CO2  neutral building with zero use of fossil fuels

The Danish hearing aids factory Widex has built a new domicile with both administration and production premises near Lynge, North Zealand. The cooling and heating needs of the building are met by means of seasonal storage of cold in the winter and heat in the summer in the limestone layer approx. 100 metres underground. So far, this is the largest building whose heating and cooling needs are covered without external energy supply, apart from auxiliary power supply for pumps etc.

The facility has been designed and delivered by the company Enopsol ApS, which has been working with facilities for energy storage in ground water for many years. Overtime, Logimatic (former NHL Automation) has become Enopsol's subcontractor in many installations.

According to calculations, the installation will be able to save Widex approx. 70% of the energy cost compared to energy costs for conventional installations.

ATES – Aquifer Thermal Energy Storage

In brief, the installation consists of a heat exchanger which separates the water in the building from the water underground. The heat exchanger is connected through pipes to two wells outside - one cold and one hot.

When cooling is required, water with temperature of about 9 °C is obtained from the cold well. It gives off its "cold" in the heat exchanger and then the water which leaves the heat exchanger and which has been heated to about 20 °C is pumped down and stored in the warm well until the building needs heat.

When heating is required, the heated water is pumped up from the hot well, while the cold water is pumped down to the cold well. The temperature of the hot water is not high enough for the water to be immediately used for heating purposes. Therefore, it runs through a heat pump, which draws energy from the ground water and sends hot water with temperature of about 45 ºC to the heating surfaces in the ventilation system.

A well pair consisting of one cold and one hot well is called a dipole. The Widex factory has five dipoles distributed over the entire site, and there are also two control wells, where one can keep an eye on unforeseen changes in the groundwater in the area.

The environmental permit requires thermal balance in the system at the end of a period of up to three years. When the cooling need is somewhat greater than the heating need, some of the surplus heat will be used for snow melting on roads and paths in the area.


Since the ATES facility is the only facility used for the heating and cooling of the 36,000 m2 building, stability is a key parameter. For this reason, Logimatic (former NHL Automation) has decided to use slightly more expensive industrial components for the entire system.

The SCADA system

A large 19” industrial PC with touch screen has been selected for operation. It provides good overview as well as details with clear graphics showing the current energy flow and the accumulated amounts of energy. For Logimatic (former NHL Automation), which is an IGSS Solution Partner, a SCADA system from IGSS is a natural choice. The SCADA system is a single-user system and the main HVAC control system of the building retrieves data from it via an OPC server.

In order not to put the complex system out of balance, the entering of new set-points and other parameters is password protected.


It is natural that the building itself should report its need for either cooling or heating. It is then up to the technical installations such as ventilation, heat exchangers, heat pumps and the ATES system to get ready to deliver the required performance. This way, the entire system is controlled by several PI/PID controllers in series. The greater the departure from the actual set-point (room temperature), the higher the risk will be for the system to respond too slowly, or for the outer parts to fluctuate.

"The fact that the heat pumps are regulated in relatively few steps does not make the task easier," says Niels Larsen, Logimatic (former owner of NHL Automation), and continues "One stage  was such a big milestone that it caused major transient current problems with the subsequent regulators of the ground water section. Only when we received a current measurement signal from the heat pumps control panel and used it as a feed-forward signal for regulation did we manage to achieve good quality in the regulation of the groundwater section."

35 controllers in the PLC

It is somewhat surprising to outsiders that 35 controllers are used for the facility’s control system, but it says a lot about the complexity of the assignment. Each dipole consists of no less than 38 measuring points for pressure, temperature and flow, among other things. PLC equipment known in the industry as being durable, reliable and dependable has been selected as hardware for the facility's control system

There are panels set up at all 10 wells in the five dipoles. They have pipe connections and valves on one side and electrical equipment on the other. The pump cannot be seen because it is submerged into the well casing.

1 MWh per day saved for the winter

In the hot days at the end of June the screen of the SCADA system shows that about 1 MWh of energy is pumped into the ground under Widex every day in order to be retrieved later for heating. The heat loss during storage is astonishingly small.

Calculations show that Widex can save approximately 90% of the cost of cooling and 50% of the cost of heating, which constitutes the basis for the previously mentioned annual savings of about 70%.

These savings will be approximately 700 MWh, corresponding to 1,000 tons of CO2 in the climate account.

More facilities on the way

Enopsol and Logimatic (former NHL Automation) have several new facilities in progress and even more on the drawing board.

The first facility in a garden centre has already been installed, transforming the centre from an energy consumer to an energy producer. The facility is expected to have a strong knock-on effect in this sector.

Another large facility in Ramboll's new head office in Ørestaden will be commissioned this year.

The same applies to a facility in the new low-cost terminal of Copenhagen Airport. Here, the plan is to continue with ATES installations as HVAC installations in the existing airport buildings are renovated in the next four years.


Widex A/S develops and produces digital hearing aids for the benefit of the 500 million people worldwide who cannot hear well.

Since Christian Tøpholm and Erik Westermann founded Widex in 1956, the family-owned company has been striving to provide the best solutions in the world both technically and audiologically to give those with impaired hearing the opportunity to experience the world just as everyone else. With a global market share of approximately 10%, Widex is among the six largest producers of hearing aids worldwide.

For many years Widex' head office has been in Værløse. All activities are moved to Allerød in the spring of 2010, where 650 people are employed. The new head office is a spectacular building. With several of the world's newest green and environmentally friendly technologies, the building sets new standards for the way companies can and should build in a time when climate change plays a key part in our consciousness and conscience.

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