In this uncertain economy, the need to constantly maintain and lower operating costs has become a necessity for construction industry. Also, In order to adhere to pollution and regulatory standards and to control costs, the construction industry has started demanding a higher fuel efficiency of the equipment that it uses in its day to day operations. The big challenge here is this must be done without compromising on productivity and reliability of the machinery.
For example, one of the biggest fuel guzzling machinery being used on a construction site today is the excavators. An average hydraulic excavator has a highly inefficient engine and hydraulic system with a fuel efficiency of just about 20%. While searching for reasons, the experts in the field found that there is a huge loss of energy during low gear conditions by the way the relief valves function when the operator is trying to swing the arm for use and during braking & idling. Also, the power drive train of these excavators also run hot and needs energy to cool itself which also contributes to higher fuel consumption.
So, by taking the challenge head on, researchers found that this can be improved only with improving the quality of the valves and the transmission mechanism. They found that just not the parts but the entire final drive train needs to be given a hard look and this has finally led to the advent of hybrid power drive trains which are not just efficient but are economical too.
What is A Hybrid Power Drive Train?
A Hybrid power drive train consists of a power generator, ultra-capacitors and batteries which are linked to the hydraulic systems which drive the vehicle, the boom, the arm etc. The capacitor acts as an energy aggregator. The electric system can be connected in parallel, in series, or compound. A hybrid power-controller manages the entire process of power and energy transfer between the mechanical and the electrical systems.
How Does The System Work?
During low load operation, the power generated by the engine is distributed by the power-controller between the hydraulic system and the capacitor. During braking, the system recovers kinetic energy from the deceleration process of the swings and stores it in the capacitor.
During a high load operation, the power controller pulls energy from both the engine and the capacitor acting as the “load levelling device” to reduce the load on the engine. Also as the load picks up, the hydraulic-system needs more torque, so, this additional work load on the engine is reduced as the stored energy is used as “transient torque assist” and it evens out the engine from functioning. This stored energy can also be used to swing the arm and boom, to run the motors for low energy work such as inching and moving short distances. This helps smooth the arm and boom functions. It can also be used to run the electrical system such as the lights and cabin cooling.
This entire system also generates lower heat as most of the heat is converted into stored energy, thereby reducing the need for cooling systems. It also reduces the pollution especially CO2 generated.
What Is The Impact of These Hybrid Power Drive Trains?
Studies have shown that the hybrid power final drive can improve the fuel efficiency of excavators from anywhere between 20-40%. This means that even with the slightly higher prices of the hybrid excavators, an operator could get back the investment in less than a year.
Hybrid final drives are really a boon to the construction industry which is grappling with multiple issues and further research in this field is well funded by big companies in this industry.