Category: Electrochromic windows

New Book: ‘Water, Energy, and Environment – A Primer’

After a long hiatus from blogging while I worked on a new book, I am pleased to announce that the book ‘Water, Energy, and Environment – A Primer’ will be published by International Water Association Publishing (IWAP) on February 18th (2019). It will be available in both printed and digital form, and the digital version will be downloadable for free as an Open Access (OA) document.

To access the free digital version go to IWAP’s OA website on Twitter: https://twitter.com/IWAP_OA.

Attached below is front material from the book, its preface and table of contents. Designed to serve as a basic and easily read introduction to the linked topics of water, energy, and environment, it is just under 200 pages in length, a convenient size to throw into a folder, a briefcase, or a backpack. Its availability as an OA document means that people all over the world with access to the internet will have access to the book and its 10 chapters.

With the completion of the book I plan to return to a regular schedule of blogging.
…………………………..
Contents
Preface ………………………………….. xi
Acknowledgement ……………………….. xv
Acronyms ……………………………… xvii
Epigraph ……………………………….. xxi
Chapter 1
Water and its global context …………………. 1
1.1 Earth’s Water Resources . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Saline Water and Desalination Processes . . . . . . . . . . . 2
1.3 Energy Requirements and Costs of Desalination . . . . . 5
1.4 Demand for Freshwater . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.5 Implications of Limited Access to Freshwater . . . . . . . . . 9
1.6 Actions to Increase Access to Freshwater . . . . . . . . . . 10
1.7 Gender Equity Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Chapter 2
Energy and its global context ……………….. 13
2.1 Energy’s Role in Society . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2 Energy Realities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3 What is Energy? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.4 Energy Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.4.1 Important questions . . . . . . . . . . . . . . . . . . . . . . . 18
2.4.2 How is energy used? . . . . . . . . . . . . . . . . . . . . . . 18
2.4.3 Electrification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Chapter 3
Exploring the linkage between water
and energy ……………………………….. 23
3.1 Indirect Linkages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.2 The Policy Linkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3 The Conundrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.4 Addressing the Conundrum . . . . . . . . . . . . . . . . . . . . . . . 26
3.5 The Need for Partnership . . . . . . . . . . . . . . . . . . . . . . . . . 27
Chapter 4
Energy production and its consequences for
water and the environment …………………. 29
4.1 Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2 More on Climate Change . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.3 Environment and Religion . . . . . . . . . . . . . . . . . . . . . . . . 33
4.3.1 The theocentric worldview . . . . . . . . . . . . . . . . . 33
4.3.2 The anthropocentric worldview . . . . . . . . . . . . . 34
4.3.3 Other worldviews . . . . . . . . . . . . . . . . . . . . . . . . . 34
Chapter 5
Energy options ……………………………. 37
5.1 Fossil Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.2 Nuclear Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.3 Geothermal Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.4 The Sun . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.5 Energy Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.5.1 Energy demand . . . . . . . . . . . . . . . . . . . . . . . . . . 40
vi Water, Energy, and Environment – A Primer
5.5.2 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.5.3 Saving energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.5.4 Accelerating implementation . . . . . . . . . . . . . . . 43
5.5.5 Energy Star . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
5.5.6 The lighting revolution . . . . . . . . . . . . . . . . . . . . . 45
5.5.7 Energy efficiency in buildings . . . . . . . . . . . . . . . 48
5.5.7.1 Zero energy buildings . . . . . . . . . . . . . 48
5.5.7.2 Electrochromic windows . . . . . . . . . . . 52
5.6 Energy Efficiency in Industry . . . . . . . . . . . . . . . . . . . . . . 54
5.7 Energy Efficiency in Transportation . . . . . . . . . . . . . . . . 56
Chapter 6
Fossil fuels ………………………………. 61
6.1 Coal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
6.1.1 Carbon capture and sequestration . . . . . . . . . . 63
6.1.2 A conundrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
6.2 Petroleum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
6.2.1 Oil spills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
6.2.2 Peak oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
6.3 Natural Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
6.3.1 Methane hydrates . . . . . . . . . . . . . . . . . . . . . . . . . 77
6.3.2 Fracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Chapter 7
Nuclear power ……………………………. 85
7.1 Nuclear Fission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
7.1.1 Fission fundamentals . . . . . . . . . . . . . . . . . . . . . . 85
7.1.2 Introduction to nuclear issues . . . . . . . . . . . . . . . 87
7.1.3 Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
7.2 Nuclear Fusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
7.2.1 Fusion fundamentals . . . . . . . . . . . . . . . . . . . . . . 91
