Borehole thermal energy storage in Köping
Overview
The borehole thermal energy storage (BTES) system at the Volvo Powertrain plant in Köping is currently the largest BTES system in Sweden. The factory is one of Volvo’s biggest for the production of transmissions such as gearboxes for trucks, boats and buses. Around 1,850 employees work at the site, which consists of five factory sections with associated offices and changing rooms. To reduce energy consumption and create a more comfortable working environment for employees, Volvo opted for a geothermal cooling and heating system.
The underground energy storage
The first storage unit with 125 boreholes has been commissioned in 2014. Volvo invested € 5 million in the system that was expected to reduce electricity and heating use by 5,000 MWh per year, equivalent to the annual energy consumption of around 300 homes with district heating. In the subsequent years, the system has continuously been expanded and today comprises a total of 215 boreholes with an average depth of 270 meters. This adds up to a total borehole length of 58 kilometers.
“We considered other types of cooling technologies, but they were not considered suitable. The investigation concluded that borehole storage was the most cost-effective solution in the long term and good from an environmental point of view.”
The challenge of great space cooling needs on the one hand and great heating needs on the other is typical for a factory. The underground thermal storage is a solution that can both balance and capitalise on the different needs. The system is used for cooling the buildings in summer, storing warmth from this process in the boreholes, and reutilising it for heating in winter.
“We heat it in the summer and take the heat out in the winter. In production, temperatures vary quite a lot, so one challenge is just to keep the balance. But we have a flexible system where we can switch between different layers depending on temperature.”
In early 2023, the latest geothermal storage was added to the system. It comprises 60 boreholes for the cooling of a new factory section. For the first time, a heat pump was connected to the thermal storage to additionally provide domestic hot water. Overall, borehole storage in Köping has been proven to be both stable and flexible. All buildings of the factory site are connected to the storage system.
Sources:
With kind permission from Geoenergicentrum Sweden:
Sv Geo 2 2023.indd (geoenergicentrum.se)