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Energy efficiency measures for public swimming pools: decarbonisation and transformation

Public swimming pools are not only popular and important leisure and sports facilities, but unfortunately also significant cost factors for local authorities. The energy costs for the operation and maintenance of such facilities are high, particularly due to the constant demand for heat and electricity. Many municipalities have even had to close their pools because they were no longer financially viable. We show ways to achieve an environmentally and operating cost-friendly changeover.

In view of rising energy costs and the climate-neutral endeavours of many local authorities, the implementation of energy efficiency measures is becoming increasingly important. There are currently around 6,000 public swimming pools in Germany (compared to 7,800 in 2000), the sustainable management of which can make a significant contribution to climate protection.

In this blog post you will learn...

  • which energy-saving measures are possible and necessary through structural refurbishment and technical building services
  • which renewable sources are suitable for supplying heat to a public swimming pool
  • what experience we have already gained - based on a few examples
  • what potential savings result from the measures described
  • and what conclusions we draw from the available experience and information.

 

1. Energy-saving measures through structural refurbishment and technical building services

Firstly, the structural and technical condition of the swimming pool should be analysed. The first priority should be energy-efficient refurbishment measures for the building envelope and technical measures (technical building equipment, TBE). These can usually reduce energy consumption considerably.

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Energetic optimisation of the building shell

Renovating the building envelope, including façades, roofs and windows, is an effective way of saving energy. By eliminating thermal bridges within the building - for example from the pool area to the cash desk/entrance area - heat loss can be significantly reduced. The same applies to the insulation of external slides that start/end in the building. These measures not only help to reduce energy consumption, but also improve comfort for users, as draughty and cold places in the pool disappear.

Energy-efficient heating and ventilation systems

An average German indoor swimming pool consumes about as much energy per year as 100 detached houses. A key factor here is the evaporation of the pool water, which draws heat away and therefore requires additional energy for reheating. Researchers have developed a new airflow system that reduces evaporation: This involves introducing supply air into the building from above at a lower velocity, creating horizontal temperature stratification that minimises evaporation. Simulations show that this method can reduce the heat requirement by more than a quarter.

Temperature reduction for water heating:

Lower temperatures in the pools, room air or showers can save a lot of energy. However, there are a few essential points to bear in mind.

  • Most swimming pools have several pools with different temperature levels. To avoid having to maintain the temperature of the warmest pool for all of them (and then mix it with cooler water), each pool should preferably only draw the energy it needs from a separate heat pump.
  • A similar principle also applies to the shower areas: Fresh water systems in the showers help to lower the flow temperatures and at the same time do not cause a legionella risk. In compliance with the 3L rule, a temperature level of 45-50°C in the heat pump flow is usually sufficient.
  • The pool temperatures themselves can also be lowered moderately without swimmers having to sacrifice comfort. The abolition of so-called warm bathing days should also be considered here.

Covering of outdoor pools:

Covering outdoor pools at night prevents the pool water from cooling down too much. This has a major savings effect. However, retrofitting covers, especially for organic pool shapes, is not always easy and is usually very expensive. In this case, the cover should always be planned at the same time as the new construction. 

Further measures as required:

  • Domestic hot water heat recovery using a heat exchanger on the fresh water and heat recovery from the ventilation (internal waste heat utilisation)
  • Caution when lowering the room temperature: Mould can easily form on thermal bridges due to the damp air. Care must be taken here to ensure that the humidity in the upper layers of air is not too high.

2. Heat supply from renewable sources

Another key measure to increase energy efficiency in swimming pools is to switch the heat supply to renewable energy sources. In the long term, this can significantly reduce operating costs, and cities and local authorities must also reduce their CO2 emissions so that they can achieve the goal of climate neutrality by 2045. There are several options for swimming pools to replace fossil fuels as a renewable heat source:

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Solar thermal:

By installing solar thermal collectors, solar energy can be used directly to heat the swimming pool water. This method is particularly effective in summer and can significantly reduce the load on conventional heating systems.

