144 Fuel Cells

A fuel cell (FC) is a device in which hydrogen and oxygen combine without combustion to produce electricity in the presence of a catalyst. One design is shown in Figure 1.11. Several competing technologies have been demonstrated and are listed below with their nominal operating temperatures.

As indicated in Table 1.2, fuel cells cost too much to be immediately competitive against grid-supplied electricity, but industry experts have indicated that with mass production prices should fall. Installed cost will not always be the deciding factor in choosing a given technology. Where environmental

FIGURE 1.11

PEM fuel cell schematic.

regulations are strict, fuel cells offer the only truly clean solution to electricity production outside of the renewables sector. The key barriers to fuel cell usage include cost (predicted cost reductions have not materialized; in fact, one large firm recently announced a 60% price increase), hydrogen fuel (widespread adoption will require a new fuel distribution infrastructure in the U.S. or on-site reforming of natural gas, i.e., methane), maintenance costs are uncertain, and transient response to building load variations is unacceptable for load following for some technologies.

In contrast to these barriers are some very attractive FC features, such as the only byproduct is water — NOx emissions are very low (< 1PPM), efficiency is good (50-60%, LHV basis), thermal or electrical cogeneration is possible in processes and in buildings, and modularity is excellent — nearly any building related load can be matched well (kW to MW range).

1.5 Matching the Load: Buildings and Industrial Processes

To set the context for distributed electrical generation and cogeneration, the important features of building load profiles in North America are summarized here. Buildings are expected to be one of the key early adoption sectors for distributed generation.

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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