Elevator technology is essentially the same as it was when Elisha Otis created his safety brake for elevators back in the 1860s. And while major improvements may have been made in the motors used in elevators, the principles remain the same.
There are a number of different areas in which elevators can be made more efficient using the technology readily available today:
Regenerative braking technology is slowly becoming accepted in many different areas in industry. It is ubiquitous in electric cars, as well as hybrids. Using normal braking technology, the kinetic energy of a moving vehicle is converted to heat by the application of brake pads to a wheel. All of the kinetic energy is lost.
Regenerative brakes recoup some of the kinetic energy by using it to turn a small generator, also known as a dynamo. The electricity produced by the brakes is stored in a battery and is available for the vehicle’s use. With time regenerative braking technology is creating brakes that recoup more of the energy lost by the stopping of the vehicle.
Elevators are prime examples of vehicles where regenerative braking technology can produce excellent results. This is because the elevator’s counterweights ensure that no more than 55% of the elevator’s capacity must be moved or stopped by an input of energy. As a result, momentum can be built up at a relatively low energy cost. By recouping some of this energy in batteries, elevator efficiency is greatly increased.
Retrofitting elevators with regenerative braking technology is relatively simple, because almost all elevators use motors driven by DC power providing smoother acceleration. The input of DC power from a battery becomes almost trivial. Only the braking mechanism requires replacement.
The use of a continuously variable transmission (CVT) allows a motor’s transmission to use a gear ratio that provides maximum efficiency. A CVT enables moving between gear ratios steplessly, providing for smooth acceleration.
CVTs are used in a variety of applications from tractors and snowmobiles to drill presses and milling machines. Many cars, including racing cars, use CVT, as do systems for generating electrical power in aircraft.
The use of CVT in elevators can improve efficiency by using the gear ratio most appropriate to the weight differential between the current weight of the elevator and the weight of the counterweight.
Elevator control systems are probably the only part of the elevator that has seen major improvements over the last century. It was not that long ago that every elevator had an operator who controlled the elevator, starting and stopping the elevator manually, based on the requests of those riding the elevator and signals from those waiting for the elevator.
This system was replaced by a set of buttons inside the elevator, with a single button for each floor, and two buttons used for calling the elevator – an up button and a down button. This method enables the elevator to determine whether or not the direction in which the elevator is travelling is relevant to the person waiting to board.
With the advent of very tall buildings, elevators were assigned specific ranges of floors on which to operate. This allows an express elevator to ‘jump’ 50 floors or more before making frequent stops. This too improved efficiency.
However, drawbacks remain. If, for example, a person on the 23rd floor of a building is waiting for an elevator to take him to the 40th floor, he has no way of making this known to the elevator other that by pushing the up button. The next ascending elevator will stop regardless of the number of stops it must make between the 23rd and 40th floors.
An efficient control system will enable the person waiting for an elevator to signal his destination before the elevator arrives at his floor. A computerized system determines the most efficient car for him to board. In our example, the first car to pass the 23rd floor may be stopping 6 times between the 23rd and 40th floors. However, a car that will arrive only a few seconds later has a passenger who wants to alight from the elevator on the 23rd floor anyway, and will only make 2 stops before it reaches the 40th floor. By causing the potential rider to wait a few seconds before boarding an elevator, not only can a significant amount of energy be saved, but the rider will actually reach his destination faster than he would have if he had boarded the first elevator ascending past the 23rd floor.
Replacement of the control system should not be a major construction project, and may actually result in the best improvement of elevator efficiency.
Current technology can make elevators considerably more efficient than they currently are, resulting in significant savings for owners and operators of tall buildings.