Many of these projects involve energizing low-power
devices, such as sensors, through capture of wasted energy from vibrations or
heat dissipation. But that still leaves a massive amount of energy being released by industrial systems that remains uncaptured for greater use.
To help address this, the German Federal Ministry of Economics and
Technology is funding a project at Deprag Schulz GmbH & Co. (a supplier of
air motors) to capture excess process gas for energy generation. Of course,
energy recovery from excess process gas in not a new idea, but Deprag Schulz's
new project does add a new twist. The Deprag Schulz project involves converting
small amounts of residual energy (5 to 20 kW) directly into electricity using a small generator.
Because no standard generator was small enough or employed suitable
materials for use as the core of the energy unit (calculated rotational speed
of the generator is around 40,000 rpm), Deprag Schulz had to
develop an electric generator specifically for this purpose. The result is a 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 which 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, the generator's rotor rotates at the same time and electrical energy
As an application example for this turbine generator, the tanks used in
smelting of metals are 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 to electricity by passing it through
the microexpansion turbine and the integrated generator and then feeding the
resulting power back into the grid.