The fuel cell - a green powerhouse

Fuel cells generate electricity by combining hydrogen and oxygen. The only byproducts of this reaction are water and heat →1. A greener energy source can hardly be imagined. How can fuel cells be used to help the world in its quest for carbon neutrality, and what challenges lie ahead?

^{Mahesh Vaze ABB Corporate Research Bangalore, India, mahesh.vaze@in.abb.com; Mikko Kajava ABB Marine & Ports Helsinki, Finland, mikko.kajava@fi.abb.com}

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Rising urbanization is increasing global demand for energy [1] – a demand that is often satisfied by fossil fuels like oil, gas and coal →2. In developing countries, for example, despite a growing use of renewable energy sources, around 70 percent is still supplied by nonrenewable fossil fuels.

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Fossil fuel sources are limited and are increasingly difficult and expensive to extract. Not only that, but their use exacerbates greenhouse gas (GHG) levels, ozone layer depletion, acid rain damage, air pollution and climate change. Moreover, the fossil fuel supply chain itself can also have adverse effects, such as the air and water pollution and other dangers that can arise from fuel extraction, transportation and processing. One way to achieve power generation without CO, CO₂, SOx, NOx or particulate emissions is to use a fuel cell.

The fuel cell
A fuel cell is a flow reactor that directly converts the chemical energy of a fuel to electrical energy through electrochemical reactions. Whereas a combustion engine follows a multistep process (from chemical to thermal to mechanical to electrical) to convert the chemical energy of a fuel to electricity, the fuel cell needs only one step to oxidize its hydrogen fuel to electrical energy →3. The products of this conversion are electricity, water and heat. The water and heat are removed to improve fuel cell operation. Oxygen can be obtained from the ambient air and, if sustainably sourced hydrogen is used, no GHGs are produced. No pollutants are emitted and thus there is no risk of breaching environment and public health regulations.

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Fuel cells were invented in 1839 by Sir William Robert Grove, a Welsh physicist, and were later used by NASA to provide drinking water as well as electricity for space vehicles. Though early hydrogen misadventures (eg, the Hindenburg disaster) hindered fuel cell development for some time, recent technical advances have resulted in fuel cell technology that is reliable, safe and widely accepted by the public and private sectors. There are many types of fuel cell →4.

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Because of the fuel cell’s inherent modularity, they are predicted to have a bright future in stationary, portable and transport applications →5.

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Stationary applications of fuel cells
Stationary fuel cell power plants provide clean, efficient and reliable distributed power. Continuous reductions in fuel cell costs and improvements in their efficiency present a favorable marriage of economy and sustainability, as evinced by the surge in the number of such plants in recent years →6.

^{06 Fuel cell systems shipped [2].}

Currently, the world’s largest fuel cell park – constructed by FuelCell Energy Inc. in 2014 – comes in at 59 MW and supports Hwasung city, South Korea [3]. This plant runs on hydrogen obtained from the natural gas supply to the local district heating system.

Another successful fuel cell deployment is a 300 kW system in Fenchurch Street, London [4]. The challenge here was the integration of the fuel cell system into an established building with limited space. The fuel cell was, therefore, integrated into the building’s cooling, heating and power configuration. This installation achieves an emission reduction of 18,000 kg of pollutants and 1,800 tons of CO₂ when compared to an equivalent conventional combustion-based power generation scheme.

Fuel cells are now widely accepted as an alternative power source in rural regions where power supply is absent or unreliable. For example, the Poelano High School in Goedgevonden, Ventersdorp – a rural region in South Africa – has successfully implemented hydrogen fuel cell technology to deliver 2.5 kW for the school’s information, communication and technology (ICT) and lighting needs. The solution is reliable, efficient, safe and quiet. Such mini-grid fuel cell configurations can relieve or augment national grids and deliver social, political and economic benefits for remote or ill-served regions the world over.

Portable applications of fuel cells
Portable fuel cells (PFCs) are often desirable replacements for traditional lithium-ion and lead-acid batteries due to their higher energy density →7. Moreover, PFCs have advantages such as off-grid operation, longer run times, rapid recharging, lower weight, convenience, reliability and low operating costs. Hence, PFCs are utilized for military applications, auxiliary power units and portable products like torches and electronics. PFCs can provide power in a range of 5 W to 500 kW.

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For example, unmanned aerial vehicles (UAVs) use portable fuel cells for their primary propulsion system because of the fuel cell’s efficacy and reliability, longer operational life and low thermal, acoustic and vibration signatures. One instance is Ion Tiger, a liquid-hydrogen-powered UAV developed by the United States Naval Research Labora­tory, which weighs just 17 kg when equipped with 550 W of fuel cell power. Ion Tiger can stay aloft for over a day, more than six times longer than a battery-powered equivalent would. The use of cryogenic liquid hydrogen doubles this flight endurance.

