I recently attended a screening of “Transforming Energy,” a locally made documentary about our energy future. The film looked at the issue from a number of perspectives. The doom and gloom future expected by James Howard Kunstler was presented alongside the optimism of inventors working on solar powered cars and the conservation ethic of people attempting to make due with entirely renewable resources. Jeremy Rifkin, whose book Entropy first introduced me to the limitations of growth in energy use and general waste, was also featured.
The movie and panel discussion that followed were hosted by Environment Colorado, a local advocacy group whose main claim to fame is the passing of state legislation mandating the use of clean, renewable energy sources. The group is currently promoting a similar federal law being debated in the Senate. Much of the discussion focused on replacing a substantial fraction of energy we use, while almost none of it dealt with limits of what we could – or should – use. There was an oblique mention of the amount of solar energy reaching the Earth, and it was implied that this limit was too high to be a concern.
My own calculations of the amount of renewable energy that can be produced in the U.S. vary from one-seventh to 17 times the energy produced in 2000. If energy consumption grows linearly over time, I project that we will reach the maximum limit in the year 3965. The bulk of the growth in renewable energy consumption (by a factor of 18 over that in 2000) will, however, have to take place between now and 2021 to keep up with the depletion of non-renewable resources; by then, we will need to be meeting ALL of our energy needs with renewable resources.