Category: Energy storage

Looking Ahead 30-40 Years – A Risky Business

History has always been my favorite subject, starting in high school, and still constitutes a major part of my personal reading. Needless to say I have a strong interest in other topics as well, as attested to by my long career in science and engineering and education/mentoring activities with young people. What often fascinates me is looking back at how things have changed in the past, often in unexpected ways, and how people looking back in the decades ahead will put their perspectives on what we are doing today. This blog post is my attempt to flesh out these thoughts, while acknowledging the difficulty of looking into the future. If I look far enough into that future I will not be around to suffer the slings and arrows of projecting incorrectly, or collecting the kudos for projecting accurately. Nevertheless, it feels like a stimulating and challenging activity to undertake, and so here goes.

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Let me start by going back seven decades to the 1940s when I was a young kid growing up in the Bronx and just beginning to form my likes and dislikes and develop opinions. My love for science fiction developed at that time and was probably a dead give-away of my future career interests. An important shaping event was the dropping of the first atomic bomb on Japan on August 6, 1945, an event that I still clearly remember learning about on the radio while sitting in the back seat of my parents’ car. Without a deep or much of any understanding at that time, I somehow sensed that the world had changed in that August moment. I still feel that way after many subsequent years of reading and studying.

The following decades saw several other unexpected and defining events: the addition of fusion weapons (hydrogen bombs) to our nuclear arsenals, commercial applications of controlled nuclear fission (nuclear submarines and nuclear-powered surface ships, and the first commercial nuclear power plant which was actually a land-based nuclear submarine power plant), development and emergence of the transistor as a replacement for vacuum tubes (first using germanium and then silicon), the development of the first solar cell at Bell Labs, the development and application of laser technology, the emergence of the information technology industry based on the heretofore abstract concepts of Boolean algebra (0s and 1s), and the increasing attention to a wide range of clean energy technologies that had previously been considered impractical for wide scale application – wind, solar, geothermal, ocean energy, fuel cells, advanced battery technologies, and a broad range of alternative liquid and gaseous fuels. Each in its own way has already changed and will further change the world in future decades, as will other technologies that we now only speculate about or cannot imagine. This is the lesson of history – it is difficult for most of us to look ahead and successfully imagine the future, and one of my earlier blog posts (‘Anticipating the Future: It Can Be Difficult’) discusses this topic. In the following paragraphs I speculate about the future with humility but also great anticipation. My only regret is that I will not live long enough to see most of this future unfold.

I will divide this discussion into two parts on which I have focused some attention and feel that I have some knowledge – medicine/health care, and energy. That leaves all too many aspects of the future that I don’t feel qualified to comment upon – e.g., what more will we learn about Amelia Earhart’s disappearance, Cuba’s possible participation in John Kennedy’s assassination, and the future of the tumultuous Middle East and the countries of the former Soviet Union. My primary focus in this post will be on the latter of the two parts, energy.

To help you understand my interest in medicine and health care I confess that at one point in my career, before committing to pursuing a PhD in physics, I gave serious consideration to attending medical school. During this period in the early 1960s I was a research scientist at Texas Instruments (TI) and was excited about the possibilities of miniature electronics which TI was pioneering in. I even suggested to my TI bosses that we undertake the application of transistors and sensors to artificial vision, but it was much too early for the company to make such a commitment. Today, 50 years later, that vision is being realized.

I also see great promise in the application of miniature electronics to continuous in-vivo diagnosis of human health via capsules that float throughout a human’s blood network, monitor various chemical components, and broadcast the results to external receivers. This will depend on low-powered miniature sensors and analysis/broadcast capability powered by long-lasting miniature batteries or an electrical system powered by the human body itself. Early versions are now being developed and I see no long-term barriers to developing such a system.

A third area in which I see great promise is the non-invasive monitoring of brain activity. This is a research area that I see opening up in the 21st century as we are beginning to have the sensitive tools necessary to explore the brain in detail. Given that the brain is responsible for so many aspects of our mental and physical health I expect great strides in the coming decades in using brain monitoring to address these issues.

