Importance of renewable energy

Renewable energy is beneficial for a number of reasons. The renewable energy technologies make use of clean sources of energy and hence would do much less harm to the environment when compared to conventional sources of energy like oil and natural gas. 

The source of energy is infinite, so for generations to come, the source can be used over and over. In other words, it is a much more sustainable option. 

This can also be beneficial to our economy. If Trinidad and Tobago could depend less on our own oil and natural gas for energy, then there would be more barrels of hydrocarbon to be sold and hence more income for the country. 

Renewable energy

Opportunites and Limitations

Opportunities

Solar panels can be installed on the roofs of schools as they are extensive. Wind turbines can be installed in a wide open location on the school grounds.

Once installed, the electricity generated by the solar panels and wind turbines will go to Direct Current (DC) storage batteries via cables. From there, it will travel to inverters where Alternating Current is needed (AC). 

The electricity from the DC storage batteries can be used as follows:

1. To charge computer back up systems.

2. To power cooling systems in classrooms such as fans and air condition units.

3. To power laboratories where it can supply power to power outlets. Can also power extractor fans in laboratories. 

4. Indoor lighting: Light Emitting Diodes (LED's) can be connected through a battery charged system which is charged by solar panels during the day. 

5. Outdoor lighting at night: This uses the same procedure for indoor lighting. In this situation, the solar panels charge up the battery system during the day. These batteries will then run at night when the sun is not available.

6. Can be used to heat water for showering:

• Tubes of water can be placed on the roof which will be heated via the sun's energy and this water will be pumped into a water heater. You can run a DC motor which will slowly circulate the water in a tank and from the tank to the shower.
• In situations when no sun is available, you can have a system that is connected to a solar battery charger that can run a DC pump and a water heater for hot water. 

Limitations

Even with so many benefits and opportunities, there are limitations that exists when using renewable energy.

1. Not all schools will have enough funds for the initial cost of the equipment. Even if they apply to the government for assistance, this can be a lengthy and frustrating procedure.  

2. To receive maximum sunlight, the solar panels may have to be tilited at an angle. This requires mounting equipment which is an additional cost.

3.  Not all schools have a wide open area for the installation of wind turbines. If they do, this area is usually used for recreational activity such as physical education for the students. In addition to this, trees may need to be cut down, to allow as much wind energy as possible. This destroys the existing landscape.

4. In urban cities, there are a lot of tall buildings nearby each other, blocking out wind energy. The wind turbines therefore may not receive as much wind energy as they need

5. In order to receive electricity from the solar panels and wind turbines, electrical wires need to be run. Wires on the school compound poses danger to students. 

6. Some schools may not be able to afford maintenance of the equipment in unexpected situations such as hurricanes.

What is solar energy?

Solar energy is energy that is given off by the sun.

Sun

How does solar energy work?

The light that we receive from the sun has energy. When this light hits objects, the energy turns into  heat. But in some cases, when the light hits objects made of certain materials, the energy turns into electric current. We can now harness this electric current for power.

What is a solar cell or photovoltaic cell?

A solar/photovoltaic cell is a device that takes the energy from sunlight and converts it into electricity. Solar panels are one of the most efficient ways to harness the energy we receive from the sun. These panels are made up of a large number of solar cells. 

Solar panel

How does a solar cell turn sunlight into electricity?

      In a solar cell we have SiO2 which is a crystal, composed of 14 electrons. A silicon atom looks for ways to full up its last shell so it will share electrons with 4 atoms nearby.

See diagram below.

·       However, pure silicon is a bad conductor of electricity since most of its electrons are not free to move around. In order to fix this, the silicon in a solar cell must have impurities. 

N - Type

The process of adding impurities is called doping and when done with phosphorous is called N - type because of the great amount of electrons and it carries a negative charge. N- Typed dope silicon is much better than pure silicon.

When energy is added to the pure silicon, it causes some electrons to break free of their bonds and leave the atom. This leaves behind a hole. These electrons that are free to move about are called free carriers and they carry a current. They move around the lattice looking for another place to fall into. However, since there are such few free carriers in pure silicon, it is not very efficient in terms of the amount of current being produced.

Phosphorous has 5 electrons in its outer shell. So it bonds with the silicon atoms to full up its last shell. However, it leaves behind one phosphorous electron which does not bond. But, there is a positive proton which keeps it in place. 

For silicon mixed with phosphorus; it requires less energy to get rid of electrons in the phosphorous atom. So most of the electrons break free in this case and there are much more free carriers and therefore more current. 

P - Type

In other cases, the solar cell can be doped with boron, which has 3 electrons in its outer shell alone. Instead of having free electrons, the P type has free openings and carries a positive charge. 

So how does it work?

A solar cell has 2 semiconductor layers: A bottom layer which is P type and a top layer which is N type. When these two come together, they form a PN Junction. Electrons from the N side can move across the junction to the P side, causing it to become negatively charged. When these electrons move over to the P side, they can pair up with a hole, creating an electron - hole pair. The reverse applies; holes from the P side can move across the junction and cause the N side to be positively charged. The holes can pair up with electrons to create an electron - hole pair. This charge imbalance on the P and N side creates an electric field. 

