NH3: The Molecular Battery
energywhiz | On 02, Oct 2013
LEVELING THE GRID
Donald Sadoway pointed out in his compelling TED talk that electricity supply must try to be in constant balance with electricity demand in order for the electrical grid system to work optimally. This dynamic is often referred to as “grid leveling” or “load leveling.”
The average person may not realize that every electron produced from burning coal or natural gas in centralized power plants, or water pouring through hydroelectric dams, or the rotation of wind turbines, or the sun’s rays falling on solar panels must be used directly. That is, right after the electron is created. Or it goes to waste. Conversely, if demand for electricity spikes, electricity producers must be able to instantaneously ramp up energy production quickly enough to distribute enough electrons to satisfy every lamp, microwave, air conditioner or electric car clamoring for it.
Battery technologies could do it. But they have to be really BIG and reliable batteries (or massive arrays of smaller batteries working together). And they have to be cheap in order to be cost effective, as grid-leveling demands. In fact, Sadoway and his recently launched company Ambri are working on this battery challenge, as are companies like Eos and others. But there’s a solution already already available. Already cheap.
MOLECULES AS BATTERIES
What if we had a molecule that could be created from adding electricity to a mixture of abundant and cheap raw materials, and that could at a later time easily and cleanly combusted to produce electricity? Not a battery in the most common reference to the term, where rare materials are frequently required, and even more frequently involve hard to dispose poisonous chemicals to manufacture energy storage devices large and small; but an energy storage mechanism nonetheless. What if instead there was a more basic way to manufacture a material directly from excess or unused electrical energy, or from electricity produced specifically to create these molecules and store them for later combustion to create electricity on-demand?
It turns out that there are ways to do this, but most of them aren’t all that clean. There are active programs developing what is called “power-to-gas” technology, which convert electric power into liquid or gas fuel that can be burned at a later time for on-demand electricity production; but they principally focus on using carbon dioxide and water to produce methane (so called “natural gas”), and then burn the methane in generators much like we already do in natural-gas-fired power planets. While one can see the potential efficiencies in reclaiming CO2 produced via other carbon-cycle combustion and using it in power-to-gas energy storage schemes, that route perpetuates many of the pollution and greenhouse-gas problems of carbon-based fuels.
CAN NH3 SET US FREE?
NH3 is the chemical composition of “anhydrous ammonia.” The “anhydrous” bit means there is no water in it (like we get in highly water-diluted household ammonia products). Anhydrous ammonia is widely used commercially worldwide, principally as an agricultural fertilizer, refrigerant, and in the manufacture of commercial explosives and pharmaceuticals.
It turns out there is also some precedent in using anhydrous ammonia as a fuel for power generation. Chuck Yeager’s aircraft was fired by NH3 fuel during his historical breaking of the sound barrier. And in World War II when diesel and gasoline were in short supply, some enterprising Europeans modified their trucks and cars to run off the plentiful substance.
Ammonia’s energy density is something like 1/2 of that of diesel fuel. That means if you used NH3 to power a car or truck, you’d get about half the distance driving on a similar sized tank of the respective substances.
NH3 at normal pressures and temperatures is a gas, though it takes only a bit of pressure to condense it into a liquid– about 200psi, which is similar to propane. The “N” stands for Nitrogen, and the “H3″ stands for three Hydrogen molecules. Notice there isn’t a “C” (Carbon) to be found in the chemical equation for ammonia. Burning NH3 produces zero carbon, zero greenhouse gasses, zero hazardous substance. Combusted correctly, the bi-products of the combustion of NH3 are only Nitrogen and Water (H2O). While it is a bit trickier to handle than gasoline or diesel, it is as pure and sustainable a combustible fuel as one can find in terms of emissions.
By almost any measure NH3 is an excellent energy storage medium, and we already have pervasive infrastructure for, and understanding of how to handle it. The global industrial production of ammonia for 2012 was nearly 200 million tonnes, and the market research institute Ceresana is forecasting the global ammonia market to generate revenues of approx. US$102 billion in 2019. It is reportedly the third most transported commodity in the United States.
PRODUCING A SUSTAINABLE MOLECULAR BATTERY
NH3 for any of its applications is classically produced by a method called the Haber-Bosch Process that dates back to 1910. The process requires a source of electricity, a source of Nitrogen (typically just ambient air, composed of around 80% Nitrogen), and a source of Hydrogen.
