# tharwan.de

## Power to Gas in Africa

You may know this famous image illustrating that we would only need a "tiny" fraction of the desert in Africa to be fitted with solar thermal power plants to meet the electricity demand of the world (diploma thesis). Problem is how to get the energy from there to the world. If only there would be a high energy density storage medium that is easy utilize and transport.

Well, you see there is. Gas. Methane gas for example. While some try to get methane gas from the bottom of the ocean, there is technology to produce it from water. In essence you first split water in hydrogen and oxygen and then combine the hydrogen with CO2 to get methane. More or less the only other thing you need to do that, is electricity, which is why this technique is called power to gas.

The problem with power to gas is, that it has a very bad energy efficiency when you compare what you put in to what you get out. For high compression (200 bar), which you need in order for easy transport, you only get about 49% efficiency. In other words less then half of the electricity put in to the process would not end up in the produced gas. To put that in perspective a coal plant reaches about 33%, a gas plant about 60% and a diesel engine up to 50% (1,2). That in turn means that for the whole process of harvesting energy in Africa and using it for transportation and electricity we might and up with only 30% efficiency. Terrible isn‘t it?

No it isn‘t. Because the solar energy which radiates on Africa at the moment is not used at all. But we should compare it to other measures of energy production, and efficency wise they are probably ahead. But keep in mind that once installed you would get solar energy allmost for free with no environmental demage done while harvesting it. No nuclear waste, no added CO2 – you only have the investment cost and the maintainance costs of the plants.

Ok, back to the idea. Imagine we would build a lot of solar-thermal power plants in Africa and produce methane gas with them. We could provide the world with energy and the world would not even have to change! Well it would shake up the political landscape. Maybe. A little bit. We can use the gas for heating, for mobility and for producing electricity. All CO2 neutral with an allmost infinite supply for the future. And all the technology to do it allready exists.

The worlds energy demand should be about 20,000 TWh/y. To produce that in methane gas we would need about three times of that in electricity, assuming that allmost all is needed as electricity (which it isn‘t but it is the worst case). That makes 60,000 TWh/y. Assuming the same things as in the image above that would mean a square with an edge length of 500km. Or four times the size of the biggest square in the image.

So what would it cost? Let‘s do a very rough estimation here: The Ivanpah Solar Power Facility is the biggest solar thermal power plant today. It it cost $2.2 billion and produces about 1 TWh/y. This would mean the total cost for building the power plants would be about$132 trillion. Let‘s work with that, even though the true cost of building 60,000 power plants would for sure be different because of scaling effects and infrastructure that would be needed besides the plants.

How much are \$132 trillion? That is about 2 times the global GDP. A lot. But if you consider that this would solve the energy problem of the world – it might be cheap. In a rough estimate the US energy consumption amounts to allmost 1 trillion dollar per year alone. Solving the worlds energy problem with the all the worlds money in 2 years. Seams worth it.

Would‘t this be Desertec all over again? Somehow. The biggest problems Desertec had were political. You can not simply force Africa to be a stable part of your electricity grid. The problem with power grids is that they are much more unstable then they look like, so extending them geographically and making their stability dependent on a far away region is not a good idea.

The difference with gas would be that it is easy to integrate, as we would not need new powerlines. And while we would still be dependent on Africa to sell us gas (as we are now from Russia for gas and Saudi Arabia for oil) we can much more easily store gas for emergencies (as we do now). If we would couple our grid instead the shutdown would be immediate. Back to the bright side…

Isn‘t that amazing: we could meet the worlds energy demand with easy to utilize gas. For the rest of the lifetime of the sun. By only using a fraction of the land available in Africa.

The depressing thing is what we do instead…

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