Indoor-pool water loop — 24/7 load, usable as thermal battery. Part of the glass family — like our glass BESS, biogas plant and CHP.
The plate heat exchanger transfers heat from the boiler or heat pump onto the pool water with hygienic separation — heating circuit and pool water stay physically apart.
Fouling reduces transfer: the flow temperature must then run hotter and the heat pump loses COP. The AI watches the temperature spread and flags declining performance early.
Pool water, circulation, filtration, backwash (the pool-water treatment standard):
Overview: The Glass Pool → · Markets: pool markets →
Monitored: continuously · flow and return on both sides
The scenario: A thin layer builds on the plates. Transfer drops gradually and the primary side runs longer to hold the pool temperature, so the loss hides in the heat demand rather than in an alarm.
Method proven on a live European reference aquatic center; presented anonymously.
Estimate from metered / design values. Zero-grid-import windows are real (metered).
Grounded in the applicable national standards for pool water treatment, plant energy performance and building energy performance. Same knowledge base as the European reference site; presented anonymously.
the pool operating guideline fixes the order for refurbishments: 1) reduce losses (envelope, pool cover, insulate the surge tank, ventilation heat recovery), 2) recover heat (heat recovery, waste-water heat, filter backwash as a heat-pump source), 3) generate efficiently (heat pump > CHP > gas). This hierarchy is decisive for public grant applications: funders check whether losses were reduced before the generation investment. Concretely: insulate the surge tank, add an outdoor-pool night cover and service the ventilation heat recovery before or together with the heat-pump installation.
Basis: the applicable national standard.10
The applicable standard requires a minimum fresh-water make-up of 30 litres per visitor per day, independent of filter performance. This make-up dilutes metabolic products, urea and other substances introduced by bathers. At 1,500 visitors/week × 52 weeks that is 2,340 m³/a, which has to be heated from drinking-water temperature (~10 °C) to pool set-point (22-32 °C). At a 28 °C pool set-point this is roughly 50 MWh/a of heating energy for fresh water alone.
Basis: the applicable national standard
The applicable standard prescribes a maximum residence time of the pool water, depending on pool type: swimmer pools 4 h turnover, non-swimmer/paddling 1-2 h. This sets the minimum filter flow rate. For a 242 m³ lap pool at 4 h turnover that is 60.5 m³/h of filter capacity. Filter backwash once per day or above 0.5 bar differential pressure. Backwash water is warm (pool temperature − 3-5 K) and therefore a valuable heat-pump source.
Basis: the applicable national standard
Standard process combination for public pools: multi-layer sand filter + flocculation + chlorine-dioxide or chlorine-gas disinfection. Alternatives use activated carbon (treatment) or UV (disinfection). Sand-filter layering: fine sand 0.4-0.6 mm on top, gravel support layer below. Filter velocity max 30 m/h. Backwash at 50-60 m/h up-flow for 5-10 min, backwash volume approx. 5× the filter-bed volume.
Basis: the applicable national standard
Evaporation from the water surface is the dominant heat loss in an indoor pool (60-80 %). Smith/Löf variant of the Carrier formula: m_evap [kg/h] = β × A [m²] × (p_w_pool − p_w_hall) [kPa]. β-coefficient per the pool energy guideline (evaporation and ventilation) Tab. 4: 0.013 unused pool (covered), 0.040 normal use, 0.080 wave/diving pool. Evaporation enthalpy at 30 °C: 0.694 kWh/kg. Pool saturation vapour pressure via the Magnus formula: 611.2 × exp(17.62 × t / (243.12 + t)) Pa.
Basis: the applicable national standard
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