Does a Fusion Power Plant Need Cooling Towers?
What’s the purpose of cooling towers and will fusion power plants look like nuclear fission plants?
Yes, fusion power plants will look from afar just like other power plants. Many people connect the view of the cooling towers with the danger of radiation and nuclear power plants. Truth be told, any thermal power plant uses some kind of cooling tower. Many power plants, be it gas, coal or nuclear use this type of tower to reduce the temperature of water/steam that has been run through a turbine to produce electricity.
Is radioactive water steam coming out of it? No, not even for nuclear power plants. The cooling tower is separated from any nuclear processes via a heat exchanger. Often it is water from a river or pond that is used as a cold water source. Once heated it turns into steam that drives the turbine that converts the rotational energy into electricity via a generator. From that perspective that part of the plant is the safest and most common part which still suffers from being stigmatised with all the danger people associate with nuclear plants. In general, gas and fusion reactors emit much lower levels of radiation into the environment than coal and nuclear plants (yes, coal plants can emit more than nuclear power plants in the ash from natural radiation).
How does a cooling tower work? Fusion reactors produce heat via the breeding blankets (see our article here). The heat is typically transferred via helium, a liquid metal, or salt to an intermediate heat exchanger. There, water gets heated up to steam when passing through the turbine.
The more energy the hot material coming from the blanket can transfer to the water, the higher the efficiency of the plant. It is therefore beneficial to have a liquid as cool as possible flowing into the system. In the steam engine the steam loses temperature while it produces work. The steam is led to the cooling tower to cool it down further where it rises in the colder air of the environment and condenses at the cooling tower walls, flowing down at the sides at a high rate and being pumped back into the cold water reservoir. The cycle is complete and the water can be heated again.
The cooling towers therefore increase the efficiency of the plant but are coupled to the environment temperature and to the surroundings, e.g. if a river or the sea can be used as well. If you like a more graphical explanation, check out this video which explains their function nicely.
Could we get rid of the ugly and stigmatised sight? Maybe. There are indeed designs for cooling towers that look very different from what people are used to. An example is ACC (Air Cooled Condensers) which provide a form of dry cooling. These type of cooling systems have the advantage that no water is being used but the efficiency is limited by the ambient air temperature.
The recent and upcoming power plants do increasingly make use of dry cooling (blue and orange in the figure below), however, not all will look like ACCs and some dry cooling systems have the typical draught cooling tower.
Ultimately, power plants are run by companies that will put efficiency of the plant as their priority as long as there is no major backlash from the public.
Expect to see cooling towers at the first fusion power plants!
Some exceptions apply of course. There are some fusion power plant designs that can convert charged particles directly to electricity. It’s likely that they would still use the heat produced as a bi-product in some way or the other.
