Silicon Chip Online - Applications For Fuel Cells

If hydrogen becomes the fuel of choice, what are the costs of manufacturing it and installing a completely new fuel distribution system?

Experience has shown that we should ask these questions early in the development of any new technology, no matter how great it looks at first glance. Looking at comparisons with existing fuel systems, the hydrogen fuel cell certainly comes out ahead environmentally.

Fig.1: comparision of carbon dioxode, nitrous oxides, sulphur dioxide and noise emissions between the four main engine types. As you can see, fuel cells win on every measure.

Fig.1 shows clearly that hydrogen fuel cell technology is below diesel, gas turbine and petrol engines with regard to CO₂, NO_X, SO_X and noise emissions.

Fig.2 shows a comparison between the overall environmental costs for existing internal combustion engine technology (ICE), electric vehicle technology (EV) and hydrogen fuel cell technology (H₂FC).

When all costs are considered: new technology costs, on-going upstream costs (eg, fuel production and distribution) and emission costs, particularly for vehicular applications, fuel cell technology is ahead but it is not a clear-cut conclusion.

In his article on solar power in the March 2002 issue of SILICON CHIP, Ross Tester concluded that most people would not use solar cell technology, no matter how environmentally desirable, unless it meant lower monetary costs for them. There is little doubt that the same conclusion will apply to the use of fuel cells.

Now let's look at some of the applications of fuel cell technology.

Developments have gone well beyond the prototype stage for several applications, particularly in space. When aircraft manufacturer Pratt & Whitney won the contract to supply fuel cells for the Apollo program in the early 1960s, their fuel cell design was based on modifications to the Bacon patents for alkaline fuel cells, which are the most efficient at low temperature.

Fig.2: the environmental costs of new technology versus old for internal combustion engines, electric vehicles and hydrogen fuel cells. Small wonder that fuel cells are regarded as the "green" alternative!

Three units capable of producing 1.5kW, or up to 2.2kW for short periods, were operated in parallel. Weighing around 114kg per unit and fuelled with cryogenic hydrogen and oxygen, these units ran for 10,000 hours during 18 missions without an in-flight incident.

And they produced all the fresh water for the space missions as well!

Continuing development by International Fuel Cells (which is a division of UTC, the company that P&W became) has meant that the fuel cell stacks used on each shuttle can now provide around ten times the power of similar-size units used in the Apollo craft.

Fuelled by cryogenic hydrogen and oxygen the cells are 70% efficient and have now completed over 80,000 operating hours in more than 100 missions. And there are no backup batteries.

Following the space program success, fuel cells have been used in:

An installation of five PC 25TM fuel cells at Anchorage in Alaska. Courtesy of International Fuel Cells LLC

Stationary power installations for utilities, factories, emergency power for hospitals, communications facilities, credit card centres, police stations, banks and computer installations
Diverse military applications
Domestic power supplies for individual residences
Mobile phones, laptop computers and other personal electronic devices
Transportation - particularly cars and buses but also in boats, trains, planes, scooters and bicycles, as well as highway road signs
Portable power for building sites, camping and vending machines.
Landfills and waste water treatment plants (which are using fuel cells to convert the methane gas they produce into electricity).

Energy supply systems based on fuel cells

Regardless of the type of fuel cell used, they all require a variety of peripheral units to store or convert fuel and convert the DC power generated for AC applications. In addition, they need pumps for fuel and air and ventilation fans to remove heat and water vapour.

Now we'll take a closer look at the way fuel cells fit into each of these various energy system applications.

Fig.3 represents a generic system based on fuel cells which could be a large utility energy system, a portable power supply or the power pack for a mobile phone - which may not need AC but will still need power conditioning.

When we think "fuel cells", until now we've automatically tended to think "big": space shuttles, buses, cars and stationary power generation. But as these pictures show, fuel cells can be downright miniscule! The two pictures at left show just how small fuel cells can be made (yes, that is a pencil!). The third photo, courtesy RoamPower, shows a fuel cell-powered emergency torch, while the fuel cell-powered notebook computer at right (courtesy Ballard Power Systems) is a portent of commercial products planned for release as early as next year and the year after.

Stationary systems

Fig.3: for those who might have missed our in-depth explanation earlier in this series, this graphic shows the operation of a typical fuel cell system. Oxygen (from the air) and hydrogen (from a hydrocarbon fuel) enter at left. Pure hydrogen is extracted by the processor. Both combine in the fuel cell(s) to form water, with a "byproduct" being a flow of electrons - or a DC current. This is then used, stored (eg. by charging a battery), or inverted to AC.

These fall roughly into the three categories: grid-connected; back-up power supplies and domestic installations.

At the time of writing, more than 200 fuel cell systems have been installed all over the world in hospitals, nursing homes, hotels, office buildings, schools and airport terminals. They are either being used to provide primary power or as a backup supply.

