Field measurement and modeling of UVC cooling coil irradiation for heating, ventilating, and air conditioning energy use reduction (RP-1738)—Part 2: Energy, indoor air quality, and economic modeling

Figures & data

Table 1. Baseline rates of work absence.

Classification	#/person-year	Source
WLD (ages 18–64)	2.172	Adams et al. (1999) and US Bureau of the Census (1997) cited in US EPA(2008)
WLD (ages 18–64)	3.670	Blackwell, Lucas, and Clarke (2014) for the CDC (Centers for Disease Control and Prevention)
Paid sick days	4.200	Barthold and Ford (2012) for the BLS (Bureau of Labor Statistics).

Table 2. Considered levels of ΔP effect due to fouling.

Designation	ΔP increase due to fouling	Location/climate zone	Reference
ΔP lower bound	20% of clean coil ΔP	Tampa, FL / 2A	Firrantello et. al. (2017)
ΔP upper bound	156% of clean coil ΔP	Orlando, FL / 2A	Keikavousi (2004)

Table 3. Characteristics of selected DOE commercial reference buildings.

Building type	Floor area[ft^2][m^2]	Floors	Heating	Cooling	Air distribution	Systems
Large office	498,58846,344	12	Boiler	Chiller (2)–water cooled	MZ VAV	4
Medium office	53,6284985	3	Furnace	PACU (packaged air-conditioning unit)	MZ	3
Small office	5,500511	1	Furnace	PACU	SZ CAV	5
Primary school	73,9606874	1	Boiler	PACU	CAV and VAV	3 CAV4 VAV
Secondary school	210,88719,602	2	Boiler	Chiller–air cooled	MZ VAV	5 CAV4 VAV
Hospital	241,35122,434	5	Boiler	Chiller–water cooled	CAV and VAV	2 VAV2 CAV
Outpatient health care	40,9463806	3	Furnace	PACU	VAV	2

Note: Abbreviations used in Table 3 include VAV (variable air volume), CAV (constant air volume), MZ (multi-zone), and SZ (single zone).

Fig. 1. Flow diagram of IAQ simulation process.

Table 4. LCCA scenarios.

ΔP lower bound	ΔP upper bound
UVGI without IAQ benefit	UVGI without IAQ benefit
UVGI with IAQ benefit	UVGI with IAQ benefit
Mechanical cleaning lower bound	Mechanical cleaning lower bound
Mechanical cleaning upper bound	Mechanical cleaning upper bound

Table 5. LCCA parameters.

General parameter	Value	Notes
Real discount rate	3%	Estimated by US Department of Commerce (NIST 2015)
Analysis period	20 years	From ASHRAE (2015a)
Energy cost rates	Varies	Location-specific tariffs included in the DOE Commercial Reference Building models are used with adjustment from 2004 to 2015 cost based on US EIA data (2016a, 2016). Census Region-specific energy rate escalation factors are used (NIST 2015).
UVGI Parameter	Value	Notes
First cost	$10/installed watt	Estimate from industry source
Annual replacement (capital)	$1/installed watt	Estimate from industry source
Annual replacement (labor)	$50 per person-hour, 0.5 person-hours per coil	Estimated time on labor based on professional judgement
Annual UVGI lamp energy	Varies	Uses installed total lamp wattage. Running whenever the building is occupied.
Annual utility savings	Varies	From energy model comparisons
Annual IAQ related savings	Varies	Calculated via stochastic analysis as described previously
Mechanical Cleaning
Parameter	Value	Notes
Annual cost (lower bound)	Varies from $56–$110 per coil	Based RS Means Facilities Maintenance and Repair Cost Data (2013)
Annual cost (upper bound)	$750 per coil, total	Approximate cost to clean Tampa field site coil once per year
Annual utility savings	One-half energy savings of UVGI scenarios	Assume effect of coil fouling increases linearly between cleanings

Table 6. Parameters used in mechanical cleaning lower bound estimate.

Parameter	Value	Notes
Labor hours	0.38 for <50-ton capacity0.51 for ≥50-ton capacity	From section D045 110 (RS Means 2013). Listed labor hours are for a combination of small maintenance tasks that included cleaning coils. Labor hours for coil cleaning were not broken out individually. Decision was made based on professional judgment to use total labor hours as-is, as 30 minutes was estimated a reasonable time needed to clean a coil.
Labor rate	$56.65 + 55.6% O&P = $88.15	STPI (steamfitter or pipefitter) rate used for HVAC maintenance work in RS Means. Assume cleaning is not performed in-house.
Material cost	$30 + 10% markup = $33	Cost of material needed to clean one coil according to discussions with facilities personnel.
Location factor	Varies	Varies based on location. Separate labor and material adjustment factors are used.
CPI adjustment from 2013 values to 2015 values	237.017/232.957 = 1.017	US consumer price index (BLS 2015) used to adjust values from 2013 RS Means to 2015 values.

