(Transcript of the video commentary.)
The history of the use of energy from renewable sources dates back to the beginnings of human development. Whether it was burning biomass in fireplaces, using wind to propel sailboats or heating homes with hot thermal springs, it was always energy from natural, constantly renewing processes. Energy from fossil fuel sources only started gaining ground in the last few centuries, mainly due to the development of industry and increased demand for energy. In connection with climate change and global warming, humankind is returning to the constantly more common use of renewable energy sources.
One of the definitions of renewable resources says that they are non-fossil fuel natural energy sources that have the ability to partially or completely renew themselves when gradually consumed. Such sources include energy from sunlight, water, wind or biomass, originating primarily from the Sun or geothermal energy, which is the result of heat generated inside the Earth.
The main use of renewable energy lies in the production of electricity, where it is successfully and increasingly replacing the burning of fossil fuels. Some countries already achieve a high integration of renewable sources in their electricity networks today, but the trend of increasing the share of renewable sources in the energy portfolio is visible worldwide. In recent years, more than 2/3 of newly installed energy sources were renewable and the share of these sources in electricity production was almost 1/3.
In the field of heating and water heating, the most widely used renewable resource is biomass when burned in ecological boilers of individual and community heating systems. The direct use of geothermal energy is also increasingly involved in heating, of course especially in areas where conditions are favourable for this. Heat pumps have also noticed a massive expansion recently, which can provide cooling of objects in addition to heating. Domestic hot water is being prepared using solar heating more often. Various types of solar collectors are used by tens of millions of households to cover at least part of their hot water needs.
A third area where renewable sources provide energy is transportation. The most common biofuel, at least in Europe, is biodiesel produced from vegetable oils and fats. It is used as an additive to conventional diesel to reduce emissions of particles and hydrocarbons. Cellulosic biomass or carbohydrates produced in certain crops such as corn or sugar cane can be fermented to produce bioethanol. Similar to biodiesel, this technical alcohol is also added as an additive to petrol to reduce vehicle emissions. In transport, renewable sources are also used to charge electric cars and other electrically powered vehicles.
Among the most well-known types of carbon-neutral renewable sources suitable for electricity production are the use of water energy, wind energy and the direct or indirect use of solar energy. Biomass and geothermal energy are mostly used to produce heat, although it is also possible to produce electricity from them. The development of technologies enabling the use of individual sources increases their efficiency, availability and competitiveness and the cost of installation decreases. All this leads to a gradual increase in the share of renewable sources in total energy production.
Hydropower is very popular and it can be said to be the most important renewable resource. It uses the potential, kinetic, as well as thermal energy of water masses on the Earth, which is constantly renewed through the natural cycle of water in nature. Since the original propulsion of mills and simple machines, hydropower technologies have improved, and the predominant way of using water energy today is the production of electricity in hydroelectric power plants. Whether they are large dam power plants, medium flow or small river hydropower plants, water turbines ensure the conversion of water energy into usable mechanical work.
The second most widespread renewable resource is wind. Wind energy is available almost anywhere and its use provides clean energy without any emissions or waste. Modern, industrially produced wind turbines with a unit power of up to several MW can stand alone or they can be combined into large wind farms in suitable locations with constant and strong winds. In addition to higher locations on land, open areas above the level of the world’s seas and oceans are promising places for the installation of wind parks. Even though large wind farms are noticeable in the landscape, they have virtually no negative impact on the surrounding environment.
Of course, the list of the most important renewable sources must include solar energy transmitted from the Sun to the Earth in the form of radiance. Its use for energy purposes can be purely passive, for example by orienting buildings towards the Sun or active, including solar technologies for heating and water heating, as well as technologies for converting solar energy into electricity either directly using photovoltaics or indirectly using concentrated solar energy. Photovoltaic power plants are currently experiencing rapid growth with the associated reduction in production costs and greater expansion. A large number of these decentralized resources, as well as large solar farms with an output of hundreds of MW are beginning to find a place in modern energy strategies.
Another renewable source with interesting potential is geothermal energy. It is actually the use of the Earth’s thermal energy, released during the decay of radioactive elements in its core. Unfortunately, there are not many suitable places for the construction of geothermal power plants with a larger installed output, which is why these cheap and ecological resources are rather local. Far greater use of geothermal energy can be expected in the form of thermal energy for heating or cooling.
The last significant non-fossil renewable resource containing bound chemical energy is biomass. In addition to well-known plant and wood material, biomass also consists of animal waste and organic components of municipal and industrial waste. For energy purposes, biomass is most often burned in biomass power plants and cogeneration units. Biomass also plays an important role in the production of alternative biofuels using thermal, chemical or biochemical conversion methods.
