Posted by
crosspatch on Saturday, April 11, 2009 10:39:18 PM
There is a certain sense of validation when one sees an article where someone else has independently reached the same conclusion one reached themselves. In this case I was reading
an article on wind power which explains how it has the potential to actually increase CO2 emissions rather than reduce them.
Let's compare wind with nuclear for a moment to illustrate this point. Energy is added to the grid when a nuclear plant is built without any increase in CO2 emissions from energy production. Nuclear generation operates 24 hours a day, day in and day out. Nuclear plants operate most efficiently at nearly full output and are slow to throttle up and down with load. Excess energy generated in off hours is dumped as heat.
Now lets compare that to a modest wind field, say 100 megawatts of power. What happens when the wind isn't blowing? People are still going to need to see in the dark, pump water around, wash their clothes and cook their food. First of all, in order to get an average of 100 megawatts of actual generation, you need to install between 350 to 900 megawatts of generating "capacity". This is because even when the wind is blowing, the units do not always generate at full rated capacity. Add in turbines that are down for maintenance reasons or iced over or otherwise not producing and you get average generation very much below rated "capacity". Figures for actual generation are between 10 and 30 percent of capacity depending on who you listen to. So lets split the difference and say you need to install 500 megawatts of capacity to average 100 megawatts of generation.
Ok, so we switch our new wind turbine field onto the grid and ... nothing happens because it is a calm day. No power is being generated. But demand is still there so it dawns on us that we must build a 100MW fossil fuel plant to pick up the slack for when our field isn't operating because we have sold 100MW of power to people and we had better deliver. Mrs. Finkenstarkle isn't going to care that the wind isn't blowing, she has two kids to get fed and ready for school and she needs electricity to do that. You still have to meet demand. So you fire up your 100MW fossil fuel plant and burn, say, natural gas until the wind starts to blow.
Now the breeze comes up and you can start to throttle back the gas turbine but the winds are "light and variable" which means the output is all over the place. You start getting 200MW out of the system and so you take the turbine offline and just as you do that the output drops to 50MW so you need to start it back up again.
The electricity demand for next Thursday afternoon at 3PM can be accurately predicted within a reasonable margin of error. The electricity available from wind next Thursday afteroon at 3PM is anyone's guess. That is the fundamental problem. Supply must be reliable. The nature of wind is that it is very unreliable. In order to provide a reliable source of power, one must augment the wind generation with conventional capacity. Had nuclear been chosen instead of wind, there would be no need for a fossil backup plant and CO2 emissions would be greatly reduced.
All of this, of course, is based on the notion that CO2 emissions are harmful in any way which nobody has shown to date to be true. But that is a whole other post.