E NE RG Y MAT TER S
FACT SHEET 8:
REDUCING CONSUMPTION
There are many ways in which energy
consumption can be reduced, but basically
they fit into one of two categories:
• only using devices when actually
needed
• making sure that when the device is
being used that energy is not being
wasted
1. Managing The “On” Time
The most powerful technique of energy
conservation is turning off equipment
when it is not needed. If the device is
switched off when not needed, it doesn’t
consume energy. The switching can be:
• manual – they require a person to
switch them on or off
• individual timers – a mechanism
within the switch itself, which could be
a push button which releases itself
slowly or a dial which allows the user
to set a time that the device stays on
for
• scheduling systems – remote control
systems which are programmed to
switch equipment off and on at preset
times or conditions (eg temperature)
• occupancy or temperature sensing – a
sensor recognises when the equipment
(eg lighting, air conditioning) should
be on
Time clock controls are a primary tool for
this latter function, because most
equipment is needed on the basis of
specific time schedules. Achieving effective
and long-lasting clock control involves a
number of key design features:
• sufficient flexibility to adapt to all
the predictable variations in schedule,
such as weekends, public holidays,
leap years and daylight saving
•
•
very clear instructions for setting
and adjusting them
easily used overrides that allow users
to easily bypass the timeclock when
equipment is needed during
unscheduled periods
Lighting control systems also need to have
some warning system in place, so that
persons still in the facility when the lights
are due to be switched off know that this is
about tho happen, and can use the
override if necessary.
Occupancy recognition is the strategy
applied to intermittently occupied areas to
turn lights on when people are present and
automatically turn lights off after the room
is unoccupied. The two principal
technologies used for occupancy sensors
are passive infrared (PIR) and ultrasonic.
Standby power
Many modern appliances, such as TVs,
computers and ovens, use power all day
and night, even when not in use. This
standby power may be substantial and
required to maintain a convenient 'ready'
state for instant, on demand use. However,
in some cases, standby power serves no
useful function or operates at excessive
levels for the background task being
performed.
Standby becomes necessary to power
certain core functions or to sense
communication for those products that are
waiting to provide full services. This power
is consumed not while the appliance is
being fully utilised but while it awaits
instruction; while it is "standing by". Some
appliances also perform a continuous
function that requires small amounts of
continuous power.
Getting the message across
Much of the energy consumption within a
facility is in the control of people, not
electronics. Therefore, education of the
workforce is essential. This can mean
training sessions for the “big picture” but
on a day-to-day basis, means signage.
Some of the communication problems
that workforce education can solve are:
• lack of awareness of how much energy
equipment uses
• lack of awareness of what can be done
to conserve energy
• lack of awareness of how and/or when
to carry out energy conservation
actions
• controls are difficult to use
• unwillingness to act
• lack of motivation
Signs will address many of the problems,
and do so by in effect granting people
permission to do something. However, it
is critical that the signs are relevant to the
environment they are placed in and
specific in their information. Generic
“conserve energy” signs are not worth the
paper or plastic they are printed on.
LOCATION
• on all devices affecting energy
consumption that require human
action, eg windows, light switches, fan
controls
• in areas automatically controlled, eg
lights
Energy Matters 8. Reducing Consumption
•
where they are visible and “connected”
to the equipment or switch they are
related to, eg next to the switch
CONTENT
• purpose or identity of the item
• what to do (or avoid doing)
• when to do it
• how to do it
• what response to expect
• how to get help, if needed
Some of these can be omitted if obvious.
2. When the switch is “on”
When the device must be on, it is
important that it does not use more energy
than necessary to do the job that is
required. There are various reasons why
this is not the case:
• over-specification of equipment
• losses, eg poor insulation
• inefficient design of equipment
• operational problems
It is beyond the scope of these notes to
cover in detail all types of energyconsuming equipment. However, lighting
is common to all situations, and Chapter 4
covers in some detail aspects of making
lighting as efficient as possible.
Over-specification
This is where through careless, ignorance,
over-conservatism or enthusiastic
salesmanship, the equipment being used is
more than sufficient to do the job. This is
most common in lighting where the area is
flooded with light, providing more
illumination than is necessary for the tasks
being performed.
With other equipment, such as
refrigeration or heating, it means that the
equipment should be off more often than a
lower powered equivalent, but when it is
on, it is drawing more power, and the
overall energy consumption is greater.
However, if the over-specification is
not the equipment, but the “space” that the
equipment is servicing, such as a
refrigerated warehouse, this will use lots of
energy for no benefit.
The problem of course with such
over-specification is that the equipment
has already been purchased, and can only
Page 2 of 4
be downsized when it has to be replaced.
With lights, this is a relatively cheap
option, and in fact, in multi-lamp fittings,
such as fluorescent housings, one of the
tubes can be removed before it fails, and
be used as a replacement later on, thus
economising in two ways.
