Energy Efficiency

Concepts and Calculations

Daniel M. Martinez,Ben W. Ebenhack,Travis P. Wagner

• Éditeur: Elsevier Science
• Année: 2019
• ISBN:
  9780128123164
• Sujet: Physical Sciences
• Sous-sujet: Energy

Energy Efficiency: Concepts and Calculations is the first book of its kind to provide an applied, systems oriented description of energy intensity and efficiency in modern economies across the entire energy chain. With an emphasis on analysis, specifically energy flow analysis, lifecycle energy accounting, economic analysis, technology evaluation, and policies/strategies for adopting high energy efficiency standards, the book provides a comprehensive understanding of the concepts, tools and methodologies for studying and modeling macro-level energy flows through, and within, key economic sectors (electric power, industrial, commercial, residential and transportation).

Providing a technical discussion of the application of common methodologies (e.g. cost-benefit analysis and lifecycle assessment), each chapter contains figures, charts and examples from each sector, including the policies that have been put in place to promote and incentivize the adoption of energy efficient technologies.

• Contains models and tools to analyze each stage at the macro-level by tracking energy consumption and how the resulting data might change energy use
• Includes accessible references and a glossary of common terms at the end of each chapter
• Provides diagnostic figures, tables and schematics within the context of local, regional and national energy consumption and utilization

Chapter 1

Introductory concepts

Abstract

In this introductory chapter, we present descriptions of the common terms used to understand energy efficiency, along with means to conceptualize primary energy and energy use. We close with an energy efficiency calculation, assessing total or cumulative system efficiency for lighting, powered by different primary energy sources. Key chapter points include as follows: distinguishing efficiency from conservation, reasons for studying end use and efficiency, and understanding the supply and end-use chain.

Keywords

Efficiency; sources; carriers; intensity; supply chain

Chapter Outline

• 1.1 Defining Energy Efficiency 2
  • 1.1.1 Energy Efficiency Versus Conservation 2
• 1.2 Impetus for Understanding and Employing Energy Efficiency 4
  • 1.2.1 Social Factors 4
  • 1.2.2 Macroeconomic Factors 6
  • 1.2.3 Other Kinds of Efficiency 8
• 1.3 Energy Sources and Energy Carriers 9
  • 1.3.1 Primary Energy 10
  • 1.3.2 Secondary Energy 12
• 1.4 The Energy Supply/Demand Chain 12
  • 1.4.1 Supply Acquisition 12
  • 1.4.2 Energy Extraction 14
  • 1.4.3 Energy Conversion 17
  • 1.4.4 Energy Processing 19
  • 1.4.5 Energy Distribution/Transport 22
  • 1.4.6 Energy End-Use and Utilization 23
• 1.5 Efficiency Calculation: Assessing Cumulative or Total System Efficiency 25
  • 1.5.1 System Efficiency of Illumination Via Incandescent Lighting From Coal-Fired Electricity 26
  • 1.5.2 System Efficiency of Illumination Via Light Emitting Diode Lighting From Coal-Fired Electricity 27
  • 1.5.3 System Efficiency of Illumination Via Light Emitting Diode Lighting From Natural Gas-Fired Electricity 28
  • 1.5.4 System Efficiency of Illumination Via Light Emitting Diode Lighting From Solar PV Technology 29
  • 1.5.5 Final Thoughts on Cumulative Efficiencies 31
• 1.6 Sources of Energy Efficiency Information 32
• References and Further Reading 33

In this introductory chapter, we present descriptions of the common terms used to understand energy efficiency, along with means to conceptualize primary energy and energy use. We close with an energy efficiency calculation, assessing total or cumulative system efficiency for lighting, powered by different primary energy sources. Key chapter points include:

• • distinguishing efficiency from conservation,
• • reasons for studying end use and efficiency, and
• • understanding the supply and end-use chain.

1.1 Defining Energy Efficiency

Energy efficiency is, by definition, a measure of the useful work produced per unit of energy used in an energy conversion. To the extent that energy conversions have a thermodynamic cost, efficiency measures the ratio of the energy sought to the total energy put into the system, such as in an energy conversion device or process. The closer the ratio of energy sought to energy input is to one, the more efficient it is. Thus, efficiency ultimately refers to the ability of an energy conversion device or process to successfully transform one energy form into another more useful form, while minimizing any undesired energy conversions that exist due to the laws of thermodynamics, such as low-grade heat losses that can not be used for any useful purpose. Moreover, improved efficiency refers specifically to technical improvements in devices and processes, which reduce any excess input costs while maintaining the same degree of energy service sought, within a measurable timeframe.

