We reported Thursday that St. Paul has installed two solar-powered electric car charging stations in Como Park, which prompted reader Ed Lehr to ask:
Is the car charging station equipped with solar panels which are charging a battery pack to charge the car battery packs, or does it have a token grid-tied solar pv array to feed the grid?
They didn't cover that kind of detail in my mandatory science class (astronomy) at St. Thomas a few years back, so I asked Anne Hunt, environmental policy director for Mayor Chris Coleman: What's up?
Her response to Mr. Lehr and me:
The PV systems at Como and McMurray are rated at 2 kilowatts, 8 modules at 250 watts each. The arrays are tied to the utility grid through the building electrical system.
They are sized to offset of the power that is expected to be consumed by the cars using charging stations.
A battery bank to store the power would have added a substantial cost to the project, and would have required substantial maintenance, and replacement of the batteries every 5 - 7 years.
The solar array was designed and constructed to require virtually no maintenance.
There will be times that the power from the solar panels would not have been used by cars charging so it is tied to the building. And there will times when people want to charge their cars (at night or cloudy days) so charging stations will pull from the grid.
Both solar sites have production meters recording the amount of power that is being generated from the solar array. And the car charging stations will record the amount of time that they are used.
The charging stations are new technology but the solar isn't. We'll learn a lot.
More information on the city's charging stations is available online.
Two Cities blog, which covers Minneapolis and St. Paul City Halls, is made possible in part by grants from The Saint Paul Foundation and the Carolyn Foundation.