08-01-2008, 07:15 PM
Quote:The issue is that direct solar power produces about 2-4hp for the surface area of a vehicle using solar cells that are 30% efficient. If we made huge breakthroughs in solar cells and increased efficiency to 60%, we would still only get between 5hp and 10hp in perfect sunny conditions. Solar power is too dilute for vehicle power. Vehicles will need to accelerate reasonably quickly and go up steep hills so 5 hp or so will not usually be sufficient. That leads back to battery storage and the additional weight. The future of vehicle propulsion must be focused on energy storage density. Part of the process will need to be a shift of thinking from 500hp vehicles down to ones sufficient for transport. As you know, bio-fuels are really just another way of storing solar power, and photo synthesis is not a very efficient process. So, the trade off would be between using huge amounts of land for solar cell farms to capture electricity, or huge amounts of land being used to grow crops to be processed into bio-fuels. Which bio-fuel is better then, Bio-diesel or Ethanol? My feeling is that Bio-diesel seems to be currently the better more efficient way to make fuel. I think eventually to replace petro-fuels we will need to rely on a combination of technologies, including hydro, solar, nuclear, and some bio-fuels.
The reason photosynthesis isn't efficient is because 90% of the energy being stored is in turn used to maintain the survivability of the organism doing the storing. Non biological photosynthesis, as technologies advance, will circumvent this limitation. The "huge breakthroughs" you speak of still assumes a linear technology advancement path when technologies advance on exponential curves (or more accurately multiple exponential curves). The question isn't "even if we can increase the efficiency *this much*" it's a question of how accurately we can predict where we are on the technology curve for solar power (or hydrogen fuel cells, etc. etc. etc.). The efficiency is going to get better, I'm confident in making that prediction. Thinking about technology in a linear fashion tends to lead to two falacies: we overestimate tech advancements in the short term, and we vastly underestimate tech advances in the long term.