Cooling Towers are not Cool
2014 EPA rules effectively prohibit once through cooling for new power plants in the United States. These rules are based on reducing larval mortality; but with little recognition that natural larval mortality is close to 1.0. In most species, overall larval survivability to adulthood is based on the population that the environment can support. In the jargon, these are called density dependent populations. In short, almost all larvae killed by a power plant will be replaced in the natural course of things.
Put another way, there is little evidence and the EPA offers none that the plant larval kills materially effect adult populations, although there will be changes in the species that hang around power plant discharges. The eco system will adjust. Usually the overall numbers increase. The most dramatic case is the manatee at St. Lucie.
Figure 1. Manatees picketing St. Lucie Nuclear Power Plant
Another big winner has been the American crocodile, a sub-species of the American alligator that has adapted to saltwater. It was just about wiped out. But it has used the cooling canals at the Turkey Point Nuclear Plant south of Miami as an incubator. It's territorial extent is now larger than anything in the fossil record. The croc has become a real nuisance in the Florida Keys. In some cases, the local fauna have become so dependent on this warm water that the plants have had to install water heaters to avoid fish kills during an outage.
Congress bears considerable responsibility for the EPA ruling. In the Clean Water Act (CWA) they called for ``best technology available" an ALARA-like concept that can easily be interpreted to mean whatever you can afford. To its credit, EPA attempted to use cost/benefit analysis in implementing the CWA. This was immediately challenged by the wealthy misanthropes. Let's call these spoiled brats, most of whom have little idea on what their wealth is based, wealanthropes. The issue went all the way to the Supreme Court which ruled the EPA could use cost/benefit analysis. But in a 300 plus page report supporting the 2014 rule, the EPA never attempted to quantify the benefit of reducing larval kill, not to mention the benefits of the warm discharge waters.1
They simply mandated closed cycle cooling, although there is nothing closed about this cycle. Consider the Columbia Generating Station (CGS) which is located well up the Columbia River. The Columbia is fed largely by snowmelt in the Rockies. The water is cold. In the winter temps are in the 2 to 3C range with the river surface occasionally freezing. Late in the summer, the temperature can get up to 22 or 23C. Windsurfers wear wet suits, year round.
If CGS had been allowed to use once through cooling, it would have needed to pull 50 cubic meters of water every second from the river. This is called withdrawal, despite the fact that that water would be returned to the river a minute or two later, albeit 10C warmer. This would have raised the temperature of the river just downstream of the plant by 0.14C and at the mouth of the river by 0.07C. The windsurfers would still need their wetsuits.
But that's not what happens. Instead CGS pulls 1 m3/s from the river. This water is circulated in a loop through the condenser and induced draft cooling towers. Each pass through the towers about 3% of the water is evaporated and the heat transferred to the atmosphere. Because this is an expensive process, the plant designers accepted a 2% loss in efficiency to reduce the flow in this loop. For a 1 GW plant, the cost of the towers, fans, etc will be roughly $200 million. This will add 10% to the should-cost of the plant.
In addition,
1) An additional 0.5% of the plant power will be lost to tower fans and pumps.
2) The towers take up roughly the same amount of space as the plant proper. The plant area will nearly double. For nuclear plants on valuable waterfront, this could be a real issue as it was at Indian Point on the Hudson.
3) Induced draft fan towers are ugly and noisy. Natural convection towers trade capital cost for fan power. Some find these immense hyperboloid structures attractive. Personally I prefer unobtrusive power plants.
4) The warm, wet conditions in the towers are excellent breeding grounds for bacteria including legionella. So the water has to be treated with biocides.
5) The towers are high maintenance items. Maintenance of the towers will add about 3% to O&M costs.
6) A portion of the water is not evaporated but must be disposed of to avoid build up of contaminants. This is called blowdown. The blowdown must be treated and then put somewhere. AT CGS it is pumped into the ground.
7) The 1 m3/s that the CGS pulls from the river is lost to the river. It can't be used for irrigation. It can't be used to produce hydropower. It can't be used to help the salmon get up the river.2
8) The towers will increase CO2 per kWh by about 3%.
There are some locations where towers are unavoidable. Palo Verdes, a desert plant, which uses treated sewage water for cooling is such a site. But for plants on large bodies of water or a big river, once through cooling is not only far superior economically, it is much kinder to the environment. Ask the manatees at St. Lucie.
Mandating cooling towers is just one more way for the wealanthropes to rob the manatee, humanity, and the planet of the benefits of nuclear power. Congress must rescind the EPA ruling.
EPA, Technical Development Document for the Final Section 316(b) Existing Facilities Rule, May 2014, EPA-821-R-14-002
The discharge will increase the vapor pressure of the river immediately downstream by one ten thousanth. The EPA argues this will increase evaporation. This is true but the process is so slow that almost all the discharged water will reach the sea,
People like the NRDC say that once-through kills millions of fish per plant per year? Is this true? What trade-off should we accept between fish deaths and efficiency?