I had a little free time so I navigated the Bloom Energy web site. A pretty nice website that is easy to navigate. Bloom no doubt spent a good deal of time and money to develop the site. One of the links on the site is the data sheet for the 100 kilowatt bloom energy server. My assumptions in my earlier blog (the bloom is off the rose) estimating their technology was spot on. Their Bloom Box is a solid oxide fuel cell with about an efficiency of converting natural gas to electricity of approximately 50%. The one data point in their data sheet I firmly disagree with Bloom is on the amount of carbon dioxide emissions from the device. Here is the link to their data sheet http://www.bloomenergy.com/products/data-sheet/ In the data sheet Bloom claims a rate of carbon dioxide emissions of 773 pounds per megawatt hour of power generation. This equates to 0.773 pounds of CO2 per kilowatt hour of power generation as a megawatt hour equals 1,000 kilowatt hours. Bloom also lists a heat rate of 661,000 BTUs per 100 kilowatt hours of net power generation.
Heat rates are listed in terms of the lower heating value of the fuel. In simple terms when one burns fuel with air one gets carbon dioxide and water that are both in the vapor phase. Makes sense as the gases going up the chimney are hot and certainly above the boiling point of water. When the utility sells you natural gas they cleverly measure the fuel value at the higher heating value where all the energy in fuel can be extracted provided that the water produced and going up the chimney is liquid water. Of course by adding the energy gained by condensing the steam to liquid water the fuel has more value. Simply put the utilities invented this higher heating value so they could charge their customers about 10% more per cubic foot or pound of natural gas they sell. An engineer at Bloom must have used this higher heating value of natural gas to calculate the carbon dioxide emissions from their energy server. I investigated the actual chemical composition of natural gas that the utility in Northern California (PG&E) sells and using the stated heat rate of 661,000 BTUS per 100 kilowatt hours I calculated the Bloom Box emits 0.856 pounds per kilowatt hour. This is some 10.7% higher than Bloom’s stated amount of emissions. For comparison the average kilowatt hour of electricity generated in California for the entire year 2008 had only 0.724 pounds of carbon dioxide emissions. This fact alone proves it is greener to buy your electricity from PG&E rather than installing an onsite Bloom Box.
The calculation of carbon dioxide emissions is pretty fundamental but I am not surprised that Bloom tried to pull another fast one on us. I wrote the following email on March 10 to Bloom at firstname.lastname@example.org blog on their technology. Of course there was no reply. I bet you they change the data sheet one night when no one is looking. I was smart enough to save and print the pdf version that was originally on their site. Perhaps the man who invented the internet is also the man who is now giving us low carbon natural gas? The whole message behind Bloom is they are the low carbon emission method to generate electricity. Maybe 60 minutes should be called 54 minutes, the last 6 minutes with Andy Rooney is pointless anyway. Actually the show is so bad these days it should just be 30 minutes and they should get rid of Lesley who has Stalled like a Pontiac. Her report on Bloom was a GTO (getting tricked often). The Green Machine has given his opinion that this Bloom is one stinking rose. Perhaps Alfalfa should try sell the system in Gilroy, the garlic capital of the world. Alas Gilroy is in PG&Es service territory so old Al should go home to Tennessee where they burn coal and emit 1.5 pounds of carbon dioxide for each kilowatt hour. Al please take Arnie with you as head east.
Sent: Wed, Mar 10, 2010 5:00 pm
Subject: Bloom Box CO2 Emissions
I have looked at your data sheet. You claim an energy input of 661,000
BTU per hour for your 100 kw unit. I take it this is LHV (lower
heating value). You also claim a CO2 emission rate of 773 lbs per mega
watt hour. I am a chemical engineer and my grad work was in
thermodynamics. I have performed a heat and mass balance using the
published data for the natural gas sold by PG&E in California and have
calculated that using your heat rate LHV and PG&Es gas composition the
CO2 emissions are 856 pounds per mega watt hour. I do believe the
person who calculated your carbon dioxide emissions used the HHV of
natural gas. But I feel pretty certain that your stated heat rate of
661,000 BTU per 100 kwh is LHV.
Can you please check your calculations and get back to me?