A couple of other wikipedia entries worth looking at are compressed air powered cars. Tho they have a lower efficiency than internal combustion cars and its true that if the compressor to make the compressed air is run off of a coal fired power station then sure its not green but they can be run from solar and air is abundant and relatively easy to store compressed so there is no reason why a lot of people could not get tanks of compressed air slowly filling from solar even in low light countries. The engine is zero pollution, in fact its usually negatively polluting cos it filters the air going in and spits out very cold and cleaner air out the back.

Another list worth having a look at is energy densities and its quite a shocker so see where the carbon and non carbon based energy storage mediums fit in on the scale.

http://en.wikipedia.org/wiki/Air_car
http://en.wikipedia.org/wiki/Energy_density

Algae is a superb storage of nitrogen and makes for good fertilizer and can be burnt. The main issues with that is growing it. It does great out in the sea but collecting it would then require a lot of energy. Maybe people will find a way tho. In a sense, algae is not so different from growing trees, chopping into firewood and burning them again. Id say thats better than oil tho much less convenient. Ultimately, both algae and trees are solar energy storage devices. I just wonder whether we can do better than that.