7.2.2 Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
7.2.3 Barriers to Fusion . . . . . . . . . . . . . . . . . . . . . . . . . 94
7.2.4 Pros and cons . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
7.2.5 Thoughts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Chapter 8
Renewable energy ………………………… 97
8.1 The Sun’s Energy Source and Radiation
Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
8.2 Direct Solar Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
8.2.1 Photovoltaics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
8.2.2 Concentrating solar power (CSP) . . . . . . . . . . 108
8.2.2.1 Power tower . . . . . . . . . . . . . . . . . . . . 109
8.2.2.2 Linear concentrator . . . . . . . . . . . . . . 110
8.2.2.3 Dish engine . . . . . . . . . . . . . . . . . . . . . 111
8.2.2.4 CSTP history . . . . . . . . . . . . . . . . . . . 112
8.2.2.5 Advantages and disadvantages . . . 112
8.2.2.6 Thermal storage . . . . . . . . . . . . . . . . . 113
8.2.2.7 Current status . . . . . . . . . . . . . . . . . . . 114
8.2.2.8 Concentrating photovoltaics (CPV) . 115
8.3 Solar Power Satellite (SPS) System . . . . . . . . . . . . . . 116
8.4 Hydropower and Wind Energy . . . . . . . . . . . . . . . . . . . 119
8.4.1 Hydropower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
8.4.2 Wind energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
8.4.2.1 Onshore wind . . . . . . . . . . . . . . . . . . . 121
8.4.2.2 History . . . . . . . . . . . . . . . . . . . . . . . . . 124
8.4.2.3 An onshore limitation . . . . . . . . . . . . . 124
8.4.2.4 Offshore wind . . . . . . . . . . . . . . . . . . . 125
8.5 Biomass Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
8.5.1 Sources of biomass . . . . . . . . . . . . . . . . . . . . . . 129
8.5.2 Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
8.5.3 Biofuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
8.5.4 Algae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
8.5.5 Biochar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
8.5.6 The future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
8.6 Geothermal Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
8.6.1 Sources of geothermal energy . . . . . . . . . . . . . 134
8.6.2 Manifestations of geothermal energy . . . . . . . 135
8.6.3 Uses of geothermal energy . . . . . . . . . . . . . . . . 135
8.6.3.1 Geothermal power generation . . . . . 136
8.6.3.2 Ground-source heat pumps . . . . . . . 138
8.6.4 An unusual source of geothermal energy . . . . 140
Ocean Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
8.7.1 Wave energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
8.7.1.1 Wave energy conversion
devices . . . . . . . . . . . . . . . . . . . . . . . . 142
8.7.1.2 Potential and pros and cons . . . . . . . 143
8.7.2 Ocean current energy . . . . . . . . . . . . . . . . . . . . 144
8.7.3 Tidal energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
8.7.3.1 Barrage . . . . . . . . . . . . . . . . . . . . . . . . 146
8.7.3.2 History . . . . . . . . . . . . . . . . . . . . . . . . . 147
8.7.3.3 Environmental impacts . . . . . . . . . . . 147
8.7.4 Ocean thermal energy conversion (OTEC) . . 147
8.7.4.1 Barriers . . . . . . . . . . . . . . . . . . . . . . . . 148
8.7.4.2 OTEC technologies . . . . . . . . . . . . . . 148
8.7.4.3 Other cold water applications . . . . . . 149
8.7.4.4 OTEC R&D . . . . . . . . . . . . . . . . . . . . . 149
Chapter 9
Energy storage …………………………… 151
9.1 Storage and Grids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
9.2 Types of Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
9.2.1 Traditional and advanced batteries . . . . . . . . . 153
9.2.1.1 Lead–acid . . . . . . . . . . . . . . . . . . . . . . 153
9.2.1.2 Sodium sulfur . . . . . . . . . . . . . . . . . . . 153
9.2.1.3 Nickel–cadmium . . . . . . . . . . . . . . . . . 154
9.2.1.4 Lithium-ion . . . . . . . . . . . . . . . . . . . . . 154
9.2.1.5 Supercapacitors . . . . . . . . . . . . . . . . . 155
9.2.2 Flow batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
9.2.3 Flywheels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
9.2.4 Superconducting magnetic energy
storage (SMES) . . . . . . . . . . . . . . . . . . . . . . . . . 158
9.2.5 Compressed air energy storage (CAES) . . . . 159
9.2.6 Pumped storage . . . . . . . . . . . . . . . . . . . . . . . . . 160
9.2.7 Thermal storage . . . . . . . . . . . . . . . . . . . . . . . . . 161
9.3 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
9.4 Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
9.5 Fundamental Change . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Chapter 10
Policy considerations …………………….. 165
10.1 Important Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
10.1.1 Is there a physical basis for understanding
global warming and climate change? . . . . . . 166
10.1.2 Is there documented evidence for global
warming and climate change? . . . . . . . . . . . . 168
10.1.3 Can global warming and climate change be
attributed to human activities, and what are
those activities? . . . . . . . . . . . . . . . . . . . . . . . . 170
10.1.4 What are the potential short- and long-term
impacts of global warming and climate
change with respect to water supply,
environment, and health? What is the
anticipated time scale for these
impacts? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
10.1.5 What can be done to mitigate the onset
and potential impacts of global warming
and climate change? . . . . . . . . . . . . . . . . . . . . 179
References ……………………………… 183
Index …………………………………… 189

