8 minutes Show
14 Apr 2021 renewable energy
The debate around hydrogen energy is getting more and more attention. Something which was a niche feedstock product serving heavy industry is now very much at the forefront of decarbonising the transportation and shipping world. Hundreds of billions of dollars are being invested into projects aimed at helping achieve net-zero targets and creating zero-emission fuel. Against that backdrop, let's take a closer look at the different options available.
The most common form of hydrogen, it's created from fossil fuels and the process releases carbon dioxide which is not captured. The process used to create hydrogen from natural gas is called steam methane reforming (SMR), where high-temperature steam (700°C–1,000°C) is used to produce hydrogen from a methane source, such as natural gas. In steam methane reforming, methane reacts with steam under 3–25 bar pressure (1 bar = 14.5 pounds per square inch) in the presence of a catalyst to produce hydrogen, carbon monoxide, and a relatively small amount of carbon dioxide. Steam reforming is endothermic — that is, heat must be supplied to the process for the reaction to proceed. There is also a gasification process which uses coal as a feedstock, creating brown hydrogen, which also releases carbon dioxide and can be put in the same category as grey. The head of business development at the renewable energy giant Enel has described hydrogen as a "climate killer" as it stands right now due to almost all of it being grey: “98% of it is produced from steam reforming and gasification, which equates to yearly carbon emissions comparable to that of Indonesia and the UK combined," he said. "Just 2% is produced from electrolysis.” Clearly then, grey hydrogen is not a long-term solution.
Blue HydrogenBlue hydrogen uses the same process as grey, except this time the carbon is captured and stored. This makes it much more environmentally friendly, but comes with added technical challenges and a big increase in cost. Carbon capture and storage (CCS) has been around a while, with the technology being used by heavy industry and power generation companies burning fossil fuels. The technology can capture up to 90% of the CO2 produced, so it isn't perfect but clearly a massive improvement. Most of the time, this CO2 is then transported by a pipeline and stored deep underground, often in salt caverns or depleted oil and gas reservoirs. Countries which do not have access to such underground options will find it very challenging to establish a blue hydrogen industry, and it may be more cost-effective to develop green hydrogen as their primary solution. Some forward thinking organisations like Drax in the UK have been combining CCS with biomass fuels, aiming to become carbon negative — removing more carbon dioxide from the atmosphere than it produces. When it comes to hydrogen production, blue hydrogen is often seen as a stepping stone from grey to green, and it's proven to be divisive among industry professionals. On one hand, it is relatively easy to scale up from existing grey hydrogen production and requires less electricity. It is also not dependent on the rapid & continuous growth in renewable energy sources such as offshore wind & solar. On the other, think tanks and green hydrogen advocates argue that blue hydrogen goes against the goals and principles of net-zero, as well as being more expensive than green in the medium term.
The utopian vision of the future is a net-zero world where all our electricity and fuel is produced by emission-free sources. In the context of this piece, that means a fully-scaled green hydrogen industry on a global scale. It has the potential to be a major part in solving the intermittent generating capacity of most renewable energy sources. Excess electricity can be used to create hydrogen, which is then stored as a gas or liquid until needed. It faces many challenges, but the momentum behind it is growing with governments around the world recognising the potential benefits and developing policies to help drive development and adoption. So, what exactly is green hydrogen? Rather than using fossil fuels, green hydrogen is made by using a process called electrolysis to split water into hydrogen and oxygen. If that process is powered by a renewable energy source, such as wind or solar power, then the hydrogen is referred to as being green. What are the challenges?- Technology Green hydrogen needs electrolysers to be built on a scale larger than we've yet seen. - Transportation and Storage Either very high pressures or very high temperatures are required, both with their own technical difficulties. - Cost To become competitive, the price per kilogram of green hydrogen has to reduce to a benchmark of $2/kg, with Bloomberg New Energy Finance reporting that $1/kg is achievable by 2050. At these prices, green hydrogen can compete with natural gas. “Costs for producing green hydrogen have fallen 50% since 2015 and could be reduced by an additional 30% by 2025 due to the benefits of increased scale and more standardized manufacturing, among other factors,” said Simon Blakey, a senior adviser for global gas at IHS Markit. - Electricity Creating green hydrogen needs a huge amount of electricity, which means a mind-blowing increase in the amount of wind and solar power to meet global targets. Some current estimates are that that we need to install more offshore wind capacity than in the previous 20 years, every year for the next 30 years. These are all major challenges, but a lot of them are already being overcome by incredible engineers and scientists. With the right backing, we can be confident that green hydrogen will prove itself to be the amazing energy solution we need.
