Future Fuel: hydrogen and fuel cell technologies

India is the world's third largest energy consumer. The current demand for imported fuels is significantly outpacing domestic production and the country is being forced to spend valuable foreign capital to procure additional energy resources. Hydrogen is a concentrated primary source of energy which can be conveniently made available to the consumer. It is one of only a few potential near-zero emission energy carriers, alongside electricity and advanced biofuels. Nonetheless, it is important to note that hydrogen is an energy carrier and not an energy source; although hydrogen as a molecular component is abundant in nature, energy needs to be used to generate pure hydrogen.

This abundantly available element can be converted through high-efficiency conversion processes to various forms of energy. Hydrogen is an inexhaustible source, if it is obtained electrolytically from water. It is easiest and cleanest fuel, which upon combustion is almost entirely devoid of pollutant emissions. In addition, hydrogen fuel cell vehicles use 40-60 percent of the fuel energy with a fuel consumption reduction of 50 percent.

The hydrogen economy 

The talk about hydrogen economy has been going on since the 2000s. Earlier efforts were made to produce hydrogen from nuclear cycles but now there is an emphasis on bio and bio-inspired production. Hydrogen produced from bio or bio-inspired sources will lead towards increased de-carbonization of hydrogen production making fuel cell a viable alternative for transport and distributed power generation applications by the year 2040.

Hydrogen finds various uses in automotive fuel cells, consumer electronics, and stationary electricity and in heat generation applications. While the promise of hydrogen as a future fuel is well known, a major challenge remains its cost. In the last decade, the cost of fuel cell has come down to $50-60/ kWfrom $3000/ kW.

It is projected that by 2050, 13 percent of total energy demand will be for hydrogen, resulting in an annual CO2 reduction of 7.5Gt in 2050, and annual sales of $4,000 billion for hydrogen and hydrogen-related technologies. So we see that hydrogen not only benefits the energy system but also the environment and business. Depending on the generation, transmission, distribution and retail pathway, the carbon footprint of hydrogen can vary between almost 20 and more than 230 gCO2/MJ, as per the reports from IEA.

For all its simplicity, we have historically not been able to unlock hydrogen's full energy potential. Unlike other energy sources, hydrogen is tough to extract, store, transport and utilize. Therefore, so far, hydrogen remains merely a niche 'energy carrier' that is used for very specific and niche applications.

Hydrogen production 

Hydrogen may be drawn from fossil fuels and wood, water, or a combination of both. Natural gas is currently the primary source of hydrogen production, accounting for roughly three quarters of around 70 million tons of global annual dedicated hydrogen production. Hydrogen production accounts for about six percent of global natural gas utilization. Fuel costs are the biggest cost component, representing between 45 percent and 75 percent of the cost of production. Low gas prices in the Middle East, Russia and North America are triggering some of the lowest cost of hydrogen production. Gas importers like India have to deal with higher gas import prices, resulting in higher production costs for hydrogen, as per IEA.

According to IRENA, the best-case supply of renewable hydrogen may be economical today, but other typical conditions require further cost reductions. The lowest-cost wind and solar projects can deliver hydrogen at a cost comparable to that of fossil-fuel hydrogen. Figure 1 shows the costs of producing hydrogen from renewables and fossil fuels today. The data suggest that even today, though only in very specific situations, CO₂ -free renewables could be among the cheapest sources of hydrogen.

The futuristic and sustainable solution is green hydrogen generation from renewable. The competitiveness of hydrogen from renewables will continue to improve between now and next few decades, as per IRENA's assessment. Lifecycle carbon emissions of hydrogen are determined by the primary energy source and the process used for hydrogen production, and need to be taken into account when quantifying climate benefits. While green hydrogen is currently priced between €2-3 /kg, but by the year 2030 prices will fall to €1 /kg.

Hydrogen has proved its mettle in Japan with 95 percent lower wheel emissions and twice the energy per kg compared to natural gas, and 160 times to that of Li-ion batteries. As per IRENA's estimates, future costs of green hydrogen will be below those for blue hydrogen fossil fuels. By 2035, average-cost renewables also start to become competitive. Pricing of CO₂ emissions from fossil fuels further improves the competitiveness of green hydrogen. In the best locations, renewable hydrogen is competitive in the next 3-5 years compared to fossil fuels.

Hydrogen storage 

Hydrogen can be stored in various ways, such as gas at normal pressure or at high pressure, in the form of liquid hydrogen or that has a high gravimetric hydride. Hydrogen storage as a gas typically requires high-pressure tanks (tank pressure of 350–700 bar [5000–10,000 psi]). Hydrogen storage as a liquid requires cryogenic temperatures. The liquid hydrogen is the most common form of storage, is hard and expensive to handle. Like Liquefied Natural Gas (LNG), Liquefied Hydrogen Gas (LHG) can be transported as a global commodity. The main drawback of liquefaction is its high power consumption, which accounts for about 20-40 percent of the hydrogen energy content in the liquefaction process, in addition to eventual  loss of hydrogen due to boil-off. Liquid hydrogen is stored at minus 253 degrees celsius in super insulated cryogenic storage tanks. The high cost of liquid hydrogen storage makes it non-feasible. 

