Solar Domestic Hot Water preparation (SDHW)
Solar Domestic Hot Water systems (SDHW) are dominating the markets in warmer climates. Around the Mediterranean, as well as in China, SDHW are already installed in vast quantities. Small systems are available for individual dwellings and larger (collective) systems provide hot water for multi-family houses, hotels, office buildings etc. This page introduces the most common SDHW types.
Hot water preparation is still by far the major solar thermal application in Europe. Solar Domestic Hot Water systems (SDHW) are specifically designed to deliver 100% of the hot water requirements in summer and 40-80% of the total annual hot water demand. They include a supplementary heater (e.g. an integrated electric or gas heater). Or they are operated as pre-heaters.
These systems are particularly popular in regions with no or low space heating demand. In Spain and other countries, solar hot water systems are now mandatory in new buildings www.solarordinances.eu.
Combi Systems and Combi+ Systems are gaining market share where space heating or space cooling is required in addition to domestic hot water. These systems are larger and save more energy
SDHW for one or two dwellings
Two different design principles: Thermosiphons and Forced-Circulation systems
Thermosiphons and Forced-Circulation are the two main SDHW systems. What differentiates them is how the water is circulated between the collector and the tank.
Collective SDHW for larger buildings
Central water (and space) heating is common in larger buildings. Increasingly, collective solar domestic hot water systems are being installed into multi-family houses, hotels, office buildings etc. These collective systems have a collector surface ranging from ten to several hundred square metres. Larger SDHW are designed specifically for lower solar input, i.e. they provide a smaller share of the hot water demand with solar energy. This and the fact that they are often operated at lower temperatures results in a high system performance (thermal energy output per square metre of collector area). Most collective SDHW systems are designed as forced-circulation systems, but multiple thermosiphon systems are also used where appropriate.
Further information about collective solar thermal DHW can be found on the SOLARGE project's website.