Energy efficient sport and spa pool

Building summary

Project status	In Operation
Location	Kirschenallee 52-54, 65451 Kelsterbach, Hessen
Completion	Februar 2010
Inauguration	Februar 2010
Building owner	Stadt Kelsterbach
Operator	GMF Gesellschaft für Entwicklung und Management von Freizeitsystemen mbH & Co. KG
Gross floor area	2,450 m2
Heated net floor area	2,150 m2
Gross volume	17,195 m3
A/V ratio	0.41 m2/m3
Key aspects	Heat insulation, Facade systems, Glazing + windows, Daylight planning, Daylight systems, Ventilation + heat recovery, Control technology, operational management, building automation

Project description

The swimming and spa pool, which opened in February 2010 in the town of Kelsterbach near Frankfurt am Main, replaces the public swimming baths built in 1965. The site, which has an overall area of around 2,500 m², is situated to the northeast of the municipality, which lies not far from Frankfurt Airport. When designing the leisure pool, an integral planning approach was taken right from the beginning that was aimed at achieving low energy consumption. An important prerequisite for this is a suitable structural and technical concept. However, the energy requirements should not be minimised at the expense of comfort, since the bathers should of course feel comfortable.

Research focus

The scientific monitoring is aimed at investigating in detail the impact of the operational management on the indoor environment, comfort and energy consumption. Because of the complexity of the ventilation and heating systems in larger swimming pools, this is of general interest. A particular focus is on the impact of the movable roof. Here it needs to be clarified in more detail as to which (dynamic) effects are caused by the open roof, whereby the indoor airflow will also be simulated (CFD simulation).

The scientific monitoring is aimed at investigating in detail the impact of the operational management on the indoor environment, comfort and energy consumption. Because of the complexity of the ventilation and heating systems in larger swimming pools, this is of general interest. A particular focus is on the impact of the movable roof. Here it needs to be clarified in more detail as to which (dynamic) effects are caused by the open roof, whereby the indoor airflow will also be simulated (CFD simulation).

Building concept

Alongside the actual swimming pool area is a highly insulated block that houses the entrance area, changing rooms, showers/WCs, restaurant kitchen and sauna quiet area. This is connected to the pool area, which is designed to be highly transparent and variable. A prerequisite for this – and a unique highlight –is the innovative foil-cushion roof, whose lightness enables a third of it to be completely retracted back. Firstly, that provides an attractive feature because the indoor swimming pool effectively becomes an “outdoor” swimming pool when there is warm weather. Secondly, the retractable roof enables considerable savings to be made in terms of the mechanical ventilation and, in particular, the dehumidification of the indoor air. This is because the opened roof enables the ventilation systems, including the energy intensive dehumidification, to be partly or entirely switched off. In addition to the restaurant area, the approximately 1,100-m² swimming pool building also includes a 25-metre-long training pool (260 m², 28 °C), a spa pool with access to the outside (103 m², 30 °C), a children’s pool (35 m², 32 °C) and a Jacuzzi (3.5 m², 36 °C).

Energy concept

The leisure pool is heated via a heating network from a neighbouring heating plant. This includes two peak load boilers, which each have a heating capacity of 2,040 kW, as well as a CHP plant with an electrical output of 352 kW. The maximum possible thermal load is 1,300 kW. In addition to the pool water and domestic water heating, 5 air-conditioning systems with an entire airflow volume of 58,500 m³/h, underfloor heating and fixed heating (radiators) are available for distributing and transferring heat to the swimming pool, sauna and restaurant areas.

The new building for the leisure pool is very energy efficient. This is achieved as a result of the high thermal insulation standard for the building envelope and by the highly efficient building services technology, which provides benefits in terms of the primary energy. The following individual measures have been taken, whereby the calculated savings are respectively based on the conventional, standard construction systems used for swimming pools:

• Compared with the applicable German Energy Saving Ordinance (EnEV) requirements, the thermal standard has been considerably improved, particularly in the front area of the baths that includes the entrance area, changing rooms, showers/WC and the sauna quiet room. Calculated savings effect for the fixed heating: 43 per cent (from 170 MWh p.a. to 97 MWh p.a.).
• The foil-cushion roof can be opened when the outdoor conditions are suitable. This is expected to enable the energy requirements for ventilation and dehumidification to be reduced by around 20 per cent.
• When not in use, the outdoor pool is covered over. That reduces the heat losses in the pool by an estimated 17 per cent (from 490 MWh p.a. to 412 MWh p.a.).
• The heat recovered from the pool backwash water leads to heating savings when feeding the indoor pools of around 50 per cent (from 117 MWh p.a. to 59 MWh p.a.).
• The improved heat recovery efficiency for the ventilation system (75% instead of 55%) reduces the ventilation heat losses by 39 per cent (from 821 MWh p.a. to 498 MWh p.a.).

The considerably reduced heat requirement achieved with these measures is mostly met by the CHP plant. In primary energy terms, this results in total energy savings of 51 per cent. In addition, other measures have also been taken that have not yet been calculated in this estimate:

• Use of modern ventilation systems and bathing water pumps with frequency converter control system (FC control)
• Use of building control technology (BCT) for optimised control
• All ventilation systems, including those outside of the swimming pool hall, have been equipped with a highly efficient heat recovery system
• The kitchen is ventilated via an induction hood that considerably reduces the electricity requirements for the fans and the ventilation heat losses.
• With a blower door test that was announced right at the beginning, a particularly airtight and high-quality construction was ensured.
• The extremely differentiated meter concept enables targeted optimisation during operation.
• The operator of the swimming pool will be obliged to ensure the energy-efficient operation of the baths; it is planned to achieve this using a bonus-malus system.
• The diving pool is heated using a solar absorber.
• The lighting systems are regulated and controlled in accordance with the light conditions.
• The air is dehumidified in the swimming pool hall using air recirculation. Well water is used for this and for feeding the pool water.

Performance

Information on this subject will become available as the project continues.

Optimisation measures and possibilities

Information on this subject will become available as the project continues.

Construction costs and economic viability

The total cost for constructing the swimming pool is around 15 million euros, whereby the retractable roof, which consists of membrane cushion elements on a timber frame construction, costs around one million euros.

Further information will be provided on this during the course of the project.

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