Renewable energy

At this moment the world still relies heavily on non-renewable energy sources, such as natural gas, oil and coal. The burning of these fossil fuels generates energy but also produces carbon dioxide (CO₂), a well-known greenhouse gas that contributes to global warming and climate change.

The earth’s temperature and sea level rises and scientists of the UN’s environment panel (IPCC) conclude that global warming is mostly caused by human activities that increase the amount of greenhouse gas in the atmosphere.

Importance

Therefore, investing in renewable energy is paramount in order to reduce emissions and address the problems caused by global warming. Moreover, we must not forget that non-renewable energy sources are finite and will in time become too expensive to retrieve.

What is renewable energy?

Renewable energy, sometimes also referred to as green or sustainable energy, is energy that is generated by using a natural resource, such as the sun, wind, water or earth. These sources are infinite and are constantly replenished.

More importantly, electricity production by using renewable energy does not directly contribute to greenhouse gas emissions. Although, it must be said that renewable technologies do have a carbon footprint, mostly related to the manufacturing and transportation of said technologies.

Commonly used sustainable energy technologies are:

• Solar power: converting sunlight to electricity using the photovoltaic effect
• Wind power: converting wind (air flow) to electricity
• Ocean power: using the power of moving water, such as tides or currents, for generating electricity
• Hydroelectric power: using the power of falling or fast flowing water for electricity
• Biomass and biofuels: burning renewable organic matter for energy
• Geothermal energy: using the earth’s internal energy for power production and heating

Around 10 – 11 percent of all consumed energy comes from renewable sources (data: 2017). This is also visualized below.

Infographic – energy consumption worldwide

Non-renewable

Fossil fuels are non-renewable because they took millions of years to be formed and are not replenished in a short time. Burning fossil fuels releases CO₂ and will thus contribute to a net increase of CO₂ in the atmosphere.

Fact: fossil fuels are called ‘fossil fuels’ because they were formed by very old remains of organic matter such as animals and plants.

Alternative

Renewable energy and alternative energy are sometimes confused with each other. The main difference is that alternative energy comes from non-renewable resources but that it has lower emissions than regular non-renewable energy sources.

Alternative energy sources include:

• Fuel cells
• Waste energy

The most common renewable energy sources are explained below.

Solar

It is important to state that most renewable energy comes either directly or indirectly from the sun. The sun partially drives the winds (wind power) and causes biological material (biofuels) to grow.

The sun provides life on earth and can be seen as the most powerful source of energy. It has an enormous potential: the solar energy that reaches the earth in one hour is more than the total amount of energy that is consumed in one year.

Hence, it is no surprise that solar radiation is utilized by technologies to be converted to heat or electricity that can power homes, infrastructure, industries and businesses.

Technology

Solar radiation can be converted into electricity in two different ways.

• Photovoltaic (PV) effect: panels with solar cells can catch sunlight and can convert it into a voltage and current to generate power.
• Steam generation: the heat of solar radiation can be used to heat a liquid and produce pressurized steam to generate electricity. The principle is the same as in a steam train, instead the steam is used to power a generator which can convert power to electricity.

Sunlight can also be used to heat water using a thermal collectors and a storage tank for water. These systems contribute to a lower (methane) gas consumption in households.

Benefits and limitations

Solar energy has its benefits and limitations:

Wind

The power of the wind can be used to generate electricity. This is a sustainable method because no greenhouse gasses are emitted in the electricity generation process.

Wind turbines, however, do have a small carbon footprint. This is because it takes energy to retrieve and transport the materials needed to manufacture the wind turbine. This energy is usually comes from burning fossil fuels.

Technology

A wind turbine catches the wind due to the shape of its blades. The kinetic energy is transferred from the blades to a shaft and gearbox that drives a generator which is connected to the electricity network.

Source: solar.excluss.com

Ideally a wind turbine is positioned around 30 meter above ground level because they can then take advantage of faster and less turbulent wind speeds.

There are different types of wind turbines being used, however, the most cost effective designs use a horizontal axis. These wind turbines are often found in large numbers in fields (wind farms), but also off shore. Stand-alone turbines are usually used by farmers or house owners that live in windy areas.

Advantages

1. The net emissions of CO2 (per kWh) are 50 times lower when compared to burning fossil fuels. Only the manufacturing (including transportation) of wind turbines contributes to the greenhouse effect
2. An average wind turbine produces 80 times the energy that was needed for the manufacturing process of the turbine
3. The wind is an infinite energy source
4. The technology behind wind turbines is under continuous development. Blades are getting more and more effective and cheaper to produce

Disadvantages

Wind energy definitely has potential, however, some downsides must be addressed in order for wind energy to become a major renewable energy source.

1. Electricity generated by wind power relies for a large part on subsidies. Burning fossil fuels is still much cheaper per kWh
2. A large number of turbines is required make an actual contribution to the electricity network
3. Wind turbines are often criticised for spoiling the landscape (visual impact) and causing noise.

Biomass and bio-fuels

Biomass and bio-fuels are organic materials that are derived from living things, such as plants, humans and animals. This matter is renewable because it contains energy from the sun and can be replenished in a relatively short period of time.

