In order to reduce the acoustic impact of the pump operation at the Malta Hauptstufe (main stage) power plant, VERBUND has developed a package of technical measures on the basis of scientific investigations, is now presenting them to the authorities in the course of a water law procedure and will then implement them promptly.
The Malta Hauptstufe power plant in the Carinthian Mölltal Valley is in daily operation in order to efficiently (and CO2-free) offset increasing fluctuations in the domestic power grid due to the volatile supply from wind turbines and photovoltaics. When necessary, during turbine operation the power plant can feed electricity into the grid, or in the event of surplus energy, it can take electricity from the net by means of two pumps and store it temporarily.
During this pump operation, noise emissions occur which the local population perceives as very bothersome. In order to have clarity on the matter, an acoustic assessment and based on that, an environmental health assessment were commissioned, and these showed a need for action. In the course of direct dialogue with a citizens' initiative formed in the towns of Reißeck and Mühldorf, with both municipalities, as well as with the state of Carinthia and the competent authority, VERBUND pledged to work out possible technical measures to reduce the acoustic impact during pump operation at the Malta Hauptstufe power plant and to implement these measures quickly when their effectiveness has been verified.
Legal framework for implementing constructional measures
On the basis of the two independent assessments, an internal team of experts worked out technical concepts in consideration of the most recent scientific findings, the implementation of which promises a significant improvement to the current situation. In doing so, the technical specifics of the facility had to be combined with feasible solution approaches. The goal of the investigations was and is to achieve an acoustic emissions status which as far as possible meets the local environmental requirements, in close consultation with the environmental medicine expert. Information on these investigations was regularly passed on to the citizens' initiative, both municipalities, the state of Carinthia and the competent authority.
After one technical solution was shown to be the best suited, the Chief Water Authority responsible for legal approval of the power plant was informed of the status quo and of the planned technical measures for reducing noise, in order to create a legal basis for VERBUND.
Based on this, the Chief Water Authority has now initiated proceedings regarding the planned modifications and fittings to the power plant facility, in accordance with the Water Rights Act. This includes an evaluation beforehand of the expediency of the intended measures and, following implementation, a corresponding review.
Further steps at the power plant location
The vibration measurements carried out the end of March 2017 on the pumps at the location, in conjunction with simultaneous sound measurements, confirmed that a significant moderation of the bothersome sound frequency would be possible with a downstream "silencer" (also known as a resonator). As a result, a production order was placed for a pilot resonator developed especially for this facility. The manufacturing process, which is complex because of the special requirements, will presumably be completed the middle of May 2017.
After the resonator has been installed at the first pump, further experiments will be made to optimise the noise reduction, attended by sound measurements in the nearby residential area, carried out by external experts under the supervision of the authorities. First results can be expected in the summer of 2017, which will then serve as a guide for the further steps.