CHAPTER 4. SCREENING ANALYSIS

TABLE OF CONTENTS

4.1 INTRODUCTION

................................ ................................ ................................ ........... 4

- 1

4.2 SCREENED

- OUT TECHNOLOGIES

................................ ................................ ............ 4

- 2

4.2.1 Burner Derating

................................ ................................ ................................ ............... 4

- 2

4.3 TECHNOLOGIES THAT HA VE NEGLIGIBLE OR NO IMPACT ON

THERMAL OR COMBUST ION EFFICIENCY AS ME ASURED BY THE

DEPARTMENT OF ENERGY TEST PROCEDURE

................................ .................... 4

- 3

4.3.1 Combustion Preheaters

................................ ................................ ................................ .... 4

- 3

4.3.2 Economizers

................................ ................................ ................................ ..................... 4

- 3

4.3.3 Blow

- down Waste Heat Recovery

................................ ................................ ................... 4

- 4

4.3.4 Jacket Insulation Optimization

................................ ................................ ........................ 4

- 4

4.4 TECHNOLOGY OPTIONS F OUND IN BASELINE UNI TS

................................ ....... 4

- 4

4.5 REMAINING TECHNOLOGY OPTIONS

................................ ................................ .... 4

- 5

LIST OF TABLES Table 4.4.1 Technologies Found in Common Baseline Boiler Designs

................................ ...... 4

- 5 Table 4.5.1 Design Options for Commercial Packaged Boilers Analyzed in the Engineering Analysis

................................ ................................ ................................ ....... 4

- 5

4

- iCHAPTER 4. SCREENING ANALYSIS

4.1 INTRODUCTION

This chapter discusses the screening analysis conducted by the U.S. Department of Energy (DOE) of the technology options identified in the market and technology assessment for commercial packaged boilers (CPBs). In chapter 3, the market and technology assessment DOE presented an initial list of technology options that can be used to improve the energy effi ciency

of CPB . The goal of the screening analysis is to identify any technology o ptions that will be eliminated from further consideration in the rulemaking analyses.

The candidate technology options are assessed based on DOE analysis as well as inputs

from interested parties including manufacturers, trade organizations, and energy efficiency advocates. Technology options which are judged to be viable approaches for improving energy efficiency are retained as inputs to the subsequent engineering analysis . Technology options which are not incorpor ated in commercial equipment or in working prototypes, or that fail to

meet certain criteria as to practicability to manufacture, install and service, as to impacts on equipment utility or availability, or as to h ealth or safety will be eliminated from consideration in

accordance with subpart C of Title 10 of the Code of Federal Regulations, Part 430 ( 10 CFR Part 430, subpart C )

, under appendix A, section 4(a)(4)(i

‒ iv). Some of the technologies identified during th e technology assessment can improve the overall efficiency of a CPB but may not improve the thermal and/or combustion efficiency of a CPB, as measured by the test procedure prescribed under 10 CFR 431.86. Such technologies are not passed on to the enginee ring analysis for consideration because they would not be implemented as a result of more stringent energy conservation standards.

The technologies identified in the market and technology assessment were evaluated pursuant to the criteria set out in t he Energy Policy and Conservation Act, as amended (EPCA or the Act). (42 U.S.C. 6291

- 6317) EPCA provides criteria for prescribing new or amended standards, which will achieve the maximum improvement in energy efficiency the Secretary of Energy determines t o be technologically feasible. (42 U.S.C. 6313(a)(6)(A)(ii)(II) ) It also establishes guidelines for determining whether a standard is economically justified. ( 42 U.S.C. 6313(a)(6)(B)(ii) ) In view of the EPCA requirements for determining whether a standard is technologically feasible and economically justified, a ppendix A to subpart C of 10 CFR Part 430, Procedures, Interpretations and Policies for Consideration of New or Revised Energy Conservation Standards for Consumer Products

, section 5., Policies on Selection of Standards

, sets forth procedures to guide DOE in the consideration and promulgation of new or revised

residential product and commercial and industrial equipment efficiency standards under EPCA. These procedures elaborate on the statutory crit eria provided in EPCA and

, in part

, eliminate problematic technologies early in the process of revising an energy efficiency standard. Under the guidelines, DOE eliminates from consideration technologies that present unacceptable problems with respect to t he following four factors:

4-11. Technological feasibility

. DOE will consider technologies incorporated in commercial products or in working prototypes to be technologically feasible.

2. Practicability to manufacture, install, and service

. If mass produ ction and reliable installation and servicing of a technology in commercial products could be achieved on the scale necessary to serve the relevant market at the time the standard comes into effect, then DOE will consider that technology practicable to manufacture, install, and service.

3

. Adverse impacts on product utility or equipmen t availability

. If DOE determines a technology would have a significant adverse impact on the utility of the product to significant subgroups of c onsumers , or would re sult in the unavailability of any covered product type with performance characteristics (including reliability), features, sizes, capacities, and volumes that are substantially the same as products generally available in the United States at the time, i t will not consider this technology further.

4. Adverse impacts on health or safety

. If DOE determines that a technology will have significant adverse impacts on health or safety, it will not consider this technology

further.

In summary, if DOE determines that a technology, or a combination of technologies, has unacceptable impacts based on the factors identified in 10 CFR 430, subpart C, appendix A, section 4(a)(4)(i

- iv), it will be eliminated from consideration. If a particu lar technology fails to meet one or more of the four criteria, it will be screened out. Further, certain technology options may be removed from consideration if it is determined that (1) they do not impact the efficiency metric as measured by the current test procedure; (2) they are already found in baseline units; or (3) there is insufficient information documenting the efficiency benefits of the technology in

CPB.

