The cleanest fuel cells convert hydrogen and oxygen into heat and electrical current, releasing water as exhaust. Microsoft, though, used more convenient methane-powered fuel cells, which release more pollutants, but not as much as natural gas combustion, according to Microsoft's study on using fuel cells to power a datacenter (PDF). "In the new datacenter design approach outlined in our paper, chemical energy is first converted to direct current electrochemically and sent a few feet to the server power supply. With our one watt of [initial] energy we are now getting almost 0.4 watts, or double the efficiency of traditional datacenters," James said.
The approach not only avoids inefficiencies of electrical power distribution, but also improves reliability since battery backup isn't required, the researchers said. For companies like Microsoft, Facebook, and Google that rely on datacenters crammed with thousands of servers, a tiny increase in efficiency can pay off. Microsoft thinks the fuel cells could make datacenters cheaper to build, too. "If the fuel cells are placed close to power consumption units, at the servers or racks, we can completely eliminate the power distribution system in the datacenter, including the power backup generation system. So, no datacenter wide electrical infrastructure is required. This is over 25 percent of the capital cost for state-of-the-art datacenters," the paper said.