The following examples are typical of stationary installations that have been announced in the last year:

In September 2001, the town of Woking, 40km southwest of London, became the first community to sign up for a commercial fuel cell installation in the United Kingdom.

They contracted with UTC Fuel Cells for a 200kW PC25TM system to provide electricity and heat for the pool in Woking Park recreational centre, as well as electricity to light the park.

In December 2001, UTC Fuel Cells announced that a PC25TM fuel cell power plant had been installed at Ford Motor Company's North American Premier Automotive Group headquarters in California. The 200kW plant provides 25% of the building's power as well as hot water for the facility.

Siemens Power Generation Group will build a solid oxide fuel cell (SOFC) power plant with a maximum electrical capacity of 250kW in Hanover, Germany, to be completed by 2003.

Fuel cells on (small) wheels: the "MOJITO FC" fuel cell powered scooter showing the fuel cell stack in the pannier. The hydrogen supply is under the pillion seat.

The world's first fuel cell/gas turbine hybrid power plant is now operating at the National Fuel Cell Research Center in Irvine, California. The system features a Siemens Westing-house solid oxide fuel cell combined with an Ingersol Rand microturbine to produce approximately 190kW of electricity. Early test data show electrical efficiencies of approximately 53%, believed to be a world record for the operation of any fuel cell system on natural gas.

Improvements in the technology could ultimately raise efficiencies to 60% for smaller systems and 70% or higher for larger systems.

Residential installations

Although mass production will be crucial to bring prices down to make domestic installations practical, with large companies such as International Fuel Cells, Ballard Power and Avista Labs becoming involved, this will eventually happen.

From fuel processor...

Most domestic systems have a fuel processor as part of the fuel cell installation. This includes a fuel reformer, which processes a hydrocarbon fuel such as natural gas, into a hydrogen-rich gas known as reformate. A carbon monoxide (CO) cleanup unit is necessary to reduce the high concentrations of carbon monoxide produced in the process to acceptable levels (under 50ppm).

At the heart of the fuel cell system is the PEM fuel cell stack, which is made up of a membrane electrode assembly sandwiched between two gas diffusion layers with bipolar plates on each side.

The reformate (hydrogen) from the CO cleanup system feeds the fuel side of the fuel cell and the PEM cell generates a DC potential as described last month.

At right is the fuel cell pack in a Volkswagen car.

This is fed to the power conditioner which converts the low-voltage DC to high-voltage AC. Batteries are usually used to ensure that the system copes with power surges from motor start-ups or when peak demand exceeds the system output.

Fuel cell systems, generally with very quick start-up featured, seem to be ideal for primary household supply and as back-up for peak or emergency use or for remote areas.

A very attractive feature is that 'waste' heat can be used to provide hot water or space heating in a home. Since fuel cells operate silently, they are highly preferable to the typical diesel generator on rural properties.

Many of the prototypes being tried in residences use hydrogen extracted from propane or natural gas.

Transportation

As noted in the first article in this series, much of the development work being carried out with fuel cells is in the transportation industry. More than 100,000 fuel cell powered vehicles are expected on the world's roads by 2004.

As with the stationary fuel cell installations, peripherals are again required.

Fig.3 is a schematic of the main components. With wheel-mounted electric motors, fuel cell technology allows great flexibility in the placement of the various components.

All of the major automotive manufacturers now have at least one fuel cell vehicle under development, including Honda, Toyota, Daimler-Chrysler, GM, Ford, Hyundai, Nissan, Volkswagen and BMW.

Research has shown that the amount of carbon dioxide produced from a small car can be reduced by as much as 72% when powered by a fuel cell running on hydrogen reformed from natural gas instead of a conventional internal combustion engine.

However, it is not enough for the technology to meet tighter legislation on vehicle emissions. It must also provide transport that offers equivalent convenience and flexibility.

Fig.4: schematic diagram of the main components of a fuel cell system in a car with electric motors driving the front wheels, or the rear wheels, independently.

Being able to reach operating temperature rapidly, provide competitive fuel economy and give a responsive performance are all considerations that make the proton exchange membrane (PEM) fuel cells the favourite.

They reach operating temperature (around 800°C) quickly and respond rapidly to varying loads, as well as offering efficiency of up to 60%, compared to the 25% (at best) achieved by internal combustion engines.

PEM fuel cells also have the highest power density, which is crucial in modern vehicle design, and the solid polymer electrolyte helps to minimise potential corrosion and safety management problems.

However, to avoid catalyst poisoning at this low operating temperature ,PEM fuel cells do need an uncontaminated hydrogen fuel.

Still, most major vehicle manufacturers regard the PEM fuel cell as the eventual successor to the internal combustion engine.

