HomeSolar EnergySolar Energy | The Full Guide

Solar Energy | The Full Guide


Solar energy has been gaining wide acceptance in recent years. Now there are solar energy farms where thousands of solar panels are installed to harness the sun’s energy. These massive electricity-generating units generate so much energy that they can meet the energy demands of a large city. Sun is the most powerful source of energy on earth.

Its full potential is yet to be realized. Earlier solar systems and processes used to harness solar energy were not very efficient. However, in recent years there have been many breakthrough technologies that have increased the efficiency ratings of solar power harnessing systems. No life is possible on earth without the energy from the sun. Solar energy is clean, green, and renewable.

What Is Solar Energy?

What Is Solar Energy?

The energy produced by the sun is called solar energy. It includes both light and heat energy coming from the sun. It is radiant electromagnetic energy in the waveform so it can travel through space. That is how it is possible for the radiant heat and light of the sun to reach the earth.

A variety of techniques, systems, and solutions have been developed over the years to convert solar heat and light into usable forms of energy. A solar panel is the most prominent example of such a system but there are a few other systems that have been used to harness the sun’s power.

About 173,000 terawatts of the sun’s energy hit the earth continuously. On average, approximately 1.4kW per hour per square meter of solar energy is received at the top of the earth’s atmosphere. About 1000 watts or one kilowatt of this energy is received per hour per square meter on the earth’s surface.

There are several factors that affect how much solar energy is received every day in a particular location on the earth. Some of these factors include the distance of the earth from the sun at a given moment, the time of the day, the time of the year, atmospheric conditions, and the location on this planet.

Forms of Solar Energy

There are two types of solar energy – active and passive.

Forms of Solar Energy

Active Solar Energy

All systems that use some type of mechanical or electrical equipment to collect, store and distribute solar energy are placed under this category. These systems convert the sun’s heat and light into usable forms of electricity, heat, or light.

In this type of setup, the energy of the sun is not used directly. Solar panels made of photovoltaic (PV) cells are the most prominent example of active solar energy. Another example is a thermal solar system that heats and circulates liquid, air, or antifreeze substances to heat water.

Passive Solar Energy

When sun heat is captured and stored without using any mechanical or electronic device, then it is referred as passive solar energy. A car left under the sun with all its windows and doors closed is a good example to understand this form of solar energy.

The sun’s heat causes the air inside the car to heat up. The heat inside the car is unable to escape while the heating process continues. It causes the internal temperature to rise more than the outside temperature.

The same effect is used to keep homes warm during cold weather. The room’s windows with glass panels are kept closed. If the sun is shining, the sun rays enter the room through the windows and warm the internal atmosphere. Sun energy is harnessed by simply designing a building’s walls, floors, roofs, and windows in certain ways.

It is possible to keep the rooms warm even when the outside temperature is lower. The only condition is that some amount of solar heat should be available. Before the advent of mechanical and electrical devices, this was the way sun energy was harnessed to keep homes and buildings warm. It is still used extensively because it costs nothing except for the initial costs of designing and building the house.

The efficiency of this technique can be increased by insulating the walls, floors, roofs, windows, and doors. It eliminates the need to install energy-intensive space heating devices. A building is ready to harness the sun’s energy once it has been designed and constructed properly.

Solar Thermal Energy

It is a part of active solar energy. This type of system uses heat from the sun to heat something or produce electricity. The setup with evacuated tubes is the most widely used thermal solar setup. Its efficiency rating is very high at 70%. There is excellent insulation so it does not get affected by the surrounding air temperature.

Its collector that harnesses the sun’s heat is made up of several insulated glass tubes containing copper pipes. The water is heated in the collector and then sent to the water tank through the pipes. This system is highly efficient but also the most expensive. Another type of solar thermal power system uses a flat dark plate to absorb the sun’s heat. This captured heat is used to heat a liquid containing an antifreeze substance. This heated liquid in turn is circulated through the pipes in the water tank.

It is used mainly to heat water. Small thermal energy units are used in homes and hotels to heat water. Large thermal energy setups are used in the manufacturing industries to heat the water of the boiler and other systems.

Solar energy has been harnessed since ancient times. The magnifying glass was used in the 7th century B.C. to concentrate sunlight and make fire. The solar system with photovoltaic effect was first developed in 1839 by Edmond Becquerel who was a French scientist. The first practical PV cells using silicon semiconductors were developed in 1954 in the Bell Labs by Calvin Fuller, Daryl Chapin, and Gerald Pearson.

It had sufficient energy conversion efficiency. Since then there have been many technological advancements that have increased the efficiency of PV cells.

Photovoltaic Solar Power System

Photovoltaic Solar Power System

This type of solar power system is now used widely to generate electricity. Its advantage is that electricity can be generated anywhere where the sunlight reaches. It works best in places where sunlight is available for most parts of the year or all year round. The main parts of this setup include a solar panel and an inverter.

