Solar heating: it’s not that complicated

Tavern of the Seas

WHILE I was reading up on the history of solar heating and solar power for yesterday’s Tavern column I came across several designs for building your own DIY solar water heater. Actually, it’s not at all complicated. I remember once having a black hosepipe in my garden, and as I am not a very neat person I regularly left it lying about on the lawn instead of coiling it up carefully and hanging it up out of the way.

One day I needed to fill a bucket with water from the hose and when it was full I almost scalded my hand. Simply from going through that hose in the sun, the water had become too hot to touch.

On our family farm in the Karoo, my brother built a very simple solar heater. He made a large, flattish cone out of sheet metal and coiled black polythene pipe around it. He then built a low wall around it and covered the whole lot with a sheet of glass.

He and his family have enjoyed free hot showers from this heater for years.

Looking at the designs, including some from old issues of Popular Mechanics magazine, a few basic principles emerge.

One is that matt black absorbs heat very efficiently, so any heater you build will be more effective if the water container is painted matt black. Another simple rule is that hot water will rise to the top of a heated container, so you need to bring cold water in at the bottom and let it exit through the top.

Once you have heated the water it needs to be insulated so the heat doesn’t escape into the atmosphere. There are many insulating materials available today, so that shouldn’t present a problem.

Using these rules it should be an easy matter to rig up a system to provide hot showers from your garden tap.

On another aspect of solar heating, I was intrigued to learn that architects in ancient Greece and Rome placed great importance on the direction in which buildings faced. Whole suburbs were designed so every house faced south, to catch the winter sun, and they had a roof overhang to shade the south walls in the summer.

(Of course in the southern hemisphere houses built on that principle should face north.)

It often seems to me that modern urban planners just grab a piece of land and squeeze as many buildings on to it as they can, regardless of which direction they face.

We must lose billions of kilowatts of power annually through bad urban planning.

Many of he old farm houses in the Karoo, which is baking hot in summer and below freezing in winter, remain comfortable throughout the year because they were designed to make use of the direction of the sun’s rays.

We can learn a lot from previous generations.

Last Laugh

A policeman was chatting to a young woman in a bar. After he had introduced himself she asked him: “What do you do for a living?” “I’m a plain-clothes detective,” he told her. “She looked at his clothes and said: “What do mean ‘plain-clothes?’ You’re in full police uniform.”

“Yes. I know,” he said. “It’s my day off.”