"All the tax money being spent on biofuels would be better spent on converting to solar."

Not unless people get a lot more electric cars (not hybrids, true electrics) and solar-power them.

In the USA, less than 3% of our electricity comes from burning petroleum, and the percentage keeps dropping as old systems are retired. Oil is just too expensive compared to other methods. (Wind will soon supply more kWH than oil, if that hasn't already happened.)

Biofuels (mostly ethanol) are basically a stop-gap to stretch the gasoline supply, used for auto transportation, not electricity.

The PV panels described would replace coal, natural gas and nuclear generation of electricity. They won't save much oil at all, if any.

The real breakthrough PV needs is to reduce the dollars-per-watt.

"The principal problem with solar energy, as the column correctly points out, is that the sun shines less than half the time, on average, at any location on earth."

No, that's not it. The big problem is that the total system cost of the panels, conversion equipment, etc., is still rather high for the energy recovered, compared to other technologies.

"However, a satellite correctly placed in geosynchronous orbit can receive direct sunlight 99% of the time."

That's true. But it's 27,000 miles or so away from where it's needed.

"a network of solar power collector satellites could collect enough energy to power all current uses on our planet, with no adverse environmental consequences."

I call shenanigans. Almost everything we do has adverse environmental consequences.

"The energy collected by space-based solar power satellites can be transmitted wirelessly to the earth's surface as microwaves, and fed directly into the power grid with minimal processing."

Not really. Let's think about this a moment....

First we have to build the satellites, which must be capable of enduring the space environment for decades. They have to contain not only the panels but the microwave conversion equipment and antennas. Plus they must beam the microwaves to a precise location on earth where the collectors are, and be absolutely safe against misalignment (or they will cook whatever the microwaves hit, if the energy density is high enough to be useful.)

How much would it cost per watt to build such satellites? Granted, they could be mass-produced, but even with such economies we're talking about a lot of very expensive hardware.

Then we have to launch the satellites and get them into orbit. These are huge satellites, too, if they're going to collect and process lots of energy.

How much would it cost per watt to launch them?

There will also be needed a system of ground collectors to intercept the microwaves and convert them to useful electricity, and feed it into the grid. How much will all that cost?

Consider all the losses in the system beyond just the PV panels, using wildly optimistic numbers:

- Conversion of DC from panels to microwaves: 50%

- Transmission from orbit to earth: 50%

- Conversion from microwaves to useful energy: 40%

0.5 x 0.5 x 0.4 means that for every 10 watts of electricity from the orbiting panels, we get maybe 1 watt of useful electricity on earth. Maybe. The advantage of 99% sunlight is lost in all the inefficiencies of getting the electricity to where it's needed. And those are wildly optimistic numbers; transmission of useful energy over long distances by microwaves is totally unproven technology. The reality might be 100 to 1 rather than 10 to 1.

Now add in all the energy needed to build the satellites, launch them, and keep them in orbit. Think of how many would be needed just to power one typical American city, given all the inefficiencies.

Then add up how much it would all cost. Remember too that we'd probably need a manned spaceflight system that could reach geosynchronous orbit to repair them. What would that cost?

Earth based systems start looking really good...

"Why doesn't the author of the article mention this option?"

Because it's not even close to being realistic compared to ground-based systems.

"It deserves to be discussed."

Yes, it does, to determine just how much it would really cost to do, and all the ramifications.

How much are *you* willing to pay per kilowatt-hour? That's the bell-the-cat question.

There's an old saying:

"Engineering is doing for a penny what anyone can do for a pound".