Solar Energy

Sunshine comes close to being the ideal energy source, including widespread availability, an unlimited supply, and zero cost up to the point of collection. Using solar energy does not cause air, heat, or water pollution. Sunshine is intense and widely available in many parts of the world. 

There are several ways in which solar energy can be utilised. The simplest of these is for heating water. 

Solar water geysers rely on warm water rising, better known as convection. This is how water circulates through the panels. Convection happens when the water stored in the panels heats up and rises into the water tank above, or in the ceiling – depending on where you decide to install it. The hot water in the tank then moves into the cylinder, usually located inside the house.

Meanwhile, the cooler water in the tanks flows downwards into the absorber (collector). These actions create circulation.  

Figure 1: Solar water geysers use black tubes to absorb sunlight and heat the water flowing through them. 

Heating up of electric water geyser accounts for 40 – 60 % of the household’s electricity

Solar energy can also be used to generate electricity using photovoltaic panels.  Photovoltaics (PV), photo meaning light, and voltaic meaning to do with electricity, is rapidly growing with global capacity increasing from 230 GW at the end of 2015 to 890 GW in 2021.  PV systems range from small, residential, and commercial rooftop or building integrated installations, to large utility-scale photovoltaic power station. 

PV uses solar cells assembled into solar panels to convert sunlight into electricity. 

Figure 2: Solar panels on the roof of a house.

Solar cells are small devices which can convert sunlight into electricity. One cell on its own will only provide a small amount of power. Several cells connected and fixed in a frame make a solar panel (or a module), which can produce a larger, useful amount of power. When several panels are connected you have a solar array.

Inside a solar cell there are two wafer-thin layers of silicon crystal, placed on top of each other to make a silicon sandwich. The top layer has been specially treated so that its atoms are unstable because they have too many electrons that they would really like to get rid of. 

Figure 3:  The insides of a solar panel 

The bottom layer has also been treated, but the atoms have a few empty spaces that need an electron to fill them. So, the top layer is desperate to lose a few electrons, the bottom layer is desperate to gain a few electrons, and the electrons themselves are itching to move from the top layer to the bottom. 

Once the solar panel is exposed to light the electrons within silicon crystal can move around freely.

The inside of a solar cell. As photons of light hit the top layer, it allows electrons to flow from the top layer to the bottom, creating a current.

When sunlight hits the top silicon layer, it ‘excites’ the electrons and gives them enough energy to move. The electrons begin to flow from the top layer to the bottom. When lots of electrons start to move in the same direction, the generate an electric current. 

The electricity generated by PV solar cells is DC (direct current). The electricity used in homes is AC (alternating current). So, the current from the solar panel system must go through an inverter, to convert it from DC to AC before it can be pumped into homes and used to run appliances.

Installing solar panels is expensive but in recent years, PV technology has improved its electricity generating efficiency, installation costs have reduced, and it has become a more economical way to generate electricity. 

Figure 4: A solar farm in Jordan

China and India are expected to become the world's leaders in using solar energy by 2027.   Many solar photovoltaic power stations have been built, mainly in Europe, China and the United States.  The worlds 6 biggest farms are:

1.  Bhadla Solar Park (Rajasthan, India) — 2,245 MW
2. Huanghe Hydropower Golmud Solar Park (Golmud, Qinghai, China) — 2,200 MW
3. Pavagada Solar Park (Karnataka, India) — 2,050 MW
4. Benban Solar Park (Benban, Egypt) — 1,650 MW
5. Tengger Desert Solar Park (Zhongwei, Ningxia, China) — 1,547 MW
6. Noor Abu Dhabi (Sweihan, United Arab Emirates) — 1,177 MW

 Pros of Solar energy

1. Stable price levels compared to other energy sources: Many energies, especially those who rely on fossil fuels, are expensive since a price is usually determined by supply and demand.

2. Cost is zero after one-time investment: Solar energy is free. Apart from the upfront cost for the installation of the solar panels and the storage, energy can be produced with no extra cost.

3. Solar energy is a renewable energy source.

4. Solar power is available all year long and can be stored: Although solar power cannot be produced every day due to clouds or rainfall, the energy that is produced during sunny days can be stored.

5. Solar energy will become even cheaper in the future: Even though there has already been plenty of research in the field of sun energy, it is likely that technological progress will continue, and this will also lead to a decrease in prices for solar panels and batteries.

6. Low maintenance costs and efforts: Since solar panels are quite durable on average, the maintenance costs are quite low.

7. Solar power can be regarded as quite ecologically friendly: Apart from the initial production of solar panels and of solar energy storage, there is virtually no additional pollution associated with the generation of solar energy.

Cons of solar energy

1. Initial production of solar panels produces significant pollution: 

2. High upfront costs of solar panels:  The upfront costs of solar panels can be quite high as are the batteries needed to store energy.

3. Sun intensity varies over the year: Since there is not only good weather, depending on the region, there might be many days or even weeks with rain or clouds and your solar energy panels will not be able to generate enough electricity.

4. For solar farms, large areas of land must be used, which in turn often leads the destruction of habitats for a variety of animals and plants.