4.2 SCREENED

- OUT TECHNOLOGIES

This section describes the technologies that DOE eliminated for failure to meet one of the following four factors: (1) technological feasibility; (2) practicability to manufacture, install, and service; (3) impacts on equipment utility or equipment availability; and (4) adverse impacts on health or safety. DOE eliminat ed one technology for failure to meet one of these criteria.

4.2.1 Burner Derating

Decreasing the burner size to increase the ratio of heat transfer area to fuel input, or burner derating, can increase the thermal efficiency rating of commercial gas and oil

- fi red boilers

.

4-2However, because heat output rate is directly related to burner size, derating also reduces the amount of heated air available to the consumer. This reduction in heat output adversely affects the utility to consumers. Therefore, DOE did not co nsider this technology option further in the rulemaking analyses.

4.3 TECHNOLOGIES THAT HA VE NEGLIGIBLE OR NO IMPACT ON

THERMAL OR COMBUSTIO N EFFICIENCY AS MEAS URED BY THE

DEPARTMENT OF ENERGY TEST PROCEDURE

DOE further refined the list of technology options c onsidered in the successive analyses stages by removing several technology options for which implementation would have minimal or

no ef fect on thermal or combustion efficiency as mea sured by the DOE test procedure. Thus, DOE believes these technologies are unlikely to be implemented in response to changes to the DOE energy conservation standards. Although these options may not significantly improve rated efficiency of CPBs and are not included in the engineering analysis, DOE does not discourage

their use b y manufacturers, because of their potential to reduce energy consumption and increase efficiency. For each technology removed, DOE has provided an explanation of why the technology does not affect thermal and/or combustion efficiency.

4.3.1 Combustion Prehea ters

Combustion preheaters capture heat from flue gases to preheat incoming combustion air. Although combustion preheaters effectively raise the operating efficiency of the boiler in the field, this efficiency is not measured or calculated directly by th e test procedure. The test procedure requires that the inlet air be within ± 5°F of the room ambient temperature . Therefore, DOE eliminated this technology from the engineering analysis.

4.3.2 Economizers

An economizer is a device that can be installed on a boiler to save energy by preheating supply water with boiler exhaust gases

. Although economizers utilize otherwise wasted heat, and may improve the overall efficiency of the boiler, they have no impact on the thermal efficiency as measured by the DOE test procedure. This is because according to the test procedure, the inlet water has a set temperature. Therefore, DOE eliminated economizers from further consideration in the engineering analysis.

4-34.3.3 Blow

- down Waste Heat Recovery

In large steam commercial bo ilers, salt and sediment residue gets left out in the water

stored in the boiler. These dissolved solids are known as total dissolved solids and are removed from the boiler in a process known as blow

- down. Depending on size of boiler, blow

- down can

either be a continuous, periodic, or a maintenance process. In any case, stored heat energy in

blow

- down water which would otherwise be wasted away in a drain can be utilized to preheat incoming water. This blow

- down process may require a separator which separate s water from steam. By integrating this technology, there is potential to reduce fuel requirement to achieve desired water temperature. This technique may also marginally increase efficiency levels as the stored heat derived from combustion gases is utili zed to a greater extent.

The DOE test procedure is performed in a laboratory setting on boilers which have not previously been commissioned for service in a building. Therefore, sediment, dissolved solids, and other deposits will not be present in the boiler, and therefore blow

- down procedures will not be required, and blow

- down is not captured in the current test procedure. Thus, an increase in efficiency from blow

- down waste heat recovery would not be measured, thus this technology

was not considered in the engineering analysis.

4.3.4 Jacket Insulation Optimization

For any equipment that is insulated to prevent energy loss, there exists a relationship between the overall increase in diameter (or external geometry) due to insulation thickness and

the therma l resistance (depending on the thermal conductivity of the insulating material). The optimization of insulation thickness presents an opportunity to apply insulation of only the required amount and that is sufficient to prevent considerable heat loss.

Fro m a review of literature and manufacturer interviews, DOE notes that a blanket 2

- 3 inches insulation is typically used on many boiler models. Although there exists an opportunity to optimize the insulation, based on a review of product literature, DOE beli eves the potential gain in efficiency (combustion or thermal) is negligible.

4.4 TECHNOLOGY OPTIONS F OUND IN BASELINE UNI TS

After eliminating those techn ologies that do not increase thermal efficiency and screening out those technologies that do not meet the requirements of 10 CFR 430, subpart C, appendix A, section 4(a)(4)(i

- iv) , DOE identified the technologies that are already commonly found in

baseline CPBs as listed in Table 4.4

. 1 . Although DOE did not consider these technologies as options for improving the efficiency in comparison to the baseline, the costs of these components

4-4was captured in the engineering analysis at the baseline efficiency level. For certain compo nents, DOE lists multiple technologies if there is more than one type of component commonly found in baseline equipment.

Table 4.4

. 1 Technologies Found in Common Baseline Boiler Designs

Gas Valve: Single Stage, Two Stage, or Modulating Primary Heat Exchanger: Cast Iron Sectional; Water Tube; Fire Tube; Copper Fin

- Tube; Carbon Steel

Jacket Insulation

4.5 REMAINING TECHNOLOGY OPTIONS

After eliminating all the technology options by the methods described above , DOE considered the technologies listed in Table 4.5

. 1

.

Table 4.5

. 1 Design Options for Commercial P ackaged Boilers Analyzed in the Engineering Analysis Addition of condensing, secondary heat exchanger Increased primary heat exchanger surface area Incorporation of heat exchanger surface features (such as dimples) and internal features (such as baffles, turbulators, micro

- fins, corrugation, or rifling) with the purpose of inducing turbulent flow on either the air or water side of the heat exchanger Flat, wavy or louvered tube heat exchanger with or without staggered fin configuration

Premix burners

Pulse combustion Low pressure, air atomized oil burner

4-5