View source for Combined cycle gas plant

[[Category:Done 2020-02-29]]
[[File:Shazand_Combined-cycle_power_plant.JPG|300px|thumb|Figure 1. Combined cycle gas plant in Iran.<ref>Wikimedia Commons [Online], Available: http://upload.wikimedia.org/wikipedia/commons/f/fd/Shazand_Combined-cycle_power_plant.JPG</ref>]]

<onlyinclude>'''Combined cycle gas plants''' are a type of [[natural gas power plant]] used to [[generate electricity]],  consisting of a [[simple cycle gas plant]] in combination with a second [[external heat engine|steam engine]] that uses the [[Rankine cycle]].</onlyinclude> The hot [[exhaust gas]]es from the initial [[gas turbine]] are sent to the steam engine, and the [[heat]] from them is used to generate [[steam]]. This steam can then expand through another [[turbine]], generating even more [[electricity]] and increasing the plant's overall [[efficiency]]. The efficiency of these plants can be as great as 55%<ref name=ieso>IESO, ''Natural Gas - Simple/Combined Cycle Generation'' [Online], Available: http://www.powerauthority.on.ca/current-electricity-contracts/sc-cc</ref>, but the [[Dispatchable source of electricity#Dispatch times|dispatch times]] tend to be slower than simple cycle [[natural gas]] plants. The combined cycle typically has an increased cost. The EIA estimated that for a simple cycle plant the cost is about US$389/[[watt|kW]], whereas combined cycle plants are US$500 – 550/kW.<ref>Paul Breeze. (2005) ''Power Generation Technologies'' [Online Book], Available: https://books.google.co.uk/books?id=D9qSDgTbRZoC&pg=PA59&dq=%22Simple+cycle+combustion+turbine%22&hl=en&sa=X&ei=8A4sUYaND4vA9QSSqIDIDw#v=onepage&q=%22Simple%20cycle%20combustion%20turbine%22&f=false</ref>

==Operation==

The first part of the plant operates by use of a gas turbine and the details can be explored on its [[gas turbine|page here]]. Essentially, it works by compressing air, injecting [[fuel]] and [[Combustion|igniting the mixture]], which expands through the turbine causing it to spin. This turbine is connected to a [[generator]], which then causes electricity to flow. This process creates hot exhaust gases, which are typically dispelled in a simple cycle plant (releasing [[waste heat]]). 

The exhaust gases are made to flow towards the next unit, called the '''heat recovery steam generator''' (HRSG).<ref name=wart>Wartsila, ''Combined Cycle Plant for Power Generation: Introduction'' [Online], Available: http://www.wartsila.com/power-plants/learning-center/technical-comparisons/combined-cycle-plant-for-power-generation-introduction</ref> The HRSG is essentially a [[heat exchanger]], in which the [[heat]] from the hot gases is used to [[boiling point|boil]] pre-heat [[water]] into [[steam]]. The ''steam then expands through a turbine'', generating electricity. Once the steam has passed through, it [[condensation|condenses]] and is recycled through.

A short video from the Tennessee Valley Authority<ref>Taken from 'http://www.tva.gov/power/comb_cycle_video.htm', accessed June 12th, 2015. This video is used under creative commons license found here: https://en.wikipedia.org/wiki/File:Combined_cycle_animation.ogv (accessed June 12th, 2015 as well).</ref> visualizing the process can be seen below:

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==For Further Reading==
*[[Simple cycle gas plant]]
*[[Gas turbine]]
*[[Cogeneration]]
*[[Steam]]
*[[Heat exchanger]]
*Or explore a [[Special:Random|random page]]

==References==
{{reflist}}
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