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Tom Lombardo posted on March 21, 2013 |
This Solar Tree can charge an EV and provide shade.

A few days ago I posted an article about a wireless charging system for electric vehicles. I promised that I'd discuss the solar power angle in my next article. Here it is!

On a hot sunny day I try to park my car at the edge of the parking lot where there might be a shade tree. These are pretty scarce, since parking lots aren't a good place to grow trees. Envision Solar has the remedy for that: an artificial shade tree that doubles as a source of energy. Meet the Solar Tree...

Image: Envision Solar

Each Solar Tree shades six parking spaces while generating up to 14.4 kW of power. The power can be used on site or, when coupled with a charging station, a Solar Tree can charge up to six electric cars. You can leave work and get into your cool, fully-charged electric car. Win-win!

Image: Envision Solar

Let’s do a little math on that. A Chevy Volt’s battery capacity is about 16 kWh. A Solar Tree produces 14.4 kW at peak sun, which technically occurs only at solar noon. During non-peak hours, the panels deliver less electricity. Peak Sun Hours (PSH) is a unit that’s used to calculate the average sunlight at a given location over a full day. For example, Chicago IL has a PSH rating of about 3.5. That means that if you averaged out all the sunlight it receives over a full day, it would be equivalent to 3.5 hours of peak sunlight.

The amount of energy that a PV panel generates in a day = Peak Power x PSH.

A Solar Tree in Chicago would generate about 50.4 kWh (14.4kW x 3.5 PSH) per day. That would charge 6 Chevy Volts to full-capacity, assuming they were halfway depleted at the start of the day.

Imagine a Solar Tree at every bus stop/charging station. It provides shelter for the riders while they wait and it charges an underground battery which, in turn, tops off the bus battery when it stops for passengers. Putting the big battery underground instead of in the bus means that the bus doesn’t have to lug around the added weight. You’d need an inverter since inductive coupling only works with AC, but it’s certainly possible. Now you have a truly emission-free vehicle!

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