The initial use of solar on the Prius was to power a ventilation fan while the car was parked, and the current version seems to specifically be designed to provide power to the air conditioner while driving. But, I also can't imagine the difference between cooling down the cabin is much different from parking in the sun or in the shade - you'd be running it continually to achieve "room temperature" during the entire drive either way.
I think they only switched to Epik/Voxility for a few hours after being kicked off Cloudflare, but I'm not familiar with where they would have been hosted or what services they used 3-4 years ago.
The garden is overseen by professionals, so it has likely had soil testing done, especially since they are growing produce.
Manhattan is mostly an island of bedrock, and there is no manufacturing or industrial areas in Lower Manhattan that would contaminate the soil. The only concern would be protecting the garden from water running off the streets bordering the park, but those all have drainage and curbs installed.
Kevin was interviewed by his former TechTV co-worker Leo Laporte on Leo's podcast Triangulation, if you're interested in Kevin's story: http://twit.tv/show/triangulation/162
Their intention is for the pool to act as a filter to clean NYC's waterways[1]. Research into effective water filters could be worthwhile, but the floating pool seems to overshadow that aspect.
Throwing in a mention for PodKicker[1], since you mentioned searching/discovery. The UI needs a lot of work, but it is nice to have the search engine built-in (they claim an index of 250,000), instead of trying to grab RSS links from a podcast's homepage. The search itself is even available as a separate app[2].