Modern Cooling Technologies Protect Fish

Power generation is a simple matter of spinning an inverted electric motor to generate electricity. Most power plants do this by boiling water. Water is heated in a boiler creating extreme pressure. Steam shooting from the boiler at very high speed turns a turbine that is attached to a generator. At the back end, the steam (now at low pressure) is sent to a condenser to cool back into water and recollect. The water must be very pure because any dirt or contamination in the steam could damage fast spinning turbine blades. So, the same water cycles continuously through this closed loop system. The colder the plant can make this water before returning it to the boiler, the more efficient the plant runs.

Cooling the steam without destroying the environment is the problem. But solving this problem is not much of an engineering challenge, in fact, the solutions are surprisingly low-tech. Fish kills can be drastically reduced or entirely eliminated with modern cooling technology. In this case, by ‘modern’ we mean technologies that have been in common use for the past 40 years or longer:

Open-Cycle/Once Through Cooling. The problem. Cold water is drawn from nature, used to cool the condenser and discharged as waste back into the waterway 15 to 34 degrees warmer.

Closed-Cycle Wet Cooling. Closed-cycle wet technologies are a vast improvement over once-through cooling. Cooling water is circulated through the plant to absorb heat from the steam in the condenser. But instead of being dumped into the environment it is piped to cooling towers where it is mixed with air. Evaporation cools the water and it is recirculated.

These systems are better, but they do still require water to replace evaporative loss and cause some thermal and chemical discharges to waterways. In all these systems cut water usage from open-cycle plants by 95 percent or better. If closed-cycle wet cooling isn’t the “best available technology” for cooling it is only because dry systems are even better.

Closed-Cycle Dry Cooling. Air cool systems work like car radiators, piping water through thin coils and blowing air over the coils to cool it. This system can be retrofitted onto any existing power or industrial plant, virtually eliminating the need for water and decoupling power plants from natural waterbodies.

Direct Air-Cooled Condenser. This is the most water efficient cooling system. It eliminates the need for cooling water entirely — circulating steam directly from the turbine into an air cooling system, then returning cooled water directly to the boiler. This system cannot be retrofitted onto existing plants because of the large pipes required. But this technology is being applied to new plants all around the world.

Dry-cooling technology was developed for sites without access to water. But new power plants are using the technology all over the country, not just for the many environmental benefits but because it reduces permitting time. Air-cooled technology is effective, reliable, affordable and available: More than 60 dry-cooled plants are currently operating in the U.S., 600 worldwide.