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EPG Application Note
In Situ: On - Site & On - Line
Electric Power Generation (EPG)
A major food retail chain wanted to
participate in cost savings derived from utilities sponsored “load
shedding / peak shaving” programs. The concept was further enhanced by
having a reliable power source, on each store site, for emergency outages!
After installation of a 1,000 kW
engine-generator (EnGen), noise complaints from an adjacent muffler
repair shop, car wash and nearby apartments resulted in a violation notice
from the Municipal Environmental Protection Agency (EPA). The citation
mandated a maximum of 65 dBA, during
daylight hours, at the property line which was approximately 18 feet from
) the EnGen!
Figure 1 – EnGen site depicting building
retaining wall/property line proximity.
Also, during climatically warm days,
when load shedding was required, the EnGen’s physical orientation to the
architectural building impeded cooling air flow and would not permit
maximum electrical loading. (Reference
Consultants, LLC (AEC) was contacted for development of a turn-key
remediation to abate the noise citation, improve aerodynamics and return
the EnGen to a profitable status. AEC engineers divided the project into
two (2) phases:
Figure 2 – EnGen weather housing before
aeroacoustic modifications with ambient
noise monitoring at property line.
Determine if the EPA mandated 65 dBA is reasonable and / or achievable
within the defacto urban acoustic ambiance (pre-existing background
noise). (Reference Figure
Design, fabricate and install requisite noise suppression hardware to
achieve regulatory compliance, meet EnGen manufacturers aerodynamic
requirements and all within financial budget constraints of the EPG site.
To accomplish Phase 1,
AEC engineers instrumented the property line nearest the EnGen with
acoustic and climatic data logging systems. Rural test sites (Ref.
Fig. 3) would have included a global positioning satellite (GPS)
system for accurate position location(s) verification and/or future
predictive computer simulations (reference, AEC specification sheet number
69900). Acoustic data and noise spectra are contiguously recorded for the
entire test duration (maximum of 100 days of 24-hour contiguous data) and
in the engineering units / acoustic descriptors required by governing EPA
standards (reference, AEC specification sheet number 29603). After 15
continuous test hours, with the EnGen locked off, data revealed the sites
defacto acoustic ambient (LAeq) was
without the EnGen running!
ACOUSTICS, AERODYNAMICS &
SITE TOPOGRAPHY ARE
COMPUTER SIMULATED & SYSTEM INTEGRATED
To accomplish Phase 2,
AEC engineers, armed with the data obtained in Phase 1, initiated
the design of a noise abatement system to meet the acoustical, physical
and financial constraints imposed by the EnGen site location. Three
dimensional (3-D), acoustic computer simulations automatically selected
the material types and configurations while a computational fluid dynamics
(CFD) computer routine monitored system aerodynamics. Both an acoustic and
aerodynamic summary is attached with each generic system assembly
candidate for the optimum EnGen site performance selection. When an
aeroacoustic remediation configuration has been selected and
topographically site adapted, the computer program will generate a shop
ready, complete bill of materials (digital production file) ready for
fabrication. This drastic reduction of engineering hours from concept to
construction makes custom designs, with optimized aeroacoustic
performances, much more convenient and cost effective than “off-the-shelf”
hardware that sacrifices system performance for a pseudo inventory of
system mis-matched packages.
Figure 3 – Typical rural test site
acoustics, GPS location and weather data.
Submission of Phase 1 test data to
the Municipality resulted in a variance that
saved the owner more than
$20,000.00 in additional acoustic
hardware to meet the original EPA criteria. Post installation aeroacoustic
testing verified EnGen site noise reduction satisfied all Municipal, State
and Federal EPA noise ordinances, per variance. Further, improved
aerodynamics eliminated troublesome EnGen shutdowns on high temperature
days and costly penalties from the utility. Reduced hardware costs for
remediation were within budget constraints and maintained the site
profitability and payback schedule. Overall, the owner received a
dependable power generating source that was community friendly and an
eager contributor to his financial bottom line. (Reference Figure 4)
Figure 4 – Noise abated configuration
depicting inlet and discharge silencer banks,
secondary exhaust mufflers and modified
weather housing for enhanced aerodynamics.
If you have an existing noise problem that
requires rehabilitation or are embarking on a proposed project with an
acoustic criteria, contact AEC for assistance starting with a telephone
consultation. From engineering services to noise abatement systems
through system installation, select any or all from the AEC “aeroacoustic
supermarket.” Just give us a call and let a qualified AEC engineer assist
you to establish an effective, guaranteed solution. Tell us about
your noisy problems then, let our over 30 years of experience with noise
make your job easier.
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