Distributed Renewable Energy Operating Impacts and Valuation Study

Section 2
Daylighting Costs
Capital Costs
Active systems are the least expensive on a per-kWh-saved basis, at an average of $0.54 per
kWh saved. The higher costs of the fittings for active systems are offset by the additional
operating hours. Passive systems are slightly more expensive at an average of $0.81 per first-year
kWh saved. Hybrid systems (involving both daylighting and electric illumination) are
significantly more expensive, at an average of $4.30 per first-year kWh saved; however, this
includes the cost of a specific type of light fixture. Hybrid systems have the benefit of being
fully automated and compact, with all the controls, daylighting, and artificial lighting in one unit.
Table 2-7 shows typical costs per fitting for hybrid, active, and passive systems.
Table 2-7
Costs per Fitting and per kWh Saved for Daylighting
Project Description
Type of
System
Cost per Fitting
Energy Savings per
Fitting (kWh)
Cost of Energy
Savings ($/first-year
kWh)
Big Box Retail – Active Active $2,150 3,654 $0.59
PSI Active $1,305 2,694 $0.48
High School Gym Hybrid $3,150 757 $4.16
ADOT Maintenance Facility Hybrid $3,285 742 $4.43
Industrial Plant Passive $690 2,224 $0.31
Warehouse 1 Passive $1,150 2,220 $0.52
Big Box Retail – Passive Passive $2,700 1,379 $1.96
National Guard Hangar Passive $1,200 1,462 $0.82
Warehouse 2 Passive $1,500 1,818 $0.82
Marine Air Station Hangar Passive $1,300 2,869 $0.45
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Source: Data provided by Natural Lighting Company Inc., Glendale AZ
2.4.2 Model Descriptions
Performance Modeling
Simulation Modeling Programs
The eQuest model was used to simulate the hourly effects of daylighting systems. This model is
an enhanced version of the DOE-2 building simulation model, which is a widely used and
accepted industry standard. The model allows daylighting to be easily added to a building model,
and it outputs hourly load shapes for end use categories such as lighting and HVAC. The eQuest
model has a specialist module for daylighting that includes the ability to specify controls and
control strategies, light wells, skylights, and diffusion lenses.
2-26 R. W. Beck, Inc. Arizona Public Service