Siemens: lake water for heating and cooling at the Bürgenstock Resort

Siemens: lake water for heating and cooling at the Bürgenstock Resort
A world-class luxury hotel recently opened 1,100 meter above sea level on top of Mount Bürgenberg in the Swiss canton of Nidwalden: the new Bürgenstock Resort. Its goal is to attract guests from all over the world. Switzerland’s largest hotel facility is heated and cooled with energy from Lake Lucerne, with approximately 300 m3 of water per hour pumped up the mountain. Lake water usage is managed via the Desigo CC building management platform from Siemens

Tourism has a long tradition in the Lake Lucerne region of Central Switzerland. The first hotel was built on the Bürgenstock in 1873, and over the following decades the mountain became a destination for gastronomy and tourism. In its heyday after World War II, prominent figures from the world of politics, business and society discovered the Bürgenstock Resort for themselves. Ownership changed hands several times around the turn of the millennium, until in 2008 Katara Hospitality, a subsidiary of the Qatar Investment Authority, took over the hotels and numerous other buildings. 

The new owners have invested nearly 550 million Swiss francs, creating a car-free resort with four hotels ranging from three to five stars, a total of 800 beds, 68 residence suites and a 10,000 m2 alpine spa. The conference center offers 2,200 m2 of space for more than 800 guests, including 31 meeting rooms and a ballroom for 500. The resort also features two indoor tennis centers that can be converted into event venues for 500 guests each. Twelve restaurants and bars, a 9-hole golf course, an ice rink, a movie theater and various retail stores offer visitors, conference attendees and foreign guests ample opportunities to linger. Nearly 800 persons will one day work on the Bürgenstock. The official opening ceremony was held in late summer 2017.


Energy from the lake 

To ensure the energy supply can keep pace with the facility’s expansion and modernization, a new power station was built to serve as the heart of the resort. It combines nearly 130 years of tradition with the latest technology. Just as in 1888, the water from Lake Lucerne is captured outside the village of Kehrsiten and pumped up the Bürgenstock. Back then, this was done to supply drinking water; today it supplies energy to the resort. The principle is simple. Heat pumps extract the energy from the lake water, which is then used to heat the buildings. 

New powerful pumps convey 78 liters of water per second up the mountain, an elevation difference of 500 meters. The old freshwater reservoir on top of the Bürgenstock is used as a storage basin; from there water is pumped into the power station. Heat pumps with 1.3 MW peak power heat the water in the system to 45 to 55°C, depending on the outside temperature. The water is then distributed to the various buildings and used either for direct heating or as a source of energy for the buildings’ heat pumps, which heat the domestic water to 65°C. There is a good reason for this two-stage system: If the water were transported at 65°C, the energy loss would be substantially higher than at 45 to 55°C, and the coefficient of performance (COP) of the heat pumps would be considerably lower. For cooling, the lake water is used directly. The water temperature 37 meters below the lake’s surface is a chilly 5 to 7°C throughout the year, so the lake water covers 70 to 90 percent of the heating requirements and all of the cooling. The water used is redirected back into the lake. It flows through a turbine, which recovers some of the energy. This energy is then used to pump the water up the mountain. 
 

Comprehensive building automation 

The power station is controlled using systems from Siemens. Thomas Guebey, head of the customer service team and overall head of Siemens projects on the Bürgenstock, reports: “The project was enormous. The safety and security of people and assets topped the list of priorities, along with uninterruptible supply.” The water from the lake travels in a nearly closed system; water is removed only to irrigate the green areas. “Safety is no longer guaranteed if somewhere a gate valve is defective, a pipe bursts or excess pressure builds up. That’s why we constantly collect data at all the crucial locations.” This data is compiled and recorded by the Desigo CC building management platform. “If the values are not right, the Siemens system automatically switches off and notifies those in charge,” explains Guebey. 

But Desigo CC manages, monitors and visualizes not only the heating and cooling. “The ventilation equipment, sanitation systems, room automation and area security are integrated as well,” continues Guebey. Desigo CC receives error messages from the electrical systems and measurement data from the energy supply system, and issues high-level commands to the shading and lighting systems. Sinamics variable speed drives from Siemens contribute to demand-based and ecological operation of the building systems and, in conjunction with other disciplines, provide just the right amount of heating, cooling and ventilation. Thanks to the uniform system structure, the individual components are perfectly coordinated and easy and intuitive to operate via Desigo CC. Site security is provided by Siemens video surveillance systems. “Thanks to this single-source solution, the inventory of spare parts can be kept at a minimum,” states Guebey. 

Unlike the hotels, the power station is already in operation. The station’s dedicated building also houses the control center and the associated computer rooms. “Our initial experience has been excellent,” says Guebey. “Since the power station was commissioned in January 2016, the technical services team has needed to address only a few growing pains.” Most of them were false error messages from the controls or defective gate valves that needed replacing. Everything has run virtually error-free since February 2016. Now the buildings are being gradually hooked up. The power station has yet to be tested under a full load; even during the very cold January of 2017 it ran at only about one-fifth of maximum. 
 

Enormous potential 

Water from other lakes is also used as a source of energy. For thirty years, Siemens has cooled the buildings at Building Technologies Division headquarters in Zug with water from Lake Zug in the Swiss canton of the same name. Siemens will also rely on this environmentally friendly energy supply at the new Zug campus due to open in the summer of 2018. Because of its much larger size, Lake Lucerne offers enormous potential for lake water use: It could supply 2,900 gigawatt hours (GWh) of energy per year. To put this in perspective: The heat demand of 100,000 residents totals 700 to 900 GWh. The lake could therefore supply the entire region with energy. Thanks to Siemens products, it is now heating and cooling the buildings of the Bürgenstock Resort.


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