I’m Dying For A Drink!

Wednesday, May 27, 2009

This day’s ABS News has an article on rainwater tanks titled “When saving water costs energy”.

http://www.abc.net.au/news/stories/2009/05/27/2582450.htm?section=australia

Let’s attack that five-word headline first.

Everything costs Energy. (That’s the first 3-word refutation of a 5-word headline I’ve made today. Another record broken!).

It’s called variously “Entropy” or “The Universe is running down”, “You can’t get something for nothing” and “There’s no such thing as a Free Lunch”.

Walking to the water tap, no matter the water source, costs energy. Carrying your glass costs energy. Lifting the glass to your lips costs energy. Breathing costs energy. Your beating heart costs energy. Everything IS energy, for the whirling electrons and vibrating atoms ARE energy.

OK, it turns out that the particles of which electrons, protons and neutrons are made are really nothing more than mathematical equations, but I digress.

So, straight off - the headline isn’t educating us to any unknown fact; let us be aware that this will be another scare-story.

I know a bit about rain-water tanks, having lived and worked in the goldfields and wheat belt of Western Australia and Adelaide in South Australia for twenty-one years. I’ve worked on remote farms with rain-water tanks, and owned a house in Gawler that possessed TWO rain-water tanks, one of which we chose to use for our kitchen needs.

Rain-water tanks are good; they divert water from the roof to a cool supply available throughout the house.

Without water we die. Our cells are largely water.

In the body of the article we find this: “They found in most cases pumping water from rainwater tanks is more energy intensive than getting it from mains water, although lower than getting it from desalination.”.

Two things:

1. Energy consumption is always calculated across a system boundary. For example, if we calculate the cost of running the water-treatment plant machines, we get a certain value for the “amount of energy [per] kilolitre of water”. But I’ll bet that doesn’t include the energy required for electric lights, refrigerators in the staff cafeteria or the works canteen, or the energy used when the workers drive to work. Why not add that into the equation? Theory is, if we all used rainwater tanks we wouldn’t need that expensive overhead. Of course, we’d need to pay displaced workers unemployment benefits ….

2. Without water we die. There’s no way to factor energy costs into a home that does not have access to mains water. Now there aren’t many homes in Australia without access to mains water. Search the web for "Goldfields water supply" (for once, with quotes!) for an example. But if you don’t have mains water, you need rain water, in which case comparative studies of energy costs are irrelevant.

The bottom line: To make a true cost/benefit comparison we need to examine many more factors, such as we see for home-based energy reducing the load on a national energy grid. If each household obtained 30% of its clean water from rainwater tanks, we could get by with a smaller mains-water supply, or support a larger population with the same water supply; take your pick.

I smell a grant proposal!

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