Keith Henson

And the steam made from reactor heat isn’t released into the atmosphere, though you do sometimes see condensate on a cold day from water evaporated in cooling towers

The best approach might be for you read the Wikipedia article. http://en.wikipedia.org/wiki/Desalination.

Keith Henson

“Solar panels, . . . deteriorate over time.”

That’s true. We can either have a replacement program or just build solar thermal. Thermal plants are competitive with solar cells on earth, no reason they would not be in space. And thermal plants often last for 50 years.

“Another issue is that market-rate generation assets need to be sized right around 500 MW to be useful.”

Because there is no fuel costs, the economics of operating power satellites is very different from earth based coal plants. We would operate space based solar plants at full capacity all the time and vary the *load.* How? Divert any power you don’t need at the moment into making hydrogen. Then use the hydrogen plus CO2 out of the air to make synthetic oil to feed to current oil refineries. Thus a one or even a 5 GW unit can operate just fine at 200 MW.

Eventually space based solar power will be sized for peak load and well beyond and the main draw would be making synthetic oil. Lose a few 5 GW units and you just make a little less oil that day.

“Solar power from space may seem like a good idea at first blush. Unfortunately, the devil is in the details. One of those details, the fact that we live in a Capitalist (market-driven) society means that one of the significant cost factors with developing and deploying an SPS will need to change dramatically for an implementation to make sense. The cost per kg of orbiting material, the durability of solar panels, and the conversion efficiency of solar panels are three of many significant factors.”

Solar thermal is nearly 4 times the efficiency of solar cells. You definitely nailed the main factor, cost per kg to GEO. In my design to cost work, I found that a target of $100/kg is about right. At that lift cost, power can be priced at 1-2 cents per kWh.

“The relatively low up-front cost of implementing terrestrial power generation using known technologies is another challenge that SPS technology has to overcome to be viable.”

Exactly. For space based solar power to attract the investment it takes, it should be able to make power for perhaps half the cost of the next most expensive option.

“For instance, wind power runs around $500,000 per MW of capacity, and that’s considered very expensive.”

That’s $500/kW which is a very good price if you could get it all the time. On a capital investment of $800/kW you pay off the investment in ten years at a penny per kWh. What power per MW of capacity can you get in a year from wind?

“At a two percent net energy conversion rate for an SPS (after solar panel efficiency loss, transmission loss, DC to AC conversion loss, etc.),”

The worst I can imagine is 15% solar cells feeding a 50% efficient electricity to electricity transmission chain. More likely would be 60% thermal cycle, 30% after transmission. But when the “fuel” is free, the only cost is capital equipment.

“the cost to implement a market-viable system is overwhelmingly large. I think we’re better off putting our money into developing better nuclear technology. We know how to make THAT clean, we just don’t, mostly out of fear that it might be weaponized, even though it already has been. If you want to argue for something, argue for that.”

Done the only way I know to get the cost down, the power satellite propulsion lasers *are* weapons. But I agree with you, nuclear perhaps 5 cents a kWh is the next best choice.

The trouble is you are never going to make dollar a gallon liquid fuels on 5 cent a kWh nuclear electricity.

Keith

It’s not really a problem because with today’s technology building a power satellite would be an insane waste of money.

With the kind of transport into space we have today, a one GW, 5000 ton power power satellite at $20,000/kg ($20 M/ton) would cost $100 B just to lift it. I.e., $100/watt or $100,000/kw Paid off in ten years, the power would cost $100,000/80,000 hrs or $1.25 per kWh.

The same $100B needed to lift one power satellite on current rockets is more than enough to develop a transportation system that lowers the cost down to $100/kg, a reduction of 200 to one.

Which is why building a test power satellite with current rockets is silly. For the same money we could set up the transport to build hundreds of them.

If we are transporting a million tons a year to GEO, maintenance isn’t a big deal.

Keith

Besides, what can go wrong with one of them?

Keith