Carbon in biomass is part of a natural cycle: plants and trees take carbon dioxide while they grow and release carbon dioxide when they are either burned or decomposed in a natural way.

Renewable on condition

This means there is one condition for biomass to be truly renewable: the natural cycle of biomass should not be disturbed. In other words, for the natural cycle to remain in balance, the amount of carbon dioxide taken from the atmosphere should be equal to the amount of carbon dioxide released.

For example, for every tree that is harvested and burned for energy production a new tree or plant should be planted to take the carbon dioxide that is emitted during the power generation process (burning of biomass).

Technology

Different types of biomass can be used for energy generation such as wood, garbage, crops, landfill gas and alcohol fuels.

Burning biomass is the most common method of generating energy:

1. Solar energy assures photosynthesis and causes organic material to grow. This material can be harvested as biomass.
2. Burning the biomass can be used to heat water in a special boiler or container
3. This releases heat in the form of fast moving steam
4. The turbine translates the moving steam to kinetic energy that drives a generator
5. The generator translates kinetic energy to a voltage and current to produce electricity for homes and businesses

Source: eschooltoday.com

Another method is to convert biomass in usable fuels, such as ethanol, bio-diesel or methane. This can be done using fermentation or decomposing the material in special containers.

Benefits and limitations

Bio-energy has its benefits and limitations:

Hydro

Hydro power is one of the main forms of renewable energy in the world. It was already being used thousands of years ago to turn wheels to grind materials such as grain. There are different ways to use water generate energy:

• Using fast running water (currents) in a river
• Using falling water
• Using tides and waves (ocean power)

The acquired energy can be used for various purposes such as electricity generation or powering mechanical devices.

There are more than 11.000 active hydro power stations in more than 160 countries.

Technology

The principle of generating hydro energy is similar to generating wind energy. Instead, moving water has kinetic energy that can drive shafts on a turbine. This turbine drives a generator which transfers kinetic energy to electrical power.

Source: eschooltoday.com

The volume and the change in elevation or the strength of tides will determine how much energy can be produced.

Advantages

Falling water can produce electricity at a constant rate

1. There are no greenhouse gas emissions
2. The amount of electricity produced can be regulated by opening and closing water entrance gates
3. Storage lakes used for dams have several uses such as irrigation, leisure and providing drinking water

Disadvantages

While hydro power is a sustainable method for producing electricity there are still some downsides must be addressed.

1. Hydroelectric power stations are often large and expensive to be built and maintained
2. A lot of countries cannot use hydro power because there are no areas to where a dam or hydro power installation would be effective
3. Risk of floods (applicable for dams only)
4. Dams can cause geological damage and disturb the habitat
5. Dams block the natural flow of water and may lead to problems related to the water supply for locations (countries) that are further along the river

Geothermal

Geothermal energy is stored below the surface of the earth. This heat can be transferred as either hot water or steam to generate electricity or provide central heating for houses and other buildings.

Geothermal energy is renewable because there is a constant replenishing of heat due to decaying radioactive particles far below the earth’s crust.

Technology

There are in principle two different kind of technologies to use geothermal energy:

1. Drilling tubes into the ground far enough to tap hot water that can be used in for heating homes and buildings or tapping steam to generate electricity.
2. Another method (explained in image below) is to run cold water deep into the ground through a network of tubes. The water is then heated by the earth which forms steam. This steam can drive a turbine to generate electricity.

Source: enviropol.com

Geothermal energy  is most successful in areas with high geothermal activity such as areas with young volcanoes.

Benefits and limitations

Geothermal energy has its benefits and limitations:

Renewable energy in the Netherlands

The Netherlands is behind most other EU-countries in terms of renewable energy production. At this moment (2016) the percentage of consumed renewable energy is only around 6 percent. Most important renewable sources are biomass and wind energy. The geography of the Netherlands limits the potential for hydro- and geothermal power.

Policy

The Dutch government actively encourages the production and consumption of sustainable energy such as wind and solar. This is done by providing subsidies for investors, households and small businesses. This policy is aimed to make The Netherlands less dependent on fossil fuels and lower global carbon emissions.

Conserving energy and maintaining an adequate energy supply is also an important policy topic. Hence, the Dutch government has decided to allocate more resources to conserve energy.

By 2020, the share of renewable energy must have grown to 14 percent of the total energy consumption. The long term goals (2050) of The Netherlands aim for a switch to a sustainable economy and low carbon emissions using a mix of energy sources:

• Gas
• Oil
• Nuclear
• Renewables

Most coal-fired power plants in The Netherlands will be shut down in the following decades.

Sources

The following websites where used to compile this dossier:

• http://www.ren21.net/GSR2016-Renewables-2016-Global-Status-Report-Key-Findings-EN
• http://enviroliteracy.org/energy/renewable-energy/
• http://www.eschooltoday.com/energy/renewable-energy/biomass-energy.html
• http://enviropol.com/index.php/geothermal-energy
• http://www.eia.gov/energyexplained

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