House of Solar

Written by Philip Proefrock
Tuesday, 18 March 2008

Lots of people are getting excited about all the various technologies for using biofuels of one sort or another as a replacement for fossil fuels, and they may present a short-term option. But looking at the various kinds of energy production that are possible gives some insight into the best directions to promote in terms of developing long-term efficient energy production.

A study cited on EV World makes a comparison between different crop- and direct-production methods of generating energy in terms of miles per acre per year, with some eye-opening information.

At the bottom end of the scale is soybean biodiesel, which can provide only 2,400 miles per acre per year. Corn ethanol is more than six times as efficient, yielding 18,000 miles per acre per year. But because of the relatively slow rate of production from plant-based fuels, these options far fall below the productivity of directly produced energy.

The same acre can produce 10 times as much energy from wind as it can from corn ethanol, 180,000 miles per acre per year. But both corn ethanol and wind power pale in comparison with solar photovoltaic, which can produce more than 2 million miles worth of transport per acre per year.

This is not to completely dismiss biofuels out-of-hand. The cost of an acre’s worth of solar PV arrays is far more than 100 times more expensive than planting an acre of corn. Many biofuels can be produced on marginal lands that are ill-suited for solar. And cellulosic ethanol can even be produced from waste, effectively making it a zero land-use fuel. And presumably the comparisons are based on sites that are optimal for each mode of generation. A site that is highly suitable for harvesting wind energy may not be a good site for growing corn, and vice versa.

The infrastructure and the existing “car parc” (the entire fleet of all vehicles in the country) is also going to take decades to turn over to the point where a significant proportion of the vehicles on the road are electric vehicles. Both a mix of energy sources and regionally appropriate choices need to be part of a comprehensive energy plan. But this offers a useful comparison that suggests where the best allocation of resources should be focused in terms of long-range planning for our energy future. ————————

Biofuels versus Solar
Lutz’s identification of ‘electric’ car technology as the top priority program at GM may prove prescient if 2006 turns out to be the year world crude oil production peaked. Assuming we are in for a gradual, but steady decline in oil production over the coming decade, the focus on electric drive and related energy efficiency technologies will be critical in more ways than we may think.

With the declining availability of once vast reserves of ancient sunlight we’ve been pulling out of the ground at breakneck speeds, future generations are going to have to rely increasingly on the available sunlight that falls on the planet each day either in the form of biomass-based fuels (biodiesel and ethanol) or on electricity generated by the wind or directly from sunlight.

Five Star Consultants’ Ken Regelson recently did a study that examined these alternatives from the perspective of “yield in miles driven per acre of land per year.” The results are pretty amazing and fall in line with a similar study done in Germany and published in Photon International. See Drive Further on Sunlight.

Obviously, the most efficient way to move a vehicle when measured in use of land area is converting sunlight directly into electricity to run electric cars, everything else with the exception of biodiesel derived from algae, pales by comparison.