In addition to its continuous efforts to optimise the plant’s energy efficiency while keeping all processes fully operational, ebswien hauptkläranlage is committed to the use of renewable energies (project “SternE – Strom aus erneuerbarer Energie”). Through a variety of sub-projects, a savings potential of 6,800,000 kWh/a can be achieved. On an annual basis, this equates to
- approximately 11% of the overall energy consumption of ebswien hauptkläranlage
- a CO2 reduction of Vienna’s climate footprint by more than 2,800,000 kg
On account of the special plant conditions (high volume flow and head), the installation of a double regulated Kaplan turbine in the outlet structure provides an efficient form of energy production. The generated electricity is fed into the plant’s distribution system and helps to cut total electricity consumption by 2%.
Since May 2009, the turbine in the outlet channel has been in operation and meets all expectations by producing up to 1.3 million kWh of clean electricity annually. The power output typically depends on the difference in water levels between the plant outlet and the Danube Canal. When the Danube Canal carries flood water, the turbine generates less power.
Since May 2013, a huge hydrodynamic screw upstream of the Kaplan turbine - 13 metres long and 26 tonnes heavy - has been generating clean electricity. Around 550 million litres of purified water flow through a channel to the outlet structure, thereby passing a height difference of 1.7 metres. The hydrodynamic screw, with its inclined shaft aligned in flow direction, uses this gradient for electricity generation: the flow of purified water sets the hydrodynamic screw into a rotational motion, which is converted into electricity by a generator. This way, 500,000 kWh of eco-electricity is produced annually, corresponding to roughly one percent of the plant’s overall energy consumption.
The installation of a solar thermal energy system with a capacity of 88 kW on top of the flat roof of the office and social building, with large-sized collectors (collector size: 126 m²) for utilising solar power derived from the sun, has helped to reduce the consumption of district heat for water heating (shower and kitchen) by 25%. The solar energy system is combined with the existing water heating unit in such a way that hot water is preferably produced from solar energy, and only when more energy is needed, or during adverse weather conditions, the system will switch to district heating.
With a photovoltaic unit mounted on the flat roof of ventilation unit no. 2, ebswien hauptkläranlage produces as much as 10,500 kWh of electrical energy per year. The solar unit has a capacity of approx. 10 kWp and a collector surface of 60 m². With this additional source of energy, three electric vehicles and the newly purchased e-bikes for use on the plant premises can be charged at the solar filling station.
A small wind turbine with a power output of roughly 10 kW has been in operation on the premises of ebswien hauptkläranlage since mid-2011. The small wind turbine has a total height of 23 metres and its rotor is 8.5 metres in diameter. To generate electricity, three rotor blades convert the wind energy into a rotation, which operates a generator, similar to an ordinary bicycle dynamo. The small wind turbine generates enough clean electricity for the lighting system in the 3,500-metre-long sewer passage in the “basement” of the plant premises (420,000 m²).