PVT systems

combine the advantages of PV and solar thermal energy. They generate both electricity and heat, which maximises the efficiency of energy generation. This dual utilisation of solar energy is particularly space-saving and efficient. The electricity is used for the building's own needs (lighting, pumps). This not only reduces electricity costs, but also contributes to CO2 reduction.

Geothermal energy:

The use of geothermal energy with heat pumps is a constant and reliable source of heat. Deep geothermal energy is particularly suitable for regions with favourable geological subsoil, but near-surface geothermal energy, in conjunction with heat pumps, is also a good supply option for swimming pools (see local heating network).

Nah- oder Fernwärme:

If there are heating networks in the vicinity of a swimming pool, whether local or district heating, this can be an interesting option for the operator. Indoor swimming pools are consumers of heat all year round, even in summer, which makes them attractive customers. Therefore, favourable prices are often possible for the purchase of heat. In addition, waste heat from the surrounding area can also be utilised, especially in summer - indoor swimming pools have a year-round heat requirement and are therefore a reliable customer. The decision for or against the use of a local heating network should be based on a profitability calculation that compares not only the investment costs but also the operating costs of an in-house heat supply over a period of 20 years with the heat prices on offer.

Biomass:

Wood pellets or wood chips can be used as sustainable fuels in biomass boilers. These are particularly useful in rural areas with readily available biomass material that would otherwise become waste. However, one should not ignore the CO2 release, which is considerably lower than with gas or oil heating systems (about half), but still present, so that this method is not to be recommended without reservation for climate and environmental protection reasons.

Examples from our working experience

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The "Inselbad" in Untertürkheim

In Stuttgart, the "Inselbad" in Untertürkheim is aiming for a climate-neutral concept. Here the renewable heat supply is realized through the use of river water and PV systems. The roof areas of the buildings are used for solar thermal energy or PV, or - following our recommendation - for PVT, we have also suggested aquathermal use of the river water flowing past. These (and other) measures are intended to replace the previous heating via gas boilers and cogeneration plants and thus achieve a largely CO2-neutral energy supply.

The "LEUZE" in Stuttgart

The thermal bath, also located in Stuttgart, consists of an indoor pool and an outdoor pool. The feasibility study envisages using the warm mineral water as an energy source for several heat pumps. This method offers high efficiency and significantly reduces CO2 emissions. In addition, the use of PV and PVT systems on the site, a parking garage and the adjacent cycle path is being examined in order to ensure the most self-sufficient energy supply possible. One variant combines the PVT sources and wastewater from an adjacent canal as optional or redundant sources for the mineral bath, the potential of which could be exploited even better via a cold network to a second, adjacent mineral bath.

Savings opportunities in numbers

By implementing the measures mentioned, significant energy savings can be achieved. For example, an average German indoor swimming pool that uses around 2,400 megawatt hours per year can save up to 34 percent of thermal energy by reducing the pool water temperature by 2 Kelvin. But it's not just comfort that can be saved: by using efficient sources and improvements in system technology, for example, in one of our projects with an indoor and outdoor swimming pool, we were able to achieve a CO2 saving of 57 percent for the most economical variant. The CO2 share comes almost exclusively from the public power grid, so the balance will continue to improve as the decarbonization of the power grid progresses (80% renewable by 2030, 100% by 2045 according to EEG).

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Energy-efficient swimming pool renovation: A good investment with a big impact

The implementation of energy efficiency measures in public swimming pools is not only ecologically sensible, but - despite often high initial investments - also economically advantageous - especially if you take the operating costs of the next 20 years into account when planning. Because of the high energy requirements all year round, it is even more worthwhile to invest in an efficient source that is available all year round in order to then reduce operational costs. Significant cost savings and CO2 reductions can be achieved through the use of renewable energy sources, modern technology and structural improvements.
There are already many examples of how to finance these measures: Neighboring municipalities can join forces and operate pools together across borders. There are also various government funding programs if swimming courses are also offered in the pools. Municipalities and cities that invest in these measures make an important contribution to climate protection and at the same time ensure the long-term operation of their swimming pools for their citizens.

 

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