Haltia is heated and cooled by energy from the sun and the earth. The goal is for the building to have a self-sufficiency rate of 75% in terms of heating and 100% in terms of cooling.
Heating According to the Cycle of the Seasons
The rock beneath Haltia has 15 boreholes that extend to a depth of about 250 metres. They contain a total of 11 kilometres of geothermal piping that is the foundation of Haltia’s heating and cooling system. Some 20 cubic metres of geothermal fluid circulate in the pipes, transferring thermal energy between Haltia and the bedrock. The geothermal fluid contains ethanol and water.
The suns heat accumulated in the bedrock over millions of years can be used in the winter to heat Haltia. The geothermal fluid runs through the heat transfer pipes to the bedrock, where the heat accumulated in the bedrock heats it up. Once heated, the fluid returns to the building.
In the building, a heat pump takes heat from the geothermal fluid, i.e. cools it. The pump further increases the temperature of the received heat and transfers it to the building’s heating system, including underfloor heating and radiators. The cooled geothermal fluid then returns via the pipes into the ground, where the natural heat of the earth heats it up again.
Cooling from the Rock in Summer
On sunny summer days, heat often accumulates in buildings; the indoor temperature tends to rise higher than desired. You then have to cool the indoor air by removing the excess heat. Usually the heat is transferred out by refrigeration equipment.
At Haltia, the heat is removed using fan convectors and chilled beams that have cool water circulating in them. When the cool water removes the excess heat from the building, it gets warmer. The heat transferred to the water is transferred back to the building’s geothermal heating system and via the pipes back to the bedrock.
After the winter heating period, the bedrock’s temperature is slightly below the normal temperature. As the warm geothermal fluid is being circulated from Haltia to the bedrock, the fluid becomes cooler, i.e. gives out heat, and returns to the building cooled. At the same time, the bedrock gets slightly warmer.
Storing the Sunshine
Energy is also collected for Haltia’s heating system by the solar collectors located on the building’s roof. With the so-called evacuated tube collectors, the sun beams reflect through a vacuum onto a black surface and thus heat it and the heat carrier inside the collector. Thanks to the vacuum, the heat remains in the tube as the surrounding air has no access to cool it.
The heat carrier heats the frost-resistant solution that circulates from the solar collectors to Haltia’s heating system. The heated solution is used together with geothermal heat to heat the water for the supply air devices, radiators and underfloor heating circuits as well as for the water used at Haltia.
When the solar collectors provide more heat than is needed at that moment, the excess solar heat can be directed to the bedrock with the geothermal liquid. This also prevents the solar collectors from overheating.
By harnessing hybrid energy from the rock and the sun, the goal is for mains electricity to be needed for only 25 per cent of the heating energy at Haltia. The electricity used by Haltia is environmentally labeled Ecoenergy.
Recovering Waste Heat
The waste heat generated by Haltia’s refrigeration apparatus and other devices is recovered to heat the supply air. Depending on the season and the need, it will be used for Haltia’s heating or stored in the bedrock.
Frugal Use of Water
The automatic water taps and waterless urinals at Haltia contribute to reduced water consumption. In the summer, water will mainly be heated by energy generated by the solar collectors, and in the winter by geoenergy.
Air Conditioning According to the Number of People
Haltia’s active, self-regulating air-conditioning system reacts to the number of people in the building and thus makes it possible to monitor and adjust the indoor air quality. Haltia includes several separate facilities that have separate entrances. There is therefore no need to keep the air conditioning on in the whole building if only some of the facilities are in use.
Haltia’s indoor air is controlled by an automated system, i.e. fresh air is taken into the building only the amount needed at any given time, which means that air conditioning always works in an optimal, energy-efficient way. The system uses little electricity but ensures high-quality indoor air. The waste heat generated by the ventilation system is recovered and used for preheating the incoming air.