|Fuel cells are only starting to enter the marketplace and due to the many operational and cost benefits they offer they should start to be accepted on an accelerated basis.|
Alkaline Fuel Cell for Backup Power
and Light Utility Vehicle Applications
|by Peter K. Nor P.Eng., Astris Energi Inc.|
The fuel cell is a device that converts a fuel such as hydrogen directly to electricity with neither the combustion of the fuel nor an intermediate mechanical stage. The fuel cell is part of a complete system that has considerably fewer moving parts, when compared to a traditional diesel or gasoline generator the fuel cell system is quieter, more efficient and cleaner running. In fact, the outputs of a system as shown in Figure 1 are simply water and heat, with a noise level comparable to many desktop computers. This allows operation indoors or in areas where internal combustion based generators would not be permitted. Applications for such a device are numerous and in certain early adopting applications such as backup power and light utility vehicles a number of companies are making considerable progress.
Fuel cells come in a variety of types that can be broadly categorized into two groups based on the operating temperature of the fuel cell; low-temperature and high-temperature. Low temperature fuel cells generally have a shorter start-up time and react better to changes in power demand, making them well suited to smaller applications including transportation and backup power. High temperature fuel cells require long start-up times but can utilize more readily available fuels, making them more suited to continuous base load power applications and are not discussed here.
The economic case for the use of alkaline fuel cells (AFC) for these applications is based primarily on the fact that the price dynamic of the existing battery solution is different than for the AFC. The battery solution increases in cost and complexity in direct proportion to the required power and time required by the system. In a simple example, for a given power output if the backup time is doubled, the cost and complexity of the battery backup solution is approximately doubled. With a fuel cell system one can simply add additional fuel, at a fraction of the cost of doubling the battery bank. As price reductions are realized due to increased production volumes, fuel cell solutions will become the low-cost option for an increasing number of power applications.
The low cost fuel cell has been a challenge for some time due largely to the fact that many low-temperature fuel cells rely on expensive catalyst materials such as platinum. Astris Energi of Mississauga, Ontario has developed a fuel cell that does not require a platinum catalyst and as a result has the potential to become the low-cost fuel cell solution that is required for widespread adoption. Building on the benefits of less expensive materials, the system designed by the company delivers unparalleled efficiency resulting in reduced operating costs and reduced onsite hydrogen storage requirements. The AFC also offers a number of additional operational benefits such a tolerance to a wide variety of temperature (including sub-freezing) and humidity conditions.
The requirement for continuous, reliable power has come about as a direct result of our everyday reliance on a seemingly endless list of power hungry and mission critical equipment. The list of applications which must be either shut-down in a controlled manner or operated for long periods without their normal power supply is long and includes mechanical systems such as elevators and electronic equipment such as telecommunications and computers. Today, the majority of solutions rely heavily on the lead-acid battery and in some cases the battery bank is supplemented by a diesel or gasoline generator. Fuel cells that can be produced economically will be able to deliver increased performance and offer a savings to the operator for a variety of backup power applications due to decreased maintenance, simpler installation requirements and increased reliability. There is an incredible advantage to having a power supply that is fully independent from your primary supply. In times of extended power outage additional gas cylinders can be delivered to power the backup power system. There is no such option for batteries.
Although purchase cost is an important factor to entry of any new technology there are many secondary benefits to adopting an AFC based backup solution. Secondary benefits that are of particular importance are those that can be translated into savings in infrastructure or operations/maintenance. In the case of a backup solution that delivers 2kW for 10-hours the existing battery solution would weigh in excess of 2000 lbs. whereas the fuel cell solution would weigh less than 300 lbs. and would occupy only a 2ft by 2ft footprint.
Light Utility Vehicles
Increasing numbers of electric powered vehicles are being used around the world. Electric vehicles are being used today as people movers at airports, for material handling in warehouses and even on the golf course. The drive-trains in these vehicles are similar and they are typically powered by an onboard battery that has a number of limitations. Most importantly, batteries typically take hours to recharge and as a result continuous operations force the user to have multiple vehicles or at a minimum multiple batteries where a single vehicle with a single battery would be sufficient. The cost associated with the handling, charging and superfluous equipment is considerable. The fuel cell powered vehicle can run for a complete shift and typically be refuelled in less than a minute thus eliminating spare vehicles and batteries resulting in a considerable savings. Further, the fuel cell powered vehicle offers improved performance due to reduced overall weight and elimination of "battery-fade" that results in reduced performance in battery powered vehicles. The golf car shown in figure 2 is 20% lighter than the battery powered version, runs for 3-days between refuelling based on typical usage and being emission free and virtually silent can work indoors.
Fuel for low-temperature fuel cells is typically hydrogen. The supply infrastructure for hydrogen is identical to that of any commercial gas and is serviced by a variety of commercial gas suppliers. At current prices the cost of hydrogen is typically a small component of the total cost of ownership. Depending on the frequency and volume of refuelling the fuel costs can be comparable to the maintenance and upkeep costs of lead-acid batteries.
Fuel cells are only starting to enter the marketplace and due to the many operational and cost benefits they offer they should start to be accepted on an accelerated basis. Today, there are an increasing number of early adopters using these technologies. If fuel cells are successful in applications such as backup power and light utility vehicles where they can offer increased performance and savings for the operator there is potential that they will find virtually limitless applications where they can succeed.
Astris Energi Inc. has focussed on developing alkaline fuel cell (AFC) technology that has no platinum catalyst and no expensive membrane. Its goal is to deliver highly efficient, affordable fuel cells and fuel cell systems. Currently, Astris provides AFC stacks ranging in output from 1 W to 2400 W and complete power systems based on these fuel cells for backup, portable and mobile applications in sizes up to 10 kW. Astris has also developed a portfolio of test equipment for conventional battery and fuel cell developers including the intelligent TL5 Test Load and TESTMASTER™, a programmable, control and data acquisition software suite.