Example Of Energy Savings; Comparison Of Energy Savings; Example With Varying Flow Over 1 Year - Danfoss VLT DriveMotor FCM 106 Design Manual

Application Examples

4.2.3 Example of Energy Savings

As shown in Illustration 4.7, the flow is controlled by
changing the RPM. By reducing the speed only 20% from
the rated speed, the flow is also reduced by 20%. This is
because the flow is directly proportional to the RPM. The
consumption of electricity, however, is reduced by 50%.
If the system in question only needs to be able to supply a
flow that corresponds to 100% a few days in a year, while
the average is below 80% of the rated flow for the
remainder of the year, the amount of energy saved is even
more than 50%.
Illustration 4.7 describes the dependence of flow, pressure
and power consumption on RPM.
100%
80%
Flow ~n
50%
25%
12,5%
50%
Illustration 4.7 Laws of Proportionalilty
Q 1 n 1
Flow : =
Q 2 n 2
H 1 n 1 2
Pressure :
=
H 2 n 2
P 1 n 1
3
Power :
=
P 2 n 2
Q=Flow P=Power
Q =Rated flow P
1 1
Q =Reduced flow P
2 2
H=Pressure n=Speed regulation
H =Rated pressure n
1 1
H =Reduced pressure n
2 2
Table 4.4 Legend for Illustration 4.7

4.2.4 Comparison of Energy Savings

The Danfoss frequency converter solution offers major
savings compared with traditional energy saving solutions.
This is because the frequency converter is able to control
fan speed according to thermal load on the system and
the fact that the frequency converter has a built-in facility
that enables the frequency converter to function as a
Building Management System, BMS.
®
VLT DriveMotor FCP 106 and FCM 106 Design Guide
Pressure ~n 2
3
Power ~n
n
80% 100%
=Rated power
=Reduced power
=Rated speed
=Reduced speed
MG03M102 - 08/2015
Illustration 4.8 shows typical energy savings obtainable
with 3 well-known solutions when fan volume is reduced,
for example to 60%. Energy savings of more than 50% can
be achieved by applying a VLT solution in typical
applications.
100
1
80
2
60
40
20
0
0 60
0
Illustration 4.8 Comparative Energy Consumption for Energy
Saving Systems, Input Power (%) vs Volume (%)
1 Discharge damper solution - lower energy savings
2 IGV solution - high installation cost
3 VLT solution - maximum energy savings
Discharge dampers reduce power consumption somewhat.
Inlet Guide Vans offer a 40% reduction but are expensive
to install. The Danfoss frequency converter solution
reduces energy consumption with more than 50% and is
easy to install.
4.2.5 Example with Varying Flow over 1
Year
This example is calculated based on pump characteristics
obtained from a pump datasheet.
The result obtained shows energy savings in excess of 50%
at the given flow distribution over a year. The payback
period depends on the price per kWh and price of
frequency converter. In this example payback is achieved is
less than one year, when compared with valves and
constant speed. For calculation of energy savings in
specific applications, use VLT Energy box software
3
60 0 60
%
39
4 4