Electrical Generation Equipment
Electricity generated from fossil fuels such as coal and natural gas as well as nuclear and other sources by converting energy in these sources (through combustion) to heat energy that drives a gas or steam turbine or in a compression ignition engine such as those used in typical diesel fuel applications. Distillate (#1, #2) and residual fuel oils (#4, #6) are the petroleum-based fuels used to generate electricity and biodiesel and biodiesel blends would potentially be applicable as substitutes for them with these three technologies in the generation of alternative power as long as the biodiesel meets all applicable specifications for use in these technologies. The following table shows technologies (referred to as prime mover type) used in the US for electrical generation from petroleum fuels.
Gas Turbines (GT)
Gas turbines work in much the same fashion as a windmill by using the wind to pump water. Basically the fuel is pressurized into a heated, high pressure gas stream which is used to turn the turbine blades. This mechanical energy is transferred directly to a generator from which electricity is created. Over 90 million gallons of distillate and residual fuel oils was used in gas turbines at electrical generating facilities nationwide in 2011.
Steam Turbines (ST)
Steam turbines work in much the same way as a gas turbine, but from the initial heating of the fuel steam is produced, pressurized, and that pressurized steam is used to turn the blades on the turbine. Over 857 million gallons of both distillate and residual fuel oils were used in steam turbines in 2011.
Compression-ignition Engines (IC)
These engines are much the same as those used in conventional transportation applications (e.g., long-haul trucks) except they contain a generator after the rotary shaft of the engine to generate electricity. Distillate and residual fuel oils used in compression-ignition engines was more than 68 million gallons in 2011.
Combined Cycle Technologies (CA, CS, CT)
These engines/technologies differ from a normal gas or steam turbine in that they utilize the waste heat generated by one engine as an energy source for another engine. These technologies are more efficient than normal gas or steam turbines and will use less fuel, but are more expensive. A typical example of these would be a gas turbine burning a petroleum-based fuel in which has hot gas exhaust that could be used to heat water generating steam for use in a steam turbine. This is referred to as a Combined Cycle Gas Turbine (CCGT). Over 161 million gallons of both distillate and residual fuel oil was used in these three technologies in 2011.
Petroleum Use for Electrical Generation in the US – Applicability to Biodiesel
The following table presents the total amount of B100 that could potentially be utilized for electrical generation in the US annually from 2007 through 2011 (latest data available) and the five-year average by each prime mover type. These gallons are based on an equivalent amount of energy versus both distillate and residual fuel oils used. The original petroleum consumption amounts were derived from the US Department of Energy’s Energy Information Administration Electrical Power 923 forms.
This table presents information on just the distillate fuel oil portion of energy used in 2007 through 2011 and five-year average.
Download the complete annual state-level spreadsheets for 2007-2011 here.
The following table shows average annual amounts of B100 (gallons) for each electrical generating technology in each state for 2007 through 2011.
Biodiesel in the Renewable Fuel Standard
Currently (spring 2013) biodiesel used for electrical power generation is not eligible for participation in the current Renewable Fuel Standard and hence ineligible to receive RIN credits.
Biodiesel Use in Renewable Portfolio Standards
Renewable portfolio standards (RPS), also referred to as Renewable Electricity Standards, are policies designed to have a certain percentage of a state’s electricity generated from one or more qualified renewable resources. Which resources can and are being used is to some degree tailored to fit that states resource base (e.g., solar in Arizona). Across the US, twenty-nine (29) states plus the District of Columbia and two territories have some sort of RPS in place. Currently, no national RPS is in place. The following provides a display of which states have some sort of RPS in place, what the percentages of electricity generation from renewable resources is targeted to be, and future timeframe.
There are many renewable resources that can be used to help meet these mandates. The major qualifying renewable resources are solar, wind, geothermal, biomass, some types of hydropower, landfill gas, and municipal solid wastes. Not all renewable resources are eligible in certain states and biodiesel is only specifically mentioned by name in nine (9) states, but may be a qualifying resource in others under a general ‘biomass’ category. These nine states are: California, Hawaii, Illinois, Nevada, New Hampshire, New York, Rhode Island, Washington state, and West Virginia. A complete listing of each state and its individual provisions with respect to meeting RPS requirements can be found here.
In addition, some states have in place a renewable energy credit (REC) trading system in which an electricity producer that generates more of his power than he needs from one or more qualifying resources can “sell” the excess renewable energy to someone who doesn’t generate enough RPS-eligible renewable electricity. For more information on RECs, go to this website.
