30079_51.pdf

CHAPTER 51

ENERGY AUDITING

Carl Blumstein

Universitywide Energy Research Group

University of California

Berkeley, California

Peter Kuhn

Kuhn and Kuhn,

Industrial Energy Consultants

Golden Gate Energy Center

Sausalito, California

51.1 ENERGY MANAGEMENT

AND THE ENERGY AUDIT 1591

51.3.1 Low-Cost Conservation 1598

51.3.2 Capital-intensive Energy

Conservation Measures 1600

51.2 PERFORMING AN ENERGY

AUDIT— ANALYZING

ENERGY USE

51.4 EVALUATING ENERGY

CONSERVATION

OPPORTUNITIES

1 592

16 02

51.3 PERFORMING AN ENERGY

AUDIT— IDENTIFYING

OPPORTUNITIES FOR

SAVING ENERGY

51.5 PRESENTING THE RESULTS

OF AN ENERGY AUDIT 16 04

15 97

51.1 ENERGY MANAGEMENT AND THE ENERGY AUDIT

Energy auditing is the practice of surveying a facility to identify opportunities for increasing the

efficiency of energy use. A facility may be a residence, a commercial building, an industrial plant,

or other installation where energy is consumed for any purpose. Energy management is the practice

of organizing financial and technical resources and personnel to increase the efficiency with which

energy is used in a facility. Energy management typically involves the keeping of records on energy

consumption and equipment performance, optimization of operating practices, regular adjustment of

equipment, and replacement or modification of inefficient equipment and systems.

Energy auditing is a part of an energy management program. The auditor, usually someone not

regularly associated with the facility, reviews operating practices and evaluates energy using equip-

ment in the facility in order to develop recommendations for improvement. An energy audit can be,

and often is, undertaken when no formal energy management program exists. In simple facilities,

particularly residences, a formal program is impractical and informal procedures are sufficient to alter

operating practices and make simple improvements such as the addition of insulation. In more com-

plex facilities, the absence of a formal energy management program is usually a serious deficiency.

In such cases a major recommendation of the energy audit will be to establish an energy management

program.

There can be great variation in the degree of thoroughness with which an audit is conducted, but

the basic procedure is universal. The first step is to collect data with which to determine the facility's

major energy uses. These data always include utility bills, nameplate data from the largest energy-

using equipment, and operating schedules. The auditor then makes a survey of the facility. Based on

the results of this survey, he or she chooses a set of energy conservation measures that could be

applied in the facility and estimates their installed cost and the net annual savings that they would

Mechanical Engineers' Handbook, 2nd ed., Edited by Myer Kutz.

provide. Finally, the auditor presents his or her results to the facility's management or operators. The

audit process can be as simple as a walkthrough visit followed by a verbal report or as complex as

a complete analysis of all of a facility's energy using equipment that is documented by a lengthy

written report.

The success of an energy audit is ultimately judged by the resulting net financial return (value of

energy saved less costs of energy saving measures). Since the auditor is rarely in a position to exercise

direct control over operating and maintenance practices or investment decisions, his or her work can

come to naught because of the actions or inaction of others. Often the auditor's skills in communi-

cation and interpersonal relations are as critical to obtaining a successful outcome from an energy

audit as his or her engineering skills. The auditor should stress from the outset of his or her work

that energy management requires a sustained effort and that in complex facilities a formal energy

management program is usually needed to obtain the best results. Most of the auditor's visits to a

facility will be spent in the company of maintenance personnel. These personnel are usually consci-

entious and can frequently provide much useful information about the workings of a facility. They

will also be critical to the success of energy conservation measures that involve changes in operating

and maintenance practices. The auditor should treat maintenance personnel with respect and consid-

eration and should avoid the appearance of "knowing it all." The auditor must also often deal with

nontechnical managers. These managers are frequently involved in the decision to establish a formal

energy management program and in the allocation of capital for energy saving investments. The

auditor should make an effort to provide clear explanations of his or her work and recommendations

to nontechnical managers and should be careful to avoid the use of engineering jargon when com-

municating with them.

While the success of an energy audit may depend in some measure on factors outside the auditor's

control, a good audit can lead to significant energy savings. Table 51.1 shows the percentage of

energy saved as a result of implementing energy audit recommendations in 172 nonresidential build-

ings. The average savings is more than 20%. The results are especially impressive in light of the fact

that most of the energy-saving measures undertaken in these buildings were relatively inexpensive.

The median value for the payback on energy-saving investments was in the 1-2 year range (i.e., the

value of the energy savings exceeded the costs in 1-2 years). An auditor can feel confident in stating

that an energy saving of 20% or more is usually possible in facilities where systematic efforts to

conserve energy have not been undertaken.

51.2 PERFORMING AN ENERGY AUDIT—ANALYZING ENERGY USE

A systematic approach to energy auditing requires that an analysis of existing energy-using systems

and operating practices be undertaken before efforts are made to identify opportunities for saving

energy. In practice, the auditor may shift back and forth from the analysis of existing energy-use

patterns to the identification of energy-saving opportunities several times in the course of an

audit—first doing the most simple analysis and identifying the most obvious energy-saving oppor-

tunities, then performing more complex analyses, and so on. This strategy may be particularly useful

if the audit is to be conducted over a period of time that is long enough for some of the early audit

recommendations to be implemented. The resultant savings can greatly increase the auditor's credi-

Table 51.1 The Percentage of Energy Saved as a Result of Implementing

Energy Audit Recommendations in 172 Nonresidential Buildings 3 ' 4

Source

Savings Sample

(%) Size

21 72

28 37

21 24

17 10

23 18

24 4

5 4

30 1

11 1

43 1

"Electricity is counted at 3413 Btu/kWhr for site energy and 11,500 Btu/kWhr

for source energy (i.e., including generation and transmission losses).