Table 7. Summary of HVAC energy savings.

	ΔP lower bound		ΔP upper bound
	Mean	Median	Mean	Median
Cooling	0.63%	0.44%	4.50%	3.20%
Fan	3.59%	3.39%	22.20%	21.49%
Pump	0.47%	0.34%	1.89%	2.53%
Heating	−0.35%	−0.11%	−3.69%	−1.07%
HVAC	0.68%	0.47%	4.59%	3.53%

Fig. 2. Mean modeled net energy savings using ΔP lower bound and ΔP upper bound. Net includes the savings from the cooling, fan, and pump subsystems, and the energy penalty due to the heating and UVGI subsystems.

Fig. 3. Modeled mean subsystem annual energy use savings due to UVGI for ΔP lower bound. Positive values indicate energy savings and negative values indicate energy penalty.

Fig. 4. Modeled mean subsystem annual energy use savings due to UVGI for ΔP upper bound.

Fig. 5. Relation between OA fraction and metric improvement for Chicago climate.

Fig. 6. Relation between OA fraction and metric improvement in medium office building.

Table 8. Annual economic benefit per unit area by building type (all climates).

Building type	Mean[$/ft^2] / [$/m^2]	Median[$/ft^2] / [$/m^2]	Standard deviation[$/ft^2] / [$/m^2]
Small office	0.140/1.510	0.123/1.329	0.073/0.781
Medium office	0.056/0.606	0.058/0.625	0.022/0.241
Large office	0.013/0.137	0.013/0.135	0.006/0.062
Hospital	0.021/0.226	0.019/0.207	0.009/0.097
Primary school	0.005/0.056	0.005/0.054	0.003/0.036
Secondary school	0.010/0.111	0.009/0.099	0.007/0.076

Table 9. LCC using ΔP lower bound.

Scenario	Minimum[$/ft^2] / [$/m^2]	Mean[$/ft^2] / [$/m^2]	Median[$/ft^2] / [$/m^2]	Maximum[$/ft^2] / [$/m^2]
UVGI without IAQ benefit	−0.18/−1.95	0.15/1.66	0.11/1.22	0.79/8.51
UVGI with IAQ benefit	−3.70/−39.83	−0.37/−4.02	−0.15/−1.62	0.31/3.28
Mechanical cleaning lower bound	−0.22/−2.39	0.10/1.10	0.00/0.00	1.07/11.51
Mechanical cleaning upper bound	0.04/0.41	1.83/19.73	0.51/5.52	10.09/108.51

Note: Positive values indicate a net cost to the owner and negative indicate a net savings.

Table 10. LCC using ΔP upper bound.

Scenario	Minimum[$/ft^2] / [$/m^2]	Mean[$/ft^2] / [$/m^2]	Median[$/ft^2] / [$/m^2]	Maximum[$/ft^2] / [$/m^2]
UVGI w/o IAQ benefit	−4.62/−49.75	−0.84/−9.01	−0.53/−5.69	0.10/1.04
UVGI w/IAQ benefit	−6.20/−66.73	−1.37/−14.69	−0.93/−10.02	0.03/0.33
Mechanical cleaning lower bound	−2.41/−25.95	−0.38/−4.13	−0.18/−1.90	0.60/6.49
Mechanical cleaning upper bound	−1.84/−19.78	1.35/14.50	0.11/1.18	9.68/104.14

Note: Positive values indicate a net cost to the owner and negative indicate a net savings.

Fig. 7. Median LCC all options using ΔP upper bound and ΔP upper bound results. A negative cost indicates a net savings to the owner.

Table 11. Percentage of cases with owner net savings.

Scenario	ΔP Lower bound	ΔP Upper bound
UVGI without IAQ benefit	13.5%	90.1%
UVGI with IAQ benefit	71.2%	99.1%
Mechanical cleaning lower bound	47.7%	88.3%
Mechanical cleaning upper bound	0.0%	42.3%

Fig. A1. LCC of ΔP lower bound using UVGI without taking into account IAQ benefit.

Fig. A2. LCC of ΔP upper bound using UVGI without taking into account IAQ benefit.

Fig. A3. LCC of ΔP lower bound using UVGI while taking into account IAQ benefit.

Fig. A4. LCC of ΔP upper bound using UVGI while taking into account IAQ benefit.

Fig. A5. LCC of ΔP lower bound using the lower bound of mechanical cleaning cost.

Fig. A6. LCC of ΔP upper bound using the lower bound of mechanical cleaning cost.

Fig. A7. LCC of ΔP lower bound using the upper bound of mechanical cleaning cost.

Fig. A8. LCC of ΔP upper bound using the upper bound of mechanical cleaning cost.

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