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Dramatic
energy cost savings were reported by Kerrier
District Council, Camborne, Cornwall following
the installation of automatic lighting control
throughout its four storey headquarters building.
Assistant
Energy Manager John Butler had expected the
lighting control system from Ex-Or Ltd to
have paid for itself within three years. In
fact the payback period on control equipment
was just 14 months and annual savings in the
order of £5,700 will continue to be
made in subsequent years.
“These
are dramatic figures indeed,” said Mr
Butler. “We were confident that the
lighting control scheme would give us significant
cost savings but we didn’t expect the
savings to be of this high order.”
Kerrier
Council’s headquarters building comprises
2,820 sq m of floor space. There are more
than 1,000 light fittings in the open plan
offices and around 320 staff work there.
Gas
accounts for most of the total energy consumed
as it is used for the heating system. However,
because the unit cost of electricity is greater,
electricity accounts for three quarters of
the total energy bill.
Said Mr Butler: “Lighting accounts for
most of the electricity cost, and just walking
past the building at night showed the wastage
caused by lights left on needlessly outside
office hours. It was clear there would be
a great potential for saving money if we could
find the most effective way of controlling
the lights so they would automatically switch
off when not needed.”
Various
types of lighting control based on presence
detection were tested but they all presented
problems. Some were not sensitive enough and
occupants found themselves plunged into darkness
whilst working. Others allowed the lights
to remain on even though levels of natural
light were sufficiently high. Because of the
situation of the council building, and the
large area of external glazing, there is often
adequate natural brightness. In those circumstances
a control system was needed that would hold
the lights off when levels of natural light
were sufficient.
“We
put the Ex-Or LightSpot controls to the test
and found them to be easy to install, totally
reliable in use and well accepted by the staff.
So we then installed them throughout the building
and now around 90 per cent of all lights are
controlled in this way,” said Mr Butler.
Electricity usage before and after installation
has been closely monitored by Mr Butler. In
the 12 monthly period before the installation,
the electricity bill was £27,493. In
the 12 month period after the lighting controls
were installed the electricity bill was £21,762,
a reduction of £5,731 (a 21% saving
in overall electricity costs for the building).
In
fact, the savings in lighting costs are even
more dramatic than these figures indicate,
for during the period following the installation
of lighting control, the amount of IT and
computer equipment installed accelerated,
but the increased electricity use from that
cannot be measured as there is no facility
for load splitting in Kerrier Council’s
monitoring procedures.
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