Natural Draft Towers

Cooling Tower(Supply) Basin

Water is supplied from the discharge of the Circulating Water System to a Distribution Basin, from which the Cooling Tower Pumps take a suction.

Cooling Tower Pumps

These large pumps supply water at over 100,000 gallons per minute to one or more Cooling Towers. Each pump is usually over 15 feet deep. The motor assembly may be 8 to 10 feet high. The total electrical demand of all the Cooling Tower pumps may be as much as 5% of the electrical output of the station.

Cooling Towers

There are 2 types of towers - mechanical draft and natural draft

Mechanical Draft Towers

	Mechanical draft Cooling Towers have long piping runs that spray the water downward. Large fans pull air across the dropping water to remove the heat. As the water drops downward onto the "fill" or slats in the cooling tower, the drops break up into a finer spray. On colder days, tall plumes of condensation can be seen. On warmer days, only small condensation plumes will be seen.
	Courtesy NSP

Natural Draft Towers

This photo shows a single natural draft cooling tower as used at a European plant. Natural draft towers are typically about 400 ft (120 m) high, depending on the differential pressure between the cold outside air and the hot humid air on the inside of the tower as the driving force. No fans are used. Whether the natural or mechanical draft towers are used depends on climatic and operating requirement conditions.

Courtesy KKN - Liebstadt NPP

Simplified Diagrams

The diagrams below illustrate the arrangement of components within the system and the major flow paths.

Forced - or Natural Draft Cooling Tower

The green flow paths show how the water is taken from a river (yellow) to an intake supply basin (green) that the Circ Water Pumps take a suction from. The water is then pumped to the Condenser where the water is heated. The water is then sent to an exit distribution basin where the water then can be returned to the river and/or pumped by the Cooling Tower Pumps to the Cooling Towers then the water returned to the intake supply basin where the water can be reused.

Natural Draft Cooling Tower

	The green flow paths show how the warm water leaves the plant proper, is pumped to the natural draft cooling tower and is distributed. The cooled water, including makeup from the lake to account for evaporation losses to the atmosphere, is returned to the condenser.
Courtesy CP&L

For pictures of natural draft cooling towers at a variety of plant, please see the Natural Draft Cooling Tower Photo page.