A Beneficial Use of Waste Heat
Waste heat is a necessary component of heat engines and all thermal processes in general. FPC processes are no exception and some 10 to 25 percent of the heat we generate must be released to the environment. But we do have advantages over other systems for our thermal processes are designed to be cascading. Cascading means that the waste heat of one process is the supply heat of the next process. After exploiting the heat from fusion at high temperature to produce hydrogen and electricity, and using heat at intermediate temperatures for a number of industrial processes, the remaining relatively low temperature heat will be used for several additional processes.
Production of Freshwater
The highest temperature 'waste heat' process is the desalination of water if there is a need for water and a source of non-potable water and our final thermal process will be an exchange of heat to the atmosphere. But even this exchange will be used for it will drive the airflow necessary for the collection of CO2 for our synthetic fuel making system.
Thermal desalination is a well know process. In desert regions like Saudi Arabia’s Al Jubail power station desalination may compete with power generation. From the experience at Al Jubail, for instance, a kilogram of fresh water will be produced for each 220 kJ provided to the thermal desalinator. The result, for a full-sized fusion site, is that delivering 10% of the total heat to the desalination tower will produce 3000 acre-feet of water per day.
If all of our 'waste heat' were used to make fresh water from seawater, each facility would make a river of fresh water equal to 3 percent of the flow of the Nile river.
Lithium, deuterium, brine, and salt
The processing of seawater to form fresh water as discussed above results in a brine or, if the process is continued to dryness, salt. The large amounts of lithium needed for the operation of the fusion reaction chambers can be obtained by processing the brines and solids that result from desalination. Deuterium, needed for the fusion fuel itself, is relatively abundant in seawater, found in approximately one out of every 3,200 water molecules, whereas the concentration of lithium amounts to only one out of every 2,000,000 water molecules.
As few as three full-sized FPC sites used to make fresh water from seawater could provide 100% of the demand for salt (sodium chloride) in the US economy (primary uses are clearing roads, livestock, and food). However, approximately 30 FPC sites will be needed to power the US economy as a whole. Therefore, returning excess salt to the sea in a sensitive and safe manner will be an important task for preserving the sustainability of fusion power. In fact, waste heat and waste brine or salt are the main byproducts from fusion that must be carefully managed to avoid potential damage to the environment.