PCM Trees at Das Tropenhaus, Berlin

   This is by far the most creative usage of phase change material in a greenhouse application, I’ve ever seen.

   Just a quick bit of history... Construction of the botanical gardens in Berlin began in 1897 with the purpose of exhibiting exotic plants brought back from the German colonies.  ”Das Grosse Tropenhaus”, a main feature of the botanical gardens, is currently the largest, self supporting, glass structure in the world.  

   This gigantic tropical greenhouse maintains a temperature of 30 degrees Celsius with high humidity.  Before its recent renovation, it utilized approximately 1,500 tons of coal a year.  After recent renovation, energy consumption levels are one-fifth of previous usage.  Wallboards, tiles and concrete containing PCM, were considered for energy storage inside the structure.

   

   In the middle of this glass cathedral are two large tree trunk structures, constructed with panels containing PCM with 26 C phase change temperature.  These “tree trunks" are camouflaged by the tropical plants around them.  They blend in so well, I’ve still not been able to identify them on their webcam.  During the day, the upper areas of the greenhouse are heated by the sun. The PCM inside the “trunks” has been cooled by, I’m assuming, night time ambient temperatures.  A small fan pushes the hot air downward.  As the hot air passes through the “trees”, the PCM cools the air that is then circulated down to the plants below. The opposite happens at night.  The PCM is warmed by the hot air, produced during the day.  Cool night air is forced downward and warmed by the PCM and drifts down to the plants below.  The truly amazing part... the only power needed to circulate the heated and cooled air is enough electricity to operate a fan.  Truly amazing!