Hydrogen is currently enjoying unprecedented attention – especially in the energy sector – with the number of policies and ventures worldwide expanding rapidly. It is the most common element in the universe and is present in almost all organic compounds; it has been estimated that approximately 90 percent of all atoms are hydrogen (Columbia University). Yet, hydrogen atoms do not exist in nature by themselves. Its atoms need to be extracted from other compounds with which they occur, such as water; hydrocarbons, like methane; plants or fossil fuels. The efficiency of this process determines how sustainable generating energy with hydrogen can be. Can hydrogen help to achieve a clean, secure and affordable energy future?
There are several methods to produce hydrogen. The most common method is the thermal process of natural gas reforming using diesel, renewable liquid fuels, gasified coal, or gasified biomass. Today, about 95% of all hydrogen is produced from steam reforming of natural gas. Another method is the more energy–intensive electrolysis in which water is separated into its oxygen and hydrogen atoms. Other methods include solar-driven processes, which use light as the agent for hydrogen production; and biological processes, which use microbes such as bacteria and microalgae to produce hydrogen through biological reactions (Office of Energy Efficiency and Renewable Energy). Depending on the circumstances of the processes, the obtained hydrogen is categorized into colors, which define its degree of sustainability:
Gray hydrogen is obtained from fossil fuels. During production, natural gas is split under heat into hydrogen and carbon dioxide. The unused CO2 is then released into the atmosphere and thus intensifies the global greenhouse effect: The production of hydrogen produces around 10 times as much CO2 (Bundesministerium für Bildung und Forschung).
Blue hydrogen is gray hydrogen, of which the CO2 is captured and stored when it is generated. It does not get into the atmosphere; the hydrogen production is CO2-neutral (Bundesministerium für Bildung und Forschung).
Turquoise hydrogen is produced through the thermal breakdown of methane (methane pyrolysis). Instead of CO2, solid carbon is produced (Frankfurter Rundschau).
Green hydrogen can be obtained through electrolysis, gasification and fermentation of biomass as well as reforming of biogas (bdew). The difference: Regardless of the technology chosen, only electricity from renewable energies, such as wind or solar, is used, which makes the hydrogen production a carbon-neutral act (Bundesministerium für Bildung und Forschung). This pollutant-free hydrogen avoids the harmful emissions associated with other kinds of energy production and its only byproduct is water.
Hydrogen and energy share a long history – powering the first internal combustion engines over 200 years ago, being the fuel of space travel since the 1960s and today, becoming an integral part of the modern refining industry (BR Wissen, iea). Currently, hydrogen is mostly used in oil refining, ammonia production, methanol production and steel production; though is almost completely absent in areas such as transport, buildings and power generation (iea). However, with the sectors of transport and industry causing a significant percentage of CO2 emissions globally, the interest in hydrogen and its use as an alternative fuel is increasing (heise online).
In transportation, for example shipping and aviation, limited low-carbon fuel options are available. Hydrogen can power fuel cells in zero-emission fuel cell vehicles (FCEV), especially for commercial applications where bulkier vehicles such as buses, forklifts, trains or boats need to travel long distances, carry heavy loads and refuel with minimal downtime. For such applications, especially with the larger craft, electric batteries would need to be problematically large (Power Technology). With hydrogen as a raw material for synthetic fuels, these traffic areas can be redesigned in a climate-friendly way. In addition to the fuel cell, electricity-based fuels, so-called e-fuels, are being discussed as a further drive option, too. They also consist of hydrogen and ideally – if green electricity is solely used – they only release as much CO2 into the atmosphere during combustion as was previously withdrawn from it (BR).
To reduce the climate impact from traffic to a significant extent, the conversion of hydrogen into climate-neutral, synthetic fuels will require quantities of electricity that by far exceed all conceivable capacities of wind turbines and solar systems in Germany (Spiegel). Another problem is the low level of efficiency, which is – due to the conversion – worse than with other drive types (BR). Only 25 percent of the original energy leads to locomotion in a fuel cell vehicle, the rest is lost; in battery-operated electric cars, for example, the value is around 70 percent (t-online). In addition, the detour via hydrogen and the fuel cell requires twice to three times as much electricity to cover the same distance. Because hydrogen is not a naturally occurring raw material, it has to be produced with a high expenditure of energy (tagesschau). Also the necessary infrastructure for this technology is still largely missing (BR): While there are currently around 80 hydrogen filling stations in Germany, there are around 30,000 electric filling stations and around 15,000 regular gas filling stations (Handelsblatt, AutoBild, ADAC).
However, this light, storable, energy-dense gas with no direct emissions of pollutants or greenhouse gases has a big potential within the energy sector. Used within the right field, such as long-haul transport, chemicals, and iron and steel, it can help improve air quality and strengthen energy security. Additionally, hydrogen is versatile: It can be transported as a gas by pipelines or in liquid form by ships; it can be added to existing natural gas networks, with the highest potential in multifamily and commercial buildings, and transformed into fuels for cars, trucks, ships and planes (iea). Hydrogen’s supply is virtually limitless and, unlike batteries that are unable to store large quantities of electricity for extended periods of time, hydrogen can be stored in large amounts for a long time (Columbia University).
by Marie Klimczak