Ventilation Retrofit Opportunities for Packaged HVAC

Transcription

1 Ventilation Retrofit Opportunities for Packaged HVAC Reid Hart, PE National Energy Efficiency Technology Summit September 2012 PNNL-SA-90782

2 Acknowledgements Bonneville Power Administration City of Eugene and Eugene Water & Electric Board PECI Premium Ventilation Proof of Concept Field Test (funded by BPA) Benjamin Lipscomb and Kristine Falletta Pacific Northwest National Laboratory Energy Savings and Economics of Advanced Control Strategies for Packaged Air-Conditioning Units with Gas Heat (funded by DOE) Weimin Wang, Lucy Huang, Srinivas Katipamula, and Michael Brambley 2

3 Outline As-found RTU conditions Multiple retrofit control strategies for unitary HVAC DCV with economizer tuning Variable speed fan control Fan cycling control with DCV Potential retrofit savings Advanced options: Occupancy sensor-based control Night flush and demand response Web-based control options for RTUs Semi-automated acceptance testing 3

4 Need for an Advanced RTU Controller Packaged air conditioners and heat pumps (RTUs) are used in about 46% of all commercial buildings, serving about 60% of the commercial building floor space (Source: EIA 2003.) Most RTUs operate inefficiently Lack of equipment maintenance Lack of advanced controls strategies that rely on constant supply speed fan and constant ventilation Operating efficiency can be improved significantly with the use of advanced controls strategies 4

5 Common Problems with RTU Controls Sensors Thermostat Air Flow Economizer Refrigerant Circuit Source: Cowan % 42% 46% 0% 20% 40% 60% 58% 64% % of units tested with problem Mega study covering four studies, 300 units Problems were found everywhere 91% had some problem 64% had two or more problems Significant impact on delivered efficiency Majority of problems come from controls 5

6 Space Temperature / Setpoint, deg F OSA Damper Unoccupied Night Flush Optimum Start (Purge) Occupied Standby Occupied Pre-Demand Demand Recovery Unoccupied Improve Economizer and Fan Performance with Integrated DDC Controls Summer Typical Mode Setpoints OA Damper Space Temp Cool Set Econo Set Heat Set % 160% % 120% 100% 80% % % % % 12:00 AM 2:00 AM 4:00 AM 6:00 AM 8:00 AM 10:00 AM 12:00 PM 2:00 PM 4:00 PM 6:00 PM 8:00 PM 10:00 PM 12:00 AM Source: Hart et al

7 Beyond Tune-Ups and EER: Premium Ventilation Package Premium ventilation specifications: Upgrade the economizer control module with Integrated OSA economizer DCV capability: CO 2 sensor Digital controls with discrete input Fan motor control Variable speed drive operates in a multi-speed mode DCV fan cycling (lower cost) Robust optimum start Acceptance testing to verify proper Ventilation & DCV set up Scheduling and warm-up lockout Field testing completed in Oregon 7

8 It s Time for Stand-Alone Direct Digital Controllers 8 It s time to move beyond old style analog controllers Too many wires up on the roof Too difficult to adjust Sequences not integrated A combined programmable thermostat with a BACnet DDC controller is now available from multiple manufacturers at a reasonable price Digital economizer controllers are now available Improved sequences have been tested Integrated differential economizer Night flush control Robust optimum start

9 DCV with Economizer Tune-Up Digital economizer operation improvement 9 Source: Hart et al Comparison periods of between 14 and 30 days with similar outside temperature averages

10 Fan Control VSD and fan cycling both about the same savings Both require DCV or advanced economizer controller In dx coil RTUs, VSD operates at multi-speed VSD higher cost, better sound impact for space Existing units designed to cycle, VSD retrofit can be a challenge Basic concept on speed control High speed for full cooling or heating Low speed for ventilation or partial cooling (if multi-stage) Savings issue when fan is in auto Not meet ventilation standards, but 37%* of units in Auto Balanced by 30%* units operating 24/7 that are re-scheduled *Jacobs et al

11 Field Results of Fan Cycling Recreation Center in Eugene, Oregon Intermittent occupancy Fans generally in Auto during baseline 11 Source: Hart et al

12 Ventilation Maintained or Improved Test site had high base ventilation and moderately high infiltration in most rooms Two rooms had improved ventilation due to fans operating in Auto during base case 12 Source: Hart et al

13 Are Advanced RTU Controls Cost-Effective? Source: Hart

14 Summary of HVAC Energy Savings Base: Non-integrated economizer, single-speed fan Improved: Integrated economizer, multi-speed fan, DCV Building Type Small office Stand-alone retail Strip mall Supermarket Maximum percentage savings 42% 40% 40% 41% Location for maximum percentage savings Los Angeles Los Angeles San Francisco Miami Minimum percentage savings 20% 23% 21% 14% Location for minimum percentage savings Fairbanks Fairbanks Fairbanks Fairbanks Average percentage savings 28% 32% 32% 22% Maximum absolute savings (MMBtu/yr) 91 1,268 1,165 1,770 Location for maximum absolute savings Fairbanks Fairbanks Fairbanks Fairbanks Minimum absolute savings (MMBtu/yr) Location for minimum absolute savings San Francisco Los Angeles Los Angeles Los Angeles Average absolute savings (MMBtu/yr) Source: Wang et al