The energy area is where I have devoted the bulk of my professional career and where my credibility may be highest – at least I’d like to think so. Previous blog posts address my thoughts on a wide range of current energy, water-energy, and related policy issues. Recognizing that changes in our energy systems come slowly over decades and sometimes unexpectedly, as history tells us, I will share my current thoughts on where I anticipate we will be in 30-40 years.

Let me start with renewable energy – i.e., solar, wind, hydropower, geothermal, biomass, and ocean energy. I have commented on each of these previously, but not from a 30-40 year perspective. Renewables are not new but, except for hydropower, their entering or beginning to enter the energy mainstream is a relatively recent phenomenon. Solar in the form of photovoltaics (PV) is a truly transformative technology and today is the fastest growing energy source in the world, even more so than wind. This is due to significant cost reductions for solar panels in recent years, PV’s suitability for distributed generation, its ease and quickness of installation, and its easy scalability. As soon as PV balance-of-system costs (labor, support structures, permitting, wiring) come down from current levels and approach PV cell costs of about $0.5-0.7 per peak watt I expect this technology to be widespread on all continents and in all developed and developing countries. Germany, not a very sunny country but the country with the most PV installed to date, has even had occasional summer days when half its electricity was supplied by solar. In combination with energy storage to address its variability, I see PV powering a major revolution in the electric utility sector as utilities recognize that their current business models are becoming outdated. This is already happening in Germany where electric utilities are now moving rapidly into the solar business. In terms of the future, I would not be surprised if solar PV is built into all new residential and commercial buildings within a few decades, backed up by battery or flywheel storage (or even hydrogen for use in fuel cells as the ultimate storage medium). Most buildings will still be connected to the grid as a backup, but a significant fraction of domestic electricity (30-40%) could be solar-derived by 2050. The viability of this projection is supported by the NREL June 2012 study entitled ‘Renewable Electricity Futures Study’.

Hydropower already contributes about 10% of U.S. electricity and I anticipate will grow somewhat in future decades as more low-head hydro sites are developed.

For many years onshore wind was the fastest growing renewable electricity source until overtaken recently by PV. It is still growing rapidly and will be enhanced by offshore wind which currently is growing slowly. However, I expect offshore wind to grow rapidly as we approach mid-century as costs are reduced for two primary reasons: it taps into an incredibly large energy resource off the coasts of many countries, and it is in close proximity to coastal cities where much of the world’s population is increasingly concentrated. In my opinion, wind, together with solar and hydro, will contribute 50-60% of U.S. electricity in 2050.

Other renewable electric technologies will contribute as well, but in smaller amounts. Hot dry rock geothermal wells (now called enhanced geothermal systems) will compete with and perhaps come to dominate traditional geothermal generation, but this will take time. Wave and tidal energy will be developed and become more cost effective in specific geographical locations, with the potential to contribute more in the latter part of the century. This is especially true of wave energy which taps into a large and nearly continuous energy source.

Biomass in the form of wood is an old renewable energy source, but in modern times biomass gasification and conversion to alternative liquid fuels is opening up new vistas for widescale use of biomass as costs come down. By mid-century I expect electrification and biomass-based fuels to replace our current heavy dependence on petroleum-based fuels for transportation. This trend is already underway and may be nearly complete in the U.S. by 2050. Biomass-based chemical feedstocks will also be widely used, signifying the beginning of the end of the petroleum era.

I expect that other fossil fuels, coal and natural gas, will still be used widely in the next few decades, given large global resources. Natural gas, as a cleaner burning fossil fuel, and with the availability of large amounts via fracking, will gradually replace coal in power plants and could represent 30-40% of U.S. power generation by mid-century with coal generation disappearing.

To this point I have not discussed nuclear power, which today provides close to 20% of U.S. electricity. While I believe that safe nuclear power plants can be built today –i.e., no meltdowns – cost, permanent waste storage, and weapons proliferation concerns are all slowing nuclear’s progress in the U.S. Given the availability of relatively low-cost natural gas for at least several decades (I believe fracking will be with us for a while), the anticipated rapid growth of renewable electricity, and the risks of nuclear power, I see limited enthusiasm for its growth in the decades ahead. In fact I would not be surprised to see nuclear power supplying only about 10% of U.S. electricity by 2050, and less in the future.

