Thermal generation supplies up to 50% of power in Aotearoa.
Thermal power is presently considered the insurance card underpinning the security of Aotearoa’s electricity system by the Government. However, sustainable and renewable energy production is the preferred option for Aotearoa’s future. Carbon emissions from thermal power plants are considerable, and steps continue to be taken to reduce emissions and enhance the efficiency of thermal power plants using new equipment and technology.
Thermal power stations use steam as the engine that generates electricity. Water is heated and turns into steam, which then spins the steam turbine which drives an electrical generator. In Aotearoa thermal power plants use coal, natural gas, wood waste, and geothermal power to generate steam.
Water is the second most important resource used in thermal energy production, after fuel. Some of the water used is converted to steam which drives the generator producing the electricity. However, most of the water is used for the condenser cooling. The condenser cooling water is abstracted from waterways located near thermal power plants.
The generation of usable electricity creates a lot of wasted energy in the form of heat which then needs to be cooled before it can be released into the environment. This water is much warmer than the original water, and the temperature is usually reduced using cooling towers to remove the heat, where water is circulated to absorb it. The water can then be either returned to the waterway from where it was extracted, or cooled using air contact and evaporation in a cooling tower.
Fish are also easily drawn in (entrained) by the cooling water into a power station and then become impinged (stuck) on the intake screens. This can cause severe injury or death to some mahinga kai species and can result in large numbers of fish deaths during migration periods.