2.3. Instrumentation
Various research-grade sensors were used to measure indoor
and outdoor air temperatures, outdoor air relative humidity, roof
surface temperatures, heat fluxes through the roof deck, solar
radiation, wind speed, HVAC power demand and building power
demand. Table A1 in the electronic supplementary material summarizes
the measurement locations and sensor types.
Outside air temperature and relative humidity (RH) were measured
using a Vaisala HMP45C-L probe, which was housed in
a Campbell Scientific 10-plate naturally ventilated Gill radiation
shield (model 41003-5). The shield was located about 70 cm above
the roof on a weather tower mounted on the building near its southwest
corner. Global horizontal solar radiation was measured using
a Kipp & Zonen CMP3 second-class pyranometer. The device was
attached to a Campbell Scientific leveling mount, which was in turn
affixed to the south end of the weather tower cross-arm. The instrument
was located higher than all nearby obstacles (including a
nearby chimney) to avoid shadows. Wind speed was measured with
a Gill Instruments WindSonic two-axis time-of-flight ultrasonic
anemometer. The device was attached to the top of the weather
tower, about 2 m above the roof. Measurements of precipitation at
Yuma Marine Corps Air Station, AZ were obtained from Weather
Underground [23].
Three roof temperatures were measured in each roof quadrant
(for a total of 12 roof temperature measurements) using
Minco S667PD thin-film platinum resistance temperature sensors
connected to Minco Temptran TT176PD temperature transmitters
(Fig. 2). Before installation of the BIPV system four roof top surface
temperature sensors were installed (Fig. 2). Each of these temperature
sensors was attached to the roof using construction adhesive
and then covered with an approximately 150 mm-square piece of
asphalt cap sheet patch. The patch was adhesively bonded to the
existing roof cap sheet. Four temperatures were also measured on
the wooden underside of the roof deck beneath the roof top surface
temperature sensors (Fig. 2). Each temperature sensor was
bonded to the wood with epoxy. During the subsequent installation
of the BIPV system, four additional temperature sensors were
added. These sensors were located on the top surface of the BIPV
system roof board (Fig. 1). The temperature sensor in the northwest
quadrant was underneath the exposed white membrane (without
laminated PV) while the other three sensors were underneath the
membrane with laminated PV (Fig. 2).
Heat fluxes were measured at the underside of the roof deck
in each roof quadrant using Hukseflux HFP01-L heat flux sensors.
Each heat flux sensor was attached to the underside of the roof
deck near roof underside temperature sensors using epoxy and oriented
for positive heat flux downward through the sensor. During
installation of the BIPV system, two additional Hukseflux HFP01-L