The choice of liquid used for turning turbines in power plants depends on several factors, including its boiling point, availability, cost, safety, environmental impact, and efficiency in converting heat energy into mechanical energy.
While there are liquids with lower boiling points than water, such as ammonia and organic compounds, they have their own drawbacks and limitations. Here are some reasons why these alternative liquids are not commonly used:
Boiling Point: Liquids with lower boiling points require lower temperatures to vaporize, which can limit their suitability for power generation. Water has a high boiling point (100 degrees Celsius or 212 degrees Fahrenheit), allowing it to absorb more heat and transfer it to the turbine efficiently. Liquids with lower boiling points may not be able to operate within the desired temperature range to generate sufficient steam.
Efficiency: The efficiency of a power plant depends on the temperature difference between the heat source (e.g., burning fuel) and the cooling medium (e.g., water or air). Higher temperatures generally result in greater efficiency. Water has excellent heat transfer properties and can handle high temperatures, making it well-suited for efficient energy conversion. Alternative liquids may have lower thermal conductivity or heat capacity, leading to reduced efficiency.
Safety and Environmental Impact: Power plants require liquids that are safe to handle, non-toxic, non-flammable, and have low environmental impact. While some alternative liquids may have lower boiling points, they may also be hazardous, corrosive, or pose environmental risks. Water, on the other hand, is widely available, non-toxic, and relatively safe to use.
Infrastructure and Compatibility: Power plants are designed and built based on the properties and characteristics of water as the working fluid. Switching to alternative liquids would require significant modifications to existing infrastructure, including the turbines, condensers, and other systems. The compatibility of materials with the working fluid is also crucial, as certain liquids may corrode or degrade equipment over time.
Despite the limitations of water, it remains the most commonly used working fluid in power plants due to its favorable properties and extensive infrastructure. However, research and development efforts continue to explore alternative working fluids and technologies that can improve the efficiency and environmental sustainability of power generation.