Researchers at NREL are developing advanced processes to produce hydrogen economically from sustainable resources. Learn how NREL is developing and advancing a number of pathways to renewable hydrogen production. Text Version Biological Water SplittingCertain photosynthetic microbes use light energy to produce hydrogen from water as part of their metabolic processes. Because oxygen is produced along with the hydrogen, photobiological hydrogen production technology must overcome the inherent oxygen sensitivity of hydrogen-evolving enzyme systems. NREL researchers are addressing this issue by screening for naturally occurring organisms that are more tolerant of oxygen and by creating new genetic forms of the organisms that can sustain hydrogen production in the presence of oxygen. Researchers are also developing a new system that uses a metabolic switch (sulfur deprivation) to cycle algal cells between the photosynthetic growth phase and the hydrogen production phase. Contact: Maria Ghirardi FermentationNREL scientists are developing pretreatment technologies to convert lignocellulosic biomass into sugar-rich feedstocks that can be directly fermented to produce hydrogen, ethanol, and high-value chemicals. Researchers are also working to identify a consortium of Clostridium that can directly ferment hemicellulose to hydrogen. Other research areas involve bio-prospecting efficient cellulolytic microbes, such as Clostridium thermocellum, that can ferment crystalline cellulose directly to hydrogen to lower feedstock costs. Once a model cellulolytic bacterium is identified, its potential for genetic manipulations, including sensitivity to antibiotics and ease of genetic transformation, will be determined. NREL's future fermentation projects will focus on developing strategies to generate mutants that are blocked selectively from producing waste acids and solvents to maximize hydrogen yield. Contact: Pin-Ching Maness Conversion of Biomass and WastesHydrogen can be produced via pyrolysis or gasification of biomass resources such as agricultural residues like peanut shells; consumer wastes including plastics and waste grease; or biomass specifically grown for energy uses. Biomass pyrolysis produces a liquid product (bio-oil) that contains a wide spectrum of components that can be separated into valuable chemicals and fuels, including hydrogen. NREL researchers are currently focusing on hydrogen production by catalytic reforming of biomass pyrolysis products. Specific research areas include reforming of pyrolysis streams and development and testing of fluidizable catalysts. Contact: Richard French Photoelectrochemical Water SplittingThe cleanest way to produce hydrogen is by using sunlight to directly split water into hydrogen and oxygen. Multijunction cell technology developed by the photovoltaic industry is being used for photoelectrochemical (PEC) light harvesting systems that generate sufficient voltage to split water and are stable in a water/electrolyte environment. The NREL-developed PEC system produces hydrogen from sunlight without the expense and complication of electrolyzers, at a solar-to-hydrogen conversion efficiency of 12.4% lower heating value using captured light. Research is underway to identify more efficient, lower cost materials and systems that are durable and stable against corrosion in an aqueous environment. Contact: John Turner or Todd Deutsch Solar Thermal Water SplittingNREL researchers use the High-Flux Solar Furnace reactor to concentrate solar energy and generate temperatures between 1,000 and 2,000 degrees Celsius. Ultra-high temperatures are required for thermochemical reaction cycles to produce hydrogen. Such high-temperature, high-flux, solar-driven thermochemical processes offer a novel approach for the environmentally benign production of hydrogen. Very high reaction rates at these elevated temperatures give rise to very fast reaction rates, which significantly enhance production rates and more than compensate for the intermittent nature of the solar resource. Contact: Judy Netter Renewable ElectrolysisRenewable energy sources such as photovoltaics, wind, biomass, hydro, and geothermal can provide clean and sustainable electricity for our nation. However, renewable energy sources are naturally variable, requiring energy storage or a hybrid system to accommodate daily and seasonal changes. One solution is to produce hydrogen through the electrolysis—splitting with an electric current—of water and to use that hydrogen in a fuel cell to produce electricity during times of low power production or peak demand, or to use the hydrogen in fuel cell vehicles. Researchers at NREL's Energy Systems Integration Facility and Hydrogen Infrastructure Testing and Research Facility are examining the issues related to using renewable energy sources for producing hydrogen via the electrolysis of water. NREL tests integrated electrolysis systems and investigates design options to lower capital costs and enhance performance. Learn more about NREL's renewable electrolysis research. Contact: Kevin Harrison Hydrogen Dispenser Hose ReliabilityWith a focus on reducing costs and increasing reliability and safety, NREL performs accelerated testing and cycling of 700 bar hydrogen dispensing hoses at the Energy Systems Integration Facility using automated robotics to simulate field conditions. View the video of the robot, which mimics the repetitive stress of a person bending and twisting a hose to dispense hydrogen into a fuel cell vehicle's onboard storage tank. Researchers perform mechanical, thermal, and pressure stress tests on new and used hydrogen dispensing hoses. The hose material is analyzed to identify hydrogen infiltration, embrittlement, and crack initiation/propagation. Contact: Kevin Harrison Hydrogen Production and Delivery Pathway AnalysisNREL performs systems-level analyses on a variety of sustainable hydrogen production and delivery pathways. These efforts focus on determining status improvements resulting from technology advancements, cost as a function of production volume, and the potential for cost reductions. Results help identify barriers to the success of these pathways, primary cost drivers, and remaining R&D challenges. NREL-developed hydrogen analysis case studies provide transparent projections of current and future hydrogen production costs. Learn more about NREL's systems analysis work. Contact: Genevieve Saur HydroGEN Energy Materials NetworkNREL serves as the lead laboratory for the HydroGEN Energy Materials Network (EMN) consortium. Recent PublicationsDirect Solar-to-Hydrogen Conversion via Inverted Metamorphic Multi-Junction Semiconductor Architectures, Nature Energy (2017) Remarkable Stability of Unmodified GaAs Photocathodes during Hydrogen Evolution in Acidic Electrolyte, Journal of Materials Chemistry A (2016) Solar to Hydrogen Efficiency: Shining Light on Photoelectrochemical Device Performance, Energy and Environmental Science (2016) Reversible GaInP2 Surface Passivation by Water Adsorption: A Model System for Ambient-Dependent Photoluminescence, Journal of Physical Chemistry C (2016) CO2-Fixing One-Carbon Metabolism in a Cellulose-Degrading Bacterium Clostridium thermocellum, Proceedings of the National Academy of Sciences (2016) Phosphoketolase Pathway Contributes to Carbon Metabolism in Cyanobacteria, Nature Plants (2016) ContactHuyen Dinh Email |
What is not a common method of producing hydrogen gas?
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