02 Dec 2020 18:33 IST

Are space solar stations round the corner?

If there was ever an instrument to fight climate change, it would be this. However, cost is the hurdle

First, a caveat : while this is far closer to reality than science fiction, this is not likely to happen any time soon.

But why should we care? After all, solar energy has been around since the first satellite was launched in the 1960s, but it took till now for it to become ubiquitous.

Likewise, the idea of a solar station in space — oh, a really, really big one — is nothing new. Like any good satellite, this space station would orbit the earth. It can be slotted so that it always faces the sun, collects energy 24x365. Never a night or a cloud to hamper its working.

But how to get the energy down to the earth? Well, that’s again no issue. Convert electricity to microwave, beam it down and reverse the process here.

As a concept this has been around for decades. And, every element of it is technically feasible, but there are a bunch of issues to resolve. For instance, where would you put the space solar station? If you want the station to beam energy to a particular region, the station would have to be right above the region all the time — it would then have to be positioned, like a telecommunications satellite, at the geosynchronous orbit. This is 36,000 km above. However, if you want your station nearer home, say, in the low earth orbit, then you’d need several receiving stations on the earth. Secondly, you’d have to develop protocols on how to share the energy, what happens when the beam gets disturbed and points to a region other than the collecting station.

These are issues to resolve but not big challenges, apparently.

Permanent clean energy?

Just imagine the upsides! Caltech University scientist Sergio Pellegrino says the solar station up there would receive eight times as much energy as one down here. Some experts estimate that 2 million MW of capacity could be put up. Clean energy permanently delivered — if there was ever an instrument to fight climate change, it would be this.

So, what is holding us back? Why hasn’t this happened yet?

The answer is, in one word: cost. It costs money to send stuff up — the more the stuff or the higher you go, the more the cost. Now, if you want to take millions of solar panels to 36,000 km above the earth, imagine the rocketry you would need! That’s why we don’t have one right now.

But, breakthrough technologies have always happened only when multiple disciplines come together. Today, fortunately, the cost of rocketing stuff up to space is coming down due to inventions in both rocket technology and fuels.

Reusable rockets

Today, private space companies such as SpaceX and Blue Origin are advancing with reusable rockets. Others are trying out other tricks. For instance, it is now believed possible to take a rocket, tethered to a balloon (or balloons) up to a certain height, say, 15-20 km, and then fire it for onward journey — you avoid lift-off on earth, which is the most fuel-consuming part. Less fuel implies less cost and more space for payload. Then there are air-breathing rockets on the anvil — they pick up oxygen from the air, so there is no need for a chamber-full of oxidizer that the conventional rockets have.

Going forward, there is an expectation of a metal hydrogen fuel. Metal hydrogen? Surprised? Yes, there are experiments happening and one of them has even claimed success in fabricating metallic hydrogen, on a tiny scale, but the stuff disintegrated before it could be tom-tom-ed around. Nevertheless, it marked the crossing of a milestone in the research. Metal hydrogen would pack a heck of a lot more energy and would, therefore, be a great rocket fuel.

All these go to reduce the cost of putting a kilogram of stuff in space. The pathway is visible, that is why today the murmurs around space solar stations are getting louder.

Space solar stations

In March 2019, Forbes magazine picked up a story from a Chinese language publication and put out an article on China’s plans for building a space solar station. While China’s plans have not been made public, it is clear that the country is working on this project.

A little less fuzzy is a project of three scientists of the Caltech University, supported by Northrop Grumman Corporation. Here is what the Space Solar Power Initiative (SSPI) has to say about itself:

The goal: the creation and launch into orbit of thousands of identical space vehicles to form a constellation that maintains a precise shape. In the airless weightlessness of space, each vehicle will transform itself into an element of a modular power-generating space station with the square mileage of a city park, each module unfolding into a structure with the thinness of paper, made up of a network of billions of greeting-card–size tiles.

Pellegrino says that when they started they thought, ‘maybe launch costs will come down’ but decided it would not be wise to count on it. They just assumed that launch costs would remain the same. So, they said to themselves “let’s make the structure super-lite”.

In terms of beaming technology, it is being said that the ‘millimeter wavelength’, as used in 5G communications, could be used, to improve efficiency. So, you see, advancements in disparate disciplines are coming together. It is not inconceivable that a space solar station will become reality.

Just give it time.

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