## Saturday, August 12, 2006

### 100 Energy Slaves per American

I was watching this guy, James Howard Kunstler, on TV talk about his book The Long Emergency who believes that we are going to run out of energy soon and it will dramatically change life in America. He said that buildings over 7 stories were going to go away because we wouldn't have the energy to run elevators and we were all going to live in small agricultural communities because the energy to transport things would no longer be available. Overall I thought he was crazy. But one questioner made a statement that I found interesting. He said that each American had 100 "energy slaves" working for us. So I decided to run the numbers and see if it is true.

The average American consumes 2,200 calories a day. The US uses 100 quadrillion BTU of energy a year (as of 2004). Divided by 300 million Americans that works out to 913,000 BTU a day. And Google tells us that converts to 230,226 calories or just over 100 times the 2,200 we eat a day. So it is true that we have 100 energy slaves each.

Our energy slaves allow us to consume much more than we would otherwise. In manufacturing, energy slaves in the form of machines build our cars, sew our clothes, and create our TVs. Our slaves provide so much that the typical American family owns more than most Egyptian pharaohs. At home we use energy slaves to wash our clothes and clean our dishes.

Of course, there are also other forms of energy we use that don't really have a slave equivalent: heating, air conditioning, refrigeration, lighting, transportation, and computing. While the slave analogy might be a little off, it is true that we feed our air conditioners, water heaters, computers, cars, factory machinery and appliances 100 times as much energy as we feed ourselves and our standard of living would be no where near as great without them.

I then became curious, how much land is needed to feed us compared to our machines?

Each year, each average American uses 341 mil BTU or 100,000 kWh. How much land would that require? As solar is the long term solution, let's calculate in terms of solar cells. 11% efficient solar cells in Austin can capture 200 kWh/yr/m^2. The average American therefore needs 500m^2 of solar cells to produce the energy he uses.

To feed humans, lets look at how much land it would require to supply all of our calories with wheat. Many foods such as meat, fruits, vegetables and nuts yield fewer calorie per acre than wheat. Others like sugar (and I believe corn) yield many more calories per acre than wheat. Using wheat might underestimate the amount of land needed, but it gives a feel for what is needed.

The FAO puts the wheat yield in the US at 3 tonnes/ha. There are approximately 1100 calories (or kCal) per pound of bread, which we will assume is the same as wheat. This works out to 2428 kCal per kg. 3 tonnes/ha therefore equals 7,284,000 kCal/ha or 728 kCal/m^2. The average American eats 2,200 kCal a day or 800,000 kCal a year. This requires 1,100 m^2 of land planted in wheat to produce that many calories.

So while our energy slaves use 100 times as much energy, they only require 1/2 as much land in order to produce that energy. This is because solar cells are approximately 200 times more efficient than creating energy through wheat. These numbers are rough, so they could be off by quite a bit, but it is definitely true that our energy slaves are much more efficient in terms of land needed to feed them than humans are.

Mark Ontkush said...

Thanks for reading ecoIron, I like your blog too. The green computing I find really interesting, I really do think it is the future.

I wonder if that's right for humans, 100 watts a day, it seems so low. But I just looked at this site
http://physics.syr.edu/courses/modules/ENERGY/ENERGY_POLICY/tables.html

and it seems that a human is in fact just like a 100W light bulb. Seems like a good deal! and the Brain for 20 watts, what a bargain that is.
Of course this assumes a fellow 'at the equator' with no other energy needs except food.

I will dig up some more data of the totl energy cycle, it's generally considered to be one of the most wasteful on the planet. Well above automobile manufacture, especially the chips. I am surpirsed that more reports don't come out on this stuff on a regular basis.

As opposed to reuse and recycle, definitely the best thing to do is 'Reduce' when it somes to computing. There are a lot of exciting new technolgoies out there that hold big promise. Probably the best ones are virtualization and thin clients. Virtualization has the potential to reduce the number of servers by 80 percent alone, so we might be talking about at 25 fold reduction in overall energy by just doing that.

It's true EPEAT is more of a 'practical' standard, dealing with what is out there instead of a more holistic approach. I very interested in what exactly is means to 'compute' at all; seriously why bother. There have been several studies that have come out suggesting that the 'informtion age' really hasnt done a lot to increase overall efficiency and productivity. People are more productive, sure, but its only because we have dumped a ton of energy in computing resources. The overall result at a national level has been about a net zero, maybe a 1 percent improvement at best.