Shuttle bearing with energy recovery

Bergzeit offers its customers a wide range of products for mountain sports. The company is based in Otterfing near Munich in Upper Bavaria. The mountain sports outfitter was founded in 1999 as a classic start-up with an attic store. In the beginning, founder Klaus Lehner provided tour information on the Internet and came into contact with many people via the tour portal. This resulted in more and more requests for equipment. Bicycle computers laid the foundation for online sales. In 2001, the online store "Bergzeit" went live. In 2003 and 2010, branches were opened in Großhartpenning near Holzkirchen and in Gmund am Tegernsee. In 2017, the new Bergzeit head office building with logistics and administration building was opened in Otterfing near Holzkirchen. As the capacity limit was soon reached, the management decided to build a new automated shuttle warehouse in 2020.

After completion of the extension, Bergzeit had the racking system installed by a service provider. PSB intralogistics then installed the shuttles. "In addition to efficient logistics processing, the shuttle warehouse needed to be energy sustainable," reports Holger Cecco-Stark, Head of Facility and ECO Management at Bergzeit. One requirement was therefore to feed the braking energy of the lifts back into the grid.

This is where drives with regenerative units from SEW-Eurodrive came into play. As the new high-bay warehouse is an energy-intensive system, a new transformer was also installed. The automated warehouse was completed in 2022. It comprises 54,000 storage locations in seven identical aisles. There are eight shuttles in each of these, which can be moved freely between levels. "We work with triple-deep storage in the aisles," explains Cecco-Stark. "So where the shuttle stops, it can serve six storage locations."

Lifter with strong acceleration

In this high-bay warehouse, two lifts are installed at the front and two lifts in the middle of each aisle. These shuttle elevators are moved by CMP112 M synchronous servomotors with KA77B bevel gearboxes from SEW-Eurodrive. The geared motors accelerate the lifts to a maximum speed of 5 m/s at 7 m/s2 . Because the four 32 A modules of the frequency inverter are combined into a group on the DC link, they can exchange energy with each other via this connection. A warehouse management computer coordinates the movements of the shuttles and lifters and prevents collisions. For example, if one lifter is at the top, it can only move down if the other lifter is at a lower position. When the lifters are braked or lowered, the kinetic energy is converted back into electrical energy.

At the customer's request, sinusoidal regenerative modules were used. Klaus Kröner, application engineer for regenerative power supply units at SEW-Eurodrive, supported PSB during the first field tests of these units. The plant manufacturer from Pirmasens, a long-standing partner of SEW-Eurodrive, was one of the first users of these regenerative power supply units. Together with a control technician from PSB, SEW-Eurodrive's service department optimized the control of the sinusoidal regenerative units and implemented energy meters. The current motor or lowering generator energy flow is measured via this digital interface. The regenerative units are equipped with IGBTs that clock at 12 kHz. A low-pass filter choke prevents the 12 kHz clock frequency from reaching the mains. If there is no travel order for the lifts, the regenerative power supply is blocked after one minute in order to avoid standstill losses. The Movidrive MDR90B sinusoidal regenerative power supply is designed for 50 kW supply and regenerative power with 2.5 times the peak power. Like the frequency inverters in the Movidrive modular series, it is part of the Movi-C modular automation system.

Sustainable energy supply

Bergzeit attaches great importance to the environmentally friendly use of resources. As part of its strategic orientation, the company has developed an energy concept that has been established in almost all areas of the company and is being further expanded. Since 2020, the company has been validated in accordance with the European environmental management system EMAS. The Eco-Management and Audit Scheme ensures that all environmental aspects, from energy use to waste and emissions, are implemented in a legally compliant and transparent manner.

Bergzeit installed a photovoltaic system on the roof for the power supply. In order to be future-proof, the company chose the maximum possible design. "Today, we produce around 550,000 kilowatt hours per year," explains Holger
Cecco-Stark. "We want to completely dispense with fossil fuels here at the site by 2030." The company also acts sustainably when it comes to its company car fleet

Clean electricity at a low price

The photovoltaic system produces up to 550,000 kWh of electricity per year and is certified according to the Guarantee of Origin Register (HKNR). This allows Bergzeit to generate and sell green electricity itself. After supplying the demand at the Otterfing site - for example the 20 company-owned charging stations - the company feeds the remaining yield, or around 40 percent, into the power grid.