Solar heating systems

Heat storage on sunny days

Solar energy is available abundantly and cheaply. What's more, it's environmentally friendly. This energy can be used either to heat buildings or water, or to generate electricity.

The challenge facing solar heating is heat storage. Solar heating systems must have some way of storing the heat collected on sunny days. This heat may be stored either in a tank as a hot liquid (direct system in which the actual water to be used is heated and stored) or transferred through the heat exchanger in the hot water boiler.

For heating applications, a heat transfer fluid is pumped through a solar collector, where the fluid is heated up. The heat transfer fluid is then pumped either to areas where it delivers its heat to heat up rooms, or is sent through water storage tanks where it warms up water for domestic use. The fluids most commonly used are based on water and propylene glycol and ethylene glycol. When selecting a heat transfer fluid, the following criteria should be considered:

  • Base fluid choice
  • Coefficient of expansion
  • Viscosity
  • Thermal capacity
  • Freeze point
  • Boiling point
  • Flash point
  • Corrosivity
  • Stability

Examples of application areas:

  • Solar room heating:
    By using of mechanical equipment, such as pumps and blowers, houses are warmed up by means of solar energy. Usually an outside source of energy is also available to help heat the house when the amount of solar energy is not sufficient. The heat transfer fluid passes through the collectors and is heated up. Subsequently the hot heat transfer fluid is then transported to the rest of the building just as it would be with a conventional heating system.
  • Solar water heating:
    Heating water is a significant home energy expense. Using solar energy to provide hot domestic water will significantly reduce this expense. In a solar water system, a solar collector is mounted on the roof or in an area with direct sunlight. Solar energy is collected and converted into heat. A pump circulates a heat transfer fluid through the collector, where it is heated up. The hot fluid then flows to the water storage tank, where it heats up the water by transferring the solar heat carried by the heat transfer fluid to the water by means of a heat exchanger. Separate circuits are used to ensure the heat transfer fluid and the domestic water do not mix. The hot domestic water is then ready to use. In order to minimise heat loss, the distance from the collector to the water tank should be as short as possible.
  • Solar energy and the environment:
    In the 1970s, the push for renewable energy was driven by oil shortages and price increases. Today, the push for renewable energy sources is driven by renewed concern for the environment. Solar energy is the prototype of an environmentally friendly energy source. It consumes none of our precious energy sources, does not contribute to air, water or noise pollution and does not pose a health hazard. Solar energy does not leave harmful waste products in the environment. Solar energy cannot be embargoed or controlled by any nation, nor will it run out until the sun dies.

Recommended dosage:

  • 35-40% Zitrec© LC