To summarize, my picture today of an increased amount of U.S. electricity generation in 2050 is as follows:

Generating Technology : Percent of U.S. Generation in 2050
nuclear: 5-10
coal: 0-5
Oil: 0
natural gas: 30-40
solar + wind + hydro: 50-60
other renewables: 5-10

I am sure that some readers of this post will take strong issue with my projections and have very different thoughts about the future. I welcome their thoughts and invite them to join me in looking ahead. As the title of this post acknowledges, looking ahead is risky business, but it is something I’ve wanted to do for a while. This seems as good a time as any to do so.

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Thoughts On U.S. Energy Policy – Updated

In October 2008, just prior to the U.S. presidential election, I drafted a piece entitled ‘Thoughts on an Energy Policy for the New Aministration’. It was published about a month later and republished as my first blog post in May 2013. I said at that time “What I find interesting about this piece is that I could have written it today and not changed too many words, an indication that our country is still struggling to define an energy policy.” This post is my attempt to look back at what I said in 2008 and 2013 and see if my perspectives and views have changed.

In that piece I started off by listing 14 items that I labeled as ‘facts’ on which most can agree. These ‘facts’ are reproduced below, followed by my comments on what may have changed since 2008.

1. People do not value energy, they value the services it makes possible – heating, cooling, transportation, etc. It is in society’s interest to provide these services with the least energy possible, to minimize adverse economic, environmental and national security impacts.

2. Energy has always been critical to human activities, but what differentiates modern societies is the energy required to provide increasingly high levels of services.

3. Population and per capita consumption increases will drive increasing global energy demand in the 21st century. While not preordained, this increase will be large even if others do not achieve U.S. per capita levels of consumption.

4. Electrification increased dramatically in the 20th century and will increase in the 21st century as well. The substitution of electricity for liquid transportation fuels will be a major driver of this continued electrification.

5. Transportation is the fastest growing global energy consumer, and today more than 90% of transportation is powered by petroleum-derived fuels.

6. Globally energy is not in short supply – e.g., the sun pours 6 million quads of radiation annually into our atmosphere (global energy use: 460 quads). There is considerable energy under our feet, in the form of hot water and rock heated by radioactive decay in the earth’s core. What is in short supply is inexpensive energy that people are willing to pay for.

7. Today’s world is powered largely by fossil fuels and this will continue well into the 21st century, given large reserves and devoted infrastructure.

8. Fossil fuel resources are finite and their use will eventually have to be restricted. Cost increases and volatility, already occurring, are likely to limit their use before resource restrictions become dominant.

9. Increasing geographic concentration of traditional fossil fuel supplies in other countries raises national security concerns.

10. The world’s energy infrastructure is highly vulnerable to natural disasters, terrorist attacks and other breakdopwns.

11. Energy imports, a major drain on U.S. financial resources, allow other countries to exert undue influence on U.S. foreign policy and freedom of action.

12. Fossil fuel combustion releases CO2 into the atmosphere (unless captured and sequestered) which mixes globally with a long atmospheric lifetime. Most climate scientists believe increasing CO2 concentrations alter earth’s energy balance with the sun, contributing to global warming.

13. Nuclear power, a non-CO2 emitting energy source, has significant future potential but its widespread deployment faces several critical issues: cost, plant safety, waste storage, and weapons non-proliferation.

14. Renewable energy (solar, wind, biomass, geothermal, ocean) has significant potential for replacing our current fossil fuel based energy system. The transition will take time but we must quickly get on this path.”

What has changed in my opinion are items 9, 11, and 12. The availability of large amounts of home-grown natural gas and oil at competitive prices via hydraulic fracturing (fracking) of shale deposits has turned the U.S. energy picture upside down. It may do that in other countries as well. Whereas the U.S. was importing over 50% of its oil just a few years ago, that fraction is now under 40% and the U.S. is within sight of becoming the largest oil producer in the world, ahead of Russia and Saudi Arabia. Whereas in recent years the U.S. was building port facilities for the import of LNG (liquified natural gas) these sites are being converted into LNG export facilities due to the glut of shale gas released via fracking and the large potential markets for U.S. gas in Europe and Asia (where prices are higher than in the U.S.).

