BLACKSTONE (2006) – Siemens QPA63.x CO2 sensors in Blackstone's conference and meeting rooms vary the ventilation based on occupancy. A motorized damper (VAV box) partially closes the ventilation supply to the room when unoccupied. If the room is occupied, the ventilation runs at 50% of maximum, then activates variable controls up to 100%, but never less than 50%. The other spaces in the building are on a constant volume schedule.

 

 

WYSS HALL (2006) – The Kele Model CD-A carbon dioxide ventilation control and temperature setback was implemented as part of the Automatic Temperature Control Sequence of Operation in all rooms. BLW Engineers calculated an annual energy savings of $1517 from the carbon dioxide controls and $1,149 from the temperature setback, based on a steam cost of $24.68/MMBH and electricity cost of $0.14/kwh (all Y2006 dollars).

 

SCHLESINGER LIBRARY (2006) – Vulcain Infrared CO2 Gas Monitors (90DM3A) - Two carbon dioxide monitors are installed in the HVAC system. One is located in the common return duct, and the other is located in the conference room. The DDC monitors the carbon dioxide levels of both sensors. The DDC system varies the speed of the variable frequency drive of the outside AHU fan, which will modulate the amount of outside air supplied to the building. The monitors include a 5-year warranty.

 

Divinity School Andover Library (upgrade) HDS secured the services of Energy Management Associates, Inc., to evaluate ventilation efficiency in the Andover Hall Library.  The pre-existing system was based on a 13,000 cubic foot per minute air handler that ran 24/7 in a room that is often unoccupied.  A Demand Control Ventilation (DCV) system was installed, including five indoor carbon dioxide sensors and one outdoor sensor.  The new system provides tempered air to meet the occupancy and dilution loads only, saving energy on the unneeded intake of fresh air. The project used a Green Campus Loan fund to cover the total project cost of $8,517. Annual Savings of $3,005, payback of 2.83 years, and a reduction of 18.63 metric tons of carbon dioxide equivalent are predicted.

Carbon dioxide sensors adjust the rate of outside air ventilation based on the carbon dioxide (occupancy) levels in the room.  They can be wall-mounted into recessed conduit boxes.

 

BLACKSTONE (2006) – All of the service water pumps utilize variable frequency drives to control volume flow to chilled water, hot water, and geothermal well water.

 

HOLYOKE CENTER, HRES (2003) (Upgrade) – These VFDs control delivery of chilled water to three separate zones in Holyoke Center. First floor retail, tower, and UHS, pumps are manually operated at constant speed whenever the outside temperature is above 35 degrees. Total project cost (all Y2003 dollars): $31,158, NStar rebate: $15,579, Net project cost and Loan Fund amount: $15,579, Annual Savings: $5,776. The project reduces energy consumption by 65,362 kWh per year.

 

PAYBACK	ENVIRO BENEFIT
3.4 years	Reduction of 48.62 metric tons CO2 equivalent

 

FAS BARKER CENTER GCLF (upgrade) – This project included new AHU exhaust fans with Variable Frequency Drives and associated duct work, new outdoor air intake with modulation damper control, and replacement of AHU 3-way valves with 2-way valves including static pressure sensors for VFD control. Total Project Cost: $92,583, Rebate: $12,000, Annual Savings: $19,875.

 

PAYBACK	ENVIRO BENEFIT
4.7 years	Reduction of 40.27 metric tons CO2 equivalent

 

KSG LITTAUER AND TAUBMAN GCLF (upgrade) - Adjustable speed drives on one 40 HP chilled water pump in Littauer, two 15 HP chilled water pumps in Taubman, on the Littauer 500 ton chiller (with CO2 controls). Total Project Cost:  $163,184, Rebate: $ 37,529, Annual Savings:  $ 35,733.

PAYBACK	ENVIRO BENEFIT
3.5  years	Reduction of 266.7 metric tons CO2 equivalent (with CO2 controls)

 

 

Variable frequency drives, or variable speed drives (VSDs), can greatly increase motor efficiency in a variety of applications. VFDs are electrical devices which adjust the rotational speed of fan and pump motors in response to varying heating and cooling loads, and thus are much more energy-efficient than constant volume systems. VFDs offer direct control over the motor’s electricity input rather than restricting the load itself by using valves and dampers. In some cases, this may eliminate the need for VAV damper adjustments. VFDs provide significant energy savings because horsepower in motors varies as the cube of the torque speed. For example, if fan speed is reduced by 20%, then motor horse-power is reduced by 50%. The best motor candidates for VFDs are large motors with long operating hours. VFD technology has been available for years and has a proven track record of energy savings and reliability.

 

The Advanced Buildings Energy Benchmark, Section 6.6, describes optimal performance criteria for Variable Speed Controls.

 

 

(Variable frequency drive on the 500 ton chiller in Littauer)

HAMILTON HALL (2006) – As part of the Hamilton Hall renovation, the project team took advantage of the Green Campus Loan Fund for New Construction to install dual setback mechanical occupancy sensors in each dorm room that are integrated with the BMS and allow for individual FCU setback. The intent of this procedure is to reduce the mechanical load of the Hamilton dormitory by reducing fan speed and outside air intake. The mechanical setback procedure utilizes occupancy sensors to reduce the heating and cooling demand of the building when specific individual spaces are unoccupied. The heating and cooling demand is reduced by manipulating the setpoint of the individual FCU in each room. Payback analysis was completed by BLW Engineers, Inc. The mechanical setback procedure occurs over two phases:

Phase 1 -15 minutes after space is unoccupied the temperature reverts to setback point I (Control +/- 5 degrees)

Phase 2 - 8 hours after space is unoccupied the temperature reverts back to setback point 2 (Control +/- 10 degrees)

PAYBACK	ENVIRO BENEFIT
$8485 in annual utility savings (Y2006)	7 years