Gas power station

A gas power plant is a power plant which uses as a primary energy source, the chemical energy from the combustion of a fuel gas. The fuel gas is by far the most commonly used is natural gas; but also other gases such as biogas, byproduct gases, firedamp come into question.

The power generation of the fuel gas can be done with different types of thermal power stations: In addition to classic steam power stations or heat engines (gas turbines or gas engines ) with natural gas firing are now mainly gas - and -steam combined cycle power plants in use.

Nomenclature

If the designation gas power plant used without further indication of the type of gas, then it is usually to natural gas. For other fuel gases (see below ) the species is usually in the name listed (biogas power plant, blast furnace gas power plant, etc.).

Power plants, which are not usually referred to as gas -fired plant, the chemical, but the kinetic or thermal energy of a gas use ( such as wind power plants, compressed air storage power plants, etc.).

Also for fuel cell power plants, the use of the name is uncommon, despite the fact that the converted in the cell fuel is often a common fuel gas (mostly hydrogen) is.

Fuel gases

In general, unless otherwise specified, is the burned gas to natural gas. Rare are other fuel gases are used:

• Byproduct gases from industrial processes ( blast furnace gas, blast furnace gas, refinery gas, etc. )
• Biogas, Kompogas from the fermentation of biomass (see biogas plant )
• Gas from biomass gasification, especially wood gas ( see, eg, Biomass Integrated Gasification Combined Cycle)
• Landfill gas from landfills
• Mine gas from ( disused ) coal mines
• Hydrogen, EE - gas, ...
• Liquefied
• Coal from a coal gasification gas ( see, for example IGCC)

Compared to solid fuels ( liquid fuels and also limited ), most fuel gases for use in power plants significant technical advantages: The fuel supply systems (interim storage, preparation, promotion, etc. ) are much simpler in design. Since most gases very " clean" ( low emissions ) burn because of their ingredients, the emission is greatly simplified. Also covered in burning no ash. All to ensure that combustion gases are - unlike solid fuels - also suitable as a fuel for internal combustion engines. In connection with the greenhouse effect is also advantageous that many fuel gases have a high H / C ratio ( ratio of hydrogen to carbon) and therefore less climate -damaging carbon dioxide produced by the combustion.

The section below types of gas-fired plants mentioned technologies for fuel gases are very similar to those for liquid fuels. In particular, older gas power plants are therefore often carried out "dual " so that, as required both gas and liquid Brenn-/Kraftstoffe (diesel, heating oil, etc. ) can be used, that is, the power plant will be entirely or partially as oil-fired power plant operated.

Types of gas-fired power plants

As the technology for converting the stored chemical energy in the fuel gas in thermal, mechanical and electrical energy ultimately different types of thermal power plants are:

Gas turbine and engine power stations

In gas power plants of this type, the energy of the fuel gas is converted directly to an internal combustion engine into mechanical energy and drive further means of a hitched generator into electrical energy ( " current").

The machines used are mostly of gas turbines; alternatively suit the task and also size gas engines (internal combustion ) or Stirling engine ( external combustion ) in question. While engines are particularly common than smaller (emergency) power generators or as compact cogeneration plants for the decentralized power and heat supply, find larger gas turbine power plants and industrial power plants and in the public power supply use (the latter due to the below mentioned disadvantages today only as peak load power plant).

Gas power plants of this type are characterized by their simple structure, high power density, high flexibility with short start times (about 15 minutes to full load ) and high load gradients and low specific investment costs (cost per kilowatt ). By dispensing with the steam process eliminates a lot of systems and system components; the system consists essentially only of the machine with its combustion air and exhaust system and the fuel supply and the electric grid connection ( see scheme). It is often omitted in such facilities on an engine house, the machine receives only a simple weather protection cover, which also acts as soundproofing. Thanks to the high availability and automation of such machines no permanent operating and maintenance personnel is required on site. Operation is largely fully automatically, the system can be operated by remote control, a control room on the ground is not normally present.

