The two adjacent solar plants known as SEGS 1 and 2 in the Mojave town of Daggett, just east of Barstow, were the first large-scale solar projects built in the USA, and they are still online. Built in 1984 and 1985 the plants have a peak output of 45 megawatts. SEGS 3-7 were built 40 miles away at Kramer Junction from 1986 to 1998, and produce 150 mw. SEGS 8 and 9 were built at Harper Lake, 20 miles away, and produce 160 mw. Together these three facilities were the largest solar power plants on earth for more than 15 years. They operate using rows of parabolic mirrored troughs, which focus the sun onto glass tubes, through which a brine heat transfer medium flows. The hot brine is pumped to steam generators, which produce electricity. Like most solar plants they are referred to as advantageous peak facilities, as they operate at their peak when it is sunniest, which is also when local power requirements are greatest, due to increased air conditioning demand.