1. Active beams versus VAV with Reheat Analysis of May 2013 ASHRAE Journal article Ken Loudermilk Vice President, Technology & Developement

2. Pre-treated Primary Air Entrained Room Air Supply Air to Room 1 Part 3 to 5 Parts 2 to 4 Parts Air handling unit 0.4 to 0.7 in. SP Active Chilled Beams

3. Cost to transport cooling with water 15 to 20% that of air 1“ Dia. Water Pipe 14“ x 14“ Air Duct Comparison of water to air as a heat transfer medium

4. Primary airflow requirement is the greater of: Volume flow rate needed to maintain mandated ventilation to space Volume flow rate needed to offset space sensible heat gains Sensible cooling contribution Drive induction of room air through coil Volume flow rate needed to maintain space dew point temperature Pre-treated primary air Typical active beam cooling operation

5. 67% of space sensible heat removal by water 33% of space sensible heat removed by primary air ACB with 55˚F primary air

6. Office/classroom building at UC Davis 56,500 ft 2 building Sensible loads average 19.5 Btu/h-ft 2 Occupancy is one person per 275 ft 2 Compares VAV + reheat to ACB system with DOAS Analyzes and compares System first cost System energy use Other benefits of VAV + R Active beams with a DOAS vs. VAV with reheat ASHRAE Journal, May 2013

7. Sensible design (outdoor air) 100˚F DB/70˚F WB (54˚F dew point) Humidity ratio W = 62.2 grains/lbm-DA Enthalpy h = 33.8 Btu/h-lbm Off peak operation (outside air) 50% indoor sensible load 77˚F DB/59˚F WB (46˚F dew point) Humidity ratio W = 46.3 grains/lbm-DA Enthalpy h = 25.8 Btu/h-lbm

8. Active beams with a DOAS vs. VAV with reheat ASHRAE Journal, May 2013 100% OA (DOAS) air handling unit No energy recovery! Primary air 63˚F, 54˚ DP (W = 2.7 grains) 0.15 CFM/ft 2 for ventilation 0.53 CFM/ft 2 for latent cooling!! Primary airflow 30,000 CFM (0.53 CFM/ft 2 ) Constant air volume, no set back No DCV provisions Mixing AHU with VFD Equipped with airside economizer Primary air 55˚F, 52˚ DP (ΔW = 8 grains) 0.15 CFM/ft 2 for ventilation 0.18 CFM/ft 2 for latent cooling Primary airflow 50,000 CFM (0.88 CFM/ft 2 ) Normal VAV turndown ratio of 6:1 Interior terminals DCV (allows shut off) VAV + reheat systemACB system

9. Active beams with a DOAS vs. VAV with reheat ASHRAE Journal, May 2013 Performance comparison of systems as described

10. Ventilation 0.15 Dehumidification 0.18 0.53 Sensible Cooling 0.601.75 0.22 0.53 Design airflow rates in CFM PA per square foot Primary air conditions and flow rates as described by authors Resultant Airflow 0.601.75 Avg. 0.88 CFM/ft 2 0.53 Avg. 0.53 CFM/ft 2 VAV System Interior SpacePerimeter Space ΔW = 7.9 grains 55˚ DB/52˚ DP ACB System Interior SpacePerimeter Space ΔW = 2.7 grains 63˚ DB/54˚ DP

11. Air handling unit configurations as described VFD 30,000 CFM 8,300 CFM Relief Fan 8,475 to 50,000 CFM 0 to 41,700 CFM recirculation Bypass Damper Fan Array Cooling Coil Heating Coil OA Filters 30,000 CFM (0.53 CFM/Ft 2 ) 63⁰F Fan Array Cooling Coil Filters 8,300 CFM 8,475 to 50,000 CFM (0.15 to 0.88 CFM/Ft 2 ) 55⁰F Note: 100% OA, no energy recovery!Note: OA requirement only 0.15 CFM/Ft 2, 16% of design airflow rate!

12. Authors‘ performance conclusions Energy use comparable ACB system more than double

13. Authors‘ performance conclusions

14. Energy use comparable ACB system more than double

15. Actual performance comparisons Operational Energy use, kW 100 90 80 70 60 50 40 30 20 10 0 Sensible Design PerformanceLatent Design PerformanceShoulder Season Performance 52.0 VAVR system 79.2 ACB system as designed 41.2 19.4 VAVR system ACB system as designed 88.0 VAVR system 89.9 ACB system as designed

16. What’s wrong with this picture? ACB system primary airflow rate as designed is driven by space latent load combined with low ΔW Primary airflow rate is 75% greater than that typically required by properly designed ACB systems Beam water side cooling capacities (23.6 Btu-h-CFM) as designed are far lower than those (40 to 50 Btu/h-CFM) in properly designed ACB systems

