Combined cycle gas turbine plants

Fig. B.5. Effect of carbon dioxide lax on electricity price for a combined cycle gas turbine plant.

In open cycle, the diesel has the higher efficiency, making it more attractive for light fuel oils. However, in combined cycle, the gas turbine often has the highest overall efficiency, but there is the penalty associated with the additional cost for boiler and turbine. Nevertheless, unless the prime fuel is of low cost, the use of combined-cycle gas turbine plant will prove to be the more economic. 

In the 1980s, fundamental changes took place in the state-owned sector with the so-called privatization of the industry. First in Chile, then in the UK, the assets of the publicly-owned electricity authorities were vested in companies which issued equity shares to the general public. This change in ownership was coupled with a fundamental shift in the way electricity was produced and sold. New, cheaper, technologies such as gas-fired, combined cycle, gas turbine plant, which could be built more quickly than the traditional coal-fired steam turbine plant, and which is less labour intensive in its operation, was introduced extensively in the UK. The separate producers of electricity competed with each other on price (per kWh) to win market share. It is alleged, with some justification in the UK, that such competition has reduced the price to the end-user. 

The latest available statistics on electricity supply relate to 1995. The general trend of recent years continues, ie. increases in generation from combined cycle gas turbine plant and from renewable energy sources whilst the coal and oil contribution is reduced. Nuclear electricity remains an important contributor in Britain, but it is not expected to grow in the near future. Electricity supplied in 1995 comprised ... 

An important field of study for power plants is that of the combinedplant [ 1 ]. A broad definition of the combined power plant (Fig. 1.5) is one in which a higher (upper or topping) thermodynamic cycle produces power, but part or all of its heat rejection is used in supplying heat to a lower or bottoming cycle. The upper plant is frequently an open circuit gas turbine while the lower plant is a closed circuit steam turbine together they form a combined cycle gas turbine (CCGT) plant. 

In recent years there has been a rapid growth in the number of combined heat and power (CHP) and combined cycle gas turbine (CCGT) plants, driven mainly by gas turbines using natural gas, sometimes with liquid fuel available as stand-by. Governments have encouraged the construction of these plants, as their efficiency is high and they produce less carbon dioxide than conventional coal and oil-burning power stations. However, they present some hazards, as gas turbines are noisy and are therefore usually enclosed. 

Restructuring will promote the introduction of other advanced technologies and practices as well. For example, the use of combined-cycle, gas turbine power plants are expected to proliferate under restructuring. These plants are generally more efficient and more environmentally benign than many fossil fuel plants currently in use. 

The required oxygen is produced in an air-separation plant. The electricity for the air-separation plant is provided by a natural-gas fuelled combined-cycle gas turbine (CCGT) power plant. 

In contrast, the yield of electricity from photovoltaics (PV) is about 337 500 kWh per ha and year, even if it is assumed that the area of the PV panels cover about one-third of the total plant area. If PV electricity were converted to liquid hydrogen (LH2), stored and then converted back to electricity by a combined cycle gas turbine (CCGT, efficiency 57.5%) about 104000 kWh electricity could be generated per ha and year. This yield is still more than three times the yield of the best biomass pathway (upper end of bandwidth electricity from biogas via large gas engine). 

Different generation technologies produce different levels of C02 emissions, and therefore the opportunity costs of C02 emissions per unit of power produced differ as well. For example, a combined-cycle gas turbine produces about 0.48 t of C02 per MWh of electricity, while a typical coal power station emits about 0.85 tC02/MWh. A C02 price of 20/tCO2, therefore, increases the generation costs for the gas plant by 9.6/MWh and for the coal plant by l7/MWh. 

Recent very successful demonstrations of the high efficiencies that can be achieved with combined cycle gas turbine-steam turbine power plants using pressurized, fluidized... 

The present treatment of the conventional process will be based on the process diagram presented in Figure 1, which represents a steam reformer coupled with an ammonia synthesis plant [6], This is one of the two cases, which were considered in the project. The other was the use of the produced hydrogen as fuel in combined cycle gas turbines. In this chapter, the steam reforming part will be treated only, but some comments on the ammonia plant will be made, in view of the composition of the product stream leaving the steam reformer. 

A transfer provision was initially drafted for new plants which had been built to replace old plants. If the operators complied with the requirement of the three-month (without any further examination) to the two-year period (if the respective verifications could be provided) from the closure of the old plant and the opening of the new plant, the allocation to the old plants would be transferred to the new plants without restrictions, provided that the new plants produced comparable products. In addition to the transfer rule - which was considered as a standard - there should be a rule that provides additional new plants (as well as plant expansions) a free allocation on the basis of the planned capacity use and an emission benchmark. The emission benchmark should be orientated towards BAT procedure. Above all, it should not be differentiated by fuel or technologies. As far as electricity production is concerned, a benchmark orientated towards a modern natural gas-fired combined cycle gas turbine (CCGT) power plant (365 g CCh/kWh) was scheduled. The allocation calculated in this way should be subject to an ex-post adjustment in the course of the following years. Thus, a special procedure was scheduled for CHP plants. The allocation should be determined with the help of the benchmark for electricity generation as well as the benchmark for heat generation. 

In a combined cycle power plant (CCPP), or combined cycle gas turbine (CCGT) plant, a gas turbine generator produces electricity and the waste heat is used to make steam for generating additional electricity via a steam turbine this last step enhances the efficiency for electricity generation to about 60%, because the temperature difference between the input and output heat levels is higher leading to an increase in the Carnot efficiency. Most modem power plants in Europe and in North America are of this type. 

Lobachyov K, Richter HJ (1996) Combined cycle gas turbine power plant with coal gasification and solid oxide fuel cell. J Energy Resour Technol 118 285-292... 

Coal gasification may likely find future application in methanol production for utilization in combined cycle power generation facilities. In this case, the methanol (stored on-site as a liquid) will be utilized as a peak shaving fuel and will be produced from excess ifier capacity as power demand is reduced. Several different schemes have been proposed for combining methanol production with coal ification in a power plant scenario. This particular arrangement may be most favorable for a liquid-phase process (see reference to the Air Product process in Sec. 3.2.7) that can utilize a substoichiometric feed with a reasonable once-throu conversion while passing on unconverted gas to the combined cycle gas turbine as a fuel... 

Jet engines entered use in central power plants as natiual gas combined cycle gas turbine power plants from the 1980s. 

The potential for an explosion inside a gas turbine combined heat and power (CHP) plant or a combined cycle gas turbine (CCGT) plant enclosure from a fuel leak has been widely addressed in the industry and reviewed at a number of seminars. Enron, the Teesside Power Station operators, contracted a study into the explosion potential inside the gas turbine (GT) enclostu-e and to recommend solutions to achieve an acceptable level of risk. 

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