Welcome to the Webinar on Energy Saving Calculations for Existing Building Commissioning February 19, 2013 Gustav Brändström, PE Angela Vreeland, PE We’ll start the presentation shortly. Hover your cursor at the top of your screen to access the WebEx menu bar and open your Chat window. We will end with an open discussion, but feel free to ask clarifying or technical support questions during the presentation through your Chat window.
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Energy Savings Calculations for Existing Building Commissioning
Engineers Angela Vreeland and Gustav Brändström demonstrate common traps and tricks in dealing with trend data, along with detailed calculations that can be applied to a variety of energy saving measures.
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Welcome to the Webinar on Energy Saving Calculations for Existing Building Commissioning
February 19, 2013
Gustav Brändström, PE
Angela Vreeland, PE
We’ll start the presentation shortly.
Hover your cursor at the top of your screen to access the WebEx menu bar and open your Chat window.
We will end with an open discussion, but feel free to ask clarifying or technical support questions during the presentation through your Chat window.
Energy Saving Calculations for Existing Building Commissioning
February 19, 2013
Gustav Brändström, PE
Angela Vreeland, PE
Page 3
Introduction Why use spreadsheet calculations? Trending and Trend Data TMY and Bin Data Top Energy Saving Measures in EBCx
AHU Measure Optimize Airside Economizer
Pump Measure Install VFD on Hot Water Pump
Wrap-up Questions
Agenda
Agenda
Page 4
Customizable for any application Can be based on actual building operation Applicable to multiple scenarios with little modification TRAP: Do not double count savings! Remember to
include interactions between findings and equipment. Scheduling > Controls changes > Retrofits Central system > Major equipment > Terminal equipment
Introduction
Why Use Spreadsheet Calculations?
Page 5
Most 3rd party tools apply to specific scenarios “Square peg in round hole” All inputs must be re-entered for each case
Energy modeling is not economical for analysis of individual equipment Time-consuming Not intent of modeling software
Introduction
Why Use Spreadsheet Calculations?
Page 6
Trending – brief overview The process of capturing time series data on equipment
operation Data is exported from a Building Automation System (BAS)
or data loggers for spreadsheet analysis Data set-up, collection, processing, and analysis are time
consuming Allows us to understand how the equipment operates
See the Innovation Exchange’s Webinar on Trending titled: Using Building Automation Systems as a Cx Tool
Trending and Trend Data
Introduction
Page 7
Why use trend data? Trend data allows you to identify operational issues you
wouldn’t find otherwise. Functional performance tests and other tools can’t capture all
modes of operation
Trend data allows you to more accurately calculate savings
Trending and Trend Data
Introduction
Page 8
Energy savings calculations are based on OAT Typical Meteorological Year Weather Data
Normalized weather Covers at least 15 year timeframe Average and typical, not average
“Major” cities only Get from NREL
http://www.nrel.gov/rredc/solar_data.html
Bin Data Grouped or “binned” data Increments vary depending on system characteristics
TRICK: AVERAGEIFS() and COUNTIFS() in Excel These functions make creating bins out of data super easy!! AVERAGEIFS() - Average value of a range, given criteria COUNTIFS() - Number of occurrences in a range, given criteria
Introduction Why use spreadsheet calculations? Trending and Trend Data TMY and Bin Data Top Energy Saving Measures in EBCx
AHU Measure Optimize Airside Economizer
Pump Measure Install VFD on Hot Water Pump
Wrap-up Questions
Agenda
Agenda
Page 11
AHU Measure
Top Energy Saving Measures in EBCxKey Measure Mix % of Total Savings
Revise control sequence 21%
Reduce equipment runtime 15%
Optimize airside economizer 12%
Add/optimize SAT reset 8%
Add VFD to pump 6%
Reduce coil leakage 4%
Reduce/reset DSP setpoint 4%
Add/optimize optimum start/stop 3%
Add/optimize CWST reset 2%
Source: A Study on Energy Savings and Measure Cost Effectiveness of EBCx, PECI, 2009
Page 12
Four most common high limit control strategies Fixed Drybulb Temperature- OAT Differential Drybulb Temperature- OAT vs RAT Fixed Enthalpy- OAh
Enthalpy is calculated from drybulb temperature and humidity
Differential Enthalpy- OAh vs RAh
AHU Measure
Optimize Airside Economizer
???