Site

Savings

Sample

Building Category

Elementary school

Secondary school

Large office

Hospital

Community center

Hotel

Corrections

Small office

Shopping center

Multifamily apartment

(%)

Size

bility with the facility's operators and management, so that he or she will receive more assistance in

completing his or her work and his or her later recommendations will be attended to more carefully.

The amount of time devoted to analyzing energy use will vary, but, even in a walkthrough audit,

the auditor will want to examine records of past energy consumption. These records can be used to

compare the performance of a facility with the performance of similar facilities. Examination of the

seasonal variation in energy consumption can give an indication of the fractions of a facility's use

that are due to space heating and cooling. Records of energy consumption are also useful in deter-

mining the efficacy of past efforts to conserve energy.

In a surprising number of facilities the records of energy consumption are incomplete. Often

records will be maintained on the costs of energy consumed but not on the quantities. In periods of

rapidly escalating prices, it is difficult to evaluate energy performance with such records. Before

visiting a facility to make an audit, the auditor should ask that complete records be assembled and,

if the records are not on hand, suggest that they be obtained from the facility's suppliers. Good record

keeping is an essential part of an energy management program. The records are especially important

if changes in operation and maintenance are to be made, since these changes are easily reversed and

often require careful monitoring to prevent backsliding.

In analyzing the energy use of a facility, the auditor will want to focus his or her attention on

the systems that use the most energy. In industrial facilities these will typically involve production

processes such as drying, distillation, or forging. Performing a good audit in an industrial facility

requires considerable knowledge about the processes being used. Although some general principles

apply across plant types, industrial energy auditing is generally quite specialized. Residential energy

auditing is at the other extreme of specialization. Because a single residence uses relatively little

energy, highly standardized auditing procedures must be used to keep the cost of performing an audit

below the value of potential energy savings. Standardized procedures make it possible for audits to

be performed quickly by technicians with relatively limited training.

Commercial buildings lie between these extremes of specialization. The term "commercial build-

ing" as used here refers to those nonresidential buildings that are not used for the production of

goods and includes office buildings, schools, hospitals, and retail stores. The largest energy-using

systems in commercial buildings are usually lighting and HVAC (heating, ventilating, and air con-

ditioning). Refrigeration consumes a large share of the energy used in some facilities (e.g., food

stores) and other loads may be important in particular cases (e.g., research equipment in laboratory

buildings). Table 51.2 shows the results of a calculation of the amount of energy consumed in a

relatively energy-efficient office building for lighting and HVAC in different climates. Office buildings

(and other commercial buildings) are quite variable in their design and use. So, while the proportions

of energy devoted to various uses shown in Table 51.2 are not unusual, it would be unwise to treat

them (or any other proportions) as "typical." Because of the variety and complexity of energy-using

systems in commercial buildings and because commercial buildings frequently use quite substantial

amounts of energy in their operation, an energy audit in a commercial building often warrants the

effort of a highly trained professional. In the remainder of this section commercial buildings will be

used to illustrate energy auditing practice.

Lighting systems are often a good starting point for an analysis of energy in commercial buildings.

They are the most obvious energy consumers, are usually easily accessible, and can provide good

opportunities for energy saving. As a first step the auditor should determine the hours of operation

of the lighting systems and the watts per square foot of floorspace that they use. These data, together

with the building area, are sufficient to compute the energy consumption for lighting and can be used

to compare the building's systems with efficient lighting practice. Next, lighting system maintenance

practices should be examined. As shown in Fig. 51.1, the accumulation of dirt on lighting fixtures

can significantly reduce light output. Fixtures should be examined for cleanliness and the auditor

should determine whether or not a regular cleaning schedule is maintained. As lamps near the end

of their rated life, they lose efficiency. Efficiency can be maintained by replacing lamps in groups

Table 51.2 Results of a Calculation of the Amount of Energy Consumed in

a Relatively Energy-Efficient Office Building for Lighting and HVAC 5

Energy Use (kBtu/ft 2 /yr)

Miami

Los Angeles

Washington

Chicago

Lights

34.0

HVAC auxiliaries

8.5

7.7

8.8

Cooling

24.4

9.3

10.2

7.6

Heating

0.2

2.9

17.7

28.4

Total

67.1

53.9

70.7

78.8

Fig. 51.1 Reduction in light output from fluorescent fixtures as a function of fixture cleaning

frequency and the cleanliness of the fixture's surroundings. 3

before they reach the end of their rated life. This practice also reduces the higher maintenance costs

associated with spot relamping. Fixtures should be checked for lamps that are burned out or show

signs of excessive wear, and the auditor should determine whether or not a group-relamping program

is in effect.

After investigating lighting operation and maintenance practices, the auditor should measure the

levels of illumination being provided by the lighting systems. These measurements can be made with

a relatively inexpensive photometer. Table 51.3 gives recommended levels of illumination for a variety

of activities. A level much in excess of these guidelines usually indicates an opportunity for saving

energy. However, the auditor should recognize that good seeing also depends on other factors such

as glare and contrast and that the esthetic aspects of lighting systems (i.e., their appearance and the

Table 51.3 Range of Illuminances Appropriate for Various Types of Activities and

Weighting Factors for Choosing the Footcandle Level* within a Range of Illuminance 6

Range of Illuminances

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: