Energy Audit of Building Systems

An Engineering Approach, Third Edition

Moncef Krarti

• Éditeur: CRC Press
• Année: 2020
• ISBN:
  9781000259773
• Édition: 3
• Sujet: Scienze fisiche
• Sous-sujet: Meccanica

Updated to include recent advances, this third edition presents strategies and analysis methods for conserving energy and reducing operating costs in residential and commercial buildings.

The book explores the latest approaches to measuring and improving energy consumption levels, with calculation examples and Case Studies. It covers field testing, energy simulation, and retrofit analysis of existing buildings. It examines subsystems—such as lighting, heating, and cooling—and techniques needed for accurately evaluating them.

Auditors, managers, and students of energy systems will find this book to be an invaluable resource for their work.

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• Explores state-of-the-art techniques and technologies for reducing energy combustion in buildings.

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• Presents the latest energy efficiency strategies and established methods for energy estimation.

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• Provides calculation examples that outline the application of the methods described.

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• Examines the major building subsystems: lighting, heating, and air-conditioning.
• Addresses large-scale retrofit analysis approaches for existing building stocks.
• Introduces the concept of energy productivity to account for the multiple benefits of energy efficiency for buildings.

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• Includes Case Studies to give readers a realistic look at energy audits.

Moncef Krarti has vast experience in designing, testing, and assessing innovative energy efficiency and renewable energy technologies applied to buildings. He graduated from the University of Colorado with both MS and PhD in Civil Engineering. Prof. Krarti directed several projects in designing energy-efficient buildings with integrated renewable energy systems. He has published over 3000 technical journals and handbook chapters in various fields related to energy efficiency, distribution generation, and demand-side management for the built environment. Moreover, he has published several books on building energy-efficient systems. Prof. Krarti is Fellow member to the American Society for Mechanical Engineers (ASME), the largest international professional society. He is the founding editor of the ASME Journal of Sustainable Buildings & Cities Equipment and Systems. Prof. Krarti has taught several different courses related to building energy systems for over 20 years in the United States and abroad. As a professor at the University of Colorado, Prof. Krarti has been managing the research activities of an energy management center at the school with an emphasis on testing and evaluating the performance of mechanical and electrical systems for residential and commercial buildings. He has also helped the development of similar energy efficiency centers in other countries, including Brazil, Mexico, and Tunisia. In addition, Prof. Krarti has extensive experience in promoting building energy technologies and policies overseas, including the establishment of energy research centers, the development of building energy codes, and the delivery of energy training programs in several countries.

1 Introduction to Energy Audit

1.1 INTRODUCTION

Since the oil embargo of 1973, significant improvements have been made in the energy efficiency of new buildings. However, the vast majority of the existing building stock is more than 20 years old and does not meet current energy efficiency construction standards (IEA, 2008). Therefore, energy retrofits of existing buildings will be required for decades to come if the overall energy efficiency of the building stock is to meet the standards.

Investing to improve the energy efficiency of buildings provides an immediate and relatively predictable positive cash flow resulting from lower energy bills. In addition to the conventional financing options available to owners and building operators (such as loans and leases), other methods are available to finance energy retrofit projects for buildings. One of these methods is performance contracting, in which payment for a retrofit project is contingent upon its successful outcome. Typically, an energy services company (ESCO) assumes all the risks for a retrofit project by performing the engineering analysis and obtaining the initial capital to purchase and install equipment needed for energy efficiency improvements. Energy auditing is an important step used by energy service companies to ensure the success of their performance contracting projects.

Moreover, several large industrial and commercial buildings have established internal energy management programs based on energy audits to reduce waste in energy use or to comply with the specifications of some regulations and standards. Other building owners and operators take advantage of available financial incentives typically offered by utilities or state agencies to perform energy audits and implement energy conservation measures (ECMs).

In the 1970s, building energy retrofits consisted of simple measures such as shutting off lights, turning down heating temperatures, turning up air-conditioning temperatures, and reducing hot water temperatures. Today, building energy management includes a comprehensive evaluation of almost all the energy systems within a facility. Therefore, the energy auditor should be aware of key energy issues, such as the subtleties of electric utility rate structures, and of the latest building energy efficiency technologies and their applications.

This chapter describes a general but systematic procedure for energy auditing suitable for both commercial buildings and industrial facilities. Some of the commonly recommended ECMs are briefly discussed. A case study for an office building is presented to illustrate the various tasks involved in an energy audit. Finally, an overview is provided to outline the existing methods for measurement and verification of energy savings incurred by the implementation of ECMs.

1.2 TYPES OF ENERGY AUDITS

The term “energy audit” is widely used and may have different meanings, depending on the energy service company. Energy auditing of buildings can range from a short walk-through of the facility to a detailed analysis with hourly computer simulation. Generally, there are four distinct types of energy audits, which are briefly described in the following sections.

1.2.1 WALK-THROUGH AUDIT

This audit, also referred to as level I audit, consists of a short on-site visit of the facility to identify areas where simple and inexpensive actions can provide immediate energy use or operating-cost savings. Some engineers refer to these types of actions as operating and maintenance (O&M) measures. Examples of O&M measures include setting back heating set-point temperatures, replacing broken windows, insulating exposed hot water or steam pipes, and adjusting boiler fuel-air ratio. A sample of a walk-through audit for a residence is provided in Chapter 17.

1.2.2 UTILITY COST ANALYSIS

The main purpose of this type of audit is to carefully analyze the operating costs of the facility. Typically, the utility data over several years is evaluated to identify the patterns of energy use, peak demand, weather effects, and potential for energy savings. To perform this analysis, it is recommended that the energy auditor conduct a walk-through survey to get acquainted with the facility and its energy systems.

It is important that the energy auditor clearly understand the utility rate structure that applies to the facility for several reasons:

• To check the utility charges and ensure that no mistakes were made in calculating the monthly bills. Indeed, the utility rate structures for commercial and industrial facilities can be quite complex with ratchet charges and power factor penalties.
• To determine the most dominant charges in the utility bills. For instance, peak demand charges can be a significant portion of the utility bill, especially when ratchet rates are applied. Peak shaving measures can then be recommended to reduce these demand charges.
• To identify whether the facility can benefit from using other utility rate structures to purchase cheaper fuel and reduce its operating costs. This analysis can provide a significant reduction in the utility bills especially with implementation of electrical deregulation and the advent of real-time pricing (RTP) rate structures.

Moreover, the energy auditor can determine whether the facility is a candidate for energy retrofit projects by analyzing the utility data. Indeed, the energy use of the facility can be normalized and compared to indices (for instance, the energy use per unit of floor area—for commercial buildings—or per unit of a product—for industrial facilities—as discussed in Chapter 4).

1.2.3 STANDARD ENERGY AUDIT

The standard audit, also referred to as level II audit, provides a comprehensive energy analysis for the energy systems of the facility. In addition to the activities described for the walk-through audit and for the utility cost analysis described above, the standard energy audit includes the development of a baseline for the energy use of the facility and the evaluation of the energy savings and the cost-effectiveness of appropriately selected ECMs. The st...