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The Stirling Engine was invented and developed by Reverend Dr Robert Stirling and his brother James, an engineer, over several years starting in 1816. The inventors sought to create a safer alternative to the steam engines of the time, whose boilers often exploded due to the high pressure of the steam and the inadequate materials. The original patent by Rev. Stirling was called the “economizer”, for its enhancement of fuel-economy. The patent also mentioned the possibility of using the device in an engine. Several patents were later awarded to the two brothers for different configurations including pressurized versions of the engine. This component is now commonly known as the “regenerator”, and is essential in all high-power Stirling devices.
In the conversion of heat into mechanical work, Stirling engines can achieve the highest efficiency of any real heat engine, up to 80% of the Carnot efficiency, limited only by non-ideal properties of the working gas and engine materials, such as friction, thermal conductivity, tensile strength, creep, melting point, etc. The engines can theoretically run on any heat source of sufficient quality, including solar, chemical and nuclear.
In contrast to internal combustion engines, Stirling engines are usually more energy efficient, quieter, and more reliable with lower-maintenance requirements. They are preferred for certain niche applications that value these unique advantages, particularly in cases where the primary objective is not to minimize the capital cost per unit power ($/kW), but rather to minimize the cost per unit energy generated by the engine ($/kWh). Compared to an internal combustion engine of a given power rating, Stirling engines currently have a higher capital cost and are usually larger and heavier, thus the engine technology is rarely competitive on this basis alone. For some applications however, a proper Cost-benefit analysis can favor a Stirling engine over an internal combustion engine.
In recent years, the advantages of Stirling engines have become increasingly significant, given the general rise in energy costs, energy shortages and environmental concerns such as climate change. These growing interests in Stirling technology have fostered the ongoing research and development of Stirling devices. The applications include water pumping, space-based astronautics, and electrical generation from plentiful energy sources that are incompatible with the internal combustion engine, such as solar energy, agricultural waste and domestic refuse.
Another potentially useful characteristic of the Sterling engine is that if supplied with mechanical power, it can function as a heat pump. Experiments have been performed using wind power driving a Sterling cycle heat pump for domestic heating and air conditioning.
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