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Lifts Low-carbon
Elevating
effi ciency
Lifts are becoming increasing users of energy but are not
included in the Part L Building Regulations. However,
some key measures can be adopted to increase operational
efficiency, explains Gina Barney
C
IBSE Guide F suggests that lifts use often the result of powering an isolation transformer or
between five and 15 per cent of a building’s of energising DC motor windings in standby mode.
energy consumption, depending on the As lifts can be idle for more than 5,500 hours a year,
property’s profile and the lift technology consideration could be given to switching off at least
used. Part L of the Building Regulations calls for lower the isolation transformer and any pre-energising motor
CO2 emissions by requiring better building properties, winding power, leaving only the control electronics on,
but lift systems are not currently considered when in standby mode.
calculating the energy use of new buildings.
If commercial property owners take notice of the Off-peak downtime
need for energy efficiency – or are made to take notice Lifts are in peak demand in the morning, around
by the requirement for energy certificates – then midday and in the evening. In between these periods
total energy consumption of a building will fall, and there is much smaller inter-floor demand, which never
the energy consumed by lifts will then become more fully utilises its underlying capability. Do all lifts need
noticeable. Moreover, while modern lift systems using to be in service during periods of low demand? This is a
variable-voltage, variable-frequency regenerative drives As passengers are prepared to wait quite long periods
win/win
are highly efficient, at least half of the UK stock of for a lift during peak times, it would be reasonable for
around 300,000 lifts are more than 25 years old and them to wait similar periods when it is not so busy.
for owner,
less efficient. Owners can adopt a number of measures This would draw on the human psychology that a consultant,
to increase the energy efficiency of lifts. consistent response to a stimulus is preferable to a
supplier and
variable one. An opportunity therefore exists to take
Idle mode out of service – or even shut down – some of the lifts
installer, as the
All lifts require car lighting. Some have ventilation fans in a group during interfloor activity and still provide a payback time
and other devices such as information panels, CCTV suitable performance.
can be quite
cameras and even HVAC systems. Energy reduction Reducing the number of lifts in service during
could be achieved by turning off the car lighting and periods of low activity makes energy savings possible
short.
any auxiliary equipment, when the lift is idle and with respect to: car lighting/ventilation; controller
unoccupied. power consumption; the number of motor starts; and
The motion of a lift, the door movements and the motor power consumption, especially when car loads
service of passenger landing and car calls are supervised are close to the counterbalancing ratio.
by a lift controller. When a lift is idle, these controllers
consume energy in their standby mode. Measurements Occupancy densities
made on eight different lift installations indicated a Table 1.1 of BS EN81-1/2: 1998, gives for lift car platform
range from 25W to 2kW; the energy consumption was areas (from 0.9 sq m to 5 sq m), the rated loads (from
dependant upon the controller technology and age of 100kg to 2,500kg) and the rated capacity, assuming an
the equipment. At the high end, the consumption was average passenger weighs 75kg. >
www.cibsejournal.com July 2009 CIBSE Journal 37
CIBSEjul09 pp36-38 lifts.indd 37 25/6/09 15:21:30
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