Category: energy efficiency

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.

Balancing Environmental Interests and Our Energy Future: Often A Difficult Call

I may be dipping my toe (foot?) in doo-doo by taking on this issue with my natural constituency – environmentalists – but here goes. Two articles in today’s (17 January 2014) Washington Post got my attention and stimulated this blog post.

The first piece, ‘Green groups assail Obama on climate’ (digital edition tile: ‘Environmental groups say Obama needs to address climate change more aggressively’), starts off as follows: “A group of the nation’s leading environmental organizations is breaking with the administration over its energy policy, arguing that the White House needs to apply a strict climate test to all its energy decisions or risk undermining one of the president’s second-term priorities.” It goes on to list a number of ways in which the Obama administration has taken steps to limit carbon dioxide emissions, but the environmentalists’ letter takes issue with the administration for “..embracing domestic production of natural gas, oil and coal under an “all of the above” energy strategy.”

The other Washington Post piece that got my attention was a brief reference to the draft of the soon-to-be-released IPCC (Intergovernmental Panel on Climate Change) report on global warming (‘U.N. cautions against delay on climate change’). It states: “Delaying action on global warming will only increase the costs and reduce the options for dealing with the worst effects of climate change…global warming will continue to increase unless countries cut emissions and shift quickly to clean energy.”

If one reviews my earlier posts in this blog it will be clear that I support a rapid transition to a clean energy future based on energy efficiency and renewable energy. Having devoted my professional career in government to that end, I believe that President Obama ‘gets it’ re global warming and the need for renewables. In fact, I chose not to retire from the U.S. Department of Energy in 2009, when I was more than old enough to do so, because we had finally elected a President who I believed did ‘get it’, after the frustrating years of Bush 43. I believe my trust was well founded based on President Obama’s subsequent behavior, in word and in action, and it bothers me that some of my environmental colleagues apparently see it differently. I may be getting old and you can say that I am getting more cranky and conservative in my dotage, but I don’t think so. I see myself as more aware of the realities of governing, especially after a long career in Washington, DC, and think Obama is doing a good job under very difficult circumstances (yes, I am referring to a dysfunctional Congress). I do see value in keeping the pressure up on a sometimes-too-political White House, but let’s at least acknowledge more often that the guy is doing a good job, and a much better one than Clinton and Gore did in the 1990’s when they faced similar political problems. Obama is finally getting us started on the path we should have been on twenty years ago.

To be more specific: I recognize and regret that the U.S. does not yet have an energy policy that creates the economic environment for a rapid transition to a clean energy future, as is true of a few other countries (e.g., the EU). It is critically needed, but the reality is that creating such a policy ultimately is the responsibility of our legislative branch. All the Executive Branch’s rhetoric can’t change that, although it has to keep pushing as much as it can and implementing as much as it can through executive orders.

One impact already is a significant reduction in power generation in the U.S. using coal, due to its replacement as a fuel by natural gas. This is due to the large amounts of shale gas released by fracking, a technology that I believe is unstoppable (see my blog entitled ‘Fracking: The Promise and the Problems’) and needs careful regulation. Many environmentalists oppose fracking because of the real risks it poses to water supplies, and I share those concerns, but the important upside is that using natural gas instead of coal for power generation puts much less carbon dioxide in the atmosphere. If renewables were ready soon to assume the power generation burden, and our transportation infrastructure was electrified and ready to use hydrogen in fuel cell vehicles (for which the hydrogen was generated from renewables-based electrolysis of water), then down with fracking for natural gas and oil. But that is not where we are today, and fracking and its economic returns will be with us for a while. Lots of work to prepare the way to our inevitable clean energy future still needs to be done. For similar reasons I do not oppose the Keystone Pipeline – I recognize its risks and wish we could avoid its extension, but stopping it is not going to stop Canada from exploiting its tar sands resources. I’d rather have that oil coming to the U.S. and reducing our continuing dependence on imports from other, less friendly countries. Imports are going down but will still be with us for a while until we introduce greater electrification of our transportation fleets.

