Power Generation

Rolls-Royce acquires Kinolt: provider of stable, uninterruptible power supplies

Posted on 07 July 2020

Rolls-Royce is expanding its range of products for emergency power applications and, with effect from 1 July 2020, is acquiring Belgian company Kinolt, a specialist in dynamic, uninterruptible power supply systems for particularly safety-critical consumers. They are mainly used in data centers, hospitals or industrial companies with especially sensitive production processes.

The company, based in Liège (Belgium), employs around 290 people, has production facilities in Liège and Willich (Germany), and has service and sales offices across the world.

Momentous power supplies

Kinolt's technology consists of a combination of rotating, kinetic mass storage devices – effectively using momentum to store energy – plus a diesel engine and a generator that doubles up as an electric motor. A special control unit, a power panel and a choke complete the system. As long as the electricity flows from the public grid, it powers the electric motor which in turn drives the kinetic mass accumulator – a flywheel weighing several metric tons. In this operating state (called the Conditioning Mode) the system acts as a voltage stabilizer and mains filter (e.g. for harmonics).

If the public grid fails, the kinetic accumulator immediately takes over, driving the generator via an inductive coupling and ensuring that customer consumers continue to be fed with uninterrupted, stable voltage until the diesel engine has been started and engaged. Now the diesel engine provides the power to drive the generator, again stabilized by the kinetic energy accumulator. This operating state is referred to as the Independent Mode.


Until now, Rolls-Royce has offered MTU standby gensets only. However, these require a certain amount of time to get going. In order to bridge this and obtain power without interruption, customers often use battery storage. The Kinolt system obviates the need for this battery bank. The great benefit of an uninterruptible power supply system using a kinetic energy accumulator is that it is much more energy-efficient than one using batteries.

“With this acquisition, Power Systems is making another major stride in its transformation from an engine manufacturer to a provider of integrated solutions. With Kinolt's expertise, we are the only manufacturer able to supply our customers with all components – and thus a complete system – for uninterrupted power generation,”

Andreas Schell - CEO of Rolls-Royce Power Systems

“Kinolt has been installing our MTU engines in their systems for a long time,” said Andreas Görtz, Rolls-Royce's Vice President, Power Generation. The acquisition will now take this partnership to a new level – and Kinolt also stands to benefit. “We will integrate the products into our MTU portfolio and will now be in a much better position to offer the complete systems across the world – in regions including Asia and the US – through our global sales and service network. We expect to see a major boost in orders for Kinolt products,” said Görtz.

The Kinolt system is made up of a diesel engine that is coupled to a kinetic energy accumulator via an electromagnetic clutch. The kinetic energy accumulator is a combination of a kinetic energy accumulator and a synchronous machine. Kinolt is to become part of Rolls-Royce's Power Systems division and its MTU product and solutions brand.

Explanation for experts:

How does that work?

At its heart is a kinetic energy accumulator, a clever but simple system for storing and retrieving kinetic energy. The kinetic energy accumulator consists of two rotating parts: an outer rotor running freely around an inner rotor which is driven by the main shaft and rotates at 1,500 rpm (50 Hz) or 1,800 rpm (60 Hz). It has two sets of windings: a three-phase alternating current winding and a direct current winding.

Rotating magnetic fields and masses

In Conditioning Mode, the AC winding is energized to create a rotating magnetic field that rotates the outer rotor at a maximum speed of 3,000 rpm. However, the relative speed between the inner and outer rings of the bearings is only 1,500 rpm, since the shaft itself rotates at 1,500 rpm. The external rotor stores kinetic energy advantageously, since the amount of kinetic energy increases exponentially as the distance from the center of rotation increases.

Energy recovery

In Independent Mode, the DC winding is fed and the outer rotor is electrically coupled to the inner rotor by induction. Its kinetic energy is transferred to the inner rotor – driving it. This energy transfer is regulated by precise control of the current fed into the DC winding. The accumulator for the kinetic energy is an entirely brushless system.

Click here for the press release on this.

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