A natural gas power plant burns natural gas to produce electricity. In one second it produces 500 MJ of electrical potential energy. The power plant consumes chemical energy in order to produce electrical potential
energy.
--In one second does it consume 500 MJ of chemical energy, less than 500 MJ or more than 500 MJ? Explain.
My solution,
E chem = Ep + E thermal
So it consumes more than 500 MJ, because what is consumed is transferred to mostly Ep and smaller portion to E thermal.
--The power plant has large cooling towers full of water. Why are these necessary?
My solution,
It is necessary because the chemical energy consumed creates E thermal (heat) so it needs to cool down.
Am I right or wrong?
For the first question, your solution is correct. The power plant consumes chemical energy to produce both electrical potential energy (Ep) and thermal energy (E thermal). Since the electrical potential energy produced in one second is 500 MJ, and there is also thermal energy being generated, it means that the total chemical energy consumed by the power plant in one second is more than 500 MJ.
For the second question, your explanation is partially correct. The cooling towers in a power plant are indeed necessary to cool down the thermal energy produced during the conversion of chemical energy to electrical potential energy. However, it is not just the chemical energy consumed that creates the thermal energy but also the inefficiencies of the power plant itself. The conversion process is not 100% efficient, and some energy is lost as heat. The cooling towers help dissipate this excess heat by transferring it to the surrounding environment, usually through the evaporation of water. So while cooling towers help in cooling down the power plant, they are not solely related to the chemical energy consumption.
You are partially correct in both answers.
For the first question, it is indeed true that the power plant consumes more than 500 MJ of chemical energy. This is because not all the chemical energy is converted into electrical potential energy (Ep). Some of the energy is lost as thermal energy (Ethermal) due to the inefficiencies in the conversion process.
However, for the second question, the purpose of cooling towers in a natural gas power plant is not solely to cool down the system due to the generation of thermal energy. The primary function of cooling towers is to remove excess heat from the power plant's steam cycle. When the hot steam passes through the turbines, it condenses back to water. The cooling towers facilitate this condensation process by removing heat from the water, allowing it to be reused in the system. This helps improve the overall efficiency of the power plant as it reduces the amount of water that needs to be continuously supplied from external sources.
So, while your answer touches on the idea of removing heat, it is important to emphasize that the cooling towers are specifically utilized for removing excess heat from the power plant's steam cycle, rather than solely cooling down the system due to the generation of thermal energy.