SIEMENS

The number-one manufacturer of home appliances in Western Europe, Bosch und Siemens Hausgeräte GmbH (BSH) of Munich, Germany is committed to minimizing the environmental impact of its products. "Before we develop any new household appliance, we always conduct a thorough analysis of its potential impact," says Dr. Arno Ruminy of the BSH Environmental Protection department. In fact, a strict internal guideline stipulates that all washing machines, refrigerators, and dryers must have a minimal impact on the environment in all phases of their life cycles. Before the development process even begins, each product idea is carefully examined in order to identify the most environmentally-compatible and recycle-friendly materials, determine the areas where material savings can be achieved, and produce a design that allows the easy replacement of used parts. "Every new device must be better than its predecessor in terms of environmental protection," says Ruminy.

By designing energy efficient appliances, BSH is also meeting the needs of its customers. That's because appliances still account for around 40 % of total energy consumption in private households — despite the efficiency gains achieved with refrigerators and such over the last ten years. Life cycle studies carried out by BSH environmental experts also show that such appliances mainly impact the environment through electricity and water consumption when they're being used. "Transport and recycling play only a minor role, and resource consumption in production accounts for only a small percentage of the total resources used. In contrast, operation is responsible for more than 90 % of the overall environmental impact of most appliances," says Ruminy. In the case of dryers, this figure is as high as 97 %. "Making things more efficient here will benefit the environment and save consumers money," Ruminy says.

Heat Pump Strategy. Back in August 2006, BSH engineer Kai Nitschmann was given the assignment to develop a clothes dryer equipped with heat-pump technology that would outperform all other dryers on the market in terms of energy efficiency. The first thing Nitschmann and his colleagues did was to define target values. "We were looking to achieve energy consumption of 2.1 kWh for 7 kg of laundry, which was just slightly above the world record at that time," Nitschmann recalls.

His development team at BSH's Berlin plant started out by disassembling all types of dryers, counting their nuts and bolts, and weighing their plastic parts. They also measured the dryers' energy consumption and loudness. Their analysis resulted in the conclusion that the only way to achieve their ambitious energy efficiency goals was to use a heat pump — a technology that had never before been used in a dryer. "A heat pump prevents the energy contained in the vapor and hot air from escaping from the dryer," says Nitschmann.

The results of the team's efforts are preserved in a glass case in Nitschmann's office. There are, for example, copper arteries through which a coolant flows. Circulation is maintained by a powerful electric motor whose output is four times that of the motor that turns the dryer drum. A compressor pumps the condensed and thus heated coolant into the copper pipes, which repeatedly twist through two aluminum frames. The first of these frames is a heating unit in which the coolant transfers the heat it contains to the circulating air. This heated air then flows into the dryer drum, where it absorbs moisture.

A second aluminum frame works as a cooler. When hot, humid air returns from the drum, it comes into contact with this frame, which has been cooled down by the cooled coolant. Moisture condenses as the air cools, and the heat obtained from the air is then transferred back into the coolant. "The energy in the hot dryer air and in the vapor is temporarily stored in the coolant and then used for heating purposes," Nitschmann explains.

Ruminy points out that the coolant, which is known as R407c, conducts heat very effectively, which significantly reduces energy consumption. Unfortunately, however, it is also a greenhouse gas, which is why BSH commissioned the Institute for Applied Ecology in Freiburg, Germany to determine whether the heat pump approach made sense. As Ruminy explains, the institute established that "the lower energy consumption by far offsets the greenhouse gas potential involved." The Freiburg experts did, however, emphasize the importance of effective recycling. Specifically, steps would have to be taken to ensure that the dryer's coolant, like that of a refrigerator, would be disposed of properly and not released into the environment at the end of the machine's service life.

Meanwhile, developers in Berlin were faced with the challenge of incorporating heat-pump technology into a dryer for the first time, since up until that point they had been used only in refrigerators, air conditioners and heating units. "If it hadn't been for our Spanish colleagues' experience with air conditioners, we wouldn't have succeeded so quickly," says Nitschmann. The team in Berlin also had to integrate a second new technology for optimizing efficiency: an innovative lint cleaner for the condenser.