Cooling pond and its overview

Cooling ponds are man-made bodies of water primarily used to cool hot water and/or to store and supply cooling water to nearby power plants or industrial facilities such as oil refineries, pulp and paper mills,chemical plants, steel mills or smelters.

Overview

Where sufficient land is available, cooling ponds are used as an alternative to cooling towers or to discharge hot water into nearby rivers or coastal bays, a process known as "on-flow cooling." The latter process leads to thermal pollution of the receiving waters.Cooling ponds are also sometimes used in conjunction with air conditioning systems in large buildings as an alternative to cooling towers. The pond receives heat energy from the water from the factory's condenser during energy production and then dissipates the heat mainly through evaporation and convection.After the water cools in ponds, it is reused by factories. Adding new water to the system (“make-up” water) to replace water lost to evaporation.A study published by the U.S.Environmental Protection Agency in 1970 reported that cooling ponds have lower overall electricity costs than cooling towers while providing the same benefits. The study concluded that the cooling ponds, which operate optimally within 5 degrees Fahrenheit of the natural water temperature, dissipate approximately 4 acres of thermal energy per megawatt.

Deep water cooling

Deep water source cooling (DWSC) or deep water air cooling is a form of air cooling used for process and comfort space cooling that uses large volumes of naturally cold water as a heat sink.It uses water at 4 to 10 degrees Celsius drawn from the depths of a lake, ocean, aquifer or river, which is pumped through one side of a heat exchanger.On the other side of the heat exchanger, cooling water is produced.

Basic concept

At standard atmospheric pressure, water is most dense at 3.98 °C (39.16 °F).Therefore, as water cools below 3.98 °C, its density decreases and it increases.As the temperature rises above 3.98 °C, the water also becomes less dense and causes the water level to rise, which is why the surface temperature of the lake increases in summer.The combination of these two effects means that the bottom of the deepest waters away from the equator has a constant temperature of 3.98 °C.The air conditioner is a heat pump. In summer, when the outside air temperature is higher than the building's interior temperature, air conditioners use electricity to transfer heat from the cooler building interior to the warmer outside environment.This process uses electrical energy.Unlike residential air conditioners, most modern commercial air conditioning systems do not transfer heat directly to the outside air.The thermodynamic efficiency of the overall system can be improved by utilizing evaporative cooling, in which the temperature of the cooling water is lowered to close to the wet bulb temperature by evaporation in the cooling tower. This cooling water then acts as a radiator for the heat pump.Deep lake water cooling uses cold water drawn from the bottom of the lake as a heat sink for the climate control system. Since heat pump efficiency increases as radiators get cooler, deep lake water cooling can reduce the electrical demands of available large cooling systems.It is conceptually similar to a modern geothermal sink, but is often simpler to build if a suitable water source is available.

Deep lake water cooling achieves higher thermodynamic efficiency by using cold deep lake water that is cooler than the ambient wet bulb temperature.Greater efficiency results in less electricity being used. For many buildings, the lake water is cold enough that the cooling portion of the air conditioning system can be turned off under certain ambient conditions, and the heat inside the building can be transferred directly to the lake radiators.This is called "free cooling," but it's not actually free, as the pumps and fans run to circulate the lake water and building air.Another appeal of deep lake water cooling is that it can save energy during peak load times, such as summer afternoons,when a significant portion of the total grid load is air conditioning.