The Big Promise of Solar Parking Lots


[Image source: Kyocera Solar Grove™ via Envision Solar]

While researching some other project, I came across this recent Autoblog Green post where they talk about the installation of a solar parking lot with capabilities to charge electric vehicles, the first one of its kind on the Southeast according to Outpost Solar, the company responsible for the installation.

Solar car ports are of course nothing new (this one in Santa Monica has been there since 2005), but reading the upbeat quotes and press release made me think again about The Promise and The Delivery of solar as it relates to EVs.

Let's start with The Delivery:

One of the recurrent questions I got when presenting itMoves was: can you charge the vehicles with the solar panels? I explained many times that the solar panels were only there to keep the AC (or heating) running, in itself not a small feat since HVAC systems are real power hogs. By keeping the shared MEs at the perfect temperature, we could provide a nice touch to the costumer, and reduce the drain on the main battery pack (no need to turn the A/C to 11 when leaving the spot). Although not too many people complained, it always felt like everyone expected one equation to be true:

1 solar panel = 1 car.

To be honest, I felt the same way when I started itMoves, but unfortunately the mathematics do not work that way:

A great rule of thumb to calculate solar energy is that the surface of the earth receives every hour an average of 1kW per square meter (10.8 square foot). Solar panels on the other hand are quite inefficient, with the best commercially available units only able to harvest around 18% of that energy. Taking Outpost Solar installation as an example, the 96 panel array (measuring 144 square meters) will deliver a maximum of 26 kW (144 x 0.18 = 25.9), consistent with their claimed 2.25 kW per parking spot. Adding to the inefficiency chain, chargers only transfer around 85% of the energy, therefore cutting the available energy at the plug to around 22kW.

Since battery packs range from 16 kW (Volt) to 30 kW (Mini-e), with the Leaf in between the two at 24kW, this particular installation can charge one or two cars per hour. In other words, if all the twelve parking spots are filled with EVs, they can all expect to be filled up after an eight hours work day.

This is not bad, although it is far from the ideal one solar parking spot equals one car, specially when we consider it takes between six and eight hours to charge them all. The economics are not particularly favorable either, since at current rates, it will take around sixteen years for the daily savings to offset the quoted $180,000 price tag. In practice, the market is reduced to willing employers who want to offer a different kind of benefit, while looking good in the process.

Which brings me to The Promise:

Visible solar (whether in parking lots or in products) promises The Future. Yes, it is still too expensive, and yes it is still too big and impractical, but it will only get better and cheaper. Like the flawed yet exciting EVs of today, solar panels indicate the beginning of a promising journey, after many false starts. We will get there, that is The Promise.
[[posterous-content:giJkzoEwCGnpugdlgwra]]When designing the 4.ME parking modules, it was great to think about the kWh produced, but quite frankly, the main motivation to add the solar array was visual: it shouted the message that decentralized electric power for transportation is here, and it is as clean as it can be. Unlike omnipresent oil, the majority of solar is now hidden, either out in the desert or up in commercial roofs, and that represents a lost opportunity to engage the public and make them believe in real energy independence.

Of course, economic fundamentals will in the long run make or break The Promise, but we have China's growth to help create the ideal conditions, both by pushing up demand (and price) of oil, and by dramatically lowering the cost of clean technology. Let's just hope that, after destroying all foreign competitors, they do not turn into the OPEC of clean energy.