The source the hydrogen has most commonly been methane (CH4, one part Carbon, four parts Hydrogen, also called “Natural Gas”) and gasified coal (that releases the H in complex coal molecules). The amount of natural gas needed for one day’s production of ammonia at an average-scale plant would heat 850 to 1,700 homes for a month during a typical northeastern United States winter; and for every metric tonne of ammonia produced in the Haber-Bosch process, some 1.8 metric tonnes of CO2 is produced into the atmosphere—so nearly twice as much greenhouse gases are produced than ammonia via Haber-Bosch!
The electricity needed for the Haber-Bosch process can also be generated from carbon-based sources (like coal or methane power plants), but can also be generated from renewable sources like wind, solar, hydro, geothermal or tidal.
Given we know that ammonia burns absolutely cleanly, what is most important for using ammonia as a renewable energy storage medium the sustainable economics regarding from where the necessary “H” (Hydrogen) comes, and from where the electricity comes to fuel the NH3 production process.
Whether produced from renewable energy or from carbon-based sources, there is significant waste and inefficiency already in production and distribution through national electricity grid. Simply storing those orphaned electrons in the form of combustible NH3 for a rainy day is both noble and profitable. And doing it sustainably and renewably promises even more profitability and nobility.
Further, it turns out that the Hydrogen needed for ammonia production can be produced via methods different from the Haber-Bosch process (which as stated uses dirty carbon-based sources as a source of H). One of those methods is through “cracking” water (H20), producing two parts hydrogen to be used in ammonia production and one part harmless oxygen byproduct, which itself can be sold for other applications.
The cracking is generally done using a procedure called electrolysis, where the application of direct electrical current in specific configurations causes the segmentation of the two different atomic elements. All electrolytic converter systems need in order to produce NH3 is a bit of electricity, regular air, and a source of water. Clean as a whistle.
Producing ammonia using H from carbon-free sources (i.e. H2O) and using carbon-free generation of electricity in the production process is called Green NH3. The same Green NH3 classification is frequently assigned to NH3 production that uses clean H sources (the same H2O) and any source of electricity—carbon-based or renewable.
THE ECONOMICS OF NH3
So why isn’t all NH3 produced using the electrolytic process? And why haven’t we been using NH3 as a fuel? Simple: economics.
There are two particular ways the economics of producing NH3 from surplus electricity generation could make sense:
- To sell on the existing markets for commercial ammonia applications
- For time-shifting stranded or surplus power generation—a clean form of energy-to-gas conversion.
Selling to the Market for Existing Commercial Applications
Using unused electricity from any existing power generation plant to produce anhydrous ammonia and sell it for agricultural or other commercial uses makes excellent economic sense if it can compete with purpose-built ammonia generation plants (who simply pay their massive electric bills accreted from normal operations).
Some data from a Hydroworld analysis:
Using the standard electrolytic ammonia approach consisting of electrolyzers, air separation equipment, and Haber-Bosch synthesis (the EHB approach [electrolysis supplying H to Haber-Bosch process]), energy consumption to produce a metric ton of ammonia has historically been about 12 megawatt-hours. Thus, the “fuel cost” [i.e. electricity for NH3 production] alone of making that metric ton of ammonia would be $600 at 5 cents per kilowatt-hour. Add in capital and operating expenses, and that metric ton of ammonia costs about $800 to make. Compare that to ammonia produced from natural gas [instead of water]. For much of the past 100 years, the cost of a million Btu of natural gas, even in the U.S., has not been much higher than US$1. Based on the number of 33 million Btu for a metric ton of NH3, the fuel cost for a metric ton of ammonia from natural gas that costs $1 per million Btu has been $30 to $40, compared to $600 for EHB ammonia. There was no way for electrolytic ammonia to compete economically.
So using the hybrid process of electrolysis to produce H for the Haber-Bosch process is somewhere in the neighborhood of $800 per metric ton; and using the H-B Process and carbon sources of H have been more like $50 per metric ton. That is, historically the carbon-based supply of H has been some 15x less expensive to use in the production of NH3.
However, institutions like Texas Tech University, Korea Institute of Energy Research and Nottingham University; and companies like ITM Power, NH3 Canada and NHThree have made significant advancements our ability to “crack” water as a economical source of Hydrogen for NH3 production, and move the needle significantly lower in the costs.
