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Case study

Energy-saving biogas cleaning with AC drives

A new technology for energy-saving biogas cleaning has been awarded the Skapa 2010 innovation prize. Farmers can now save money and the environment by producing their own vehicle gas on their farms using farm waste.

[3 February 2011]

Per-Olof Karlsson is the name of the inventor who has been awarded with the Skapa 2010 innovation prize and a EUR 30,000 grant. He has developed a new technology that upgrades biogas to vehicle gas in an energy-saving and cost effective manner. Many farmers have their own digesters which convert manure and crop waste into biogas, but expensive equipment or costly transportation to central facilities is required to upgrade it to vehicle gas. This upgrade process can now also take place directly on farms at a low cost. The cycle is complete when farm vehicles are powered using renewable fuel produced from farm waste, and any surplus can be sold for a profit.

Energy-saving process with patented technology

Biosling is the name of the biogas facility that took almost six years to develop. It offers all the functionality required, integrated into a mobile system. Its modular design makes it easy to modify to meet demand. In traditional facilities, the process takes place using energy-intensive compressors. Using the new patented technology, the gas and water are instead pumped in turns into a rotating hose reel. Gravitation pushes the substrate in towards the centre and carbon dioxide is discharged into the water when the pressure increases. Methane levels increase while the gas is purified from unwanted sulphur and nitrogen. Vehicle gas corresponding to almost 1,500 litres of petrol can be produced every day.

Energy saving biogas cleaning Biosling

Photo: Artic Nova

AC drives adapt motor speed to demand

Three Emotron FDU AC drives from 1.1 to 7.5 kW control the motors and guarantee reliable and effective operations. Emotron VFX is used to maintain constant torque in the hose reel, with up to 150 percent starting torque at zero rpm. IP54 classified metal enclosures offer easy and disturbance-free installation. Emotron's distributor Kjellstedt Consulting developed and installed the drive solution.

"This is the most energy-efficient solution available on the market for small-scale facilities”, says Lars Kjellstedt. “Our figures show that only half the electrical energy is required for each produced unit in comparison to traditional systems. The AC drives used to optimize motor speeds are of course a contributing factor.”

There has been great interest, and Per-Olof Karlsson's company, Artic Nova with eight employees, has begun producing the first cleaning facilities.

"In Sweden alone, there are 3,000 farms that would benefit from investing in such a facility", says Per-Olof Karlsson. "The next step is to test the method on landfill gas where methane gas levels are even lower."