Energy Savings Study for Daylighting Application
Spanish Springs Middle School
Quality Control Systems
Sparks, Nevada
April 2005
An energy savings study for a daylighting application at
Spanish Springs Middle School (Washoe County,
Nevada) was performed in 2004 in order to apply
for a NevadaSureBet customer rebate. NevadaSureBet
is a program sponsored by Nevada Power and Sierra
Pacific Power and administered by KEMA. This program
provided a cash rebate to the school upon evidence of
energy demand and consumption savings obtained by
installing the daylighting system throughout the school.
The system was designed and Manufactured by
Natural Lighting Co., Inc. of Glendale, Arizona.
Daylighting is a state-of-the art technology using dome
lenses and diffusers to transmit direct and ambient
sunlight through a reflective light shaft to evenly illuminate
an interior space. T-5 lamps are integrated into the
daylighting modules to provide additional staged
lighting when ambient natural lighting is insufficient
or unavailable.
The daylighting retrofit at Spanish Springs consisted of
removing 92 original fixtures (24 x 400W HID,
6 x 500W HID, 15 x 110W F032T8, 47 x 70W 2x2
fixtures) and replacing them with 67 daylighting units
(30 tracking 4x4 fixtures and 37 passive 4x4 fixtures
with 381W T-5’s). This allowed sunlight to illuminate
the gym, library and other areas during daylight hours,
thus saving energy. Furthermore, integrated staged
lighting was connected to a control system that sensed
lighting levels and occupancy to determine if and how
much additional electric lighting was needed to
maintain comfortable light levels.
The energy savings calculations consisted of a
comparison of the estimated annual energy use of the
old fixtures versus the energy use of the new daylighting
systems. The energy use depends on the amount
of daylight available during normal hours of use of the
facility. In the Spanish Springs study, we assumed 20
days a month of use with an average of 12 hours a day
(nominally from 7 AM to 7 PM). This provided a total
of 2,880 hours per year. The amount of usable daylight
was based on the hours per day - from 1 hour after sunrise
to 1 hour before sunset - that fell within the nominal usage
window. The calculation was based on astronomical
data for the year and yielded a total usable daylighting
availability of 83% (or 97% during the peak demand times
of June-Sept) (1,2)
Additionally, historical weather data was gathered
for the region, to include climatic conditions – such
as the number of cloudy and clear days – in the
daylight availability calculation. The Spanish Springs
area receives sunny or partly cloudy days 68% of the
time during the 83% daylight period, for a total of
57% sunlight availability (3). This means that for
57% of the school’s operational time, daylighting
is sufficient to provide all the lighting needs and
electrical lighting is not required. Of the remaining
43% of the time, it is assumed that half of this time
will require half the staged lights to be turned on,
and the other half of the time all the lights will need
to be turned on. Additionally, accommodation is
made for the occupancy sensors. Based on numerous
studies, it is conservatively estimated that the school
will save 40% from the use of occupancy sensors (4).
The end result for Spanish Springs is that an annual
consumption savings benefit of 33,092 KWH or
66% is obtained from the daylighting application.
This figure was accepted by KEMA in the
NevadaSureBet application and was used to
calculate the school’s subsequent rebate.
As an experiment, the data was re-calculated
assuming that the Spanish Springs Middle School
was located in Las Vegas. The type and extent
of the retrofit was kept exactly the same – only
the weather and astronomical data was adjusted
for Southern Nevada to take into account the
greater number of sunny days predominant in
Las Vegas. The result was an annual consumption
savings of 37,172 KWH or 74% (for a savings
total that was 4,000 KWH or 8% better than Reno’s).
References Page:
Astronomical data:
For Reno, NV and Las Vegas, NV.
Astronomical Applications Dept.
Rise and Set for the Sun for 2004 and 2005.
(2) Power Company:
Average Peak Demand defined as June-Sept
inclusive 1-7 PM (as per Kema, based on Power
Company policy for the rebate program).
www.sierrapacific.com
www.nevadapower.com
www.nevadasurebet.com/ProjectCenter/
(3) Weather data:
Historical weather data for Reno and Las Vegas, from
Western Regional Climate Center.
Data is based on daylight hours only. A clear day denotes zero
to 3/10 average, sky cover. Partly cloudy is 4/10 to 7/10 tenths.
Cloudy is 8/10 to 10/10 tenths.
www.wrcc.dri.edu/htmlfiles/westcomp.ovc.html
www.wrcc.dri.edu/htmlfiles/westcomp.clr.html
(4) Lighting, occupancy sensors, etc.:
From FPL study, classroom energy savings
of 40 to 46% due to occupancy sensors.
Occupancy sensors can reduce energy waste
by as much as 68% and increasing energy savings
by as much as 60%, according to a new study
conducted by the Environmental Protection Agency (EPA)
Nema study (2001): Occupancy sensors in classroom
application, energy savings of 52% using a 20 minute
time delay period.
http://www.nema.pdf
http://www.savingenergy.asp
http://designguide.htm
http://www.epastudy.html
(5) Daylighting Applications:
Daylighting is a state-of-the art technology using dome lenses and diffusers
to transmit direct and ambient sunlight through a reflective light shaft to
evenly illuminate an interior space. Daylighting provides indoor full-spectrum, natural daylight which:
http://www.daylighting.com/
http://windows.lbl.gov/
http://www.daylighting_initiative.html
 |