This is how hydraulics becomes efficient
 Hydraulikaufzüge sind energieeffizient und zukunftsorientiert

written by Michael Pyper on Monday, October 18, 2021

The times when elevator hydraulics were considered energy guzzlers are long gone. Depending on the constraints and the techniques used, elevator hydraulics even beat the traction lift in terms of sustainability.

How does it look in hundreds of thousands of apartment buildings? They have a maximum height of 15 meters (49 ft.) and up to five floors. According to VDI guideline 4707, a standard passenger elevator can carry up to eight people at a speed of one meter per second. The service life of such elevators is at least 20 years, sometimes 40 years and more.

These are the key data for exciting investigations by the Spanish technology center 'Instituto Tecnológico de Aragón’ (Itainnova) and the Swiss Federal Office of Energy - with astounding results. From a holistic perspective, the hydraulic drive system is more sustainable for typical apartment buildings than a machine room-less traction drive system. The consumption of resources during the whole lifespan is noticeably lower than the environmental impact of the manufacture, installation and disposal. And after 20 years a partial modernization is ecologically much more sustainable than the complete replacement of a hydraulic elevator.

About frequency inverters, intelligent valves and Supercaps

It's nice to read this scientifically established in black and white. Of course, behind all this lies a lot of development work and know-how, such as energy-efficient valves, frequency inverters for demand-matched power consumption, or Supercaps that do not let energy produced during downward travel simply go to waste.

Bucher Hydraulics is a long-time member of the VDMA BlueCompetence initiative. Under the motto ECOdraulics, the company has committed itself to developing and manufacturing products with a particular focus on energy-savings, low-emissions, long life, low weight and space-savings. The intelligent hydraulic valve ‘iValve’ is such a product. It saves up to 30 percent energy compared with conventional valves. One option is predictive maintenance, where damage can be prevented before it occurs. This is also sustainable in terms of the environment, as components are only replaced when really necessary.

A major factor in saving energy: frequency inverters. Without a frequency inverter the pump's drive motor runs at full speed right from the start. The travel curve - i.e. acceleration, full speed and deceleration - is controlled by a valve by means of energy dissipation. The now hotter surplus oil is simply fed back to the tank, making oil coolers frequently necessary. Frequency inverters, on the other hand, control the motor from as low as zero speed and pump only as much oil as needed for the ideal travel curve. Energy savings of 30 to 40 percent are possible, and the extra cost of the frequency inverter quickly pays for itself, especially in frequently used elevators.

 Eco Line

When current flows backwards

But there's more. With Supercaps, for example. They can be charged and discharged like rechargeable batteries but much faster. In addition, they last for many more charging cycles. By the way, these small powerhouses are also used in Formula 1 cars to store electrical energy in the KERS system for additional speed.

Bucher Hydraulics has adapted this technology for elevators. With the appropriate software modifications, it can even be retrofitted to existing units. A positive side-effect of the Supercaps - they reliably put an end to the dreaded energy peaks that really drive up the electricity bill.

The process works in reverse: the oil displaced from the cylinder by the car drives the pump. The pump turns backwards and the electric motor becomes a generator and produces electrical energy. The energy is temporarily stored in the Supercaps via the frequency inverter, where it waits for the next upward journey. This reduces the power consumption from the grid by 20 to 30 percent, depending on the application and payload.

Alternatively, the electricity can be fed back into the grid - which, however, requires a precise agreement with the energy supplier.

 SuperCap

Auf einen Blick: Effizienz mit ECOdraulics

  • Up to 30 percent energy savings thanks to the iValve
  • 30 to 40 percent energy savings due to the frequency inverter
  • 20 to 30 percent energy savings due to Supercaps or feedback into the grid
  • Oil cooler can be eliminated
  • Energy-efficient and made-to-last, hence careful use of resources
  • Simple and ecological modernization

Followed up with: Tony Aschwanden, Head of Product & Application - Elevator, Bucher Hydraulics AG

Mr. Aschwanden, what role does the application scenario of an elevator actually play in energy efficiency?
For elevators that make many trips, i.e. are used frequently, the energy intake during travel is, of course, more significant than in elevators that are mainly in standby mode. However, the consumption in standby is by no means negligible, according to a relevant study. You therefore have to pay close attention to how an economical solution looks in each individual case. But no matter how it looks, we have the right solution.

Frequency inverters and Supercaps have been around for a long time. Can't just anyone put them in?
No, this requires a lot of experience. An example: Supercaps can be just physically retrofitted of course. However, this also requires appropriate software modifications, in order to effectively charge these ‘batteries’ when traveling down and to retrieve the energy in a controlled manner when traveling up. This is where the real know-how lies nowadays. The system can even be retrofitted in existing units and thus save 20 to 40 percent of the energy, depending on the application.

When is it worthwhile to use a frequency inverter?
The fact is that so far only about ten percent of existing hydraulic systems are equipped with frequency control. This is because the frequency inverter can more than double the cost of the power unit. The application has to be analyzed very closely. In this respect, decades of experience as the Number 1 supplier of elevator hydraulics certainly helps us. The effort is worthwhile, if the system runs frequently. With 30 to 40 percent savings, the extra cost of such a system quickly pays for itself, especially since energy is becoming ever more expensive. In addition, we no longer need to use energy for cooling the oil!

Additional information

Product page:

Elevator Hydraulics

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