The following is a re-post of one I made on LinkedIn back in June 2014…
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Whenever I see a new scientific gadget, I am immediately interested. So when my company recently trumpeted the installation of a new fuel cell system to help with electricity production at our headquarters facility, I started reading the internal news post with a small bit of excitement. Unfortunately, being a open skeptic and a staunch believer in the scientific method, my initial interest quickly turned into a critical analysis of what I was reading and watching.The first few statements made by the manufacturer of the fuel cell system made me question my understanding of basic chemistry or at least my definition of a few words. I am not a Chemist, nor am I an expert in fuel cells, I just have a degree in EE with a minor in Physics. However, being an engineer I tend to work on the application of science to real world problems and while this topic seemed to touch more on classic Chemistry, that never keeps me from asking questions and learning more.
What was it that got me spun up? The claim that the manufacturer makes about the Bloom Energy Server [1]:
Next, an electrochemical reaction converts fuel and air into electricity without combustion.I found that to be a misleading marketing "fluff" statement at best; unsound scientific reporting or a down-right false statement at worst. A second comment on the page and in the video seemed to fit into the same fluff category:
The oxygen ions combine with the reformed fuel to produce electricity, water, and small amounts of carbon dioxide.
From my old-school understanding, combustion is an exothermic chemical reaction that always releases thermal energy and in some cases (like this) also releases energy in the form of free electrons (electricity) and/or light. Combustion is synonymous with burning in our modern lexicon which implies a flame; but in Chemistry, "combustion" is just an oxidizing reaction (or redox reaction). The chemical equation that both Bloom and Wikipedia [2] show is: CH4(g) + 2O2(g) → CO2(g) + 2H2O(g). When I perform this chemical reaction in my kitchen with a gas range, it is usually call "burning" by the general public or "combustion" by nerds like me.
There is no magic here: methane, natural gas, CH4(g) is oxidized or combusted (the “+ 2O2(g)” part), and gives off CO2(g) and water vapor. Both of these gasses happen to be "a greenhouse gas" one is a major and the other is a minor greenhouse gas. Try to guess which is major—of course, that is a separate discussion that I may cover in a later post. The amount of CO2 given off does not come from the method of generating the reaction. So the “small amount" of carbon dioxide byproduct is no different when Bloom uses a fuel cell to oxidize methane than when I use a stove-top burner to combust natural gas. Mole for mole, the amount of carbon dioxide created is the same when consuming equivalent amounts of methane. By the way, I am willing to bet the Bloom Energy Server consumes a whole lot more natural gas than I do in my kitchen.
My understanding of the most efficient form of fuel cell combustion is the Alkaline Fuel Cell (AFC) which uses the reaction 2H2 + 4OH- → 4H2O + 4e- or the even simpler Proton Exchange Membrane Fuel Cell (PEMFC) with the reaction 2H2 + O2→ 2H2O. These PEMFCs were used in the Apollo and Space Shuttle programs and they were capable of producing electricity at nearly a 70% efficiency level [3] [4] [5]. Unfortunately it takes a high level of industrial energy (jet engine-style compressor) to produce liquefied hydrogen. The combustion of liquid hydrogen still gives off a greenhouse gas (water vapor) as a byproduct of the reaction, but there is no "nasty" CO2. This chemical process allows hydrogen to act as a nice battery—a method of storing a portion of that same industrial energy it took to produce. However, the inefficiencies in the production and the difficulty of storing hydrogen have not been solved to the extent that makes hydrogen fuel cells marketable to the public, thus our reliance on hydrocarbon versions.
It may be fair for Bloom to argue that their system is more efficient at using a chemical reaction in a thermal cycle to produce electricity versus using the intermediate mechanical stage common in power plant-generated electricity, but it is not valid for them to claim it works without combustion. The efficiency argument is also scientifically questionable from my perspective. Our modern power industry can squeeze every bit of efficiency out of their plants by benefiting from scales of production. I assume Bloom must convert the DC electricity in their Server to AC line voltage (at three phases for industrial use?) which is inherently an inefficient process. Just for a comparison I found a table on Wikipedia [6]... Bloom claims over 60% efficacy, which as noted in the link, is pretty close to that of a “gas turbine plus steam turbine” (natural gas power plant). Economic and market games played by the electric utilities to convince consumers when best to place their load onto the grid (peak demand charges) is different than electricity production and transmission efficiencies. Thus, this new on-site power generator may be a good deal for my company, but not because of any magic with hydrocarbon-based electricity production.
If Bloom's customers are hoping to get an independent power source, controlled on-site, and driven by an alternative fuel, then this new fuel cell system seems to be a reasonable investment and should stand on those merits. However, I am not convinced this technology is any “greener”, nor more efficient, and I doubt it costs any less in the long run (a 100kW installation has an estimated cost of $700k-$800k [7]). In my mind this new fuel cell system may help to reduced the chance of a blackout or brown-out occurring on a business campus since it allows electricity to be generated on-site. However, it is still dependent on a utility, it just happens to be a natural gas provider rather than an electricity provider.
