*Bee-bee-bee-beep bee-bee-bee-beep*
A lad rolled over and flicked aside the corner of his bedroom curtain. It was 6 AM, and a glint of light from the West told him it was going to be a pretty clear day. He sat up and gazed for a few seconds at a cluster of ten giant silver disks through sparse clumps of mulga occasionally interspersed with wattle or gum trees, each disk now twinkling in the first rays of dawn.
Umuwa is an administration hub occupied by roughly 80 full-time residents. It services the
Anangu Pitjantjatjara Yankunytjatjara Aboriginal Lands in South Australia. Umuwa is located at
-26.465404, 132.042150, roughly 450 kilometres South-South-West of
Alice Springs.
The dishes
In September 2003, Melbourne-based Australian company Solar Systems commissioned the world's first production system to employ their CS500 parabolic solar concentrator. The AU$2.5M power plant, known locally as the "sun farm", was constructed just West of Umuwa. Its 10 (5x2) dish array was designed to supplement the electricity distribution grid diesel gensets in Ernabella, with the intention of later building a 3MW on-site station. The CS500s each consist of 130 square metres of mirrors in 112 individual pieces that concentrate the sun's rays roughly 500x onto a "receiver" at the focal point of the dish. This so-called receiver is a densely packed matrix of silicon-based photovoltaic (PV) cells capable of producing a peak output of 22kW. Temperatures inside the receivers can theoretically reach over 100,000 degrees Kelvin, so their temperatures are regulated by a fan-forced tubular heat exchanger. The PV cells are connected to matched inverters and power conditioners to ensure a clean, stable 415 volt, 3 phase AC supply reaches the grid. Each dish independently tracks the azimuth and elevation of the sun from sunrise to sunset.
The site
The site also houses a fully automated control room, self-contained electrical systems shipping container including batteries and transformers, storage shed for spare parts etc, elevated work platform for maintenance, pumping and cooling system hut, and workers' quarters. The plant was subsidised by the South Australian and Northern Territory governments.
Problems
When the plant was first installed, it was unreliable. Bird excrement severely deteriorated mirror performance despite daily cleaning. During cloudy periods, the solar cells' output fluctuated dramatically. When the existing diesel generators couldn't keep up with the rapid increase in load, they would stall, leaving every grid-fed community temporarily without power. In 2004 Dudley Dagg, operator of the Ernabella power plant was interviewed on the ABC's "Nexus" program, and I quote: "And when the sun farm doesn’t produce, it drops the load on to this power station. This plant wasn’t designed for taking say another 50 per cent load within a couple of seconds." A lightning strike took the entire sun farm offline for several months in 2005.
Upgrades
The original air-fluid heat exchanger has been replaced with a network of subterranean polythene pipes, reducing the operating temperature of the system and boosting overall efficiency of the PV cells. The national and state governments provided a AU$1.2M grant in 2008 to upgrade the PV cells, bringing the annual output of the plant from 335MWh to 715MWh.