Page 13
Economizers malfunction frequently Stuck outside damper Outside air (OA) flow measuring station error Temperature or humidity
sensor out of calibration
AHU Measure
Optimize Airside Economizer
Page 14
Economizer control errors are common Incorrect high and/or low limit setpoint Incorrect minimum outside air setpoint Lockout between economizer and mechanical cooling
Result in A loss of “free cooling” opportunity Increased cooling load Increased heating load
AHU Measure
Optimize Airside Economizer
Page 15
How do we know if something is wrong? Calculate the %OA
where:OAT = Outside Air TemperatureRAT = Return Air TemperatureMAT = Mixed Air Temperature
Plot %OA against OAT and look at the pattern
AHU Measure
Optimize Airside Economizer
Page 16
Economizer Lockout ~ 70°F
- IDEAL PATTERN
Page 17
Why should the high limit setpoint be ~70°F? High limit of 71°F in MN was found to be ideal
Taylor Engineering Research Best economizer control strategy is provided for each region November 2010 ASHRAE Journal (Vol. 52, No. 11)
TRAP: Humidity Sensors are Error-Prone Avoid enthalpy high limit control Iowa Energy Center Research http://www.iowaenergycenter.org/wp-content/uploads/2012/05/
PTR_Humidity_Rev.pdf
AHU Measure
Optimize Airside Economizer
Page 18
Finding (problem) Economizer high limit lockout is 80°F
Measure (solution) Change the lockout to 70°F
AHU Measure
Optimize Airside Economizer Example
Page 19
Lower the High Limit Setpoint: 80°F to 70°F
- HIGH LIMIT TOO HIGH
Page 20
Spreadsheet Calculation Layout Reducing the high limit setpoint will lead to savings whenever
the outside air damper is open more than it should be
CurrentColumn D- Average RAT during Bin Obtain from trends of RAT and OAT Plot RAT vs OAT to see overall pattern Use AVERAGEIFS- Filter for when AHU is ON
Summary Economizers malfunction often, but fixing them is typically
very easy and cost-effective
Additional considerations…. Sometimes fixing the issue leads to more energy use An AHU may economize at OATs as low as 20 or 30°F The fewer sensors the economizer relies on, the better
AHU Measure
Optimize Airside Economizer
Page 31
Introduction Why use spreadsheet calculations? Trending and Trend Data TMY and Bin Data Top Energy Saving Measures in EBCx
AHU Measure Optimize Airside Economizer
Pump Measure Install VFD on Hot Water Pump
Wrap-up Questions
Agenda
Agenda
Page 32
Pump Measure
Top Energy Saving Measures in EBCxKey Measure Mix % of Total Savings
Revise control sequence 21%
Reduce equipment runtime 15%
Optimize airside economizer 12%
Add/optimize SAT reset 8%
Add VFD to pump 6%
Reduce coil leakage 4%
Reduce/reset DSP setpoint 4%
Add/optimize optimum start/stop 3%
Add/optimize CWST reset 2%
Source: A Study on Energy Savings and Measure Cost Effectiveness of EBCx, PECI, 2009
Page 33
Constant volume pumping is common in existing buildings.
Hot water loops come in many variants; primary, primary/secondary, primary/tertiary, etc.
Energy savings from reducing the pump speed Opportunities exist when the
drop in temperature is low
Pump Measure
Install VFD on Hot Water Pump
Page 34
TRICK: Plot HW dT vs OAT. Example of low temperature drop
Design Loop dT = 48°F
Page 35
Constant volume pumping is common in existing buildings.
Hot water loops come in many variants; primary, primary/secondary, primary/tertiary, etc.
Energy savings from reducing the pump speed Opportunities exist when the
drop in temperature is low, and/or use in the AHUs are low.
Pump Measure
Install VFD on Hot Water Pump
Page 36
TRICK: Plot # of AHUs heating vs OAT. Example of Low use of heating at the AHUs
Page 37
Example Finding (problem)
Secondary Hot Water Loop Pump runs excessively
Measure (solution) Install VFD on 40hp Pump, close off three way valves, and install
Summary of Measure Keep the pump running at as low of a speed as possible TRICK: In conjunction with adding a VFD, look at the scheduling. TRAP: If there are different modes of operation, account for them!
(Morning Warm-up, freeze protection, etc.) SAVE LOTS OF ENERGY!
Implementation cost $29,000 (incl. commissioning)
Energy Savings $12,100 Simple Payback 2.4 years
Pump Measure
Install VFD on Hot Water Pump
avreeland
Is this example-specific or general? I think the traps and tricks should be general so that they can be applied to many different situations...
Page 48
Introduction Why use spreadsheet calculations? Trending and Trend Data TMY and Bin Data Top Energy Saving Measures in EBCx
AHU Measure Optimize Airside Economizer
Pump Measure Install VFD on Hot Water Pump
Wrap-up Questions
Agenda
Agenda
Page 49
Introduction
Target High Energy Savings MeasuresKey Measure Mix % of Total
Savings
Revise control sequence 21%
Reduce equipment runtime 15%
Optimize airside economizer 12%
Add/optimize SAT reset 8%
Add VFD to pump 6%
Reduce coil leakage 4%
Reduce/reset DSP setpoint 4%
Add/optimize optimum start/stop
3%
Add/optimize CWST reset 2%
Source: A Study on Energy Savings and Measure Cost Effectiveness of EBCx, PECI, 2009
TRICKs
Focus on:• Large equipment (high
horsepower, tonnage, etc)
• Equipment that runs a lot
Do a test calculation:
• Estimate savings and costs
• Is the payback reasonable?
Page 50
California Commissioning Collaborative www.cacx.org
Better Bricks www.betterbricks.com
Taylor Engineering www.taylor-engineering.com
Portland Energy Conservation, Inc - PECI www.peci.org
Wrap-up
Resources
Page 51
Trending Invaluable tool
Identify operational issues Calculate accurate energy savings
Spreadsheet Calculations Straightforward Flexible Accurate Worth the investment in development
Wrap-up
Conclusion
(and spreadsheets)
Page 52
Questions?
Energy Saving Calculations for Existing Building Commissioning