Friday, December 30, 2005

Alternative Energy is the New Perpetual Motion

Discussion on this post at The Belmont Club has lead me to start my own post on this blog about the prospects of dismantling the petrochemical industry, creating the "Hydrogen Economy", and eliminating US demand for foreign oil.

First a review of basic Thermodynamics:

Law 1:
Energy in a system can be neither created nor destroyed

Layman's Translation:
The best you can do is break even

Law 2:
Entropy in a system increases until equilibrium is reached

Layman's Translation:
You can't really break even because the usable energy is constantly decreasing

Now, the beautiful thing about oil, natural gas, and coal is that billions of plants over eons did the work of fixing solar energy into carbohydrates, and then the geothermal processes of the earth further concentrated that energy into convenient pockets of high-energy density hydrocarbons. Any alternative that humankind comes up with has to do all of this work. We might be able to do it FASTER and more EFFICIENTLY, but the energy has to come from either: the Sun (solar, wind, ocean current, deep water thermal transfer) or the Earth (geothermal). Additionally, a system could be created in which traditional fossil fuels provide the seed energy, but the system derives enough energy to restart the cycle and power other endeavors.

Let's review a few of the most talked about alternatives to oil and their production systems:

1. Hydrogen
There's been a huge buzz over the last decade about the coming hydrogen economy, which will meet all of the land transportation energy needs in the future. Well, what's the deal with hydrogen? First, the plan is to derive energy by combining free hydrogen with oxygen to yield energy. Just like the Space Shuttle main engines, only on a tiny scale. Now if creating water from H2 yields energy, then deriving H2 from H2O requires an equal amount of energy. Referring again to those 2 laws, we lose energy at both ends. Electrolysis of water requires more energy than we derive. So there would always have to be energy added to this system equal to the amount of energy produced by burning hydrogen plus the energy loss in creating free hydrogen. Right now our free hydrogen comes mostly from Natural Gas. It is a more efficient producer of hydrogen. If we don't use NG for the hydrogen or the electrolysis of water where will we get the energy?

2. Ethanol
Another much talked about solution for ground transportation. On a per volume basis, Ethanol contains only about 70% of the energy of an equivalent volume of gasoline. In the US most ethanol is derived from corn. It's basically really pure corn liquor. Most studies about ethanol net energy derivation only take into account the fuel spent on planting, harvesting, and transporting the corn itself. They fail to account for the manufacture, transportation, and distribution of fertilizers and pesticides; most of which are derived from petroleum products. Ironically, the amount of energy spent on raising corn can probably best be visualized as the 50 gallon drums used in the OK City bombing (a whole lot of ammonium nitrate, plus some diesel). Leaving out the ammonium nitrate, corn ethanol yields about 1.3 to 1 energy return. Adding the ammonium nitrate pushes the energy yield into the negative.

3. Solar Energy
Ok, so you get the point that the first two just moved the petroleum up the food chain, but what about solar power? Well, most solar cells are made of silicon and plastic. There's energy for annealing the silicon plus the plastics themselves are created from petroleum products. Oh, and solar cells are flimsy and inefficient. But let's assume that they aren't. In the temperate latitudes of Earth, the average energy from the sun is 1kWs/m^2. The average US household uses about 12kWhrs/day. So assuming that we could get 100% efficiency, and direct sunlight for 12 hrs/day, we'd need 1m^2 of solar panel per household. Not bad right?

4. Wind Power
Wind generators require an awful lot of open space in which to work. Additionally, they are only efficient in winds between 20-50 mph. Above and below that, they are fairly useless. They are also loud, ugly, and dangerous to birds. Each wind turbine is good for something like 20Kw. That sure is a lot of windmills to handle the US power requirements.

The Rub
Here's the rub, total energy consumption in the US is actually 2.9 TRILLION kWhrs per year! (This stat is total consumption including cars, etc. translated to electrical terms. Official stat was 10 Quadrillion BTUs.) That's 8 BILLION kWhrs a day, or 333 million perfectly efficient 1m^2 solar panels. Our best solar panels in the lab to about 30% efficiency, so we'd only need a billion of those. (or a 1000 km^2 panel. For reference, total land of Rhode Island is 2700 km^2) Then we'd have to store and maintain all of those.

This is just to replace fossil fuels in energy generation. In the next post, I'll discuss all of the other places where oil and natural gas are used in products.