Global Freshwater Thermal Pollution from Steam-Electric Power Plants with Once-Through Cooling Systems

Abstract:

Thermoelectric power generation requires large amounts of cooling water. In facilities employing once-through cooling systems the heat removed in the power cycle is rejected directly into a water body. Several studies have focused on the impacts of power-related thermal emissions in Europe and the U.S., in terms of river temperature increase and the capacity for power production, especially in the light of legislative measures designed to protect freshwater bodies from excessive temperature. In this work we present a comprehensive, global analysis of current freshwater thermal pollution by thermoelectric facilities. The Platts World Electric Power Plant (WEPP) database was the principal data source. Data gaps in the principal parameters of the steam-electric power cycle were filled in by regression relationships developed in this work. Some 2400 steam-electric units using once-through freshwater cooling systems, amounting to 19% of the global installed capacity of thermoelectric units, were identified and georeferenced, and a global view of thermal emission rates was achieved by systematically solving the Rankine cycle on a power generating unit level. The rejected heat rates are linearly proportional to the steam flow rate, which in turn is directly proportional to the power produced. By applying the appropriate capacity factors, the rejected heat rate can be estimated for each unit or agglomeration of units at the desired temporal resolution. We coupled mean annual emission rates with the global gridded hydrological-river temperature model VIC-RBM to obtain a first view of river temperature increases resulting from power generation. The results show that in many cases, even on a mean annual emission rate basis and a relatively large spatial resolution of 0.5 x 0.5 degrees, the local limits for temperature increase are often exceeded, especially in the U.S. and Europe.