Lifts Low-carbon
Key actions
> The relationship between the rated capacity and
How to reduce the available car area is non-linear. For example, a lift Shutterstock
your lift’s CO
2
car with a platform area of 1.3 sq m is considered big
footprint enough for six people (0.21 sq m each), whereas a lift
car with a platform area of 5 sq m is considered big
Turn off lift car lights and
auxiliaries, and the power
enough for 33 people (0.15 sq m each, or six people
side of the lift controller, per sq m.)
after a lift has not been
However, observations show that passengers do not
used for five minutes
fill cars to such a high density. If passengers do not
Shut down lifts during
load lift cars to the densities given in Table 1.1 of EN81-
periods of low traffic
demand
1/2, then for many years the drive systems of lifts have
been oversized. For example, in the case of the 1,600
Reduce the
counterbalancing weight
kg traction lift (a popular size) this oversizing is equal
to match the realistic to 20 per cent, and for a 2500 kg traction lift, 33 per
number of passengers a
cent.
lift can accommodate
Because the drive motors are being oversized, their
Reduce the drive motor
iron and copper losses will be a larger proportion of the
size to match the realistic Running lifts at slower speeds could improve efficiency
number of passengers a
energy required, leading to lower machine efficiencies.
lift can accommodate
The capital costs and energy audit of the motor, its from zero to two-thirds rated load, the drive motor is
Re-evaluate the
associated drive controller, wiring, and so on, will also working within its capacity. If the car fills to the rated
counterbalancing ratio
be larger. A result of reducing the car loading values, load, then the drive motor must exceed its rating. This
from 50 to 33.3 per cent
from the rated load to the notional rated load values, will cause the motor and the drive to be overloaded.
Reduce drive motor
is that the weight of counterweight can be smaller and There is a solution, however, which is to run the drive
size to match the new
counterbalancing ratio
would result in immediate energy savings. motor at a lower speed for car loads greater than two-
thirds full.
Provide a drive controller
capable of variable-
Speed drives The consequence of running at a slower speed is that
speed, variable-voltage, The drive motor of a traction lift is required to move
the lift will take longer to move between floors and this
variable-frequency
the load of the passengers in the car. In order to reduce would have some effect on handling capacity in peak
control of the drive motor
the size of the drive motor, the weight of the car, plus a demand periods. However, the effect would lessen as
proportion of the maximum weight of the passengers passengers leave the car, often at the first floors, thus
(the rated load), is balanced by a counterweight. The reducing the loading. The consequences of a lower
commonly used value for the counterbalancing ratio counterbalancing ratio are:
is 50 per cent. For a lift with this counterbalancing, • A smaller motor and controlling drive unit are
when it is half full with passengers, the motor only required, leading to a lower energy usage;
needs to overcome various losses in order to move the • The drive control system would need to detect the
lift. However, is the value of 50 per cent correct? It car load and set the target speed to meet the rating
has been observed that some lift designers use values requirements; and
as low as 40 per cent, leading to the conclusion that • Traffic calculations would need to take into account
it has already been recognised by some designers the variable speed and increased flight times that
that lifts do not fill to the rated capacity. Suppose the occur.
counterbalancing ratio were set at 33.3 per cent. What
effect would this have? In the range of passenger load European standards
The suggestions above are win/win outcomes for
owner, consultant, supplier and installer, as the payback
Shutterstock
periods can be quite short.
Work is going on at the international level in ISO
TC178/WG10 to measure the energy consumption of
lifts (ISO/DIS25745-1: 2008) and to provide an energy
classification system similar to that used for white goods
such as fridges, from Class A (good) to Class G (bad).
Although the energy saved for lifts is small compared
with that used by other building services, it does result
in lower operational costs for lift installations – and at
no increase in the carbon footprint. l
Dr Eur Ing Gina Barney is a member of the CIBSE Lifts Group
committee and the CIBSE Guide D: 2010 revision panel.
www.liftconsulting.org www.cibseliftsgroup.org
CIBSE Guides D and F are available from the CIBSE
bookshop at www.cibse.org
Do lifts need to be in operation during periods of low demand?
38 CIBSE Journal July 2009 www.cibsejournal.com
CIBSEjul09 pp36-38 lifts.indd 38 26/6/09 12:13:08
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60