The Future Of Energy Part 4: Energy Storage

In part 1 of this series, I made a case for reducing our dependance on fossil fuels as much, and as soon, as possible. In the rest of this series I'll be looking at ways this might be done.

So far I've looked at wind (part 2) and solar (part 3), and I've said that these can only ever make up 20% of our total electric supply. The reason being that they are intermittent sources (i.e. not round the clock) and you can't run a modern society on an electric supply that shuts down over-night!

So, is it possible to get round this problem? Well, it looks like the answer is (or will be) "Yes" if something called Grid Energy Storage lives up to it's promise.

The idea works like this: National power grids are set-up to meet the maximum possible demand the population can place on it. If they weren't, then there would be 'black-outs' all the time.

The trouble with this approach is that, for the majority of the time, there are power-stations sitting around idle, waiting for peak demand. Meanwhile, there will be others, the ones which can't be switched on and off at a moments notice (like coal, nuclear, solar and wind), that are sometimes generating electric with nowhere for it to go (e.g. when everyone's asleep). Crazy.

Imagine if you could store that excess electric, and release it at peak demand: You wouldn't need so many power stations doing nothing. Potentially huge cost savings.

Another benefit of energy storage would be for 'smoothing out' the supply dips in intermittent sources like wind and solar. This would effectively give you a constant supply from these sources, enabling them to make up much more than the 20% of the total electric supply I mentioned earlier.

Types of Energy Storage

There are actually many different types (See here) so I'm just going to pick out a few to show the potential:

• Batteries: It's difficult to think of batteries, even big ones, holding enough energy to be useful to a national grid, but that's exactly what they are being used for right now. The types of batteries range from relatives of the familiar lithium-ion (e.g. found in laptops) and lead acid (in cars) to the less well known sodium based, and so-called flow batteries. The most popular variety at the moment are sodium sulphur batteries but many others show promise, especially flow batteries. 

• Flywheels: These are already in use for grid power in a few cases. Flywheels involve accelerating a rotor to a very high speed to store the excess energy, then decelerating them to recover the energy.

• Molten Salt: You might remember I mentioned something called concentrated solar power (csp) in part 2 of this thread? With csp, an array of mirrors focus sunlight on a central tower creating heat. This heat is used to boil water and drive turbines. Any excess energy can be stored in reservoirs of molten salt for a number of hours until it's needed. This could have huge potential for sunnier regions like Australia, the Mediterranean, and California. It's a proven technology and it's likely to go into full commercial use very soon.

• Pumped Hydro: This is a commonly used storage technique which involves using spare energy to pump water uphill to a raised reservoir. To release the energy, you just let the water flow back down and drive a turbine. The obvious problem with this is that reservoirs aren't always possible e.g. Not enough room, or the land is too flat.

Conclusions
For me, energy storage will play a key role in our efforts to reduce carbon emissions. It will allow electric generation to be more efficient by holding onto any excess until it's needed; permit solar and wind power to be bigger players in generating electric; and, for transport, smaller, cheaper, lighter batteries will revolutionise electric cars.

And that's just the tip of the iceberg.

But energy storage is still in it's infancy and it may be a decade or more away from making a real impact. So what do we do in the meantime? Well, for a start, keep adding to the wind turbines and solar power stations as fast as possible. It's going to take a while for most countries to reach their 20% thresholds anyway. By then, energy storage may be in the position to take off.

My concern though is: What happens if, for some reason, energy storage doesn't take off?

I look at a possible answer in the next part of this series.

More on energy storage.