With rising competition and demand in production and distribution NH3 for commercial use, and commensurate rising costs, more recent numbers indicate that pure electrolytic Green NH3 production using improved electrolysis stack technologies, and new technologies like Solid State Ammonia Synthesis (SSAS), Green NH3 production is already on-par or besting traditional NH3 production, and indisputably so when external costs are taken into account.
Producing Ammonia for Grid-Leveling and Energy-to-Gas Strategies
Unlike biofuels, where frequently crops like corn are being used for ethanol production and thus effectively creating competing economics between food and energy, ammonia production for energy use and grid-leveling can be considered completely separately from ammonia production for other commercial uses (like agriculture fertilizer).
While there is a capital cost to instituting NH3 production and storage at sources of surplus electricity, and adapting generators to combust NH3, the electricity is essentially free, as is the source of air and water. That is, the focus is on using surplus electricity and storing it for later combustion and energy production during high peak loads.
There are tens of billions of dollars lost each year in Transmission and Distribution market inefficiencies, and stranded energy production. That is, more energy is produced than used, energy isn’t plentiful enough in high-demand periods, and energy is produced in places remote to a grid. There is overwhelming evidence that we are now at a tipping point where the entire process of creating, distributing and combusting anhydrous ammonia has become massively scalable, distributable and economically viable, particularly for industrial scale applications like grid-load-leveling.
GRID LEVELING vs. VEHICULAR FUEL
It is a fact that anhydrous ammonia in high concentration is harmful to organic life. It reacts with water moisture when released as a gas. Surfaces like skin, eyes and lungs are tasty targets for the gas, which can chemical burns if they come in contact. But the human organism has developed a very sensitive early-warning system for ammonia. Anyone who has experienced the pungent aroma of ammonia gas will be pleased to know that we humans can detect infinitesimal amounts– as small as 5 to 20ppm (parts-per-million)– when at least 100-times that is required before there is a threat to human physical safety.
Still, the global economy has sorted out how to produce and move millions of metric tonnes of it around the world safely every year.
Logical and justifiable or not, for motor vehicle applications we can easily imagine the objections to hundreds of millions of cars and trucks running around highways and city streets with “poisonous gas tanks”. Even though anhydrous ammonia moves through our streets every day in massive quantities, and storage technologies are already sophisticatedly safe and ever-improving, it will take time and technology to lower the perceptual barrier of the populace around NH3 as a vehicle fuel.
But not so for grid leveling and large-scale energy storage. On farms large and small, industrial complexes, military bases, power plants, solar farms, wind farms and more—producing NH3 in quantity from either clean or dirty energy production sources, and storing it in quantity for a rainy day (or simply an hour of peak air conditioning usage) makes good economic sense. It means we use less carbon-based fuels over time, and it means we mitigate the commonly quoted “issue” with some renewables—the sun doesn’t shine 24 hours a day, the wind doesn’t blow all the time.
DISTRIBUTED PRODUCTION = PRODUCE and COMBUST ANYWHERE
Combustible anhydrous ammonia can be produced anywhere there is a source of electricity and a source of water. It is inherently a “distributed production” fuel source, and the production-combustion cycle for Green NH3 is virtuous.
H20 (Water) + N (Air) + Electricity (Wind/Solar/etc) -> COMBUST -> N (Air) + H20 (Water)
Neither the materials to produce or the byproducts from combustion are poisonous. While the produced material requires special handling, the methods for doing so are highly evolved and improve yearly. And the combustion byproducts are not radioactive, contain no greenhouse gases, and don’t have a deleterious affect localized environment (razing or drilling into local lands), and doesn’t adversely affect global environment (contribute to alleged climate change).
Every electron generated via energy production large and small (but especially large) can be stored in NH3 molecules, and then later combusted in NH3 economically adapted generators (or purpose-built NH3 generators).
NH3 has the potential to create massive improvements in the efficiencies of both renewable energy facilities and carbon-fueled power plants. At almost any price, the model of produce-anywhere/combust-anywhere is inherently more productive and efficient than the carbon-based models of destructive-production, massive carbon footprint in distribution, and destructive-and-dirty combustion. It just turns out that the NH3-as-fuel cycle is cost-competitive, and the economics continue to benefit from technological advancements and world economics. It only gets better from here on in.