Case Studies of Biodiesel Use in Electrical Power Generation
Biodiesel has been and is currently being used for electricity generation, but applications are limited due to lack of extensive testing in “real-world” applications as well as prices of competing fossil fuels.
FM did extensive testing of B100 in one of their engines and approved B100 for use in it as long as they biodiesel consistently met the current ASTM specification. Applications of biodiesel in their engines included a DuPage county Illinois facility with a 1.5 MW generator engine, a facility in Story county, Iowa, and even in Alaska powering six 2.3 MW engines.
Hawaiian Electric Company, Inc. (HECO)
Hawaii has a clean energy initiative for a mandate of 70% by 2030 and 40% of Hawaii’s net electricity generation to be renewable energy based. Hawaii in 2009 initiated a Bioenergy Master Plan which was concerned with developing a roadmap for a state bioenergy industry in Hawaii and also looking at power generation driven by producing more of its energy needs from renewable resources due to high petroleum prices.
HECO first did a demonstration test in 2011 at Maui Electric Company on 12.5 MW Mitsubishi diesel engine generators. Initially, biodiesel was used for start-up for cleaner emissions and then successfully tested on 100% biodiesel. Currently HECO uses B100 in one of their 100 MW Siemens gas turbines (model SGT6-3000E) and was fully operational beginning November 2010. They use soybean-based biodiesel from Renewable Energy group with a two year biodiesel contract for between three to seven million gallons per year. Cecily Barnes, manager of biofuels for HECO states that the Siemens engine was commissioned for use on #2 diesel, all Siemens performance guarantees were based on that fuel, and biodiesel was added to the warranty, but must meet the OEM’s original fuel specifications which include specifications for vanadium, lead, barium, manganese, chlorides, different specifications for phosphorus, potassium, and sodium and as well as a specification for heat of combustion not contained in the current ASTM D6751. The same is true of other electrical generating manufacturers such as General Electric.
For more information on the HECO operation and Hawaii’s reasons for pursuing biofuels and renewable energy in general, please go to these documents (2 HECO PPT and pdf documents).
ASTM D2880 - 03(2010) Standard Specification for Gas Turbine Fuel Oils
Petroleum-based fuels in gas turbines need to meet strict specifications just as they do in compression-ignition engines with D975 the internationally-recognized standard for diesel fuel oils, D6751 for B100 as a blend stock with distillates, or D7467, the specification for diesel fuel oil and biodiesel blends of B6 to B20. The accepted ASTM specification for petroleum-based fuel oils for use in gas turbines is ASTM D2880 which is significantly different than each of the above three specifications.
Description of Gas Turbines Fuel Grades
Grade 0-GT includes naphtha, Jet B, and other light hydrocarbon liquids that characteristically have low flash point and low viscosity as compared with kerosine and fuel oils.
Grade 1-GT is a light distillate fuel oil suitable for use in nearly all gas turbines.
Grade 2-GT, which is a heavier distillate than Grade 1-GT, can be used by gas turbines not requiring the clean burning characteristics of Grade 1-GT. Fuel heating equipment may be required by the gas turbine depending on the fuel system design or ambient temperature conditions, or both.
Grade 3-GT may be a heavier distillate than Grade 2-GT, a residual fuel oil that meets the low ash requirements, or a blend of distillate with a residual fuel oil. Fuel heating will be required by the gas turbine in almost every installation.
Grade 4-GT includes most residuals and some topped crudes.
The following table are specifications contained in ASTM D2880 (http://www.astm.org/Standards/D2880.htm) and these would need to be compared to the relevant ASTM specifications (D396, D975 (up to 5% biodiesel), D7467, and D6751). In addition, there are trace metal limits of 0.5 mg/kg of fuel entering the combustor on vanadium (V), sodium plus potassium (Na + K), calcium (Ca), and lead (Pb) all of which are presently not in any of the four relevant biodiesel-related specifications.
Electrical Generation Equipment Manufacturers and Warranties
Major manufacturers of electrical generating equipment that utilize distillate and residual fuels in the US are:
Currently none of these warranty their equipment for B100 use or for blends although Fairbanks Morse did previously in 2007 as state above. The fuel input to the equipment (e.g., biodiesel and the blend) must meet all applicable standards for use in the equipment throughout its complete use cycle.