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Are the batteries ready? Bringing clean energy storage up to speed

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Institute for Local Self-Reliance

In the long run, there’s no avoiding energy storage for a 100 per cent renewable energy society. The two major sources of renewable power are wind and sun, and they are either fickle or reliably not available at night.

The problem is that the simplest energy storage option for electricity is batteries, and this image from Wikipedia (hat tip to Robert Rapier) illustrates a significant technical barrier: our simplest option is also among the least energy dense material we have.

There are two likely paths to a 100 per cent renewable energy future in these circumstances: mass distribution of low-density, low-cost storage, or higher density storage.

In some respects, we’re already moving along the first path. Widespread availability of battery-powered iPads and laptops has led to great strides in greater energy density of batteries and lower cost. The following chart (used in our Democratizing the Electricity System report) illustrates the changes in the past 15 years.

Electrified transportation is the next iteration, using batteries that are orders of magnitude larger (eg. a Nissan Leaf battery with 23 kW-hour capacity has 300 times the storage capacity of a Macbook Pro laptop battery). These are 1st-generation commercial batteries, with enormous improvements in capacity and cost likely. Furthermore, with hundreds of millions of cars, the sheer storage capacity of the US vehicle fleet will be tremendous (over 4 billion kilowatt-hours) as electric vehicles become the drive train standard. And a recent study has shown that the storage capacity of 2.1 million vehicles can enable an additional 10 gigawatts of wind power on the grid (in the Northwest).

The Germans, ever the clean energy integration leaders, with over 15 per cent of their electricity sourced from wind and solar, have also looked at electricity to hydrogen storage (a look at the above chart suggests the energy density of hydrogen has some advantages).  While not as efficient as batteries (two-thirds of power is lost, compared to 10-20 per cent round trip for batteries), the resulting hydrogen can be used in natural gas power plants to provide backup power or piped into the natural gas network for building heat.  It’s not only flexible but it also could be useful because wind power in particular can peak during periods of low electricity use (nighttime).

The good (or bad, depending on your perspective) news for the US is that renewable energy is such a small fraction of total electricity generation that energy storage isn’t yet necessary in any significant quantity. Existing power plants have sufficient spare capacity to fill the gaps left by variable renewables. While this state of affairs doesn’t endear the US power industry to environmentalists, it does mean there is time to see storage technology improve.

I’m optimistic.

This article was originally published on the Institute for Local Self-Reliance – www.ilsr.org. Reproduced with permission.

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  • Paul

    I don’t see how density is the primary concern for stationary grid energy storage? Isn’t cost the biggest barrier?

    Storage is not only applicable for use with renewables, watch this interview for more details: http://youtu.be/vX0G9F42puY

  • Ken Fabian

    Developing storage has been lagging – but there are interesting solutions beginning to emerge as the focus begins shifting from better wind turbines and lower cost solar cells.

    With (claimed) costs lower than pumped hydro this use of pumped heat looks worth keeping an eye on – http://www.isentropic.co.uk/news/46/66/UK-Government-backed-body-invests-in-Isentropic-s-revolutionary-low-cost-energy-storage-system

    The combination of liquid electrolytes and capacitors into flow capacitors that don’t have the capacity limits of conventional ones sounds worthy of follow up – http://www.nanowerk.com/news/newsid=25663.php

    But I do have to say I’m doubtful that the world’s Lithium supply can handle either widespread use for electric vehicles or stationary storage for renewables – there just isn’t that much of it. I think that thermal remains my favorite for large scale energy storage especially if better means of converting lower grade heat to and from electricity emerges – stirling engines just haven’t shown themselves to be cost effective so far. Something ‘out there’ like nantenna’s converting radiant heat direct to electricity maybe?