On the Grid Soung Sik-Kim Chapter 29

Summary A chemical engineer Soung- Sik-Kim Describes optimizing the efficiency of coal-fired power plants Discusses the benefits as an energy source: plentiful, easy to store and transport, and many power plants are already designed to burn it. Discusses downsides: air pollution and acid rain Describes how a power plant generates electricity and distributed through the grid. Describes the grid as a large interconnected set of circuits, and explains some of the basics

Electricity and Electronics Electricity is charge flowing in wires. Energy is required to make charge move. A power plant is designed to use the chemical energy in fossil fuels to move charges through wires.

Circuit A circuit is a closed continuous conducting path along which charge can flow. A circuit has an energy source (a battery or a power plant), a conductor (often a wire), and a load (an electrical device that uses the energy carried buy the charge to do work.

Grid The electrical distribution grid is a vast system connecting millions of end users to electric power. Power plants are connected to the grid and supply the voltage difference to move charge through the grid. When more loads are connected to the grid, electrical generation at power plants increases. Energy is not stored anywhere in the grid.

Power Is a rate at which energy is produced or consumed. The unit for power is the watt (W). One watt equals one joule/ second. Engineers often describe power in terms of kilowatts (1000x( or magawatts (1 million x).

Question 1 Question What is Soung referring to when she talks about “the grid,” and how does “the grid” supply our electrical power? Answer “The grid” is a massive system of interconnecting circuits that provides electric power to end-users. There are ten grids in North America. The electricity that power plants generate enters the grid directly. Power companies provide grid access to end-users and charge for energy consumed. Power companies also make sure that power plants provide enough electrical power to the grid to meet their end-users’ needs

Question 2 Question What caused the U.S. government to start funding clean coal research like the kind that Soung does? Answer In the 80’s, there was public outrage over acid rain, which was created when sulfur dioxide and nitrogen oxide in the air combined with rainwater, making the rainwater acidic. The acid rain hurt plants and animals in entire ecosystems and damaged buildings and statues made of marble and limestone. In response to public concern, the US Environmental Protection Agency (EPA) placed limits on the amount of toxic gasses power plants may release. The government started funding clean coal research in an effort to help power plants meet those limits.

Question 3 Question Describe two ways that Soung is making coal-fired power plants more efficient and cleaner for the environment. Answer Installing sensors to monitor the temperature of gasses in the combustion chamber makes it possible to adjust the flame size or oxygen level so that as much energy as possible transferred to the water in the boiler. Removing soot from the boiler tubes so as to remove unwanted insulation in order to transfer as much heat as possible to the water in the boiler. Reducing waste by using fly ash from coal burning as an ingredient in concrete, and using molten ash, called slag, in roof shingles. Reducing atmospheric pollution by using a “scrubber” to remove sulfur from the exhaust and combining it with limestone to make Gypsum, which is used as a building material.

Question 4 and 5 Question 4 What is necessary for charge to flow through a circuit? Answer 4 The circuit must be a continuous, closed conducting path. Also, energy is required to make charge move, so there must be a power source. Question 5 What is the relationship between energy and power? What are the units for each? Answer 5 Power is the rate at which energy is consumed or produced. The units used most frequently for energy are the joule, the BTU, and the kilowatt-hour. The units used most often for power are the watt (j/s), the kilowatt, and the megawatt.