Lesson 8:Introduction to Energy Audit of Educational and Residential Facilities
Try to analyse how energy is used in your facility and think about what you could do to save energy and money. The outcome of this exercise could form the basis for developing energy efficiency project for your facility. In this Lesson we learn about diagnosing energy waste in educational and residential facilities and measures that are needed save energy and money – Energy Audit.
Meaning and purpose of energy audit
Energy audit is similar to medical diagnosis. During medical diagnosis, the doctor physically examines and interviews the patient, checks the temperature and pressure of the patient and may follow up with some laboratory tests, all in an attempt to establish what is wrong with the patient and prescribe appropriate treatment. Similarly, energy audit is employed as a tool for determining what measures can and should be taken to save energy in a facility. Energy audit is the first step in understanding how a facility uses energy and how energy could be saved in the facility. The purpose of the energy audit is to identify, quantify, describe and prioritize cost saving measures relating to energy use in the facility.
Potential Energy Saving Measures
For most facilities, the potential energy saving measures are electric and thermal measures. For residential and educational facilities, thermal measures are of less importance Thermal measures are geared towards reducing the amount of fuel consumed by laundry, kitchen, showers and process heat. However, thermal measures have smaller savings impact on residential and educational facilities. In residential and educational facilities, typical electrical measures include:
- Heating, ventilation and air-conditioning (HVAC) system
- Appliances (Plug loads)
Lighting. Typical lighting efficiency measures include the use of efficient lamps and ballasts, addition of reflectors to enhance lumen output, delamping in over lit spaces, and use of day lighting and day lighting controls.
HVAC System. Typical measures include the replacement of old equipment with new, energy-efficient models, manually turning off appliances when not in and the use, automatic power management devices to control HVAC.
Appliances (Plug loads). The appliances include audio-visuals, personal computers, printers, photocopiers fax machines, etc. Typical energy efficiency measures are similar to HVAC system.
Evaluation of Energy Saving Measures
Any energy saving measure that is recommended for implementation it will guarantee sufficient energy savings to pay for the implementation cost within a reasonable period of time. Therefore, energy saving measures must be subjected to some form of evaluation in the form of economic analysis. The economic analysis is usually based on simple payback calculations that take into consideration the cost of implementing the energy saving measure (ESM) and the cost savings resulting from the implementation of the ESM.
Generally, the payback period is the length of time required for the returns on an investment to exceed the investment cost. The basic idea is that the shorter the payback period the more attractive the investment (Eastop &Croft, 1990). The simple payback period (in years) is determined by dividing the investment cost by the annual returns on the investment. In the context of our energy audit, the implementation cost represents the investment cost and the energy cost savings represents the returns on investment. Thus, Simple Payback period (in months) = Implementation Cost/ Monthly Cost Savings or the Simple Payback Period (in years) = Implementation Cost/ Annual Cost Savings.
Three 100W incandescent lamps are used for exterior lighting and it being recommended that we replace with either three 20W compact fluorescent lamps or two 20W fluorescent lamps. Determine the payback period for each of the two recommendations using the information below.
|Item||Unit Cost (¢)|
|20W compact fluorescent lamp||22,000|
|20W fluorescent lamp||5,000|
|20W fluorescent lamp fixture||25,000|
|Installation cost of 20W fluorescent lamp fixture||5,000|
Daily operating hours of existing lamps = 10 hours
Daily energy consumption lamps = [math]PxTxN/1000[/math], kWh
P = Power rating of lamp in watts
T = Time in hours per day lamp is in use
N = Number of lamps in use
Daily energy consumption of 100W incandescent lamps, E1 =100x10x3/1000 = 3 kWh
Daily energy consumption of 20W CFLs, E2 =20x10x3/1000 = 0.6 kWh
Daily energy consumption of 20W fluorescent lamps, E3 = 20x10x2/1000 = 0.4 kWh
Daily Energy Savings by CFLs = E1 - E2 = 3 – 0.6 = 2.4 kWh
Daily energy savings 20W fluorescent lamps = E1 - E3 = 3 – 0.4 =2.6 kWh
Monthly energy savings = Daily energy savings x 30 days
(An average of 30 days in a month is assumed)
Monthly energy savings by CFLs = 2.4 kWh/day x 30 days = 72 kWh
Monthly energy savings by fluorescent lamps = 2.6 kWh/day x 30 days = 78 kWh
Monthly energy cost savings = Monthly energy savings x energy cost
Monthly energy cost savings by CFLs = 72 kW x ¢ 580/kWh =¢ 41,760
Monthly energy cost savings by fluorescent lamps = 78 kWh x ¢ 580/kWh = ¢ 45,240
Implementation cost for CFLs = 3 x Unit Cost of CFL = 3 x ¢ 22,000 = ¢ 66,000
Implementation cost for fluorescent lamps
=cost of fixtures + cost of two lamps + installation cost of two lamps = 2x25,000 + 2x5,000 + 2x5,000 = ¢ 70,000
Payback period for CFLs = Implementation cost ÷ Monthly energy cost saving = ¢ 66,000/¢ 41,760 per month = 1.58 months ≈ 2 months
Payback period for fluorescent lamps = Implementation cost ÷ Monthly energy cost saving =¢ 70,000/¢ 45,240 per month = 1.55 months ≈ 2 months
Thus, the payback period for each recommendation is roughly 2 months, following which the savings in energy cost appear as profit for the life of the installation.
Energy Audit Report
The energy audit report may have the following parts.
- Title Page
- Table of Contents
- Executive Summary
- Identified Energy Saving Measures
- Description of Existing Situation
- Economic Analysis
- Appendix (if any)
The characteristics of a good energy audit report are as follows.
- Must be easily read and digested by both technical and non-technical audiences.
- Include charts and graphs to display information graphically whenever possible
- Always display units and make calculations clear.
- State and explain any assumptions made.
- Make recommendations clear and support them with as much quantitative details as possible.