German inventors have an ingenious way of keeping your hot drink stay in ‘perfect temperature’ – warmth enough time till you finish it.
Klaus Sedlbauer, the head of the Fraunhofer Institute for Building Physics (IBP), and his colleague Herbert Sinnesbichler, used ‘phase change materials’ (PCM) of the sort found in the construction industry to keep rooms cool in summertime.
The material is usually embedded within plaster boards or placed on walls and ceilings to absorb and store warmth and releases it after the sun has gone down. It is the same technology uses in making ski-jackets.
Thank to Klaus and his colleague, now it has found a new life in the IBP mug. The high-tech mug is made using a porcelain shell with a hollow interior filled with a honeycomb structure made of ribbons of highly conductive material, such as aluminium.
This honeycomb structure is then filled with PCM.
‘So now, if you are drinking hot tea in one of these cups,’ Sinnesbichler told Germany’s Der Spiegel magazine, ‘the drink’s heat is directed straight into the still solid PCM.
‘This heat, in turn, melts the PCM – kind of like wax – and turns it into a liquid.’
Once the material has become liquid, it retains thermal energy, but without absorbing any more heat.
Warm drinks – like coffee or tea – are best enjoyed at 58 degrees Celsius,’ Sedlbauer said.
‘In order to reach and maintain this temperature, we fill the mug with a type of PCM that becomes a liquid at exactly 58 degrees Celsius.’
The material absorbs the warmth of the mug’s content like a sponge, stores it and brings it down to the optimal temperature. And then the PCM helps maintain the content’s temperature at this optimal level by slowly releasing the stored heat back into the mug’s contents.
‘Under ideal circumstances,’ Sedlbauer says, ‘the optimal temperature can be maintained for 20-30 minutes.’
The material can be used in reverse, for example to keep beer cool at around seven degrees C.
The Frauenhofer Institute is in discussions with a number of manufacturers to bring the smart mugs on to the market by the end of this year.
‘We don’t know how expensive they’ll be yet,’ Sedlbauer says. ‘We are already talking with different companies.’