When light hits the solar cell in packets of energy, called photons, it breaks apart electron hole pairs, sending the electron to the N side and the hole to the P side. These charges are now separated so there is a difference in potential and a voltage created. 

If we connect the solar cell to an external circuit, this allows the electrons and holes to move around. When the charges move around the circuit, they create and electric current. 

With both a potential difference / voltage and current, we now have power. 

For a more visual understanding, check out the following videos below:

How solar panels work

PN junction solar cells

Benefits of solar energy

1. The energy we receive from the sun is never ending and wide spread. The sun always exists! Even during winter season, some areas still receive a significant amount of radiation.

2. Energy from the sun is free and we do not have to pay for it. No fuel is needed to power it.

3. Solar energy does not pollute the air by releasing harmful gases.

4. Solar energy can be used to harness power in remote locations once sunlight is available.

5. Solar cells are long lasting and do not require a lot of maintenance.

6. Installation of solar panels are fairly easy. These panels are usually placed on roof tops which means that no space needs to be created.

7. New technological advances have increased the rate of efficiency of solar panels from 40% to 80%.

Limitations of solar energy

1. The initial cost to implement solar panels is high but we can assure you that within the years to come, it will definitely be worth it!

2. Solar panels require a substantial amount of area clear of shadows. Overcast and cloudy areas, together with buildings covered by trees, will produce electricity at a much slower rate since it blocks out sunlight.

3. Solar panels are not effective at night due to its reliance on sun rays. Therefore a utility grid power system would be needed.

4. For large scale companies, the solar panels need to occupy a significant amount of space for the system to work efficiently to provide electricity for the whole area.

What is wind energy?

Wind is caused by large scale convection currents in the Earth’s atmosphere. This wind is driven by heat energy from the sun and we can therefore say that it is a product of solar energy.

The energy we get from the wind is kinetic energy and we can harness that energy by using wind turbines and convert it into electricity. 

Wind

Basics of Wind Energy

To understand how wind energy works, we must first of all, understand the daily wind cycle.

During the day when the sun is out, the air over the land heats up faster than the air over the ocean. This heated air is lighter and therefore rises. The cooler air is denser and falls. The rising and falling of air creates convection currents.

During the night, it is the opposite. The air over the ocean maintains heat longer than the air over the land. The air over the ocean now rises and the air over the land falls.

This air that moves carries a lot of energy with it. 

Daily Wind Cycle

How does wind energy work?

Wind energy works through the use of turbines, which provides us with electricity.

Wind turbine

How do we get electricity from wind turbines?

Wind turbine components

• The wind blows on the blades of the rotor, causing it to rotate. This converts some of the wind’s kinetic energy into mechanical energy.
• The rotation of the blades causes an internal low speed shaft to spin. This shaft is connected to a gear box which increases the number of rotations per minute. Initially it is ~ 18 revolutions per minute, but with the gear box in place, it increases it to ~ 1800 revolutions per minute.
• The low speed shaft and gear box connect the rotor to a generator, so that when the rotor spins, the generator spins as well.
•  The generator uses an electromagnetic field to convert the mechanical energy into electrical energy.
•  The rotor turns to face the wind to maximize the amount of energy it receives. Also, extremely high winds can cause damage to the turbine. To prevent this from happening, the turbine is equipped with a brake, to stop the blades and rotor from spinning.

           For a more visual understanding, check out the video below:

           How do wind turbines work?

Benefits of wind energy

1. Just like the sun, wind is always there and is produced consistently.

2. Wind energy is free and we do not have to pay for it. No fuel is needed to power it.

3. Wind energy poses no harm to the environment or health of society as it is free of pollutants.

4. Over the years, the cost to produce wind energy has been reduced.

5. This has provided employment opportunities as workers are needed for installation and maintenance. This benefits the economy in rural areas where some turbines are installed. In addition to this, power plant owners at times pay rent to farmers and ranchers for the use of their land providing an income for them.

Limitations of wind energy

1. The initial cost to implement wind turbines is very high. But we can assure you that within the years to come it will definitely be worth it!

2. Wind turbines occupy a huge amount of space and is considered to destroy the landscape. They are positioned high up in the air and can be a threat to wildlife nearby such as birds. They are also positioned deep within the earth which poses a threat to underground habitats.

3. Wind turbines create a lot of noise. For this reason, wind farms are located in remote areas where few are affected by this.

4. The turbines require a minimum wind speed for operation which turns the blades. If this speed is too low, the blades will not rotate and no electricity will be produced. This implies that they can be limited to areas where there are consistent winds, with speeds large enough for operation, such as hilly high topography areas and coastal regions. 

5. As mentioned before, there is a break to stop the rotor and blades from spinning during high winds to prevent damage to the turbine. However, during extremely high wind conditions, like hurricane season, the brake may fail and the turbines can become damaged.