Lots of other issues come into this discussion, for which I have no time in this blog if I am to keep it to a reasonable length. The bottom line in my head is that we (clean energy advocates, environmentalists) have to do a better job of educating the public about the long-term advantages of a clean energy society (including jobs) and elect representatives in both the House and Senate who ‘get it’ and feel the pressure from home to move us more rapidly in this direction. Ultimately, politicians understand the power of the ballot box if they understand nothing else. One of our tasks is to use that power effectively.

Energy Efficiency – The Necessary Cornerstone of U.S. Energy Policy

So far in this blog I’ve focused mostly on energy supply, with only a few references to limiting energy demand. I intend to correct this imbalance by now discussing, in more detail, energy efficiency, the wise use of whatever energy supplies we have, and the reasons I believe energy efficiency should be the cornerstone of U.S. energy policy. I will do so in the context of talking about energy security.

A search of the literature reveals that no precise definition exists for energy security. My approach to addressing this topic is to start by recognizing that energy is a means to an end, not an end in itself (except perhaps to those who sell energy or fuels). Fundamentally, energy is important only as its use facilitates the provision of services that are important to human welfare. These energy services include heating, cooling, lighting, communication, transporting people and goods, commercial activities, and industrial processes.

It is often said that energy is the lifeblood of modern societies, but the use of energy in its various forms, particularly fire, has been critical to human activities over the centuries and has helped shape human society. What is true is that modern societies provide a high level of energy-dependent services to their members and are totally dependent on energy sources that go well beyond human and animal power.

In the 20th century population growth, increasing urbanization, and increasing human welfare led to a rapid rise in electrification and dramatically increased global energy demand.

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Transportation proved to be the fastest growing consumer of energy supplies, with well over 90 percent of transportation energy needs provided by petroleum. This pattern is continuing in the 21st century.

Projections by the International Energy Agency, the European Commission, the World Energy Council, the US Energy Information Administration, and others all point to the same general conclusions: there will be increased consumption of all primary energy sources over the next several decades. Specifically, the US Department of Energy’s Energy Information Administration, in its International Energy Outlook 2013, projects that, under business-as-usual, total world energy demand will rise from just under 600 Quads (1 Quad = 1.055 Exajoules) today to just over 800 Quads in 2040. Most of this growth will take place in the developing world.

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These projections mask a central issue: How urgent is it to reduce growth in global energy demand and related emissions of carbon dioxide, other greenhouse gases, and other pollutants? I believe there is an urgency in a world that is powered today mostly by fossil fuels (80%) and is in the obvious early stages of human-induced global warming and climate change that is now irreversible even if carbon emissions were reduced to zero tomorrow. These impacts include deep ocean and ocean surface heating, more intense storms, glacier melting, rising ocean levels, changes in land temperatures and precipitation patterns, and movement of disease vectors to new regions. A sad corollary is that nations and island locations that had little to nothing to do with creating global warming may end end up suffering its most severe consequences.

The ‘good news’ is that limiting energy demand through increased energy efficiency is in most cases the lowest hanging fruit to be harvested in our struggle to balance energy demand with supply while ensuring that people suffering from energy poverty are being provided needed services. Considerable literature exists on how we can make more efficient use of energy in buildings (insulation, more efficient appliances and lighting, ground source heat pumps, passive solar design), transportation (more fuel efficient cars, trucks ans aircraft, alternative fuels, increased use of public transportation), and industry (more efficient manufacturing technologies). What was once wasted, when energy costs were lower and less attention was paid to energy use, can now be seen as a resource to be mined.

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In light of the above I conclude that energy security must rest on two principles: (1) using the least amount of energy to provide a given service, and (2) access to technologies providing a diverse supply of reliable, affordable, and environmentally benign energy. The implications for energy policy are also twofold: (1) priority #1 must be the wise, efficient use of whatever energy supplies are available, whether fossil, nuclear, or renewable, and (2) then, and in parallel with increased efficiency, focus on new energy supplies that meet cost, sustainability and environmental requirements.

The clear message is that energy efficiency, the wise use of energy, must be the cornerstone of national energy policies.

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