Fuel Cell Backup Generators

Application performance is a many-headed thing. Ultimately application software executes on servers and these reside in data centers. So how do the hosting centers perform? Many companies want to operate, or at least market themselves, as green companies. The goal is to use less carbon-based fuels and reduce their carbon emissions.  Toward this end, Apple, eBay, AT&T, and Microsoft have replaced diesel generator backup systems with ceramic fuel cells from Bloom Energy at some of their data centers.  How do these work?

Diesel generators generate electricity by using mechanical energy to rotate a wire inside a magnetic field, a well-known process to produce electricity, discovered in 1831 and taught to many kids in high school physics.  The problem with diesel generators is fuel is expensive and emits nitric oxide, carbon monoxide, and particulate matter into the environment; in other words, they pollute.

Fuel cells are an attempt to replace diesel fuel generators, with something that does not pollute. Also, if properly designed, they might cost less in the long run.  The problem is existing fuel cell technology requires platinum, which is expensive, and does not produce enough power.

Fuel cells operate like a battery.  A traditional battery works by placing two electrodes (a metal, like copper, that conducts electricity) inside an electrolyte (acid). The cathode electrode has a positive electric charge (+). The anode has negative electric charge (-). Power is produced when ions flow from anode to cathode.  The electrolyte disrupts this flow redirecting it to the path of least resistance, which is the electrical wire attached to the battery.  This provides power for user consumption. The battery does not last long, because the electrolyte loses its ability to redirect this charge over time, so it must be recharged by redirecting this flow in the opposite direction using an external power source.

A fuel cells works on the same principle in that it uses a cathode and an anode, except that it requires a fuel, like methane, albeit much less fuel that a diesel generator.  The fuel cell emits oxygen and water instead of pollutants.   Engineers have tried to boost their power output by recapturing some of the heat they vent and putting that back into the process.  This is called combined heat and power (CHP) fuel cells.  These are costly, because they require platinum electrodes, and difficult to operate, because they require exacting environmental conditions to work.

What Bloom Power has done is to drive down the cost of this process and boosting its power by patenting a technology that replaces the platinum electrodes with ceramic, which is made from sand.  Bloom Power calls these solid oxide fuel cells (SOFCs).  The company says, “They are like batteries, except they always run.”

Fuel passes into anode side of fuel cell.  It oxidizes the fuel, releasing oxygen and water (steam).  This steam is redirected to help power the fuel cell, which requires an operating temperature of 800°C.  (To put this into perspective, at this temperature, zinc−which, ironically, can be used as an electrode in traditional batteries−melts.)  Electricity flows out the other side.

The Bloom Power Energy Server produces 200 kilowatts of power by wiring many of these fuel cells together.  (By comparison, a typical coal-fired thermoelectric plant that powers a medium-sized city produces something like 300 megawatts of power, or 150 times more.  So the Bloom Power system produces a great deal of power.)

You might consider this technology for your data center.  Although a diesel generator is probably cheaper if you consider that power outages are not that frequent, and you might not be large enough to require 200 kilowatts of power.