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nilsinside AB proudly presents
the Revolution Energy Converter - the REC

nilsinside revolution
nilsinside revolution


The technology behind the REC

Simple concept, amazing potential

The technology behind the REC has a simple concept yet so innovative and powerful. The REC is an active heat exchanger which transforms a part of the heat to pressure pulses of a desired frequency. These can be used different ways to generate work (connecting to a piston engine, a turbine, a pump, an electricity generator…).
In thermodynamic terms, the REC acts as “a closed system with a moving boundary” that transforms an existing given temperature difference into kinetic energy which can connect to an electric generator.

Today's external heat engines are very limited in power due to small cylinder volumes. At nilsinside we have solved this by using very large heat transfer areas, allowing much larger cylinder volumes which can benefit from lower temperature differences and be built for much higher output power than a conventional engine.

Here’s the technical explanation

The REC is a closed system that heats up and cools down a large sliced volume efficiently, fast and repetitively, resulting in internal pressure changes.
The illustration below shows a cross-sectional view of the REC and its internal parts.



An inside view of the REC with the hot and cold blocks and their respectively conducting fins in red and blue, and the electric operated RS in brown with the quarter openings which contain the slices of volume. The hot and the cold blocks are separated by insulating nil blocks in transparent beige. The second nil block (placed opposite) has been removed in order to see the RS opening.


The closed REC uses an internal “Revolving Shutter” (RS), a pack of discs, to move the sliced gaseous volume column which is held within a quarter of an opening called the Work Generating Volume (WGV). The RS rotates the WGV between the conductive fins of a hot and a cold block where they heat up/cool down quickly. This results in internal pressure changes. Note that these are thin slices with large area as they heat up and cool down faster than thick volumes.

To prevent unwanted efficiency leaks, the REC contains two “nil blocks” with insulating fins placed in-between the hot and the cold blocks. These insulating blocks prevent the simultaneous heating up and cooling down of a part of the same volume.

The RS is not in contact with the fins and is free wheel turned by a controller with logics and an electric stepper motor. Although the purpose of the RS is only to move around gas, it must be constantly controlled. This is done by the “Revolution Dynamic Link” (RDL). The RDL software continuously adjusts the RS speed according to input from the running application. It’s designed for variable speed as well as a varying work load.

Here’s how the REC works, step by step:

1. The Revolution Dynamic Link (RDL) positions the opening of the RS to overlap with the hot block of the REC

2. Heat-transfer from the hot fins into the slices of gaseous volume (WGV) takes place

3. The internal pressure of the REC rises and forces the piston to move a given distance

4. The RDL turns the slices of the work generating volume to the fins on the cold side, where they will dump their heat

5. The internal pressure drops and the piston returns to its original position, i.e., pushed back the distance. The process restarts from step 1.

Still a bit of a blur?

Check out the video animation of the REC cycle:

The work generating volume (WGV) is formed between the fins and the open quarters in the revolving shutter (RS). All the open RS segments, the WGV, is part of the total volume. The pressure distribution of the total volume is used to generate power - in the example in the video above this is done by connecting a piston or a membrane. The REC can be used in series to generate more power output.

What makes it so much better than conventional engines?

Theoretically the REC can be compared to a Stirling engine (which alternately heats and cools a closed working volume and convert the pressure / volume changes to work) but the Sterling engine is very limited in power.
Important differences between the REC and conventional heat engines are:

  • it delivers ready made alternating pressure pulses opposed to one-way pressure

  • it’s not limited to steam and can benefit from lower temperature differences allowing the recovery of £millions worth of waste heat on a large scale that no other technique is able to acheive,

  • Its power range is significantly higher and varies from a few kW to several MW – a Sterling engine’s max output is generally less than 100kW!

  • It’s more cost efficient due to the simple dessign and therefore lower manufacture cost,

  • it has a large power range compared to other engines that are limited in size and do not scale,

  • It has a unique ability to change the thermodynamic cycle on the go,

  • It has a revolving shutter with a unique ability to change the convective heat transfer coefficient (htc) to optimal ratio. The convective htc for a turbulent flow is relatively high compared to a low coefficient of a laminar flow!


Nilsinside’s technology innovation is unique and the Intellectual Property associated with the REC model has been registered. Currently the IP has been approved in Sweden, China and the US.

Click this link to read: The Revolution Energy Converter Explained

Link to the REC Explained in pdf format: RevolutionEnergyConverterExplained.pdf

Link to frequent protyotype questions in pdf format: QuestionsAndAnswers.pdf

updated by KITS