Transport applications of fuel cells
To combat toxic air and declining fossil fuel reserves, many countries are rolling out hydrogen refueling infrastructure to accommodate vehicles powered by fuel cells →8. City authorities are reacting too. For example, Aberdeen City Council has introduced Europe’s largest fleet of hydrogen fuel cell buses [6]. In the first year, the fleet had more than 1,600 refueling events. Refueling takes just 5 to 7 minutes. The hydrogen refueling station was extremely reliable and available (99.99 percent) and dispensed 35,000 kg of hydrogen. City planners are now considering the expansion of the fleet, not least because this successful exercise won them the 2016 Low Carbon Championship award for the transport initiative of the year. Similar fuel cell buses have been successfully deployed in other cities around the world.

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Maritime operators, who contribute 3 to 5 percent of global CO₂ and over 5 percent of global SOx emissions, are also keen to use fuel cells and have therefore executed a number of research projects in this area →9. ABB, too, has fuel cell activities related to the maritime industry: the MARANDA project [7], for instance, is a joint venture of several companies financed by the European Union. The project will design and implement a 165 kW proton-exchange membrane fuel cell unit to be installed on board the research vessel Aranda. The main objective of the research project is to verify the fuel cell’s ability to produce emission-free electrical power with low noise and vibration levels in the marine environment. ABB will deliver the electrical power conversion technology needed to attach the fuel cell system to the vessel’s electrical power plant. Another fuel cell pilot project (100 kW capacity) was performed by ABB and Ballard in conjunction with Royal Caribbean Cruises [8].

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Challenges of hydrogen and fuel cells
Though hydrogen disperses very quickly in air, rapid­ly dropping below flammability level; does not have a lot of “bang-power” per volume compared to other common fuels; and its very rapid burn rate means that exposure to heat or flame will be extremely brief, care must be taken when handling it. Indeed, there are currently several standards governing fuel cell installation.

The fuel cell landscape has challenges in other areas, though:
• Safe and effective hydrogen production, storage and distribution.
• Cost, mostly due to expensive catalysts. Cost is the biggest hurdle for fuel cells today.
• Fuel cell stacks, built to generate higher voltage and power, need to be optimized for output, efficiency, cost and size. However, lifetime performance degradation, a key performance parameter, is not fully understood (kinetic loss, ohmic loss, loss of mass transport and loss of reformate are thought to be the sources of degradation). Moreover, the effects of freezing, thawing and stack impurities, as well as mitigation of stack water flooding or drying-out dangers, must be explored and accurately modeled. Multiphysics computational fluid dynamics (MCFD) and reduced order model (ROM) techniques can be exploited to model fuel cell electrochemistry, heat transfer and fluid mechanics to provide control and operational characteristic curves and to investigate fine-tuning and optimization. These operational characteristic curves are useful in designing the control and protection systems and power electronics needed to integrate fuel cells with the main grid.

Despite the challenges that remain, fuel cell technology has found wide acceptance with the public and with business. As a green powerhouse, the fuel cell is unrivaled – for what other power source can not only provide a clean source of electrical power but also deliver heat for the home or workplace and pure water that can be processed for drinking?

^{References
[1] Economic Times Bureau, “India’s energy consumption to grow faster than major economies,” Jan 27, 2017. Available: economictimes.indiatimes.com/industry/energy/oil-gas/indias-energy-consumption-to-grow-faster-than-major-­economies/articleshow/56800587.cms?from=mdr
[2] The Fuel Cell and Hydrogen Annual Review, 2016, 4th Energy Wave, 2016.
[3] T. Overton, “World’s Largest Fuel Cell Plant Opens in South Korea,” Power Magazine, February 25, 2014.
[4] Logan Energy, “A case study on 300 kW Fuel Cell System installed at 20 Fenchurch Street.” Available: www.loganenergy.com/wp-content/uploads/2015/11/150818-20-Fen­church-Street-GW.pdf
[5] B. Cook, “An introduction to fuel cells and hydrogen technology,” Heliocentris, Canada, 2001.
[6] Ballard, “A case study on Fuel Cell Zero-Emission Buses for Aberdeen, Scotland.” Available: ballard.com/docs/default-source/motive-modules-documents/aberdeen-case-study.pdf?sfvrsn=2
[7] M. Kajava, “MARANDA – Aranda goes hybrid.” Available: search.abb.com/library/Download.aspx?DocumentID=9AKK107045A7585&LanguageCode=en&DocumentPartId=&Action=Launch
[8] J. Bogen, “Catching fuel cell fever.” Available: new.abb.com/marine/generations/generations-2017/business-articles/catching-fuel-cell-fever}

^{Photo: Gaël Musquet, Wikimedia Commons
Photo fig. 08: AdrianHancu, istockphoto.com}