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Clean Renewables and Clean Energy Storage – A Perfect Combination of Domestic Resources

There are interesting synergies between renewable energy and energy storage that have profound implications for the Smart Grid and our energy and economic security.  Wind and solar are readily available domestic sources of clean renewable electricity and share a common characteristic of intermittency.  Wind tends to pick up at night, and we all know when the sun shines.  There are also weather-related influences that make it difficult for generation planners to have 100% confidence in these resources, unlike traditional fossil-fueled sources of electricity.  Given the risk-averse nature of utilities in planning their power purchases, would they favor the purchase of renewable power from producers that could “firm” or commit that power with reserves of stored energy over those producers that couldn’t provide that additional assurance?  Could renewable power producers with energy storage capabilities participate in ancillary services and increase revenue possibilities for their business?  For instance, wholesale frequency regulation – the ability to inject power into the grid to maintain the desired frequency on the grid – could be supplied by clean energy storage instead of running fossil fuel-based generation facilities in a standby mode – a costly and emissions-producing practice.

What has prevented energy storage from playing a bigger role in the Smart Grid and being coupled with renewable sources of electricity?  There are two reasons – technology and price.  Energy storage technologies are experiencing a transformational boom, in part due to the Department of Energy’s Advanced Research Projects Agency – Energy (ARPA-E) focus on innovative breakthroughs for electric vehicle (EV) batteries.  Grid-scale energy storage solutions are also benefitting from new interest and investment, and are poised to challenge traditional energy storage solutions.  For example, traditional pumped hydro harnesses the energy of water running downhill to spin turbines and generate electricity, and then uses cheap, off-peak electricity to pump that water back to the top of the hill for reuse.  But pumped hydro requires very select conditions – a ready supply of water, a steep hill, and the willingness to invest a billion dollars or so into a generation plant and transmission facilities. 

And then there is price.  Many energy storage technologies simply couldn’t compete with fossil fuels – although the negative externalities of CO2 and human health were not factored into these calculations to deliver true costs.  But now there are new energy storage technologies that can cost-competitively store electricity.  One interesting technology takes the common zinc-air battery, which is today used as a disposable battery for hearing aids, and makes it a high energy density and rechargeable energy storage option.   What is most intriguing about zinc-air technology is what it is not – it is non-toxic and non-flammable, two attributes missing in some energy storage technology alternatives.  Another positive attribute is the price point – it can achieve “grid parity” with natural gas. 

One company that is focused on zinc-air is Eos Energy Storage, an east coast startup.  Eos intends to sell their grid-scale product at $160 per kWh, which is one fifth the cost of a lithium ion battery system, according to Steve Hellman, president of the company.  This price means that their grid-scale batteries would compete with gas-fired turbines to firm renewable power and ancillary services like frequency regulation.   Since zinc-air technology is environmentally benign, it could easily be situated for distributed energy storage purposes in residential neighborhoods without complications of zoning for toxic or flammable substances.  Distributed energy storage avoids the need to build expensive transmission facilities.  This technology would also be welcome in substations because it would not introduce new safety risk factors for workers.  In addition, zinc is readily available in the USA.   Given our current energy and economic insecurities caused by a reliance on imported fossil fuels, we should look to domestic clean sources of energy and materials and leverage natural synergies between renewables and energy storage to speed their integrations into the Smart Grid.

Photo by EosEnergy.

Christine Hertzog's picture

Thank Christine for the Post!

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Geoffrey Styles's picture
Geoffrey Styles on August 2, 2011

Christine,

Storage certainly looks like a crucial ingredient for intermittent renewables, but as you note it’s not cheap.  Could you quantify the benefit of firming renewable capacity with storage, and is the uplift sufficient to justify dedicated storage, particularly for wind, which generates most of its output off-peak?  And how does that compare with the cost/benefit of time-shifting millions of megawatt-hours from renewables to compete with baseload technologies?  Or is the whole model of dedicated, rather than grid-serving storage suspect? 

Rick Engebretson's picture
Rick Engebretson on August 2, 2011

Storing electrical potential energy and storing plain old potential energy create different possibilities.

Storing water at some height then allowing that mass and gravity to work for you later can be done with any mass, and most any hydraulics. Hydraulic pressure might even be obtained by something as simple as daytime heating and nighttime cooling, without wind or solar electricity. Fancy fluid phase changes might even be regarded as a form of heat pump.

But if electrical storage is a must, without the problem of energy density for mobile batteries, electrolytic capacitors might work. I salvaged a large capacitor from Otto Schmitt’s lab that he said was used to kill “big Norwegian rats.” The rat stood on a metal plate and touched the wired bait and they heard the zap and found the rat on the other side of the room. Being something of a provocateur, I got the hint.

I suspect batteries will always be expensive. Highly reactive chemistry in a sophisticated container is something to respect.

Geoffrey Styles's picture
Geoffrey Styles on August 2, 2011

Ed,

Compressed-air energy storage (CAES) is interesting, though it’s hard to envision it being very useful in dedicated storage, especially for buffering of intermittent renewables.  As I understand it, it’s almost more of an efficiency technology, functioning as a supercharger for a gas-fired turbine.  No natural gas, no CAES.

Nathan Wilson's picture
Nathan Wilson on August 2, 2011

I think “grid parity” with natural gas is out of reach for this battery system, at least for wholesale producers.

The $160/kWh figure sited adds up to $1.28/W for an 8 hour system.

This report from Sandia labs  http://prod.sandia.gov/techlib/access-control.cgi/2003/032783.pdf looked at various storage systems. For a lead-acid battery system, it shows $150/kWh, but this means selling stored energy for whopping $0.40/kWh, once interest etc is added in (assuming power is purchased for $0.05/kWh).

That’s more than double the cost of pumped hydro (for large systems), and no better than the cost of the hydrogen fuel cell system (for small systems).

John Englert's picture
John Englert on August 3, 2011

Instead of looking for complex, high tech solutions to the difficulties of diffuse intermittent sources of energy, perhaps we should ask ourselves if maybe these sources just aren’t suitable for our electricity needs. There are some good reasons why people moved from windmills and water wheels to heat engines to perform work.  

Rusty Speidel's picture
Rusty Speidel on August 10, 2011

In the end, it comes down to cost per KWh for the life of the installation. Batteries today have life spans that are not particularly compelling for a large-scale project becuase they need to be replaced 4 or 5 times over the life of that project. At Encell, we see things differently. We are focused on developing a battery that will deliver full charge and discharge for 40-50K cycles, using chemistries that are safe, clean, long-lasting, and impervious to abuse. Where we are innovating is in the design of the actual battery, so that traditional mixtures can be ressurrected and causes of inefficiencies and power loss can be greatly reduced.

Our designs come in a prices consistent with current lead acid solutions, generate power per Kg suitable for alternative storage needs, and then win big by lasting far longer than any lead acid or lithium solution can ever hope to. Once our batteries are installed, that’s it. There is no second, third or fourth capex investment every 5 years.

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