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Preface
This book springs from my strong conviction that clean water and clean energy are the critical elements of long-term global sustainable development. I also believe that we are experiencing the beginning of an energy revolution in these early years of the 21st century. Providing clean water requires energy, and providing clean energy is essential to reducing the environmental impacts of energy production and use. Thus, I see a nexus – a connection, a causal link – among water, energy, and environment. In recent years we have adopted the terminology of the water-energy nexus for the intimate relationship between water and energy, and similarly we can apply the term nexus to the close connections among water, energy, and environment. Thisuse of the term nexus can be, and has been, extended to include the related issues of food production and health. Dealing with, and writing about, a two-element nexus is difficult enough. In this book, I will limit my analysis and discussion to the three-element water -energy-environment nexus and leave the discussion of other possible nexus elements to those more qualified to comment.

This book also springs from my observation that while there are many existing books of a more-or-less technical nature on the three elements of this nexus, a book addressing each of them and their interdependencies in a college-level primer for a broad global and multidisciplinary audience would be valuable. Consideration of these and related issues, and options for addressing them, will be priorities for all levels of government. They will also be priorities for many levels of the
private sector in the decades ahead, both in developing and developed nations. A handbook-style primer that provides an easily read and informative introduction to, and overview of, these issues will contribute broadly to public education. It will assist governments and firms in carrying out their responsibilities to provide needed services and goods in a sustainable manner, and help to encourage young people to enter these fields. It will serve as an excellent mechanism for exposure of experts in other fields to the issues associated with the water-energy-environment nexus. Further, in addition to the audiences mentioned above, target audiences include economists and others in the finance communities who will analyze and provide the needed investment funds, and those in the development community responsible for planning and delivering services to underserved populations.
The book is organized as follows: the first chapter will be devoted to the concept of nexus and how the three elements, water, energy, and environment, are inextricably linked. This recognition leads to the conclusion that if society is to optimize their contributions to human and planetary welfare they must be addressed jointly. No longer must policy for each of these elements be considered in its own silo. Chapters 2 and 3 will be devoted to spelling out global contexts for water and energy issues, respectively. Chapter 4, on related environmental issues, will address the issues of water contamination, oil spills, fracking, radioactive waste storage, and global warming/
climate change. Chapter 5 will be a discussion of energy efficiency – i.e., the wise use of energy – and its role in limiting energy demand and its associated benefits. Chapter 6 will focus on the basics of fossil fuels – coal, oil, natural gas – which today dominate global energy demand. Chapter 7 will discuss nuclear-fission-powered electricity production, which today accounts for 10% of global electricity. It will also discuss the prospects for controlled nuclear fusion. Chapter 8 will discuss the broad range of renewable energy technologies – wind, solar,hydropower, biomass, geothermal, ocean energy – which are the basis of the now rapidly emerging energy revolution. Chapter 9 will discuss the closely related issue of energy storage. Finally, Chapter 10 will address
policy issues associated with water, energy, and environment, discuss policy history and options, and provide recommendations.

