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Fuel Cell Fundamentals
Not relying on wind or the sun to produce electricity, energy servers made from fuel cells may be the next new source of green energy.
There are several basic types of fuel cell energy servers. After reading this, you can decide if combined heat and power (CHP) energy servers or solid oxide fuel cell energy servers are right for your building.
In both cases, fuel cells make up energy servers. Energy servers provide for distributed power generation, which is power generation at the same location or point in which the power is consumed. Generating power on-site rather than at a central location (where power is transmitted from a power plant to where the power is needed) eliminates the cost, complexity, interdependencies, and inefficiencies associated with transmission and distribution. Servers generate electricity off the electric grid and aren’t subject to power outages. They’re also not dependent on weather, and can run all day.
Because these fuel cells always run and provide a consistent base load of power, they’re best for sites that have continuous power loads. However, if more power is supplied by the energy servers than your building needs, excess power can be fed back into the grid for credit through a net metering program.
Combined Heat and Power: The Basics
CHPs use a fuel processor to reform natural gas into ultra-clean hydrogen through a catalytic process. Then, through an electro-chemical reaction, they create electricity without burning natural gas like a traditional power plant. The hydrogen is processed through a fuel cell stack, creating DC power and heat. The DC electricity is converted into AC, which directly ties to a facility’s main electrical panel. This provides locally produced, continuous power for electricity needs. In addition, the heat produced by the fuel cell is transferred into the building by a hydronic system or heat exchanger, which supplies a continuous source of heat for hot water or space/radiant heating.
"A combined heat and power fuel cell is a more efficient power solution," says Nicole Elovitz, director of marketing at ClearEdge Power. "A majority of the energy lost in electricity production is given off in the form of byproduct heat, which a CHP system recycles and transfers to the customer in a usable form. When the electricity and the byproduct heat are used by the customer, the efficiency of converting fuel to usable energy is very high."
Solid Oxide Fuel Cells: The Basics
Solid oxide fuel cells generate power through an electromechanical reaction between oxygen and fuels, such as natural gas, ethanol, and landfill gas. A fuel source combines with steam to create a "reformed" fuel, which flows over the anode side (negative electrode) of the electrolyte. Warm air flows across the cathode side (positive electrode) of the electrolyte. The electrolyte is a solid ceramic tile made of beach sand, and allows only oxygen ions from the cathode to pass through to the anode. The chemical reaction of oxygen ions and the reformed fuel produces electricity, water, heat, and a small amount of carbon dioxide. The water and heat are reused to repeat the process.
According to Bloom Energy, these energy servers are 67-percent cleaner than typical coal-fired power plants – even when running on fossil fuel – and can be 100-percent cleaner when using a renewable fuel. In addition, customers pay an average of 4 cents less per kWh than the average California utility customer. Several businesses currently using these types of energy servers include eBay, FedEx, Walmart, and Staples.
Energy Servers Serving eBay
eBay is currently using energy servers in its San Jose, CA, campus as a supplement to traditional, on-the-grid electricity. The servers provide electricity for one out of every six eBay employees, supplying 15 percent of the energy for the campus."We get five times as much power from the Bloom servers as we do from our solar installation," says Amy Skoczlas-Cole, director of the eBay Green Team, "because the Bloom servers run 24/7. Together, our Bloom servers and solar installation take about one out of every three employees’ energy use at our San Jose, CA, campus off the grid."
With current state and federal incentives, eBay is expecting a three-year return on its investment.
"The best way to assess whether a fuel cell is a viable option is to have an energy savings analysis performed on the building’s historical use data," says Elovitz. "The team can run an analysis for the building based on usage and rate information to deduce whether a unit – or multiple units – would be the right solution."
Kylie Wroblaski (firstname.lastname@example.org) is associate editor for BUILDINGS.