# Small Compressed Air System Case Study

# Monte Villa Farms, Bothell, Washington

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height="2.8027777777777776in"}

# Project Summary

-   In 2005, Monte Villa Farms approached their electric provider
    Snohomish County PUD (SnoPUD) to reduce their energy costs. SnoPUD
    completed a field survey of the compressed air system at the site
    and found that the system had excess capacity, was oversized for the
    actual air demand of tenants, and correspondingly was operating at
    poor part-load performance. The compressed air system efficiency
    project had an estimated energy savings of 492,049 kWh per year and
    after SnoPUD incentives, the project yielded a net simple payback of
    6 months.

# Compressed Air System Overview

-   Premier Advisors LLC owns and leases a four building
    manufacturing/office/warehouse complex known as Monte Villa Farms in
    Bothell, Washington. As part of the lease, they provide clean and
    dry compressed air to their tenants.

-   The compressed air system supplied 120 psig air to the distribution
    piping network with two 125 horse power (HP) air cooled, fixed-speed
    modulating rotary screw air compressors automatically controlled to
    alternate service every other day. The building owner and tenants
    held a contractual agreement that the compressed air system would be
    available to meet peak air requirements 7 days a week. To serve the
    air requirement of the packaging machine at the far end of the
    plant, the system supply pressure had been increased to ensure that
    the required air volume could be supplied reliably at all times to
    packaging equipment.

-   Two air compressors, operating lead, lag, each a 125 HP QNW flooded
    rotary screw were originally installed to meet the 24 hour a day air
    requirements of a multi-tenant air system in this industrial park
    setting. Baseline power metering of the existing system indicated
    that the actual capacity requirement of the system could be met with
    a much smaller compressor.

-   The demand side air requirement to be met was defined as 37^º^ F dew
    point air, delivered at a stable and reliable pressure for hand
    tools used in light manufacturing (precision torque assembly,
    milling, grinding, drilling, deburring, polishing and packaging).

# Project Overview

-   A new 60 HP rotary screw compressor with load/unload capacity
    controls, a cycling refrigerated air dryer and 1500 gallons of
    additional air receiver storage volume were selected and
    incorporated into the system to meet system average production and
    peak air demands. Installation of increased air storage receivers
    and a downstream flow controller allowed system supply pressure to
    be reduced 25 psig resulting in a new system supply pressure of 95
    psig that now meets all tenant requirements.

-   Average compressed air system electrical load was reduced from 65 kW
    (24/7) to 8.6 KW (24/7). The resulting new system reduced energy use
    by 492,049 kWh/yr, or \$32,000 per year in reduced electrical costs.

-   Total project cost was \$52,600. With the SnoPUD's energy efficiency
    incentive of \$33,314 Monte Villa Farms received a 100 percent
    return on investment in less than 8 months.

# Project Implementation

-   SnoPUD staff worked with a local equipment supplier along with the
    tenants as a project team. To determine the opportunity, the
    existing compressor motor load, system pressure and flow rates were
    metered for a number of weeks. After analysis, it was determined
    that the average (24/7) air requirements of the system over a
    typical production day were approximately 6% of the 125 HP
    compressor's capacity, or approximately 30 CFM. Observed peak air
    requirements were limited in duration and rarely exceeded 120 CFM.

-   To meet existing air system requirements and to accommodate the
    anticipated air future use of a prospective new tenant, a 60 HP, 125
    PSIG rotary screw compressor with Low Unloaded Horsepower (LUHP)
    controls was selected.

-   It was determined that the existing (2), 240 gallon air storage
    receivers on site provided inadequate system storage volume. A new
    1,000 gallon dry air storage tank and new downstream flow controller
    were piped in to enable the system storage to operate over a 25 psig
    pressure decay differential and maintain a practical and effective
    load/unload cycle frequency during production periods. The
    additional storage allowed the "unload/off" duration of the cycle.
    To maintain adequate system pressure at the far end of the
    manufacturing floor several modifications were made. A remote
    500-gallon air receiver was integrated into the distribution piping
    at the far end of the floor providing additional remote air storage
    to supply the intermittent and high volume demands in the packaging
    area. Attempts to meet this air demand previously had been solved by
    artificially inflating the system supply pressure at the expense of
    increased system leak load, increased tool wear and increased energy
    operating costs.

-   Monte Villa Farms now has a compressed air system that operates at
    high system efficiency, improved part-load performance, and a
    dramatically reduced electrical operating cost, 24 hours a day, 7
    days a week over the range of multiple tenant demand and production
    schedules.

# 

# Monitoring and Verification Approach

-   Baseline power metering of the existing system was conducted over a
    6 week period.

-   Post monitoring was performed to determine actual performance of the
    new compressed air system.

-   The results of this sub-metering confirmed that the actual capacity
    requirement of the system could be met with the new smaller
    compressor.

# Project Results

-   Average compressed air system electrical load was reduced from 65 kW
    (24/7) to 8.6 kW (24/7). The resulting new system reduced energy use
    by 492,049 kWh/yr, or \$32,000 per year in reduced electrical costs
    based on a \$0.065/kWh average rate.

-   ![](media/image2.wmf){width="3.625in"
    height="2.6951388888888888in"}The graph below illustrates the
    dramatic drop in average electricity demand (a kW) that was achieved
    by this project:

# Project Team

-   Holly Jones -- Hibbs/Premier Advisors Property Manager

-   Mark Sheckler \-- Rogers Machinery

-   Dave Hunt -- Snohomish County PUD

# Summary of Project Benefits and Payback

-   Total project cost of \$52,600

-   Electricity savings of 492,049 kWh yr (87 percent reduction)

-   Electricity cost savings of \$32,000/year

-   45 kW demand reduction (Demand cost reduction of \$1,954/year)

-   SnoPUD's energy efficiency incentive was \$33,314

-   Simple Payback = 7.5 months

-   165 percent return-on-investment (ROI)

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SOME PHOTOS BELOW

Engineers survey the existing system showing the two 240 gallon storage
tanks and two air dryers.