Thursday, 4 February 2010

How cool is solar!

There are more cold stores in Brisbane than I ever imagined. Some are huge, think Big W on ice and multiply that by the three or four that I visited, then think maybe a few hundred others as big as a small house, then thousands as big as a room.

Being a climate change tragic, having designed and built a solar passive house in 1960, wrote letters, harassed politicians for decades, wrote plays (‘20-20 Vision’ in 1990) and even a political suspense novel about climate change (no sign of a publisher so far), basically making a nuisance of myself for half a century, I wondered at the sustainability of such huge cold stores.

So you see where I am coming from. When I was looking at the refrigeration units that ran these stores, their umbilicals as thick as your arm sucking power from the grid I wondered ‘how could we ever hope to generate that much power from renewables’!

Then my thoughts ran to the pattern of demand. Days require more than nights. Doors opening and closing gain heat, adding more daytime need. Hotter days demand more than cooler days and so on. Then I did the maths as far as I was able.

A typical large cool store, say, 50mX50m covers an area of about 2,500 m2. A roof that size would accommodate enough solar panels to generate 250K, or about 1,000 amps at 240V for an average eight hours a day. That adds up to 8,000 amp hours and must go a long way to providing enough power to run the thing. So, except for cloudy days, generation would roughly parallel demand. Fairly neat.

The same applies to solar generation for desalination plants. The sunnier the weather, the greater the demand. Really neat. So why aren’t we going there?

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