Mixing it up with VFD technology to create environmentally friendly renewable energy

03 November 2022

Biogas production in Greece is on the increase thanks to PK Energy, a specialist in the construction of electricity production units from renewable energy sources, and the use of Optidrive variable frequency drive (VFD) technology from Invertek Drives.

The company has already completed several biogas systems using animal effluent and vegetable waste to produce the gas through anaerobic digestion which in turn is converted into electricity.
The animal and food waste is broken down into microorganisms within two special oxygen free storage units, where pumps ensure the right quantity of material is fed into them before being mixed to help create the gas.
The gas is converted into electricity when it passes through two on-site cogeneration units. These generators create 3MW an hour. The electricity is then fed into the mains grid.
Each of the pump and mixing processes uses Optidrive E3 VFDs. These are specifically IP20 enclosures, 3PH, 4kW up to 37kW VFDs.
The overall project was undertaken by PK Energy who worked with Automation Experts on methods for pumping the animal and vegetable waste into the reactors, as well as the mixing process using the VFDs.
Theodore Amiridis, technical director at Automation Experts, said the 18 Optidrive E3s used were an integral part of the overall project and ensures the optimum amount of gas is created through controlled pumping and mixing. He said: “The whole process relies on pumping and mixing processes, each requiring the VFDs to accurately control the amount of waste going in and out and the speed of the mixing during the process. Material is pumped into tanks one and two where it is mixed to produce the gas.
 “After some time, pumps are then used to transfer the material from these tanks into a third one where it will undergo centrifugal treatment, also using the E3 VFDs.”
The Optidrive E3 VFDs are used to control the mixers and pumps using PID functions to ensure the accurate flow and mix of the material depending on the material.
“The Optidrives are easy to install and commission, as well as being easy to programme. Every drive was connected with PLC through Ethernet/IP protocol. The VFD PID function was used on the pump control. The whole process, combined with our expertise, ensured the optimum levels of gas were produced by ensuring the correct motor and pump speed,” added Amiridis.

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