Solid Oxide Fuel Cells And The Bloom Box

Navid Chowdhury
December 7, 2011

Submitted as coursework for PH240, Stanford University, Fall 2011

Fig. 1: Schematic of a Solid Oxide Fuel Cell. Source: Wikimedia Commons


Distributed Generation (DG) is the idea of generating power on site at the point of consumption (rather than at a central power grid) and it is becoming more and more essential at both commercial and household level. It allows its user the flexibility and control that commercial power grid does not. But more than that, it is the high efficiency and low transmission cost (and loss) that's beginning to drive its cause. In the past, DG's mainly referred to combustion generators that burnt mostly diesel to generate power. But as the campaign for greener energy sped up in the last couple of decades new DG systems have been introduced in the market. Fuel cell was the result of that drive for greener DG system. Fuel cells are devices that convert chemical energy in fuels (usually hydrocarbon) to electricity in an electrochemical reaction. Great thing about fuel cells is that although it burns fossil fuel, it barely emits any greenhouse gas unlike most fossil fueled energy sources. Fuels cells come in different types/design and the one that I am going to talk about today is the Solid Oxide Fuel Cell (SOFC).


SOFC works the same way as most fuel cells do but instead of a solvent electrolyte it uses a solid electrolyte. Usually the electrolyte is some kind of a ceramic material; most commonly it comes in the form of Yttria stabilized Zirconia (YSZ) or as Scandia stabilized Zirconia (ScSZ). [1,2] The material used for the electrolyte is very important as it defines the efficiency and the performance of the SOFC.

At the cathode, oxygen from the air is split into oxygen ions and free electrons. The oxygen ions travel through the solid electrolyte to the anode where it is oxidized with hydrogen from the fuel supplied. This reaction at the anode releases free electrons which then enters the circuit (connected to the cell) and generate electric power. Besides electrons, the reaction at the anode also releases heat and some water as byproduct. The whole process operates at a very high temperature; roughly between 500 and 1000 degree Celsius. [1] The high temperature results in high cost as the materials that make up the system need to have high tolerance for high temperature conditions.. The benefit, on the other hand, of the high temperature is that there is no need for any kind of catalysts to trigger/speed up the reaction.

SOFC's are usually stacked together in series to generate power in quantities useful households and commercial institutions. The fuel used for SOFC's could range from light hydrocarbons like methane, propane and butane to heavy hydrocarbons like gasoline, diesel and jet fuel. [3] In the case for light hydrocarbons, the high temperature of the system helps in internally reforming them while the heavier hydrocarbons need to be reformed externally. Reforming the heavier hydrocarbon is an exothermic reaction and the heat generated in the process could be used to maintain the high temperature of the sysem. [1].

Bloom Energy Server

Bloom Energy server or most commonly known as the "Bloom box," is tipped as the "next generation" SOFC. [2] It was invented by the company called Bloom Energy, which was founded in 2002, based on extensive research work done on SOFC's by its founder at NASA. Since its unveiling the Bloom box has created a major hype in the clean energy industry for its "secret technology" that would revolutionize the DG power systems. Most of its high profile first adopters are already lauding it for its cost cutting technology and unprecedented efficiency.

Bloom Energy fuel cell uses a special ceramic material that the company secretively calls "common sand like powder" for its solid oxide electrolytes. According to Bloom Energy each of their fuel cell can generate an average power of 25 W, which is enough for a light bulb. Stacked together, a bunch of fuel cells could power an average home. Multiplying the size of the stack could multiply the power derived and could therefore be utilized for large scale commercial purposes

The first commercial installation of a bloom energy server was made in July 2008 when a 100 KW bloom box was installed at the Mountain View campus of Google. A few more high profile adopters followed suit, with installations made at eBay, Wal Mart and Coca-Cola. The high profile first adopters were another reason why Bloom box received so much attention in the media as it did(CBS ran a 60 min documentary on the Bloom Energy). But the big name clients aside, bloom box is yet to reach out to the general households where it is said deemed to have its greatest impact. The obstacle it needs to overcome before it does so is cut its extremely high capital cost. The cost of setting up a bloom box is currently in the range of $700,000, which is way too high to be competitive in the current energy market. [4]


Bloom Energy founder K Sridhar has repeatedly emphasized that the eventual goal for his company is to make bloom energy severs available at a low affordable cost for individual households. To that end Bloom energy has already come up with a new program where consumers in California could chose not to bear the installations cost and just buy the electricity generated by the energy servers. Bloom Energy would own the servers and be responsible for its maintenance while the consumer would just pay for the electricity (which would be at a cost lower than the current "per KWH" cost offered by California power grid). Although this plan garnered a lot of praise in the media there were still some skeptics who doubt the hype around the company. Some call bloom box the next "Segway" while others are skeptic of its business plan as Bloom energy is yet to reveal its operation cost per KWH of energy generated. [4] Only time will tell if bloom box is the energy solution we were looking for or if it is just another overhyped Silicon Valley startup.

© Navid Anjum Chowdhury. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] A. Nakajo, "Electrochemical Model of Solid Oxide Fuel Cell for Stimulation at the Stack Scale," J. Electrochem. Soc. 158, B1102 (2011).

[2] S. Ashley, "Next Generation Flex-Fuel Cells Ready To Hit The Market," Scientific American, 18 Nov 11.

[3] C.H. Steele and A. Heinzel, "Materials for Fuel Cell Technologies," Nature 414, 345 (2001).

[4] P. Keegan, "Bloom Box: Segway or Savior," Fortune, 23 Feb 10.