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Warm pool water through heat recovery

Cuxhaven, Germany

Energy-efficient air conditioning technology at Strandhotel Duhnen

The renowned Strandhotel Duhnen in the North Sea resort of Cuxhaven has been accommodating guests for 125 years. Today, the hotel directly on the Wattenmeer National Park and the adjoining Aparthotel Kamp with its fully equipped holiday apartments offer all the amenities of a holiday hotel in a family atmosphere. In doing so, the hotel management not only has the well-being of its guests in mind, but also the environment. State-of-the-art Daikin air-conditioning technology and technology- and behaviour-optimised energy management not only ensure that guests feel comfortable in all hotel areas. Integrated heat recovery also saves a significant amount of energy and heats the water in the hotel's pool.

 

Outside of Strandhotel Duhnen

The renowned Strandhotel Duhnen in the North Sea resort of Cuxhaven uses heat recovery to heat the hotel pool. © Daikin

 

The family-run Strandhotel Duhnen on the kilometre-long North Sea beach of Cuxhaven offers all the amenities of a modern 4**** establishment in its 67 spacious single and double rooms, six junior suites, two sky suites with personal spa and 19 holiday apartments. A spacious wellness area with swimming pool as well as a restaurant offering regional delicacies, a cocktail bar and maritime pub provide variety and relaxed well-being for the guests at the holiday and wellness hotel.

 

Energy-efficient air conditioning technology from a single source 

The owners of the hotel used the extended periods of Corona lockdowns, during which hotel operations had to be suspended, to renovate and modernise. Thus, the air-conditioning technology was updated both in the guest rooms and in the public areas on the first floor of the 1976 part of the building, which houses the reception front desk, the hotel lobby, the breakfast room, the “Four Seasons” restaurant, the Lido Bar and the “Düne” event room. As in the past, the company relied on solutions from Daikin.

Room equipped with a indoor unit from Daikin
Room equipped with a indoor unit from Daikin

Feel-good climate guaranteed. From now on, guests will benefit from state-of-the-art air conditioning technology in the guest rooms during their stay at the Strandhotel. © Daikin

“Our hotel is very quality-conscious and for us the price-performance ratio must be right. Since we have been very satisfied with the Daikin systems so far, another concept was out of the question for us. The high standard, good reputation and wide distribution of Daikin provide the necessary confidence in the reliability of the technology,” explains Kristian Kamp, managing owner of Strandhotel Duhnen, adding: “For us, the modernisation of the air conditioning technology focused on energy efficiency. That’s because our hotel has already been honoured in the past with the gold medal of ‘DEHOGA Umweltchecks’ for its sustainable and environmentally conscious business concept. As part of the ‘Green Travel’ initiative, our hotel is recommended to interested guests with a ‘green thumb’.” To ensure that these demands on the new air-conditioning technology were well implemented, Kamp brought on board master refrigeration engineer Leif-Arne Tegt from Fritz Kälte-Technik and Pascal Sansen, technical consultant at Daikin Airconditioning Germany GmbH.

 

“I was very pleased that Kristian Kamp and Leif-Arne Tegt joined me to complete this building project together. Our goal at Daikin is to meet the demands of specialist companies and customers in the best possible way – especially when it comes to the topics of CO2 reduction and energy efficiency. We are not afraid to use complex technologies and make tricky considerations in order to plan and implement a system in the best possible way. For me personally, finding efficient solutions together is always an exciting experience,” explains Pascal Sansen.

 

The project was completed in two stages. After the first lockdown 2020, the focus was on modernising and equipping the guest rooms with modern air conditioning. The second step was to improve the climate comfort in the publicly accessible guest areas on the first floor. Some control and flow optimisations became necessary here compared to the previous system. But the main reason for the decision to modernise and convert to a Daikin water-to-air heat pump with heat recovery was the potential use of the waste heat generated to heat the hotel's swimming pool and domestic hot water system.