Scooters & bicycles

Manhattan Scientifics and Aprilia unveiled a fuel cell powered concept scooter at the International Paris Fair in April this year. Called "MOJITO FC," the scooter is powered by Manhattan Scientifics' hydrogen fuelled 3kW fuel cell.

It is expected that production models will have a range of nearly 200km and a top speed of at least 60km an hour.

The fuel cell system, including all electronics, valves and fans, weighs slightly less than 6kg, with the fuel vessel weighing only 4.3kg.

Manhattan Scientifics believes fuel cell scooters with optimised drive systems will achieve a higher top speed and quicker acceleration than current vehicles with 50cc and 80cc internal combustion engines.

Manhattan Scientifics and Aprilia previously developed the Aprilia ENJOY FC, a concept fuel cell powered bicycle which received one of Time Magazine's 2001 "Inventions of the Year" awards.

Portable fuel cell power

A Plug Power 7kW residential PEM domestic fuel cell installation. Plug Power has been testing the above unit in a home since 1998. Detroit Edison co-founded the company and General Electric agreed in 1999 to distribute and service Plug Power cells. Such support has boosted expectations of a commercial introduction of the domestic fuel cell this year.

In the not-too-distant-future, miniature fuel cells will enable people to talk for up to a month on a mobile phone without recharging the battery. Miniature fuel cells will also power laptops and Palm Pilots for many hours longer than batteries can.

Direct methanol fuel cells powering mobile phones have already been tested and the Casio Computer Company intends to begin selling methanol fuel cells from 2004.

These cells will be able to continuously power a laptop computer for as long as 20 hours, compared with about 3-5 hours from batteries.

The methanol fuel for its fuel cells is expected to cost about 30 cents per litre, which sounds incredibly cheap when you consider the size of the unit that will be using it.

Landfill treatment

An Avista Labs Independence 1 - a 1kW PEM fuel cell.

According to the US EPA's Landfill Methane Outreach Program, landfill or biogas has already been tapped at 140 landfills in the USA to provide methane gas through fuel processors directly to fuel cells.

Since a demonstration test in 1992 at the Penrose Landfill, in Sun Valley, California proved successful, fuel cells have been installed and are now operating at landfills and waste water treatment facilities in several states in America as well as in Japan.

Groton Landfill in Connecticut, which has been operating since 1996, produces 600,000kWh of electricity a year, with a continuous net fuel cell output of 140kW. In 1997, ONSI (another division of UTC that markets fuel cells) installed a system at the Yonkers waste water treatment plant that produces over 1,600MWh of electricity per year, while releasing only 30kg of emissions into the environment.

The city of Portland, Oregon also installed a fuel cell to produce power using anaerobic digester gas from a waste water facility. It expects to generate 1,500MWh of electricity per year, reducing the treatment plant's electricity bills considerably.

Toshiba has installed fuel cells that run on waste gases at the Asahi and Sapporo breweries and is also targeting local government to sell fuel cell systems that run on gas from sewage, as it has done in Yokohama City.

Military applications

Fuel cells could provide power for most types of military equipment from land and sea transportation to portable handheld devices used in the field, so military applications are expected to become a significant market for fuel cell technology. The efficiency, versatility, extended running time and quiet operation make fuel cells extremely well suited for military applications.

Clearly, fuel cells would have many advantages over conventional batteries. For a start there would be no need to worry about the logistics of supplying spare batteries. In a similar way, the efficiency of fuel cells for transport would dramatically reduce the amount of fuel required during manoeuvres. Since the 1980s, the US Navy has used fuel cells for deep marine exploration craft and unmanned submarines.

How much do fuel cells cost?

Ah, the key question! As mentioned at the start of this article, most people won't take up new technology unless they feel that the tangible benefits outweigh the monetary costs.

Fuel cell power plants have been offered for about $6000 per kilowatt installation cost but this would only be acceptable in areas where electricity prices are high and natural gas prices low.

A study by Arthur D Little, Inc. predicted that when fuel cell costs drop below $3000 per kilowatt, they will achieve much wider market penetration.

In cars, fuel cells will have to be much cheaper to become commercially acceptable.

One of the main areas of development of fuel cells in transportation is in public transport buses. In the first article in this series, we showed the outside of the Citaro fuel cell powered bus. Now we can show you the X-ray version so that you can see where all the pieces fit in.

Note the hydrogen supply tanks mounted in the roof. This not only protects them from damage in case of a collision, especially, the hydrogen tanks, but allows for a continuous low floor design.

Hydrogen is very flammable if not handled correctly. Its safety is a factor that people will need to be convinced of before rushing out to buy a fuel cell powered car. In view of this, Honda has run front and rear collision tests on its FCX-V5 prototype, at a speed of 55km/h. The results confirmed high passenger protection safety during frontal tests and there was no hydrogen leakage from the high-pressure tank.