Solar Pool Collectors
Solar pool heaters are designed to use minimal cost materials - unglazed polymer is the choice - as ambient temperatures are normally higher during pool use.
With the amount of temperature increase generally between 10 and 20 degrees of ambient, and the desired temperature of a pool in the mid 80 degree range, an uninsulated unglazed polymer heater can obtain the desired pool temperature easily at the lowest cost per British Thermal Unit (there are many variables, such as multiple sun days, or multiple cloudy days, that can exaggarate these temperatures).
Let us review: Should pool water and the outside morning temperature be 70 degrees, with sunshine through-out the day, a pool solar heater can increase the temperature of the pool water to a desirable 85 degrees - a 15 degree temperature increase.
The sizing of pool heaters rule of thumb is 1 square foot of collector to 1 square foot of pool surface area. Windage, shading, location and direction of the collectors are all factors that could effect this rule of thumb. A Solar Site Assessment is required to have an accurate measurement.
Evacuated Tube
Evacuated tubes are designed for upper end temperature increases and are designed to operate most efficiently at 125 (and higher) degree temperature difference. These are best used in an industrial process where higher temperatures are required. The reason they can accomplish such high temperatures is their efficiency and minimal heat loss capability.
Let us review: An industrial process needs to increase 75 degree return water to 210 degrees - a 135 degree temperature increase. Evacuated tubes operate very well in this temperature range and are the most efficient solar water heating device that can accomplish this task. At the higher end temperatures, evacuated tubes become the highest value/lowest cost per British Thermal Unit solar heating device.
It should be noted, the higher cost, increased maintainance, and a lessor life span will cause this type of solar heating device to have higher life cycle cost, or higher cost per British Thermal Unit produced over its lifespan, than a flat plat collector in a solar domestic water heating situation. Why a cooler system is a happy system.
Flat Plate Solar Collectors
Flat plate is best used in mid-temperature range increases, such as a residential domestic water applications. It's best operating capabilities are increasing water temperatures between 25 and 125 degrees of ambient.
The flat plate's main advantage are in they emit excess heat through the glass. This may not seem as an advantage during winter, but the heat being emitted will slick up the surface glass enough to allow the snow to slide off, thus cleaning the surface to allow sunlight to heat the collectors. This may not happen with the higher efficiency evacuated tubes.
The heat loss also is beneficial in the summertime when a large temperature increase is not needed. In the case of a solar domestic water heater - during multiple sun days, and lower than normal hot water use - the starting daily temperature of the potable water in the solar storage tank may be over 100 degrees. Sized right, the flat plate will begin losing measurable heat in the 180 degree range and overheating of the solar fluid is averted.
Let us review: A 2 occupant home having a single 4' by 10' solar thermal collector - with a matching 45 gallon solar storage tank - will have a normal morning solar storage tank starting water temperature of 75 degrees (residue heat from the day prior). On a full sun day, the flat plate solar collector can increase the temperature from 75 degrees to 150 degrees in the solar storage tank - a 75 degree temperature increase.
150 degrees is a far higher temperature than the necessary 120 degree temperature normally associated with a hot water heater, but not so high as to cause boiling water flowing from your taps and/or overheating of the solar fluid.
How a Solar Domestic Water Heater Operates
The frigid cold water intended to flow into your water heater will be diverted to the solar storage tank. Through a heat exchanger, your water in this tank is preheated by the sun. This water can reach temperatures of 150 degrees. When you pull water from your water heater, this 150 degree water in the solar storage tank will flow to your water heater. Of course, your water heater will now not have to burn fuel for heating.
Since the solar heated water could be a much higher temperature - that could cause scalding - we install a *thermostatic mixing valve after your water heater.
*It is mandatory that a "cold water" thermostatic mixing valve be installed after your water heater - to cool the water flowing to your faucets - to lower than 125 degrees (adjustable). We got you covered!
GreenSky will install all types of solar heating devices. Contact Us.