Principle of the technology


The heat2power proprietary concept is based on requirements that we have identified as mandatory in the environment of automotive mass production. Study of more than 40 different waste heat regeneration technologies led us to develop this concept because all other concepts had inconveniences or even unacceptable properties. The main characteristics of an automotive WHR should in our opinion be :

We have indeed come up with a system that combines all these requirements. We are therefore convinced that it has a strong market potential. We had previously also investigated alternative systems currently in the market or being developed and found their main inconveniences :

When we understood that the inconveniences of the existing technologies would really be big hurdles for the industrialisation of a WHR system in the automotive industry we focussed on system simplicity and low cost. Not for optimal thermal transfer properties. This is why we based our system on air. Though it is not the best working medium for thermodynamic cycles, its abundance in nature, its compatibility with the lubrication system and known behaviour in engines are true advantages. What we have come up with is discussed below.

Introduction to the heat2power concept

In our quest for better fuel efficiency we have decided to let others work on the improvement of the combustion. However when studying the total power flows in an engine we judged that there was some potential of reduction of waste heat power flow. In parallel we worked out several ideas and did a technology survey on Waste Heat Recovery (see the Benchmark section on this website). Our experience in the automotive industry gave us the conviction that a system should have a low level of required investment to be industrialized. Otherwise bringing the system to the market would be most difficult, even if fuel consumption reduction is important.

The heat2power system is based on the use of one or more cylinders for the regeneration of waste heat. These cylinders can be in replacement of the combustion cylinders inside an existing engine or as an add-on module that is connected to the engine by means of a gear set or a belt drive. Also is it possible to have no mechanical linkage between combustion engine and regeneration unit in case the power from the regeneration unit is taken off electrically. In general for low cost of installation and development we recommend OEMs to use an add-on system. In that way the original engine remains basically unchanged.

The thermal power is extracted from the exhaust of the internal combustion engine by means of a heat exchanger. This is a gas-gas heat exchanger operating at high temperatures: up to about 950°C. Basically the heat2power system works like most other thermodynamic cycles : intake and compress a gas, then heat it up and finally let it expand. The difference between an ICE and the heat2power system is that the heat input is not by combustion inside the cylinder but by heat exchange external to the cylinder.

After the expansion stroke the air is released at low temperatures (250-300°C instead of 600-950°C). This can also be considered as an advantage for military vehicle that require a low thermal profile.

The heat exchanger in the exhaust is placed after the catalyst (gasoline vehicles) or after the particle filter (diesel vehicles). In such manner the exhaust gas after treatment remains unaffected and the combustion engine does not need its tuning to be done all over again. However we recommend applying thermal insulation of the exhaust manifold and the first part of the exhaust and catalyst/DPF so that a maximum amount of heat is available for the regeneration process.

The layout of an add-in system and the associated power flows are represented in figure 1:

System layout of a heat2power ADD-IN configuration and its power flows
figure 1 : System layout of a heat2power ADD-IN configuration and its power flows

The regeneration device is made of :

Any fuel used in the combustion process of the "combustion cylinders" that generates heat is compatible with heat2power.

The heat2power system is a machine that works with heat only. It does not need any fuel. It can therefore also be applied in the fields of solar energy and geothermal energy as an alternative to the Stirling engine as well. The heat2power engine works with 5 (4) strokes (3 (2) strokes is possible), has the same RPM limitation as the IC engine, and operates with a good efficiency and with relatively high specific power.

More information will be made available soon. Feel free to contact us for more details.


Once we have established a confidentiality agreement between heat2power and your company we can transmit to you a more complete document. This explains in detail the following topics:

- Waste heat power flow of an IC engine
- Introduction to the heat2power concept
- The heat2power thermodynamic cycle
- The heat2power engine warm-up process
- How the pressure increases in the heat exchanger
- Limit and convergence for the heat exchanger pressure
- Theoretical P-alpha and P-V diagrams with a converged system
- Major steps of the heat2power cycle (with a converged HAC pressure)
- Theoretical heat2power efficiency principle
- The heat2power hybrid engine configurations
- The heat2power machine in a simulation model

- Performance predictions of the heat2power hybrid engine
- Potential heat2power’s performance improvements
- Various proposals for layouts in a road cars, race cars, trucks and powergeneration
- Conclusions