Tag Archives: power

Cooling towers

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cooling-towers

A pair of metal cooling towers at a power station in the Ukraine.

Cooling towers are an essential part of many power stations. Although they are most commonly associated with nuclear power stations, they are found in any power station that uses heat from burning fuel to generate electricity. (Drax, a coal-fired power station that is the largest in Western Europe at 3960 megawatts has twelve cooling towers.)

An aerial view of Drax coal-fired power station.

The purpose of a cooling tower is to extract waste heat from the power station so that the working fluid (water) can be reused. This waste heat passes into cold water, heating it in the process, and this warm water is then fed into the cooling tower where it cools and is then reused. The separation of the working fluid (purple and blue) and the waste heat extraction (grey pipes) is obvious in the diagram below.

cooling-tower-diagram

The space below the water inlet is filled with a material designed to increase the surface area of the water in contact with the air, helping to speed up the process of heat loss.

fill-plates

Fill plates mounted underneath the outlet nozzles.

The hyperboloid shape of cooling towers ensures continuous non-turbulent airflow, maximising the amount of air per unit time moving through the tower. Air enters at the bottom of the tower and accelerates up the tower as it is heated by the warm water, drawing fresh cool air in at the bottom due to the stack effect. In the photograph of a disused cooling tower below, the spaces at the bottom of the tower through which air enters are clearly visible.

inside-cooling-tower

Source: Tom Blackwell

Standby power

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We are constantly being bombarded with messages to turn devices off at the mains, rather than leaving them on standby. But is it worth it? How much energy does this actually save?

standby-light

According to the Lawrence Berkeley National Laboratory a television left on standby uses about one-and-a-half watts. For comparison purposes, a power shower uses between 7500 and 10800 watts. That means that for one fewer ten-minute (9 kW) shower you can leave your TV on standby for another forty-one days and still have used less electricity than you would have.

A study published in 2010 in the Proceedings of the National Academy of Science showed that people were far more likely to select curtailment activities (turning things off) rather than efficiency savings (like cutting a minute off your shower), despite efficiency savings being more likely to reduce energy consumption. Turning devices off at the mains, rather than making choices that would save far more energy, is another example of this.