It should be said however that some
spare capacity in any system is essential to
deal with extreme situations and to reduce
wear on the equipment, which would
otherwise be on all the time.
Losses
Losses of energy in this context generally
refer to heated or cooled air, but can have
other meanings.
INSULATION
Insulation acts as a barrier to heat flow
and is essential to keep your home warm
in winter and cool in summer. A well
insulated and well designed home will
provide year-round comfort, cutting
cooling and heating bills by up to half.
Table 1 shows the losses and gains of heat
in a temperature climate such as
Newcastle’s.
TABLE 1 Heat losses/gains
Part of building
Ceiling/roof
Window
%loss/gain
25-35
10-20 (loss)
25-35 (gain)
Wall
15-25
Floor
10-20
Air leakage
15-25 (loss)
5-15 (gain)
There are two types of insulation – bulk
and reflective. Each works in a different
way, and has its own uses.
Bulk insulation mainly resists the
transfer of conducted and convected heat,
relying on pockets of trapped air within its
structure. Its thermal resistance is
essentially the same regardless of the
direction of heat flow through it. Bulk
insulation includes materials such as glass
fibre, wool, cellulose fibre, polyester and
polystyrene.
Energy Matters 8. Reducing Consumption
Reflective insulation mainly resists
radiant heat flow due to its high reflectivity
and low emissivity (ability to re-radiate
heat). It relies on the presence of an air
layer of at least 25 mm next to the shiny
surface. The thermal resistance of
reflective insulation varies with the
direction of heat flow through it. Reflective
insulation is usually shiny aluminium foil
laminated onto paper or plastic and is
available as sheets (sarking), concertinatype batts and multi-cell batts.
Commercial insulation materials are
sold with an R-rating, which is a measure
of their effectiveness in preventing heat
conduction: the higher the R-rating, the
less heat passes through. Fibreglass
insulation “batts” are typically at least 10
times better insulators than the common
wall and roof construction materials.
Different levels of insulation are
recommended for ceilings and walls. The
means by which the insulation is put in
place obviously differs from one type of
house to the next, and also if it is going
into a new building, or being retrofitted to
an existing one.
AIR LEAKAGE
This means the unintended passage of air
through the outer structure of the
building, i.e. doors, windows, ceiling and
walls. Leakage is caused by:
• pressure imbalances – air moves due
to a difference in pressure between
two points; air conditioning generally
causes high pressure zones, and the air
inside them attempts to find means of
escape
• “chimney” effect – cold air is denser
than warm air, and can create
convection currents through a
building, drawing cold air in and
pushing warm air to the top of the
building and out; if this is in summer,
it is not a problem, but it certainly is in
winter!
The moving air will find “breaks” in the
internal lining of the building, resulting in
losses of heated air (in winter) or cooled
air (in summer). Unintended breaks can
best be found by “smoke testing”, using
specially-designed “smoke pencils” which
generate small plumes of smoke which will
show up the air currents.
Page 3 of 4
Maintenance
All the schedulers, signs, efficient design
and loss minimisation in the world will not
overcome poorly running equipment due
to lack of maintenance. Unfortunately,
preventative maintenance tends to be the
first thing cut when short-term savings
need to be made. Then the inevitable
happens. Breakdowns occur that could
have been avoided by a regular
maintenance program. Examples of
maintenance failures that would cause
wasted energy consumption include:
• dirty light fittings
• flickering fluorescent tubes
• blocked air conditioning filters
• faulty thermostats – a very common
problem, which causes cycling (rapid
stop and start) or overshooting (not
stopping or starting when exceeding
the set values)
• motors with worn bearings or
requiring lubrication
• leaks in water heating or steam piping
• incorrect readings on control dials and
meters
• broken seals on oven or refrigerator
doors
• poorly fitting external doors
must display a standardised energy
rating label, as shown below.
Products regulated under the rating
system include:
• refrigerators and freezers
• mains pressure electric storage water
heaters
• air conditioners
• fluorescent lamps
Maintenance isn’t difficult or that
expensive, it just isn’t an obvious benefit
until things break down.
Inefficient design
For much of the time that electrical
equipment has been designed and built,
most thought went into making sure it did
the job it was supposed to as well as
possible. In a lot of cases, this meant
using lots of energy in the process. In the
last decade or so, conscious efforts have
been made to improve the energy
efficiency of a wide range of equipment,
and in dong so, create another selling
point to distinguish item A from
competitor’s item B.
As householders, we are all aware of
the star rating system for whitegoods, such
as washing machines, air conditioners,
refrigerators, dishwashers and clothes
driers. What you may not have known is
that it is now law that all whitegoods
Energy Matters 8. Reducing Consumption
Page 4 of 4