Running hot and cold

Phil Carson | Jan 29, 2010


The news this past Wednesday that the Southern California Public Power Authority (SCPPA) will proceed with a pilot-scale project with Ice Energy on utility-scale energy storage delivered an opportunity for a brief review of that space. As my colleague, Kate Rowland, examines the news in her column today, I'll attempt the context. 

Most efforts appear to be in the pilot stage right now. About 16 projects nationwide have been awarded demonstration grants totaling $185 million under the American Recovery and Reinvestment Act. We'll mention a few such projects in a moment, but first let's look at the technology options and how they tie-in to the smart grid.

I had the benefit yesterday of speaking with Michael Winkler, who works as an energy specialist for the Redwood Coast Energy Authority (RCEA). Winkler walked me through the technology options for energy storage and their ties to the smart grid.

The RCEA is a nonprofit, joint powers authority representing seven towns in Humboldt County, Calif., that promotes sustainable energy practices. I thought its humble (no pun intended) size made a useful contrast with the sprawling SCPPA initiative. And I'm looking forward to learning more about the Electricity Storage Association (ESA), which has evolved from exploring storage as it relates to short-term reliability issues to longer-term storage options examined here.

While working for the Schatz Energy Research Center in his hometown of Arcata, Winkler determined that Humboldt County could be not only self-sustaining but a net exporter of electricity, based on its abundance of wind, waves and sun.

"To make that work, however, required that we develop energy storage techniques tied to a smart grid," Winkler told me. "That's because our renewable resources generate power at the 'wrong time.' And exporting electricity is constrained by the limits of our current transmission system."

With a smart grid in place in the future, the grid operator will see a surplus of power generation -- perhaps from renewables -- or a dip in demand and balance the system by shunting excess power to a storage medium for later use. The stored energy can be used later to shave peak load or serve demand in off-peak hours. Permanent load shifting increases the reliability of transmission lines and optimizes use of generating capacity. For utility-scale, renewable energy integration, storage is "the holy grail," Winkler said.

In Winkler's view, storage technologies fall into two categories: thermal or electrical. Thermal can imply the use of heat or cold and those uses might vary according to climate. Ocean-cooled Humboldt County needs heat storage (probably in the form of geothermal exchanges), while end-users in Southern California need cold storage, thus the SCPPA pilot with Ice Energy. Electrical storage goes to batteries or plug-in hybrid electric vehicles.

Battery innovation is alive and well -- see GE's investment in A123 Systems, for example -- but Winkler's data showed that thermal storage currently is an order of magnitude cheaper, with an unlimited lifecycle (water versus batteries' exhaustible chemical storage media) and nearly as efficient as batteries. (Battery R&D folks and vendors chime in here.) Thus, for now, Winkler is focusing his efforts on thermal storage.

Two other thermal storage technologies we haven't mentioned: centralized, compressed air and pumped hydro storage. The latter has been in use, in one form or another, for more than a century. Compressed air energy storage (CAES), in contrast, implies pumping air into underground chambers (abandoned natural gas chambers, e.g.), then releasing it to drive electric generators.

You'll see from the U.S. Department of Energy's (DOE) demonstration grant awards that utilities large and small are investigating these promising technologies with a variety of partners. Southern California Edison is looking into solid state lithium-ion batteries. Pacific Gas and Electric is exploring CAES.

Winkler relied on DOE's Energy Information Agency data that showed average residential energy expenditures is 66 percent thermal dependent. In other words, two-thirds of residential energy use could be addressed by the more efficient, environmentally benign thermal storage options. He inadvertently touched on yesterday's lively discussion in this space, however, when he projected that the large commercial building sector, with keen interest in financial incentives, would be first to realize benefits from energy storage technology.

Phil Carson
Intelligent Utility Daily


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One of distributed thermal storage's biggest advantages is that it doesn't require the expensive and contentious permitting a central station pumped storage or CAES plant would.  No new transmission would be needed.  Best of all, it would be capable of operating much more flexibly than pumped storage or CAES.

I'd like to think policymakers will have the good sense to craft rules that don't tilt the playing field in favor of any particular technology.  Even the more promising concepts will only get better if their inventors are under constant pressure to improve. 

Electrical and thermal storage bills introduced

Mike Winkler just mentioned that his congressman, Rep. Mike Thompson (D-CA), is sponsoring two bills to provide tax credits for installing end-use energy storage.

One bill covers electrical storage (H.R. 4210) ; the other bill covers thermal storage (H.R. 3918). The bills focus primarily on homeowners. When H.R. 3918 was introduced, Ice Energy and a competitor, CALMAC, endorsed it.