Mankind always tried to find ways to produce and store energy. Since ancient times, running water has powered mills, fire has cooked food and wind has pushed vessel sails. However, men started to control the earthly elements in a more ingenious and rich way, by combining energy and matter to devise new materials to control nature forces.

Daylight was no more the only source of light when we started keeping fire inside lamps. Then, with the invention of electricity, lamps became ubiquitous, lighting entire cities 24 hours a day. But, how does this happen? Learn where the main energy sources used by human beings come from and how we convert such energy to meet our daily needs.

Fossil Fuels

This is the main way mankind gets energy out of the planet and makes up 81% of the world energy matrix. Fuel fossils such as coal, petroleum, natural gas and fuel oil are formed by the deposit of organic matter on land or water. Over the course of thousands of years, dead plants and animals, in certain places, had their fossils exposed to pressure and temperature that allowed the formation of liquids and gases we use as fuels today.

In Brazil, fossil fuels make up 63% of the entire energy matrix. They can be burned at thermal power stations for instance, producing high temperatures to heat the water. Then, steam is produced under high pressure and finally used to spin the turbines that generate power. Power distribution companies are in charge of delivering electric power to factories, commerce and residences.

In many countries, natural gas is also used as a heat and light source, feeding the fire to heat stoves and showers. Coal is used to produce electric power at thermal power stations and as raw material to manufacture steel at steel producers.

Petroleum, in turn, has the most comprehensive use among all fossil fuels. Besides setting into motion many transportation types, from private cars to trains, helicopters and airplanes, it is also a raw material for different types of plastic and rubber. Pipes, furniture, pillow foams, mattresses and pads, pens, toys, cups, plates and even clothes and shoes use plastic fibers made out of petroleum.

Although a very important energy source, the use of fuel fossils has been criticized for its emissions of greenhouse gases (GHG). That is a finite and non-renewable energy source, meaning these fuels will run dry and should be replaced, changing the economy direction of the world’s leading suppliers, such as USA and Saudi Arabia, and others. In addition to greenhouse effect, fuel burning (carbon dioxide and sulfur, for example) may contaminate air and water, causing acid rains and other atmospheric phenomena hazardous to health. That’s why it’s crucial to seek alternative urgently and try to replace these known fuels with biofuels.

Goal 7 out of the 17 UN’s Sustainable Development Goals includes the need for “ensuring access to affordable, reliable and modern energy for all.” The goal also reinforces international cooperation to allow clean energy researches and technologies, including renewable sources, energy efficiency improvement and promote investment in infrastructure.

Water power (hydropower)

Hydropower, or water power, requires significant infrastructure works to produce in large scale. To make a hydroelectric power station operate for example, a dam must be built. Then, a significant volume of water is stored, which will slowly be released and under great pressure to make the hydraulic turbines revolve and generate electric power.

Hydraulic power accounts for 18.7% of all energy and electric matrices in the world, and 80.2% of Brazilian matrices. That is a controversial source, since it requires flooding large areas and may impact the fauna and flora of a region. However, in the long run, the cost of this energy is low and, once installed, it is often less harmful to the environment compared to other matrices.

Water force can also be exploited to generate energy – and we should remember how a tide is caused. Tides are influenced by the attraction forces (gravity) that the Sun and the Moon exert on our planet. The more aligned are the Sun, the Moon and the Earth, like it happens at New Moon, the greater their effect on the rising of the tides. At Waning Moon, the tides lower and, at Full Moon, there is a new rise. Finally, at the Crescent stage, the Moon and the Sun are at balance, making tides more stable.

So, marine energy, or tidal energy or power, is a renewable source – as water and ocean motion is a continuous, natural and abundant phenomenon – and clean, since it does not pollute nor contribute to global warming.

In Brazil, a pilot project was installed in 2012 at the power station of Porto Pecém, in the Brazilian northeast state of Ceará. The site generation potential is about 100 kilowatts (KW) used to supply power to Ceará main port. However, it is estimated that Brazil’s 8 thousand kilometers long (5 thousand miles) coast can host tidal power stations with capacity for generating 87 gigawatts. From the total produced, 20% would be converted into electric power, the equivalent of 17% of Brazil’s installed capacity.

In the Pecém project, the station produces energy from waves and uses huge mechanical arms connected to buoys, leveraging the water movement to set generators into motion, similar to hydroelectric power system. In Ireland, a similar project developed in 2008 uses 41-meter (135 miles) height underwater turbines. The water movement caused by marine currents makes the turbine spin 12 times a minute. The speed is low and does not impact marine life, but enough to generate 1.2 megawatt and supplies 1,000 households. According to EPE (Energy Research Company), the potential estimated for the world marine energy is 22 thousand terawatt-hour (TWh) a year, from which 200 Twh would be usable. But methods for large scale energy production are still underway.

Sun power (solar)

Solar energy is vital for maintaining life and organization on the planet. Plants grow toward sunlight and use it in the photosynthesis process, producing their own food from this contact with the Sun. Humans need the Sun to organize sleep cycles and, consequently, produce hormones. Our skin also absorbs sunlight and makes our body produce vitamin D, crucial for maintenance of bones, nails, hairs and others. The Sun is now playing another important role: supplying a renewable and low-polluting energy matrix.

