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World premier of solar dryer

Using solar energy to heat air in a tumble dryer – this world first has now been introduced to the market by Miele. The T 8881 S EcoComfort is connected to a home's central heating system which, in turn, is linked to a solar-thermal rooftop array. This reduces the burden on the environment as a solar dryer with an A+++ energy efficiency rating is up to 80% more efficient. 

A solar dryer makes direct use of the sun's energy without first converting it into electricity. This requires a solar-thermal array which feeds hot water into a central heating system via a stratified storage tank. The first project study on this subject was jointly presented by Miele and Solvis, the solar-thermal specialist, at IFA 2011 in Berlin. Now, on completion of final R&D specifications and after exhaustive product testing, not least to Miele's 20-year life expectancy benchmark, the appliance is ready to go into series production.

As the solar dryer requires considerably less primary energy, energy costs compared with a highly efficient heat-pump dryer have been reduced by a further 60% (or by 80% compared with a vented or condenser dryer). Given normal usage in a family of four, the added costs of this machine (around € 500) are capitalised within just over 7 years. Practical: during the summer, the solar dryer helps utilise the hot water produced by a rooftop array to the full; in winter, the water in the stratified storage tank can be alternatively heated using bio-mas or geo-thermal heat.

The solar dryer is connected to the storage tank via four lines. The first transports hot water to the dryer, where heat transfer to process air takes place in a heat exchanger. In the process, the water cools down and is returned to the storage tank via a second line. A third connection pipes cooler water from the storage tank into the dryer in order to cool down the warmer air returning from the dryer. The moist air is then cooled down in a second heat exchanger to condense out moisture. This is then piped back to the tank along a fourth line. Thanks to this closed circuit, temperature losses are negligible as, for the most part, the heat extracted for drying laundry is re-introduced to the storage tank in the condensation process.

In terms of drying results, the solar dryer is comparable to its more conventional counterparts. The low process air temperature is similar to that on a heat-pump dryer, resulting in extremely gentle care of textiles being taken. The use of solar-heated water is also possible on other Miele domestic appliances such as dishwashers and (AllWater) washing machines.