Wairakei - The First Twenty Years

The Wairakei Geothermal Power Complex is situated five kilometers north of Lake Taupo in the North Island of New Zealand. The Wairakei system consists basically of a highly permeable hot water aquifer contained within almost impermeable boundaries. Steam is produced from the hot fluid in a three-stage flash process. Initially the first stage produced steam at 13.8 bar g (200 psig) but due to declining field pressure this has been progressively reduced to 8.3 bar g (120 psig) by mid-1980. The second stage produces steam at 5.5 bar g (80 psig). In 1972 the third stage flashing facilities were installed to utilize the otherwise waste saturated water from the second stage. This produces steam at 1.72 bar g (25 psig). The first machine was synchronized to the national grid on 15 November 1958 and the last machine in October 1964. Development of the power complex was in two stages and has a total installed capacity of 192 MWe. The final arrangement of equipment is shown in Figure la. The unusual complexity of small machines in the Stage I development is a result of the initial concept containing a heavy water distillation plant. This plant, however, was stopped early in the project, but not before manufacturing contracts had been let. At this stage it was considered too late to redesign the whole project, so, to take the place of the distillation plant, additional turbo-generators were installed. The Stage II development added 3 x 30 MWe mixed pressure machines.