When building the Valsana Hotel in Arosa, we created a hotel for the future. A hotel with sustainability at its core that is powered entirely without fossil fuels. How did we do it? By using geothermal energy and an ice battery that heats the entire complex.
The entire Valsana complex is heated using geothermal probes and by capturing and reusing waste heat from other appliances that is ordinarily lost to the surroundings. This waste heat is stored in a large tank or ice battery, essentially a large water tank housing a 400m pipe register of 1.5 m high pipes. Heat pumps draw their energy directly from this storage tank where a water-glycol mixture flows through the pipes which are in turn connected to the heat pump circuitry. When the heat pumps extract a large amount of energy, the water in the pipes freezes to form an ice block. The waste heat from the heat recovery system is fed back into the water basin to thaw the ice. If more waste heat is generated than energy withdrawn, the ice is melted and the water in the circuitry can heat up to 15°C.
A large part of our thermal energy requirement is used for heating water. The kitchen and especially the spa have a great demand for hot water. More than 50% of the heat emissions from the used water can be captured and recycled before the water is discharged into the sewage system. The waste heat is fed into the ice battery at relatively low temperatures, once again storing energy through the combined effect of freezing and thawing the water-glycol mixture.