energy efficient elevatorsgreenspun.com : LUSENET : Elevator Problem Discussion : One Thread
I am looking for information on energy consumption by elevators and for any newer technology that consumes less electricity (kWh and kW) than traditional motor-generator sets and DC motor systems. Are there any books or websites that might have this information? Does anyone have before and after consumption data for modernization projects?
-- Betsy Jenkins (firstname.lastname@example.org), December 31, 2003
-- John Brannon (email@example.com), January 01, 2004.
Betsy, We collected this data on a few of our MG to VVVF (AC) conversions and found that there's no one true answer. Variables as building traffic, (unique to each building), load, and dispatching efficientcy factor into the calculation. Usually when a modernization is done, the dispatch system is also upgraded. This causes the elevator to pickup and deliver building traffic more efficiently, thereby also reducing power consumption. Our data showed kwh savings between 5% and 25% depending on the building varables. The bottom line is vvvf drives saves energy over MG sets, and they require much less maintenance, repair etc..
-- Mike Lardner (firstname.lastname@example.org), January 03, 2004.
See the following for details of KONE's EcoDisc motor:
-- JL (email@example.com), January 20, 2004.
The energy to operate an elevator is basic physics. Required Power = Lift force X speed. However, power is a rate of energy consumption. The Total energy consumed during each run is that rate X running time. Always true for for each run, in either direction, with any % payload. To calculate the required force one must know much more about how the lift system is constructed, with or without counterbalancing. System losses are another part of the story. There will always be friction in rope sheaves, pulleys, gearboxes, rollers, slides, moving air column, etc. etc. Hydraulic elevators have the hydro system of pumps, valves and piping losses to deal with. Roped traction elevators with counterweights are capable of higher efficiency (than hydraulics) but also have a significant amount of moving inertia. Accelerating the this inertia for each run means that energy is added to the moving equipment. The required energy to accelerate the load can be almost equal to that required to make the lift alone. What happens to that energy during an elevator slow-down is very important when calculating the overall energy consumption.
Most people understand that the old m-g set is not as efficient as we would like it to be, and that it wastes power by running when no one is using the elevator. However, many people forget that it is inherently regenerative. That is, during an elevator slow-down much the energy storred in the moving inertia is pumped back into the utility line. Ditto for lowering of a load under the influence of gravity.
For traction elevators modern day SCR DC or VVVF AC motors and drives are more efficient than the old m-g set. But don't be totally fooled by all the hype. DC motors and AC motors are about the same overall efficiency for the same hp. [PM motors are a little better, but not that much.] SCR drives + obligitory transformer & acoustic noise filter are about 90% efficient, and they ARE regenerative. Low cost AC drives + obligitory input reactors may be 93-94% efficient but are NON-REGENERATIVE. This means that the energy added to accelerate the load and that potentially reclaimed by lowering by gravity, is simply dissipated as heat rather than pumping it back into the power system. This can represent a significant loss of opportunity which increases the overall power consumption in the case of a busy high speed elevator. This can add up to big numbers of wasted energy depending on the number of runs per day, typical payloads and operating speed. AC drives with full regeneration capabilities do exist. They cost more and end up with about the same overall efficiency as that of an SCR drive system. However, they do have the capability of providing regeneration AND high power factor, AND reducing utility line harmonics (over an SCR dtype drive) if you are willing to pay for that.
So one of the big questions to answer about overall energy consumption when comparing system lift equipment is whether or not it will regenerate.
If you are looking for ways to justify the cost of modernizing elevator lifts, don't forget to look at the relative size of the elevator consumption Vs that of the whole building. You might be surprized how little of the overall building consumption is actually used by the elevators. If you actually do a study in this regard, please publish your findings.
-- Don Vollrath (firstname.lastname@example.org), January 27, 2004.
Here is an interesting paper on the VVVF part of the subject. "A comparative evaluation of line regenerative and nonregenerative vector controlled drives for AC gearless elevators" Kulkarni, A.B.; Nguyen, H.; Gaudet, E.W.; Industry Applications Conference, 2000. Conference Record of the 2000 IEEE ,Volume: 3 , 8-12 Oct. 2000 Pages:1431 - 1437 vol.3
-- Don Vollrath (email@example.com), January 29, 2004.
There is a new software that has been developed that can look at different types of drives and simulate the traffic in the building. If you are interested in more details, let me know.
-- Lutfi Al-Sharif (firstname.lastname@example.org), May 11, 2004.
I wonder what the relative use (sales) is for regenerative drives or traditional drives in elevators? It seems that the added cost may be hard to justify.
-- Jeff Shepard (email@example.com), June 17, 2004.