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What is renewable energy?

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Energy exists freely in nature. Some of them exist infinitely (never run out, called RENEWABLE), the rest have finite amounts (they took millions of years to form, and will run out one day, called NON-RENEWABLE)

With this in mind, it is a lot easier to lay any type of energy source in its right place. Let’s look at these types of energy in the diagram below:

pYou will notice that water, wind, sun and biomass (vegetation) are all available naturally and were not formed. The others do not exist by themselves, they were formed. Renewable energy resources are always available to be tapped, and will not run out. This is why some people call it Green Energy.

TIP

Approximately 20% of electricity produced globally in 2009 came from renewable sources. Out of this, hydro-power accounted for about 16%.

In 2012, 9% of the energy consumed in the USA came from renewable sources. This means the USA depends a lot on non-renewable sources. 30% of the energy from renewable sources came from hydropower, whiles biomass, biofuels and wood, together accounted for about 49%. —Source: USEIA, Monthly Energy Review, April 2013

When can energy be called ‘Renewable’?

When its source cannot run out (like the sun) or can easily be replaced (like wood, as we can plant trees to use for energy)

When their sources are carbon neutral. This means they do not produce Carbon compounds (such as other greenhouse gases).

When they do not pollute the environment (air, land or water) Renewable energy includes Biomass, Wind, Hydro-power, Geothermal and Solar sources.

Renewable energy can be converted to electricity, which is stored and transported to our homes for use. In this lesson, we shall take a closer look at how renewable energy is converted into electricity.

What is Biomass

Biomass fuels come from things that once lived: wood products, dried vegetation, crop residues, aquatic plants and even garbage. It is known as ‘Natural Material’. Plants used up a lot of the sun’s energy to make their own food (photosysnthesis). They stored the foods in the plants in the form of chemical energy. As the plants died, the energy is trapped in the residue. This trapped energy is usually released by burning and can be converted into biomass energy.

Wood is a biomass fuel. It is renewable. As long as we continue to plant new trees to replace those cut down, we will always have wood to burn. Just as with the fossil fuels, the energy stored in biomass fuels came originally from the Sun.

It is such a widely utilized source of energy, probably due to its low cost and indigenous nature, that it accounts for almost 15% of the world’s total energy supply and as much as 35% in developing countries, mostly for cooking and heating. (More reading on Bioenergy or Biofuel here)

How is biomass converted into energy?

Burning:

This is a very common way of converting organic matter into energy. Burning stuff like wood, waste and other plant matter releases stored chemical energy in the form of heat, which can be used to turn shafts to produce electricity.

Let’s see this simple illustration of how biomass is used to generate electricity.

1. Energy from the sun is transferred and stored in plants. When the plants are cut or die, wood chips, straw and other plant matter is delivered to the bunker

2. This is burned to heat water in a boiler to release heat energy (steam).

3. The energy/power from the steam is directed to turbines with pipes

4. The steam turns a number of blades in the turbine and generators, which are made of coils and magnets.

5. The charged magnetic fields produce electricity, which is sent to homes by cables.

Other ways in which organic matter can be converted into energy include:

Decomposition:

Things that can rot, like garbage, human and animal waste, dead animals and the like can be left to rot, releasing a gas called biogas (also known as methane gas or landfill gas). Methane can be captured by a machine called Microturbine and converted into electricity. Sometimes, animal waste (poop) can also be converted into methane by a machine called ‘Anaerobic Digester’

Fermentation:

Ethanol can be produced from crops with lots of sugars, like corn and sugarcane. The process used to produce ethanol is called gasification.

What is Wind Power?

Wind is caused by huge convection currents in the Earth’s atmosphere, driven by heat energy from the Sun. This means as long as the sun shines, there will be wind.

How do winds form? (Check out the lesson on winds here)

This can be explained in simple terms by the daily wind cycle.

The earth’s surface has both land and water. When the sun comes up, the air over the land heats up quicker than that over water. The heated air is lighter and it rises. The cooler air is denser and it falls and replaced the air over the land. In the night the reverse happens. Air over the water is warmer and rises, and is replaced by cooler air from land.

The moving air (wind) has huge amounts of kinetic energy, and this can be transferred into electrical energy using wind turbines. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. The electricity is sent through transmission and distribution lines to a substation, then on to homes, business and schools.

Wind turbines cannot work if there is no wind, or if the wind speed is so high it would damage them.

Wind turbines are usually sited on high hills and mountain ridges to take advantage of the prevailing winds.

Just like a windmill, wind energy turbines have been around for over 1000 years. From old Holland to farms in the United States, windmills have been used for pumping water or grinding grain. (More on Wind Energy here)

Did you know… The largest wind turbine in the world, located in Hawaii, stands 20 stories tall and has blades the length of a football field.

An average wind speed of 14 miles per hour is needed to convert wind energy into electricity.

