Electricity Generation and Transmission in Hong Kong

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Electricity is the most common energy source for homes and offices in Hong Kong. The electricity consumed in Hong Kong is generated mainly using coal, natural gas and nuclear energy as the sources. For example, the Lamma Power Station of The Hongkong Electric Co., Ltd. (HEC) and the Castle Peak Power Station of CLP Power Hong Kong Limited (CLP Power) are the two power plants that generate electricity by coal.

Fig. 1   Lamma Power Station of HEC (photo courtesy of HEC)	Fig. 2   Castle Peak Power Station of CLP Power (photo courtesy of CLP Power)

Fig. 3   Guangdong Daya Bay Nuclear Power Station (photo courtesy of CLP Power)

Hong Kong also gets its electricity from a nuclear power plant, the Guangdong Daya Bay Nuclear Power Station. Nuclear Power Station uses nuclear energy, not chemical energy, for electricity generation.

How a coal-fired power plant works

Coal-fired power plants like those in the Castle Peak Power Station and the Lamma Power Station have different structures that work together for the generation of electricity. Learn their names by playing the game below.

But basically, the working principle of a coal-fired power plant can be understood quite easily. See the diagram below.

Fig. 4   The chemical energy stored in coal is eventually converted to electrical energy in a coal-fired power plant

In fact some of the basic operation of a coal-fired power plant can be explained using everyday life things.

Fig. 5   Hot steam can push things into motion.

Have you ever observed steam pushing out of a kettle of boiling water, causing the kettle lid to rattle? If you have, you have seen that heated steam pushing things into motion. In a coal-fired power plant, coal is burnt at the boiler to produce heat and water is heated to produce hot steam. The hot steam pushes the turbine to spin. A turbine works like a windmill toy; when you blow on a toy windmill, it spins. Similarly, when hot steam flows past the blades of a turbine, the turbine catches the movement of the hot steam and spins.

Fig. 6 and Fig. 7   A turbine on the left (photo courtesy of CLP Power) and a toy windmill on the right works similarly. Both can catch the movement of moving gas to make themselves spin

The spinning turbine is connected to the axis of a generator such that the generator will turn together with the turbine. The generator works like a bicycle dynamo. Electricity is generated when the generator is rotating.

Generator is an energy converter that converts kinetic energy to electrical energy. This is how electrical energy is generated in a coal-fired power plant. Test yourself with the game below to see how much you know.

Transmission and distribution

The voltages of common batteries are quite low, for example the voltage of a dry cell is 1.5 V and that of a car battery is 12 V. But the voltage for transmitting electricity over large distance is much higher. For example, the highest transmission voltage for CLP Power and HEC are 400 kV and 275 kV respectively. Both companies also use 132 kV for electricity transmission [1]. These voltages are hundreds of thousands times higher than the voltage of a dry cell.

Fig. 8   Schematic diagram showing the transmission of electricity in Hong Kong

The high voltage reduces the current flowing through the transmission cables and thus reduces the power transmission loss due to the current's heating effect.

Fig. 9   The transmission system of CLP Power (click here to view enlarged version) (image courtesy of CLP Power)

The high voltage of transmission is lowered step by step to 220 V for the mains supply. The voltage of 220 V is still high enough to do serious damage to human body so one should be careful when using electricity.

References