Solar Thermal

Wood Pellet BoilersWhat it is:

Solar thermal is using the energy of the sun for heating purposes, either for hot water, for space heating, or both. In the case of solar thermal, solar energy is captured by either flat panels or evacuated tubes, and transferred via fluid to a holding tank where it is stored until needed.

Past, present, future

People have heated water and living space with solar thermal techniques for thousands of years. After being largely ignored in more recent history, solar thermal is now gaining popular acceptance around the world because it’s an efficient, clean heating solution with a reasonable payback on investment. Solar thermal is most commonly used for making hot water for washing, bathing, etc. Modern solar thermal technology also makes it possible to be used as a supplemental source of space heat, even in northern climates such as in the northeastern US. In fact, even in temperate EU countries with less solar potential than we have here in New England, solar thermal is becoming a mandatory component of heating systems in new buildings.

Solar thermal systems are the most efficient way to actively capture the sun's energy. That is, more of the energy that reaches the thermal collector becomes usable energy, than is the case with PV panels. Efficiencies of greater than 50% are possible with solar thermal vs. closer to 10% for PVs. These systems are also reliable, having matured greatly over the past 30 years. Solar thermal systems also require a lower outlay of capital than is the case for other solar energy systems, such as photovoltaics.

In the realm of solar thermal, there are choices to be made about the type of collector (glazed flat plate, evacuated tube, etc.), the circulation method (natural vs. forced), the method of heat exchange, size of holding tank, and more. The answers depend on location, expected use, and budget.

For the heating of hot water, it’s not unusual to have solar thermal systems provide the majority of hot water by solar, particularly in the months from spring to fall.

In the case of space heat, the suns radiant energy is transformed into thermal energy which is captured and transferred to an insulated water tank. The solar-heated water is subsequently boosted in temperature when necessary by means of a boiler. That boiler can be a traditional fossil fuel powered boiler, or one powered by some other fuel, such as biomass. Combined solar thermal and boiler systems gain efficiency over boiler systems alone because a portion of the heat energy provided by the system comes from the sun.

Advantages:

  • Non-polluting.
  • Costs made reasonable with incentives.
  • Long-lasting.
  • No maintenance.
  • The same system can be used for heating hot water and supplementary space heating.

Disadvantages:

  • Used only as a supplemental system in the northeast, so must be tied in with a primary heat source.
  • Not appropriate for shaded or north-facing roofs.

Ecological Impacts:

No adverse impacts.

Interested in getting more information on solar thermal heating systems? Simply fill out our short online request form and we can help with design an EcoHeat solution that's right for you.

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EcoHeat Quick Fact:

Life cycle costing and cash flow analysis demonstrate a clear long term benefit of solar thermal over electric and natural gas-fired hot water systems.