Boffins say their thin film solar cells make space farms viable

Boffins from two UK universities believe they've figured a viable way to make space-based solar farms feasible, and it doesn't even require any new-fangled or expensive technology to accomplish. The conclusion reached by the team from the University of Surrey and Swansea University comes after a first-of-its-kind experiment …

[IceC0ld]

possibly the answer to the problem lies n the name - SPACE BASED

we may NOT be able to get the energy back to Earth for NOW, BUT

maybe they could be used to power the next generation of satellites ?

or for space exploration in general ?

then, when the tech to grab the power back down to us IS established, then we get our solar space based farms ? :o)

[Bill Gray]

Not sure why you're being downvoted here.

This should certainly be useful for (for example) solar-electric (ion drive) propulsion, such as was used for the Dawn mission. Spacecraft using this usually have lots (and lots) of solar panels. Lower-mass panels means more payload or more power or some of each. There are probably some other space-based applications that could profit from having more or lower-mass solar power.

[Rol]

Some things would be best engineered in zero g, if not only achievable in zero g, so this could be where the output from the farms go?

[Filippo]

There's also the teeny problem that anything that can deliver large amounts of power from space to Earth is, almost by definition, one flick of a switch away from being an unstoppable superweapon.

[I am David Jones]

Not really, if you need a large tuned array of receivers on the ground, as seems to be the case

[Filippo]

Sort of. The energy per square meter delivered to the ground has to be a lot higher than what you can obtain by the same acreage of solar panels, for the whole endevour to make sense. I'd say at least an order of magnitude greater, probably more? Photovoltaics get maybe 30% efficiency, so even if you managed to tune this to 90% efficiency, in order to get an order of magnitude improvement on the ground you'd have to deliver over three times as much power as strong sunlight. That's enough to cause damage already, definitely enough to make people run away as fast as they can, and I believe I'm being extremely conservative with my guesstimates.

If the power density on the ground is significantly lower than that, the project doesn't make sense economically; just build solar panels, they won't make as much power, but they are cheaper and easier to maintain by, I dunno, two orders of magnitude.

[John Robson]

"If the power density on the ground is significantly lower than that, the project doesn't make sense economically; just build solar panels, they won't make as much power, but they are cheaper and easier to maintain by, I dunno, two orders of magnitude."

Except that your new power density doesn't have down time each day (at least not significant downtime).

a PV farm using sunlight has, on average, 12 hours of daylight - and there is a significant bias towards the middle of the day even during that time. A space based array could have virtually no time in the shadow of the planet, and therefore have a much higher load cycle, requiring lower power density for the same overall generation.

[jmch]

" A space based array could have virtually no time in the shadow of the planet, and therefore have a much higher load cycle..."

Since it would not have any place to store the energy it would either need to be at geostationary orbit (might be too high / far away?) or else need multiple ground stations to send energy to (requiring complex angular positioning / beamforming). The latter does sound exactly like something that could be weaponised.

[Filippo]

What jmch said.

Also, I realized that we're going to need a whole bunch of these installations, not just one. Even if individual arrays are only about as powerful as sunlight, the whole system can definitely be weaponised by adjusting their orientation to target overlapping areas (and they have to be able to adjust orientation). Depending on how many you have above the horizon and how nasty you feel, you could dial it anywhere from "make people uncomfortable" to "vaporize".

[phuzz]

There's another difference as well. Solar cells are designed to work with sunlight, which has a range of different wavelengths. Power beaming would (presumably) use a single, fixed, wavelength, which would enable the receiver to be much more efficient, and the wavelength can be picked to be less harmful (ie, no UV or higher energy).

[Filippo]

Yup, that's why I was assuming 90% efficiency, which I think is generous. If it's less efficient than that, the beam power needs to be even higher.

[Anonymous Coward]

Except you can have solar cells in/under the microwave reflectors, so you get both.

(I still agree with you that it's BS)

[NullDev]

Think of the plus side. At least you will have a nice source of heating for those cold winter months, because who doesn't want to microwave their whole house.

[DS999]

The earth side receiver would need to be 10x the size?

That math doesn't work.

Let's assume the space based receiver was located where it could get sun 24x7. It wouldn't produce what 10x the area of solar panels could on Earth averaged over a full year.

Equipping those earth based panels with a battery to smooth out their power output like the space receivers would deliver would be far cheaper than launching a kilometer sized array of panels into orbit even if the panels themselves were FREE!