Alternatively, others point out that unit energy consumption (also known as specific energy consumption) may sometimes be more useful for understanding energy efficiency, because it specifies the amount of energy needed to produce a certain amount of product or service from a certain device or process. The smaller the amount of energy used to produce a certain quantity of valuable product or service, the more efficient the device or process is. So, whereas energy efficiency is considered dimensionless (energy out divided by energy in), unit energy consumption has dimensions, such as joules of energy needed to produce a ton of steel, or liters of fuel needed to move a vehicle 100 kilometers. To reduce unit energy consumption in a device or process, thereby improving efficiency, that device or process would need to undergo a design or operational change (i.e., to reduce the number of joules to produce a tonne of steel).

1.1.1 Energy Efficiency Versus Conservation

Efficiency should not be conflated with conservation, as conservation refers not to technical improvements in processes, but to policy decisions and behavioral choices. It may include decisions to employ or invest in improved technologies, representing an overlap with efficiency. Policies can be designed to require development of energy efficiency (e.g., fuel economy standards) and to encourage the development of energy efficiency products (e.g., ENERGY STAR appliances).

Likewise, policies can be crafted to encourage the installation of energy conservation devices using tax credits and rebates while policies can also be used to promote energy conservation such as adopting progressive rate charges for higher energy consumption. Many conservation choices, though, are voluntary behavioral actions to avoid or defer consumption. These choices can range from rather obvious, “painless” choices, such as turning off lights and electronics when not in use, to choices that may reduce benefits, such as turning thermostats down in the winter.

Efficiency and conservation are often mistakenly viewed as synonymous. While they are related, they are also distinct. For instance, improved efficiency can be a means to achieve conservation, but not the other way around. Efficiency is a technical function of the energy input relative to the useful work accomplished. Choosing to eliminate an activity does not improve efficiency, but rather can lead to clear energy savings—conservation.

Conservation refers to measures to reduce energy use. These measures can include austerity choices to reduce energy consuming activities or incentives to employ more efficient technologies to do the same things with less energy input. Conservation involves making choices, which often include decisions to forego some activities or to change how they are done. It is also true that conservation reliably results from higher energy prices. For example, total miles driven decreases when fuel prices increase as people choose not to take as many pleasure trips or shift to public transportation, taxis, or transportation network companies, but such choices are clearly not examples of improved efficiency.

Efficiency and conservation are certainly related, although not identical. Efficiency improvements typically lead to conserving energy (with the exception of the partial role that the so-called rebound-effect plays). The overlap on the Venn diagram in Fig. 1.1 represents the conservation that is realized by efficiency improvements.

Figure 1.1 A Venn diagram of efficiency and conservation. The overlap represents the conservation that is realized by efficiency improvements.

1.2 Impetus for Understanding and Employing Energy Efficiency

Dramatic transformations in our use of energy lie ahead. Change will be forced on us by ultimate shortages in some of the critical resources on which we have come to depend and on concerns for environmental impacts. Finite resources (coal, oil, gas, and uranium for nuclear fission), which provide the vast majority of the world’s current energy sources, will inevitably deplete. Crude oil, the life blood of the world’s transport needs and habits, will probably be the first of the finite sources to be constrained by depletion; nevertheless, all the finite resources face these limits. There is also a worldwide desire to reduce emissions from drilling, mining, and mobile and stationary combustion point-sources. Oxides of nitrogen and sulfur, particulate matter, and greenhouse gases are all emissions from increasing consumption of wood and fossil fuel sources for heating, electricity, manufacturing, and transportation, as well as increasing pollution in the natural environment.

Energy efficiency is one of the most valuable responses to these combined challenges. The energy that is not needed, because of enhanced efficiency, will be the equivalent of additional new energy produced. Indeed, it will be better, because efficiency enhancements will generally have little or no on-going environmental impacts. Efficiency improvements are inexhaustible. Once an efficient technology is developed and deployed, it can continue to be used and further deployed until it either saturates the market or is superseded by an even better, more efficient technology. As such, energy efficiency will play an increasingly prominent role in the local, regional, and national agendas of most developed countries.

Of course, there are always other considerations besides efficiency, including pollution and other emissions. For these issues, noncombustion primary sources have a clear advantage. However, evaluating the “life cycle” efficiency of these systems, based on flux-limited resources (e.g., solar and wind), depends on the system boundaries. In particular, does the energy flow being tapped count as energy input, or should we only count anthropogenically controlled energy input? Efficiency must be evaluated within the context of what we seek, which would be the goods and services provided by the energy—at the least direct economic cost.

1.2.1 Social Factors

The ability to harness external energy sources transformed the lives of humans dramatically many thousands of years before anyone developed a language for the economy. Energy systems have continuously evolved to provide greater power for humans and with ever-greater control. We are entirely surrounded by the benefits of energy use: from the simplest forms of cooking meals, to the most sophisticated telecommunications, or the mightiest industries.

Nations using very little external energy have invariably low economic and social advantages, while the affluent nations, with high qualities of life, have relatively high per capita energy consumption (PCEC). Studying the relationship between energy use and quality o...