The renewable energies

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Life-cycle assessment (LCA)

Life-cycle assessment or LCA is a technique for assessing the environmental impact that a product or service has throughout its life-cycle. All of the stages involved in a given product's life have to be taken into account: extraction of raw materials, manufacture of the product, its distribution, the product's use, recycling, incineration, removal to landfill, etc.


Plants grow by using sunshine to photosynthesise. This process, whereby light energy is converted into chemical energy, is used by all plants, and is therefore used to create all biomass. The term biomass therefore refers to all organic matter that is produced using biological processes: terrestrial and aquatic plant species, agricultural residue, livestock waste, etc. Wood is the main component found in solid biomass – such as that used in wood boilers. Liquid biomass refers either to vegetable oil (e.g. rape) or alcohol (e.g.: beetroot). Liquid biomass can be used as fuel in thermal combustion engines. Next-generation agrofuel is being developed: microalgae, the parts of plants that are not used by the agro-food sector.

Wind power

Heat from the sun captured by the ground or the oceans' surfaces helps raise the temperature of neighbouring air masses and, in turn, their atmospheric pressure. The pressure differential between two air masses leads to flows between them: the result is wind – the source of wind power. Wind power installations capture the force that the wind exerts on mobile surfaces in order to generate mechanical energy which is then converted into electricity. The blade design is based on the technology used in aeronautics: the blades' geometry has to be such that they can effectively convert the wind's force – in the same way as an aeroplane wing is designed to provide lift. There are horizontal-axis and vertical-axis wind turbines.

Hydraulic power

Hydraulic power is generated by the movement of water. A varied selection of water bodies can generate this power. Hydroelectricity is generated by harnessing water flows in rivers and is the main form of renewable electricity production currently in use. However, relatively little use is currently being made of ocean currents to generate electricity. Wave power is energy generated by the action of the wind on the seas' and oceans' surface, creating waves. In addition to the wind moving the water, there is also the gravitational pull exerted on the Earth by the moon and the sun – the tide.

Solar power

Every second, the sun converts millions of tonnes of matter into heat, resulting in a core temperature of several dozen million degrees Celsius. This heat is radiated throughout space and only a very small amount of it is intercepted by the Earth. In one hour, the sun pours out the equivalent of all the energy that humankind uses in one year. The amount of energy that reaches the Earth's surface over a 12-month period is constant, regardless of the weather. This energy can be converted into heat, mechanical energy or electricity. Examples of solar energy applications: solar water heaters, photovoltaic panels, solar power towers, parabolic Stirling generators, solar power plants with parabolic trough technology, etc.

Renewable energies

An energy source is considered renewable if it can be regenerated or renewed at human scale. Examples of renewable energies are solar power, wind power, hydraulic power, biomass and geothermal power. Celestial bodies such as the sun, the Earth and the moon are the sources of all these energies. As natural resources become increasingly scarce and climate change due to greenhouse gases starts to kick in, the current energy system is becoming difficult to maintain. Finding ways to save energy and manage it more effectively, as well as increasing our use of renewable energies are all becoming inevitable. But the random nature of the planet's weather systems compromises the utility of renewable energies (e.g.: variations in sunshine hours or windspeeds). So, in order to meet energy demand, we need to develop ways to store energy.

Process engineering

Process engineering is where a number of disciplines intersect, drawing on knowledge and expertise for using a succession of operations to create products by industrially transforming natural or synthetic raw materials. Process engineering helps tackle the major challenges facing us in the 21st-century: energy management, making optimum use of raw materials and minimising the damage we do to the environment.

Geothermal power

The decay of radioactive elements contained in the Earth's core releases heat. This heat ensures that the centre remains at temperatures of more than 7000°C. Geothermal energy is this enormous quantity of heat which is able to pass through the Earth's various layers. It is what creates spectacular geological events – such as volcanoes and hydrothermal springs –, as well as thermal gradients. Generally speaking, the temperature increases by 1°C every 30 metres as one burrows down towards the centre of the Earth. The ground is able to store solar energy at depths of up to a few metres and so can give off the heat needed to drive heat pumps with high levels of yield. This is geosolar power.
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Date of update December 5, 2018