Solar Power for Hot Water and Heating

The Sun supplies us with an enormous daily energy potential that exceeds primary energy consumption, by 80 times in Germany, for example. This energy source is virtually inexhaustible and is also at our disposal for the next million years. Fossil fuels such as coal, natural gas, or oil are, in contrast, limited. The next generations will not be able to use them without restriction, so the sun presents itself without a doubt as the energy of the future.

Solar Water Heating

The use of solar energy to heat water results in favorable basic requirements, since a household's warm water use is roughly constant throughout the year. Thus, there is a larger conformity between demand and the solar energy supply, than with the utilization for heating.

Percent of monthly solar coverage

Solar heating systems for hot water distinguish themselves with simple system technology which is, however, technologically sophisticated. In the meantime, there are a large number of solar companies, which have many years of experience in system planning and mounting. They offer a wide palette of system concepts for a variety of needs.

How does a solar heating system work?

The heart of a solar heating system is the collector. A flat-plate solar collector, the most prevalent collector form, is made up of a selectively layered absorber that serves to absorb the incoming solar radiation and transforms it into heat. This absorber is embedded in a thermally insulated box with a transparent cover (usually glass) to minimize thermal loss.

A heat conducting liquid (usually a mixture of water and non-environmentally damaging anti-freeze) flows through the absorber and circulates between the collector and the warm water storage tank. Thermal solar energy systems will be brought into operation through a solar automatic controller. As soon as the temperature on the collector exceeds the temperature in the storage tank by a few degrees, the regulator switches on the solar circulation pump and the heat conducting liquid transports the heat received from the collector to the storage tank.

Elements of a solar heating system for hot water:

  • Automatic solar controller
  • Temperature sensor on collector
  • Temperature sensor on storage tank
  • Solar circulation pump
  • Cold water inflow
  • Hot water run-off
  • Expansion tank
  • Temperature sensor for additional heating
  • Charging circuit- solar circulation pump

The conventional heater guarantees, with the charging circuit, that enough warm water will be available even when the solar heating system supplies little or no heat at all. Solar heating systems can be integrated into buildings without a problem. Thus, a modern solar heating system, with at least twenty years life expectancy exceeds that of a boiler, and ideally supplements conventional heating technology.

Active environmental protection

CO² emissions from heating systems producing

With the installation of a thermal solar heating system, one is actively contributing to the lowering of environmentally harmful CO² emissions. A solar heating system has an unequivocally positive CO² balance compared to conventional water heating systems.

To avoid excessive CO² emissions, you should see to it that no electric heating systems come into operation. In contrast, the use of a solar heating system combined with efficient energy technology (a modern condensing boiler) with the lowest possible energy consumption is environmentally ideal.

The period of energetic amortization (the time until the solar heating system has produced as much energy as was needed to manufacture the system) on a thermal solar heating system is between half a year and two and a half years. In comparison to that, conventional systems never pay back energetically. In order to make a certain amount of energy available, they need an even larger amount of primary energy.


Aren't solar heating systems too expensive?

The argument often put forward against the use of solar heating systems is that they are not economical. This often culminates in a flat out rejection of renewable energy. But have you ever asked yourself if the new aluminum wheel rims on your car are economical? Or if the old oil central heating boiler from the 70s still works economically? Other than that, you cannot forget that solar heating systems provide an important contribution to the use of environmentally friendly energy.

The inexpensive prices for conventional energy sources conceal the real facts. The consequential costs for environmental and health damages caused by their use (the so-called "external costs") are not included in their price and have to be payed for by the general public. You also have to consider, that the price for conventional energy sources will increase considerably in the near future, due to these resources running short.

The sun, however, supplies its energy free of charge. The relatively high initial investment at first sight suggests that the systems are, in general, very expensive. But from the time of installation of the system on, there are no more operating costs, except very low costs for maintenance and pump electricity. Whoever invests in a solar heating system is also investing in the future. Other than that, there is the possibility to lower the costs of a solar heating system by claiming state or community funding. Since 1996, homeowners in Germany can make use of an environmental bonus eight years long: up to 500 marks per year for a solar heating system.

The German Section of the International Solar Energy Society (ISES) would be pleased to answer any further questions on funding possibilities.

Text and illustrations used with permission from the German Section of the International Solar Energy Society (ISES)

Concise and comprehensible explanations of the basic concepts in solar heating and photovoltaics can be found in our Solar-Lexicon.

Reports on technology, business and politics, as well as presentations on innovative systems and products can be found in the Solar Magazine