[midgepad]

Re: The earth side receiver would need to be 10x the size?

IE almost anywhere around Earth orbit. I don't think the receiver is limited to accepting a beam fron one SPSS.

however, better to use the power outside the Earth's atmosphere, for tasks we should ban in the atmosphere to reduce heat dissipation into that atmosphere.

[DS999]

Re: The earth side receiver would need to be 10x the size?

The additional heat dissipation inside the atmosphere is a rounding error within a rounding error. The sun hits 100% of the Earth (the daylight side) constantly except for solar eclipses, and the surface area of half the Earth is roughly 100 million square miles. To increase the amount of solar heating by 1% we'd have to build 1 million square miles of arrays and beam all that power down to Earth. Even if you assume some of it hitting e.g. ice is reflected that's still an insane area we couldn't build in the lifetime of a baby just born five minutes ago.

I wouldn't lose sleep over this, even if we started building solar collectors as fast as we could we'd have centuries to figure out a way to balance it by orbiting mirrors that reflect the sun over parts of the ocean, distributing aerosols that reflect it in the upper atmosphere, or whatever.

[midgepad]

Re: The earth side receiver would need to be 10x the size?

That's not the dissipation.

The dissipation is from processing, and Bitcoin etc have been compared to the electricity consumption, production, dissipation and CO2 etc, of various medium sized countries.

[lowwall]

"A single satellite, for example, would need to have so many solar cells that it would measure at least a kilometer across, while ground-based receivers would need to be around ten times that size."

What matters is the net present cost per watt hour of this system compared to an oversized terrestrial PV + storage system that can deliver the same amount of reliable power.

I suspect that earth based will always be cheaper even if you have to build a pumped hydro facility to get the needed reliability.

[Neil Barnes]

Cadmium

I thought that was one of the RoHS banned chemistries - it seems it gets a pass for solar generation. I learn something new every day.

(I also vaguely recall that tellurium isn't a particularly friendly thing, either: Midgely used it before he settled on tetrethyl lead as an octane booster, and it made him very smelly...)

[david 12]

Re: Cadmium

I thought that was one of the RoHS banned chemistries

All solar panels are classified as toxic waste here (.vic.au). CdTe offers another excuse for Nimbys to complain and protest, but if you don't want a solar farm, you'll complain about anything. In solar panels the CdTe is tightly bound.

[Graham Dawson]

Or we could build a couple of next-gen nuclear reactors and have more power, from a smaller footprint, in a safe and reliable form that isn't subject to the inverse square law.

[Gene Cash]

Expense?

Like the article says, CdTe has been around for a while, but it's absolutely eye-wateringly expensive. It's so bad even Tim Cook might go "dang, that's expensive"

So are these any cheaper?

[david 12]

Re: Expense?

but it's absolutely eye-wateringly expensive.

It's used in massive solar farms because it's the cheapest kind of panel available. Either what I'm reading is wrong, or what you're reading is wrong.

[david 12]

only expected to work for a year

Here on earth, CdTe panels have completed a 25 year endurance test. I find it hard to believe that boffins actually expected the panels to fail in space after one year.

The document referenced is behind a paywall,

[Paul Crawford]

Re: only expected to work for a year

Here on earth, CdTe panels have completed a 25 year endurance test.

Without the harsh UV and ionising radiation, I expect...

[The Kraken]

Oh great - let’s cook the planet even faster.

Last thing we need is more thermal input.

Better would be to make smarter use of what we have and if possible, use less.

[the Jim bloke]

Yes but people suck

I do agree that better efficiency and simply not spending energy on stupid stuff would be far better,

but con artists will continue to promote crypto, and nobody wants to give up their air conditioner or heating, and business will continue to head down capital intensive/reduced labour automation etc etc etc.. Not to mention former third world countries wanting to be "developing nations" and cremating the environment to get there.

so power demand will continue to rise, and someone is going to make a buck providing it,

Generating and transmitting power anywhere inside the atmosphere is going to leak heat into the atmosphere, but at least most of the renewables are grabbing energy already in the system, so its only manufacturing the collectors and infrastructure plus transmission leakage - and if you can get a granular renewables network with local collectors and storage, you will get less leakage than from massive centralised systems..

The simplest solution to global warming would be to reduce solar input outside the atmosphere - except we absolutely lack the capability to do that. If we could harness environmental heat and convert it to non thermal use - that would be nice... kind of like what a wind turbine does, only it would totally screw up the climate if we did it at significant scale