Define "thermal efficiency" in relation to boilers.

Thermal efficiency is defined as the ratio of energy output in the form of heat to the energy input from the fuel in a boiler system. This measurement is crucial because it indicates how effectively the boiler converts the energy stored in the fuel into usable heat. A higher thermal efficiency means that more of the fuel's energy is being converted into heat, thus reducing waste and improving the overall performance of the boiler. Understanding thermal efficiency allows operators to evaluate and optimize boiler operation, ensuring that energy resources are used effectively.

The other definitions, while related to boiler operation, do not capture the specific concept of thermal efficiency. Total energy usage refers to the overall energy consumption of the boiler without detailing how much of that energy is effectively converted to heat. The rate of steam production deals with the performance output of the boiler but does not reflect the efficiency of energy conversion. Lastly, the amount of fuel consumed over time relates to fuel usage metric rather than the efficiency of transforming that fuel's energy into heat.