A power supply for in-house needs, with an exceptional efficiency boost
BENNING supplies a new power supply system for Obernburg combined power station, with the emphasis on safety and sustained efficiency
It has long been a logical and cost-effective solution for major corporations and business parks to use natural gas in order to generate power and heat.*1 Rising gas prices are now placing operators under massive pressure, which calls for a logical optimisation of efficiency – and this also includes the self-generation option. The combined power station at Obernburg am Main stands as a model project for optimisation in this field – thanks to using BENNING’s modern, highly efficient components.
The Obernburg Industry Centre – abbreviated to “ICO” in German – is located in Miltenburg, in the Unterfranken region, adjacent to the banks of the River Main, at the base of the Bavarian Spessart forest. Its position is idyllic, by way of a contrast to the status of the Centre, which – being operated by Mainsite GmbH & Co. KG – stands as a modern industry park on a site measuring in excess of 170 hectares and retaining over 3,000 employees.
This site was set up in 1924 – as a production centre for textile viscose threads – by Vereinigte Glanzstoff-Fabriken AG. Since that time, ICO has expanded to be more than just Europe’s largest and most diverse chemical fibres centre. It also provides a home for more than 30 successful international companies of varying sizes and specialist fields. In addition to some firms which have come through from the Group’s previous structure, these are providers from the fields of medtech, medical analytics, plastics tech, paints and inks, reaction tech, logistics, chemicals and industrial services.*2
Energy for financial success
All of this business activity naturally requires energy – and this is generated by the specifically founded “Kraftwerk Obernburg GmbH” power station on a scale tailored to the onsite companies’ particular needs.
The power for the ICO – with any surplus output going to the public grid – depends on a combined gas/steam process, driven by a gas turbine supplying 60 MW with steam turbines downstream. The steam is then also utilised as a heat source and as process steam. The modern combined gas/steam process and the power station’s combined electricity/heat production inherently means that the Centre possesses high efficiency.
This is and has always been central to the operating company: many years before today’s price rises, the new core component of the power station – a gas turbine supplying 60 MW – was installed in the context of a renovation project commencing in 2018 and comprising a level of investment in excess of €50 million. And the three steam turbines, dating back as far as 50 years, and located downstream from the gas turbine, were renovated in order to enhance energy efficiency thanks to power/heat coupling.
Guaranteeing operating safety
The primary anticipated service life of the newly installed gas turbine exceeds 100,000 operating hours. In the interests of making it possible to achieve the projected service life, turbine shutdowns are planned for intervals of 4 years, which will enable the required overhauls to take place.
They will make use of the 2023 shutdown phase as a platform for optimising efficiency and uptime, plus the opportunity for replacing the power station’s existing conventional internal power supply profile with a state-of-the-art tech concept. In addition to the essential consumers in the turbine system, critical to operation – especially the standby oil pumps – the systems installed to cover in-house requirements can also be upgraded with new control panels as the project continues. Consequently, the new in-house supply system had to be capable of providing reliable power in both direct current and alternating current formats.
Maximum safety for critical consumers
Background: when a gas turbine comes to be switched off, the resultant cooling gives rise to mechanical loads on the turbine’s main components. In order to minimise the heat load on these components – thus also minimising negative repercussions on service life – the cool-down rate has to be precisely controlled. And this can be achieved only if – in the event of an unplanned switch-off, for example due to an external grid failure – there is going to be battery backup to power the standby oil pumps feeding the turbine bearings and all of the metrology and control electronics. Otherwise there’s no chance of any controlled rundown, and that will mean losses on a scale of millions.
This was the demanding, highly-crucial challenge that BENNING took on. In conjunction with Kraftwerk Obernburg GmbH – as represented by the manager responsible for electricity, metrology and controls, Mr Günther Wörner – BENNING came up with a proposed solution relying on the most modern and highly efficient components, offering the customer the required degree of future-proofing thanks to its modular equipment topology.
And it was the latter point, plus the essential need to achieve a modern level of high efficiency, that had to be seen as prime concerns for Kraftwerk Obernburg GmbH. Finally, the existing system, dating from 1996, had originally been specified in monoblock design – clearly outmoded by now.
Modular architecture offering the highest efficiency
With its INVERTRONIC compact module inverter series, BENNING supplies very safe, cost-effective, single-phase inverter systems producing high-quality electrical energy for the critical consumers, and with the maximum of reliability.
In conjunction with TEBECHOP modular rectifier systems, the net result is a very versatile, cost-effective platform for the construction of comprehensive, battery-supported standby power supplies with the maximum of availability, which is how the ICO needs it to be.
BENNING’s TEBECHOP SE product range offers a new generation of highly affordable modular rectifiers which go all the way to meet the requirements of sensitive, process-critical systems, also offering expansion to battery-supported standby power supplies if lead or nickel cadmium accumulators are combined in parallel.
Monitoring with overview; Smart controls
An impressive sight, for the operator, is this solution’s most conspicuous element: the MCU 3000 remote monitoring system with its user-friendly, 10-inch TFT display, constituting a consistent man/machine interface in the system comprising rectifiers, DC converters and inverters.
Remote monitoring can be used in addition to the use of the potential-free contacts either by ethernet, web, SNMP, MODbus or Profibus.
Using existing cable infrastructure
Maybe less conspicuous, but no less important: connection technology. In order to make it possible to avoid further use of cables routed in the far-reaching branches of the building complex, whilst also avoiding costly new installations, the specialists at BENNING placed particular priority (from the planning stage through to the implementation of the design) on a like for like layout for cable conection points.
Smooth progress management culminates in prompt completion
The entire project was completed in less than one year. Technical planning commenced in the autumn of 2022, and BENNING delivered and installed the entire power supply system on-site precisely at the beginning of the planned three-week plant overhaul at the start of July 2023. Commissioning was completed within the envisaged timeframe: 10 days before the posted closing date for the project.
Significantly enhanced efficiency
What was impressive was not just the fact of meeting the planned timeframe but also the conspicuous, marked improvement in the achieved level of efficiency – and this also provides the following benefits in terms of capacity as a fully modular, cycled system for in-house energy production: a before/after assessment of the primary feed – the 220 V rectifier system – resulted in a reduction in the amount of energy required annually of over 71,000 kWh relative to the old power supply system.
So, going forward, BENNING’s highly efficient power supply solution will not only contribute to continuous, reliable operation of the gas/steam power station in Obernburg, but will also reduce operating costs and slash the annual CO² output by approx. 26.9 tonnes.
„Due to the positive experience that we had already gained in other projects, the decision was made relatively quickly in favor of working with BENNING.“
Head of Electrical, Measurement and Control Technology,
Kraftwerk Obernburg GmbH,
Industrie Center Obernburg