The phenomena of global warming and climate change due to mankind’s combustion of carbon-rich fossil fuels are also becoming better understood, climate change deniers have become less and less visible, and the specific impacts of climate change on weather and water are being actively researched. An important change is the substitution of natural gas for coal in new and existing power plants, which has reduced the share of coal from 50% just a few years ago to less than 40% today. This has reduced U.S. demand for domestic coal, which is now increasingly being sold overseas.

The second part of the 2008 article was a set of 10 recommendations that are reproduced below:

1. Using the bully pulpit, educate the public about energy realities and implications for energy, economic and environmental security.

2. Work with Congress to establish energy efficiency as the cornerstone of national energy policy.

3. Work with Congress to provide an economic environment that supports investments in energy efficiency, including appropriate performance standards and incentives, and setting a long-term, steadily increasing, predictable price on carbon emissions (in coordination with other countries). This will unleash innovation and create new jobs.

4. Consider setting a floor under oil prices, to insure that energy investments are not undermined by falling prices, and using resulting revenues to address equity and other needs.

5. Work with Congress to find an acceptable answer to domestic radioactive waste storage, and with other nations to address nuclear power plant safety issues and establish an international regime for ensuring nonproliferation.

6. Establish a national policy for net metering, to remove barriers to widespread deployment of renewable energy systems.

7. Provide incentives to encourage manufacture and deployment of renewable energy systems that are sufficiently long for markets to develop adequately but are time limited with a non-disruptive phaseout.

8. Aggressively support establishment of a smart national electrical grid, to facilitate use of renewable electricity anywhere in the country and mitigate, with energy storage, the effects of intermittency.

9. Support an aggressive effort on carbon capture and sequestration, to ascertain its feasibility to allow continued use of our extensive coal resources.

10. Remove incentives for fossil fuels that are historical tax code legacies that slow the transition to a new, renewables-based, energy system.

I still support these recommendations, buttressed by the following observations:

– more public education on global warming and climate change has taken place in recent years, and a majority of Americans now accept that global warming is driven by human activities.

– there is a lot of lip service given to the need for increased energy efficiency, and President Obama’s agreement with the auto industry to increase Corporate Average Fuel Economy (CAFE) standards over the next decade is an important step forward. What is lacking, and slowing needed progress toward greater efficiency, is a clear policy statement from the U.S. Congress that identifies and supports energy efficiency as a national priority.

– with the shutting down of the Yucca Mountain long-term radioactive waste storage facility in Nevada, the Obama Administration is searching for alternatives but believes the country has time to come up with a better answer. This may be true, or may not, and only time will tell. It is not a uniquely American problem – other countries are struggling with this issue as well and most seem to favor deep geological storage. This is a problem we will definitely be handing down to our children and grandchildren,

– net metering as a national policy, as is true in several other developed countries, has gone nowhere in the six years since 2008. It is another example of a lack of Congressional leadership in establishing a forward-looking national energy policy.

– progress has been made on moving renewable energy into the energy mainstream, but we have a long way to go. NREL’s June 2012 report entitled ‘Renewable Electricity Futures Study’ made it clear that renewables could supply 80% of U.S. electricity by 2050 if we have the political will and make appropriate investments. The study puts to rest the argument used by the coal and other traditional energy industries that renewables can’t do the job. The public needs to understand that this canard is inaccurate and not in our country’s long term interests.

– the need for a national grid, and localized mini-grids (e.g., on military bases), has been recognized and appropriate investments are bring made to improve this situation. A national smart grid, together with energy storage, are needed to assure maximum utilization of variable clean energy sources such as wind and solar. Other renewable energy sources (geothermal, biomass, hydropower, ocean energy) can be operated as baseload or near base load capacity. And even intermittent wind and solar can supply large amounts of our electricity demand as long as we can transfer power via the national grid and use averaging of these resources over large geographical areas (if the wind isn’t blowing in X it probably is blowing in Y).

– the carbon capture and sequestration effort does not seem to be making much progress, at least as reported in the press. My blog post entitled ‘Carbon Capture and Sequestration: Is It a Viable Technology?’ discusses this issue in some detail.

– with respect to reducing long-standing and continuing subsidies for fossil fuel production, no progress has been made. Despite President Obama’s call for reducing or eliminating these subsidies the Congress has failed to act and is not likely to in the near-term future. This is a serious mistake as these industries are highly profitable and don’t need the subsidies which divert public funds from incentivizing clean energy technologies that are critical to the country’s and the world’s energy future.

