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Reciprocating Engines (Generators)

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A reciprocating engine for power generation in Haiti. (Photo:Walt Ratterman)

Reciprocating Engines (small generators) are the most common form of small generator. In generator-only systems, the generator must be sized to handle the peak expected load, but the system frequently runs at lower loads at reduced efficiency. It is common to find oversized generators at many development country health facilities. Running an oversized generator is expensive and inefficient and should be avoided.


Cost Considerations

Engine generators typically have low capital cost compared to other alternatives, but higher operating costs due to the need for fuel. Initial capital cost will be approximately $2,000 for 2.5 kW, varying with the size and type of generator. Operating costs will vary depending on the level of usage. Engines do offer economies of scale in increasing sizes, but utilizing a few smaller units is generally preferred. This allows cycling of the generators for maintenance, and allows the use of one or two units at full load rather than a larger unit at reduced load. A battery bank can also be added to a generator-based system to reduce run time and save fuel costs.

Maintenance Considerations

Engine oil and the oil filter should be changed after approximately 1,000 hours of operation. The engine head may need to be rebuilt after 8,000 hours, and the engine block after 16,000 hours. Facility personnel can examine the generator daily for fuel, oil, or coolant leaks. The area in the vicinity of the generator should be kept free of any debris that could pose a fire hazard or make access difficult. Oil and coolant levels should be checked weekly. More in-depth monthly, semi-annual, and annual maintenance checks should be performed by professionals. In some cases, spare parts for generators may be difficult to obtain.

Fuel Options

Diesel is the most common option for generator fuel. Diesel engines tend to be more expensive than gasoline generators, but also more reliable and longer-lived. The fuel does not burn as cleanly as propane or biogas. Gasoline generators are cheaper than diesel generators and available in smaller sizes. They are normally used as emergency back up generators due to their shorter operating lifetimes. Propane, where available, lends itself to generators that are quieter, cleaner, and environmentally safe; spilled propane evaporates rather than contaminating a site. Propane generators are well-suited to use in a hybrid system with solar or wind, though they are not optimal for serving as the sole (or primary) energy source. Propane may also be used to run a refrigerator directly.

Lessons Learned

  • Generators are frequently sized incorrectly at health facilities. It is very inefficient to operate an oversized generator. Replacing an oversized generator can often be the most cost effective intervention to reduce energy costs at a health facility.
  • Donor provided generators are often provided without consideration of installation fees and maintenance protocols. Poor installation (e.g. using small wires) often leads to poor generator performance (e.g. low voltage at loads)
  • For larger facilities, consider separating critical from non-critical loads so a smaller generator can be used for continuous service of the critical loads and save fuel costs.

Additional Resources

These are links to external publications and Web sites that have information on issues related to providing reliable electricity and energy services at health facilities. USAID and Powering Health make no warrantee or guarantee regarding these external resources, and the organizations hosting these resources are solely responsible for their content.


Technology Characterization: Reciprocating Engines, developed for the U.S. Environmental Protection Agency by the Energy Nexus Group, Feb 2002 (PDF 249K).

Reciprocating internal combustion engines are a widespread and well-known technology. North American production exceeds 35 million units per year for automobiles, trucks, construction and mining equipment, marine propulsion, lawn care, and a diverse set of power generation applications.

Generator Sizing, SunEnergy Power International, May 2008 (PDF 438K).

Typical Back-up Generator Configuration, Likely Health Center Load Profile, Sizing the Generator, Generator Alone Sizing Result, Power for Inverter / Batteries, Charging the Batteries, Generator Run Time with Batteries, Generator Fuel Consumption, The rising cost of Fuel.

Generator Configurations, SunEnergy Power International, May 2008 (PDF 350K).

Typical Back-up Generator Configuration, Emergency Loads Only, Add Inverter/Batteries, Add other Emergency Loads, Whole facility generator plus the inverter/batteries, Stand-by vs. Primary Power.

sepi haiti gen 3p

Generators Three Phase vs. Single Phase, SunEnergy Power International, May 2008 (PDF 301K).

Power Generator Formulas, Amperage of 3 Ph Generators, Amperage of 1 Ph Generators, Compare 3 PH to 1 PH, Examples, The result, Other likely Scenarios, Discussion Topics.

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