10315 Fuel Considerations

Since not all fuels can be used with every technology, fuel can also dictate fixed costs as shown in Table 10.3.

TABLE 10.3

Cost Comparison for CHP Fuels

Fuel Type

Installed Cost

Fuel Cost

O&M Costs






Natural gas Petroleum Waste heat Biomass

Low Medium

Zero Low




A potential system issue for gas turbines is the supply pressure of the natural gas distribution system at the end user's property line. Gas turbines need minimum gas pressures of about 120 psig for small turbines, with substantially higher pressures for larger turbines. Assuming there is no high-pressure gas service, the local gas distribution company would have to construct a high-pressure gas line or the end user purchase a gas compressor. The economics of constructing a new line must consider the volume of gas sales over the life of the project.

Gas compressors may have reliability problems, especially in the smaller size ranges. If black start capability is required, then a reciprocating engine may be needed to turn the gas compressor, adding cost and complexity. Reciprocating engines and fuel cells are more accommodating to the fuel pressure issue, generally requiring under 50 psig. Reciprocating engines operating on diesel fuel storage do not have fuel pressure as an issue; however, there may be special permit requirements for on-site fuel storage.

Diesel engines should be considered where natural gas is not available or very expensive. Diesel engines have excellent part-load operating characteristics and high power densities. In most localities, environmental regulations have largely restricted their use for CHP. In California and elsewhere in the U.S., diesel engines are almost exclusively used for emergency power or where uninterrupted power supply is needed, such as in hospitals and critical data operating centers. As emergency generators, diesel engines can be started and achieve full power in a relatively short period of time.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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