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Heat engine

A heat engine – also called steam generator – converts the fuel’s chemical energy into thermal energy and conveys it to the water, converting it into steam, which powers a turbine connected to an alternator. Finally, the steam is once more condensed into water that will be sent to the heat engine.

Steam turbine

It’s a device that extracts thermal energy from pressurized steam generated by the heat engine and converts it into rotary motion. This occurs in three phases, which match three steam pressure levels. The turbine is connected to the alternator’s axle, which thus rotates.

Alternator

The alternator converts the mechanic energy transmitted by the turbine into electricity, by means of the phenomenon known as electromagnetic induction.

Transformer

The power produced by the alternator is transmitted to the transformer which heightens its current, before injecting it into the electrical grid, in order to reduce losses.

Condenser

The condenser cools the steam that leaves the low pressure body of the turbine until it turns liquid again, so that is can be re-injected into the cycle and re-pumped into the heat engine.

Pump

The feeding pump is used to guarantee water supply to the heat engine, in order to substitute the water that is converted into steam and is conveyed to the turbine. The pump sucks in the water that comes from the condenser and sends it towards the heat engine.

Catalyzer

The denitrification catalyzer is used to abate nitrogen oxides. The fumes produced by combustion in the heat engine travel inside it, and are mixed with ammonia and oxygen so as to produce the reaction that converts nitrogen oxides into molecular nitrogen and water.

Dust collector

The electrostatic collector, placed between the catalyzer and the chimney, is a device that collects dust particles contained in fumes by means of electrostatic fields.

Hydroelectric


	Combined cycle

	Heat engine
	Turbine
	Alternator
	Transformer
	Pump
	Condenser
	Catalyzer
	Dust collector

In a combined cycle plant the thermal energy generated from combustion of a fuel mass (coal, oil, orimulsion or methane) is converted, through a thermal cycle, into mechanical energy, in turn converted into electricity, by means of an alternator. The fuel burnt inside the heat engine, produces thermal energy, which converts process-water into steam. The latter, which is exposed to a very high level of heat, reaches the blades of the turbinewhich convert the steam’s potential energy into mechanical energy. This energy is then conveyed to the alternator which converts it into medium voltage power. The voltage level is heightened by means of elevating transformers that connect the power station to the high voltage grid. The steam, after having conveyed its energy to the turbine, is released by the latter and collected inside the condenser inside which it is reconverted into water - by means of the cooling water coming from the outside – and then transmitted to the heat engine through the feeding pump so that the cycle starts again.

In a conventional combined cycle plant, only approximately 38% of the thermal energy that is released from combustion in the heat engine is converted into power. The remaining 62% is dissipated in the subsequent energy conversions (chemical to thermal, thermal to mechanical, as well as mechanical to electrical) and as residual heat from the chimney fumes and from the steam destined to condensation and recovered as hot water to be sent back to the heat engine for a new cycle. The electricity produced and grid-injected is conveyed, by means of specific electric lines, to transforming stations where other transformers make it available to meet the needs of different users.

Over 60% of the electricity produced worldwide comes from burning fossil fuels: coil, fuel-oil and gas. And this percentace is bound to increase, reaching 68% by 2010 according to estimates of the International Energy Agency (IEA). Even in Europe, where nuclear production is widely implemented, the share of conventional thermoelectric generation surpasses half the total. In Italy, in 1999 the thermoelectric component (209 TWh) represented almost 80% of the total gross production. Taking into account the facilities' capacity, still in 1999, in Italy, conventional thermal power plants had a total net power of 52,584 MW, representing 71% of the total, a percentage similar to the one recorded in the World.)