One of my co-workers saw a video on YouTube about a popcan hot air heater so he decided to make one himself. It worked so well that he decided to make a video of it. Then the local media caught wind and thought they could make a story of it. This video is the result of condensing 90 min. of videotape into a new clip. He spent $500 to make it but should make that back in a few years. A large part of the cost was the plate glass. It would have been more effective except for the fact that the garage next door blocks part of the exposure to the sun. Next project is a solar water preheat for the house.

http://regina.ctvnews.ca/video?clipId=840775

PS today, we are digging out of another 20cm of snow and -30* temps.

Darn, the CTV piece wouldn't play on my laptop. Probably my paranoid security settings.

But I looked up the YouTube versions. There are all sorts of variations on thermal walls, using glass, sunlight, and natural convection to direct heat into an interior space.

I was planning one to ensure ventilation in an outhouse, using scrap wood that had been well-charred on the surface and a glass door I got at the dump.

My single-paned, south-facing sunroom is a good example of how much heat the winter sun still has. It can be -20C outside, but if it gets full sun for a couple of hours I can have lunch out there with only a sweater on. But when I lose direct sun, the temp drops like a stone.

So, the challenge I guess is keeping the heat after you gain it. When the sun goes down, a thermal wall setup will work in reverse unless you stop the air flow.

As for the solar water preheat, it's a great idea as long as it goes through a temperature controlled regular heater before use. Otherwise there's a legionella risk, which can be nasty.

Doug, could you explain about the Legionella risk in the preheat please?

I'm no authority, but as I understand it, Legionella bacteria can thrive and build up in water heating systems. Inhaled via fine droplets, or spread through ventilation systems, it can cause serious illness. The critical thing is that the water is always heated to a minimum temperature before it reaches taps and showers.

Legionella is nothing to trifle with. There was a stubborn outbreak in Montreal, Canada last year. Twelve people died.

Google will provide oodles of information, as will local health/safety code authorities. A couple of links for starters:

http://www.osha.gov/dts/osta/otm/legionnaires/hotwater.html

http://www.wras.co.uk/Preheated-Water.htm

I hadn't even thought of Legionella, but that's true, keeping moderately warm water around can create the perfect environment for bacteria to thrive.

From the first link Doug references above:


So, even if your system has a boiler, the water may not be safe because the water is not heated high enough or long enough by the boiler to kill off Legionella before it is sent to your taps and shower.

Pardon me,

Some people live in areas where water is in the range of 20-45 (naturally) before it goes in the heater. Me included. Actually in the summer some folks install water coolers to their main water tanks !!

Despite the temp, we have not heard of this bacteria.
So, do you think that other factors maybe involved, like water salinity ..etc. (maybe IN ADDITION to the temp) ?

p.s.
I live in the Middle East, and our feed water is on the salty side : around 2000-4000 TDS

Legionella is a freshwater bacterium, so it's possible that your water is naturally too salty for optimum reproduction. It's hard to say. There are a lot of different factors in any case of disease transmission

There was even a study in the UK that pointed to the windshield wiper fluid tank in vehicles being the source of infections in the drivers, mostly people who drove for a living. In those cases, plain water was used, instead of wiper fluid. The bacteria grew in the tanks and became aerosolized whenever the drivers sprayed fluid onto their windshields.

Wouldn't surprise me a bit. It's just an aquatic bacteria that thrives in warm water. I would speculate that a system that has a fairly high and constant flow-through wouldn't provide a very good incubating medium. On the other hand, if nice warm water sits and the bug happens to be in there, it may thrive.

To my mind, the public health and safety code rule for "adequate time at adequate temperature" is probably the easiest and most reliable way to manage this bug on a large scale.

My only reason for mentioning it is that a home-made pre-heater should take this into account, both in design and operation.