Turbine Generator Captures and Re-uses Wasted Energy

Efforts to harvest energy typically lost during production operations are increasingly becoming a key facet of sustainability projects at a number of industrial facilities worldwide. Many of these projects focus on energizing low-power devices, such as sensors, through capture of wasted energy from vibrations or heat dissipation. While these projects are intriguing and admirable, significant amounts of energy released by industrial systems remains untapped for regenerative purposes or for companies to sell back to power utilities as a means of offsetting energy costs or generating revenues.

In an attempt to address this issue, the German Federal Ministry of Economics and Technology is funding a project at Deprag Schulz GmbH & Co. (www.deprag.com) to capture excess process gas for energy generation. Of course, energy recovery from excess process gas in not a new idea, but this project at Deprag Schulz differs from other such energy capture applications in that it involves converting small amounts of residual energy (5 -20 kilowatts) directly into electricity using a small generator.

When Deprag Schulz embarked on this project, engineers at the company could not find a standard generator small enough or that employed suitable materials for use as the core of this new energy generation device. To be effective in this application, Deprag Schulz engineers calculated that the rotational speed of the generator would need to be around 40,000 rpm. This realization led the engineers to design an electric turbine generator based on a permanent magnet synchronous induction machine for the generation of electricity.

The prototype from Deprag Schulz is a compact unit made from a microexpansion turbine with an electrical generator that produces electricity from gas. The core turbine generator unit, not including the electrical control box, is not much bigger than a shoebox and can be used locally where gas is either released unused by the industrial process or where a high level of pressure is reduced to a lower value.

Here’s how the turbine generator works: Gas flows into the turbine and is pressed through jets to accelerate its movement. When it meets the blades of the turbine and is diverted, it releases energy. This kinetic energy is then converted to electrical energy in the generator.

The key to the design of this prototype is that the turbine and electric generator have one shared drive shaft. This means that, when the turbine rotates, so does the generator’s rotor, enabling electrical energy to be generated.

To help visualize how such a turbine generator could be applied in an industrial setting, consider the tanks used in the smelting of metals. These tanks are typically cooled by compressed air. The compressed air flows through cooling channels and absorbs heat. Typically, this air is then released into the atmosphere without being used. With the turbine generator, the energy absorbed from the heat can be converted into electricity by passing it through the microexpansion turbine and the integrated generator and then feeding the resulting power back into the grid.

Deprag Schulz
www.deprag.com