 

Info box

Type of property 4**** hotel with apartment house
Hotel facilities 75 hotel rooms, 19 holiday apartments, spa and wellness area/swimming pool, restaurant, bar, lobby, breakfast room, bistro
Year of construction The part of the building involved dates from 1976 and includes hotel lobby, restaurant, function room, the “Lido Bar”, breakfast room as well as reception front desk with a total area of approx. 450 m 2. It underwent modernisation in 2021.
Technical equipment

New equipment in public area:

  • 1 water-cooled VRV IV+ Heat Recovery System (RWEYQ22T9) with 61.5 kW cooling capacity and approx. 74 kW heat output 

  • 10 ceiling cassette indoor units (1x FXZQ 32; 5x FXZQ 40; 1x FXZQ 50; 3x FXFQ 50)

  • Ventilation kit in breakfast room: Retrofit communication box EKEQMCBA and expansion valve kit EKEXV100
     

New equipment in guest rooms:

  • 3 compact Mini-VRV outdoor units (RXYSQ) in 2 sizes with 5 and 8 hp respectively 

  • a total of 46 FXAQ15 and FXAQ20 indoor units for easy retrofitting

  • KNX interfaces (KlicDI.VRV) for control via the building automation system
     

Inventory units:

  • 2 Daikin FDXS50 indoor units in the Sky suites (2016)

  • Multisplit outdoor unit 3MXS80

  • Sky-Air simultaneous split RZQG71 with 2 ceiling cassettes FCQG35 (2016)

Air conditioning brought up to date

The Strandhotel Duhnen has been rebuilt again and again during the 125 years of its existence. Today, the hotel consists of three different building complexes, which were built, expanded and repeatedly modernised in several construction phases. The family charm and the classic ambience of the hotel have always been preserved – even during the present modernisation.

The hotel lobby, meeting area and restaurant were previously air conditioned by three Daikin 4MKS90D multi-split systems, each with two FCQ60B indoor units and one FCQ35B indoor unit built in 2005. The breakfast room was previously cooled with a condensing unit from another manufacturer, with the room's ventilation air conditioning system permanently running at partial load. In addition, all systems have in the past released heat unused to the outside air. This was now to change.

 

Future-orientated heat pump with heat recovery 

In order to provide guests with perfect comfort while optimising costs and ensuring smooth operation and full control over the technology used, the hotel's owners wanted a modern, energy-efficient and quiet system with high-quality workmanship that would eliminate the deficiencies of the aging equipment. 

Fritz Kälte-Technik, which has been responsible for implementing the air conditioning at the Strandhotel Duhnen for years, was involved in the planning process at an early stage and, in collaboration with Pascal Sansen from Daikin, energy efficiency expert Stephan Goedeke, who has been working at the hotel since 2014, and the Strandhotel's heating engineer, Andreas Kratzmann from G. Kratzmann GmbH, designed an overall system consisting of innovative air conditioning solutions exclusively from Daikin. For example, the public guest areas on the ground floor now use the modern VRV IV+ Heat Recovery series water-to-air heat pump for simultaneous heating and cooling. The Daikin VRV IV+ Heat Recovery provides 61.5 kW of cooling capacity and air conditions an operational area of approximately 450-500 square meters at the Strandhotel Duhnen. As a complete solution with integrated heat recovery, it meets all the requirements for centrally controlled climate regulation in buildings: accurate temperature control, ventilation, hot water production, plus the integration of ventilation units and door air curtains on request. Thanks to integrated heat recovery and VRT (variable refrigerant temperature) technology, the new Daikin system offers outstanding efficiency values and the greatest possible comfort. 

 

The waste heat generated during room cooling heats the swimming pool

The special feature of the use of VRV IV + Heat Recovery in the Strandhotel Duhnen is that the approximately 72 kW of waste heat generated during cooling is not simply released to the outside air as was previously the case, but is used to heat the hotel's own swimming pool and to preheat the service water in the entire hotel area of the main building. Both of these were previously heated conventionally with fossil energy but now do not incur additional energy costs. The swimming pool water is passed through a heat exchanger and thus heated to about 30 degrees. This allows savings of more than 17% compared to conventional pool heating. The heat remains 100% in the building process, without integration of outside air. Another advantage: heat recovery is silent and no recoolers are required.

