.

Fig. 8: Northeast view of the “Living 2015” prototype.
© TU Darmstadt, Kubina

Fig. 9: Internal view: Alongside the cooling ceiling elements, the use of PCM plasterboard also played a crucial role in obtaining the desired constant interior temperature.
© TU Darmstadt, Christian Stumpf

Fig. 10: Frost spraying of apple trees in the Altes Land area near Hamburg
© Obsthof Axel Schuback, www.apfelpatenhof.de

Fig. 10b: Frost spraying of apple trees in the Altes Land area near Hamburg
© Obsthof Axel Schuback, www.apfelpatenhof.de

Fig. 10c: Frost spraying of apple trees in the Altes Land area near Hamburg
© Obsthof Axel Schuback, www.apfelpatenhof.de
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In practice

“Living 2015” prototype

The prototype solar house designed by students from the Technical University of Darmstadt won the “Solar Decathlon” international competition in the USA in 2007 for the most attractive and energyefficient solar house. This energy-independent building was constructed on the TU Darmstadt campus and then transported to the USA once it was finished. The house is a lightweight wooden construction with a low heat storage mass compared to solid constructions. It has a floor area of 80 square metres. In order to combine the highest possible living comfort with the lowest possible energy consumption, a compact building envelope with excellent insulation was selected. 50 square metres of BASF plasterboard containing PCMswere integrated into the walls. In addition, 50 square metres of active, water-carrying PCM cooling ceiling elements from ILKAZELL were used.

As part of the energy concept of the Darmstadt prototype building, the use of PCMs played a crucial role in maintaining the required constant interior temperature of the house. The students implemented an intelligent system to transport the heat stored in the melted wax out of the house: Cold water at 16 °C is fed from a water tank through the cooling ceiling elements during the day, thus actively cooling the room, while at night the heated water is fed to the photovoltaic modules attached to the roof, where some of it evaporates. The cooling effect achieved by the evaporation process cools the residual water again, which is then returned to the water tank. The inclusion of the PCM plasterboards with a thickness of 15 mm in the Darmstadt lightweight construction means that the structure can store as much heat as a 90-mm concrete wall.

En passant - Frost protection for apple trees

Plants do not have body heat of their own, and are thus directly exposed to the surrounding temperature and generally have no means of protecting themselves. However, there are some species in the highlands of the Andes in South America that store water in cavities in their trunks in order to protect themselves against frost damage. On cold nights, this water begins to freeze, thus releasing heat of crystallisation, also known as heat of solidification, which prevents further cooling and stops the plants themselves from freezing.

Humans are now using the same approach: In order to protect fruit trees against frost damage, they are artificially sprayed with water on cold nights. The consequence of this spraying is that blossoms and buds are covered with an ice layer. The frost protection effect occurs thanks to the release of heat when the water solidifies (freezes) on the blossoms. The steady growth of this ice layer leads to a continuous freezing process that ensures a constant temperature of 0.5 °C inside the ice sheet. In this way, the buds and blossoms are protected against freezing.

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