Recycled Coal Mines – Storage Space for Renewable Energy? | Tomorrow Today - The Science Magazine | DW | 23.03.2015
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Recycled Coal Mines – Storage Space for Renewable Energy?

Surplus power generated by renewable energy sources needs to be stored because the wind isn't always blowing and the sun doesn't always shine. Jochen Bard, a physicist from the Fraunhofer Institute for Wind Energy and Wind Energy System Technology (IWES) in Kassel tells about using decommissioned coal mines to set up pump storage power plants, an approach that could be a hit in other countries.

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Pump storage hydroelectric plants are seeing reinvigorated industrial landscapes, old mines are being reused, surely there's a downside to this technology?

Jochen Bard, Fraunhofer Institute

It is an excellent idea. We need more energy storage in the future and pump storage systems that a high efficiency, so it is a great idea to try and reuse existing infrastructure. However, we will need much more energy storage in the future, maybe a thousand times more than what is available today in pump storage, but this is a step in the right direction.

Well in a facility like this, how much energy exactly is it producing? Is it enough for a small town, or a small city?

A pump storage power plant can provide power for a city the scale of Berlin for several hours, so it's quite a lot of energy that can be stored.

Well, that's quite impressive. This is the kind of solution that Germany needs, if it's going to make this massive transition to renewables, the Energiewende, that they've promised to carry out over the coming decades. On Facebook, our viewer Sato Adriono says that supplying energy from renewables is actually simply a matter of will on the part of governments. Do you agree with that?

We certainly need a very consistent energy policy over a number of decades in order to achieve what our targets are, but it's also depending on the contribution of all people in the country to save energy, use new technologies, such as heat pumps, electric vehicles and so on.

Among the different sustainable sources, you know you have hydroelectric and solar power, wind power, just to name a few. Which one do you think will win out in the long run?

The energy solution in the future will not be one silver bullet. It will not be only one supply system. We will have a mix of energy supplies, from solar and wind which are the two most important ones, but also bioenergy because it can be controlled. And there are other parts of the world that have other opportunities - like geothermal and ocean energy or hydropower.

When you talk about bioenergy, you're talking about power to gas, then?

Yes, power to gas or biogas from fermentation processes are the options that we are currently looking at.

Power storage is for when the sun isn't shining and the wind isn't blowing. Storing the energy is the major problem. Hydroelectric plants, like the one in the report, they're one solution. What other kinds of solutions are out there for storing large amounts of energy on the scale we would need?

Batteries. Electrochemical batteries like lead acid batteries or lithium ion batteries, to name a new technology. They are also very important for electric vehicles or stationary systems in houses. They will not be very big, so we will have to use very many of them. Other forms are chemical storage systems by using hydrogen or methane and that can be done by using the existing gas network that we already have.

Well, supply is just one aspect of this equation. The other is going to be consumer behavior.

What can individuals do to actually improve the energy supply balance?

Everybody can reduce their electricity consumption by simply buying efficient appliances. Wen you buy a new fridge or buy a new tv, pay attention to the energy consumption. We have reduced our consumption at home maybe by two-thirds, by now, step-by-step.

Two-thirds? That's a lot. Thank you very much for joining us on Tomorrow Today.

(Interview: Derrick Williams)