Saturday, December 26, 2009

Banter With Blair

Blair an avid Green Explored reader who is also a chemical engineer like me, wrote the following comment about my last blog that Americans get overcharged.


How efficient is oil as an energy source for autos? Step 1: A supertanker consumes an average of 30,000 barrels of heavy fuel oil to transport 2,000,000 barrels of crude oil from Jeddah, Saudia Arabia to the West Coast or the Gulf of Mexico in the US. 2,000,000 – 30,000 = 1,970,000 barrels. Step 2: According to the NAICS, almost 20% of the fuel energy consumed in the US in 2002 was by oil refineries. Though the actual amount of energy required to refine oil into gasoline is less than 20%, the fact remains that 20% of the energy that goes into the refinery will not be leaving the refinery. 1,970,000 x 80% = 1,576,000 barrels. Refineries process 50% of their crude oil into gasoline and the rest into diesel fuel, heating oil, and other petroleum products. 1,576,000 x 50% = 788,000 barrels of gasoline. Step 3: The overwhelming majority of refineries are located on the coasts or borders of the US. Therefore, to get gasoline to consumers, it must be trucked from refineries to wholesalers/retailers (gas stations). A diesel tanker truck requires 250 gallons of diesel to transport 9,000 gallons of gasoline the average distance (1,500 miles roundtrip) from a refinery to a gas station. So, another 3% is “lost”. 788,000 barrels x 97% = 764,360 barrels remain. That’s 38% of the original total. The cost of gasoline “at the pump” is irrelevant. The thermodynamics of hydrocarbon combustion compared to other energy sources is moot. It doesn’t matter where you stand on the issues of global climate change or auto exhaust air pollution. The fact is using oil as an energy source to power automobiles is incredibly inefficient. Raising CAFE standards will not raise that 38% efficiency figure. We have to come up with something better.

Well Blair it is back to thermo 101 for you. Step 1 you are correct the super tanker will use about 1% of the oil it carries. Step 2 there is no way on God’s green earth that oil refineries consumed 20% of all the fuel energy of the USA. In fact refineries put out more barrels of product than incoming product as there is this thing called “processing gain” that comes about because the refined product is less dense than the crude so if you remember mass balance methodology there is an increase in volume of “lighter” less dense material for a given mass. The US DOE reports processing gain at about a million barrels a day or about 5% of the total usage of oil. See http://www.eia.doe.gov/pub/oil_gas/petroleum/data_publications/weekly_petroleum_status_report/current/txt/table1.txt

Of course the refinery does need electricity (often self generated), steam (often self generated) and hydrogen for the refining process so there is some loss of energy (not barrels). Here is a wiki article for the well to the gas station analysis for oil and it puts the value as a 17% loss (ie 83% of the energy is in the gasoline that was in the crude in ground). http://en.wikipedia.org/wiki/Life_cycle_assessment

OK so let’s live with this wiki number even though I believe it is more like 90% of the energy that remains. You magically lost the energy in the other products like diesel fuel, jet fuel in you calculation. This energy is not lost in the refining process it is used for other purposes. So you cannot suddenly say that the gasoline has to bear this loss. That calculation my friend is like counting backward from ten on the fingers of your one hand. You go ten, nine, eight, seven, six going from your thumb to your pinkie and then you say add my five other fingers and I have eleven fingers (a trick I learned when I was four). I got the other kids in kindergarten to believe they had eleven fingers.

For the electric power alternate we have a natural gas extraction and distribution at 95% efficiency, power generation station at 50% efficiency, transmission and distribution at 97% efficiency, inverting AC to DC for battery charge at 90% efficiency and, charge discharge efficiency of lead acid batteries at 60% for a complete cycle efficiency of 24.8% . Using the wiki wells to station efficiency of 83% and the Prius’ engine efficiency of 30% as the engine is running optimally we have the very same 24.9% well to wheels efficiency of the heavy metal car. Without the 500 pounds of batteries the lighter Prius will get better energy efficiency (Newton’s laws of motion). Blair I hope this lesson in “processing gain” helps you understand the dumbness of your Bezerkley friends and alumni. Have a great new year and let’s meet up for coffee even if you drive an electrified Hummer

6 comments:

  1. Lindsay, once again your bias has blinded you to the obvious. First, it is not a question of thermodynamics. The 1st and 2nd law make "processing gains" a fiction. The fact remains that only 16 gallons of gasoline are produced from the 42 gallons of crude oil in each barrel. It doesn't matter how much "energy" is contained in a barrel. It only matter how much is made available to AUTOMOBILES. Crude oil for heating oil, jet fuel, diesel, fertilizer, etc. maybe great but to continue relying on it for AUTOMOBILES is DUMB. Using your juvenille rationalization, we should work on developing nuclear power plants for autos. Batteries, fuel cells, hamster wheels may not be the answer but crude oil to power AUTOMOBILES in the 21st century is DUMB.

    ReplyDelete
  2. OK Blair you now are sent back to high school as you did not understand first year engineering explained in its simplest form. What about diesel cars In Europe half of the cars are diesel so do they get more than 16 gallons out of 42 in Europe. If you would just take a look at the DOE link I gave you only 13,837,000 barrels of crude and 764,000 barrrels of products were imported Add them and you get 14,601,000 barrels of crude and products into the system. Out came 8,991,000 barrels of gasoline, 1,464,000 barrels of jet fuel, and 3,670,000 of diesel distillate for a total of 14,125,000 of transportation fuel. This is not 16 out of 42. Not even the leftist math you learned counting backwards could yield such an answer. You are so blinded by the leftist nonsense in Half Moon Bay that your brains have become mushy and I may have to call the place Half Wit Bay. Of course we will rely on hydrocarbons for the next fifty years to propel vehicles because of one simple reason. They work. Don't cry when electricty costs 30 cents a kilowatt hour for your last tier of electricity you buy from PG&E. You voted for the idiots in Sacramento and love their "low carbon fuel" nonsense. Low carbon fuel is just a bunch of criminal academics from the two schools you attended. Davis and Bezerkeley. I am proud that I studied thermo in Iowa where folks still know how to light a fire

    ReplyDelete