The innovative Daikin technology of the VRV IV + Heat Recovery with integrated heat recovery shines with a SCOP value of 11.4. The SCOP (Seasonal Coefficient of Performance) value describes the energy efficiency and cost-effectiveness of heat pumps and represents the ratio of the heat generated by the heat pump to the drive energy (electricity) required for this. Values of 3-5 are considered very good. The higher this value is, the more efficiently the system works and this is reflected in the power consumption. In addition, the Daikin VRV IV + Heat Recovery outdoor unit is filled with recycled refrigerant – 

an important milestone on the way to a CO2 neutral future. Daikin has been using recycled refrigerant with R-410A refrigerant in all VRV systems manufactured and sold in Europe since November 2020 as part of its circular economy program called “L∞P by Daikin”.

 

Daikin VRV5 Heat pump

The Daikin VRV IV heat pumps used in the hotel are particularly environmentally friendly. Thanks to the L∞P by Daikin circular economy program, recycled refrigerant is used. © Daikin

Waste heat utilisation as a challenging task

Leif-Arne Tegt, owner of Fritz Kälte-Technik, has worked regularly with Daikin products since his apprenticeship and has successfully expanded the cooperation with Daikin in recent years since taking over the business. For him, the special challenge of the project lay in the required resource efficiency by connecting to the heating system to use the waste heat in the swimming pool. “Using the waste heat from the plant to heat the in-house swimming pool required a water-side connection. This was somewhat challenging for us as a refrigeration plant company. But in cooperation with Pascal Sansen from Daikin, energy consultant Stephan Goedeke and heating engineer Andreas Kratzmann, we were able to develop a very good concept here. The professional interaction of the trades is particularly important for such complex requirements for a target-orientated solution.”

 

Heated indoor pool

The customer's request to heat the in-house swimming pool by heat recovery was successfully achieved. © Daikin

Elegant appearance and technical excellence in the public guest rooms 

In addition to the water-to-air heat pump with heat recovery, the new air conditioning system at Strandhotel Duhnen consists of a 10 ceiling cassette indoor units mounted in the suspended ceilings in the lobby as well as in the restaurant, meeting rooms and hotel bar, and a ventilation kit for ventilation in the breakfast room. The indoor units can easily cool or heat rooms with ceiling heights of up to 3.50 m. The ceiling cassette indoor units also incorporate highly efficient filters that remove dust particles from the air, guaranteeing high air quality.

During the modernisation, preparations were also made for the installation of ventilation kits for systems still to be modernised in the future in the lobby, restaurant, back office, bar area, another conference room and three staff rooms.

 

concealed ceiling unit

In addition to the guest rooms, the air conditioning technology was also renewed in public areas such as the hotel restaurant. © Daikin

Powerful Mini VRV for air conditioning of guest rooms

In addition to the VRV IV+ Heat Recovery with heat recovery, three compact Mini VRV outdoor units were placed on the roof of the hotel to provide air conditioning for the guest rooms. An identical Mini VRV had already been installed and commissioned for an 11-room wing during the first lockdown in 2020. As a total solution, the energy-efficient air-to-air heat pumps with VRV IV+ technology each deliver up to 33.5 kW of cooling capacity and up to 37.5 kW of heating capacity at a height of just 823 millimeters and an installation area of less than 0.5 m2. This reduces both the energy costs incurred and the CO2emissions. The Mini VRV outdoor units can each be connected to as many as
64 indoor units and controlled separately.

Mini VRV outdoor unit
Mini VRV outdoor unit

The VRV outdoor units for air conditioning the hotel rooms are located on the hotel roof. © Daikin

Central energy management

Of course, for efficient management of energy consumption, centralised control and monitoring of the entire system is possible. All air conditioning units were integrated into the automation system of the Strandhotel Duhnen via the existing KNX building control system. Further substantial energy savings can also be achieved in this way.

 

State support with the Federal Support for Efficient Buildings (BEG)

Funding for the project was applied for from the German Federal Office of Economics and Export Control (BAFA) as part of the Federal Funding for Efficient Buildings (BEG). Energy consultant Stephan Goedeke, owner of an engineering and expert office for energy advice, was consulted as an approved energy efficiency expert for non-residential buildings for funding programmes of DENA, KfW and BAFA in the application process. The subsidy for Daikin's energy-efficient air-to-air heat pumps was approved as a so-called individual measure (BEG EM). A basic subsidy of 35% is available from the BEG for heat pumps such as Daikin VRV.

The modernisation of the air-conditioning technology at Strandhotel Duhnen was implemented within six weeks and completed on time for the end of the 2021 spring lockdown.

 

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