GAS TURBINES AND HYDROGEN, COULD BE BATMAN AND ROBIN?
Updated: Oct 8, 2022
We already discussed about the basics of the Energy Transition as well as other angles related to the topic. Today, let us explore with you a very trendy topic that is one of the major pillars for the decarbonization. This is, the powerful duo between Gas Turbines and Hydrogen, also known as the Batman and Robin superheroes of Climate Change. But, to better understand the power of this couple, we need to cover some concepts first.
A gas turbine, also known as Batman, is basically an internal combustion machine (driver) that transforms the energy from a fuel, into mechanical energy (to the shaft) and heat (in the exhaust gases). This heat normally is a loss, unless we use it (I will come back into this point at the end of the article). This energy from the shaft (in the way of torque and power) can be used to move other machines (known as driven) such as a compressor (to compress a gas and move it through a pipeline or to increase the pressure of a gas to use it in a process) or an electric regenerator (that generates electric energy). We like to call these equipment “energy transformers” because they transform one kind of energy (chemical from the combustion for example) into another (like mechanical or electric).
The gas turbine 101 goes as follows, the air enters the machine through an air filter and inlet plenum, then is compressed by a compressor and enters the combustion chamber, where the diffusers and combustors are located. In the combustion chamber the magic happens, the air is mixed with the fuel and it is ignited, generating a flame, and converting the chemical energy inside the fuel (calorific power) into heat that also expands the gas. This gas in expansion pass through the turbine wheels transferring part of the energy and producing mechanical movement that is delivered through the shaft (this is a brief simplification, if you are interested on this specific topic we can arrange a dedicated session). Finally, the gases product of the combustion, exits the turbine through the exhaust plenum and the stack to the atmosphere with the remaining energy. The other part or the equation is the fuel, normally gas turbines use natural gas, but, in some cases they can use liquid fuels like diesel, kerosene (similar than the Jet Fuel of aviation) ethane, ammonia, propane, and many others. The combustion of fossil fuels, generates Carbon Dioxide emissions (CO2) as products of the combustion, and as we already discussed, CO2 is one of the GHG inventory gases we should try to avoid to fight the Climate Change.
Well, here the Hydrogen enters stage, aka Robin. The Hydrogen (H2) has also a calorific potential and can be used as fuel and be burned in a gas turbine (as well as in many other internal combustion engines). The magic is that combusting hydrogen and air, generates as products of the combustion water in form of steam, that is less harmless for the environment than GHGs. Other emissions are the NOX or nitrogen oxides, that are dangerous because can generate acid rain; however, they can be captured in the exhaust of the turbine by catalytic systems. Hydrogen implementation sounds like a walk in the park, right? So, why not converting all the existent gas turbines to be used with Hydrogen? Well, it is a little more complicated that it sounds.
First, Hydrogen must be produced at high volumes to replace liquid fuels and natural gas used today in gas turbines. Preferably, we should migrate to blue or green hydrogen (that are carbon neutral, otherwise we better we stay with the Natural Gas). Hence, until the world produces enough volume of blue or green hydrogen, we will need to wait some years or decades. Then, we have the price barrier of H2, , today green hydrogen it is still around five times more expensive than blue hydrogen, and both are more expensive than natural gas. On the other hand, this pre-combustion decarbonization solution competes with post-combustion decarbonization solutions like Carbon Capture Utilization and Storage or CCUS (which allows burning cheap natural gas). However, most of the energy companies, Oil & Gas majors and market analysts predict that green hydrogen will become very competitive by 2030 or sooner.
