Fans by Fantech Electronic Catalogue

ENERGY SUSTAINABLE DESIGN

REFERENCE INFORMATION

2016

O-12

GREENHOUSE GAS AND BUILDINGS

To sustain a comfortable environment within buildings we have

to use energy in order to provide heating, cooling and

ventilation. Reducing a building's energy usage will ultimately

reduce greenhouse gas and carbon emissions, as well as save

cost for the building occupant.

Electricity as generated in NSW, Australia, produces

approximately 0.99kg of greenhouse gas (CO

) for every kWh

(1.3kg in Victoria); each kg contains approximately 272 grams of

carbon. If we assume a fan runs for 10 hours/day, 200 days per

year, then the table shown below can be used to calculate the

greenhouse gas and carbon output attributable to any

installation.

MINIMISING THE ENERGY USED BY FANS

Fans are a significant energy consumer but the energy that goes

into running them can be minimised with careful and appropriate

fan selection, ducting design and installation.

To achieve the best power saving solution:

Select the most suitable fan for the specified duty.

But remember, this may not always be the lowest cost fan.

Refer to "Fan Selection - First Cost versus Life Cycle Cost"

on this page.

Ensure the fan is given a chance to operate to its fullest

potential. Space restraints can result in negative system

effects.

Even without space restrictions, a lack of attention to detail

can result in negative effects. For example, a slack or

misaligned flexible connection on the fan inlet can cause

serious loss of capacity and efficiency.

Systems should be designed to minimise the pressure drop

by paying particular attention to bad practices such as:

- Slack or excessive length of flexible ducting.

- Locating high pressure drop fittings close to bends or

other disturbances in airflow.

Refer to

Section P

of this catalogue which provides a

comprehensive array of tips and advice on appropriate fan

installation practices.

An energy efficient fan and system combination is not

necessarily expensive. Indeed, when running costs are

considered, which they should, it generally works out to be more

economical after a short running time.

FAN SELECTION -

FIRST COSTS VERSUS LIFE CYCLE COST

A cheap fan often means that while you think you have a

bargain, it may end up costing you more in the long run.

For example, we have chosen a duty of 12,000L/s @ 300Pa.

Using the Fans by Fantech Product Selection Program, the

lowest cost in-line duct mounted fan selection is a model

AP1004GP6/29: a 1000 diameter fan absorbing 9.91kW with an

11kW motor running at 24r/s.

An alternative selection is a model AP1254GP6/16: a 1250

diameter fan, absorbing 7.54kW with a 7.5kW motor (in air-

stream rating) at 24r/s. This difference in list price between the

two fans is approximately $400, with the second one being the

more expensive and 250mm larger in diameter.

If the fan is to run for 10 hours a day, 200 days/year, then the

running power used for the first selection is 22mWh and

16.7mWh for the second (using fan absorbed power (AkW) and

motor efficiency @ 90%). At approximate Sydney, Australia

electricity prices, this equates to an annual running cost of

$3380 and $2500 respectively, with greenhouse gas being 21.8

tonnes and 16.6 tonnes and carbon usage being 5.9 tonnes and

4.5 tonnes.

In the period of one year, the second fan, while more expensive

on first cost, will have already saved the difference in running

cost against the cheaper fan. Fans have a normal life of 10-20

years, which means that the more expensive fan will save the

building occupant a considerable amount over its working life.

In addition, the saving in greenhouse gas and carbon will be

substantial. With responsible selection of fans, energy use can

be optimised.

FAN EFFICIENCY VERSUS FAN POWER

Fan efficiency is the energy needed to drive a fan as a

comparison of the energy imparted to the air. It is usually

expressed as a percentage and is traditionally based on the

motor output energy. Fan efficiency is important but only has

meaning when comparing fans of the same size. Here the fans

showing higher efficiency levels consume less energy.

When comparing fans of different sizes, selecting on the basis

of the efficiency percentage is unlikely to give the most energy

efficient fan. The figure to focus on when fans of different sizes

are involved is the AkW (Fan absorbed power).

Given a duty of 40,000 L/s @ 500Pa, and using the Fans by

Fantech Product Selection Program, the selection

AP1404CA9/30, a 1400 diameter in-line fan with a total efficiency

of 82% appears to be the most efficient selection, consuming

46.3kW. However, the AP1806DA9/21, and 1800 diameter fan

with a lower total efficiency of 77% consumes only 35.2kW –

almost 25% less!

The difference comes about because of the impact the velocity

pressure has on the total pressure: with the same air flow

passing through each fan the velocity pressure through the 1400

dia unit will be much greater than that through the 1800 dia fan.

kWh/pa

Greenhouse gas,

tonnes

Carbon,

tonnes

1.0

2000

1.98

0.54

2.0

4000

3.96

1.18

3.0

6000

5.94

1.62

4.0

9000

7.92

2.15