Power generation is affected by climate and the onset of climate change has reduced rainfall in many regions of continental North America. By 2004, successive years of low rainfall in the watershed area of Quebec's James Bay hydroelectric project reduced water levels to near critical in the holding dams. The Southwestern United States has also undergone several success years of low rainfall. Long-term weather patterns have indicated that the earth has undergone several periods of low rainfall during its past history. During those periods, the human population was a fraction of what it is at the present day.
The human population has steadily increased since the last periods of reduced rainfall and has become highly urbanized in most regions of the world. This population requires a steady supply of electrical energy as well as clean water for its personal and economic survival. During the 1950's by an engineer named Garrison recognized that America had a future need for an expanded secure supply of fresh water. He became aware that most of the rainfall that fell over Canada collected into rivers that flowed toward the Arctic and into Hudson Bay and devised a plan that became known as the Garrison diversion. The plan proposed to divert fresh water from Northern Canada by pipeline into heavily populated areas of the USA.
Today, several large hydroelectric dams that supply power to parts of Canada as well as to the north central and northeastern USA are located on some of these very rivers. Garrison's diversion scheme would require that several Canadian hydroelectric dams be closed in order for water to be diverted to southern destinations. New thermal power stations would need to be built to replace the hydroelectric installations as well as to provide energy to pump water against gravity to enable it to flow south to American destinations. Additional energy would be needed during cold northern winters to prevent water from freezing in the pipeline system. The system could cost well in excess of $100-billion to construct and several million dollars per year more to operate.
The American power industry may be able to offer several more cost-effective alternatives whereby several American coastal cities may gain access to a supply of fresh water for human consumption. Some of the technology was developed for use in the Middle East where very little fresh water occurs naturally and where a growing population has a growing need for fresh water. Heat rejected from thermal power stations has been used to desalinate ocean water in hot and arid regions. Several thermal power stations are located near the coast in several American states and the reject heat can be used for this purpose. During winter, snow falling in the northern states usually ensures an adequate supply of water for the human population.
During the hot summer months, large cities like New York City, Chicago, Los Angeles and several other southwestern cities face constrained water supplies and water restrictions. The City of Santa Barbara in southern California reduced fresh water consumption by installing a duplicate municipal plumbing system that enabled toilets to be flushed using ocean water. This pioneering conversion could be undertaken in numerous other coastal cities and it may take decades for major cities the size of Los Angeles to install new independent plumbing systems by which to operate the sewer systems. It is likely that the total overall cost of installing such systems in America's major coastal cities may be less than constructing and operating a modernized version of the Garrison diversion scheme.
An initiative to introduce duplicate plumbing systems into coastal cities could coincide with initiatives to make large cities more energy efficient when it comes to heating or cooling large numbers of large buildings. During summer, cool water from the ocean may serve as a heat sink and reduce the amount of energy that large skyscrapers use for air conditioning. The City of Toronto in Canada recently introduced a central cooling system for the central business district where cold water from the bottom of Lake Ontario is used to cool an entire district of large skyscrapers. A similar result may be achieved if exhaust steam from a nearby steam-thermal power station is used to drive vacuum refrigeration technology, a large-scale technology uses water as a refrigerant and can cool it to as low as 5-degrees C (41-degrees F).
A 1,000-Mw coal fired or nuclear steam power station may operate at an efficiency of 40% will reject the equivalent of 1,500-Mw in heat. During winter, this heat may be used for district heating within a radius of up to 40-miles from the power station. During summer, the heat rejected in the exhaust steam may be divided between energizing water desalination technology and driving steam vacuum refrigeration equipment that can typically operate with a coefficient of performance (C.O.P) approaching unity. The cooled water would be pumped through the same piping systems that carry warm water during winter for the purpose of district heating.
Natural gas fired power stations that operate in the Middle East use gas turbine engines of up to 380-Mw each. These engines are often equipped with heat exchangers that are located downstream of the exhaust systems and for the purpose of using engine exhaust heat to operate ocean water desalination equipment. The amount of heat in the exhaust is also sufficient to provide district heating during winter or to raise steam at low pressure that may drive steam vacuum refrigeration systems during summer. Water vapor is also a major component of the combustion gases of gas turbine engines that operate on natural gas. These gases (CO2 and H2O) are free from engine lubrication contaminants and the vapor may be condensed via heat exchanger using ocean water as a heat sink. The water would likely be pure enough for human consumption.
America's Southwest and Midwest has growing need for fresh water during summer while the Mississippi River usually overflows its banks every spring. The Red River flowing from North Dakota into Manitoba overflows its banks there almost every spring. At the same time, water levels in Lakes Superior, Michigan and Huron have been steadily dropping for several years. Lakes Superior and Michigan may have enough storage capacity to contain excess spring water pumped in from the Mississippi and Red Rivers. To hold extra water in Lake Michigan, a control dam would need to be built at the Strait of Mackinac. Shipping locks that can operate as control dams already exist at the exit of Lake Superior.
The river water would be pumped into the big lakes at a time of year when the demand for energy to provide winter heating is in decline across North America. Extra electrical generation capacity may be available during spring when no air conditioners would be operating. During off-peak periods for power stations during spring, the added electrical power would be used to drive water pumps. As America's demand for fresh water increases, the power industry would come to play a more significant role in providing fresh water. The combination of pumping fresh water into storage at northern latitudes, desalinating ocean water from the exhaust heat of power stations, condensing the exhaust of natural gas powered gas turbine engines and using ocean water to flush the bathrooms would all contribute to helping meet America's need for water. The power industry has the potential to become an integral part of the solution in this regard.