Innovations in Comfort, Efficiency, and Safety Solutions.
Ambient Light Energy Harvesting CO2, Temperature and Humidity Sensor
| Mike Schell,
VP Marketing & Business Development
AirTest Technologies Inc.
J G O’Donoghue
Building in Edmonton is an
enormous, three-story, 262,500 square foot office building operated by
the Province of Alberta. A $32 m retrofit project of the building was
completed in 2018 to meet the Alberta Go-Green program that
incentivizes buildings to rely on renewable energy. The project was a
full renovation that included the addition of solar power, tenant
improvements and installation of new HVAC, electrical and plumbing
systems to meet sustainability objectives.
Included as part of the retrofit was the installation of 117 AirTest TR9277-EO wireless, zero energy, CO2, temperature and humidity transmitters that are powered solely by an onboard photovoltaic panel that harvests indoor ambient light. If desired, a button battery can also be used to provide 5 years of power. These devices were installed in all meeting rooms in the building and are used to provide energy efficient Demand Controlled Ventilation (DCV) that allows the modulation of delivery of fresh outside air to the space based on the number of people in the space exhaling CO2.
DCV is widely recognized as a method of reducing
energy costs while ensuring good indoor air quality and is a regular
part of energy efficiency building upgrades. It is often also required
by code in new construction. Wireless technology is often preferred in
retrofit applications like this to avoid the cost of running wires.
The building control system selected for the project is made by Delta Controls and installed by ESC Automation in Edmonton. A key component offered as part of the Delta system is an inexpensive, add-on wireless gateway called the CON-ENOC which supports a wide range of devices that communicates using the low-energy, EnOcean® wireless protocol, including the AirTest TR9277-EO. The gateway can receive signals from up to 32 actual EnOcean® communicating devices which then translates the information via an RS485 connection to the widely used BACnet™ wired communication protocol. Many other HVAC manufactures offer similar EnOcean® gateways.
MacPherson, a Controls Technician at
ESC, was responsible for the CO2 installation. According to Shane, “
This was the first installation our branch has undertaken using this
AirTest TR9277-EO wireless transmitter, and I was unsure how difficult
this would be. Thankfully, the sensors were fast and easy to install
and when it was all was completed, I looked like a hero!”
feature of the TR9277-EO is a test mode that allows for measurement of
radio signal strength between the gateway and transmitter. In this
installation, there were a number of metal interior walls in the
building that potentially can be a barrier for radio communication. To
meet this challenge, Shane strategically placed the CON-ENOC gateways
within 15 meters (50 feet) of the EnOcean® devices in such a way that
the radio signal did not have to go through more than two walls. The
radio strength test onboard the TR9277-EO then allowed for quick
verification and ideal placement in this challenging situation. This
test also helped quickly identify that one gateway was not operating
properly and had to be changed out. The transmitter also has a light
level test that can be used to determine the best location for indoor
harvesting light for power.
Even though the TR9277-EO measures
temperature and humidity, the temperature measurement and control for
the building were performed by another brand of wireless temperature
sensor that had a display and manual temperature adjust features as
required in the building specifications. AirTest does offer an
adjustable temperature transmitter as well as the three parameter
TR9277-EO transmitter, but the low energy budget of these ambient
light-harvesting devices does not support active displays at this time.
all sensors were installed, Shane relied on the “Automated
Background Calibration” (ABC) self-calibration feature of the
transmitter that will calibrate the sensor to outside air over about a
week of operation. This method assumes that inside levels are equal to
outside levels (e.g., 400 ppm) once the building has been unoccupied
for a few hours. The TR9277-EO CO2 sensor also has an onboard pressure
sensor to correct CO2 readings for altitude that further increases
reading accuracy. If desired, the sensor can also be calibrated in
outdoor air before final installation.
there is not a display on
the TR9277-EO, three LEDs on the right side of the photovoltaic panel
will flash every 15 seconds to indicate good, marginal, or poor air
quality levels based on CO2. A more exact output of the current
measurement can be shown in LED flash sequence by activating the
function using the side button.
TR9277-EO offered a simple,
fast and reliable way of integrating CO2, temperature and humidity
measurement into the Delta Controls system using their CON-ENOC,
EnOcean®-to-BACnet™ gateway. This approach reduces total cost of
installation in new and retrofit applications by drastically reducing
wiring and labor costs. In spaces with high or variable occupancy, CO2
DCV can start saving energy immediately. Many utilities also offer
rebates for CO2 DCV installations.
ESC Automation, 18222
102 Ave, Edmonton AB T5S-1S7, 780 722-0753, www.escautomation.com
AirTest webpage for the TR9277-EO CO2, Temp and RH transmitter and
other EnOcean® products, with data sheets and additional info:
• Datasheet for the Delta Controls, CON-ENOC,
P: 604 517-3888, TF:
888-855-8880, F: 604 517-3900 • The EnOcean® Alliance, “No Wires. No
Batteries. No Limits.” : www.enocean-alliance.org AirTest TR9277-EO
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