There was
only adequate budget to replace one of the chillers, so the new chillers’ capacity
was increased as high as possible while still using the main breaker and conduit/wire from
the old chiller that was being replaced. The chilled water and condenser water
pumps were converted to variable flow operation. The cooling tower capacity was
doubled compared to the previously installed original capacity, and the cooling towers
were converted to variable speed fan operation.
A new
Siemens DDC system was installed to implement our proprietary control sequences. As
a part of the control system, a minimum of 4 DDC zones (one per building exposure) were
added to each floor to give the engineer operational feedback, and assist in the automatic
reset of the supply air static pressure and temperature setpoints. Each new TI
remodel is slated to replace the existing pneumatic zone controllers with new DDC zone
controllers, and eventually, there will be no pneumatic zones left in the building.
These
modifications reduced the energy consumption for the entire building by slightly over 30%,
and the chiller plant system (chillers, pumps and cooling towers) has operated at an
average of 0.503 kW per ton for the March 2000 through December 2000 measurement
period. The total HVAC system (chillers, pumps, towers, floor by floor air
distribution systems) has been operating at 0.93 kW/ton over the same period. The HVAC
system energy consumption has been cut by over 50% compared to the previous equipment and
operational sequences of operation. A total of over 500,000 data points were used in
the evaluation of the equipment and system efficiencies.
The project
was originally calculated to have a five year simple payback period. Since the
electric utility rates in San Diego quintupled during much of the summer due to
deregulation, the simple payback period has been cut to less than 1.5 years.
The savings
we had projected over the course of a year are being obtained in 1.5 months during the
summer.
These
savings occurred over a very warm year, and with an increase in occupancy of 11%. (Graphs
for this building) |
