Producing fuels from 1,500 degrees of solar heat

> "annually producing several thousand litres of fuel."

That's maybe 10 liters a day. Seems low for the size of the installation. A liter of gasoline is about 10KWh. So if this thing gets 5 hours a day of full sunlight, it's putting out 2KW. That's like 5 standard solar panels.

Either I'm calculating this wrong or this is insanely inefficient.

> It uses an AI-based method involving drones to calibrate the mirrors 200 times faster compared to traditional techniques using cameras, Synhelion says. Precision is key to ensure the mirrors track the sun and efficiently reflect its light into a solar receiver at the top of a 20 m tall tower.

Naively I would assume we know where the sun is and how to calculate the angles. What are drones and AI doing?

This is just using solar heat to reform methane from biogas. I was hoping it would be using solar heat for production of the reduced chemicals from water or CO2. This latter problem is much harder, but there have been proposals, for example using heat to reduce transition metal oxides with evolution of oxygen, then reacting the oxides with steam to make hydrogen.

M2O3 --> 2 MO + 1/2 O2

2 MO + H2O --> M2O3 + H2

This sounds very cool, but "annually producing several thousand litres of fuel"?

An average US car consumes ~1800 litres/year... So this 600 kW solar facility is just enough for one or two cars?

A random search shows you need ~2kW worth of solar to charge your electric car daily, so this technology needs to improve a lot to be competitive with batteries. Hopefully they figure it out before they build the full-size plant.

"This heat powers a thermochemical reactor that turns CO2, water and methane into syngas"

The methane has to come from biomass, so this isn't quite closing the loop here on a full solar only process. Pure CO2 and water to synfuels is still wildly energy inefficient.

Several comments... Disclaimer, I work in this space.

a) Surprised that on HN no one has commented on the similarities with Heliogen: https://www.heliogen.com/ This US-based company backed by Bill Gates and Bill Gross similarly focuses on high-temperature heliostat applications, e.g. green hydrogen and concrete etc. They even have similar hexagonal-mirror heliostats. b) Why these CSP startups so often focus on moon-shot 'super hard' applications like the above baffles me. There are LOTS of great applications for lower temperature solar thermal systems - which are much easier to build and operate. Our plastic-molding systems are just one example: http://lm.solar c) It's a little odd to be doing CSP in Germany - Heliostats need collimated light (non-diffuse light, e.g. light that casts a shadow) and Germany has pretty low DNI compared to, say, Morocco. I know the article says they plan to deploy commercially to Spain, but even a test system would be super hard to operate with frequent haze, high cloud layers, etc. To be clear, not saying PV-solar is impractical in Germany - PV can harvest diffuse light just fine.

Funny that the photo of the solar tower / target in the article shows an overcast sky! Global Solar Atlas gives annual average DNI of @ 1000 kWh/M2/year at Jülich, which is way low. https://globalsolaratlas.info/detail?c=50.922093,6.361102,11...

I wish them luck, but there are likely more practical, impactful uses for CSP.

PS Re the 'sunlight is free' comments... yes but if your process is very inefficient and/or requires a huge heliostat array then CapEx goes way up (which has to be financed = cost) and then you get into needing automated cleaning robots to keep your array working well (see Ivanpah - https://en.wikipedia.org/wiki/Ivanpah_Solar_Power_Facility ), etc.

The cascading effects of moon-shot application => huge CSP system => problems (high CapEx, huge physical sites, permitting problems, need for automated cleaning etc) are exactly why we're working on industrial uses for SMALL heliostat arrays. And why grid-scale CSP (electric generation) systems generally get trounced by PV+battery systems.

I have no idea if technology like this will prove to be scalable, economically competitive, or even practical… but it does seem pretty dang cool as a concept

If they get some traction, it might be interesting. It reminded me of another project which I have almost forgotten about.

David Doty is a respected name in a narrow circle of nuclear magnetic resonance scientists for the hardware that his company builds [1]. At some point about a quarter century ago, he became obsessed with what he saw as an impending energy crisis, and started to look precisely into the technical nuances and economics of Fischer-Tropsch process. It seemed like a potential solution to turn excess of renewable energy into an energy-dense liquid fuel, which could then be distributed using the already existing infrastructure.

Doty was always exceptionally meticulous in anything he did, and so he went with a fine comb to find and eliminate inefficiencies in the fuel synthesis process, wherever it was physically possible. He funded a small team working on this, and they came up with some improvements [2] which they have patented, presented at conferences, etc. But despite all this work the economics of the process was still not favorable.

[1] https://dotynmr.com/ [2] http://www.dotyenergy.com/

At this feeble level of efficiency we’re probably better off using the energy to split water into hydrogen or producing ammonia.