17. Active beams with a DOAS vs. VAV with reheat ASHRAE Journal, May 2013 Performance comparison with properly designed ACB system

18. Air handling unit modifications for ACB system 8,300 CFM VFD 16,667 CFM Fan Array Cooling Coil Heating Coil OA Filters Bypass Damper 30,000 CFM 16.667 CFM (0.3 CFM/Ft 2 ) 55⁰F Fan Array Cooling Coil Filters Relief Fan 8,475 CFM 16.667 CFM 16,667 CFM 8,192 CFM recirculation (0.3 CFM/Ft 2 ) 55⁰F Reduce SAT to 55˚F Lower PA dew point allows primary airflow reduction of 45% and an associated fan energy reduction of 70%! Introduce mixing at AHU Mixing results in an additional 30% reduction in chiller energy!

19. Leveling the playing field Same primary air conditions used for both systems ACB system primary airflow rate reduced from 30,000 CFM to 16,950 CFM! Beam water side cooling capacity (44 Btu-h-CFM) increased by 86%

20. 0.15 0.18 0.20 0.60 Design airflow rates in CFM PA per square foot Primary air conditions and flow rates for modified ACB system 0.20 0.60 Avg. 0.30 CFM/ft 2 Ventilation 0.15 Dehumidification 0.18 Sensible Cooling 0.601.75 Resultant Airflow 0.601.75 Avg. 0.88 CFM/ft 2 VAV System Interior SpacePerimeter Space ΔW = 7.9 grains 55˚ DB/52˚ DP ACB System Interior SpacePerimeter Space ΔW = 2.7 grains 55˚ DB/52˚ DP

21. Actual performance calculations 30% less than VAVR 38% less than VAVR Same as VAVR Was more than double 6% more than VAVR 34% less than VAVR

22. Actual performance comparisons using modified ACB system Operational Energy use, kW 100 90 80 70 60 50 40 30 20 10 0 Sensible Design PerformanceLatent Design PerformanceShoulder Season Performance 62.1 ACB system, 55˚F PA 54.5 ACB system, AHU mixing 51.5 ACB system, 55˚F PA 31.8 ACB system, AHU mixing 22.0 ACB system, 55˚F PA 22.0 ACB system, AHU mixing 52.0 VAVR system 79.2 ACB system as designed 41.2 19.4 VAVR system ACB system as designed 88.0 VAVR system 89.9 ACB system as designed

23. Active beams with a DOAS vs. VAV with reheat ASHRAE Journal, May 2013 System cost comparisons

24. Authors’ installed cost comparison of the systems as designed

25. System ductwork configuration 900 FPM 0.53 CFM/Ft 2 2,000 FPM @ 0.9 CFM/Ft 2 ACB System Mains A EFF = 30,000/900 = 33.3 VAV System Mains A EFF = 50,000/2,000 = 25.0 Authors’ conclusion: Average duct cross sectional area 33% greater for the ACB system Two supply risers One supply riser

26. Ductwork configuration 2,000 FPM ACB System Mains A EFF = 16,667/2,000 = 8.3 VAV System Mains A EFF = 50,000/2,000 = 25 VAVR system average duct cross sectional area is triple that of the ACB system when sized for the same maximum velocity

27. Beam requirements Number of beams reduced by 63% by modifying ACB system 63% reduction in beam piping and insulation costs

28. Remedies for other cost inequities Perimeter VAV terminals serve multiple offices Interior VAV terminals have no reheat provisions Perimeter VAV terminals require only one HW connection per zone No indication of thermal zoning or condensation prevention in ACB system Four pipe configuration of interior space beams Remedy: Eliminate heating provision on interior beams Eliminates HW piping/insulation and connection to interior beams Perimeter beams require individual HW connections Accomplish perimeter heating by heating primary air Reduces HW piping/insulation and connections to one per perimeter zone

29. Cost comparison using modified ACB system Modified ACB system cost assumes the cost per CFM for the ACB system remains constant and thus system costs are proportional to the reduced primary airflow requirements. These costs also do not include any possible reheat piping reduction opportunities discussed before.

30. Installed cost comparison (ACB system with mixing AHU, no ER)

31. Article in winter 2013 High Performance Buildings UC Davis Health and Wellness Center 73,112 ft 2 of conditioned space LEED-NC Gold Occupied since March 2010 DOAS air handling strategy Energy performance Projected 35% better than LEED baseline Actual 31% better than projected 70% less primary air than VAV system

32. Chilled beams! And the hands down winner is………

33. Questions?

34. Active beams versus VAV with Reheat Analysis of May 2013 ASHRAE Journal article