A report for the Australian Building Codes Board (ABCB) in 2004, Energy Efficiency of Building Transport Equipment, divides traction lifts into two categories — gearless or geared. It says gearless lifts can reach in excess of 2.5 mps and smaller types are now being used with machine room-less lifts. Geared lifts range from smaller lifts and some machine room-less type lifts up to machines used to drive lifts with speeds up to 2.5 mps.
“Gearless units will always be more efficient than their geared cousins because there is no associated friction loss to overcome by transferring energy through the gear reduction unit,” says Sean Cadogan, business development manager at Kone Australia.
The ABCB report says energy efficiency in lifts decreases via frictional losses when the lift is moving. The report says to combat this problem, the architect or building designer could consider specifying more energy efficient types of equipment; using lightweight materials in the car superstructures; and roller guide shoes could be specified for both the car and counterweight, in lieu of sliding guide shoes.
Schlinder says 65 per cent of power in lifts is taken up in the utilisation phase — the start-up and stop phases. Ryan Singh, senior vertical transportation engineer at Lincolne Scott, says this can be reduced by adjusting the counterweight balancing of the lift. This can be done by estimating the number of people the lift will carry and anticipating what the lift’s handling capacity will be. The lift is then balanced accordingly.
Existing lifts can also be refurbished to be more energy efficient. Craig Russell, product line team manager at Schindler Lifts Australia, says older lifts use electronic static drives — a 4.15 volt motor connected to a generator to create the DC. “Newer lifts are generally all AC making the machine more efficient and cleaner as far as energy is concerned,” he says.
Singh says lifts up to 30 years old can be upgraded with a new control system, a new variable frequency drive system and installing a more energy efficient lighting and fan system. For example, he says in a typical car, if there are four standard downlights which are 20 watts each, that equals an average of 80 watts per hour. Whereas if those lights were replaced with four LED downlights, which are 5 watts each, the lift lighting would only be consuming 20 watts an hour.
Kone manufactures the ReSolve with Unity Drive, which can be fitted to existing high speed elevators during modernisation without the need to change existing machines, and uses up to 40 per cent less energy than traditional systems.
Zoning
Reducing the number of stops a lift makes can reduce its energy use. “If you look at a standard lift, it can typically serve all floors, whereas a more energy efficient lift will allocate people to certain cars so each lift will end up serving less floors,” Singh says. This process is known as a destination selection control system. In conventional lift systems, people enter their destination inside the lift. But with a destination selection control system, people enter their destination before they enter the lift and the control system will determine which lift they enter. So instead of people who are going to the same level entering different lifts, they will all be allocated to the same lift.
The Schindler Miconic 10 and Schindler ID Destination control systems can reduce the energy consumption by minimising the number of time the lift has to start and stop. The system uses complex algorithms to efficiently manage the passengers within a building. “This also benefits users as they ultimately arrive at their destination sooner. This is just one way that technology is allowing building owners to realise their energy reduction targets as well as managing their tenants expectations of quality and efficiency,” says Russell.
At two Central Tower buildings in Adelaide, Lincolne Scott was involved with installing lifts with the destination selection control system. The lifts also have regenerative feedback of power. This means as a lift comes down, it can generate energy which is fed back into the building’s power grid. “When a lift’s speed goes above 2.5 metres per second, generally you can achieve that [and] provide enough power back into the system to make a difference,” Singh says.
Schindler manufactures the Power Factor 1 drive, which becomes a generator of clean power as the lift decelerates, using the lift's momentum and gravity to create energy. The power created can then be distributed back into the power grid.
“The ReSolve with Unity Drive regenerates excess energy not used by the elevator system back into the base building electrical grid,” Cadogan says. “Older systems burn or dump excess energy as heat across resistor banks or into the motor. The energy savings over conventional motor-generator systems is up to 40 per cent less.”
Cadogan says standby energy is mostly consumed by the car lights, control devices, car ventilators, elevator drives and control systems. “This standby energy consumption can account for 25 per cent to 80 per cent of the total energy consumed by the elevator, depending on its design and usage.”
There are various ways to save standby energy. After the last car call, the car lights and the car fan can be switched off automatically and come on again the next time the car is called. Or in a building which has several lifts in use, one or more of the lifts could be left in standby mode in quiet periods and ventilation and lighting could be turned off.
In some Schindler lifts, such as the 7000 for high-rise buildings, light controls are a standard feature and lights are automatically turned off after 20 minutes as a default. Over 85 per cent of the total weight of the Schindler 7000 is also recyclable material, made out of different alloys of steel, cast iron and copper.
While it is important to look at the individual working factors in a lift, the ABCB report says the overall lift system also needs to be efficient. “That is, the building has the right number of lifts serving the most efficient floor zoning arrangement. [And] the lifts not being over sized and the speed relevant to the travel of the lift. With a lift system that is oversized with more lifts than are actually required, the lifts would tend to travel with a smaller load. This could mean more lift trips for the required handling capacity,“ the report says.
Singh says around 60 per cent to 70 per cent of lifts could currently be classified as energy efficient. He says, “People are making more of a concerted effort to improve the energy efficiency. However, there are a certain portion who look at the aesthetic appeal and some don’t like LED downlights or fluorescent lighting. But I think the majority is now leaning towards energy efficiency.”
Lifts are not currently energy rated. But Lincolne Scott is pushing for a rating, with Singh working with the Green Building Council of Australia to eventually attain a Green Star benchmark for lifts. The next step would be gaining a national star rating, similar to star ratings for household appliances. At the moment, Singh says any benchmark or rating is around two to five years off. How quickly a rating is developed depends on how quickly the idea is embraced by others in the industry.
