Which of the following most accurately describes a "power boiler"?

A power boiler is specifically defined as a boiler that generates energy through combustion processes, typically used to produce steam or heat water. This steam or heated water is often utilized for power generation or other industrial processes. Power boilers operate at high pressures and temperatures, allowing them to effectively convert the energy from fuel into usable forms.

In contrast, options describing a boiler used solely for heating water or restricted to residential use do not encompass the full capabilities of a power boiler, which is designed not just for heating, but for significant energy generation. A power boiler also possesses a pressure vessel, making the option that states it has no pressure vessel inaccurate. Therefore, the description of generating energy through combustion clearly aligns with the primary function and operational characteristics of a power boiler.