Thermal Power Plant

A thermal power plant is a facility used to generate electrical energy from thermal energy, such as that released by fossil fuels, uranium, a conventional thermodynamic cycle to move an alternator and produce electrical energy, in the case of using fossil fuels, releasing carbon dioxide into the atmosphere. This is a gas that contributes to the greenhouse effect.

When heat is obtained through the controlled fission of uranium nuclei, the thermoelectric power plant is known as a nuclear power plant. This type of plant does not contribute to the greenhouse effect, but it does have the problem of radioactive waste that has to be stored for thousands of years and the possibility of serious accidents.

Introduction

Virtually all thermoelectric plants are coal, nuclear, geothermal, solar thermal energy, biomass combustion as well as there are some natural gas plants. The waste heat from a gas turbine can be used to produce mechanical work which generates steam as in engineer James Watt's steam engine and in turn produce electricity, in what is known as a combined cycle, which improves the efficiency. The steam introduced into the plunger makes it possible to drive, thanks to the piston, a rotor that generates electricity. Although it is efficient, it moved thanks to the invention of the turbomachine. Non-nuclear power plants, particularly fossil fuel power plants, are also known as thermal power plants or conventional power plants.

Conventional thermal power plants can use non-renewable energy sources, such as coal, oil and gas, or renewable energy sources, such as biomass.

Power plants that use fossil fuels generate a lot of energy in a large space and emit highly polluting gases. As for those that use biomass, if their consumption exceeds the regeneration capacity of the vegetation from which they are nourished, they can cause deforestation.

History

The first thermoelectric power station was built in the town of Ettal in Bavaria and came into operation in 1879. The first commercial power plants were the Pearl Street Power Plant in New York and the Edison Electric Light Station, in London, which came into operation in 1882.

These early power plants used piston steam engines. The development of the steam turbine allowed the construction of larger and more efficient plants, so that by 1905 the steam turbine had completely replaced piston steam engines in large power plants.

Conventional cycle thermoelectric plants

Classic or conventional cycle power plants are those thermal power plants that use the combustion of coal, oil (oil) or natural gas to generate electricity.

They are considered the most economical plants, so their use is widespread in the economically advanced world and in the developing world, despite being criticized due to their high environmental impact.

The following shows the operating diagram of a conventional cycle coal-fired power plant:

Basically, the operation of these types of plants is the same regardless of the fuel consumed. Thus, it burns in the boiler, releasing heat that is used to heat water.

The heated water will be transformed into steam with a very high pressure, which is what turns a steam turbine, which will transform the internal energy of the steam into mechanical energy (rotation of a shaft).

Electricity production is generated in the alternator, by the rotation of the rotor (which shares the same axis as the steam turbine) and by electromagnetic induction.

The generated electricity passes through a transformer, which will increase its voltage for transport.

The steam that comes out of the steam turbine is sent to a condenser (thermodynamics) to transform it into a liquid and return it to the boiler to start a new cycle of steam production.

Combined cycle power plants

Currently, numerous thermoelectric plants of the so-called combined cycle are being built, which are a type of plant that uses natural gas, diesel or even prepared coal as fuel to power a gas turbine. Then the exhaust gases from the gas turbine still have a high temperature, they are used to produce steam that drives a second turbine, this time steam. Each of these turbines is coupled to its corresponding alternator to generate electricity.

Normally during the starting process of these power plants only the gas turbine works; this mode of operation is called open cycle. Although most plants of this type can interchange fuel (between gas and diesel) even in operation.

As the temperature difference produced between the combustion and the exhaust gases is higher than in the case of a gas or steam turbine, much higher efficiency is achieved, of the order of 55%.

This type of power plant generated 32% of Spain's electricity needs in 2008.

GICC

In recent times, a new technology has been developed, Integrated Gasification in the Combined Cycle (IGCC), which, through a coal gasification system, significantly reduces polluting emissions into the atmosphere, by being able to apply the combined cycle to coal.

