[H2-PV]

Originally Posted by robertp

Concentrating Solar Power (NOT photovoltaics) can provide both electricity and desalination.

Any solar system can provide both desalination and electricity. It's an engineering decision, not a physics problem. Neither one automatically provides both, and you are underestimating the challenges in maximizing productivity of either by trying to make one system do two jobs both well.

Originally Posted by robertp

Every year, each square kilometre of hot desert receives solar energy equivalent to 1.5 million barrels of oil. Multiplying by the area of deserts world-wide, this is nearly a thousand times the entire current energy consumption of the world.

The cost of collecting solar thermal energy equivalent to one barrel of oil is about US$50 right now (already less than the current world price) and is likely to come down to around US$20 in future.

So? Each square kilometer of the sun does even better -- in both cases there are engineering challenges and delivery challenges. The cost of transporting electricity is $1.5 megabuck per miles of high-tension transmission lines. The further you transport, the higher the costs.

Water, being infinitely heavier than electricity, costs extravagantly more to transport long distances. Flippant statements about "teleporting" power costlessly from where it may be abundant to where the people are is just throwing sand in peoples eyes to blind them and delay deciding on choices that make sense in the immediate future.

Why don't you suggest unicorns could transport the electricity and purified water to the world's billions?

Originally Posted by robertp

An area of the Sahara of 254 km × 254 km would generate the equivalent of the entire current world demand for electricity.

Waste heat from electricity generation in a CSP plant can be used to create fresh water by desalination of sea water: a very useful by-product in arid regions.

It takes a 40 degree C difference in temperature to operate Stirling Engines to produce AC electricity, and PV systems with coolant can do that in temperate climates where the people actually live. CHAPS is combined heating and power solar, and has produced real-world total efficiencies of near 60%.

The "Sahara Red Herring" is unicorns again. There's no water to desalinate in the Sahara, and no way to get the mythical desalinated water to say, NYC.

Originally Posted by robertp

A CSP plant in California has been supplying electricity to around 500,000 people since 1985.

A recent report from the American Solar Energy Society says that CSP plants in the south western states of the US "could provide nearly 7,000 GW of capacity, or about seven times the current total US electric capacity".

The technology is relatively simple and robust, and apart from the energy used in construction, is totally carbon-free. The fuel never runs out (unlike uranium, coal, gas)

see www.trec-uk.org.uk for much more detail.

So What? At a megabuck per mile it doesn't pay back to string wires to some of the best locations for solar or wind. Las Vegas is where it is because organized crime could manipulate a sparse population to vote for legalized gambling, not because a lot of people thought that living in deserts was the best idea. If it wasn't for the Hoover Dam nearby there wouldn't be any Las Vegas despite the high solar potential.

You are throwing around random facts casually without thinking it all the way through.

In some distant stranded places the highest use of renewable energy is to convert it straight into purified silicon PV and move it by truck to where the people are. It takes 1.2 kilograms of purified silicon to make one meter square of 13% net efficiency PV. A standard 18-wheeler big rig can move 40 tons a trip, 30240 meters square, 3,931 kilowatts per trip. With two drivers that one truck can make 200 trips of 1,000 miles each way round trip. The truck costs less than one quarter of mile of high-power electric transmission lines, and delivers 786,240 kilowatts of new PV waferstock per year. For the cost of one mile of wiring you can run five trucks from the stranded windfields of the Dakotas to Phoenix, Arizona, or Las Vegas. Once the PV is where the transmission lines already exist and are paid for, then you can plug in all that PV to the national grid.

Hydrogen Gas transmission pipelines is $600K to $900K per mile, compared to $1500K per mile of wiring. H2 gas in co-gen fuel-cells is nearly 100% efficient in providing both lights and heat/cooling/hot-water, given the best engineering known today. Co-gen is not just for CSP, but can be used with many power options, so all your arguments FOR CSP are also arguments FOR H2-PV equally.

A Molten-Carbonate (MCFC) or Solid-Oxide (SOFC) Power Plant-Sized Fuel Cell in the Megawatt range is also 1000 degrees C desalinator if you engineer it to do that.