Draft
STANDARD SAVINGS ESTIMATION PROTOCOL FOR
VARIABLE SPEED AIR COMPRESSOR
Submitted to
REGIONAL TECHNICAL FORUM
Submitted by
SBW CONSULTING, INC.
2820 Northup Way, Suite 230
Bellevue, WA 98004
January 28, 2011
Standard Savings Estimation Protocol For Variable Speed Air Compressor
TABLE OF CONTENTS
1. PURPOSE............................................................................................................ 1
2. DEFINITION OF KEY TERMS ..................................................................................... 1
3. ELIGIBLE PROJECTS ............................................................................................... 1
4. REQUIRED KNOWLEDGE AND SKILLS OF PRACTITIONER ................................................... 2
5. REQUIRED COMMISSIONING .................................................................................... 2
6. DATA COLLECTION REQUIREMENTS ........................................................................... 2
6.1. Compressor Specifications ................................................................................................. 2
6.2. Compressed Air System Operations .................................................................................. 3
6.3. Electrical Measurements ................................................................................................... 3
6.4. Inputs for Cost-Effectiveness Analysis ............................................................................... 3
7. PROVISIONAL DATA REQUIREMENTS ......................................................................... 4
8. SAVINGS ESTIMATION STEPS ................................................................................... 4
8.1. Compute Energy Use for Trend Log Intervals .................................................................... 4
8.2. Annualized Energy Savings................................................................................................. 4
8.3. Life Cycle Costs and Benefits ............................................................................................. 5
9. SAMPLING PROCEDURE .......................................................................................... 5
10. RELATIONSHIP TO OTHER PROTOCOLS AND GUIDELINES ............................................... 5
11. TYPICAL COST OF APPLYING THIS PROTOCOL ............................................................. 5
12. USER’S GUIDE TO THE SAVINGS CALCULATOR ............................................................ 6
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Standard Savings Estimation Protocol For Variable Speed Air Compressor
1. PURPOSE
This protocol establishes a method by which annual electrical energy savings (kWh) can be estimated for
a compressed air system that has been upgraded by the addition of a Variable Speed (VS) air
compressor. Variable speed air compressors reduce electric use by adjusting the compressor motor’s
speed to match the required load. The part load performance of a VS compressor is more efficient than
part-load performance of air compressors with other output control schemes such as modulation or
loading and unloading.
This protocol specifies minimum acceptable data collection requirements and the method by which
these data are to be used in computing savings. For some data elements, alternative sources of data are
also defined and are allowed. Savings are computed using the Excel workbook (to be developed) that
accompanies this document to ensure standardized application of the savings estimation methods.
2. DEFINITION OF KEY TERMS
Project. The project consists of the installation of a single VS compressor in a compressed air system
that is served by one or more compressors. The variable speed compressor shall always be the trim
machine, which is the only machine in the system allowed to run at partial capacity. It may also
comprise other improvements to the compressed air system such as reductions in pressure, leak load
and inappropriate uses. However, in those cases the protocol yields an estimate of the total savings
from all improvements.
Baseline. This modifier; as in baseline control strategy refers to the period prior to the upgrade.
Post. This modifier; as in post power trend log, refers to the period after the VS compressor upgrade is
installed and fully commissioned.
Commissioning. This is the process of testing and adjustment required to ensure that the VS
compressor is operating according to its design intent.
3. ELIGIBLE PROJECTS
The following criteria define eligible projects.

All electric-powered non-VS baseline compressor types are eligible.

Production hours and operating production equipment must be similar in baseline and post periods.

All types of facilities are eligible, including those with seasonal variations in production.

The cost of implementing this protocol must not make the project economically unattractive.
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Standard Savings Estimation Protocol For Variable Speed Air Compressor
4. REQUIRED KNOWLEDGE AND SKILLS OF PRACTITIONER
The practitioner who has lead responsibility for applying this protocol must have a full understanding of
the following:

Appropriate safety procedures for work involving compressed air systems and the measurement
equipment required by this protocol

This protocol and the accompanying savings calculator.
The practitioner must also be able to successfully perform the following tasks:

Identify the variable speed compressor.

Identify the seasonal production schedule.

Supervise a licensed electrician in installing true power transducers on circuits serving the system’s
compressors.

Operate data logger(s) to collect power and pressure measurements.
5. REQUIRED COMMISSIONING
This protocol may only be used for projects that pass the following commissioning tests:

The practitioner confirms by interviewing the installation contractor that the work included
establishing control settings (sequencing and capacity control) for all other compressors in the
system to ensure that the variable speed compressor is the only trim compressor.

The practitioner will observe the compressor’s control panel for a reasonable period to confirm that
the displayed operating status indicator (kW, amps or speed) drops as the displayed pressure
increases and increases as the displayed pressure decreases. Displayed pressures should not vary by
more than 3 psi from the set point pressure value obtained from the system operator.
6. DATA COLLECTION REQUIREMENTS
The following data must be collected and entered into the savings calculator. The minimum acceptable
procedure for obtaining the data is specified. In some cases, alternative procedures are allowed which
would provide data of equal quality.
6.1. Compressor Specifications

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Variable Speed Compressor. By inspection, identify the variable speed compressor, to support
commissioning in Section 5.
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Standard Savings Estimation Protocol For Variable Speed Air Compressor
6.2. Compressed Air System Operations

Calendar Periods by Production Mode. Some compressed air systems may operate differently
across seasons of the year. For example, a system for a winery may operate differently during the
crush and the bottling seasons. Obtain from the facility operator the typical start and end dates for
each production mode.

