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Snow cooling in Sundsvall

Snow cooling is our most acknowledged energy efficiency project to date. In Sundsvall we have developed and operate a large scale snow cooling plant used for cooling the County Hospital. The plant, which has been in use since 2000, is the first of its kind in the world.

The County Hospital in Sundsvall is a massive structure that covers about
190 000 m² and – naturally – requires a heavy duty cooling system in order to maintain a comfortable indoor climate as well as keeping a variety of technical equipment from overheating.

Prior to the year 2000, a conventional cooling appliance was used for this purpose. However, the county council of Västernorrland has since the turn of the millennium committed to a more environment-friendly and energy-saving alternative in making use of a natural resource that is easily available in the north of Sweden, namely snow.

A natural choice

Before the snow cooling system was built there was already a snow deposit situated west of the hospital – mainly used by the Sundsvall municipality to dump snow that had been cleared from streets in the region. This undisturbed place proved to be the ideal spot for building the new cooling facility, since there would be no negative impact on the surrounding area and it was already a natural place for unloading massive amounts of snow.

Wooden chips prevent melting

The facility is equipped with a 23 feet (7 meters) deep bowl-shaped basin that is being filled with snow during the winter months. The snow-pool is made out of waterproof asphalt which provides insulation against any unwanted heating from below. During the spring and summer months the snow deposit is covered with a layer of wooden chips in order to prevent the snow from melting due to increased outdoor temperature. During winters with less snowfall, a set of snow-cannons can be used to secure that there is enough snow in the pool. However, using snow-cannons is still a more energy efficient solution than using a conventional cooling system.

The snow cooling facility

All in all the snow cooling facility consists of three main parts; the snow storage, a pumping station and a heat exchanger. Snow that has melted is being pumped through the heat exchanger where the water cools the technical equipment as well as the ventilation air which passes through the hospital.

Through this process, the water reaches a higher temperature – on the way back it is therefore used to melt more snow. This also eliminate the risk of shortage in cooled water since everything returns to the snow deposit where it melts just enough amount of snow that is required depending on the outside temperature. In other words; on hot days when much cooling is needed, the system gives a higher output due to more water being pumped and therefore more snow being melt, whereas it on colder days pumps a lesser amount and thus melting a lesser amount of snow.

Click to enlarge

How snow cooling works (Click to enlarge)

Benefits of snow cooling

Snow cooling offers three major benefits. First of all, electricity consumption is greatly reduced. Using snow to cool the hospital has reduced the need for electricity for cooling by more than 90 percent. The energy requirement to cool the hospital used to be 900 MWh per year but snow cooling requires only 65 MWh for pumps. Secondly no Freon-based refrigerants are used and thirdly, polluted snow is cleared away.