Power-to-gas energy storage could help displace use of fossil fuels

[IDemo]

The intermittent nature of renewable power generation has long been a potential barrier to a low-carbon future.

Electricity only generated when the wind blows or the sun shines isn't always needed at that exact time. As more intermittent power comes online, the grid has to turn down more energy. Between October 2011 and March 2013, 224GW hours of potential energy were turned down from UK wind farms alone (receiving £7.6m of the total £170m curtailment and balancing payments in 2013 – effectively being paid for energy that could have been generated, but isn't).

Surges of renewable energy are rejected in favour of the low and steady hum of nuclear, coal and gas. This problem can only be solved by effective energy storage. Batteries can only keep small amounts. Electric vehicles could potentially, en masse, add up to one big storage capacity, but it is unlikely any time soon. Pumped hydro is the current front-runner, using excess energy to pump water up a slope and release it back down again when needed, but it requires very specific topography (ie hills and space for large lakes).

There's another solution, which avoids all those issues – turning the excess electricity, through electrolysis of water, into renewable hydrogen gas.

http://www.theguardian.com/sustainable-business/renewable-energy-power-gas-storage-fossil-fuels

[intaglio]

1. There are several energy storage solutions

Cryogenic energy storage can be operated at near 70% efficiency in ideal situations, although those conditions require a low grade heat source. However it is scalable for home energy storage at lower efficiencies and has a surprisingly low capital cost

Vanadium redox flow batteries can operate at 65% - 75% but have low energy densities compared to more traditional batteries. The chemicals, space required and capital cost mean that it cannot be used at home.

Mechanical (gyroscopic) storage - the big problems are mass, friction and speed variation during discharge but these are largely cured by higher velocity wheels in vacuum on magnetic bearings. Industrial sized ones can give "round trip" efficiencies of 80% - 85%. Again scalable for home use but the capital expenditure is huge.

Home battery storage for people with solar and wind generators comes in 2 flavours: firstly using a plug-in electric/hybrid vehicle as a home back-up and secondly lead acid batteries purchased specially for the purpose. The vehicle solution has an obvious problem - going for a drive could leave your home powerless and is a pretty high capital cost. The second solution is a low capital outlay (even lower if second hand batteries are purchased). Personally I look on this solution as the elephant in the room because it decentralises the grid even further.

[Benton D Struckcheon]

2. Tesla and Solar City are already marketing lithium-ion battery packs.

They've been doing it for residential and commercial, and are just now getting to utility scale. Lithium-ion energy densities have been increasing. The solutions are actually already here, it's now a question of mass deployment to get the cost down.

[nationalize the fed]

4. batteries always need replacement

at least today's batteries. Until there's a major breakthrough that's the way it is.

You want tons and tons and tons of dead lithium batteries having to be lugged around to be recycled?

[Benton D Struckcheon]

5. They last a few years and all materials are recyclable. N/t

[hunter]

3. In arid places near the ocean it would be done like this:

Base load power would be used to desalinate brackish and sea water, and to recycle sewage. This fresh water would be kept in low elevation reservoirs.

Whenever there is a surplus of wind or solar power that fresh water would be pumped uphill and stored, where it could be used to generate power later, maintain natural river flows, and provide domestic water supplies.

Storing hydrogen gas isn't as efficient as pumped storage hydroelectric power.

In a perfect world with surplus energy we wouldn't be extracting hydrocarbons at all, we'd be grabbing carbon dioxide from the air and turning it back into coal or hydrocarbons we could put back into the ground, and recyclable plastic products.