One of the projects I work on is a contract with Big State Agency Whose Name I Cannot Mention Here to investigate the ecological impacts of once-through cooling. Once-through cooling, in this instance, is when coastal power plants draw water from the ocean into the plant to cool the turbines, it passes once by the condensers, and then exits again. When the water enters the plant, it passes through some screens, and biological life is either trapped on the screen, or it is so small it passes through the screen. Impingement can be fatal, entrainment almost surely is fatal (but it has not been studied in great detail).
These are largely older plants, 50 yrs or so. The plants were largely supposed to be shut down, but our State's energy demands stymied that plan. They still will be phased out eventually, the question is...when. And, no new ones will be built. This has led to a lot of attention from environmental groups. Mostly about the fact that these plants are not shut down, and even though most are running at very low capacity, if at all, they could be turned on at any time (in theory). So herein lies the problem. Lots of larvae, in particular, are getting turned into a lovely seafood stew. Is this a big deal? Politicians, environmental groups, policy makers, they want to know. The world is black and white - is this good or bad?
Well, the rest of what I write here is my opinion (insert your favorite disclosure statement here...):
It is neither black or white, but grey, and the shade of grey changes depending on the situation. To say that a certain technology is good or bad depends on a couple of things: 1) what are the costs and the benefits of that technology?, and 2) does the alternative provide a better ratio of those two things?
Once through cooling kills millions to billions of larvae. What does this loss mean to the ecological community? We dont know for sure. We've spent a lot of dollars trying to figure that out. My gut feeling is that it is not too big a deal for most (not all) species out there. It is probably a big problem for a couple of species. But, for most species, a single female fish can produce millions of larvae. Does this additional loss pose a problem? Again, dont know...
Environmentalists want the plants to close; they want the plants to retrofit immediately to dry cooling. This would, absolutely, save the larvae. No doubt about that. At what cost? Dry cooling is really inefficient compared with wet cooling. You need a lot more towers to do the job, and do it less efficiently. So, we are looking at a bigger footprint of the power plant, less efficient energy production, likely a bigger air pollution contribution (there are studies out there about this and I am not bothering to look them up specifically right now), and that is just what I can think of off the top of my head in three seconds or less. I may ask my colleague to weigh in on this.
Tearing down and rebuilding the plant comes at a cost too. I once read a study about the practicality of buying a new energy efficient car just to be driving a car that is "greener". They calculated all the costs that go into making a car in the first place, the steel, the factory, and so on...looking at the total carbon footprint of making a car. They ended up concluding that it was far better to hold on to your present car and run it into the ground. I dont know if that is still true if you redo the math with the newest hybrids - but the point is still thought-provoking. If you tear down and rebuild, what is the total carbon footprint?
So, what is my point? Just remember that there is no such thing as a free lunch. Everything has a cost, in dollars, to the environment, and so on. There is lots of talk now about switching to cleaner fuels, being greener, and so on. I am totally in favor of this, but you have to have your eyes open and make sure that you know the costs associated with your "greener" solution.
A rant for later -
Wind Energy, Not As Friendly as You Thought
Buying Carbon Credits, Does It Really Balance Out Your (Irresponsible) Actions?