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Lou: You can't turn on the TV without seeing stories about alternative energy. In industry, the desire to lower carbon emissions has never been greater. In an earlier episode we spoke about a few fuel alternatives that are available today to those that desire to lower carbon emissions.
Lou: Today, I'm excited to take that conversation a step further into "Fuels of the Future". Let's take a look at fuels that are out on the distant horizon and what they might bring.
Lou: Returning via the Cat Electric Power Hotline for our conversation today is Hind Abi-Akar. Many of you may recognize Hind for not only our recent podcast on "Fuels of Today", but Hind was also a featured speaker at one of Caterpillar's 2020 webinars where she spoke about different fuels and their applications. Hind received her PhD in Materials Science from the University of Alabama and has been with Cat for 25 years. Hind is presently a Lubricants and Fuels Technical Expert.
Lou: Welcome Hind!
Hind: Thank you Lou for having me again on the Power Bytes podcast. It is an exciting and interesting time to be in the energy business with all the potential opportunities to make the world better and more sustainable.
Lou: Hind, with all this talk about reducing carbon emissions and carbon neutrality what do you see as some of the fuel possibilities?
Hind: This is an important question. We have discussed in a previous podcast the current alternative fuels, biodiesel, renewable diesel, and their blends, and we have been supporting our customers use these fuels for few decades now. Parallel to these efforts, we are working on several different classes of alternative fuels. Hydrogen, Methanol, Ammonia, DME (which is dimethyl ether) are probably the most often discussed and are in various levels of development.
Lou: Hind, I know Cat engines can blend hydrogen into our gas engines today. Why is Hydrogen on your list of future fuels?
Hind: Interest in hydrogen as a fuel has existed for a while (as early as WWI for self-sufficiency reasons) and has gained even more attraction lately.
Use of hydrogen as a transportation fuel has many challenges: low energy density, difficulty to store, and flammability and safety are major hurdles. Also, Pipeline transportation is complicated by hydrogen incompatibilities with some common materials such as hydrogen embrittlement of steel.
The attention to Hydrogen as an energy carrier that can be used to store, move, and deliver energy produced from other sources seems attractive.
As an example, when solar or wind renewable power sources are overproducing such as on sunny or windy days, one way to store the extra power produced is to generate hydrogen. Basically, the extra power can be used for water electrolysis and the hydrogen produced can be stored and can be used a carbon free fuel or zero greenhouse gas fuel
Lou: That's very interesting Hind. Is there work going on to better understand how to transport hydrogen?
Hind: There are multiple considerations, including blending it with other fuels such as natural gas. In fact, it is being considered in Europe to blend green hydrogen into the natural gas pipeline with trial runs currently taking place in Germany and Italy. The benefits would be utilizing the excess renewable power generated to reduce carbon dioxide emissions from natural gas utilities. Using the natural gas pipeline for hydrogen transport has also been proposed as an interim solution for a dedicated hydrogen pipeline.
Lou: What considerations are there when using hydrogen in combustion engines?
Hind: As a fuel, Hydrogen is ignitable in very dilute mixtures. In the engine, this means very lean operation, which is burning the fuel with excess air. The result is lower combustion temperatures resulting in decreases of NOx emissions. High dilution rates, either with air or EGR, are necessary with hydrogen to slow down the flame speed and the rate of pressure rise in the combustion chamber and to meet emissions
One important question for use in combustion engines: How do you carry Hydrogen in vehicles? That is the safety concern mentioned earlier – hydrogen must be compressed in expensive high-pressure tanks, which requires energy to compress and requires advanced storage technologies.
Lou: You also mentioned Ammonia. Can you tell us a bit about Ammonia as a fuel source and where it comes from?
Hind: ammonia is NH3: no carbons and high hydrogen content. Theoretically, ammonia appears attractive as a fuel. However, ammonia suffers from low energy density and undesirable combustion flame characteristics. If injected in the intake port or upstream, ammonia displaces a lot of air compared to natural gas, and if directly injected in the cylinder, the evaporation lowers the in-cylinder temperature drastically, making ignition difficult. Also, ammonia’s toxicity at low concentrations makes handling ammonia a safety concern.
Lou: So, why are folks even looking at Ammonia?
Hind: Well, compared to hydrogen, ammonia is easy to store – easy to compress and store as a liquid under pressure. Ammonia has also been investigated as a hydrogen carrier for fuel cells because it easily decomposes into nitrogen and hydrogen through a splitter or cracker, of which there are multiple solutions ranging in effectiveness and cost. In fact, some researchers use a heated catalyst to dissociate a small percentage of ammonia into hydrogen to help offset some of ammonia’s poor combustion traits, such as a low flame speed and high ignition energy. Most ammonia Internal Combustion Engine research has been done with hydrogen enrichment or another fuel.
Lou: I'm glad you took us through that. Sounds like there is a lot of interesting work going on in this area.
Lou: Hind, we always like to hear about new developments, but in the end, it all comes down to the economics. What can you share with us about the costs of such fuels?
Hind: As these fuels are still far out, we really don't have a firm number, indications at this time show levelized H2 production costs of $1.25 - $3.0/kg of H2. When compression/liquification and transportation costs are added the cost, range becomes $12-$20/kg of H2. Much of the cost is due to compression/liquefaction and distribution; production costs for gray hydrogen can be lower. Gray Hydrogen of course is hydrogen made by steam reforming of natural gas.
Ammonia is a bit more difficult because today, it requires a secondary fuel for ignition. Suffice it to say that it's the more expensive of the two alternatives.
Lou: I think everyone would expect new fuels to be more expensive and as they become more commercially adopted, that price should come down. Would you agree?
Hind: Once these fuels are more widely adopted than today and start propagating in the market, the economics of scale may influence the costs and hopefully make these options more economic. We need to expect though that development, establishment of distribution network, proof of concepts and field evaluations in engines would require time and resources, adding to the uncertainty of estimating costs of these fuel technologies.
Lou: There you have it folks. I'd like to thank "Hind Abi-Akar" for sharing her insights with us today… and thank you, our listeners for listening to Power Bytes.
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