Cleantech Market Intelligence
For Microgrids, It’s Not All About Size
The University of Texas (UT) at Austin claims to have the largest microgrid in the world, with a peak load of 62 MW of capacity, serving 150 buildings. The combined heat and power (CHP) plant that serves as the anchor is rated at 135 MW.
Leave it to Texas to make such a claim. It’s not really accurate, but more importantly, it doesn’t really matter. Bigger is not necessarily better when it comes to microgrids.
On the one hand, economies of scale tend to reduce cost. But microgrids turn that assumption on its head, since onsite distributed energy resources (DER) reduce the line losses associated with the centralized power plant model. I tend to agree with Steve Pullins of Green Energy Corporation, who says that the sweet spot for microgrids that incorporate new state-of-the-art technologies such as solar PV, lithium ion batteries, and CHP is between 2 MW and 40 MW.
About every 6 months or so, I get an email from Craig Harrison, developer of the Niobrara Data Center Energy Park, asking me, “Am I still the largest microgrid in the world?” The Niobrara proposal, which has increased in size from 200 MW to 600 MW over time (with both a grid-tied and an off-grid configuration now part of the single project), is still in the conceptual phase (you can see elegant renderings of the project provided by CH2M Hill). In this case, a unique confluence of natural gas supplies and regulatory quirks (which in essence render the project as its own utility) conspire to set the stage for what will probably be (and remain) the world’s largest microgrid. It’s only a matter of time.
Navigant Research’s Microgrid Deployment Tracker 2Q14 shows that the largest operating microgrid, if measured by peak demand (and not generation capacity), could be Denmark’s Island of Bornholm, which is interconnected to the Nordic Power Pool. With peak demand of around 67 MW, the advanced pilot project incorporates plug-in electric vehicles (PEVs) and residential heat pumps, along with wind and CHP.
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The microgrid at UT Austin is impressive, given that its origins date back to 1929 and it can provide 100% of the campus’ energy needs. But it’s really an old school microgrid since it relies upon one source of electricity and thermal energy. Robbins Air Force base in Georgia claims to have 163 MW of capacity, but it’s powered by large diesel generators, which are less desirable than CHP. Much more interesting are microgrids that draw upon multiple distributed generation sources, incorporate advanced energy storage, and can sell energy services back to the utility. The UT microgrid does none of these things.
In my view, a large microgrid is a contradiction in terms. It’s much better to create multiple microgrids and then operate them at an enterprise level, creating redundancy via diversity of resources and scale, perhaps even mixing in AC and DC subsystems. To me, a microgrid such as the Santa Rita Jail, which is only 3.6 MW in size but incorporates solar, wind, fuel cells, battery storage, and a host of state-of-the-art energy efficiency measures, is more interesting than the one in Austin. When it comes to distributed energy, diversity trumps scale.