– today’s electric utility sector is facing an existential threat that was not highly visible just a few years ago. This threat is to the utility sector’s 100 year old business model that is based on generation from large, centralized power plants distributing their energy via a radial transmission and distribution network. With the emergence of low-cost decentralized generating technologies such as photovoltaics (PV), these business models will have to change, which has happened in Germany and will eventually happen in the U.S. Keep tuned as this revolution unfolds.

As a final word I repeat what I have said in earlier posts: we need to put a long-term, steadily increasing price on carbon emissions that will unleash private sector innovation and generate revenues for investments in America’s future. This is a critical need if we are to successfully address climate change, create new U.S. jobs in the emerging clean energy industry, and set an example for the world.

Energy Storage: A Critical Link In the Renewable Energy Chain

An issue that has always grabbed my attention is the critical role I and others foresee for energy storage in the eventual widespread use of variable (intermittent) renewable energy sources such as wind and solar. In fact it was the focus of my first decision when I assumed responsibility for DOE’s renewable electricity programs in 1994. That decision was to establish a comprehensive storage program to complement the established generation programs – up until that point the only storage program was a small effort on underground hot water storage at a university in South Carolina (no doubt related to the fact that the Chairman of the relevant budget authorization subcommittee was from South Carolina). The new program, in addition to thermal storage, added battery storage and superconducting magnetic energy storage (SMES) – superconductivity was another of the programs I managed.

Energy storage is one of two critical renewable energy issues that I have always said I would ‘fall on my sword for’. The second is the need for a national smart grid that will allow renewable electricity generated in one part of the country to be shared with other parts. I have touched briefly on the energy storage topic in earlier blog posts; this post takes a much more detailed look at various storage options.

The need for storage to steady the output from a variable energy source is not new. In fact, in December 1861 the following words and illustration appeared in an agrarian newsletter:
“A Mighty Wind One of the great forces nature furnished to man without any expense, and in limitless abundance, is the power of the wind. Many efforts have been made to obtain a steady power from the wind by storing the surplus from when the wind is strong. One of the latest and simplest of these is illustrated in the accompanying engraving. A windwheel is employed to raise a quantity of iron balls, and then these balls are allowed to fall one by one into buckets upon one side of a wheel, causing the wheel to rotate, and thus to drive the machine.”

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If one substitutes water for the iron balls and attaches a generator to the rotating machine you have today’s system of pumped water storage and generation. A modern version of the 1861 system, using gravel instead of iron balls, is shown in the following sketch:

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Since the discovery of electricity generation using rotating coils of wire in magnetic fields by the British scientist Michael Faraday in 1820, people have sought ways to store that energy for use on demand. Without such storage, or use in some other way (e.g., to electrolyze water to create and store hydrogen, heat water, bricks or phase change materials that store heat , or refrigerate water to create ice) surplus electricity generation is lost. With modern societies increasingly dependent on energy services provided via use of electricity, the need for electricity storage technologies has become critical. This is especially true as more and more variable renewable energy enters the grid, to avoid grid destabilization. This can occur because electric power supply systems must balance supply and demand, and because demand is highly variable and hard to control the balancing is routinely achieved by controlling the output of power plant generators. If these generators are variable solar and wind, and their grid contribution becomes significant, achieving the balance is that much more difficult, and a means of stabilizing these variable outputs is needed.

There is also strong economic and social incentive for storing electricity in a localized, distributed manner. Today’s 100-year-old centralized utility business model, in which large central power plants deliver electricity to customers via transmission and distribution lines, includes the imposition of peak demand charges that can account for a significant fraction of a business’ or an individuals’ electricity bill. With the use of localized generation (e.g., PV panels on your roof), combined with storage at your site, these demand and peak charges can be reduced if not eliminated, and independence from the utility, to some degree, can be achieved. This reality is taking place in Germany (and coming to the U.S.) and threatening the utility business model in Germany to the extent that German utilities have gone into the solar-energy storage business. They now sell or lease or maintain roof-mounted PV and battery storage systems.