15 Summary of HVAC Cost Savings for the Same Case Building Type Small Office Stand-Alone Retail Strip Mall Supermarket Maximum percentage savings 59% 53% 54% 50% Location for maximum percentage savings San Francisco San Francisco San Francisco Los Angeles Minimum percentage savings 27% 30% 29% 27% Location for minimum percentage savings Miami Miami Miami Seattle Average percentage savings 38% 38% 38% 36% Maximum absolute savings ($/yr) $2,108 $21,383 $20370 $46,605 Location for maximum absolute savings Fairbanks Fairbanks Fairbanks Fairbanks Minimum absolute savings ($/yr) $752 $6,868 $6,556 $15,046 Location for minimum absolute savings Seattle Albuquerque Albuquerque Miami Average absolute savings ($/yr) $1,134 $9,481 $9,390 $21, Source: Wang et al

16 Annual HVAC Energy Consumption (10 6 Btus) Comparison of HVAC Energy Consumption Add Multi-Speed Fan and DCV Gas Electricity 20% % 28% 25% 27% 42% 26% 35% 28% 27% 32% 26% 27% 26% 26% 25% 0 Climate Zone and Location Small Office 16 Source: Wang et al

17 RTU HVAC Energy Use and Savings Premium Ventilation Package Example: Sacramento, California office building Apply premium ventilation measure package Baseline Fan & Aux 29% Baseline Heating 28% Remaining Fan & Aux 20% Optimum Start 4% Strip Heat lockout 2% Warmup Cycle 5% DCV 7% Integrated Economizer 12% Baseline Cooling 43% Remaining Cooling 31% VSD fan 9% Remaining Heating 10% 17

18 Regional Electric and Gas Savings Additive measures: DCV and economizer Add fan control (VSD or cycling) Add night flush, optimum start, standby control 18

19 19 Regional Savings: 10-Ton RTU with Gas Heat

20 20 Regional Savings and Payback: 10-Ton RTU with Gas Heat

21 Installed Bid (2010 Real $) Costs for Premium Ventilation with Local DDC and Fan Cycling First time bid costs ranged $1,900 to $3,200 (Manufacturers A, B, C) Expected to become more favorable over time Favorable comparison to advanced thermostat with digital economizer controller (P) $3,500 $2,500 $1,500 A B C P $

22 22 Semi-Automated Acceptance Testing Required

23 23 Better Acceptance Testing Needed

24 Conclusions and Next Steps Potential savings: Upgrading RTU controls has good potential savings ~35% Field testing has verified operation with custom controllers Next steps: Work with manufacturers to lower the cost and the barriers for technology deployment More field testing to verify savings, explore web-based options Contractor training and acceptance tools need improvement Expand impact assessment to packaged heat pumps, more building types, and other control technologies Future Integrate advanced control with fault detection and diagnostics to achieve persistent savings 24

25 Questions? Reid Hart, PE References Cowan, N. Review of Recent Commercial Roof Top Unit Field Studies In the Pacific Northwest and California. New Buildings Institute (NBI) for Northwest Power and Conservation Council [NPCC], October Accessed September 19, 2012 at EIA Commercial Buildings Energy Consumption Survey (CBECS). U.S. Energy Information Administration, September Accessed September 19, 2012 at Hart R Advanced Unitary HVAC Control Sequence. ASHRAE Transactions. Vol. 118, Part 1. Hart R, J Callahan, K Anderson, and P Johanning Unitary HVAC Premium Ventilation Upgrade. ASHRAE Transactions. Vol. 117, Part 1. Hart R, K Falletta, and B Lipscomb RTU Premium Ventilation: Proof of Concept Field Test. Portland Energy Conservation, Inc. for Bonneville Power Administration, Portland, Oregon. Hart R Premium Ventilation Package Testing: Short-Term Monitoring Report Task 7. Portland Energy Conservation, Inc. for Bonneville Power Administration, Portland, Oregon. Accessed September 19, 2012 at Hart R, W Price, J Taylor, H Reichmuth, and M Cherniack Up on the Roof: From the Past to the Future. In Proceedings of the 2008 ACEEE Summer Study on Energy Efficiency in Buildings, pp American Council for an Energy-Efficient Economy, Pacific Grove, California. Hart R, W Price, and D Morehouse The Premium Economizer: An Idea Whose Time Has Come. In Proceedings of the 2006 ACEEE Summer Study on Energy Efficiency in Buildings, pp American Council for an Energy- Efficient Economy, Pacific Grove, California. Jacobs, P., V. Smith, and C. Higgins. Small Commercial Rooftops: Field Problems, Solutions and the Role of Manufacturers. In National Conference on Building Commissioning: May, 20:22, Wang W, S Katipamula, Y Huang, and M Brambley Energy Savings and Economics of Advanced Control Strategies for Packaged Air-Conditioning Units with Gas Heat. PNNL-20955, Pacific Northwest National Laboratory for the U.S. Department of Energy. Accessed September 19, 2012 at 25