Throughout the construction industry, there is a need to make machines safer, more energy efficient and to reduce their emissions.
Despite that, many of the heavy-duty machines have demanding work cycles, meaning they cannot embrace full electrification. Instead there needs to be a hybrid solution - but with two options available in EHA and EHP, which one will provide the most benefits?
Power-on-demand with electro-hydraulic pumps (EHP)
EHP stands for Electro-Hydraulic Pumps. They work in a similar way to a conventional system but without any internal combustion and are controlled by a high-performance mobile hardened drive. Working to save expenditures rather than recovering energy, they use power on demand in addition to working under various pump and unit speeds.
- Using power on demand helps to reduce fuel consumption by between 5% and 20%.
- Noise is reduced thanks to the power-on-demand feature which allows for the EHP to turn off when not in use.
- EHP systems can incorporate recovery as long as the system is designed so that the load can drive back the EHP to work as a motor and a generator. If so, the system can charge the battery itself.
- Quick and easy product selection. Only three parameters are required to select the right EHP specification for the application:
- Battery Voltage
- EHP is very similar to the conventional system, meaning it does not necessarily represent a big departure from current methods.
- Suitable for upgrading machines presently but is perhaps not a long-term solution.
- In order to go further with the changes, EHA may prove to be more efficient - although that does depend on the life cycle of the machine.
Saving and recycling energy with Electro-Hydrostatic Actuation (EHA) Systems
EHA stands for Electro-Hydrostatic Actuator systems and has been earmarked as a potential solution of tomorrow. Currently being used within the aerospace industry, EHA systems work without valves, so that every function of the machines are dependent on each other. As a self-contained hydraulic system, it integrates one cylinder and a single feedback unit. There is also one servo motor and one variable speed pump as well as a single electric drive. Compact and highly efficient, EHA systems only need an electrical connection in order to work.
- No conventional valve control, meaning energy losses dramatically decrease.
- Reduces fuel consumption by up to 50%.
- Compact system helps to reduce the overall weight of construction machines.
- EHA means fitting a new system and it cannot be retrofit to any current construction vehicles.
- Must be adopted in the design stage when creating new construction machines.
- A huge step forward in technology - meaning set-up costs will be substantial.
Both EHP and EHA represent a step forward from the way construction machines currently operate. For most construction machine manufacturers, the determining factors when it comes to deciding between EHA and EHP will be the type of application and the duty cycle.
How far the manufacturers are looking into the future could also be considered. There is no doubting that EHP is the easiest option. It makes product selection simple, it is cheaper than EHA and it can be fitted to existing systems.
EHA, on the other hand, is likely to result in significant costs. It represents a complete departure from the conventional system and cannot be retrofit to current construction machines. As the aerospace industry has proved, however, EHA drastically reduces weight and provides much better efficiency than EHP which results in significant fuel savings.
This article was contributed by Björn Eriksson, Senior Systems Engineer and Adrian Butler, Industry Market Manager