GENERATOR FUEL - WHAT GENERATOR FUEL IS BEST?
There are many advantages and disadvantages to different types of fuel. Nearly all Generators use either gasoline, diesel, natural gas or propane. The following information will hopefully answer any questions or concerns you may have concerning different fuel sources. Some general features of the generator itself influence purchase decision. Where possible we indicted hardware and environmental differences in generator set types. You should consider all the factors shown. POSITIVE, NEGATIVE, GENERATOR FACTORS, are shown by the color of the features.
Gasoline:
* Advantages:
o Common fuel source - easily obtained
o Increases portability of smaller generators
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* Disadvantages:
o Highly flammable
o Short shelf life of fuel (approximately 12 months)
o Storing large quantities of fuel is hazardous
o May not be available during power outages
o Somewhat expensive fuel, check your local prices
o Inefficient
Diesel:
* Advantages:
o Least flammable fuel source
o Fuel easily obtained (fuel is easier to obtain during a disaster because it is a necessary fuel for the military, trucking industry, and farming operations)
o On site fuel delivery available
o Engine life for liquid-cooled 1800 RPM engines can approach 20,000 hours if properly serviced depending on the application and environment.
o High speed 3600 RPM diesel engines normally have a 10,000 to 15,000 hour life expectancy with proper maintenance and service under most conditions
o Less expensive to operate. The general rule of thumb for fuel consumption is 7% of the rated generator output (Example: 20 kW x 7% = 1.4 gallon per hour at full load).
o Designed for off-road applications and can operate on dyed or farm/construction diesel fuel which is sold without the road tax and thus is considerably cheaper to purchase.
o Engines designed to work under a load for long periods of time and perform better when worked hard rather than operated under light loads.
o Can operate in sub-artic conditions with fuel additive.
o Equipment is competitively priced for a comparative sized water-cooled gaseous models with the same features.
o In high use situations overall long term cost of operation is much lower than gaseous GenSets.
Diesel Fuel Use Chart
* Disadvantages:
o 18-24 month shelf life, without additives
o Installing large storage tanks raises cost of system
o May not be available during power outages.
o Diesel fuel storage must be considered relative to required run time in your geographical area. If you live in hurricane country you might need a large fuel tank due to the high possibility of extended power outages
o Engine noise is higher on a diesel compared to a gaseous engine. Use of a properly designed enclosure and sound attenuation system is more critical on a diesel engine system.
o Subject to "wet stacking" or over fueling if run for long periods of time with ultra light loads (less than 40% of the rated output). "Wet Stacking" causes the engine to smoke and run rough because the injectors become carbonized. Running a heavy load will usually clean up the over-fuel condition and allow the engine to perform normally. Diesel engines operate better and are more fuel efficient when loaded (70-80% is optimum).
o In sensitive emission areas in some states diesel engines are prohibited from operating over a prescribed number of hours per year to help reduce pollution levels
o Requires clean moisture free fuel and a bit more maintenance than a comparable gaseous unit;
o Some cities and counties require the generator on-board fuel tanks to be double-wall containment type which can increase the cost of the generator system.
o Typically heavier and require more planning to load and unload than a lightweight gaseous GenSet.
Bio-Diesel:
* Advantages: (Same as Diesel see above)
o Least flammable fuel source
o Easily obtained
o On site fuel delivery available
Bio-Diesel is a cleaner-burning diesel replacement fuel made from natural, renewable sources such as new and used vegetable oils and animal fats. Like petroleum diesel, Bio-Diesel operates in compression-ignition engines. Blends of up to 20% Bio-Diesel (mixed with petroleum diesel fuels) can be used in nearly all diesel equipment and are compatible with most storage and distribution equipment. These low level blends (20% and less) don't require any engine modifications and can provide the same payload capacity as diesel. Using Bio-Diesel in a conventional diesel engine substantially reduces emissions.
* Disadvantages: (Same as Diesel see above)
o 18-24 month shelf life, without additives
o Installing large storage tanks raises cost of system
o May not be available during power outages
o Obtaining oils and other fuels.
o Mixing and maintaining proper percentage of oils/fuel
Emulsified Diesel:
* Advantages: (Same as Diesel see above)
o Least flammable fuel source
o Easily obtained
o On site fuel delivery available
This is diesel that is mixed with a small percentage of water and an agent that keeps the water and diesel mixed. By adding the water to the diesel a smaller amount emissions are created when the fuel is burned.
* Disadvantages: (Same as Diesel see above)
o 18-24 month shelf life, without additives
o Installing large storage tanks raises cost of system
o May not be available during power outages
o Obtaining oils and other fuels
o Mixing and maintaining proper percentage of water/fuel
Propane:*
*See propane notes below.
* Advantages:
o Long shelf life
o Clean burning
o Easily stored in both large tanks or in smaller 5 - 10 gallon cylinders
o Obtainable during power outages - gas stations may be unable to pump fuel during an area wide outage
o Home delivery available for larger tanks
o Quieter engine noise level
o More emission compliant
o Gaseous engines do not have a problem with "wet stacking like diesels
o Less expensive units with air-cooled engines are budget priced.
o Engine life for liquid-cooled 1800 RPM engines can approach 5,000 to 6,000 hours on industrial quality gaseous GenSets
* Disadvantages:
o Pressurized cylinder of flammable gas
o Fuel system is more complicated (increased possibility of failure)
o Larger tanks are not aesthetically pleasing (unsightly)
o Fuel system plumbing results in higher installation cost
o Somewhat expensive fuel, check your local prices
o Propane can become very dangerous if lines are broken.
o Propane begins to derate around -20 degrees above zero
o Initial cost of generator is somewhat higher, 15 to 20% especially in sizes larger than 30 kW.
o More expensive to operate by as much as 3-times the fuel consumption compared to diesels;
o Shorter life expectancy by a factor or 10 to 1for air-cooled models and 3 to 1 for water-cooled models compared to diesel powered GenSets
o Smaller air-cooled gaseous engines are less expensive than comparable diesels but have a short life expectancy as low as 500-hours depending on engine make and use
o Shorter life than diesel engines
Natural Gas:
* Advantages:
o Unlimited fuel source - refueling not necessary
o Clean burning
o More available during power outage.
o Quieter engine noise level
o More emission compliant
o More convenient fuel source (natural gas)
o Gaseous engines do not have a problem with "wet stacking like diesels
o less expensive units with air-cooled engines are budget priced.
Natural gas is a mixture of hydrocarbons (mainly methane (CH4)) and is produced either from gas wells or in conjunction with crude oil production. Because of the gaseous nature of this fuel, it must be stored onboard a vehicle in either a compressed gaseous state (CNG) or more commonly as liquefied state (LNG).
* Disadvantages:
o May be unavailable during natural disasters (earthquakes, etc)
o Lower power output (30% less BTU's per unit than gasoline.
o Fuel system plumbing results in higher installation cost.
o Fuel not available in many areas.
o Natural gas (NG) begins to derate at +20 degrees above zero.
o Initial cost of generator is somewhat higher, 15 to 20% especially in sizes larger than 30 kW.
o More expensive to operate by as much as 3-times the fuel consumption compared to diesels;
o Shorter life expectancy by a factor or 10 to 1for air-cooled models and 3 to 1 for water-cooled models compared to diesel powered GenSets
o Smaller air-cooled gaseous engines are less expensive than comparable diesels but have a short life expectancy as low as 500-hours depending on engine make and use.
o Hurricanes and earthquakes can disrupt the flow of natural gas lines with up-rooted trees
o Natural Gas can become very dangerous if lines are broken.
