Public Relations

White paper | Saving Energy using PICVs | June 2017
© Siemens Switzerland Ltd, 2017 6
As PICVs Maintain Flow, Pumps Optimize Pressure
On the other hand, PICVs make it possible to deliver the
same flow at a lower pressure difference. As long as the
pressure difference remains in the allowed PICV operating
range, the flow will be maintained at the set level (auto-
balancing feature).
This opens the door for advanced pump control strategies,
where the same flow is delivered at a lower pressure
difference, somewhere between the lowest possible point
(to remain in the PICV’s operating range) and the nominal
point (Figure 8).
The pump battles against less resistance. It can operate at
an optimal speed and requires substantially less energy to
provide the same performance.
Savings from a Real Case
Application in Real Life Case Study
The three ways to generate savings described in this paper
were implemented in a campus with several buildings in a
large Saudi Arabian city that has a representative number of
heating and cooling days.
This building features air handling and fan coil units, with
chilled water for cooling and electrical re-heaters for
heating. The chilled water system incorporates the
following components:
o 10 chillers. Located at utility building. Nine duty
and one standby, capacity: 1370 kW each.
o 10 primary chilled water pumps, constant speed.
Located at utility building. Nine duty and one
standby, capacity: 55 l/s (198 m3/h) @ 30m head.
The ratio of installed pump capacity and installed
cooling capacity (chillers) is approximately 1.5%.
o 10 secondary chilled water pumps, variable speed.
Located at utility building. Nine duty and one
standby, capacity: 55 l/s (198 m3/h) @ 55m head.
The ratio of installed pump capacity and installed
cooling capacity (chillers) is approximately 2.5%.
o Different sizes of air handling units (AHUs) and fan
coil units (FCUs) located at each building as per
demand cooling loads. Control valves with
electrical actuators installed on the chilled water
return pipes of the cooling units (AHUs and FCUs).
Up to 30% Savings with PICVs
Using actual operating and climatic data, energy savings
were generated for both energy distribution and energy
generation using the following three methods:
o Eliminating heat exchanger overflow at any time
and under any operating condition
o Improving control accuracy by eliminating
hydraulic cross-coupling between neighboring
control loops
o Enabling advanced energy distribution strategies
by eliminating the risk of heat exchanger / cooling
coils starvation
In this case, conservative calculations demonstrated that
using PICVs in the building yielded savings of up to 25-30%
in energy distribution and savings of 2-5% for energy
generation.
In absolute annual figures, these savings amounted to
approximately 330 MWh and approximately 200 MWh,
respectively, or a total annual cost saving of around 34000
EUR.
Figure 8: Pump control strategy with variation of
differential pressure.