Calendar Periods for Scheduled Facility Maintenance. Obtain start and end dates for scheduled
maintenance periods during which compressed air system operations is atypical.
6.3. Electrical Measurements

Trend Log of Motor Power. Install transducers and data loggers to measure poly-phase true RMS
power on the circuits powering all compressors. Set the data loggers to record average power for
each 60-minute interval, with power sampled at least once per minute. Power logging must occur
for at least three consecutive weeks (504 hours) during each production mode (see section 6.2).

Alternative Measurements.

Control System Log. In lieu of data logging, power measurements may also be obtained from
the facility control systems trend logs. The same measurement interval, period and timing
requirements apply as described for the power measurement above.
6.4. Inputs for Cost-Effectiveness Analysis
The following data need to be gathered to support the cost/benefit analysis feature of the calculator.

Project completion date.

Measure cost. The initial cost of installing the new equipment, including all materials and labor
costs. This is the full cost of the VS compressor installation. This value must be supported by
invoices or other documentation.

Sector. Possible values are Agricultural, Industrial, and Commercial.
The following values are used in the cost-effectiveness calculation, but are pre-set in the calculator.

Electric shape. The calculator assigns an appropriate electric shape based on compressor operation
data described in section 6.2 and the profile of savings computed from the trend log data.

Periodic costs or savings. Any non-annual periodic costs associated with the measure, and the
associated time period. These are incremental costs of the efficient option over the costs of the
baseline. For a VS compressor, the calculator restricts this value to be zero.

O&M costs or savings. Annual O&M costs or savings associated with the measure. These are costs
or savings which occur with the efficient option that would not occur with the baseline option, i.e.
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Standard Savings Estimation Protocol For Variable Speed Air Compressor
the costs associated with VS compressor drive maintenance. The calculator restricts this value to be
zero.

Non-energy benefits. Annual non-energy related costs or savings associated with the measure. The
calculator restricts this value to be zero.

Measure life. Number of years the measure is expected to be in effect. For a VS compressor, the
calculator restricts this value to be 10 years.
7. PROVISIONAL DATA REQUIREMENTS
During the period that the RTF classifies this protocol as Provisional, the following data requirements
will be in force:

None.
8. SAVINGS ESTIMATION STEPS
Savings are estimated using the savings calculator that accompanies this protocol (To be developed).
Savings are estimated as follows.
8.1. Compute Energy Use for Trend Log Intervals
The following steps are completed separately on both the baseline trend data and the post trend data.

Data Synchronization. Start times for all trend log intervals are synchronized by adjusting each to
the closest hour.

Truncate to Data Period. Discard hourly measurements beyond the three week measurement
period so that the days of the week are proportionally represented.
8.2. Annualized Energy Savings

Hours by Production Mode. Compute the number of hours between the start and end dates for
each production mode. (Section 6.2).

Adjust for Scheduled Maintenance. Subtract hours of scheduled maintenance from any production
mode hour totals within which scheduled maintenance occurs.

Hourly Average Energy Use by Production Mode. Sum the hourly kW measurements and divide by
504 (hours in a three-week period), for each production mode in the baseline and post periods.

Average Hourly kW Savings. Compute the difference between baseline and post periods for each of
the production modes.
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Standard Savings Estimation Protocol For Variable Speed Air Compressor

Annualized Savings. Multiply average hourly kW savings, for each production mode, by the annual
hours in each mode. Sum the product for all production modes to compute annual savings.
8.3. Life Cycle Costs and Benefits
The calculator contains a model called ProCost which computes life cycle costs and benefits. Inputs to
the model include the estimates of first-year savings described in section 8.2 and the cost-effectiveness
input data described in section 6.4. ProCost computes life cycle costs and benefits from the economic
perspectives of the end user, utility, and region. The calculator can be used to review these results.
9. SAMPLING PROCEDURE
No sampling is allowed for this protocol. Data collection and savings estimation is required for all
compressors operating in any system receiving a new VS compressor.
10. RELATIONSHIP TO OTHER PROTOCOLS AND GUIDELINES
The relationship between this protocol and other relevant protocols and guidelines is as follows:

International Performance Measurement and Verification Protocol – 2007 (IPMVP), Efficiency
Valuation Organization. This protocol is consistent with Option A - Retrofit Isolation: Key Parameter
Measurement described in the IPMVP, as a key parameter is measured (compressor power).
11. TYPICAL COST OF APPLYING THIS PROTOCOL
Shown below is an estimate of typical cost for a variable speed air compressor replacement. Cost is
higher for a site with multiple air compressors on the affected compressed air distribution system. For
sites that involve significant variations in production levels across the year, additional expenses will
occur for multiple site trips to obtain trend data at different production levels. The assumptions made
for this estimate are: a total of four visits to the site for installation and removal of measurement
equipment, pre and post, three compressors instrumented, a single operating mode pre and post, and
the use of an on-site electrician for installation of power transducers.
Item
Quantity $ / Hour Rental Total Cost
Equipment
Power Loggers
400
400
Labor
Practitioner
Travel
8
110
880
Scheduling
2
110
220
Facility Operator Interview
1
110
110
Inspection
2
110
220
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Standard Savings Estimation Protocol For Variable Speed Air Compressor
Item
Quantity $ / Hour Rental Total Cost
Install/Remove Loggers
4
110
440
Savings Estimate
4
110
440
2
90
180
Electrician
Electrical Measurements
Total
$2,890
12. USER’S GUIDE TO THE SAVINGS CALCULATOR
[To be developed once this protocol is finalized and savings calculator is developed. This Guide and the
Calculator are outside the scope of SBW’s current contract.]
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