![]() These combined cycle plants are incredible versatile. The thermal section of the plant will provide baseload power, and the gas turbine part will spin up to provide peak power. These combined cycle plants require the thermal section to almost always be on. If you recall from our previous article, thermal plants take a long time to ramp up power production. ![]() Combining these processes together can result in a 60% thermally efficient plant. ![]() ![]() This waste heat can then be shunted to boil water in a more traditional thermal plant. Our gas turbines discussed above produce temperatures in excess of 900 C. When peak electricity production is needed, the gas can go into the gas turbine instead of the thermal section. This combined cycle power plant has two sections: the thermal section and the gas turbine section. This series of turbines extracts much more heat, and thus much more efficiency, than a single-cycle turbine. It is then more or less directed to a subsequent turbines that are designed to be efficient at lower temperatures, and even with wet steam. In a normal thermal power plant, the steam coming out of the first turbine has lost some heat and pressure. Before getting into that, let’s briefly revisit how a normal thermal plant has higher efficiencies. Gas turbines can be combined with standard thermal plants often use what is called a combined cycle format. This has caused the US to decrease its annual CO2 emissions by nearly 10%. With hydrofracking causing a glut in natural gas in the US, producing power via gas is cost-competitive with coal in the US, and recently has been replacing coal to produce electricity. Natural gas plants contribute to GHG emissions and PM2.5 (PM 2.5 can form from emissions of NOx, which occurs from any combustion). Both produce less pollution than coal, simply because natural gas is cleaner than coal and produces more energy per unit CO2 emitted. The former has the same internals as a coal power plant and can provide baseload power, the latter is for peak power. Natural gas fired power plants come in two primary flavors: standard thermal plants, and fancy jet turbines. There are a few places where I use gas turbine and turbine in the same sentence. There is a special type of turbine called a gas turbine that directly burns natural gas inside of it to produce power. Every thermal power plant drives a turbine to produce power. Bad news! There are some confusing terms here. ![]()
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