254 Controls and Communications Dispatchability

The characteristics of Stirling generators allow them to be located inside homes, businesses, and similar environments where IC generators would be intolerable because of their high noise and maintenance levels. The most popular application of Stirling generators is in micro-cogeneration systems. In these systems, the generator is coupled to a household boiler (a water heater for hydronic space heating), so electricity and hot water are produced simultaneously from the same fuel. Stirling micro-cogeneration systems are gaining popularity in Northern Europe, where they are connected to the grid and use natural gas. The micro-cogeneration system is treated much like any other home heating system as far as the consumer is concerned. The systems can be configured to supply electricity only when heat is called for, or they can be programmed to dump unwanted heat when only electricity is needed.

Being connected to the grid is an excellent way to operate Stirling generators. The grid controls the generator frequency and voltage, so very little is needed for the connection other than the requisite safety equipment. Connecting a free-piston Stirling generator to the grid is a fairly simple operation and requires minimal hardware for the European grid. Utilities in the U.S. are only now becoming exposed to numerous consumer level, grid-coupled generators, and must evaluate implementing them with the U.S. grid.

Stirling generators also operate very well off-grid as battery chargers. The generator can run continuously, charging a battery bank, to handle peak loads that may be greater than the engine's capacity. Many photovoltaic (PV) systems are installed in this fashion but require a large number of batteries, since they can only provide charging power when the sun is shining. A Stirling generator can run day and night, thereby requiring a minimum amount of batteries. Since the generator doesn't need to be shut down, the required amount of batteries is far less than even gasoline and diesel generator systems need. When an engine is run off-grid, system electronics can automatically activate the generator when battery voltage drops below a preset threshold and shut it down again once the battery bank is fully charged. AC power can be easily obtained from a battery bank by using an inverter. Generators in this type of system can easily power off-grid homes, remote monitoring equipment, or communication relays.

Activation of Stirling generators can be handled in a variety of ways, depending on the application. Remote activation by a utility is certainly possible, but the relatively small capacity of the Stirling generator would be insignificant on a utility scale unless the installed capacity was very large.

When connected to the grid, it is far more practical to turn the generator on and off as needed or activate it as loads within the household reach prescribed levels. This way, power can be produced when it is most needed or most cost effective. Off-grid systems are best run continuously or shut down only when the battery bank is fully charged. This minimizes the size and cost of the battery bank and allows the system to more easily handle loads that exceed the engine capacity.

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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