Today’s menu of devices that allow storage of surplus electricity for use at other times includes: solid state batteries and supercapacitors, flow batteries, flywheels, compressed air energy storage (CAES), and pumped hydropower. Hydrogen generated from any electricity source via electrolysis of water, and combusted or used in fuel cells, is, in many ways, the ultimate storage technology for surplus electricity. Flywheels, pumped storage, and fuel cells are discussed in earlier blog posts ; other storage technologies are discussed below.

Historically, electricity has been stored in lead-acid batteries, and this is still the dominant battery storage technology today in cars and elsewhere because of low cost, high power density, and high reliability. Disadvantages are low specific energy storage capacity, large size, high weight, and the need for an acid electrolyte. Lead is also a toxic material. Research to improve batteries has been underway for more than a century, and considerable progress has been made (e.g., improved lead-acid batteries that require no maintenance and recycling of used batteries to recover the lead), with considerable promise for further developments in the future.

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Most battery attention today is focused on lithium-ion batteries where cost and safety are prime concerns. Research into post lithium-ion batteries is also being actively pursued.
Lithium-ion batteries are widely used today because! “pound for pound they’re some of the most energetic rechargeable batteries available.” For example, it takes six kilograms of a lead-acid battery to store the same energy as one kilogram of a lithium-ion battery. Lithium-ion batteries (there is a variety of battery chemistries) also hold their charge well (losing about 5% per month), have no memory effect (therefore no need to fully discharge before recharging), can handle many hundreds of charge/discharge cycles, and have good ’round trip efficiency’. The story does have a negative side – lithium-ion batteries are sensitive to heat, can’t be fully discharged (thus requiring a computerized battery management system), are still costly (although costs are coming down), and certain chemical formulations can occasionally burst into flame if damaged or otherwise overstressed. One person making a big bet on lithium-ion batteries is Elon Musk, who has announced plans for a $5 billion battery factory, to provide lithium-ion batteries for his Tesla electric vehicles and other applications. Through such large scale production Musk hopes to reduce the cost of the batteries by 30 percent (to about $10,000 for a 60 kWh battery pack).

Supercapacitors store energy in electric fields and fill a gap between ordinary capacitors and rechargeable batteries. Their claim to fame is that they can be charged/discharged much more rapidly than batteries and can tolerate many more charge/discharge cycles. They are widely used as low current power sources for computer memories and in cars, buses, trains, cranes and elevators, including energy recovery from braking.

Redox (reduction/oxidation) flow batteries are large scale rechargeable energy storage systems that are on the verge of wide application in the electric utility sector. They are particularly well suited to storing large amounts of energy, e.g., the surplus energy created by hours of solar or wind power generation. The energy storage materials are liquids that are stored in separate tanks, and when energy is needed the liquids are pumped through a ‘stack’ where they interact to generate electricity. Many different chemical liquids have been tested for flow battery operation, with most current attention being focused on vanadium compounds which are expensive. Flow batteries also have relatively low round-trip efficiencies and response times. Because of the vanadium cost concern many other chemical possibilities are being evaluated.

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CAES (compressed air energy storage) utilizes surplus electricity to compress air to high pressures in large caverns, which can then be heated and released as needed to power expansion turbines that generate electricity. Such a CAES system has been operating successfully in Alabama since 1991, and gases other than air (e.g., carbon dioxide) can be used as well.

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SMES stores energy in the magnetic field of a circulating dc electrical current in a superconducting coil. The superconductor has no electrical resistance and the current continues indefinitely unless its energy is tapped by discharging the coil. A typical SMES device has two parts, a cryogenic cooler that cools the superconducting wire below its transition temperature at which it loses its electrical resistance, and power conditioning circuitry that allows for charging and discharging of the coil. Its advantages are ultra fast charge and discharge times, no moving parts, nearly unlimited cycling capability, and an energy recovery rate close to 100 percent. Disadvantages are cost of the wire, the need for continuous cooling, large area coils needed for appreciable energy storage, and the possibility of a sudden, large energy release if the wire’s superconducting state is lost. SMES devices are often used to provide grid stability in distribution systems and for power quality at manufacturing plants requiring ultra-clean power (e.g., microchip production lines). One MWh SMES units are now common and a twenty MWh engineering test model is being evaluated.

