Are they Cost-Effective? Brad Pittler & Patrick Sims Energy Saving Devices Are they Cost-Effective? Brad Pittler & Patrick Sims

The Customer Southern Methodist University Michael Vangelli University with roughly 10,000 students Michael Vangelli Campus Planning and Plant Operations Electrical Engineer

Issues to be Resolved Collect data regarding study room, rest room, and copy room usage. Gather information regarding energy efficient devices Compare installation costs of energy saving devices to what they would save over a period of time

Method of Data Collection Automatic Using “Intellitimer” Device Using Circulation records from libraries Using sign-out sheets Manual Counting people entering and exiting rooms Using anecdotal evidence when available

Data Analysis Objective To gather sufficient data to: Develop a mean for each type of room Develop a picture for room usage over a period of time Develop a representative basis for recommendation

Problem Development Data collected formed a cost/benefit problem (with the following assumptions): The data collected was representative of the norm The costs would be static, and labor would be ignored Inconvenience of installation had no cost

Model Development Goals were to calculate energy-cost savings for two different types of energy saving devices. Calculating the time until the device pays for itself in energy savings Implemented into the model three factors: Data Gathered on Occupancy Cost of Energy per kWh Average Energy used per room (in kWh.)

The Model Annual Savings Model (Percent of time unoccupied) X (Cost of energy) X (Energy used per room) X (16 hours) X (350 days) This will calculate total energy savings.

The Model (Cont.) The Payback Period T = Unit Cost / Annual Savings This will calculate how long the unit will take to “pay for itself” via energy savings.

Choosing the Devices Gather information on options used for energy savings Contact other organizations to learn about their choices Learn about drawbacks and costs to install the devices

The Contenders Leviton develops devices that use both IR and Ultrasonic to detect occupancy WattStopper offers devices using either IR or Ultrasonic to detect occupancy

Drawbacks and Positives Criteria Leviton WattStopper Cost X Ease of Procurement Ease of Installation

Based on pattern (~16 minutes) The Contenders (Cont.) Device Install Time Unoccupied time Cost (List Price) Leviton Model 1000WAH 60 minutes Based on pattern (~16 minutes) $113.80 WattStopper WT-605 (for restrooms) 16 minutes $134.00 WattStopper WA-100-120 (for copy rooms) 30 minutes 18 minutes $72.00 WattStopper WPIR 15 minutes $102.00

Numerical Findings Cost of Solution Energy Savings Time to Payback (years) Study Rooms $134 (WS) $113.80 (Lev) $75.42 1.35 (WS) 1.51 (Lev) Restrooms $102 (WS) $49.67 2.7 (WS) 2.29 (Lev) Copy Rooms $72 (WS) $59.59 1.21 (WS) 1.91 (Lev)

Conclusions In two of the three cases, installation of either device would have a payback period of less than two years. Both devices had positive and negative points. The decision would be made on choice between cost and convenience. Further study of room usage patterns could contribute to better choices.