SIEMENS

The grayish granules feel like a handful of puffed rice. Blow a breath of moist air over them, however, and they quickly become painfully hot. “That’s adsorption heat,” says Michael Rosenbauer, Head of Dishwasher Development at BSH Bosch und Siemens Hausgeräte (home appliances) in Dillingen, Germany. This heat is generated when the microporous granules trap water molecules in their tiny pores. The unusual material they are made of is an aluminum silicate zeolite that is easily recycled. When placed in a container on the floor of one of BSH’s latest generation of dishwashers with “speed- Matic” functionality, 1.15 kilograms of these granules adsorb the moisture from drying dishes. A demonstration dishwasher in the BSH lab in Dillingen shows just how rapidly this occurs. Operating in a continuous cycle, the machine wets dishes and then dries them in just two minutes. Even damp patches at the bottom of cups or the drops that always stick to plastic containers evaporate in seconds due to the warm air generated by the heat from the zeolite granules.

Rosenbauer says that the original idea came during a presentation at the Bavarian Center for Applied Energy Research (ZAE) in Garching, near Munich. This nonprofit association, which is funded by collaborations between industry and higher education, had organized a demonstration for developers from all of BSH’s product groups. All in all, this spawned 39 ideas, but the Dillingen team was the first to come up with a product. In 2008, 250 pilot-production dishwashers were sent to testers in many locations, without any reference to the special functionality. “The response was immediate. People were amazed by how dry the dishes were,” Rosenbauer recalls.

Energy Recycling. At present, no other manufacturer anywhere has anything to rival the zeolite system - and that is unlikely to change for the time being. BSH has filed some 30 patents, ZAE has supported the research, and engineers in Dillingen have protected both the idea of zeolite drying and its implementation.

The system consists of the zeolite container and a heating mechanism. A fan blows damp air over the zeolite granules and hot, dry air back into the dishwasher chamber. This reduces moisture content from 100 to 10 percent. In the process, the granules retain up to 200 grams of water - enough to remove every last drop from the dishes. To remove the water, heating coils then heat the zeolite to a temperature of 240 ° Celsius.

Although this process consumes energy, speedMatic dishwashers use around 20 percent less electricity as compared with conventional models from the highest energyefficiency category according to German consumer watchdog “Stiftung Warentest.” Because water that has been adsorbed is not driven out of the zeolite granules until the next washing cycle, the hot, damp air thus generated can be used to moisten and warm dirty dishes. Part of the heat energy consumed for this purpose is later recouped and used for the drying process - in the form of energy released when water molecules are adsorbed in the tiny pores of the granules. At the same time, the machine’s low water consumption - 10 instead of 14 liters per cycle - sets a new record. In recognition of this innovative development, BSH developers have been presented with the Climate and Environment Innovation Award from Germany’s Environment Minister.

The speedMatic innovation also offers environmental benefits. If all German households with dishwashers rated at over 1.3 kilowatthours (kWh) per cycle were replaced by 0.83 kWh speedMatic models, CO₂ emissions would fall by 1.2 million metric tons a year.

A life cycle assessment by BSH indicates that although production of the new dishwashers requires four to six percent more energy than for older models, the environmental impact of such factors is negligible because a zeolite dishwasher uses one-fifth less energy during its operating life, which is responsible for 95 percent of its environmental impact. Consumers benefit too. At an electricity price of 0.19 Euros per kWh, the additional cost of purchase can be recouped within an average service lifetime of 13 years - or even earlier if power prices continue to rise.