The main disadvantage of internal combustion engines is their low efficiency in the simple process ( "Simple Cycle", that is, only Open Cycle without downstream steam process ) usually only at a maximum of 30%. Because of the high quality and expensive fuel is only poorly exploited, larger gas turbine and engine power stations in most countries are now used almost exclusively as " peakers " (peak load power plant). Because of the increasingly disadvantages sat down in the 1990s, combined cycle power plants ( see below). Older power plants from before were converted predominantly either to combined cycle power plants or held ready for use only as fast bootable reserve. Only in countries that have large domestic gas resources and in which gas prices are correspondingly low, gas turbine and engine power plants are today central and sometimes still used in the base load. Special cases are power plants, like the specialty gases such as biogas, mine gas, landfill gas burn (see below section Brengase ).

Gas -fired steam power plants

In gas power plants of this type are conventional steam power plants whose steam generator (boiler ) is fired by gas burner with a fuel gas.

In their design and operation such gas power plants resemble other fired steam power plants: The steam generated in the boiler is used through a steam turbine to generate electricity. A cooling system ( cooling tower, etc. ), the inevitable waste heat into the environment. Compared to steam power plants that are fueled with solid fuels, many systems, however, are much easier, starting with fuel supply. Also falls at a gas power plant at no ash or slag from combustion. The emissions control system is greatly simplified with fuel gases: A dusting of soot or fly ash is not required for clean combustion. In low-sulfur fuel gases can also be dispensed with a flue gas desulphurisation. A denitrification (catalytic or non- catalytic) may be integrated into the combustion, and the steam generator. Often, therefore, fireplace - are placed directly on top of the tower boiler - without intermediate emission control.

The disadvantage of this design is similar to the above in the internal combustion engines, in particular the relatively poor efficiency. Compared to internal combustion engines is aggravated that a gas-fired steam power plant is much more expensive in construction and in terms of starting times ( approximately 1 hour to full load ) is not quite as flexible and load gradient. That still up in the 1980s, such gas-fired power plants were built in large numbers, mainly because that in this time, the gas was still relatively inexpensive and that the available on the market gas turbines and engines were still relatively small. With the development of more efficient gas turbines, gas-fired steam power plants were increasingly from the 1990s through GT and combined cycle power plants (see below) displaced. Older gas-fired steam power plants, which are still in operation today, are almost only used as peak load power plant or heating plant in combined heat and power generation.

Combined cycle power plants

In a combined cycle power plant an internal combustion engine (gas turbine or gas engine less frequently ) is combined with a steam power plant (consisting of a steam boiler and a steam turbine with cooling system ); Thus, the advantages of the above two types are combined and partially mitigate the disadvantages. The machine makes the power plant flexible and quick to use manner, and by the combination of gas and steam combined cycle power plants process achieve the highest efficiency of all thermal power plants (up to about 60%). Disadvantages are mainly the high fuel and thus operating costs, which mean that even combined cycle power plants are used only in exceptional cases in the base load even with this type.

In the combined cycle power plants, two subspecies are distinguished by the power fraction of gas and steam process:

Use way

Plants that burn gas, are compared to solid fuel comparatively simple in construction and have a high power density, resulting in relatively low construction costs result. However, since the combustion gases are very high quality and expensive fuels in general, gas-fired power plants have high operating costs. From the ratio of construction and operating costs shows that gas-fired plants are mostly used for load regulation in the medium and peak load range. In base load gas-fired plants are usually economically most as cogeneration in combined heat and power generation.

Through the development of more efficient gas turbines, reduced costs and improved efficiencies it came from the 1990s to a " boom" of combined cycle power plants in many industrialized nations. As a result, for example, doubled the use of gas for electricity generation in Germany between 1990 and 2012 ( see picture).

Because of the short startup time and quickly regulate gas-fired power plants are considered to be indispensable for compensation of fluctuations, such as increasingly occur due to the growing supply of volatile electricity from wind and solar energy. On the part of politicians and associations is therefore requested and predicted a further expansion of gas-fired power plant capacity as a reserve to secure the energy turnaround. On the part of the operator but laments that in particular the elimination of Mittagsspitze by the rising supply from photovoltaic systems the efficiency of gas power stations reduces greatly, so that at present there is no incentive to build new gas-fired plants. In addition, gas-fired plants are affected by their relatively high operating costs and the resultant position in the merit order disproportionately from the currently prevailing overcapacity in the electricity market and the resulting low market power prices. Therefore, some operators have announced the closure of uneconomic become gas power plants. To counter this, the Energy Act was revised to the effect that gas power plants, which are classified by the Federal Network Agency as " systemically important " must be kept ready for use against payment of compensation by the operator.