Breakthrough technology in waste heat re-cycling

Edited by the Engineeringtalk editorial team Jul 31, 2001

Scram Technology has been appointed to market and licence a breakthrough technology in waste heat re-cycling that promises up to 10% reduction in energy used in engines, motors and fuel cells

Scram Technology announces that it has been appointed to market and licence a breakthrough technology in waste heat re-cycling that promises up to 10% reduction in energy used in internal combustion engines, electric motors and fuel cells.

The efficiency of most engines and motors is poor.

70% of the available energy in the fuel of a petrol internal combustion engine is lost as waste heat.

Diesels lose 60%.

Electric motors more than 5%.

Accurate efficiency figures for fuel cells are not yet available but are reportedly more than 40%.

The only technology currently available to use this waste heat is turbo compounding, which uses a turbine in the exhaust to recycle energy to the output shaft of the engine.

Scania launched a turbo compound 12 litre truck in February 2001, but the cost of the system will confine application to very large trucks.

John Hammerbeck, the inventor of the periodic belt drive, has applied for a patent combining the known principle of thermal belt engines, with any waste heat producing engine and a periodic belt drive.

This combination increases the power output of the total system and so reduces fuel consumption.

Improved economy is achieved by the thermal engine piggy-backing on the output of the conventional engine by making the output of both concurrent.

This invention is important for electric, hybrid and fuel cell vehicles because waste heat production increases when power demand rises, for example when ascending a hill.

The invention is not limited to vehicle use but can save energy wherever motors or engines are employed.

John Hammerbeck said "It won't be enough to save the planet, but it will be an important tool in reducing greenhouse gas emissions." Thermal engines that use thermally deformable memory metals or bi-metallic strips to turn low grade heat into useful rotational work are much researched but have produced no generally useful products because of cost, low rotational output speed and difficulty in starting.

Previous technologies in this field, for example, US Patent 04150544 (Pachter 1979) and US Patent 4246754 (Wayman 1981) essentially use a thermally deformable belt running round pulleys.

Heat is applied to the belt on one side of the system causing it to contract and deliver rotational force to the pulleys.

As the belt circulates the heat is dissipated and the belt expands on the other side of the system.

Hammerbeck combines this idea with a periodic belt.

The periodic belt system is a new way of changing speed/ratio hailed by Industrial Technology magazine in February 2001 as "possibly the most significant development in speed control since the brake".

Previous methods of ratio changing use the interaction of different circumferences of cogged wheels or pulleys, for example stepped gears as in manual and automatic vehicles, the van Doorne CTV and the Torotrak IVT.

Periodic belts are elastic and circulate in a fixed time however much they are extended.

If the belt is extended or contracted, overall or locally, any output pulley over which the belt runs will change speed.

Periodic belts drives are cheaper, lighter and more efficient than gears and provide wide continuously variable ratios.

Engines employing periodic belt transmissions can easily be converted to use waste heat by simply using a thermally deformable belt and directing waste heat at the belt in its pulling phase.

Any heat absorbed by the belt in the pulling phase of its loop and transported and dissipated on the return phase will result in increased torque on the output pulley.

At high belt circulation speeds the effect may be slight because of the low rate of heat transfer between ambient air and the belt, but at lower speeds such as in stop/start city traffic or climbing hills there will be a significant increase in power delivered and consequent fuel saving.

This contrasts with turbo compounding which is only effective at high engine output.

This concurrent drive technology is not limited to the main engine in a vehicle.

The waste heat may also be directed at belts driving subsidiary systems such as alternators and air conditioning compressors.

These systems now consume a substantial part of the energy output of the main engine.