At last year's IFA electronics trade show, Miele unveiled its SmartGrid-ready washer and dryer. Although they run off of regular mains power, these machines are also able to access the internet and determine when rates will be cheapest. Users indicate the time period in which the laundry must be washed or dried, the appliances choose the least expensive time within that period, then proceed to automatically start at that time. At IFA 2011, Miele has gone one better by unveiling what it describes as the world's first dryer to use the heat of the sun to get the wetness out of clothes.

The dryer, developed in a partnership with solar tech company Solvis, utilizes heat gathered by rooftop solar-thermal collectors. A freeze-protected fluid in those collectors transfers the sun's heat to water in a stratified storage tank designed by Solvis by heat exchange. The water lies in different temperature layers within the tank, which will soon come into play.

Four pipes connect the tank to the dryer. The first one brings hot water to the dryer, where it heats the air in the tumbler via a heat exchanger. The then-cooled water proceeds back to the tank through the second pipe, where it can once again be heated. In order to extract the clothes' moisture from the inside of the dryer, a cold internal surface is provided to cause condensation. That surface is cooled with cold water, brought in through the third pipe. The fourth pipe is used to return that same water to the tank, once it has started to warm up.

In winter or when the sun isn't shining, the tank can be heated by other energy sources. When the dryer isn't running, hot water from the tank can also be routed to the washer or other appliances.

The whole closed system is reportedly almost loss-free, as the heat taken from the tank to warm the air is largely recouped when the cold water is heated in the condensation process. The machine is said to have half the operating costs of a heat pump dryer, and up to 80 percent less than standard vented or condenser dryers. It is also claimed to offer laundry-drying performance similar to that of conventional machines.

Miele says that its solar-heated tumble dryer should be on the market by the fall (northern hemisphere) of 2012.

The company also took the opportunity to announce an addition to its existing SmartGrid-ready technology. Besides being able to determine when electricity rates are lowest, it can also now estimate when a roof-mounted photovoltaic array will be able to generate enough electricity to run a given combination of appliances.

As with the previous example, users would indicate a time period in which - for instance - their dishwasher and clothes washer needed to run. An energy management system would then check the internet, to see at which point within that period there would be the most solar yield. It would relay that information to the Miele gateway system, which would estimate how much electricity would be required to run the two appliances.

Between the two systems, a schedule would be worked out wherein both machines would have enough electricity to run (presumably one after the other), and still finish by the user-set deadline. If the weather forecast proved inaccurate and there wasn't enough sunlight, the appliances would complete their schedule using electricity from the municipal grid.

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