One of the more interesting posts I read recently was Nine Challenges of Alternative Energy from The Oil Drum. The original post provides a good summation of the problems facing us as we try to go to alternative energy sources.
The author points out that alternative energy falls into two categories: substitutes for liquid fuels (primarily for transport) and generation of electrical power. One of the first things I noted was the absence of nuclear power in the list of alternates on electricity.
One of the first challenges is scalability and timing. How can we get enough alternative energy soon enough to do any good? Things do not look very promising -- there isn't enough on the horizon to replace what we have and expect to lose.
Commercialization is a challenge in our market driven economy. It typically takes 25 years to get a new process going, and we may not have that much time left with our present energy sources.
Substitutability (strange word!!) is an issue, because we want a drop-in replacement, like for gasoline or diesel, and there is not really one. That means a new infrastructure will be required to support the new energy mode.
Material Input Requirements pertains to what are the raw materials necessary to obtain the new energy source or process. The scarcity of certain metals and rare earths bring to question the feasibility of some energy-centric ideas. Even LEDs may be come a problem because of the special materials needed to make them.
The author sees the intermittancy of various energy sources as being a major challenge in their adoption. The wind does not always blow, so what do you do when it doesn't if you are depending upon wind turbines. At least the sun shines, except on cloudy days. Only nuclear power can achieve a 100% availability factor.
Energy density is an issue. Fossil fuels are among the most energy dense compounds available. When you compare gasoline with battery weight, the difference is orders of magnitude. Only nuclear fuels come close to the same density.
Water is a challenge, because for the most part every alternative considered needs water, and that is becoming one of the most precious commodities. Will there be enough water to produce the alternative, or the means to do the alternative?
Receding Horizons is a real issue, because we have been waiting around for so long we are losing the race for not starting it. The cost of doing things keeps going up, so our comparisons of when it will be possible to do something keeps slipping further into the future.
EROI is a factor. If you must spend more energy creating energy than what you get out, you can never make it up. Already, studies are showing that tar sands, grain ethanol, and biodiesel may cost more energy than you can get out of them -- you are ahead if you don't produce them.
The comments that follow the blog post are also most interesting. Take a look at the original article and those comments.
sam
