Hydrogen Power 101

­There is a worldwide imperative to reduce our reliance on carbon-based fuels and switch to clean energy. Consequently, hydrogen has emerged as a promising solution to address escalating demands for sustainable energy and efficient operations. Understanding the basics of hydrogen is essential in analyzing the potential impact of various regulatory, manufacturing, and supply chain-related factors on its market adaptation as a source of clean energy. So, let us look at the basics of hydrogen, how it can be produced, and how it can be used – directly as a fuel and as an energy storage medium.

At the ground level, there are three main reasons why the usage of hydrogen is of great interest:

●      It’s a potent energy carrier.

●      It’s a clean fuel.

●      It’s abundantly available.

Let’s dive into each of these areas.

HYDROGEN IS A POTENT ENERGY CARRIER

Hydrogen is an energy carrier, meaning it can temporarily store energy, which can be transported and later converted to other forms such as mechanical work (e.g. hydrogen-powered internal combustion engines) or electricity (e.g. hydrogen-powered fuel cells). Additionally, hydrogen is a “potent” energy carrier because it has the highest energy content of any common fuel on a weight basis. One pound of hydrogen contains 54.44 Megajoules (MJ) of energy versus one pound of diesel, which includes 20.64 MJ, or one pound of gasoline, which has 20 MJ of energy. That means, on a weight basis, the energy content of hydrogen is almost three times that of diesel or gasoline, making it an extremely potent energy source.

HYDROGEN IS A CLEAN FUEL

When hydrogen combines with pure oxygen through the electrochemical process, it produces water and releases energy i.e., electricity; thus, the process has no harmful byproducts. This environmentally friendly attribute makes it an appealing option for various applications in electric power generation and transportation.

Note that hydrogen burns clean only when combined with pure oxygen. When hydrogen burns with oxygen in the presence of air, other components in the air cause the production of oxides of nitrogen (NOx) as byproducts.

HYDROGEN IS ABUNDANTLY AVAILABLE

Hydrogen is everywhere on Earth. But it is found in a compound form. Although hydrogen is stable in its molecular form, the bond in the hydrogen molecule isn't that strong. That's why hydrogen does not exist naturally and needs to be extracted from various compounds, such as:

●      Liquid form: petroleum, water.

●      Gaseous form: natural gas of any methane-rich gas.

●      Solid form: coal, biomass (e.g. wood, manure, crops).

This leads to an important deduction: energy must be spent to extract hydrogen from    its various compound forms. 

Producing hydrogen

There are many ways to produce hydrogen, but two methods are commonly used for industrial-scale production: steam methane reforming (SMR) and electrolysis. 

SMR is conducted under high pressure and involves using high-temperature steam plus a catalyst to separate hydrogen from methane (CH4). The byproducts of this process are carbon monoxide (CO) and a relatively small amount of carbon dioxide (CO²). In the subsequent step, more hydrogen can be produced by combining the CO with steam and introducing a different catalyst. The byproduct of this step, called the water-gas shift reaction, is CO².

Electrolysis is the process of using electricity to split water into hydrogen and oxygen, using an electrolyte screen or membrane. The process produces hydrogen, oxygen, and nothing else – no harmful byproducts at all.

The production caveat

Interestingly, it takes more energy to produce hydrogen than it provides as an energy carrier. However, the benefits associated with its abundant availability, high energy content, and clean emissions characteristics overshadow this reality. 

The economics of using hydrogen as a fuel are becoming increasingly compelling for heavy industries, such as the steel and chemical industries. The fact that H2 is a low-emission – and potentially a no-emission option – can be an especially significant factor in these instances.

One of the ways hydrogen becomes a no-emission option is by utilizing solar and wind energies to produce hydrogen. This proposal compensates for the limitations of all three energy sources. Wind and solar are not only intermittent but they are variable and sometimes produce more energy than is needed. The proposal is to use the electricity generated by wind turbines and solar farms to produce hydrogen. This hydrogen is stored and can be used at any time. This way, the wind and solar production spikes can be smoothed out. Not being near high-voltage transmission lines becomes less of an issue. Meanwhile, excess production from wind and solar is typically discounted, which lowers the cost of H2 production.

The net result is that the entire energy chain is zero-emission, starting with generating electricity and moving on through the production of hydrogen and its usage.

The color code

If the electricity used in electrolysis is from clean, renewable sources such as wind and solar, then the hydrogen produced is considered green.

