Wondering what green hydrogen energy is? We break down Green Hydrogen Energy's role as a zero-emission energy carrier, and its potential for industrial processes, transport, and power generation.
Green Hydrogen Energy, or simply green hydrogen, is an energy carrier that, when produced through renewable means, offers a carbon-free alternative to fossil fuels. Green hydrogen energy refers to the potential energy stored in green hydrogen, which can be harnessed by burning it to power vehicles or other industrial processes. Since the only byproduct of burning hydrogen is water vapor, green hydrogen offers a pathway to energy production that does not emit carbon dioxide.
Currently, the dominant use of hydrogen is in oil refining and fertilizer production, which is referred to as grey hydrogen or when paired with carbon capture, blue hydrogen. As of now, the vast majority of hydrogen is derived from natural gas and coal, which contributes CO2 emissions equivalent to the combined output of Indonesia and the UK.
Extracting hydrogen from a variety of sources - including fossil fuels, biomass, and water - plays an integral part in multiple industries. Currently, about 75% of the global hydrogen production of 70 million tons comes from natural gas, equating to around 6% of the world's consumption of natural gas. Coal, which is predominantly used in China, is the second-largest source, while oil and electricity make up a smaller fraction.
Green hydrogen is therefore a very promising alternative in that it that its derived from renewable electricity and doesn't rely on fossil fuels. Demand for hydrogen has grown threefold since 1975 and continues to rise. But only 6% of global natural gas and 2% of global coal are used for hydrogen production. Those numbers could rise as major investments push forward the hydrogen economy.
As far as how to produce green hydrogen, goes, green hydrogen is produced by electrolysis. This is an electrochemical procedure where water is split into hydrogen and oxygen. The action happens within a device named an electrolyzer, which can be scaled to suit various production needs - from small, localized hydrogen generation to large central facilities powered directly by renewables or other non-carbon sources of electricity.
The method of operation for electrolyzers revolves around components like fuel cells, containing an anode and a cathode separated by an electrolyte, although the specifics vary depending on the type of electrolyte used and the ionic species it conducts. Hydrogen generated via electrolysis can theoretically have zero greenhouse gas emissions, contingent on the source of electricity utilized.
Today, water electrolysis contributes less than 0.1% of the global hydrogen production. Current power grid conditions in many regions aren't optimal for providing electrolysis-required electricity due to greenhouse gas emissions and inefficiency. Thus, electrolysis is being explored alongside renewable (wind, solar, hydro, geothermal) and nuclear energy options, which could achieve virtually zero greenhouse gas and pollutant emissions.
Polymer Electrolyte Membrane (PEM) electrolyzers use an electrolyte that is a special type of solid plastic to make electrolysis happen. This solid electrolyte reacts with water at the anode, forming oxygen and positively charged hydrogen ions. These hydrogen ions travel across the PEM to the cathode while the electrons follow an external circuit. Once they reach the cathode, the hydrogen ions merge with the external circuit electrons, creating hydrogen gas.
Alkaline electrolyzers, another variant, work differently, ferrying hydroxide ions through the electrolyte from the cathode to the anode, with hydrogen generated at the cathode. Traditional alkaline electrolyzers use a liquid alkaline solution as the electrolyte, but newer models utilize solid alkaline exchange membranes (AEM), showing promising results in laboratory testing.
Solid oxide electrolyzers, on the other hand, use a solid ceramic electrolyte that selectively conducts negatively charged oxygen ions at high temperatures. In this method, steam combines with electrons to form hydrogen gas and oxygen ions, which then move through the ceramic membrane and react at the anode to create oxygen gas.
With its "vibrant" potential, green hydrogen is making waves across diverse sectors. The industrial scene is already exploiting it widely, using it in the production of chemicals like ammonia and methanol, in oil refining processes, and in the steel-making industry. On the transportation front, the influence of green hydrogen is equally evident. It's powering up an array of fuel-cell vehicles – everything from cars and trucks to buses. Pilot programs have already taken place to fuel ships and aircraft in the future.
However, hydrogen is poised to infiltrate sectors where it's almost entirely absent, such as transportation, buildings, and power generation.
But it doesn't stop there. Green hydrogen has a promising future in our homes and buildings, either blended into our natural gas networks or utilized directly in hydrogen boilers or fuel cells. Think of it as a versatile heating solution that's both efficient and eco-friendly.
Green hydrogen in tanks or fuel canisters used as energy storage could bolster the power grid's flexibility and resilience in the face of unpredictable demand or supply fluctuations. And green hydrogen offers a key solution to mitigate carbon emissions in several industries, including long haulage transportation, shipping, aviation, and industrial sectors such as steel and ammonia, which make it appealing for attempts to hit 2050 net zero goals.
