Solar power has the potential to solve all of humankind’s energy problems. The amount of solar energy that reaches the surface of the Earth, per year, is somewhere in the region of 8,000 times higher than our current power requirements. If we were to cover just 1% (or indeed 0.01%) of the Earth’s surface in solar panels, we would have more than enough electricity to satiate society’s current and future needs. It isn’t that simple, of course, otherwise we would’ve already done it.

For a start, solar power is unreliable: Fluctuating weather conditions, seasons, and the day-night cycle all mean that solar farms on Earth can never reach optimum efficiency. Then there’s the matter of power transmission: The sunniest parts of Earth are generally the least densely populated, and it’s virtually impossible (and incredibly inefficient) to move power from the Sahara to, say, Europe. Then there’s the initial outlay: A typical solar power installation might produce around 150 watts per square meter — and for large installations, the price per watt is now around $1. To cover 1% of the Earth’s surface (about 5 billion square meters) would cost around $750 billion — a figure that isn’t completely untenable, but way out of reach of any commercial entity.

Another intriguing option is space-based solar power (SBSP). In short, SBSP would place a solar farm in geosynchronous orbit (35,786 km, 22,236 mi) and beam electricity back to Earth using microwave- or laser-based wireless power transmission. Outside of the Earth’s atmosphere the SBSP installation would receive about 30% more power from the Sun, would be operational for almost 24 hours per day, and of course would not be affected by Earth’s weather systems. If such a solar farm was placed over the equator, it wouldn’t be affected by the seasons, either.

Perhaps the most exciting aspect of space-based solar power, though, is the ability to beam power to whoever needs it most. An SBSP installation could provide extra juice for the dinner rushes in Tokyo, Shanghai, Delhi, Istanbul, Paris, London, New York, and Los Angeles, all without breaking a sweat. Try doing that with grid-based power, which cannot easily be transmitted over a few thousand miles. (See: The hunt for alien, star-encompassing Dyson Spheres begins.)

SpaceX

So why hasn’t NASA already launched a space-based solar power plant, then? Because, like large-scale solar power here on Earth, it’s incredibly expensive to launch things into orbit. It currently costs around $20,000 to place a kilogram (2.2lbs) into geostationary orbit (GSO), and about half that for low-Earth orbit (LEO). A large SBSP plant would weigh thousands of tons and would cost billions to place into orbit — and that’s even before you factor in the assembly cost (astronauts are not cheap labor). Suffice it to say that, as it stands, SBSP isn’t feasible.

All that’s set to change, however, with the arrival of SpaceX, Deep Space Industries, and other commercial space agencies (See: SpaceX launches first commercial resupply mission to the ISS.) SpaceX’s CEO, Elon Musk, has said that he wants to bring the price down to $500 per pound — at which point, SBSP becomes a lot more realistic. It is because of this prospect that there has been something of a resurgence in interest in SBSP. The Japanese government, in the wake of the Fukushima disaster, wants to launch a two-kilometer-wide 1-gigawatt SBSP plant. The Russian federal space agency, Roscosmos, has a working 100-kilowatt SBSP prototype, but no announced launch date. China plans to put a 100kW SBSP into LEO by 2025.

Most notably, though, John Mankins, the CTO of Deep Space Industries and 25-year NASA vet, has produced a new, contemporary report on the viability of SBSP [PDF]. His conclusion, in short, is that it should be possible to build a small-scale, pilot solar farm dubbed SPS-ALPHA for $5 billion — and a large-scale, few-mile-wide power plant for $20 billion. NASA’s funding for SPS-ALPHA dried up last year, but presumably Mankins’ work continues at Deep Space Industries.

Beyond the initial outlay, there are other factors to consider, too. For a start, a large SBSP plant would be very susceptible to damage from space debris, which in turn would create more space debris. It’s also not clear how long an SBSP installation would remain operational: Space is a hostile environment where solar panels rapidly deteriorate. It’s no good spending $20 billion on a solar power plant if it breaks down before it breaks even.

With that said, though, it’s important to consider space-based solar power as one part of the bigger space travel, exploration, and colonization equation. (See: Deep Space Industries to begin asteroid prospecting by 2015, mining by 2020.) It might cost a prohibitive amount to launch a single SBSP plant, but, as with the Apollo program, we must look at the bigger picture — a picture that includes space elevators, fusion power, asteroid mining, and space bases on the Moon and Mars. At some point — perhaps sooner rather than later, if global warming persists — we’re going to have to work out how to lift large objects into space. Launching a clean, green, endless source of power seems like the perfect starting point.

Now read: Nuclear power is our only hope, or, the greatest environmentalist hypocrisy of all time