One wind turbine can produce enough electricity to power up to 300 homes. The first power-generating turbine was constructed in Ohio during the late 1800’s and was used to charge batteries.

Wind energy is the fastest growing segment of all renewable energy sources.

Water power

Moving water has kinetic energy. This can be transferred into useful energy in different ways. Hydroelectric power (HEP) schemes store water high up in dams. The water has gravitational potential energy which is released when it falls.

Let’s see a good example of how water can be used to generate electricity.

The Dam is built to retain the water. More electricity is produced if the water is more in the reservoir

Sluice Gates: These can open and close to regulate the amount of water that is released into the pipes.

Potential energy in the retained water is transferred into kinetic energy by water flowing through the pipes with high speed.

The force and high pressure in the water turns a series of shafts in a generator. Spinning shafts in the generator charges millions of coils and magnets to create electricity, which is regulated by a transformer. This is then transported via cables to homes and factories.

To build a dam there has to be valleys and rivers that flow all year round. This will help with the building and success of the dam. This way, the fullest effect of the waters kinetic energy can be tapped.(Click for more on hydro energy)

Did you know…

Hydropower is renewable energy source that doesn’t cause global warming because it doesn’t releases dangerous greenhouse gases.

China is the largest producer of hydroelectricity, followed by Canada, Brazil, and the United States (Source: Energy Information Administration).

Hydropower is the most important and widely-used renewable source of energy.

Geothermal energy

Deep down in the earth’s crust, there is molten rock (magma). Molten rock is simply rocks that have melted into liquid form as a result of extreme heat under the earth. This can be found about 1800 miles deep below the surface, but closer to the surface, the rocks layers are hot enough to keep water and air spaces there at a temperature of about 50-60 degrees F (10-16 degrees C). Geothermal technology takes advantage of the hot close-to-earth-surface temperatures to generate power.

In places with hotter ‘close-to-earth-surface’ temperatures, deep wells can be drilled and cold water pumped down. The water runs through fractures in the rocks and is heated up. It returns to the surface as hot water and steam, where its energy can be used to drive turbines and electricity generators. (Note that there isn’t any technology that allows humans to tap the heat from molten rock yet. Maybe one day, there will be)

In other places, a geothermal heat pump system consisting of pipes and pumps buried in the earth can be used to heat homes. This is done by opening up the system, extracting the hot air to feed indoor air delivery system during the cold seasons. In the USA, some geothermal systems can be found in Hawaii and Alaska.

Geothermal energy is called a renewable energy source because the water is replenished by rainfall, and the heat is continuously produced by the earth. (More on Geothermal Energy here)

Solar power

Solar power is energy from the sun. “Solar” is the Latin word for “sun” and it’s a powerful source of energy. Without it, there will be no life. Solar energy is considered as a serious source of energy for many years because of the vast amounts of energy that is made freely available, if harnessed by modern technology.

It is renewable!

It is considered ‘Renewable Energy‘ because…

The technology used to convert the sun’s power into electricity does not produce smoke (carbon dioxide and other air pollutants).

Tapping the sun’s energy does not usually destroy the environment.

Unfortunately, the sun does not available in the night, and in some days, clouds and rains and other natural conditions prevent the sun’s powerful rays to reach us. This means that it is not always available. This a why we cannot rely on solar energy alone.

Solar cells

Solar cells are devices that convert light energy directly into electrical energy. In these cells, there are semiconductors (silicon alloys and other materials). You may have seen small solar cells on calculators or some mobile phones. Larger arrays of solar cells are used to power road signs, and even larger arrays are used to power satellites in orbit around Earth. Solar cells are also called photovoltaic cells or PV devices.

Solar panels

Solar panels are different to solar cells. Solar panels do not generate electricity directly. Instead they heat up water directly. A pump pushes cold water from a storage tank through pipes in the solar panel. The water is heated by heat energy from the Sun and returns to the tank. They are often located on the roofs of buildings where they can receive the most sunlight.

There is also the Solar Thermal Power Plant. Here, a concentration of the sun’s energy by many panels is used to heat up water into steam, which is then used to turn turbines to produce electricity.

Guess what! Power stations of this nature usually need a lot of space to capture a lot of the sun’s energy!

The Parabolic Trough System uses this kind of system. Here, troughs are designed to direct the sun’s energy to absorber tubes as long as the sun is up.

Many of these Parabolic troughs are installed to collect massive energy for the rods to heat water to turn turbines.

Other less common methods that use the Solar Thermal Power Plant system are the Solar Dish and The Solar Power Tower.

Did you know… In many African villages, the people use the sun’s energy to dry food-stuffs like fish, corn, snails, and cocoa for storage? That is raw solar energy in use. They spread the foods on large mats and trays in the hot sun for days until the required dryness is attained. This is common in regions with lots of sun.

