Our world is constantly under construction. From sprawling cities to projects in the most remote corners of the planet, we are building the future. But as the world’s population swells, so too must our concern for not just what we are building, but how we are building it. The challenges of working safely, working to limit our impact on the environment and working more efficiently, exist regardless of the climate, terrain or local politics. Finding solutions that can be applied irrespective of the city, country, continent or climate must be the mission of construction companies as they transition from not just doing a good job, but ensuring the energy and environmental impact of their work is reduced to a minimum.

One specific area of concern is noise and emissions from construction machines. Historically powered by fossil fuel, normally diesel combustion engines, there is growing pressure for them to switch to cleaner, quieter alternatives. While the technology to enable pure battery supplied electric power for smaller construction machines is available and being adopted now, for larger machines with greater and multiple demands, the capabilities of pure battery supplied electric power are not yet at the necessary level. That means that good hybrid solutions are needed to lessen the dependence on fossil fuel power.

Blueprints for an office park, a public garden, a library or a school are usually met with enthusiasm at civic meetings. When it comes to constructing such properties in cities however, the reaction is considerably colder.

Construction sites in urban locations could also face future challenges. It is anticipated that legislation will come into force to tackle the problems of noise pollution and exhaust emissions. To be fully compliant, it is vital that the construction industry takes action to address these issues sooner rather than later.

The answer for many construction machine manufacturers has been electromobility - fully electric or hybrid implement and traction systems which utilise electric prime movers or diesel-electric hybrids to replace noisier, less environmentally friendly fuel systems.

There have already been great strides made with smaller machines such as forklifts that are 100% powered by electricity. What were once noisy, polluting, gas-guzzling vehicles, are now smaller and operate with zero local emissions at whisper-quiet decibel levels. Their lack of emissions also means safe operation is possible both inside and outside.

When we get to heavy-duty machinery however, there are still plenty of challenges to be overcome. Powered by fossil fuels which produce carbon gas emissions, heavy-duty machinery cannot be powered by electricity alone because of its demanding work cycles. That means hybrid solutions need to be explored and adopted. The good news is that battery technology is starting to evolve and improve with greater outputs and longer duty cycles possible without impacting overall size and weight; this makes it more likely that even larger machines can become fully electric. Some types of machinery are also possible to feed directly from the electric grid. This challenge runs the breadth of the industry, beginning with the machine builders and original equipment manufacturers (OEMs). Thankfully, there are currently three potentially viable hydraulic solutions which represent a good fit for electromobility.

Power-on demand with Electro-Hydraulic Pumps (EHP) aka ePumps

The Electro-Hydraulic Pump (EHP) is very similar to a conventional system but works without an internal combustion system. Instead it uses an electric motor which is coupled with a hydraulic pump, controlled by a high-performance mobile hardened drive. Designed with diesel-electric hybrid and all electric mobile applications in mind, the most popular EHP does not recover energy, it saves expenditures by using power on demand as well as operating under variable pump/motor unit speeds. In typical applications, this allows the EHP to reduce fuel consumption by 5%-20% when compared to a standard load sensing (LS) system. Additionally, EHP systems reduce both emissions and noise level during use. The greatest contributor to noise reduction however, is the power-on-demand feature which allows the EHP to turn-off when it is not in use.

Depending on the application, it is also entirely possible to incorporate recovery in some EHP systems.

If the system is designed where the load can back drive the EHP and work as both a motor and a generator, it can then charge the battery itself.

Saving and recycling energy with Electro-Hydrostatic Actuation (EHA) systems

While EHP can be thought of as the solution of the present, Electro-Hydrostatic Actuator (EHA) systems could be seen as the answer for tomorrow. Deciding on the type of application and duty cycle in use are the biggest determining factors in whether to use an EHP or EHA system. Initially employed in the aerospace industry, every EHA is a self-contained hydraulic system which integrates a single cylinder, one feedback unit, one variable speed pump, one servo motor, one electric drive and the control electronics into a compact setting that only requires an electrical connection to work.

There are no throttling valves involved in the EHA systems, meaning every function of the machine is independent of the others.

Each function has its own pump which is used as a motor when recovering energy. By removing the conventional valve control, energy losses dramatically decrease, making the system much more efficient. It is estimated that EHA can reduce a machine’s fuel consumption by up to 50%.

There is however a downside to EHA technology. It cannot be retrofit to any current construction vehicles; it can be used only when creating new machines. Unlike EHP, EHA represents a huge leap forward in technology as well as a complete departure from the way things have been built in the construction industry for decades. That does not mean it should be ignored, and as the cost of this technology decreases, EHA is set to become much more relevant with new build machines coming online.

Combining EHA and EHP

A lot of applications have several implement functions. With so many functions within any given application, the use of power can fluctuate substantially. When it comes to these applications, the best resolution is usually to create an entirely custom solution that uses a combination of EHA and EHP. For example, the most power consuming functions with energy recovery can utilise EHA while an EHP system operates the rest. There are also plenty of solutions where cross-talk between EHA channels can be used.

Motion Systems