This could very fast become economical. Direct conversion from heat to chemicals (without intermediate electricity production) could reach very high efficiencies if the right catalysts are found. Mass-production of the mirrors could make them extremely cheap. The catalysts they talk about use abundant and cheap elements.
The productivity per acre will anyway be many times higher than even the best immaginable algae, and of course many times more easy to handle, extremely stable (even compared to algae) and you have directly the desired chemicals. I am very pro-algae because they will have to replace large part of traditional agriculture, but in the long run, the way to go for chemicals (and fuel) is direct solar-to-chemicals.

I'm all for converting flu gas into hydrocarbon fuels, or other useful products, but I thought algae was far more efficient at using sun light to lock up emissions than synthetic photosynthesis.

Some of the proposed uses for this concept are ridiculous. Convert CO2 from a coal plant into fuel? It will take more energy to make something out of CO2 from a coal powerplant than it generates as electricity. If you have that energy, why burn the coal in the first place?

If you can store CO2 from cement production (or make cement with solar heat), that makes sense.

It is going with what we have, 600 coal fired power plants are not going to be replaced over night. If you gasify the coal and use IGCC you have the carbon before you burn. Turning it into fuel for cars makes sense because we have millions of cars and would like to reduce imported oil.

@Alain - You are completely right! Except for how you use the term "catalysts" - In the case of this process, the solid redox materials used are part of the reaction, for example they split CO2 or H2O to CO or H2 by oxidizing iron to iron oxide in one step (transferring the oxygen atom), then reduce the iron oxide back to iron in the high temperature step, releasing oxygen (they actually use mixed-metal oxides with iron and other metals, but this is just an example).

@HealthyBreeze - Synthetic photosynthesis type processes are much more efficient than natural photosynthesis. The best land-based biomass is around 1% efficient in sunlight-to-chemical energy and biofuels from traditional crops like corn are closer to 0.2%. I can provide references if desired (or just look it up). Even with commercially available photovoltaics (10-20% efficiency) and electrolyzers (60-80% efficiency) you are at 6-16% efficiency, so you will need about 1/10th the land of land-based biomass. Algae is a bit better but not as high as non-biological methods.

@Engineer-Poet - There are certainly better CO2 sources, such as aluminum and other industrial plants, and CO2 captured from the atmosphere (http://www.scientificamerican.com/article.cfm?id=washing-carbon-out-of-the-air), but it is not completely ridiculous to use CO2 from a coal power plant. If you are running coal power plants you can either sequester the CO2 you have produced, or recycle it. To recycle it you obviously need renewable or nuclear energy. Solar electricity is not yet economical to replace the coal power plant. It is possible that their solar heat-driven process could be inexpensive enough to produce fuel (and would be competing with gasoline and biofuels, not with the electricity of the coal power plant). Heat is cheaper than electricity which is what attracts the researchers to such a process rather than electrolysis.

Finally, at this stage there is no reason to believe this process will ever become economical, but the research should continue until it is clear whether or not it could be.

I looked at the feasibility of this several months ago –from the perspective of research investment. It does not look promising at all. The main problems are: very low conversion – roughly 5% and exceptionally high energy requirements.

The process also suffers from the usual problem of researchers failing to address H2 separation after conversion. It doesn’t do any good to get low conversion without an economical means of separating the “fuel” from the inerts/steam.

While I have worked with Sandia on other projects, at this stage I would place this “technology" firmly in the snake oil category.

@Dave Kelly - I agree this does not appear to be the most feasible way to recycle CO2 into fuels. But that does not mean research should not continue on the process (you yourself should certainly not invest if it does not look promising; I do not plan to either).

@Will S - The EROEI is most likely similar to PV, e.g. high. You invest energy in building the system, then you collect free energy for its lifetime, which quickly "pays back" for the energy you invested. It will not use waste heat to run the system since it needs heat at 1400 oC or whatnot. Why would you need to use waste heat to come out greater than unity?

The entire front end of the process shuts down every night. Consequently, the entire syngas train is in recycle mode most of the time. The intermediate product is mostly methanol, costing $1 per gallon made from natural gas. The economic viability is therefore questionable unless the process is government subsidized.

After going back over the older posts, it looks like this scheme can convert oxidized carbon and hydrogen to reduced forms (H2 and CO, plus O2). I'm going to assume that the thermochemistry works. I realize that the ideal thing to do would be to use solar thermal engines to just replace the fossil fuels, but it looks like the intent of the scheme is to convert the effluent from cheap fuels (coal) to feedstock for much more valuable products (motor fuel). The CO and H2 could just be burned instead of coal or natural gas, but storage is an issue and that's not the most favorable product in today's market.

Recycling CO2 instead of distributing it in the atmosphere has a growing value. If the value of the CO2 removed is factored in, the cost of the liquid fuel produced would be much lower.

It would be interesting if there were a good way to make CO from CO2 and thermal energy that is easier than making Hydrogen from water and thermal energy. Carbon-Monoxide can be converted quickly into methanol which is easy to store and use in engines.

The people who are trying to promote solar energy rarely have any property to do it on. Solar energy is free but so is coal and oil. We just have to pay to collect it. This requires large tracts of land covered with some kind of equipment. No body seems to want to give up any land to anyone else even at a good price if they think that it is part of their tradition.

The price of making solar fuels of electricity is too high for an industrialized country.

In the 1960s The Sierra Club would not have tolerated for a minute vast tracts of large wind turbines. They now have to pretend that they are not clutterning up the natural environment because they want to pretend that renewable energy exists. Every bit of energy on the earth is nuclear energy at its source. The sun and other stars are just creating new atoms.
..HG..