Experiencing innovation:

The centre of excellence for energy

The solar ice storage system under the new company headquarters is a triumph of modern energy technology. SCHNEPF implemented and perfected the bold idea of using a subterranean water or solar ice tank to heat a 2,500-m² office building in winter and cool it in summer. The system comprises an ice storage tank, solar/air absorber, heat pump and low-temperature consumer groups.

The heat pump uses energy drawn from the earth, water, ice formation within the ice tank, the air and sun to heat the building.

This entirely new energy concept earned SCHNEPF first prize at the German TGA Awards.

Building facts and figures:

  • Heat pump cooling capacity: 100 kW
  • Heat pump heating capacity: 73 kW
  • Absorption area required to operate the heat pump: 382 m2
  • Concrete core activation: 1,800 m2
  • Power generation from 320 m2
  • Photovoltaic system: approx. 50 kWp
  • Office area: 2,500 m2
  • Triple-glazed sun protection glass
  • Concrete volume as storage medium: 1,000 m3
  • Construction period: 7 months
  • Usable volume in ice tank: 350 m3
  • Renewable heating and cooling supply: 100%

Put on ice.

The centrepiece of the facility is the subterranean ice tank with a 350 m³ capacity and around 6 km of closed-loop piping. Filled with a mixture of water and anti-freeze, this serves as a heat exchanger for the brine/water heat pump installed within the building.

Ice tank facts and figures:

  • Depth: 5.5 metres
  • Diameter: 9.5 metres
  • Ice weight: 250 tons
  • Usable volume: 350,000 litres
  • Total length of piping: 5,700 metres
  • Heat pump: 85 kW heating, 65 kW cooling

Heating and cooling:
A year in the life of a building

During the heating phase, heat is drawn from the water in the ice tank and delivered to the building via the heat pump. The further withdrawal of heat causes ice to form on the piping. This ice layer expands within the ice tank from the inside outwards during the heating phase. At the end of the heating phase, the ice tank contains almost 100% ice.

In the subsequent warm season, the 'stored' ice is used to cool the building. The transferred building heat melts the ice from the outside inwards. This natural cooling process is used until the ice has fully melted and the water temperature in the tank rises to approx. 10 °C.

As a consequence, around 70% of the cooling energy required in summer is naturally covered by the 'stored' ice. If the water temperature in the tank continues to rise, the heat pump can also be used as a cooling unit. Waste heat from the pump is in turn now 'stored' in the ice tank. Whereupon a new sequence can now begin.

The fact that the building is pleasantly warm or cool all year round is also as a result of so-called core concrete activation. Coils containing running warm or cold water embedded in the concrete layers are used to heat or cool the concrete and effectively provide balanced temperature control within the rooms. Any peaks in temperature within individual application areas are regulated via induction outlets in the ceiling.

Fresh air – good and cost-effective

The fresh air supply is delivered via a high-performance ventilation unit that filters, preheats or precools and dehumidifies air from outside. A highly efficient heat regeneration system is able to transfer up to 80% of the energy contained in waste air to the air delivered into the building.

Only delivered where needed

The warm water requirement in the office building is fairly low. As such we opted not to install a centralised warm water heating system, also for the reason of avoiding any distribution and stagnation wastage or hygiene problems. Warm water is therefore available decentrally via tankless water heaters located directly at the point of withdrawal in the sanitary facilities and tea kitchens. The required electricity is supplied by the photovoltaic system (PV system) on the roof.

All good things come from above

On the flat roof of the building is a 320-m2 photovoltaic system for power generation with a peak capacity of 50kWp and an annual output of approx. 46,000 kWh. The power generated covers the building's usage, with any excess power then fed into the grid.

Impressive results

The annual energy balance for heating and cooling in conjunction with the PV system could be described as an energy-neutral overall balance; not least because of the outstanding thermal protection provided by the first-rate standard of insulation.

Our building effectively exceeds the provisions of the German Renewable Energies Heat Act (EEWärmeG) by 194%.

Additional surplus from the PV system balances out power supplies to the building management system, ventilation system, general office operations and our highly efficient interior lighting system.