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Doing the math on energy                                                                                    

Posted at: Dec/21/2009 : Posted by: mel

Related Category: Environment,

So I have been doing some reading and math with respect to a "carbon footprint". If the goal is to reduce the amount of carbon being expelled into the atmosphere, then we need a real goal....say 50% reduction. Switching from 160HP gas burning cars to 75HP plug-in electric cars is not actually a savings. In the U.S. we produce the majority of our electricity from either coal or natural gas. Factoring in transmission loss these sources still produce approximately 90-95% the same carbon as gas powered cars, especially when you factor in transmission loss. Surprised, the process of converting coal or natural gas into electrical energy is also not perfect, and a great deal of the energy in the coal or natural gas goes up the stack or out a cooling system as waste heat. I am not going to explain all the science here, but fundamentally the Second Law of Thermodynamics requires it so this can’t be avoided. Then there is the all the heat loss from the charging and discharging of a battery. Battery technology is fundamentally very heat intensive and inefficient to recharge. For the novice readers, simply said, not all the energy goes to the drive wheels, if there is heat radiating from the vehicle, it took energy to make that happen. Try charging a battery and at the same time put your hand on the battery, the heat you feel is energy that will not go to the drive wheels.

I know, there has been a lot of consumer noise about hybrid and plug-in electric cars. From the consumer standpoint of cost per mile to operate these are potentially very efficient vehicles technologies. Reducing the cost per mile as gasoline goes up and up is a good thing, but this does not mean we are actually reducing the amount of carbon being pumped into the atmosphere.

I know, you are raising your hand from the back of the room and you want to talk about solar, also known as photovoltaic. Solar electric generation is really cool stuff, but it is also backwards math. I could be sarcastic and call it “smoke & mirrors”, but I will leave that to others. Yep, it’s true that the sun is a very substantial energy source and harnessing it is a great idea. The challenge is how we make a photovoltaic cell. Current material technologies and manufacturing methods make these cells very energy intensive to produce. Once you factor in the expected lifespan of these components we are actually not any further ahead in reducing our carbon footprint.

Now I will be an optimist and believe that in a few years we could produce the solar cells economically. To meet the current energy needs of Los Angeles would by many estimates require 2300 square kilometers of desert being paved with solar cells. Even if industry could approach that kind of volume, there is still the unintended impact. 2300 square kilometers of dark solar cells would by their reflectivity change local weather patterns in ways we cannot begin to predict, but it is entirely possible they could create their own localized low pressure area. Woops, large scale solar array produces permanent cloud cover reducing effectiveness, sounds like a headline. I am also imaging the environment impact on various species of desert birds, lizards, rodents and turtles.

Based on current knowledge the remaining options are hydroelectric, wind and nuclear.

Hydroelectric is good within limitations. There is only so much water and gravity to be taken advantage of. Much like a house of cards, you just can’t change something without finding out there is an impact elsewhere later on. In the first half of the 20th century we created a lot of hydroelectric dams. Time has taught us that the damming of many of these rivers has had a detrimental impact on fish populations and waterway ecosystems. We are only now starting to see the environmental impact these dams have had. In response to the impact on fish populations and ecosystems we are now significantly limiting new dams and in many cases removing selected hydroelectric plants.

Nuclear is the logically choice, but as long as we give such a large voice to such a small group this option should be considered dead. It is interesting to note that France gets 80% of its electricity from nuclear power and by my math has the excess capacity to power half their cars if they were converted to electric. It pains me to admit that France might be doing anything right or at least ahead of us.

I know, I sound like a pessimist and I prefer not to. The big point I am try to make is that we have to be careful what we are actually talking about. If the goal is to reduce our foreign oil dependence or automobile tail-pipe emissions, hybrid-electric, and plug-in electric cars are a good path to go down. But driving an electric car does not mean you are pumping less CO2 into the atmosphere, it only means you are getting your energy from another source.

Fundamentally, if the goal is to pump less CO2 into the earth’s atmosphere we need to be willing as individuals and as communities to live a less energy intensive lifestyle. Accomplishing this could be almost earth shaking in scope. We would need to become very dependent on public transportation virtually giving up our personal vehicles. Western economies would need to move away from replaceable goods. This would mean holding on to the same TV, toaster, and cell-phone for 10 years or more which would have a significant impacts consumers and manufacturing jobs.

After 120 years of unfettered consumption of natural resources we are now beginning to see the impact. Our challenge is how we change in response. Are we trying to reduce our oil dependency, or our carbon footprint? The way we ultimately respond could be as significant to mankind as the transition over 100 years ago from an agrarian society to an industrial and manufacturing based society.

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