The energy consumption of under-utilized lifts in standby mode

Ferhat Celik, graduated from Istanbul Technical University, «mechanical engineer.» Then he received a master’s degree and Ph.D. from the Institute of Scientific and Technical University of Manchester (UMIST). For seven years he served as assistant professor at Istanbul University and then joined the company Blain Hydraulics, making valves, hydraulic elevators, where he headed the department of R & D in electronic servo valves. Ferhat Celik — author of technical papers on hydraulic lifts, industrial processes, systems CAD and automated production.

Concerns about global warming and environmental pollution causes implement methods of optimal use of energy and in the elevators. The elevator falls from 3 to 10% of the energy consumed by the building. To date, various methods for reducing energy consumption of elevator, and some of them are already being used in practice. Frequently used elevators typically consume more energy in the process than in standby mode. However, much of the elevators, especially in residential buildings, is most of the time in standby mode, and because their energy consumption is determined by the time spent on standby. Moreover, the evaluation of real energy consumption should take into account the energy equivalent of the cost of maintenance and spare parts. Therefore, considering the question of the energy used by an elevator, some attention should be paid to the power consumption in standby mode and during maintenance.

In addition, an increasingly important criterion when choosing the elevator becomes a short payback period of energy-saving elevators.

This article focuses on maintenance costs and energy consumption in the standby hydraulic elevators and elevators with traction and studied in detail the energy consumption lifts.

1. Introduction

Researchers used various methods to determine the energy consumption lifts. These methods include theoretical approaches, solutions based on the formulas and tables, the results of direct measurements, a combination of these methods, finally, modeling, simulation and others1. Al-Sharif and his colleagues reported that they had received acceptable values ​​of energy consumption lifts, through the use of flexible software and simulation models developed by them modelirovaniya2. However, the correct results from these models are available only if you fill them with realistic data. Of great importance in this case have the data such as the number and intensity of visits, the balance of the cabin and the cargo load counter, height and others. On the basis of the reliability of these data to choose the drive system that greatly impact on the consumption of energy lift.

2. Energy consumption in standby mode

Since the beginning of the 1980s in elevators began to use the achievements of microelectronics. At that time, refused to relay control systems elevator. Through the use of electronic controllers drive them fix those associated with the use of control systems based on relays problems such as frequent failure, short life, large and small design flexibility. Against these advantages the additional energy consumption electronic control systems have neglected. When they began to use the system locks the door, and then the variable speed drives, backlit buttons, displays in the cockpit and outside the mine, warning, safety, and other similar systems lift, increased demand for energy consumed in standby mode in order to maintain all of the equipment in the active state.

At the same time two-speed elevator drives are widely used in prior periods have given way to compact motors with variable speed drives (VSD) (electric drive). These drives have become popular because they are used in elevators without machine room, where asynchronous motors and permanent magnet work mainly with variable speed drives and variable voltage (VVVF). The drives are often called VVVF inverters. The use of these systems in elevators without machine room led to the abandonment of gear, reducing the size of the engine, improving the quality of the trip. In addition, manufacturers claim that the use of these systems reduces the power consumption to 50% compared to conventional traction sheave elevator. In addition to the systems without machine room, inverters have become the preferred option for the traditional traction elevators, which provide the engine room and the gear system (motor and gear unit + inverter). It also serves as the energy-saving alternative to a two-speed elevators.

When going to the traction sheave elevator, which are equipped with inverters, solves the problem of energy saving, hydraulic elevators with inverters and / or the battery again took their place in the market as systems that provide energy savings. Although inverters are added to the overall energy consumption of the energy balance of the system, drives the inverter shows energy-saving solution for all installations. Along with increasing competition in the market of elevators for low-rise buildings, the use of an elevator drive with inverters has become a trend. Then the user to ensure that these systems are only energy-saving solution, regardless of the degree of use of the elevator during the year. Then, a new marketing strategy is transformed into a rant about environmentally friendly, aims to increase sales to the elevator drive inverters.

In one study, the Swiss Agency for Energy Conservation (SAFE) 4, held on 33 elevators, it was reported that the proportion of energy consumed by an elevator in standby mode, up to 80% of total energy consumption. Fig. 1 is a graph showing the development of energy consumption in standby mode lift for decades. In a study of management SAFE also noted that the hydraulic system is as energy-efficient inverters, as well as a system with traction machine room.