The trick of the green hydrogen is the location, local availability can significantly decrease its cost. Geopolitically speaking, we have net natural gas exporter countries (in the form of liquefied natural gas or LNG to facilitate the transportation) and net importers. For example, some exporters are Qatar, USA, Australia, Canada and Peru, while some importers are UK, Italy, Spain, Germany, Japan and China. Then if you can produce green hydrogen in your own country approximately at the same price that you pay today for imported LNG (let’s said below 2 USD per kilogram) the equation works and you also increase the reliability of your energy supply (take a look to this article of IEA about Hydrogen in Latin America link #1 below). We believe this is a potential reasons that UK, Germany and Japan pushing for green hydrogen and working to become green H2 hubs. Having said that, the exporters might forecast that current customers (the importers) could partially shift the LNG to H2, and they are also trying to offer cheap green H2 to compete as soon as possible (the case of Australia). Nevertheless, in our opinion the question mark is around the countries that have access to cheap gas, mainly because the green H2 may be never as competitive, and potentially those countries will find a better scenario in the development of CCUS projects (post-combustion solutions). Many of us are confident that green hydrogen has the potential to change the macroeconomics of the energy scenario in the next 20 years, since it can be produced almost everywhere as far as you have good and cheap renewable energy and water, and also, due to the opportunity it offers to democratize the access of energy plus its decarbonization potential.
The other aspect is related to the access of hydrogen as fuel, because most probably will be not produced where it’s required (meaning nearby) and we will need transport it to places to be used. This task can be done by liquefying the hydrogen to send it by trucks or vessels, or compress it to send it by pipelines. Using existent pipelines is feasible but under certain conditions (Snam, one of Italy’s leading energy infrastructure operators, is working very actively about this in Italy and Europe: link #2). We can send a blend of hydrogen in natural gas and partially decrease the emissions (this is a very quick and smart way to reduce some emissions in the short term and involve minimum investments) or try a pure hydrogen pipeline. These are all feasible solutions with different cost impact which will be finally translated to a transport tariff embedded in the total H2 cost.
Yet, remember our Batman, the gas turbine, must be hydrogen ready to handle this new fuel. Some turbines can burn it with no major issue, Baker Hughes turbomachinery division for example has more than 50 years of experience with gas turbines burning hydrogen (link #3 below). Some other turbines can be modified from natural gas into hydrogen, and unfortunately some others cannot be modified. This is because the hydrogen when burned, has different flame velocity and shape (quicker and longer than natural gas) so the combustion chambers must be capable to handle it. Some gas turbine Original Equipment Manufacturers (OEMs) are working since several years evaluating the potential modifications required for all the existent models, and for the gas turbines that are designed from scratch we try to make them hydrogen ready. This is pretty useful because if you are thinking on acquiring a new gas turbine and also considering the Energy Transition and decarbonization future, will be better if your new machine is hydrogen ready from day one, ensuring you will be able to convert it into a carbon neutral asset as soon as you want (or green hydrogen becomes cheap enough!).
Last but not least, we can increase the efficiency aka Batgirl. Remember the heat at the exhaust I mentioned at the beginning? well as any thermal machine, the gas turbine has certain efficiency transforming the energy from the fuel into shaft power, and this efficiency can vary between 30% and 44%, while the remaining it is normally lost in form of heat in the exhaust. This is also valid for hydrogen, it is true you will not generate CO2 emissions but the thermodynamic laws are the same, and some energy will be lost in the exhaust gases anyway. In order to save and use some of this (normally lost) energy, there are some equipment that can be paired to the gas turbines and take advantage of it.
The task is performed equipment like a WHRU (Waste Heat Recovery Unit) that can use the heat of the exhaust gases to heat other fluids like oil or even heat water for heating purposes (this last one is called CHT or Combined Heat and Power if the turbine is used also to generate electric energy). Other common piece of equipment suited for the task is the HRSG (Heat Recovery Steam Generator) that transfers the heat to water producing steam, and this steam can be used for a process (like inside a refinery) or to couple another great machine like the steam turbine, and delivers some additional electric energy (known as combined cycle or CCGT, because combines two thermodynamic cycles, Bryton and Rankine). The combination of a gas turbine with some of these waste heat recovery systems can push the efficiency up to 80% or even above.
If at this point, you are not already in-love with the gas turbines, We don’t know what is wrong you! Jokes apart, gas turbines are very capable, useful and well known energy transformers that combined with carbon neutral fuels like green hydrogen and pushing the efficiency up to the roof with waste heat recovery systems, can be our Batman, Robin and Batgirl to fight the climate change.
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