More on that metaphor about the electric grid as a bathtub

Science Cafe Concord on Tuesday discussed the power grid, and how its being forced to change in the face of renewable energy, distributed energy, microgrids, storage and other technologies, all fueled by our growing worries about climate change. It was a very good two-hour discussion and if you missed it (for shame!!!), the video will be posted online by Concord TV here after editing is done in a week or so.

FYI, two other useful sources of information were mentioned: Panelist Mike Mooiman’s terrific (if sporadic) energy blog, Energy in New Hampshire, and the four-part podcast series on Hydro-Quebec, the electric powerhouse to our north, being put out by Outside/In, the NHPR podcast.

One subject that came up during the session is a metaphor for the grid I used in my Monitor column previewing the talk – that the grid is like a huge bathtub:

In other words, pretty much any New England producer of electricity connected to the grid, whether it’s Seabrook Station or your neighbor’s rooftop solar panels that he insists on talking about every single time you see him, pours electrons into one gigantic bathtub. Any user of electricity – whether it’s me using it to light up the computer screen I’m staring at as I write this or your town’s power-hungry sewage treatment plant – pulls its electrons from that same pool. That’s why we mostly pay the same wholesale price. (Our retail price is affected by state- and company-specific actions like taxes and transmission costs.)

However, last night’s panelists had some issues with the metaphor – specifically, that it implies you can store electricity like you can store water in a bathtub. The thing that makes electricity different from any other major energy source, of course, is that you can’t store to (at least,  not to any extent with today’s technologies). When millions of cars hit the road on Thanksgiving, the nation’s oil producers don’t have to instantly ramp up the amount of oil they pump, but when millions of air conditioners get turned on, the region’s power plants do have to instantly ramp up the  amount of electricity they generate. That’s why operating the electric grid is more complicated than operating, say, the oil-pipeline network.

So here’s an adjusted metaphor: The New England power grid is like a very shallow bathtub with a huge drain that can’t be closed. Each power plant is somebody who is dumping buckets of water into the tub and each consumer is somebody siphoning out water – the secret is to have producers keep enough water in the tub despite the drain so that we can all siphon at whatever rate we want, without throwing in so much water that it spills over the edge (gets wasted). And do it 24/7/365, as the amount of water being siphoned fluctuates wildly from week to week and now, as solar and wind get integrated, from hour to hour.