Solar Energy Plant Creates Fuel

Normally, when you think of solar power, you think about photovoltaic cells or using the sun to generate steam. But engineers at Synhelion — a spin off from ETH Zurich — had a crazy idea. Could you reverse combustion and change waste products back into fuel? The answer is yes if you can use the sun to turn things up to 1,500°C.

The input is water, carbon dioxide, and methane into syngas. The pilot plant in Germany is set to begin operations using a thermal storage device to allow the plant to operate around the clock. The new plant is slated to produce several thousand liters of fuel a year. Future plants will produce more, and they are targeting a cost of $1 per liter of fuel. The pilot plant has a 20-meter-tall tower and around 1,500 square meters of mirrors, producing 600 kW of output. The hexagonal mirrors are very thin, and the plant uses drones to aim the mirrors quickly compared to other methods.

Syngas shows up a lot lately. Getting to 1,500 degrees is a big ask, although we’ve seen ETH Zurich get to 1,000 using solar.

24 thoughts on “Solar Energy Plant Creates Fuel

  1. Synthetic fuels are the next step in the transition away from pure hydrocarbon fuel. This is a good example of using solar to that effect. I didn’t see in the linked article what the efficiency of the process was. Also “thousands of litres per year” is not even a drop in the bucket to meet demand. Hopefully this is scalable and will be more than a one off pilot plant.

    1. Umm… Synthetic fuels ARE pure hydrocarbon fuels. The difference is the source of the hydrocarbons and their purity. Previously, relatively impure hydrocarbons were taken from earth puss (oil), excising infection from lesions and abscesses in the planet, turning that toxic ooze that would otherwise continue to fester and seep, killing everything around it, into fuel to produce energy. In this case, it’s hydrogen from water, CO2 from the air, and sun energy to form the purest of hydrocarbons to use as fuel, releasing a bunch of oxygen as a byproduct.

      1. Sorry I should have differentiated between the “purely” prehistoric produced hydrogen carbons made over the eons by natural processes and those produced by recent man made means,

      1. With the taxes on fuel and general fuel prices in the EU, the efficiency doesn’t have to be all that great to break even economically.

        The approximate resale cost of fuel in the EU is 20-25 cents per kWh. The LCOE of solar thermal in the EU-27 is right in the same ballpark, so you’d need 100% efficiency to meet the price.

        However, there are other processes that are much cheaper. Like on-shore wind power which has an LCOE around 6 cents per kWh so your efficiency can be terrible below 50% and you’re still making money – assuming the government doesn’t tax and kill your business.

        1. Although, the LCOE of solar thermal is in terms of electricity. If you can use the heat directly, your process efficiency can be as low as 35% and still break even. In practice with all the taxes and other business overhead, you need to make it better than 70% to make ends meet.

          Still, it’s in the realm of possible with technology available today.

  2. Synthetic fuels can work as a niche substitute (especially for large aircraft where there are few alternatives) but not a mainstream solution due to how energy-intensive they are to make. I remember there was a study done around 2020 that showed that if all fossil fuels were to be replaced by synthetic e-fuels at that time, world electricity production would need to triple or quadruple to provide the needed energy capacity.

    1. This is actually true in general. We will need four or more times our current electricity generation to replace fossil fuels. This alone is not insurmountable, however, it is going to take time, and we may have to overspend on electricity in the transition. That is where the efficiency of fuel conversion comes into play. If you got only 50% of the energy converted into e-fuel, you probably would be better off Just electrifying the sector, but also that does take time, and we don’t really have that. So we need the transition solutions like this. If we could make completely degradable plastic entirely out of CO2 from the air, that would be a double win.

      1. But you have to remember that “fossil” fuels have advantages over electricity, refueling is faster (fuel tank vs. battery), long term storage, transport to remote areas, etc.

        1. Everything has advantages and disadvantages.

          Since the conversation is so often about electric cars I would like to point out that we are never going to have pipes conveniently bringing gasoline/petrol or diesel to our homes. But almost everyone has electricity!

          Sure… you can drive to a gas station, wait in line, dodge getting bumped into by the bad drivers. Realize that the pump you pulled up to is out of order so do it all again. And when you finally get the chance to fill that tank that part only takes a minute or two.

          But you can’t just park that gas car in your driveway at the end of the day near empty and come back to it full in the morning!

    2. >world electricity production would need to triple or quadruple

      That’s not all that unrealistic.

      Compare to replacing everything with batteries, which would require producing a thousand to a million times more batteries than we’re capable of today.

    3. Any process, given boosts at first, becomes more and more cost effective as the economies of scale kick in.
      This has been true for both PV and Wind, it’s now competitively cheaper I think even without the boosts.

      Nuclear power (another way to get those temps) — and future Fusion power — have the handicap of megaproject cost & time overruns, which small modular systems don’t.

  3. “The hexagonal mirrors are very thin, and the plant uses drones to aim the mirrors quickly compared to other methods.”

    Does this mean drones like quad copter drones? How does that work? That seems like an interesting subject that could have its own article if so.

    1. I did a little digging and apparently they’re using the drones to replace camera targeting like thermal collectors and parabolic concentrators use, but the hex mirrors have their own drive motors and deformation pistons/screws/whatever.

      My imagination is picturing lots of little drones bursting into flames for accidentally wandering a little off course.

  4. The result is a mixture of hydrogen and carbon monoxide. This is not a fuel source that can be compressed or liquefied or realistically transported, but rather must be used on site. It of course produces CO2 when it is combusted. An enormous amount of waste heat exits the system into the surrounding air. Handling must be safe because of the obvious toxicity of carbon monoxide.

    A Chemist

    1. A chemist should hear about Fischer-Tropsch synthesis. Input: Water steam, CO2, little bit of metal catalyst, lot of heat. Product: synthetic liquid hydrocarbon fuel. Known from 1930s.
      But now for niche use only.
      The question is effectivity, both energetical and financial.
      Photovoltaic and wind with appropriate batteries seems to be still cheapest way to catch and distribute solar energy.

    2. “It of course produces CO2”

      But you started with CO2 and methane. So why is that a problem? Even if there is more CO2 in the end than in the start. Isn’t that just the carbon input from the methane? Which is a worse pollutant than CO2.

  5. One of the feedstocks is methane, which the article says will come from bio waste. Hard to imagine that scaling to the amount required to replace fossil fuels in aviation.

    Nevertheless, creating any liquid fuel without pulling carbon out of the ground is a step forward.

  6. Is it just me or wouldn’t it be more effective to get the 1500C from a nuclear power plant than from a solar plant running when it’s nice out? Also wouldn’t any plant doing this get a crap load of carbon credits?

  7. I recall an article from the 90s discussing using a nuclear plant to generate synthetic fuels. They estimated they could get the costs down to $4/gallon. I would like to see a less expensive alternative, but using heat from nuclear fission plants to co-generate synthetic fuels makes a good deal of sense.

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