"Skeptic" is not a bad word in my dictionary, in fact I feel it embodies what we need more of today. The founder of Maxim, Jack Gifford had a set of principles that he lived by and founded the company on [8]; one of those was:
One of my personal principles is to not be a hypocrite and thus I try to keep an open mind, ready to change if I can be convinced with a sound, logical argument without fallacy. I may have the facts wrong, so please feel free to point out where I have misinterpreted the science. I am willing to be led through the description of a newly found "energy source” like the Bloom Energy Server, and maybe they will read this post and help lead me to a better understanding. However, the laws of Physics, Chemistry, and Thermodynamics often make it difficult to find a free lunch, even with a good guide.
The following are my references for the above text:
[1] http://www.bloomenergy.com/fuel-cell/solid-oxide-fuel-cell-animation/
There is no magic here: methane, natural gas, CH4(g) is oxidized or combusted (the “+ 2O2(g)” part), and gives off CO2(g) and water vapor. Both of these gasses happen to be "a greenhouse gas" one is a major and the other is a minor greenhouse gas. Try to guess which is major—of course, that is a separate discussion that I may cover in a later post. The amount of CO2 given off does not come from the method of generating the reaction. So the “small amount" of carbon dioxide byproduct is no different when Bloom uses a fuel cell to oxidize methane than when I use a stove-top burner to combust natural gas. Mole for mole, the amount of carbon dioxide created is the same when consuming equivalent amounts of methane. By the way, I am willing to bet the Bloom Energy Server consumes a whole lot more natural gas than I do in my kitchen.
My understanding of the most efficient form of fuel cell combustion is the Alkaline Fuel Cell (AFC) which uses the reaction 2H2 + 4OH- → 4H2O + 4e- or the even simpler Proton Exchange Membrane Fuel Cell (PEMFC) with the reaction 2H2 + O2→ 2H2O. These PEMFCs were used in the Apollo and Space Shuttle programs and they were capable of producing electricity at nearly a 70% efficiency level [3] [4] [5]. Unfortunately it takes a high level of industrial energy (jet engine-style compressor) to produce liquefied hydrogen. The combustion of liquid hydrogen still gives off a greenhouse gas (water vapor) as a byproduct of the reaction, but there is no "nasty" CO2. This chemical process allows hydrogen to act as a nice battery—a method of storing a portion of that same industrial energy it took to produce. However, the inefficiencies in the production and the difficulty of storing hydrogen have not been solved to the extent that makes hydrogen fuel cells marketable to the public, thus our reliance on hydrocarbon versions.
It may be fair for Bloom to argue that their system is more efficient at using a chemical reaction in a thermal cycle to produce electricity versus using the intermediate mechanical stage common in power plant-generated electricity, but it is not valid for them to claim it works without combustion. The efficiency argument is also scientifically questionable from my perspective. Our modern power industry can squeeze every bit of efficiency out of their plants by benefiting from scales of production. I assume Bloom must convert the DC electricity in their Server to AC line voltage (at three phases for industrial use?) which is inherently an inefficient process. Just for a comparison I found a table on Wikipedia [6]... Bloom claims over 60% efficacy, which as noted in the link, is pretty close to that of a “gas turbine plus steam turbine” (natural gas power plant). Economic and market games played by the electric utilities to convince consumers when best to place their load onto the grid (peak demand charges) is different than electricity production and transmission efficiencies. Thus, this new on-site power generator may be a good deal for my company, but not because of any magic with hydrocarbon-based electricity production.
If Bloom's customers are hoping to get an independent power source, controlled on-site, and driven by an alternative fuel, then this new fuel cell system seems to be a reasonable investment and should stand on those merits. However, I am not convinced this technology is any “greener”, nor more efficient, and I doubt it costs any less in the long run (a 100kW installation has an estimated cost of $700k-$800k [7]). In my mind this new fuel cell system may help to reduced the chance of a blackout or brown-out occurring on a business campus since it allows electricity to be generated on-site. However, it is still dependent on a utility, it just happens to be a natural gas provider rather than an electricity provider.
"Skeptic" is not a bad word in my dictionary, in fact I feel it embodies what we need more of today. The founder of Maxim, Jack Gifford had a set of principles that he lived by and founded the company on [8]; one of those was:
question everything and everybody...caveat emptor; be a skeptic. These are wise words.
One of my personal principles is to not be a hypocrite and thus I try to keep an open mind, ready to change if I can be convinced with a sound, logical argument without fallacy. I may have the facts wrong, so please feel free to point out where I have misinterpreted the science. I am willing to be led through the description of a newly found "energy source” like the Bloom Energy Server, and maybe they will read this post and help lead me to a better understanding. However, the laws of Physics, Chemistry, and Thermodynamics often make it difficult to find a free lunch, even with a good guide.
The following are my references for the above text:
[1] http://www.bloomenergy.com/fuel-cell/solid-oxide-fuel-cell-animation/
