Heating and cooling by a BEO field

What is a BEO field?

Jan Laga: "BEO stands for borehole energy storage. Vertical boreholes up to 150 metres deep are arranged in a grid at intervals of 6 to 7 metres and 2 U-loops are inserted in each borehole in which a water-glycol (anti-freeze) mixture circulates. These U-loops are then connected at the surface via a collector. The heat exchange with the soil thus takes place through the tube walls. These tubes are made of very strong material and have an extremely long lifespan because they are not exposed to UV light or the elements. All the bores with U-loops and the connecting collector are called 'BEO field'."

How does it work?

Jan Laga: "In summer, the soil in the BEO field (about 12°C on average) is used to bring coolness to the surface, which is then used to cool the building.

As a result, the soil will gradually warm up a few degrees. When heat is needed in the subsequent heating season, the circulation of water-glycol will bring soil heat to the surface. In the technical area, a geo-heat pump will produce water at 40°C. This will then heat the building. So during the winter, we extract heat from the soil and it will cool by a few degrees as a result. After the winter, the cycle can start again by the next cooling season. If the system is designed according to the rules of the art and expertly operated, the energy consumption will be very low and the soil will remain nicely balanced."

Why do you use this thermal energy system in a circular building?

Jan Laga: "As already explained, the principle of geothermal energy is the reuse of summer heat in winter. This reduces the net consumption of new energy to a maximum. The energy cost is therefore also very low. Obviously, no fossil fuels are involved. Electricity is all that is needed and this will be generated from renewable sources as much as possible. This is also at the heart of the idea around circular construction."

What are the benefits of shallow geothermal?

Jan Laga: "The main advantages of shallow geothermal are:

• By far the lowest consumption and maintenance costs; these low costs allow the additional investment of drilling to be recouped quickly.
• No large heat exchangers with fans on the outside of the building as with conventional cooling systems or air-water heat pumps. These are often aesthetically and acoustically disruptive.
• Gasless systems are possible.
• Renewable energy with very low environmental impact.
• Future proof: in a few decades, geothermal energy will be the standard as is already the case in several European countries.
• Inside the building, the distribution of heat and cold is noiseless and without annoying horizontal air movements (cold draught).
• Large positive impact on EPB score so that often other expensive measures (extra insulation, special glass, sun blinds) are less necessary.
• Technology is fully mature / no functioning risks.
• Better assurance of building value in the future."

Is a BEO field often used in Flanders? In what kind of construction projects?

Jan Laga: "Geothermal energy is widely used in Flanders. Both for private housing construction and for larger projects such as offices, collective housing, hospitals, commercial centres, etc. The stricter building standards regarding insulation / building envelope together with progressively warmer summers are reducing the required heating capacity and increasing the required cooling capacity. New homes without cooling are at risk of summer comfort problems if they are not equipped with cooling at the start. Geothermal is by far the best solution for this."

How long does it take to build a BEO field?

Jan Laga: "The construction of a BEO field - depending on its size, of course - is a matter of a few days to weeks and is easily fit into a construction site's schedule. A geothermal system is hardly a factor making the construction time longer."

What are Tenerga's strengths in the circular construction project? Do you already have experience with circular buildings?

Jan Laga: "Tenerga's main asset in this project is its extensive experience of geothermal energy applied to buildings. Tenerga has very little experience with circular buildings in particular."

Was the choice of shallow geothermal for the 't Centrum project a quick one?

Jan Laga: "For a project of more than 1,000 m2, the choice of shallow geothermal is almost a no-brainer. The lowest possible CO2 footprint makes it the most ecological solution but it is also immediately the most economical. The client in this project quickly understood the value of the peace of mind that Tenerga offers and that the Total Cost of Ownership (installation cost + operational cost over the lifetime) for geo-climatisation is significantly more favourable than with any other system."