Zero Energy Buildings: They May Be Coming Sooner Than You Think

Buildings account for approximately 40 percent of the energy (electrical, thermal) used in the U.S. and Europe, and an increasing share of energy used in other parts of the world. Most of this energy today is fossil-fuel based. As a result, this energy use also accounts for a significant share of global emissions of carbon dioxide.

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Source: U.S. Department of Energy, Buildings Energy Data Book

These simple facts make it imperative that buildings, along with transportation fleets and power generation, be primary targets of reduced global energy and fossil fuel demand. This blog post discusses one approach in buildings that is gaining increasing visibility and viability, the introduction of net zero energy buildings and the retrofit of existing buildings to approach net zero energy operation. A net zero energy building (NZEB or ZEB) is most often defined as a building that, over the course of a year, uses as much energy as is produced by renewable energy sources on the building site. This is the definition I will focus on. Other ZEB definitions take into account source energy losses in generation and transmission, emissions (aka zero carbon buildings), total cost (cost of purchased energy is offset by income from sales of electricity generated on-site to the grid), and off-site ZEB’s where the offsetting renewable energy is delivered to the building from off-site generating facilities. Details on these other definitions can be found in the 2006 NREL report CP-550-39833 entitled “Zero Energy Buildings: A Critical Look at the Definition”.

The keys to achieving net zero energy buildings are straight forward in principle: first focus on reducing the building’s energy demand through energy efficiency, and then focus on meeting this energy demand, on an annual basis, with onsite renewable energy – e.g., use of localized solar and wind energy generation. This allows for a wide range of approaches due to the many options now available for improved energy efficiency in buildings and the rapidly growing use of solar photovoltaics on building roofs, covered parking areas, and nearby open areas. Most ZEB’s use the electrical grid for energy storage, but some are grid-independent and use on-site battery or other storage (e.g., heat and coolth).

A primary example of what can be done to achieve ZEB status is NREL’s operational RSF (Research Support Facility) at its campus in Golden, Colorado, shown below.

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It incorporates demand reduction features that are widely applicable to many other new buildings, and some that make sense for residential buildings and retrofits as well (cost issues are discussed below). These include:
– optimal building orientation and office layout, to maximize heat capture from the sun in winter, solar PV generation throughout the year, and use of natural daylight when available
– high performance electrical lighting
– continuous insulation precast wall panels with thermal mass
– windows that can be opened for natural ventilation
– radiant heating and cooling
– outdoor air preheating, using waste heat recovery, transpired solar collectors, and crawl space thermal storage
– aggressive control of plug loads from appliances and other building equipment
– advanced data center efficiency measures
– roof top and parking lot PV arrays

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U.S. ZEB research is supported by DOE’s Building America Program, a joint effort with NREL, Lawrence Berkeley National Laboratory, Oak Ridge National Laboratory, and several industry-based consortia – e.g., the National Institute of Building Sciences and the American Institute of Architects. Many other countries are exploring ZEB’s as well, including jointly through the International Energy Agency’s “Towards Net Zero Energy Solar Buildings” Implementing Agreement (Solar Heating and Cooling Program/Task 40). This IEA program has now documented and analyzed more than 300 net zero energy and energy-plus buildings worldwide (an energy-plus building generates more energy than it consumes).