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To summarize, there are many energy storage options that work and tradeoffs are often required – e.g., among storage capacity, power capacity, round-trip efficiency, and most importantly cost. Lots of research is underway to reduce costs, given the large potential markets and the need to safely integrate variable renewable energy generation from solar and wind into the utility grid system. I have no doubt that cost-effective storage systems will soon be available, facilitating the needed rapid transition to a renewable electricity future.

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.”

Hydrogen and Fuel Cells: Important Parts of Our Energy Future?

Hydrogen is a simple atom/molecule and the most abundant element in the universe.

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As a physicist it is an an article of faith with me that mankind will eventually make large scale use of hydrogen as a fuel. As a realistic physicist I also acknowledge that such large scale use of hydrogen is a number of years away.

The device that will convert hydrogen into a major energy source is the fuel cell, which is an electrochemical device that combines hydrogen and oxygen to produce electricity, with water and heat as its by-product. First invented in the 19th century, today there is extensive research and a large and growing literature on fuel cells.

In its simplest form, a fuel cell consists of two electrodes – an anode and a cathode – with an electrolyte between them.

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When cells are stacked in series the output increases, resulting in fuel cells with power capacities ranging from several watts to several megawatts. A fuel cell system that includes a fuel reformer can obtain hydrogen from any hydrocarbon fuel such as natural gas, methanol, or gasoline. Since fuel cells rely on an electrochemical process and not combustion, emissions from fuel cells are significantly lower than emissions from even the cleanest fuel combustion processes. Fuel cells are also quiet, durable, and highly efficient. They are different from batteries in that they require a constant source of fuel and oxygen/air to sustain the chemical reaction; however, fuel cells can produce electricity continually for as long as these inputs are supplied.

My enthusiasm for hydrogen goes beyond my physics daydreaming: I often refer to it as the ultimate energy storage system. For example, what does a utility do with excess electricity generated by wind turbines at night when the wind is often strongest and consumer demand for electricity is lowest. The simple answer is to store it for delivery during the next day when demand and electricity prices are higher. Of course, storage is not energy- or cost-free, and still expensive today. My attraction to hydrogen is that excess electricity can be used to electrolyze a common substance (water) into hydrogen and oxygen and the hydrogen can be stored and used in fuel cells which transmit their generated electricity to consumers in many locations via power lines. No need to transport hydrogen via pipelines which are inherently expensive and often hard to site, and these pipelines have to be impervious to leakage by the tiny hydrogen molecule, unlike more standard fossil fuel pipelines. The kickers in this game are that water has to be available and the efficiency of electrolysis devices needs to be improved to reduce the cost of hydrogen production.

A fuel cell is a transformative technology that changes the way we generate and use electricity, a characteristic it shares with solar PV. It can be used in small and large sizes, in mobile and stationary applications, and has several technological foundations (proton exchange membrane, phosphoric acid, solid oxide). The hitch in fuel cells is cost reduction, a tough problem to address, and they’re competing as storage devices with lithium ion batteries which are steadily getting cheaper. Flywheels, when mass produced, may also offer some competition.

I’ve been following fuel cell development issues for almost forty years, since arriving in Washington, DC, and cost seems to be the major barrier to their large-scale use. Lots of effort is going into related research, including how to mass produce cheaply. The U.S. Department of Energy is supporting this effort both for mobile applications (i.e., cars) and larger stationary applications.

Considerable effort is also going into development of micro fuel cells that can be used to power cell phones, laptop computers and tablets – all of which can benefit from longer-lasting portable power supplies. These will probably be fueled by replaceable alcohol-water cartridges where the alcohol (ethanol/C2H5OH or methanol/CH3OH) supplies the needed hydrogen. For example, one mixture under investigation is 35% methanol in water. Such a micro fuel cell could provide ten hours of laptop time, although some computer tablets today achieve that goal. The reason for not going above 35% is that methanol interacts chemically with common anode and cathode materials and degrades the fuel cell. Nanotechnology may offer new material options, allowing this percentage to increase. An interesting aspect of alcohol use in micro fuel cells is that alcohol, being flammable, requires a waiver to be brought onto airplanes. Ethanol clearly has such a waiver as witnessed by drink service on most aircraft. Methanol only recently obtained such a waiver.

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