The IEA offers four strategic opportunities to scale up green hydrogen use: converting industrial ports into clean hydrogen hubs, leveraging existing natural gas infrastructure, expanding hydrogen in transport through fleets and freight, and launching international hydrogen trade routes.
The cost of hydrogen production today largely hinges on technical and economic elements, such as gas prices and capital expenditures. Fuel costs are the most significant aspect, comprising between 45% and 75% of the total production costs. Regions with low gas prices like the Middle East, Russia, and North America have some of the lowest hydrogen production costs. On the other hand, countries that rely on imported gas, such as Japan, Korea, China, and India, face higher hydrogen production costs due to elevated gas import prices.
The falling costs of renewable electricity, especially solar PV and wind, are sparking increasing interest in electrolytic hydrogen. While producing all of today’s dedicated hydrogen output from electricity would drastically increase electricity demand, it's seen as an opportunity for a renewable energy surplus.
Various nations and regions have set ambitious goals for clean hydrogen production as a part of their net-zero roadmap. For example, the United States Department of Energy identified opportunities for substantial clean hydrogen production by 2030 and 2050, while the EU announced its goal of reaching significant renewable hydrogen use by 2030.
Despite the interest, projections of incredibly low hydrogen costs, such as $0.5 /kg, do not align with a some analysts' assessment. For example, authors Lize Wan and Paul Butterworth argue more realistic figures suggest costs closer to $3 /kg, factoring in costs for storage, compression, and distribution. The received price of green hydrogen is likely to be over $3 /kg in 2050.
In their view, transitioning to a hydrogen-based system will inevitably lead to increased energy prices, affecting the economy, the competitiveness of different sectors, as well as consumer behavior.
While blue hydrogen does offer a potential carbon emission mitigation solution, it's not a zero-emission production route. Therefore, if the world aims to rely heavily on green hydrogen to meet its net-zero targets, sectors that are difficult to decarbonize will have to grapple with much higher energy costs.
As renewable energy sources become more affordable, the IEA predicts that the cost of producing hydrogen from such resources could fall by 30% by 2030 due to declining renewable costs and mass manufacturing of fuel cells, refueling equipment, and electrolyzers. However, to produce it on a scale that can meet global energy demands, significant amounts of cheap renewable electricity are needed, along with advancements in electrolyzer technology.
This pathway towards cleaner energy has garnered attention because it aligns with the Hydrogen Energy Earthshot goal: slashing the cost of clean hydrogen by 80% to $1 per kilogram within a decade.
Electrolysis also potentially syncs well with renewable energy power generation, particularly in cases of fluctuating and intermittent power generation inherent in certain renewable technologies. For instance, hydrogen fuel and electric power generation could be integrated at a wind farm, enabling flexibility in production shifts to match resource availability with operational needs and market factors.
In buildings, blending hydrogen into existing natural gas networks could be a potential short-term solution, while in the long run, the direct use of hydrogen in boilers or fuel cells is a viable option. In power generation, hydrogen stands out as a prime option for storing renewable energy, and hydrogen and ammonia can be used to improve power system flexibility.
In assessing the environmental benefits and economic feasibility of hydrogen production through electrolysis, one must take into account the source of the needed electricity, its cost and efficiency, and potential emissions from electricity generation.
The existing electricity grid isn't an ideal power source for electrolysis, as most electricity generation contributes to greenhouse gas emissions and is energy intensive.
Slow infrastructure development, high production costs, and regulatory barriers are among the key challenges.
In the transportation sector, the viability of hydrogen fuel cell vehicles will rely on fuel cell costs and the number of refuelling stations.
And short term scarcity coupled with long term uncertainty are one of the biggest barriers towards wider scale adoption and investment.
The hydrogen industry's growth will be fueled by enhanced international cooperation, common standards, knowledge sharing, and tracking progress towards shared long-term goals.
The U.S. Department of Energy, among other organizations, is relentlessly working to reduce the cost of renewable-based electricity production and develop more efficient fossil-fuel-based electricity production methods with carbon capture, utilization, and storage.
Addressing challenges is the primary focus of ongoing research. These include achieving the Hydrogen Shot target of $1/kg H2 by 2030 through better understanding of performance, cost, and durability trade-offs of electrolyzer systems under future dynamic operating conditions using CO2-free electricity.
The EU has a similar effort underway through its REPowerEU plan. By reducing the capital cost of the electrolyzer unit and system, enhancing energy efficiency for converting electricity to hydrogen over a range of operating conditions, and deepening knowledge about electrolyzer cell and stack degradation processes to develop strategies to extend operational life, green hydrogen may very well become a viable part of the energy mix over the next few decades.
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