As Jan Gustavsson, President of the association and resident in one of the terraced houses, explains, “the cost of oil rose sharply in the early 2000s, so we had to do something to reduce our energy costs”.
When the energy renovation project with ENWELL AB Göteborg began in 2002, the association at Hönö was using around 170 m³ of oil per year (equivalent to 1,700 MWh of energy).
The first stage involved drilling 22 boreholes 200 metres deep, coupled with 4 heat pumps. Because the capacity and efficiency of the heat pumps have gradually increased over the years, today the use of oil is almost zero.
To supply the heat pumps with as much thermal energy as possible, additional boreholes were drilled in two phases, bringing the total to 36 boreholes with an average depth of over 200m, making a total of 7,900m of boreholes. However, despite this additional drilling, a drop in the temperature of the brine from the boreholes wasobserved.
So, since 2013, the boreholes have been actively recharged using hybrid panels to improve the energy balance and increase brine temperatures.
Hybrid solar power to heat boreholes and supply electricity to heat pumps
In 2021, the association at Hönö was equipped with SPRING hybrid panels to increase the production of electricity needed to run the heat pumps and to heat the water in the geothermal circuit.
With the average temperature lift of the brine in the geothermal loop 2.8°C higher, the heat pumps offer higher efficiency and heat production. This reduces the need to use fuel oil for the auxiliary boiler and cuts heat pump operating hours, thereby extending their lifespan.
In the long term, the solar heat from the hybrid panels ensures that the boreholes will continue to provide the thermal energy and temperature required to keep the heat pumps running efficiently and economically.
Today, the association at Hönö uses around 340 MWh of electricity a year to provide heating and hot water for its residents, a reduction in energy consumption of 80% compared with 170 m³ of oil (1700 MWh). 170 m³ of oil would have given a primary energy value of 244 kWh/m² and an energy class G according to current criteria.
Geothermal and hybrid solar energy: a high-performance system to free you from fossil fuels
Thanks to the efficiency of this geothermal heat pump plant, the community association has achieved a primary energy value of 47 kWh/m², well within energy class B. CO2 emissions have been reduced from 490 tonnes per year to 8.8 tonnes per year, a reduction of over 98%.
What’s more, as all the investments were self-financed, this coupling is very attractive from an economic point of view, while costs have been kept low over the years.
For both the association at Hönö and the residents, energy class B means that they meet the requirements for green loans, further reducing running costs and increasing the value of the homes.