Marine (Ocean) Energy

The oceans have incredible amount of power and energy potential. Even though the marine energy technology has not fully delivered on its potential, there has been, in recent time, a number of areas in marine energy that has kicked off. The UK is believed to be a leading player in Marine energy. Even though its capacity presently is only about 9megawatts, it is on course to deliver about 120MW by 2020. Two of these are Wave energy and Tidal Energy.

Wave Energy: How does it work?

Wave energy (WE) harnesses the kinetic energy in the up-and-down movement (waves) of water in the ocean. The waves are caused by wind action, and wind action is caused by the sun heating the surface of the waters, generating air pressure. This means as long as there is the sun, there will be wind and waves, even though its intensity may vary.

WE locations are best where there are strong winds traveling over very long distances. This makes places like the west coast of UK a great point, because of the winds over the Atlantic.

Wave Energy is captured by devices called Wave Energy Devices. There are several types of Wave Energy Conversion devices including the fllowing:

A. Point Absorber: This floating structure moves up and down and in all directions. With some conversion mechanisms inside it, power is converted and stored in a hub at the base.

B. The Attenuator: This floating device also rides the waves, flapping like the wings of a bird, a movement caused by the pounding waves. The kinetic energy in the movement is converted into energy and stored.

C. The Oscillating Wave Surge Converter: This device extracts energy from the waves of the water. It is installed below the water surface, but the current is strong enough to cause it to oscillate.

How does Tidal Energy work?

Ocean tides are caused by the earth’s rotation, as well as the combined gravitational fields of the earth, sun and moon. This combination shapes the gravitational pull on the earth’s oceans. The oceans tidal stream is even more powerful when wind air pressure systems get involved. Areas with greater current speeds, narrow straits and inlets, as well as channels between islands are perfect locations for installing tidal energy structures.

Some tidal structures (or devices) look a lot like wind energy blades, but this time, installed under water to harness the kinetic energy in the oceans currents. Unlike in wind turbines, the blades in tidal energy devices move a lot slower because of the high density of the medium (water). However, they carry a lot of power.

Some tidal convertors work just like the wind turbines. Kinetic energy from spinning of the blades, caused by the currents is tapped with the help of some convertors inside of the spinning structures to generate electricity.

Examples of tidal energy convertors include the Horizontal Axis Turbine, Vertical Axis Turbine and the Oscillating Hydrofoil.

The world’s biggest Tidal Power Plant is the Sihwa Lake Tidal Power Station in South Korea, with 254MW output capacity. There is also a 240MW output capacity plant in France called La Rance Tidal Power Plant.

What are the problems with Marine Energy?

Marine energy comes with its own problems and challenges. For example the unpredictable changes in wave patterns (extreme tides to very calm waters can cause huge structural damage.

It can also cause overload operation problems. There is also lack of data and information on this new area, and many governments and businesses are less encouraged to jump on board.

Then there is also the environmental concern such as: marine energy facilities may affect wave hydrodynamics, create artificial habitats, concerns with marine animals, noise and so on.

Saving Energy

Just century ago, humans used very little energy because we had less of the things that use up energy. There were no computers, phones, TV, cars, lights, washing machines and all that. After the industrial revolution, people started using a lot more manufactured items such as electronics, automobiles, and home appliances. These items use a lot of energy, but if we all cut our energy use by half, that would be huge savings.

Saving energy can be achieved in a couple of ways:

1.Energy conservation, 2.Energy Efficiency, and 3.Recycling. These first two are not the same, even though people often use them to mean the same thing.

Energy Conservation:

This is the practice that results in less energy being used. For example, turning the taps, computers, lights, and TV off when not in use.

It also includes running in the park or outside instead of running on the treadmill in the gym.

Energy conservation is great because we can all do this everywhere and anytime. It is a great behavior we must acquire.

Did you know:

1. Up to 25% of heat loss is through windows, plastic window covers can help reduce drafts.

2. 85 to 90% of energy used to wash clothes goes to heating water

Energy Efficiency This is the use of manufacturing techniques and technology to produce things that use less energy for the same result. For example if a heater is designed to warm your home with less energy than regular heaters, that would be an energy efficient heater. If your washing machine uses less energy to do the same job as other washers, that is an energy efficient washer.

FACT: Homes built after 2000 are about 30% bigger, but there use less energy than older homes. Source: US EIA survey: RESIDENTIAL ENERGY CONSUMPTION SURVEY (RECS)

Recycling

This involves the use of waste or old materials to make new ones. For example, we can collect all old newspapers from the town at the end of everyday and turn the papers into fresh paper for printing again. We can collect all plastic bottles and send them to be used for new plastic bottles, or used for children plastic toys. (read more about recycling here)

Recycling saves energy because less energy is used to recycle than to turn new raw materials into new products.

This means to save energy, we need to use all these great ways. If we all try do this, together we can save some money and use less natural resources too.