In the large market of solar water heater systems, there are a diverse arrange of ways solar water heater systems keep their heat. One of these is by using a heat transfer fluid.
Heat-transfer fluid operates very similarly to anti-freeze in your car. They carry heat through solar collectors and a heat exchanger to the heat storage tanks (FYI none of these are needed for your heat streamer solar water heater kit) in solar water heating systems. In a cold climate, solar water heater systems require fluids with low freezing points, whilst in a desert climate they should have a high boiling point. Their viscosity must also be taken into account, as the resistance of liquid effects how heat will be transferred. Common types of heat-transfer fluids that we at Clean Republic are asked about are:
"Air - Air doesn't freeze or boil, and is non-corrosive. It has a low heat capacity, and tends to leak out of solar water heater systems.
Water - Water is nontoxic and inexpensive, with a high specific heat and very low viscosity: it's easy to pump. It has a low boiling point and a high freezing point, and can be corrosive if the pH is not maintained.
Glycol/Water Mixtures - Clean Republic is mostly asked about this one. Glycol/water mixtures have a 50/50 or 60/40 glycol-to-water ratio. Ethylene and propylene glycol are "antifreezes." These mixtures provide effective freeze protection as long as the proper antifreeze concentration is maintained, and they should be changed every 3-5 years."
So, does our solar water heater need a transfer fluid? No. The Heat Streamer solar water heater kit is a passive solar water collector, meaning the infrared rays of the sun heat the tubes that heat the water. Therefore, heat transfer fluid is not necessary. This also cuts down on set-up and potential damage to the environment. So buy your solar water heater it today!
Quoted text pulled from energy.gov