If you’re interested in getting solar thermal panels for a hot water system for your home, one of the decisions you’re going to have to make is whether you want to get evacuated-tube solar thermal panels, or flat-panels. There are a few thing that you have to consider in this regard, but on the whole the evacuated-tubes are going to be better.
One of the most important factors when it comes to which kind of solar collector is better is efficiency. That is, how much of the solar energy collected actually gets converted to useful heat energy for your water. And in that, the evacuated-tubes win.
The reason is that it is simply a better design. With a flat-panel you have the collector plate running across the bottom and transferring the heat up to the water that is running through it. With the evacuated-tubes though, the collector plate is running all the way around the inside of the tubes. This gives it a larger surface area, so there is more heating opportunity. Also, it means that whatever angle the sun is shining at, there are going to be portions of the collector plate which are getting the full effect. With flat-panels, at certain angles there are going to be parts of the collector plate which are in shade.
The “evacuated” part of the tube also helps with efficiency because it prevents the heat captured from escaping, and it also stops the cold weather from decreasing the level of heat within the tubes.
It also tends to be that using evacuated-tubes is the more reliable method of collecting solar energy to heat the water for your home. Really though this comes down to whether it is a direct or indirect system, it’s just that the indirect system tends to be used more with the evacuated-tubes. The reason that is better is that the water is not going to the panels directly, which has a couple of advantages.
First of all it means that you are not going to get any deposits from the water building up over time and causing blockages down the line. Instead, a heat-transfer substance is used, which just circulates around the panel, heating and cooling, transferring the heat to the water. This is also a better way of doing it because it means that if the system stagnates for any reason, you are not going to have the trouble of trying to get the water out of your solar panels.
The only aspect where the flat-panels are better is in terms of cost. They don’t cost as much as evacuated-tubes, so if your budget is tight then it is worth considering them then. They are certainly not a bad option, they are simply not as good at utilizing solar energy as the evacuated-tubes are.
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