Well, my favorite renewable power generation type is probably power tower solar thermal because I'm not optimistic about battery storage of photovoltaic being economical, but the construction cost of them can and needs to come down. And shorter term, oil is the real problem. Compressed natural gas cars are possible, they already exist, but they're modified versions of gas cars instead of being designed for natural gas, and the pressure vessel production cost could IMO come down with more competition and smart people working on it.