Subsequently, the energy industry has adopted a color code to refer to how hydrogen is produced and used. There are still some differences in definitions, but the terminology is settling down.

For instance, if the CO² produced in an SMR process is released into the atmosphere, the hydrogen produced is labelled as gray. If, however, the CO² is captured and stored (carbon sequestration) then the hydrogen produced would be termed blue. (The captured CO² can be used in various applications such as oil extraction, building materials, the food industry, etc.)

Hydrogen storage

Electricity is converted into hydrogen, hydrogen is stored, and then again used as a fuel to produce electricity (or energy). Although hydrogen has approximately three times the energy content of gasoline or diesel per unit weight, it is nearly 14.6 times lighter than air. Hence, the density of hydrogen needs to be increased to store it in a viable-sized storage tank. At room temperature, hydrogen can be stored in a gaseous form under high pressure. Hydrogen turns into liquid at an extremely low temperature of –423.17 degrees F at normal atmospheric pressure. In liquid form, due to its higher density than high-pressure storage in gaseous form, liquid hydrogen offers higher energy content in a smaller volume.

Hydrogen can also be stored in solid form. This entails the absorption or adsorption of hydrogen by another material.

Hydrogen is odorless, colorless and highly flammable, so its transportation and storage solutions must meet safety requirements.

Hydrogen and internal combustion engines

Internal combustion engines (ICE) can be divided into two categories, compression ignition (CI) engines such as diesel-fueled engines, and spark-ignited (SI) engines, including gasoline and gaseous-fueled engines.

Hydrogen can be blended with a primary fuel as an intermediate solution to minimize the unburnt hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO²) and particulate matter (PM) emissions. Due to its inherent properties, hydrogen is more suitable for use in SI engines than CI engines. Blending hydrogen with primary fuels does reduce engine power. 

It is also possible to use 100% hydrogen as a fuel, but this necessitates major changes in the engine design. The benefit would be zero carbon emissions, although by-production of oxides of nitrogen (NOx) cannot be eliminated.

Hydrogen fuel cells

Hydrogen-powered fuel cells are a promising technology that aid the pursuit of achieving net zero emission goals. Various types of fuel cells are available, each with its advantages and disadvantages and suitability to serve varied application needs. Fuel cell technology has been the focus of research and development in the energy sector, with many promising advancements being made in the electric power generation and transportation industries.

Hydrogen fuel cells are being adopted in various vehicles, including cars, trucks, forklifts, boats, and even some airplanes. In these applications, they can be viewed as somewhat akin to the batteries in electric vehicles (EVs). They are also used for electric power generation for prime, peak shaving, and emergency situations. Indeed, Kohler has recently partnered with Toyota to develop and install a hydrogen fuel cell power generation system at the Klickitat Valley Health Hospital in Goldendale, Washington.

A hydrogen fuel cell uses hydrogen and oxygen to produce electricity. Conceptually, the operation of a fuel cell is the opposite of electrolysis, and the process is similarly zero-emission. (Some fuel cells can operate on hydrogen-rich fuel as well, and these have some carbon emissions.) A typical fuel cell generates approximately 0.6 to 0.7 volts. The fuel cells are stacked in series to yield the desired output voltage and stacked in parallel to produce the desired power output.

Fuel cells are classified primarily based on the kind of electrolyte that they use. As a result, different types of fuel cells use different catalysts, operate at different temperature ranges and accept different fuels. These differences play a role in determining the suitability of a particular type of fuel cell for the given application.

Click image to enlarge 

Figure 2: Conceptual diagram of a typical fuel cell

Conclusion

Hydrogen’s versatility and eco-friendly characteristics promise to combat climate change and move towards clean energy. Besides electric power generation, hydrogen has been a subject of interest in many other industries, such as transportation, food processing, petroleum refining, manufacturing, and many more. Research company Markets & Markets estimated that the revenue produced by hydrogen in 2023 was about $247 billion. The firm projects that figure will nearly double by 2030, to over $410 billion, driven partly by new energy uses. These new uses are being encouraged through a variety of government initiatives around the world. The most ambitious might be the U.S. National Clean Hydrogen Strategy and Roadmap.

Ultimately, the makeup of hydrogen as a clean energy source holds the potential to revolutionize the power generation industry, offering an environmentally sustainable solution to meet the escalating energy demands, while reducing the carbon footprint.

Kohler Power Systems North America