Aneel (National Energy Agency ) data shows that, for the past five years, the number of connections to energy micro-generation rose from 23 to 30.9 thousand – and 99% of this amount is solar energy. More than two thirds of connections were made by domestic consumers. Solar panels take advantage either of sunlight and Sun heat to produce electric power. Electricity can be directly generated from sunlight (photovoltaic panels) or by means of heat utilization (solar thermal power plant). Photovoltaic panels can be installed on roofs or covers and the solar matrix is considered fast, effective, cheap and clean, since they do not generate waste.

But, since nothing is perfect, solar energy is an intermittent source of energy. That means it cannot be produced all the time. At plants in cold and with low incidence of solar radiation regions, or on cloudy and rainy days, production declines and the supply gets compromised; thus, redundancy is required, that is, having more than one source of energy to cover downtime caused by weather conditions.

Brazil has a solar incidence of 5.4 kilowatt-hour/square meter, but the installed capacity for photovoltaic power generation is only one gigawatt. China, the world leader, has 130 gigawatts of installed capacity. By 2024, 886.7 thousand solar energy generating units will be installed in Brazil, amassing a total potential of about 3.2 GW. According to the Ministry of Mines and Energy report, as of July 2018, electric power consumption reached 47,534 GWh, considering self-production and losses.

Wind energy (aeolian)

The movement of air masses is the source of wind energy. Turbines installed on towers at 150 meters (93 miles) height transform winds into kinetic energy. The helix spins and triggers the wind turbines that produce electricity to supply households, companies and factories. Smaller and more rudimentary versions have been used for millions of years to pump water and crush grains. The difference is that now these turbines are more efficient and used in large scale to produce electric power.

Globally, the installed generation capacity of wind energy is 539.58 gigawatts, from the total of 25,570 Twh produced in 2017. Brazil ranks 8th in the top 10 countries with highest installed wind energy capacity, having 12,76 GW of generation. Today, 500 Brazilian wind farms supply 11% of the country during “wind harvest season”, ranging from June to November.

Wind energy matrix is considered clean, as it does not generate any type of waste. It is cheap, renewable and does not contribute to greenhouse effect. However, it’s an intermittent source – it stops operating when there is no wind – and it needs vast fields to be installed. Additionally, its environmental impact should be assessed, as the helix blades can hit flying birds, harming species in the wind farm areas.

Because the towers need to be high, installation also changes the region’s landscapes significantly. Another side effect: the sound of wind hitting the blades makes constant noise. The nearest residences are recommended to be at least 200 meters (656 miles) away.

Atom energy (nuclear)

Atomic energy, also known as “nuclear energy”, is created by fission, or splitting, of atom nucleus, a process that releases a great amount of energy. A nuclear plant uses fission energy to generate heat inside a reactor that turns water into steam, then moves the turbine, and finally produces electric power. The final process is similar to that of a thermal power station. Currently, the United states leads the production of nuclear energy, but the most dependent countries on this matrix are France, Sweden, Finland and Belgium. In France, 80% of electricity comes from atomic plants.

Atomic sources are considered a clean energy source because they do not generate waste and the plants can be fixed in small areas. However, atomic waste arising from activity at a nuclear plant using uranium or plutonium  has no utility or a safe destination. Plutonium waste, for instance, takes about 24 thousand years to drain half of its radioactivity. This source is also exhaustible and non-renewable, although uranium and plutonium reserves are much larger than fossil fuel reserves. But its use is criticized because risks in case of accident involve compromise of life in surrounding areas, especially human’s.

If a nuclear energy leak occurs, radioactive pollution of air, Earth and groundwater may impact people’s health for decades to come. Today, Brazil has two nuclear power plants: Angra 1 and Angra 2, which have potential for generating 2 megawatts or 4.2% of all energy produced in the country. Globally, nuclear energy accounts for 15.6% of energy and electric matrices.

Nuclear energy is used not just to produce electric power. The radiation can also be applied in medicine (X rays and radio therapy, for example), manufacturing industry, pharmaceutical in particular, in agriculture (to promote oriented mutations for genetic improvement) and in archeology (to assess dating of ancient objects).

Waste-to-energy (biomass)

Renewable and inexhaustible source, biomass is generated from short-term decomposition of organic materials such as manure, food scraps and agricultural waste. Through combustion, gasification, fermentation processes and liquids arising from material decomposition, biomass may generate electricity, heat and even biofuels. This source is considered a clean source of energy, as it gives new use to waste that otherwise would end up in landfills or dumps. Biomass can also be burned directly in the wood stove, to make use of heat, or it can be used to heat water and produce steam under high pressure, which is used to trigger turbines and electric generators.

In Brazil, biomass is used to generate electricity – usually coming from sugarcane, but biomass can also be generated from compounds such as ethanol, vegetable oils and fats, bio-oil, biogas , BTL (biomass-to-liquids) and biodiesel, they are processed and used as fuels that replace their fossil versions to feed cars and machines. Biomass accounts for 8.2% of the Brazilian electric matrix and 2.2% of the world’s electric matrix.

It is worth noting that biomass burning and its derivatives trigger the release of carbon dioxide and other greenhouse gases into the atmosphere. In this sense, this specific reuse of biomass cannot be considered 100% clean.

Published 22 November 2018

Content published in November 22, 2018