The same conclusion comes Liz in his master’s thesis. These results contradict the general notion that hydraulic elevators consume more energy than a traction sheave elevator without machine room. In addition, the study says Lisa that underutilized elevators installation of inverters leads to an increase in energy consumption in standby mode, and therefore, the traditional hydraulic elevators are still serious option worth considering. Liz said that, if the elevator is idle about 80% of the time, the inverter will consume about 222 kWh / year for each elevator. This means that for many underutilized elevators will experience an increase in energy consumption despite the use of the latest energy-saving technology.

Author of many articles also indicate that any energy-saving elevator system under these conditions does not make as a result of cost reduction.

Another example of this — a hydraulic lift with batteries. Despite the fact that such systems are not often used in the market because of their cost, it is proved that they consume more power when they are constantly used at low load.

The figure shows the devices adversely affecting the power consumption in standby mode. As can be seen from the figure, the devices, which account for the maximum power consumption are permanent lighting cockpit and door lock system. This is followed by an electronic controller and an inverter. Among others — call buttons on the floors, on the floors of displays, button in the cockpit, the light curtain in the cabin, etc.

The figure shows the energy consumption during operation and standby time on the number of cycles of operation of the elevator. Also shown is the energy consumption as a percentage depending on the building type.

From the above data shows that the annual number of cycle trips in a typical six-story building is about 40 000 (110 cycles per day), and despite the use of energy-efficient systems, 83% of energy consumption falls on standby. Calculations show that the elevators in the building are medium in size from 200 000 cycles per year (550 cycles per day) at the same drive system to the standby mode accounts for 40% of energy consumption, and in hospitals and large office blocks from 700 000 cycles per year ( 1 900 cycles per day), the figure is 25%.

3. Factors adversely affecting the power consumption in standby mode

To reduce the consumption of energy in passive mode (standby mode) and active (working) mode developed appropriate energy-saving control system liftom7. In such systems, when the lift is not used for specific periods of time, power consumption is gradually reduced (passive control). The first stage is muted cockpit lighting and directional indicators are turned off movement at the landing and in the cockpit displays and buttons with dual illuminated in the cockpit. In the second step off the door controller, the electronic devices in the cockpit, and fans inverter buttons backlit double floor. Activation of this mode takes about 30 seconds, whereas the active control speed is reduced, cabin slowly fed directly to the floor, and it saves time ranking. Furthermore, part of the kinetic energy returned by the regenerative drive, preferably. It is found that the energy-saving control system of the elevator can save up to 50% of energy, and in some cases up to 90% savings.

Research of the German Association of Engineers DVI showed the presence of various areas of potential energy savings in the elevator system, published a list of measures needed to reduce energy consumption in liftah8. In light of this, it becomes clear that it is possible to save a considerable amount of energy due to the development of effective control systems. However, the methodology to determine the association DVI energy categories of elevators caused numerous criticisms of how inconsistent the European Congress for lifting devices in 2008, which was held in Germany.

In addition to developing the appropriate software and hardware systems for the elevator control in order to reduce power consumption in standby mode, you need to pay serious attention to the choice of the drive. Just to compare energy consumption of different drives need to make an assessment of the maintenance of the basic systems (lighting, fans, security equipment, lock the doors and drive, etc.) available to any drive separately. This way you can identify three important factors that affect the energy consumption in standby mode.

1 factor. Energy consumption in the standby mode of the elevator controller: As shown in Table 2, the electronic controller elevator issued by different companies, consume different amounts of power. This is mainly due to the amount of energy consumed by the inverter in standby mode.

2 factor. Energy consumption in standby mode inverter: Table 3 presents data on the energy consumption of some inverters, issued by various companies, in the standby mode. From the table it follows that the energy consumption in standby mode depends on the manufacturer of the product. It does not include the energy consumed by the fan, which adds 6 to 14 watts. This study revealed that most manufacturers do not understand the importance of the inverter energy consumption in standby mode

Products of many well-known companies give high in the table. Among the manufacturers of elevators widespread use of larger inverters to meet the structural requirements. However, a wrong choice of the motor-inverter leads to higher power consumption in standby mode.

UPS are widely used, especially with the introduction of elevators without machine room. Since the technical intervention for systems without machine room is complicated in the case of a malfunction or power failure requires an experienced, UPS floor. UPS includes an inverter consumes energy in standby mode. Therefore, comparing the drive system, it is helpful to carefully consider the energy needs of the UPS.

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