Lessons Learned: The efficient power of hydrogen

Figure 1: Solar energy splits water and transports the resulting hydrogen to users, where it produces water, while releasing its energy content as heat or electricity.

We live in the fossil fuels and nuclear age, but we should be moving towards the hydrogen age. I say "should" because it’s not certain we’ll reach it. In other words, it’s not certain that global warming will be stopped in time, or that the experiences of Hiroshima, Fukushima and other events will be enough to stop the nuclearization of the planet. Also, it’s not a given that we’ll switch to relying on solar energy. So, this column isn’t a description of the probable global energy technologies of the future, but only thoughts on achievable and desirable goals that process control technologies can support.

We know that energy can’t be created or destroyed, but it can be transported and transformed. One form of energy can be moved from one location to another, and in a new location, it can be converted and used in a new form. Today, energy is transported to users as fossil fuels or in uranium-based forms, and converted into new forms of heat or electricity. The energy distribution system is mostly centralized, so electricity produced by power plants (or fuel produced by refineries) requires expensive, long-distance transportation by electric grids, or by trucking or rail to reach users

In a hydrogen age, centralized energy distribution is expected to be more distributed (Figure 1). This will be done, in part, because some electricity will be produced "in place.” This process eliminates resistance loss and other costs associated with a grid, or the expense of transportation by trucks, trains, ships or pipelines to locations where energy content is converted into heat or electricity.

Hydrogen’s vitals

Hydrogen is the most abundant of all known substances, but it’s not commonly found in its pure form on Earth, and is usually only available in combination with other materials. Some of its properties are:

Some 90 million tons of "grey" hydrogen is produced yearly in the U.S. It’s used for fertilizer production, oil refineries, fuel cells, or as a primary fuel for space exploration. It’s currently made mostly from natural gas and coal, which results in some 800 million tons of carbon dioxide emissions. In a hydrogen age, it would be produced from water by using green energy without any carbon emissions.

Hydrogen can be stored as a gas or liquid. The associated problems are that extremely cold liquid like hydrogen can cause serious burns or embrittlement of steel or other metallic components. As a gas, hydrogen is usually safely stored in high-pressure tanks (or in large quantities in caves) at 350–700 bars [5,000–10,000 psi].

Direct burning of hydrogen in air results in high temperatures, which trigger nitrogen oxide (NOx) formation. High concentration of NOx can cause respiratory infections, decreased lung function and asthma. Therefore, when mixed with natural gas, its proportion is limited to 15%. When burning 100% hydrogen, specific equipment is used to remove NOx. Hydrogen burns with a pale blue flame, which is nearly invisible because it contains no soot, while combustion of other fuels is visible due to other materials.

The advantages of hydrogen include its high energy content, low weight and good safety record. The main cause of this good safety record (compared to hydrocarbon fuels) is that it’s 14 times lighter than air (while other fuels are heavier). When hydrogen leaks, it quickly rises and disperses in the air. Once its concentration drops below the lower explosive limit of 4%, it can’t ignite, even if an ignition source is present. Because hydrogen doesn’t accumulate on the ground, if stored outdoors or in well-ventilated areas, its fire or explosion hazard is less than other fuels.

Batteries vs. hydrogen

Today, most batteries are recharged by "grey" electricity, and most of the heat for households and industry is supplied by burning fossil fuels. Several industries benefit from maintaining this practice. The fossil-fuel industry benefits if the public believes that electrification through use of batteries helps the climate. Even some political leaders tend to overlook the fact that batteries are recharged by electricity made by power plants that burn carbon-emitting fossil fuels.

Others, such as battery-driven, electric vehicle (EV) manufacturers, prefer to minimize the potential competition that fuel cell-driven EVs represent, and work to discredit the hydrogen-fueled automobile industry. The fact that most governments support building electric charging stations—but not hydrogen fuel stations—indicates that these efforts have been successful.

Figure 2: Through hydrogen storage, the availability of intermittently available “green” energy becomes continuously available to supply the needs of transportation or other uses.

The battery-driven EV industry, among other methods, uses advertising that suggests that batteries are simple (Figure 2) and don’t emit carbon dioxide. The opposite is true. It’s misleading to show the sun or the solar panel in Figure 2 as the energy source because most battery recharging electricity comes from carbon-emitting, complicated power plants. Plus, it’s brought to the recharging stations over expensive and energy-wasting grids. In contrast, for fuel cell cars, no power plant and no grid are needed because the hydrogen fuel is stored directly in the car.