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Joined: Tue Jul 22, 2014 9:45 am
Location: Loughborough, UK

Solar -> CCS?

Mon Jul 28, 2014 8:03 am

A number of forum members (in sunnier climes) want to charge their i3s from solar panels. So you'd need 7 Kw of solar power continuously for over 3 hours to charge the car. That's a huge acreage of solar panels. Is anybody considering using solar power to feed the DC rapid charging circuit via the CCS connector? That would eliminate the losses from converting solar DC to AC and back again.

Posts: 305
Joined: Wed Jul 09, 2014 4:08 pm

Re: Solar -> CCS?

Mon Jul 28, 2014 12:13 pm

A friend put 4 kW of solar panels on his house when he got a Tesla Roadster. Shortly before the Roadster was delivered, and before the panels were turned on, his boss installed a charging station at his parking space at work! He never did charge at home, and his electric bills are now down about 90% from previous years.

BTW, as much as I love the i3 (from test drives, as I expect mine to be delivered within 3 weeks), I must say that the Roadster is more fun to drive!!!!

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Joined: Mon Jul 28, 2014 12:01 pm
Location: Beltsville, Maryland

Re: Solar -> CCS?

Mon Jul 28, 2014 12:29 pm

Given some charging loses and inefficiencies you’d probably need over 10 kW of panels to provide the 7 kW level 2 charge, That would be about 1000 sq. ft. of panels or 2.3% of an acre. It would fit on many large residential roofs.

While it is an attractive concept to charge an EV directly from sunlight without any tie to the utility grid, it would be expensive and wasteful to do in practice. When the sun is shining and the car isn't there to accept the charge or its battery is full then the expensive panels are wasted. It much better, when possible, to connect to the grid like most solar power installations. Then all solar power produced that isn't used immediately is fed to the grid. And when you need power but sun isn't shining you take some power back from the grid.

You could probably put together a small stand alone system that would support the lowest level 1 charging of 120V 6A 700 Watt. That would only require 100 sq. ft of panels, might be semi-portable and cost you a few thousand dollars for something that would recharge your car in about a week in the sun. Not particularly practical or cost effective.

Now imagine what it would cost to put together a level 3 DC fast charger at 50 kW.

Near me there is a 400 kW solar microgrid with storage that has a couple level 2 chargers. I might have to drop by there sometime for a charge.

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