Solar Thermal Evacuated Tubes
The evacuated tube systems have a 58mm tube instead of a 47mm and the length of the tubes are 1800mm instead of 1500mm. The new manifold is extruded aluminum and it is very hi tech.
The new tubes put out a lot more hot water because not only of their added diameter and length but because of their one piece heat sink that is inside the tube. The older system had segmented heat sinks but the new ones are all one piece. This allows the 30 tube system to produce about 40,000 BTUs on a sunny day. This is assuming the system is set up for facing south in the northern hemisphere.
The Evacuated Tubes Solar Heating System is a breakthrough in the efficiency of hot water production for residential and commercial uses. The tubes, similar to the inside of a thermos, are placed in the sun. Being round gives them maximum sun exposure at every sun angle during the day. Also, because of the vacuum chamber between the two walls of the tube, the tubes always remain cool to the touch even in bright sunlight and most importantly, the tubes can still produce hot water on cloudy days. They are very superior in performance in cold weather conditions. A flat plate collector would radiate a lot of the generated heat through the single panel glass. The Evacuated Tubes work with a vacuum so this doesn’t happen.
Evacuated tubes are extremely popular in other parts of the world and it is unfortunate that they are lagging in popularity in the United States because they work so well.
Sunlight heats the inner black tube which in turn heats the aluminum heat sinks that runs the length of the inner tube. A small copper tube is located in a slot in the aluminum heatsink.. Inside this tube is a small amount of glycol which changes to steam that goes up the tube end into the manifold where the glycol changes state from steam to a fluid state. This is called latent vaporization and it is this changing of state that gives the tubes the high efficiency that makes them produce about 40% more hot water than a flat plate collector.
After the heat pipe gets heated, it transfers its heat from the heat tube end into the water flowing through the aluminum manifold. It does this by conduction.
The Evacuated Hot Water System
This evacuated tube hot water system contains 22 glass tubes or 30 with the stretch version. There is also one extra tube and all the components including the manifold frame and component assembly necessary to put together the tube system. It does not include pumps, expansion tank or other accessories. We can provide all this necessary equipment but you would have to contact us to help you design a solar hot water system.
One of these 22-tube hot water systems usually provides enough hot water for an average family of four.
After the frame is attached to a roof, it is easy to slip each tube into its slot in the manifold while the bottom gets attached to the bottom rail. Hence there is no heavy lifting required as the tubes get installed one at a time. (Water must be flowing through the manifold when the tubes are installed.)
The evacuated tubes can be connected to a radiant floor heating system as the temperature output is perfect for Pex tubing. The tubes can also be used with some of the new Absorption Air Conditioners;; we think this is, without doubt, the future of air conditioners.
The tubes are made out of a glass similar to Pyrex (Borosilicate glass) and they are breakable but once they are installed on a roof they should give many years of service.
Federal Tax Credit
Domestic solar hot water or space heating systems are now eligible for a federal tax credit up to 30% of the system costs; there is no longer a maximum credit amount. The evacuated tube hot water system is qualified for the rebates requiring SRCC certification. The credit does not apply to heating for swimming pools or hot tubs.