Harnessing underground steam to generate electricity is one of the world’s more unusual engineering feats. The earliest experiments were carried out at Larderello in Italy, where the world’s first geothermal power station was opened in 1913. New Zealand army engineers serving in Italy during the Second World War were sent to inspect the station, but when they arrived in June 1944 it had been destroyed by retreating German forces.
New Zealand engineers visited Larderello again in 1948, when the power station had been rebuilt and was producing over 140 megawatts of electricity. Back in New Zealand, two dry years in a row had meant that hydroelectric dams could not produce the country’s energy requirements. Another source of power, independent of imported oil, was becoming imperative.
Pioneering days at Wairākei
In 1949 exploratory drilling began at Wairākei, just north of Taupō. This site was chosen because the Department of Scientific and Industrial Research (DSIR) had already succeeded in obtaining steam for the Wairākei Tourist Hotel by drilling to 170 metres; cooling water was available from the nearby Waikato River; and the land was undeveloped.
Initial explorations were encouraging, and the power station was built between 1958 and 1963. It was only the second in the world, and the first to attempt to harness wet steam (a mixture of steam and hot water, in contrast to Larderello’s use of dry steam). Engineers invented a steam–water separator, and had to pioneer ways of overcoming numerous other problems. As a result, New Zealand expertise became highly sought-after by countries interested in developing geothermal resources.
A flirtation with nuclear power
The Wairākei geothermal project was initially a joint venture between the New Zealand government and the United Kingdom Atomic Energy Authority (UKAEA) to produce power and heavy water. Heavy water (in which both hydrogen atoms have been replaced by their heavier isotope deuterium) is used to slow down the nuclear fission process that occurs in thermal nuclear reactors. It can be made by distilling ordinary water, but this process uses a lot of energy; geothermal heat was thought to be an ideal energy source. The idea was first suggested at a conference in Rotorua in 1946, and in 1954 funding was approved. However, the costs proved to be prohibitive, and the UKAEA pulled out of the project in 1956.