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An interesting example of ZEB technology applied to a residential home is NREL’s Habitat for Humanity zero energy home (ZEH), a 1,280 square foot, 3-bedroom Denver area home built for low income occupants. NREL report TP-550-431888 details the design of the home and includes performance data from its first two years of operation (“The NREL/Habitat for Humanity Zero Energy Home: a Cold Climate Case Study for Affordable Zero Energy Homes”). The home exceeded its goal of zero net source energy and was a net energy producer for these two years (24% more in year one and 12% more in year two). The report concluded that “Efficient, affordable ZEH’s can be built with standard construction techniques and off-the-shelf equipment.”

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The legislative environment for ZEB’s is interesting as well. To quote from the Whole Building Design Guide of the National Institute of Building Sciences:
“Federal Net Zero Energy Building Goals
Executive Order 13514, signed in October 2009, requires all new Federal buildings that are entering the planning process in 2020 or thereafter be “designed to achieve zero-net-energy by 2030”. “In addition, the Executive Order requires at least 15% of existing buildings (over 5,000 gross square feet) meet the Guiding Principles for Federal Leadership in High Performance and Sustainable Buildings by 2015, with annual progress towards 100% conformance”.
Two milestones for NZEB have also been defined by the Department of Energy (DOE) for residential and commercial buildings. The priority is to create systems integration solutions that will enable:
Marketable Net Zero Energy Homes by the year 2020
Commercial Net Zero Energy Buildings at low incremental cost by the year 2025.
These objectives align with the Energy Independence and Security Act of 2007 (EISA), which calls for a 100% reduction in fossil-fuel energy use (relative to 2003 levels) for new Federal buildings and major renovations by 2030.”

A word about cost: ZEB’s cost more today to build than traditional office buildings and homes, but not much more (perhaps 20% for new construction). Of course, part of this extra cost is recovered via reduced energy bills. In the future, the zero energy building goal will become more practical as the costs of renewable energy technologies decrease (e.g., PV panel costs have decreased significantly in recent years) and the costs of traditional fossil fuels increase. The recent surge in availability of relatively low cost shale gas from fracking wells will slow this evolution but it will eventually occur. Additional research on cost-effective efficiency options is also required.

To sum up, the net zero energy building concept is receiving increasing global attention and should be a realistic, affordable option within a few decades, and perhaps sooner. ZEB’s offer many advantages, as listed by Wikipedia:
“- isolation for building owners from future energy price increases
– increased comfort due to more-uniform interior temperatures
– reduced total net monthly cost of living
– improved reliability – photovoltaic systems have 25-year warranties – seldom fail during weather problems
– extra cost is minimized for new construction compared to an afterthought retrofit
– higher resale value as potential owners demand more ZEBs than available supply
– the value of a ZEB building relative to similar conventional building should increase every time energy costs increase
– future legislative restrictions, and carbon emission taxes/penalties may force expensive retrofits to inefficient buildings”

ZEB’s also have their risk factors and disadvantages:

“- initial costs can be higher – effort required to understand, apply, and qualify for ZEB subsidies
– very few designers or builders today have the necessary skills or experience to build ZEBs
– possible declines in future utility company renewable energy costs may lessen the value of capital invested in energy efficiency
– new photovoltaic solar cells equipment technology price has been falling at roughly 17% per year – It will lessen the value of capital invested in a solar electric generating system. Current subsidies will be phased out as photovoltaic mass production lowers future price
– challenge to recover higher initial costs on resale of building – appraisers are uninformed – their models do not consider energy
– while the individual house may use an average of net zero energy over a year, it may demand energy at the time when peak demand for the grid occurs. In such a case, the capacity of the grid must still provide electricity to all loads. Therefore, a ZEB may not reduce the required power plant capacity.
– without an optimised thermal envelope the embodied energy, heating and cooling energy and resource usage is higher than needed. ZEB by definition do not mandate a minimum heating and cooling performance level thus allowing oversized renewable energy systems to fill the energy gap.
– solar energy capture using the house envelope only works in locations unobstructed from the South. The solar energy capture cannot be optimized in South (for northern hemisphere, or North for southern Hemisphere) facing shade or wooded surroundings.”

