solar thermal 101

What is a Solar Thermal System?

A solar thermal system differentiates itself from a solar power system in that it does not produce electricity. Generally speaking it produces heat, and with improving technologies it can also remove heat from a space. The inner workings of a solar thermal system are fairly simple; heat from the sun, in the form of solar radiation, is trapped, and then transferred into air and/or water.

Solar water heaters have three main components: a solar collector, insulated piping, and a hot water tank. The solar collector transfers the sun’s heat into potable water, the insulated pipes carry the hot water to the tank where it is held until it is needed. When the water is ready to be used, the pipes carry the water to that location, whether it is the kitchen sink or the shower.


Solar space heaters utilize similar components as solar water heaters. The solar collectors and insulated pipes are used to heat water. At this point either an Air Distribution System or a Hydronic System with Radiator can be used. In the former, heated water is pumped through a coil surrounded by air. The heat is transferred from the water to the air, which is then distributed throughout the house like a normal  HVAC system. In the latter, the heated water itself is circulated through the home. Radiators in each room, connected by insulated piping, are used to heat the interior spaces.

In both cases of a solar water and a space heater, an auxiliary system is necessary for times when the sun is not providing a sufficient amount of solar radiation. It is important to note that the more efficient your system, the less often you will need to use your backup system. And because solar thermal units are typically more efficient than electric units, when you do need to use your backup system, you will still use less energy.

Efficiency for air conditioners and heat pumps can be measured by both the Energy Efficiency Ratio (EER) and the Seasonal Energy Efficiency Ratio (SEER). EER measures efficiency at a single point in time, comparing output of heating/cooling energy to input of solar energy. SEER measures efficiency over the duration of a period of time (during the cold or hot season). For perspective, Energy Star EER ratings for air conditioners start at 9.2 and SEER rating start at 14.

 SEER savings

Why should you get a solar water and space heater?

The economic benefits of utilizing solar thermal energy are extensive. On average 60% of a home’s energy needs come from water and space heating. If you can get all of your water and space heating needs from solar, you will see a 60% reduction in your utility bills.


Even if you only see a 50% reduction, the savings mean that your solar system will be more than worth the cost. In fact, the return on investment for solar thermal systems can be as short as three to six years. Water heaters can provide 40-80% of home hot water needs, meaning that, depending on the efficiency and size of the system, your utility bill for hot water will be reduced at least 40% alone.

Yet another economic perk of a solar thermal system is the federal tax credit that runs through December of 2016. Any taxpayer can get a 30% rebate on their property taxes. For more information visit this link.

Subtler savings come from the consistent inexpensiveness of operating a solar thermal system. The lifespan of a solar thermal systems is at least 30 years and requires little to almost no money for maintenance. Maintenance is necessary only once every three to five years and consists merely of a visual examination of the components and checking the fluids. This means that for the duration of the systems life, it and your property will become more valuable as the cost of non-renewable forms of energy increases.

Like solar power systems, solar thermal systems have environmental benefits comparable if not better than the economic benefits. Production costs can account for a significant percentage of the carbon-emissions that go into making a product. When compared to water and space heaters that run on non-renewable forms of energy, solar water and space heaters have a considerably longer lifespan. This means that fewer materials will need to be used to produce the components for the solar systems in the coming decades. In addition, parts of solar thermal systems are more likely to be manufactured, distributed, and sold locally, reducing carbon emissions resulting from transportation.

Of course carbon emissions are also reduced directly by the systems themselves. A 50 gallon collector solar hot water system can offset over 50 tons of CO2 per year, or 5,000 tons over the life of the system SunWaterSolar. This is equivalent to removing eight cars from the road every year. A 80 gallon solar thermal hot water system will offset 120 tons of CO2 over its lifetime MSEIA. This is the same as removing 36, 100-watt light bulbs from use every year.

 energy used from space heating and cooling

What makes a solar thermal system efficient?

When looking at the ideal performance and efficiency of your solar system, there are a number of variables that should be considered. The orientation of your roof, for example, should be south facing in order to maximize the amount of sunlight captured throughout the day, (Pure Energies) and the pitch (tilt) of your roof should also be considered, as the degree of the pitch will affect the amount of sunlight received. Temperature and shading also affect the efficiency of solar energy production. Panels ideally should be installed a few inches above the roof so that the airflow may prevent overheating, and shading should be avoided as much as possible, as it may cause energy production to suffer or even shut down.  (Pure Energies) Because the average solar panel converts 11-15% of sunlight into energy, it is essential to have optimal efficiency in your own panels. (Pure Energies) The higher the efficiency, the fewer solar panels needed to produce the same amount of solar energy.


Additional Resources

LEAP: Solar Power 101

LEAP: Get Started with Solar Power

LEAP: Get Started with Solar Thermal

Solarzie Charlottesville