Energy Saving Devices

1
Energy Saving Devices

• Are they Cost-Effective?
• Brad Pittler Patrick Sims

2
The Customer

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

3
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

4
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

5
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

6
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

7
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.)

8
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.

9
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.

10
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

11
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

12
Drawbacks and Positives
Criteria Leviton WattStopper
Cost X
Ease of Procurement X X
Ease of Installation X
13
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) 60 minutes 16 minutes 134.00
WattStopper WA-100-120 (for copy rooms) 30 minutes 18 minutes 72.00
WattStopper WPIR 60 minutes 15 minutes 102.00
14
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) 113.80 (Lev) 49.67 2.7 (WS) 2.29 (Lev)
Copy Rooms 72 (WS) 113.80 (Lev) 59.59 1.21 (WS) 1.91 (Lev)
15
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.