Rivers Serve As 'Horizontal Cooling Towers' For Thermoelectric Power Plants [VIDEO]

A new analysis on thermoelectric power plants highlights how the systems interact with climate, hydrology, and aquatic ecosystems throughout the northeastern U.S. and show how rivers serve as "horizontal cooling towers" that provide an important ecosystem service to the regional electricity sector - but at a cost to the environment.

According to researchers, the study shows interactions among electricity production, cooling technologies, hydrologic conditions, aquatic impacts and ecosystem services, and can be used to assess the full costs and tradeoffs of electricity production at regional scales and under changing climate conditions.

Thermoelectric power plants boil water to create steam that in turn drives turbines to produce electricity. The waste heat generated during the process required huge amounts of water, by some estimates cooling thermoelectric power plants are the largest user of fresh water in the U.S.

Water withdrawals are either evaporated in cooling towers or returned to the river at elevated temperatures. Rivers can help mitigate these added heat loads, essentially acting as horizontal cooling towers as water flows downstream.

"Our modeling shows that, of the waste heat produced during the production of electricity, roughly half is directed to vertical, evaporative cooling towers while the other half is transferred to rivers, said Robert Stewart of the UNH Institute for the Study of Earth, Oceans, and Space (EOS), according to a statement.

The study also shows that, of the waste heat transferred to rivers, only slightly more than 11 percent wafts into the atmosphere with the rest delivered to coastal waters and the ocean.

"We were surprised to find that relatively little of the heat to rivers is exchanged back to the atmosphere," said Wilfred Wollheim, an assistant professor and co-director of the Water Systems Analysis Group at EOS. Wollheim adds, "Reliance on riverine ecosystem services to dispense waste heat alters temperature regimes, which impacts fish habitat and other aquatic ecosystem services."

But the study also noted that in the face of changing climate and increasing energy demand, "it is essential to assess the capacity and associated environmental trade-offs of heat regulating ecosystem services that support the electricity sector."

Indeed, last summer a reactor at the Millstone nuclear power plant in Waterford, Conn. was shut down because the water in Long Island Sound was too warm to cool it-something utterly unanticipated when the plant was designed in the 1960s. And in July 2012, a nuclear plant in Illinois had to obtain special permission to continue operations because its cooling water pond reached 102 degrees in the wake of low rainfall and high air temperatures.