In recent times, significant progress has been made in hydrogen storage using solid-state storing material, such as metal hydride, chemical hydride and carbon nanotubes. Through these processes, hydrogen can also be bottled and transported embedded in hydrides, liquid organic hydrogen carriers and nanotubes which are potentially cheap, safe and easy to manage. Hydrogen is typically saturated with other compounds in an exothermic process at high temperature and pressure. It is then released in pure form by an endothermic dehydrogenation process at high temperature and atmospheric pressure. But, most of these systems store hydrogen with lesser volumetric energy density and there is need to develop a storage material that has a high gravimetric and volumetric density (9 wt percent), favorable thermodynamics, reversible and recyclable and cost effective.

Hydrogen supply chain 

The unique chemical properties that make hydrogen challenging to store, also make it challenging to transport. Hydrogen is taken to market in tanker trucks or pipelines. Tanker trucks carry the hydrogen in a compressed or liquefied state. During dispensation, the fuelling station has to use a pressurization system, which consumes even more of the remaining usable energy. Unlike, other forms of energy, storage and transport alone offset as much as 50 percent of all the inherent energy in the hydrogen. Another, way to deliver hydrogen is via gas pipelines, which is the least expensive option for transporting large volumes of hydrogen, but when compared to pipelines for natural gas or oil, hydrogen pipelines are quite expensive. 

Hydrogen has gained popularity in countries like Japan and the US, but in India, the costly infrastructure needed to support hydrogen is one of the reasons why it has not been widely adopted yet. India needs to work on refueling site compression, storage and dispensing and compressed gas tube trailers, liquid tankers and carriers, catalysts and regenerators for hydrogenation/ dehydrogenation to realize the hydrogen utilization in power and automotive sector.

Hydrogen utilization 

Fuel cells are one of the key enabling technologies for a future hydrogen economy. They have the potential to replace the internal combustion engine in vehicles and to provide power in stationary and portable power applications. A comparative assessment of petrol-fueled vehicle, battery electric vehicle and fuel cell vehicle is well illustrated in the figure below:

Methanol, which is a key feedstock for petrochemical products as well as a fuel additive, can be used as a hydrogen carrier fuel in the future, either directly combusted or reformed on board fuel cell vehicles. India based Thermax Ltd. has already developed a methanol reformer for methanol driven e-mobility. A thorough study shows that a hybrid design with charging done via methanol (hydrogen) will settle many challenges of pure battery electric vehicle.

Fuel Cells 

A fuel cell uses the hydrogen or other fuel to generate electricity in a safe and efficient manner. If hydrogen is fuel, then the only products are electricity, water, and heat. Fuel cells can be used in a wide range of applications, including applications for transport, material handling, stationary, portable and emergency backup power. Fuel cells can work more effectively than combustion engines and can transform the fuel's chemical energy into electrical energy with efficiencies of up to 60 percent.

The fuel cells are primarily classified according to the type of electrolyte they use. This classification specifies the type of electrochemical reactions that occur in the cell, the type of catalysts available, the range of temperature under which the cell operates, the appropriate fuel, and other factors.

Different types of fuel cells are currently being produced, each with its own advantages, limitations and potential applications. Phosphoric Acid Fuel Cell (PAFC), Proton Exchange Membrane Fuel Cell (PEMFC) and Alkaline Fuel Cell (AFC) are low operating temperature fuel cells, while Solid Oxide Fuel Cells (SOFC) and Molten Carbonate Fuel Cell (MCFC) are high operating temperature fuel cells. Despite global efforts to develop a fuel cell, some challenges need to be tackled, such as higher membrane ionic conductivity, impurity tolerance such as CO, S, Cl, and low temperature and affordable reformer catalyst.

Milestone for India 

It is estimated that India's hydrogen market set to cross $365 million mark by 2022, as per ASD reports. To achieve such milestones, we must target on producing hydrogen at a price of $1-2/kg utilizing sustainable hydrogen production pathways. By 2030, India must focus on rolling fuel-cell vehicles on the road, high-grade heat and power, and blending hydrogen with natural gas for domestic supplies.

To realize the dream of Hydrogen based economy, we must focus on Fuel Cell Electric Vehicles (FCEVs) as a primary consumer of hydrogen. These FCEVs refuel rapidly, run quiet and far, and beat the greenhouse gas emissions. Additionally, we must focus on large scale R&D to make hydrogen available as a source of clean energy at a price point that can compete with traditional and alternative fuels.

In general, a transition to a pollution-free, hydrogen economy is possible but the obstacles are significant. Companies such as NTPC, IOCL, etc. and intuitions like NISE, BHU, IIT, etc. has initiated the transition. NTPC is targeting to produce green hydrogen at a price of $1/kg, BHEL is working on the process to convert 1cubic meter of hydrogen in 1kWe, and Tata Motors has developed and is currently testing seven fuel cell buses. Nevertheless, the complete transition is still a long way off. In the meantime, it is important to work to reduce fossil fuel dependence through efficiency and substitution.