energy?

[Seaspray0]

It would be nicer to get the energy the same way the sun does... fussion nuclear energy. But we don't know how yet.

[Michichael]

Seaspray - yes we do. We've got several working methods - just the bureaucratic red tape and eco-tards like getting in the way of progress.

[ReasonableGuy]

How can the solar satellite energy beam system be efficient without being deadly? Either the beam from the satellites to the earth based antennas is weak, and requires acres of antenna, or it is strong and harms every bird and insect that flies through the beam, and every land creature that the beam accidentally hits. Can a true physics geek enlighten us?<br /><br />Nuclear has a couple of huge problems: 1) - Long term disposal / storage of nuclear waste; 2) - potential for use of radioactive materials as weapons; 3) - Fear of all cancers; <br /><br />Solve those and nuclear has a chance. <br /><br />When you can find solvent private insurers willing to provide liability insurance for a nuclear plant without government subsidy, then you can declare nuclear power (as done in the U.S.) to be safe. <br /><br />Until then the best that can be argued is that it is extremely risky, but necessary.

[Michichael]

1) Nuclear Fusion doesn't produce the radioactive byproducts that fission does - what is produced via nuclear fusion is no more dangerous than some of the dyes we use for radio imaging in hospitals.<br /><br />2) Fusion doesn't produce "weaponized" or "weaponizable" byproducts. <br /><br />3) You're more likely to get cancer from having sex or the background radiation in your home than you are to get from being exposed to radiation of any US nuclear power plant - fission or fusion.<br /><br />The big nuclear scare is from people getting sick of radiation poisoning and being told there was only a minor leak when in actuality there was a major problem. Further, that's a fission problem, not a fusion. Nuclear fusion is the most efficient and safest method of generating heat, light, and as a result, power - we've got several projects currently working on this, such as the ITER facility in Europe, and the laser fusion testing center in California.

[s1der]

the first thing I have to say about storage and desposal of watse is not here on earth but at the sun in which occurs all the time and that would eliminate some of the weapons use. we send people in to outer space all the time and are building a space station --- why not get rid of the waste in space vehicles toward the sun ( a near miss after leaving the earth would let the sun gravitationsl pull suck it in to it thus with the waste problem !

[jbolsen]

We often hear the "let's blast the nuclear waste into space / the sun" argument. <br />But consider this: <br />- The Hanford site currently contains 53 million gallons of high-level radioactive waste (http://en.wikipedia.org/wiki/Hanford_Site) - and that's just some of the total amount of radioactive waste in existance. <br />- Achieving escape velocity for that amount of material would cost astronomical amounts of energy and money. <br />- Would you risk sending 1000's and 1000's of rockets with radioactive waste into space knowing that some percentage (say 5% or so) fails in spectacular ways? <br /> <br />A sidenote on that is that perhaps a space-elevater (http://en.wikipedia.org/wiki/Space_elevator) would be somewhate safer and more economical but that's science fiction for now. <br /> <br />So sorry - but the nuclear waste we're producing now is going to stay with us for the forseeable future.

[paulstewart9]

A critical aspect of this is to make sure we do not bring more energy to the planet than it would otherwise naturally absorb. Otherwise, we end up with the same global warming problem we have with fossil fuels. There is likely a way to manage this and it is likely that the economics of using the sunlight we get here will be far better and the outcome more manageable as far as the environment.

[Jack Gratteau]

This has to rate as one of the nuttiest ideas ever to expend someone else money. First off, the difference in Solar flux for a ground based collector is barely different than a space based one (500W/sq m vs 750W/sq m). A concentrated solar cell is about 40% efficient, only if you can get rid of the heat. That is easy to do on the ground, and the heat can be harvested to run steam power conversion. All of this adds weight, and it costs about $5000/lbs for low earth orbit. Figure this structure will clock in at about 20,000lbs, or about $100million just to launch. Then you have a fleet of them to overfly your receiving point. Think Irridium, they went bankrupt before getting the whole fleet on the air, and just lost one to a collision with a wayward Soviet satellite. Putting the satellite in geosynchronous orbit cost about 4X more. Now think about how long the hardware has to tolerate being operational. It takes station keeping thrust to stay on orbit. Plan on replacing the thing every 10 years. Now you want to irradiate some piece of real estate with 100KW/sq m RF energy. After you've cleared all the air traffic for miles around, any buzzard unlucky enough to follow the stench of death that it will attract will add to the kill radius. Imagine what it will take to service the receiving array. Put on a chain-mail suit like used in high tension wire service. Hike for miles to get to the site. OK build a shielded tunnel to get there. Then use non-conducting tools to work around the hardware. Now factor in some reality of the physics of the whole thing. You don't get a nice little spot on the ground like a flashlight. Diffraction effects will produce an "airy disk" around your target, so you will have to cordon off more than 100X the area of primary footprint for the side lobes. More physics, the Earth doesn't like you mucking around with the planetary geomagnetics. Whatever EMP you plan to put down in the desert somewhere is going to be re-imaged 180 degrees around on the other side of the globe. This is one of the reasons why we stopped doing nuclear tests, it had a nasty habit of knocking out the communications and hardware in places we didn't intend. That was back in the 50's and 60's, before everyone had a PC and an iPod. Add a little havoc like this today, and it'll be be more than a few penguins that get sunburned.

