Solar Power Technology

In a fossil-fueled power plant the chemical energy inherent in the fossil fuel is converted first to raise the enthalpy of the combustion gases; that enthalpy is transferred by convection and radiation to a working fluid (usually, water/steam); the enthalpy of the working fluid is converted to mechanical energy in a turbine; and finally the mechanical energy of the turbine shaft is converted to electrical energy in a generator.

The major components of a fossil fueled power plant are as follows:
• Fuel storage and preparation
• Burner
• Boiler
• Steam turbine
• Gas turbine
• Condenser
• Cooling tower
• Generator
• Emission control

Fuel Storage and Preparation
Coal is delivered to a power plant by rail or, in the case of coastal or riverine plants, by ship or barge. Usually, power plant operators like to have several weeks of coal supply on site, in case of delivery problems or coal mine strikes. Because a 1000-MW power plant, having a thermal efficiency of 35%, consumes on the order of 1E(4) metric tons of coal per day, the coal mounds near the plant may contain up to 3E(5) metric tons of coal. Some coal-fired power plants are situated right near coal mines (so-called mine-mouth plants). Even these plants store at least a month’s supply of coal
near the plant.

When coal arrives by rail, it is usually carried by a unit train, consisting of a hundred wagons filled with coal, at 100 tons per wagon. The wagons are emptied by a rotary dump, and the coal is carried by conveyors to a stockpile, or directly to the power plant.

Coal is delivered to a plant already sized to meet the feed size of the pulverizing mill, in the order of a few to ten centimeters per coal lump. In the United States and many other countries, coal is washed at the mine.Washing of coal removes much of the mineral content of the coal (including pyritic sulfur), thus reducing its ash and sulfur content and improving its heating value per unit mass. In preparation for washing, the coal is crushed at the mine mouth to less than
a centimeter per nut or slack.

Most modern steam power plants fire pulverized coal. The raw coal from the stockpile is delivered on a conveyor belt directly to a pulverizing mill. Such mills are either of the rotating ring, rotating hammer, or rotating ball type. The mill reduces the raw coal lumps to particles smaller than 1 millimeter. The pulverized coal is stored in large vertical silos from whence it is blown pneumatically into the burners at a rate demanded by the load of the plant.

In oil-fired power plants, oil is stored in large tanks (the “tank farm”), to which oil is delivered either by pipeline, by railroad tankers, or by tanker ship or barge if the plant is located near navigable waters. Power plants like to have at least a 30-day supply of oil in their tanks. For a 1000-MW plant with 35% efficiency, this can amount to over 1E(5) metric tons of oil. The oil is purchased from refineries in the form it is combusted in the burners, with specified sulfur, nitrogen, and ash
content as well as other properties, such as viscosity and vapor pressure.

In natural gas-fired power plants, gas is delivered to the power plant by pipeline at high pressure (compressed natural gas, CNG). Some gas-fired power plants use liquefied natural gas (LNG). Liquefied gas is transported in huge (up to 1.25E(5) m3) refrigerated tankers at −164 ◦C. The LNG is stored in refrigerated tanks until used.