Finally, it is important to note that the energy consumption in an office building or home is not strictly a function of technology – it also reflects the behavior of the occupants. In one example two families on Martha’s Vineyard in Massachusetts lived in identical zero-energy-designed homes and one family used half as much electricity in a year as the other. In the latter case electricity for lighting and plug loads accounted for about half of total energy use. As energy consultant Andy Shapiro noted: “There are no zero-energy houses, only zero-energy families.”

Electrochromic Windows: We Need to Get the Cost Down

A technology that has fascinated me since I first saw it demonstrated nearly forty years ago is the electrochromic window. It is part of the family of smart glass technologies that control the amount of light and heat that the glass transmits. This control can be activated by temperature (thermochromic), by light (photochromic), or voltage (electrochromic). This blog post will focus on the latter, which offers significant potential for reducing the energy consumed in buildings. Electrochromic windows have other useful applications as well.

How do electrochromic windows work?

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When a voltage is applied between the transparent electrical conductors (usually less than 5 volts) an electric field is set up in the window material. This field moves ions reversibly through the ion storage film through the electrolyte and into the electrochromic film. Different ions (typically lithium or hydrogen) produce different colorations, and the window can be switched between a clear, highly transparent state and a transparent blue-gray tinted state with no degradation in view (similar to that achieved in photochromic sunglasses) by reversing voltage polarities. Critical aspects of electrochromic windows include material and manufacturing costs, installation costs, electricity costs, and durability, as well as functional features such as degree of transparency, possibilities for dimming, and speed of transmission control (complete switching can take several minutes). Many different electrochromic window options at different price points for buildings are now available, and active R&D efforts are underway. One recent advance is the development of reflective, rather than absorptive, windows which switch between transparent and mirror-like.

Electrochromic windows are an attractive energy efficiency measure because they can block heat (infrared radiation) in the summer, reducing air conditioning loads, and allow infrared wavelengths to pass into buildings in the winter and reduce heating loads (windows account for about 30% of building energy load). This also reduces utility peak load demands. Tunable electrochromic windows also serve to reduce lighting loads when adequate natural light is available, reduce glare, provide privacy without the need for blinds and curtains, and reduce fabric and art fading by blocking ultraviolet radiation.

Important applications, in addition to reducing energy demand and increasing human comfort, include use in automobile windows, sunroofs and rear view mirrors, in aircraft (e.g., the Boeing 787 Dreamliner uses electrochromic windows in place of pull down window shades), and as internal partitions in buildings with the ability to switch screens and doors from clear to private.

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Given that electrochromic (EC) windows have been under development for many decades, their obvious ability to block or transmit wavelengths of light as needed, and their many applications, why hasn’t greater use of such windows become a standard part of building construction. The simple answer is cost. NREL looked at this issue in its December 2009 report entitled ‘Preliminary Assessment of the Energy-Saving Potential of Electrochromic Windows in Residential Buildings’ and compared the cost of low-e argon-filled windows with that of EC windows and concluded that “..EC windows would have to reach a price point of approximately $20/square foot before they would be competitive..” At that time EC windows were in the range $50-100/square foot, with commercial buildings on the lower end and residential applications on the higher end. Another approach bring taken by a few EC window companies is to add an EC film to existing windows, which reduces costs considerably.

How much energy can EC windows save? The NREL study, using a model to evaluate the performance of EC windows in a single-family traditional new home in Atlanta, predicted that whole-house energy demand could be reduced by 9.1% and whole-house electricity demand by 13.5%.

Looking globally, the U.S. and China have joined in a $150 million consortium called the U.S. China Clean Energy Research Center aimed at facilitating “joint research and development on clean energy technology. The consortium estimates that in the next 20 years China will build more square footage of floor space than the current total in the United States. The goal is to make those buildings as energy efficient as possible.”

Several new factories have been or are being built to produce EC windows or EC films and reduce costs significantly through economies of large-scale production. My intuition says this will happen soon, and will serve as an important step toward zero-energy buildings – i.e., buildings that use no more energy in a year than they produce through PV generation. A future blog will discuss zero-energy buildings in more detail.