I’ve written before about the importance of conservation, though in many cases, I’ve assumed that its impacts go without saying. I recently ran across a simple analysis that may help me to articulate why I see energy (and other resource conservation) as the crux of an energy solution, rather than icing on the cake.
Consider the example of an incandescent light bulb in a lamp in your home, powered by electricity from a coal-fired power plant. This is a typical, though somewhat simplified scenario:
Coal is a source of chemical energy. Converted to thermal energy (heat) in a furnace, we lose about 15 percent of its energy to inefficiency, limitations of insulation, moving fluids and fuel, &c. We convert this thermal energy to mechanical energy by means of a turbine that loses more than half of the remaining energy overcoming friction and other impediments. The generator loses another 5 percent, while transmission, distribution, and grid congestion claim almost 10 percent more. The bulb itself converts electricity to light with about 5 percent efficiency (95 percent of the energy is wasted). The end result is that the light from the bulb represents a more than 98 percent loss of energy from the original coal. Put another way, every unit of light energy saved conserves 60 times as much chemical energy in the form of coal. That doesn’t include the energy spent mining, processing, and transporting the coal to the power plant, nor disposing of the 1000 tons of waste that a medium-size coal-fired plant produces in a day.
It turns out that Mom was right. We really should turn out the lights when we leave the room. Evidently, it actually conserves about 60 times more energy than it seems to. How’s that for an easy way to be the solution?
Image source: Victoria & Albert Museum
Friday, December 5, 2008
We Can Do It!
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12 comments:
Although much depends upon the type of coal and on the newness and efficiency of the coal fired electricity plant, on average the thermal energy content of coal is about 3 KWH per pound. Due to the inefficiences ERD mentioned, only about 40 percent of the thermal energy in coal is converted to electricity. So on average one can say that it takes approximately 1 pound of coal to generate 1 KWH (or 1,000 watts) of electricity. If you had a regular old fashion 100 watt lightbulb, and you ran it for 10 hours, you would have consumed one pound of coal.
Of course your one pound of coal has to be mined. Currently in eastern Kentucky, a typical stripmine gets about 1 pound of coal for every 7 pounds of rock and soil removed -- sometimes more, sometimes less. Each pound of rock and soil (and coal) that gets moved requires diesel fuel to run the huge earth moving machines and draglines. Both the 1 pound of coal and the 7 pounds of rock and soil have to be removed from the site, so that's more diesel fuel expended. The coal then has to be transported dozens of miles by truck to tipples where it is loaded on trains (both of which run on diesel fuel), to be transported to the electricity generating plant. So in addition to the energy of the coal used to create the electricity, substantial energy from petroleum (as diesel fuel) is used to mine and transport the coal.
erd it troubles me you find yourself being more concerned with a planet then you are with human beings!!!
PJ,
Where have I stated that I'm more concerned with the planet than with human beings?
erd your assumption that the earth should overly occupy our focus is statement enough!!
PJ,
I'm not sure what I've written here that assumes what you've suggested. I don't think that the environment is more important than people. That would be a peculiar thing for me to beleive, given much of what I've written on BIA and on my former blog. If there's some previous post or comment you have in mind that bears out your concern, by all means, refer me to it. I'm happy to address any confusion. Honestly, it looks like you're simply repeating a tired, false stereotype here.
It's worth saying again: Improving environmental quality is a way to serve other people.
In this post, I've suggested that people avoid wasting something that they're not really using, and pointed out that this has greater savings than are imediately obvious. What's wrong with that?
i am not confusing anything erd. i appereciate a desire by you to have a "healthy" world. but i worry your view means mankind should eliminate his lifestyle to accomodate that. if that is true you have put the enviroment ahead of mankind's existence.... if you have time stop by my blog (shameless plug) tomorrow. i very much look forward to your response to this post!
PJ,
If you remain concerned that I'm putting the natural world ahead of people, then by all means, show me something that I've written that bears this out. Or explain why there's something inherently wrong with avoiding, reducing, or preventing waste.
If I turn out a light that I'm not using, because I want to save energy, who is losing? How does this put the natural environment ahead of people?
Who is your victim?
Two comments. First, the easy one addressing Pat's concern about putting the planet ahead of humanity. I don't allow people to defecate on my bed because it's bad for my health. It's not that I care more about the bed than people, it's that I care about my own well-being. I have no problem with them defecating in the toilet, because that isn't bad for my health.
But now to the bigger problem. I own 40 acres of forest land. I spend my exercise time outside working on the land. One of the most common tasks is thinning the thickets and removing dead trees. I don't bother cutting down the dead trees; I wait until they fall naturally. Then I limb them and drag the log to the firewood pile where I cut it up for firewood. (We can discuss the issues raised by that later on, if you wish.)
All this leaves a lot of slash -- the dead limbs and small trees cut down during thinning. I pile up the slash into slash piles. Now, standard forestry practice at this point is to burn the slash pile during the winter. However, I have decided not to burn the slash piles. Instead, I leave them standing as housing for small creatures, and in the expectation that, as they rot, the carbon released will be trapped in the pile and eventually sequestered in the soil.
The problem with this is that, in the several decades it takes for a slash pile to decay, it constitutes a fire hazard. It will increase the temperature of any fire moving through the area, and the prime strategy in fire management is to keep the fire cool, not stop it.
But here's the real killer. The prevention of CO2 emissions is valued now at $35/ton. A slash pile will typically contain maybe a ton of carbon. So why am I going through all this hassle for a lousy $35? Indeed, if I simply ignored all this carbon stuff and instead spent the time I now spend on carbon sequestration on earning money, I could earn more than $35, use the $35 to pay somebody else to reduce carbon emissions, and still come out ahead. Right?
Sue,
Thanks for the numbers on mining effort. This really underscores the point a little savings at the point-of-use is magnified into signficant savings in the production process.
Chirs,
I'm not familiar with the use of slash heaps as a carbon sequestration strategy. At first cut (no pun intended), it seems that on the large scale, this would actually be counter productive. The increased risk of escalating ground-fires means that over time and space, catastrophic burns that convert standing trees back into atmospheric carbon would also increase. Without any numbers, it's impossible to say which activity would be favored by risk and return. However, I'm inclined to think the slash piles would net a negative carbon sequestration.
From the financial standpoint, it also doesn't show great return, but that's more a matter of opportunity cost. And, of course, it would make sense to consider your neighbors as well. I'd hate to promote a fire that charred my neighbor's property.
Why do you ask?
Good point about their contribution to other trees burning. The real effect lies in where the firefighters decide to make their line. If a slash pile pushes them back 50 feet, that leads to many tons of wood being abandoned to the flames. Still, I have to compare this with the low probability of a fire. We've gotten pretty good at keeping fires down in my neck of the woods. There hasn't been a serious fire within a mile of my place since the 1930s.
Chris, interesting dilemma. First I would think about what happens in the wilderness -- the whole tree remains on the ground, and that periodic fire is healthy for forests -- and balance that against the fact that you are not talking about remote wilderness, but rather woods adjacent to human habitation (what we sociologists like to call the "wildland-urban interface." One thought -- leave the tree trunks to rot and create nice animal (and microbe) habitats and clear away the smaller slash and use that in your fireplace or outdoor fire pit.
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