Sunlight - Solar Radiation

Sunlight Solar radiation is also known as sunlight or solar resource is a general term used for the electromagnetic radiation emitted by the sun. Solar radiation is captured by different sources and can be turned into several other forms of energy, such as heat, electricity, using a variety of technologies. However, the economical feasibility and operation of these technologies at any specific location depends mainly on the available solar resource and amount of sunlight rays received. 

The amount of sunlight wavelength depends on the extent of the daytime cloud cover. Some places on Earth surface can receive more than 4,000 hours per year of sunlight which is more than 90 percent of the maximum possible like in the Sahara while others receive less than 2,000 hours, in some regions like Scotland and Iceland which have frequent storminess. The amount of sunlight also changes regularly as the day progresses, owing to greater cloud cover in the early morning and during the late afternoon. In this topic, we have discussed what is sunlight and solar radiations, Let’s discuss more about its principle, uses, and advantages.

Basic Principles

Different location on Earth surface receives a different amount of sunlight every year. The amount of sunlight wavelength which reaches any place on the Earth's surface varies according to:

• Geographic location

• Time of day

• Season

• Local landscape

• Local weather.

Our Earth is round in shape and the sun strikes the surface of Earth at different angles, ranging from 0° (above the horizon) to 90° (directly overhead). When the sunlight is vertical, the Earth's surface gets the maximum possible energy. The more tilted the sun's rays are, the longer it will take to travel through the atmosphere and becoming more scattered and diffuse. 

As our Earth is round in shape, some regions never get a good amount of sunlight because of the tilted axis of rotation, these areas receive no sun at all during part of the year.

When the sun is near to Earth, the Earth's surface receives the maximum amount of solar energy. The Earth is nearer to the sun when there is summer season in the southern hemisphere and winter in the northern hemisphere. The small tilt of around 23.5° in the Earth's axis plays a major factor in determining the amount of sunlight striking the Earth at a particular location. 

Countries such as the United States, which lies in the middle latitudes, receive maximum solar energy in the summer not because days are longer, but because the sun is nearly overhead. The sun's rays are more slanted during the shorter days of the winter months. Cities including Denver, Colorado, (approx 40° latitude) receive nearly three times more solar energy in June compared to December.

The rotation of the Earth’s surface is responsible for hourly variations in sunlight. If we notice the phases of the sun in the early morning and late afternoon, the sun is low in the sky in the morning time. Sun rays travel further through the atmosphere at noontime when the sun is at its highest point. On any clear day, the amount of solar energy reaches a solar collector around solar noon.

Advantages of Solar Energy

• Clean: It is considered to be one of the cleanest forms of energy as there is no emission of carbon dioxide like in the case of fossil fuels which is one of the major causes of global warming.

• Renewable: It is a renewable source of energy and there is an ample amount of solar energy available on the earth.

• This energy can be stored in the batteries and so there is no question of unreliability.

• Reduction in overall costs.

• Free source energy because it can be trapped and used easily.

Disadvantages of Solar Energy

• The production becomes very low during winters and on cloudy days.

• Installation cost and the initial cost of the materials are too expensive.

• Space consumption is very large.

Types of Solar Energy

Solar energy can be classified into different categories depending on the mode of conversion and type of energy it is converted into. 

Passive Solar Energy: 

In this process, trapping of the sun’s energy can be done without using any mechanical devices.

Active Solar Energy: 

In this process, mechanical devices are used to collect, store and distribute the energy.

Solar Thermal Energy: 

This energy can be obtained by converting solar energy into heat.

Photovoltaic Solar Power: 

The energy can be obtained by converting solar energy into electricity.

Concentrating Solar Power: 

It is a type of solar thermal energy that can be used to generate solar power electricity.

Uses of Solar Energy

Water Heating: 

Solar energy is used as an alternative to replace electric heaters and gas as efficiency is more by 15-30%.

Heating of Swimming Pools: 

Solar blanket is used to keep the pool warm. The other way is by using a solar water heater to keep the water warm for a long time.

Cooking Purposes: 

Solar cookers are used in making food items. Solar energy is used to heat, cook and pasteurize food. A solar cooker consists of an elevated heat sink so that when food is placed in it, it gets cooked easily. Using solar energy for cooking is very simple. Instead of cooking in a conventional oven, cooking in a solar oven can surprise us with the electricity bill. To cook in a solar box we require – thermometer, a box with aluminium foil, pan duct tape, a cooking bag, and styrofoam insulation.

Solar Energy for Industries

Many industries have a huge demand for electricity due to the use of heavy machinery and equipment. The power supply can be made with the help of solar energy. It can be used in order to protect pipes from corrosion. Using solar energy can manage the electricity bills.

Solar-Powered Transportation: 

The transportation process done by photovoltaic (PV) electricity is an advanced method in making effective use of sunlight. Railways, subways, trains, aircraft, vehicles, etc can be driven by solar power.

Solar Lighting: 

Adding indoor solar lighting is one of the simplest methods to enhance house effectiveness. solar lighting does not require a very complex setup. As the lamps used are easily mobile and can harness the sunlight during the day. So there will be no need for grid-supplied electricity in the evening. 

Solar lights are not that much used as solar panels. As it is an inexpensive item that can decrease electrical charges and enhance the home’s effectiveness.

Solar space heaters can harness sunlight and can use liquid or air as a catalyst to transform it into thermal energy. Solar water heaters use water as a solvent in the thermal transfer method. The person who builds a solar thermal array on their ceiling can get a return of 5 to 10 percent with a scheme that charges a portion of a solar panel.

Solar Energy for Battery Charging: 

Batteries which is used to play video games can be charged during the daylight as a backup in case of a power cut. In order to save electricity, we can charge the reserve battery bank in the sunlight throughout the day and can be used in the nighttime.

Solar Water Heater: 

There are two types of solar water heaters that can replace traditional water heaters they are active solar hot water systems and Passive hot water systems.

Active water heater system can be classified into two categories:

• Direct Circulation System 

This system includes a pump to circulate household water into the house with the help of solar collectors.

• Indirect Circulation 

This process includes non-freezing liquid to transfer water that flows into the home. They are used in areas where there are freezing temperatures.

Passive Water Heater System 

They are cheap and less efficient compared to active water heater systems.

Conclusion

As solar energy is environment-friendly it is best suited for countries like India. It does not release carbon dioxide gas. It is a good replacement for non-renewable sources of energy as it is an inexhaustible source of energy. Rural areas can be largely benefited from this energy for various purposes including cooking, drying, electricity, etc. In countries like India and Bangladesh, the generation of power is costly so solar energy is the best alternative.