Does the Water in Solar Thermal Systems Need to Be Replaced?

Photo credit: Snap

Along with photovoltaics, solar thermal hot water heaters are growing more fashionable and marketable every year. Solar hot water heaters are more expensive than conventional models, although energy savings over time and increasing federal and state financial incentives narrow that gap considerably. After your new solar water heater is installed there is typically very little maintenance required — a big selling point for manufacturers and installers.

Very little, however, does not mean zero maintenance — just very rare maintenance. For active systems, pumps and other electrical components may need repair or replacement, but usually not for at least 10 years (quality solar thermal systems come with at least a 10-year warranty).

Yet another good maintenance question comes in regard to the water or fluid flowing through the system and/or solar thermal collectors.

Water

The water in solar thermal systems rarely needs to be replaced, even for systems with a storage tank. According to the federal government, the average person uses 15-20 gallons of water per day. That is why the average family of four’s water tank will be about 80 gallons in size. Remember that reducing your water usage will save even more money and reduce the size of your system, saving on initial costs as well.

Because the system is sized to provide enough water for daily use, the water within the system is not allowed to grow stagnant — the only real reason why the water would need to be replaced. Speak with your solar thermal installer about any further considerations that may arise based on your location, lifestyle, and type of system.

Transfer Fluid

For indirect, closed-loop systems — most common in climates with periods of freezing temperatures — an anti-freeze or propylene glycol solution is run through the collectors. This fluid will not freeze, thus making the solar water heater usable year round. The heat collected by the anti-freeze solution is transferred to usable water in a storage container by a heat exchanger. The transfer fluid will have to be replaced every 3-5 years on average and should be tested at regular intervals.

Posted on June 5th in Solar Thermal by Dan.