Kirmaier: Biogas Gröber Ruf GmbH & Co. KG – as the name implies – is a company which generates energy on a climate-neutral basis. Using the gas generated from biomass, the customer drives BTTP (Block type thermal power station) gas motors which generate electricity and heat with a high degree of efficiency. In close partnership with local farmers, the customer – which is based in Fuchstal, Bavaria – obtains the required biomass from cultivation in the region. In addition, the customer makes use of the roof areas of its operational buildings to generate photovoltaic energy.

We have come to appreciate how future-oriented and innovative this customer is. We immediately noticed that this Company’s fundamental policy is to give priority to the sparing and intelligent use of ecologically generated power.

The Company’s affiliations include its capacity as a partner of the Fuchstal Energy Future project, which is funded by the Federal German Ministry for the Environment and Natural Conservation. Photovoltaic systems, a hydro power station, a municipal wind farm and Biogas Gröber Ruf’s biogas system have all been combined, within this project, to form an innovative energy grid that spreads across a number of communities.

The goal of logically applying renewable energy sources then gave rise to the customer’s further considerations with a view to optimisation. We were able to provide the customer with tremendous support. Previously, in phases where there was no solar radiation – in other words on rainy days or at night – the plant’s own electrical power needs in terms of operating the system were covered on a round-the-clock basis by the biogas BTTP. The power draw entailed in that context, representing approximately 9% of the generated power, was consequently no longer available to be fed into the power supply grid.

By virtue of investing in an energy storage system which provides for buffer storage of the surplus solar power generated in the daytime – and not required to cover the plant’s own needs – it was possible to achieve a significant increase in the proportion of own-generated solar power that could be used in-plant. That meant that only a residual quantity – approximately 2% of the more ecologically valuable biomass power (also available at night) – could be drawn upon to cover the plant’s own requirements.

It was possible to increase the proportion of own consumption of generated solar power to the commendable figure of 80%. And there is a further benefit from a commercial viewpoint, because under EEG (German-language abbreviation for Sustainable Energy Regulations) the biomass power feed earns higher payment than solar power does.

Kirmaier: Amongst other functions covered by the UPS system, it also provides for an increase in the operational reliability of the plant, because the sophisticated automation system consisting of sensors, evaluation computers, actuators, feed pumps and managed stirring drives could not tolerate any grid fluctuations / failures. Any fault would have given rise to considerable complications in the operation of the plant. And a worst-case occurrence would have given rise to safety-critical situations, because plant parameters such as gas pressure or volumetric levels would then have been unavailable.

In order to avoid such a scenario, a portion of the energy which is available from the batteries is not released to cover our own needs, but is kept in reserve to guarantee continued supply for the sensitive plant technology.
In the event of any grid failure, the ENERTRONIC modular Storage system – which operates simultaneously as a storage system and as a UPS – will cut in and support the reliable continuation of operation by virtue of its energy reserve.
In addition to the basic function which covers the storage and release of the climate-neutral production of electrical power, then, the system – without any significant additional costs – provides absolutely interruption-free, continued power supply to sensitive supplies should any grid failures arise. This comes in conjunction with an extended service life, since it filters out any of the grid impurities such as harmonics or transient voltages that would otherwise reduce the service life of the plant components – most of which are expensive.

Kirmaier: The outcome of the early-2020 planning & analysis phase was the requirement, on the hardware side, for a system consisting of ENERTRONIC modular Storage with 160 kVA output (4 modules, each providing 40 kVA), a BMS and a li-on energy accumulator of modular layout, with an energy capacity of 462 kWh (2 x 7 x 33 kWh). It was not viable – for financial reasons – to consider a solution with conventional lead batteries, although the ENERTRONIC modular Storage solution is also suitable for such an application. It was possible to make connection directly at the low-voltage level (400 V AC / VDE AR-N4105). This approach meant that there was no need for the plant to invest in its own transformer. The system’s design is based upon maximum availability, with redundancy. The advantages of modular architecture – such as quick & straightforward servicing, flexible scaling and modest space requirements – were as convincing as the benefits of high system energy efficiency, added safety and a quicker breakeven time.