Braedstrup Fjernvarme is the Danish site for Europe’s largest seasonal ground source probe heat store combined with a solar thermal energy system.
In phase one of the project, 50 REHAU RAUGEO vertical PE-Xa probes have been installed across an area of approximately 225m² area at a depth of 47-50m to store the heat generated by a 16,000m² solar thermal panel installation.
In summer, the hot water circulates at up to 85ºC within the probes and acts to heat up the surrounding ground and create a gigantic heat store. In winter when heat is required for the town’s district heating scheme, the stored heat is transferred back to the circulating water and extracted via a heat pump.
Using a compact geothermal borehole field, the ground is activated to store heat throughout the summer season and operates much more efficiently than the insulated surface mounted water storage tank which was used previously.
The solar thermal heat is currently providing district heating to 1200 homes in Braedstrup Fjernvarme but, because the system has the capacity for up to 3600 homes, the excess heat is stored for later use. In phase two of the project, planned for 2012-2013, a total solar heating area of 60,000m² will be installed with 250-350 probes drilled to store the heat.
REHAU RAUGEO PE-Xa probes were chosen for the heat store because they can easily withstand the high water temperatures of up to 85ºC without any deterioration in performance or risk of damage. The inherent durability of the PE-Xa material means it is also highly resistant to nicks or scratching during installation or whilst in the ground.
REHAU RAUGEO is a double-U probe constructed without a welding joint at the probe base. The feed and return consist of a continuous pipe curved around the probe base and encased in glass fibre reinforced polyester resin for additional protection. The risk of leaky weld connection is therefore excluded and maximum safety is guaranteed at the deepest point.
The Braedstrup Fjernvarme project is being used as a case study to evaluate how the efficiency of district heating schemes, which already account for 60-70% of domestic heating systems in Denmark, can be improved through extended use of renewable energy sources.
The Danish market is currently reviewing how it can develop a method to include renewable energy and CHP from common heating solutions such as district and block heating in the calculation of energy demand in buildings.
In order to make it possible to choose the most cost effective reductions in greenhouse gas emissions and grow energy consumption, the Danish Energy Authority and Central Denmark Regional Development Forum are funding a large scale project to develop a scheme introducing primary energy factors from renewable energy solutions placed outside the site/land register of the building and demonstrating how to reduce the primary energy factors on a common, decentralised natural gas-fired plant in Denmark.