523 Applications

The two-shaft microturbine can be used in a variety of applications because of the flexibility inherent in its direct mechanical drive capability. Figure 5.7 shows the possible combinations of shaft power/thermal power applications. The most commonly discussed application for MTs today is for cogen-eration wherein the turbine drives an electric generator. As shown in Figure 5.6, an additional heat exchanger built into the exhaust stream is typically used to heat water for either space heating or domestic hot water service. In a cogeneration application that can effectively use the waste heat, overall system efficiency can be quite high (80% or more). The system can be designed to provide a variable heat recovery output to accommodate the

FIGURE 5.7

Application matrix for a two-shaft microturbine.

FIGURE 5.7

Application matrix for a two-shaft microturbine.

specific heat requirements of the facility over time. This includes running the MT at full power output with a zero heat load if necessary.

In another two-shaft MT application, the power turbine is directly connected to a centrifugal compressor to drive a vapor-cycle chiller system (Figure 5.8). The MT simply replaces the electric motor/compressor unit commonly used in chillers. Using a conventional refrigerant such as HFC134a, the rest of the chiller system (condenser, expansion valve/economizer, evaporator, etc.) remains the same. When packaged as a chiller, the two-shaft MT systems can be sized to deliver between 30 and 400 refrigeration ton (RT) of chilled water. Typical integrated part-load value (IPLV) coefficients of performances (COP) approach 2.0 (based on HHV) under ARI conditions. In the past decade, natural gas-fueled systems such as these have become less expensive to operate than electric motor-driven chillers, due in part to rising electricity costs and comparatively low gas prices in the summer.

The two-shaft design is also well suited for driving positive displacement screw compressors (Figure 5.9). Again substituting the power turbine for the electric motor, the system can be designed to work with many different types of fluids in refrigeration and gas boosting applications. The operating characteristics of the engine make it best suited for full-load, continuous-duty, industrial refrigeration which, depending on the cycle design, can be configured to provide cooling down to -100°F (-73°C).

FIGURE 5.8

Microturbine chiller application cycle diagram.

FIGURE 5.8

Microturbine chiller application cycle diagram.

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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