ASHRAE Journal - June 2022 - 43

HONORABLE MENTION | 2022 ASHRAE TECHNOLOGY AWARD CASE STUDIES | UDIES
to validate the previous energy model. To operate the
new chiller plant at a high-effi ciency level, a new digital
controller with mobile app function was installed
for ongoing real-time monitoring, commissioning and
optimization.
Innovation
Various innovative technologies have been adopted for
the achievement of optimum energy effi ciency and the
lowest life-cycle cost.
Novel Analytical Methods. For retrofi tting the existing
chiller plant, it is necessary to fi rst evaluate energy performance
and then make effi ciency enhancement decisions.
QGO was completed in 1985. Therefore, only daily
plant logbooks have been available. It is almost impossible
to review hourly records in past years; meanwhile,
it is important to complete missing data and correct
human errors/equipment faults. Evaluating energy performance
is common and very important when retrofi tting
existing buildings in Hong Kong.
To better manage this challenging task, new methods
have been used for analysis and estimation of the energy
performance of the existing chiller plant with comprehensive
consideration of three aspects:
* Annual cooling load demand profi les were based on
logbook records reviewed with comprehensive expert
analysis and judgement.
* Chiller operating schedules and hourly cooling
demands show the spare capacity of the chiller plant.
A maximum of three out of total four chillers can accommodate
nearly the whole year operation. Such an
N + 1 chiller arrangement creates a potential ESO, which
provides an opportunity via retrocommissioning for
fi ne-tuning individual chillers back to their optimum
performance.
* Degradation of the aged chiller was estimated at a
an average COP of 4.4. The energy management team
recognized that it was necessary to replace the existing
chillers with high-effi ciency ones.
BIM Technology Application. BIM was specifi cally
used throughout the project life cycle to enhance project
effectiveness and effi ciency. The BIM application has
minimized clashes and the risks of project delay while
also streamlining project management effi ciency.
Advanced Chiller Plant Modeling. The building's
performance by retrocommissioning approaches and
economic benefi t of each phase were simulated with a
well-known software that complies with both ASHRAE
Standard 140 and ASHRAE Standard 90.1 as well as the
LEED® Rating system. This advanced chiller modeling
consisted of three steps.
1. Energy estimation. The existing chiller plant was
taken as the baseline to establish the energy model,
which mainly considered the annual cooling demand
and existing chiller performance.
2. Proposed chiller plant's energy simulations.
The annual energy consumption of the proposed
chiller plant adopting new innovations could be well
evaluated through the energy simulation software.
3. Verifi cation of simulated results by on-site
measured data (measurement and verifi cation).
One year after replacing the two chillers in Phase I,
the measured results were collected and compared
with the simulated results. The difference between
the recorded data and chiller performance data for
the simulated results was a 13% variance for chiller
performance modeling and a 11.5% variance for annual
chiller consumption.
Based on the well-validated results given above, it
is logically reasonable to adopt the energy simulation
model to predict the potential energy-savings after the
completion of Phase II.
Adoption of New Generation Ultralow Global
Warming Potential HFO Refrigerant. The climate
commitment for environmental protection and
greenhouse gas emissions has been fully considered
in the design. As a result of the Montreal Protocol on
substances that deplete the ozone layer and the Hong
Kong Government's Climate Action Plan 2030+, an
innovative HFO refrigerant, R-514A, was proposed for
the replacement of existing HFC 134a chillers. This is
because the HFO has ultralow global warming potentials
(GWP less than 2), a short atmospheric lifetime,
and is considered safe for the environment. The QGO
is one of the fi rst government buildings in Hong Kong
to adopt innovations and technologies designed for a
combined operation with this next-generation HFO
refrigerant.
Energy Effi ciency
Energy effi ciency is a primary benchmark for evaluating
the effectiveness of retrofi tting projects.
Energy Consumption Before and After Retrofit. The
electricity saving for two phases has been summarized
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ASHRAE Journal - June 2022

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