Is ammonia the holy grail for renewable energy storage?
New Orleans, 1871: "Ammoniacal Gas Engine" propelled streetcar, sketch by A. R. Waud, with subsidiary figures of woman holding baby, woman with parasol, and man wearing a hat. (Wikimedia Commons)
"If you want to beat carbon, it's the only way to do it unless you change the chemical charts." So says Jack Robertson about the prospects for making ammonia the world's go-to liquid fuel and renewable energy storage medium.
Robertson is chairman and CEO of Light Water Inc., an ammonia energy storage startup. The carbon he mentions refers, of course, to the major carbon-based fuels of oil, natural gas and coal that provide more than 80 percent of the world's energy. The charts he mentions refers to the periodic table of elements, a listing of the basic elements of the universe which are about as likely to change their properties as the proverbial leopard is to change his spots.
But the idea that ammonia can be used as a fuel, while not new, is not widely known. That's not really surprising since the last 150 years have been powered by another better-known liquid fuel called oil. And, the ubiquitousness and historically low price of oil prevented other liquid fuels from gaining a foothold in the marketplace. The use of historically cheap coal and natural gas has kept ammonia on the sidelines in the electricity market as well.
But now, two things have changed. First, concern about climate change has policymakers scrambling to figure out how to reduce carbon emissions. Second, the world's primary liquid fuel, oil, has been trading at its highest daily average price ever for the last three years. In 2011 the average daily price of Brent Crude, the world benchmark, was a record $111.26 a barrel--which was followed by another record in 2012 of $111.63. The year just finished saw Brent Crude a bit lower on average at $108.56, a figure higher than all but the two previous years.
(Despite all the hoopla about rising American crude production, the rate of oil production worldwide has eked out only a small gain of 2.7 percent between 2005 and 2012, about a quarter of the growth rate of the previous seven-year period. And, this slower growth in the face of rising demand in India and China has led to record prices.)
What makes ammonia so attractive as a fuel is sixfold. First, it contains no carbon. The ammonia molecule is composed of one atom of nitrogen and three atoms of hydrogen. Therefore, when ammonia-based fuel is burned, it produces no greenhouse gases. Second, we already have well-known processes for making ammonia. We don't need new or exotic technology to produce it. Third, these processes have long ago demonstrated that they can be scaled up to form a worldwide ammonia production industry. Fourth, an ammonia distribution system is already in place that includes rail tankers, tanker trucks, ships, barges and ammonia pipelines, a system that uses pressures no higher than that found in a bicycle tire to keep ammonia in its liquid state. While that infrastructure would need to be expanded, no new technology is required to transport ammonia from where it is made to where it is used.
Fifth, ammonia has an enviable safety record. There have been mishaps. But they don't involve fire since ammonia is not easily combustible. Those who've used ammonia cleaners will understand that it is the fumes which pose a danger if they are too concentrated. On the other hand, humans can detect the strong smell of ammonia at very low levels, long before it ever reaches toxic concentrations. And, this means that in the event of an accident, humans can flee or take measures to protect themselves from harm before it's too late.
Sixth, if manufactured using renewable energy, ammonia, when produced and then burned as a fuel, creates nothing that can be classed as pollution. When ammonia molecules are broken down into their constituent parts during separation and/or combustion, the nitrogen returns to the atmosphere and the hydrogen reacts with the oxygen in the air during combustion to form water.
Ammonia energy research is part of the hunt for a cheap method of storing intermittent flows of energy from wind and solar power generation, a major problem that has plagued the expansion of these low-carbon technologies. The wind, of course, doesn't always blow and the sun doesn't always shine. To make matters worse, when the wind blows most and the sun shines its brightest, sometimes too much electricity is produced and some of it must essentially be dumped. A similar problem plagues hydroelectric dams as I will explain below.
So, how exactly would ammonia be used for renewable energy storage? While others have been working on this problem, Robertson's story is instructive. After many years as an aide for the late U.S. Senator Mark Hatfield of Oregon, Robertson returned to Oregon to work for the Bonneville Power Administration (BPA) where he eventually rose to the rank of deputy administrator.
Each spring from his perch at BPA he watched enormous amounts of water run down the Columbia River, much of which would never generate electricity at the agency's hydroelectric dams because there was simply too much water. Even the electricity that was generated from the dams and later from the huge wind farms installed along the river would often be sold for almost nothing during the spring. Occasionally, the BPA actually had to pay others to take its excess electricity.
Robertson wondered if there might be some way to store all this excess power and then use it in other seasons when supply from the dams and wind farms was lower and electricity prices were higher.
After an early retirement he went to work on the problem in a more systematic way, first founding a nonprofit that studied the issue. One of the possible answers was to produce ammonia using the excess power. Robertson realized that in order to bring that idea to fruition he would need to raise private capital and formed Light Water Inc.--so named because the burning of hydrogen (after separation from the nitrogen atom in ammonia) produces light if used to generate electricity and also water as hydrogen combines with the oxygen in the air during combustion (as previously noted).
Robertson's aim is to produce "green" ammonia. By "green" he means produced using only renewable energy to separate hydrogen from oxygen in water molecules using electrolysis. (Ammonia is currently most often made using hydrogen stripped from methane or coal.) The "green" hydrogen would then be combined with nitrogen drawn from the air (which is 78 percent nitrogen) to form ammonia through the well-known and widely used Haber-Bosch process. The huge excess power available in spring from the BPA's system of dams and wind farms along the Columbia now doesn't have to be wasted, he believes. It could be used to make ammonia in quantities so large that the resulting volumes could even be shipped long distances to provide power and fuel for other parts of the country.
And, of course, wherever hydroelectric power and wind and solar energy are in large surplus at various times of the year (or in the case of wind and solar energy, various times of the day), ammonia-producing plants could be set up to store that excess energy for later use and/or shipment to other locales.
I've mentioned that the hydrogen in the ammonia molecule must be separated from the nitrogen so the hydrogen can be burned as fuel. (The harmless nitrogen simply returns to the atmosphere whence it came.) This can be done using well-known and widely used technology such as steam reforming (which is currently employed to strip hydrogen from methane molecules).
But, as it turns out, ammonia itself can be burned as a fuel if it is put under enough pressure. Robertson has combined his efforts with several others to seek funding from the California Energy Commission to test high-efficiency, high-compression engines fueled by ammonia as a way of producing electricity. (Such engines could, of course, be used to power vehicles as well though this is not the focus of Robertson's project.)
If the project is funded, a successful test could pave the way for private funding that would take the concept to the next step, a working pilot plant and then a commercial-scale plant that make ammonia and use it to generate electricity for utilities during peak load hours.
Robertson's project is but one example among many of experiments with ammonia as a fuel. The NH3 Fuel Association lists several efforts on its website.
The public has been previously tantalized by supposed energy breakthroughs such as ethanol and cold fusion--only to be disappointed when the results failed to match the hype or were nonexistent. But, the world already has long experience with ammonia, and so most of the questions surrounding its use, safety and scalability have already been answered--except one. Can it become a breakthrough alternative liquid fuel and storage medium for renewable energy?
The evidence so far suggests that it has a far better chance of succeeding than many of its current competitors.
New Orleans, 1871: "Ammoniacal Gas Engine" propelled streetcar, sketch by A. R. Waud, with subsidiary figures of woman holding baby, woman with parasol, and man wearing a hat.
Image added by Bart at Resilience
What do you think? Leave a comment below. See our commenting guidelines.
Sign up for regular Resilience bulletins direct to your email.