Quote:
Originally Posted by NeilBlanchard
How do the vacuum tube system fare in comparison to the flat plate type?
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In the winter, its all about total surface area to capture the heat, whilst vac tubes have less losses than a flat collector, they don't have a lot of surface area so you will need lots of them. Also they are not DIY, so its better value to not use vac tubes when you can make your own large collector arrays relatively simply.
Snow build up on vac tubes can be a problem also, the gaps between the tubes allow the snow to grab a hold and because they are better insulated the snow doesn't melt and slide off as it would on a flat plate collector.
The typical heat pipe inside the vac tube doesn't start working until it gets to 40 degrees Celsius, this means under cloudy adverse conditions they are not as efficient as flat plate collectors, so will not harvest as much energy per unit area as a flat plat collector in these conditions, sales people will try and tell you otherwise.
Cheers
Mike