It’s a trade-off ultimately, either we get to use currently deployed ICE systems and feed them with this solar fuel, or deploy new engines to leverage hydrogen or ammonia based vehicles.

Most probably better to bet on electricity storage tech catching up and just switch everything to full electric.

In my view, it sounds like they're trying to tackle way too much at the same time.

Just the core system that converts input chemicals and heat to a fuel is a major undertaking. Focus on that.

Adding their own mirror system might be doable, but only if they use a well known and simple solution.

Trying to add an "AI drone mirror autocalibration" is a major undertaking, enough to keep a medium sized company busy for a number of years.

Likewise with the "solar energy storage system". Just run when the sun is shining, and produce as much fuel you can from that.

If you have more incoming power from the sun than what you can produce fuel from, concentrate on solving that instead. Or just build something that is economical even if the mirror system is way oversized in order to always keep the fuel conversion busy.

> What if they could reverse combustion and turn carbon dioxide and water back into fuel?

Humbling thought that the green weed outside your window is doing exactly that - plus, depending on the species, tens of thousands of variations on a carbon theme.

Seems like cool concept, basically it's just solar furnace with extra steps - to me it is a bit nonsense that it is placed in Germany because there are far better locations on a globe like Chile with 10 times more solar energy per m2.

I am glad, however, that the idea of solar furnace is still being explored. Yesterday I was wondering if such installation could be put on a large ship vessel which would solve problem of year season. Also with our knowledge about tornado formations the ship could be put in places with max solar input.

Related:

Fischer–Tropsch process

https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_proces...

They should come up with a way to turn leaves into oil. Send it down fractured wells and pump it out 10 years later.

There used to be a company that tried to do this to directly generate electricity: eSolar (https://www.cbsnews.com/news/an-interview-with-esolars-bill-...)

Reading the article I get a feeling that it's more like proof of concept, than a economically feasible project, as there's no mention of costs.

Many years ago I remember seeing this same focused sunlight design being used to generate electricity directly from the heat.

This concept is not quite smoke and mirrors, since there's nothing wrong with the science, but this article definitely reads more like a breathless press release than something truly ground-breaking. More notes below:

> Synhelion was founded in 2016 as a spin-off from ETH Zurich, sparked by what the company founders describe as a crazy idea they had: what if they could reverse combustion and turn carbon dioxide and water back into fuel?

This is not a "crazy idea", but rather a straightforward description of the chemistry involved. We call one implementation of this process "photosynthesis", but there are others.

> The technology they’ve developed relies on four key components. Mirrors – known as heliostats – that track the sun to focus its energy on to a solar receiver. This in turn produces very high process heat at temperatures exceeding 1,500°C. This heat powers a thermochemical reactor that turns CO2, water and methane into syngas, which can be processed via Fischer-Tropsch into fuels.

Again, this is well-understood industrial process chemistry - absolutely a good thing, in my opinion, but not new and sexy by any stretch.

> And finally, a thermal store to release energy when the sun goes down to allow the solar-powered facility to operate around the clock.

This actually IS new and interesting in this application (or at least, it is to me) - a shame that this isn't fleshed out more in the article. I tried to see if there was more about this aspect of their process on the Synhelion website, but their pages were loading slowly and I lost patience. Sorry, team.

> The company says the design of its ultra-thin hexagonal mirrors are key to achieving such high process heats.

Any physicists out there who have a speculation about why the thinness of the mirrors makes a difference here? My understanding is that the maximum temperature that mirrors can get you is limited by the surface temperature of the sun, rather than the mirrors themselves, but I'm certainly no expert on this point.

> It uses an AI-based method involving drones to calibrate the mirrors 200 times faster compared to traditional techniques using cameras, Synhelion says. Precision is key to ensure the mirrors track the sun and efficiently reflect its light into a solar receiver at the top of a 20 m tall tower.

This bit smells like trying to shoehorn in an application of "AI" where it's not really needed - what's the actual improvement using "drones and AI" over just pre-calculating a tracking curve based on latitude + time of day/year? Or just putting down twice as many mirrors and not bothering to make them track?

> “... The inauguration of DAWN marks the beginning of the era of solar fuels – a turning point for sustainable transportation. Our founding dream of producing renewable fuels from solar energy is becoming a reality.”

This is hyperbole, as eg. Prometheus was doing this two years ago. Additionally, Synhelion will be hamstrung on growth as long as they depend on biomass methane as a feedstock, but they can solve that by buying methane from Terraform :)

I’m looking forward to times when this silly technology kills all plants because no CO2 remained in the air but people need fuel