Hybrid public works machines to protect the environment

In the beginning hybrid engines were developed by automotive industry but today hybrid engines have the wind in their sails for public works machines. Manufacturers pay a special attention to reduce the consumption of their machines and to pollute less. A necessity, knowing that the taxation project of CO2 emissions goes on and Tier 4 antipollution regulations are evolving.

More workable hybrid machines for public works

The operation is the same: kinetic energy recovery, storage, than restitution.

However, the difference with the automotive industry is remarkable. Indeed, public machines manufacturers are more searching for quick electric power to relief diesel motors than for high capacity of energy storage.

To get this result, they use super condensers. Their operation is based on electrons and ions migration for charging and discharging. The power transfer is carried out faster than from batteries producing power from chemical reactions.

For example, for a hydraulic excavator, the energy recovered can come from braking or turret rotation. Thanks to this available power, hybrid machines are more workable: improvement of starting torque, maneuver flexibility, etc.

Up to 40 % fuel saving

In 2008, the Komatsu manufacturer presented the first hybrid excavator in the world. It worked as follows: the turret rotation hydraulic engine is replaced by an electric motor-generator unit. At every braking of the turret, this system recovers kinetic energy that is then returned at the next turret rotation in the form of electrical energy.

This hybrid excavator allowed to reduce CO2 emissions and to reduce fuel consumption by 25% compared to a classic excavator.

Caterpillar developed a hybrid hydro-electric technology, whose principle relies on power storage in the form of pressurized oil.

Latest generation models grant a reduction in fuel consumption that can reach 40% depending on their use. Besides, hybrid machines contribute to a significant reduction of noise pollution on building sites.

These developments step in the right direction and future technologies will certainly evolve according to the limits set by futures anti-pollution regulations.

Electric and fire risks to fear?

New technologies may complicate machines maintenance as it will require certified technicians and it will also be crucial to think about electric and fire risk due to the presence of Lithium batteries (reliability, short-circuit and overloading resistance, etc.). However, it is too early to talk about these points.

In the automotive sector, many rumors had circulated about the dangerousness of certain models. The presence of a high voltage battery originated explosion or fire risks. These risks dissipated through years and hybrid models are nowadays among the safest vehicles of their category according to some rating institutes.

Even if some construction machines are very exposed due to their environment (thermal shocks, vibrations, humidity) hybric technology has undeniably a great future ahead in this field.

It remains to improve the storage capacity of future batteries in order to go beyond current technological limits and perhaps to see on the market 100% electric vehicles.

Besides, it seems that a manufacturer is already working in his French plant on a prototype of a mini excavator using this type of technology …


Nicolas Arnaud, Energy Loss Adjuster

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