Beaming solar power in from space

Funding for winning bids to develop solar power stations in space was announced this week by the UK government. In a speech at London Tech Week, Energy Security Secretary Grant Schapps confirmed that 8 UK universities, including Cambridge, Imperial, Queen Mary and Bristol, as well as several technology companies will share grants worth £4.3 million to kickstart the initiative, saying, "I want the UK to boldly go where no country has gone before - boosting our energy security by getting our power directly from space." The vision is of a massive orbiting solar array that harvests sunlight unweakened by the effects of the atmosphere and where physical space is less of a constraint. The energy is beamed down to Earth and fed into the grid. By 2050, systems like this, they say, could be yielding up to 10 GW: that's the equivalent of 16 Hinckley Point C nuclear power stations. The UCL Energy Institute’s Mark Barrett had this to say…

Mark - Rather than having your solar panels on your roof, they plan to put them in space attached to a satellite. The advantage there is that there's no day or night, so they can generate all the time. And then the electricity is converted into something called microwaves, like you have in your microwave cooker. And that energy is beamed to earth where it's picked up by a pretty large area of special antennae. You know, you're talking many square miles, which convert the microwaves back into electricity and put it into the grid.

Chris - Let's take this step-by-step then. First of all, let's consider the scale of this. How big is this?

Mark - The proposed size is two gigawatts and the satellite and the PV panels might weigh about 2000 tonnes. And to contrast that, the largest thing in space is the space station, which weighs 400 tonnes. So this satellite is far, far larger.

Chris - How practical is this to do this? Someone obviously thinks it's worth investing at least some money to do pilot work on this because they've put up a reasonable sum of seed corn funding, haven't they?

Mark - The truth is for all of the components of the system putting solar panels in space at this scale, all of these things are just simply unproven. But in addition, we have the huge cost of getting these equipment, these thousands of tonnes into space. And this is something that won't be assembled by humans. We will have lots of robots. This is proposed, lots of robots out in space, putting all this stuff together. And also, I might add, whereas the solar panel on your roof can be easily maintained. What happens if something goes wrong in space, thousands of kilometres away? What's the practicality of getting robots up there to make it work again?

Chris - Something's only worth doing in sustainability terms if it's better than what we could do already. Now, is there a danger given what you've just said, that we do all this and the carbon footprint is so far in the red that this thing never pays for itself?

Mark - Well, we have to rapidly reduce our greenhouse gas emissions to stop excessive climate change. And we need a reliable supply of electricity. We currently do this with solar panels and wind generators. The costs have fallen by 80% in 10 years, and just in the last year, the global increase in the capacity of solar and wind on the planet earth is equivalent to 50 of these satellites. So by the time they get the first one working, which they think might be around 2040, we could build at least 500 equivalent solar satellites, but on Earth.

Chris - Indeed because if one just considers the Sahara Desert, and if you took just a small fraction of what is currently unproductive surface of earth, getting very hot every day with more sunshine than anywhere else on earth, surely it's easier to transport electricity from the Sahara than it is from space.

Mark - Yes, the point is well made. Using solar and wind with long distance transmission, we can spread the demands and the supplies of renewables out of very large areas. These are all proven technologies, or most of them are 50 or a hundred years old. They're built in their thousands. And so, we know about their reliability. And they're built by, in the main, by private companies competing in markets so that the costs aren't excessive. Whereas these solar satellites, they're going to have to be, one estimate is 17 billion pounds of public money to get the first one operating. So it's a huge financial risk.

Chris - Can we just consider for a minute the practicalities of bringing this much energy down from space? This isn't going to produce a sort of death ray that if someone flies their aircraft through it, they get fried. Is it?

Mark - Well, the average microwave input into the collector is only about two or three times that of the average solar radiation falling on that patch of Earth. Generally, it is thought that there's no obvious danger for microwaves at the intensity which this satellite system will operate at. I'm not sure how much experience there is with microwaves at that intensity to be certain.

Chris - And if I gave you 17 billion quid, would you spend it on this?

Mark - No.

Chris - Would you spend it elsewhere? And if so, what would you do?

Mark - I would spend on things like innovation, technology development, on the electric vehicle batteries, for example. More efficient equipment, more efficient, small scale, low cost heat pumps. Better solar panels for buildings, better wind generators, production of hydrogen, production of ammonia. All of these things need innovation and development. And the markets for them are huge. And they're more or less driven now largely by private companies selling them into competitive markets, whereas solar satellites, you can't ever see that happening, really.