[batvette]

I think you and tsport100 have a better grasp of the limitations of technology than PG &#38; E and the dreamers thinking this is right around the corner from being workable. <br />We have so much rf energy bouncing around us from multiple sources already, with the biological effects largely unknown or if they are they are kept from public knowledge. The jury is still out on microwave energy dangers as well as EMF, (though surely PG &#38; E is one of those who will say all those teachers in Fresno who got rare cancers after teaching in classrooms along a high voltage transmission line were "random" or "allowable risks") I don't think this is an acceptable solution. <br />One thing not discussed, is getting all this up into space is going to require a lot of launches by the biggest vehicles available. The type of propulsion varies, and eaach has its own damage factors to the environment. <br />While we don't expect too many of these: <br />http://www.liveleak.com/view?i=20f489a8e7 <br />we can expect damage to the ozone layer as even the more environmentally friendly non-hypergolic liquid propulsion systems burn their combustible fuels at that altitude, as discussed here: <br />http://www.thespacereview.com/article/1395/1

[tsport100]

Lets jump in here with both feet!<br /><br />The entire system relies on RF power transmission. The ONLY modern day test over any distance (only 148 km - geostationary orbit is 36,000 km) failed to receive any more than 1/1000th of 1% of the power transmitted. Do the math and calulate how much power needs to be transmitted to receive 200MW...<br /><br />The RF power transmission technology does not exist!<br /><br />Show me a test over 36,000 km at 90-90% efficiency and then we'll start saying this is even remotely feasible! Besides that technical hurdle it will ALWAYS be cheaper to install PV cells on the ground!<br /><br />http://www.gizmag.com/solar-power-space-satellite/11064/

[Dango517]

I'm not convinced putting a solar umbrella over the earth is a good idea. Long term and on a grand scale, the repercussions would be negative. <br /> <br />With bases planned for the Moon and Mars NASA maybe pitching in a little support on this one. Both are dusty places with low gravity, add a little human activity and solar's effectiveness may drop dramatically in these two locals. <br /> <br />With any of these approaches the international political considerations need to be weighed heavily. With Star Wars and now Obama's talk about merging NASA with the Defence Department (very bad idea) more then a few of our neighbors might be raising an eye brow or two over these sorts of plans. <br /> <br />I'm continually amazed that the only State seemingly behind solar is California. This should be the domain of the Mid-West with the most to loose during gasoline price spikes. Maybe being the largest "populous" state in the Nation has something to do with it, maybe, or simply this might be a "hook" for R&#38;D dollars. Do they do research in the cold of the Mid-West? Yes, I realize we don't have a beach but the Great Lakes are pretty nice,. besides you can drive a car on them in the Winter, that is if Winter returns.

[mranenome]

I'll believe it when I see it

[Axil128]

The answer to abundant energy is the Thorium fuel cycle and the Liquid Fluoride Thorium Reactor (LFTR). Dr. Edward Teller, the father of Fusion, after a lifetime of work on every aspect of nuclear technology had at the end of his life come to this conclusion in his final study: the LFTR is the best of all possible reactor types. <br /> <br />The LFTR is a very simple, efficient, and elegant type of reactor. It can start up on any kind of nuclear fuel, bomb material, or nuclear waste product to produce very high temperature heat and at the same time breed more fuel in the bargain. This thrifty approach to nuclear energy greatly appeals to me, but I became even more interested in the LFTR when the details of a new patent were revealed by Dr LeBlanc (see below @ minute 53). It opens up the possibility of building a very compact but powerful reactor that can run for 30 years without refueling. It can be operated remotely in an unattended fully automated intrusion detecting mode and sited underground while it breeds self perpetuating new fuel within the thorium structure of the reactor itself. <br /> <br />In order to get to its fuel, U233 that has been produced inside the very solid metal walls of this 200 ton reactor containment vessel, a proliferator must destroy and disassemble the reactor, lift its heavy reactor core out of a 100 meter deep reinforced aircraft crash proof hole in the ground, then cut the thorium containment vessel up into small pieces while enduring heavy killing gamma radiation exposure, next reprocess these reactor pieces using isotopic separation since the U233 is denatured with enough U238 to make chemical separation of bomb grade U233 impossible, and do all this without being detected. Now, this is a tall order for any proliferator and may just be an impossible assignment. <br /> <br />At the end of the service life of the Lftr, the reactor vessel is sent back to the factory where it is reduced to liquid fluoride salts that become the feedstock of a next new Lftr. This feedstock can only be used by the new Lftr and not for bombs. A few handfuls of waste products are held at the factory for a few hundred years to cool down before they are mined for the many precious elements contained within like platinum and iridium. Now that is what I call a safe, efficient and thrifty mode of operation! <br /> <br />To learn more see one of the following: <br />Aim High <br />http://rethinkingnuclearpower.googlepages.com/aimhigh <br /> <br />What Fusion Wanted To Be <br />http://www.youtube.com/watch?v=AHs2Ugxo7-8 <br /> <br />Liquid Fluoride Reactors: A New Beginning for an Old Idea <br />http://www.youtube.com/watch?v=8F0tUDJ35So <br /> <br />The Center for International and Security Studies at Maryland has some good things to say about thorium as follows: <br />http://www.cissm.umd.edu/papers/files/future_nuclear_power.pdf