Environmental impact

The emission of waste into the atmosphere and the combustion processes that occur in thermal power plants have a significant impact on the environment. To try to alleviate, as far as possible, the damage that these plants cause in the natural environment, various elements and systems are incorporated into the facilities.

Some types of power plants contribute to the greenhouse effect by emitting carbon dioxide. This is not the case of solar thermal power plants that, by not burning any fuel, do not. It must also be considered that the mass of this gas emitted per unit of energy produced is not the same in all cases: coal is made up of carbon and impurities. Almost all of the carbon that is burned turns into carbon dioxide; it can also turn into carbon monoxide if the combustion is poor in oxygen. In the case of natural gas, for every carbon atom there are four hydrogen atom that also produce energy when combined with oxygen to become water, therefore they pollute less for each unit of energy they produce and the emission of harmful gases from the combustion of impurities —such as sulfur oxides— is much less.

Negative impacts can occur during construction as well as during operation of thermoelectric plants. Thermoelectric plants are considered important sources of atmospheric emissions and can affect air quality in the local or regional area. The combustion that occurs in thermoelectric projects emits sulfur dioxide (SO₂), nitrogen oxides (NO_x), carbon monoxide (CO), carbon dioxide (CO₂) and particulates (which may contain minor metals). The amounts of each will depend on the type and size of the facility, the type and quality of the fuel, and the manner in which it is burned. The dispersion and concentrations of these emissions, at the ground level, are the result of a complex interaction of the physical characteristics of the plant stack, the physical and chemical qualities of the emissions, the meteorological conditions at the site, or near the facility during the time required for emissions to travel from the stack to the ground-level receptor, the topographic conditions of the plant site and surrounding areas, and the nature of the receptors.

Clean cooling water is the most important effluent from thermoelectric plants. It can be recycled or discharged into surface water, without causing major effects in terms of its chemical quality. However, the effect of waste heat on ambient water temperature must be considered.

The pollution problem is greatest in the case of conventional thermoelectric plants that use coal as fuel. In addition, the combustion of coal results in the emission of particles and sulfur oxides that greatly pollute the atmosphere. In fuel oil the emission levels of these pollutants are lower, although the emission of oxides must be taken into account. of sulfur and acid soot, practically zero in gas plants.

In any case, to a greater or lesser extent, all of them emit carbon dioxide, CO₂, into the atmosphere. Depending on the fuel, and assuming a yield of 40% on the primary energy consumed, a thermal power plant emits approximately:

Fuel		CO emissions2 (kg/kWh)
Natural gas		0.68
Natural gas (combined cycle)		0.54
Fueloleo		0.70
Biomass (wood, wood)		0.82
Coal		1,00

Natural gas plants can work with the so-called combined cycle, which allows higher yields (up to a little more than 50%), which would still make plants that work with this fuel less polluting.

Advantages and disadvantages

Advantages

• They are the cheapest plants to build (taking into account the price per negative installed), especially coal, due to the simplicity (comparably speaking) of construction and the energy generated massively.
• The combined cycle power plants of natural gas are much more efficient (about 50%) than a conventional thermoelectric, increasing the electricity generated (and therefore profits) with the same amount of fuel, and reducing the emissions quoted above by 20%, thus remaining at 0.54 kg CO₂, for kWh produced.
• The large amount of thermal energy generated (in the most efficient, at least 50% of the total energy consumed) could be used as waste energy for heating (or even refrigerating) buildings through a distribution network.

Disadvantages

• The use of fuels generates greenhouse gas emissions and, in some cases, of acid rain to the atmosphere, together with particles (hollines) in coal, if smokes are not well debushed.
• Fossil fuels are not an infinite source of energy, therefore their use is limited by the availability of reserves and/or their economic profitability.
• They adversely affect river ecosystems when refrigeration is made through the water of the river in question (which is not common, because it is more efficient to do so by vaporization).
• Sustainable Development Goals condemn the use of coal as fuel: SDG 7 ensures access to affordable, reliable and sustainable energy from renewable sources.