Photovoltaic cells of the solar panel convert sunlight into electricity. At this stage, it is DC electricity and not rectified so an inverter is used for energy inversion and conditioning. Now the rectified electricity can be used to power common electrical appliances. Most consumer electrical items used in homes and other places use AC electricity. To power such systems with the solar panel’s electricity, an inverter is used to convert the solar panel’s DC power into AC power.

A PV solar power setup can be used to charge a battery. It helps store solar energy for later use. The energy of the charged battery is used to power electrical items. A solar panel power setup with a battery makes it possible to use solar energy any time of the day or night. Some people use the term solar panel only for non-PV solar panels used to heat water. The ones with photovoltaic cells are referred to as photovoltaic panels.

What Is a Photovoltaic Cell?

A photovoltaic cell has a semiconductor material like silicon that creates an electric charge when exposed to sunlight. The word photovoltaic comes from the photons of light and voltage of the electricity. The semiconductor material is capable of converting light energy into electricity without any moving parts.

Earlier photovoltaic panels were not very efficient so their use was limited to special purposes like powering space satellites and remote research stations. Since then there have been great technological advancements in this field. Now photovoltaic cells are very efficient in converting sunlight into electricity. Researchers continue to increase this conversion efficiency.

Solar Panel with Photovoltaic Cells

A single photovoltaic cell can generate about 1-2 watts of power. To boost this power output, multiple photovoltaic cells are connected to each other and mounted on a support base. This set of photovoltaic cells is called a photovoltaic module. A module can be used in itself if only a small amount of power is needed.

To further boost the power output, several such modules are connected together and placed on a support base. It is called a photovoltaic solar panel or PV panel. The number of modules on one panel depends on the amount of voltage required from that panel. Several solar panels are connected together to obtain the desired amount of solar energy.

Any number of solar panels can be connected together to generate electricity. It is limited only by the available space and budget. PV cells are available in several sizes and shapes. A PV cell has a thickness that is less than human hair. This structure is vulnerable to breakage if used in the real world without any further protection.

The cells are placed between two protective materials made of glass or plastic for better protection during handling, transportation, and installation. Most people see photovoltaic solar panels in this form on the rooftops of homes and buildings. These panels are connected to the power system that first rectifies the incoming solar electricity and then distributes it to the connected electrical items.

Sunlight Requirements for PV Panels

A PV system is powered by the sun’s rays so it must be placed at a location where sunlight is available in abundance. Most PV solar panels can generate electricity even during cloudy days but the performance and electricity output are not very high in such conditions.

For best results, the PV cells should get a significant amount and intensity of the sun’s rays. The performance of a PV solar panel is not affected by the climate conditions like air temperature. Areas that receive lots of sunlight are ideal places for solar power system installations.

Solar Panel Maintenance

Solar Panel Maintenance

Made with tempered glass, solar panels are durable and made to withstand rough weather and harsh outdoor conditions. There is no moving part except in cases where a tracking mount is installed. If everything has been installed correctly, the solar panels do not require regular maintenance. The panels keep performing well over their specified lifetime.

The energy conversion efficiency of a PV panel can come down slightly in areas that see a lot of dirt, dust, and smog. Owners using solar panels in such areas should keep a watch on their solar power system’s performance. If it dips below the specified level, some cleaning of the solar panel’s top surface may be needed.

It is important to remember that going on a rooftop to clean solar panels is risky and dangerous. It is better to take the help of a professional solar panel cleaner for this job. They are trained to handle such jobs and use proper equipment and safety gear.

The Cost of PV Solar Panel Installation

The Cost of PV Solar Panel Installation

It depends on several factors. The first is the amount of electricity needed from the solar power system. The second is the type of solar panel purchased. There are different qualities of solar panels. The ones that are more efficient in converting sunlight into electricity are more expensive.

There are some additional charges associated with the installation of a solar power system. The services of professional installers are needed to install the PV solar panels on the rooftops. The installation team includes electricians who install the electrical parts of the setup and connect them to the home electricity connection.

There may be additional expenses. For example, a rooftop may require some modification before solar panels can be installed on it. The solar panel system usually comes with all parts needed for its installation on the rooftop but some other items like sealing materials, nails, nuts and bolts, and cable covers may be needed. All such items must be purchased separately.

Homeowners and business owners can reduce the cost of solar panel installation by taking the help of incentives provided by the federal and state governments. Installation of a solar panel generally costs about $15,000-$30,000 on average. This cost is calculated before any rebate or tax credit. At the lowest end, it costs about $5,000 and at the high end, it can cost about $40,000 for a home.

Solar Tax Credit

Solar Tax Credit

This incentive is available to both residential and commercial groups. The costs of solar panels are already coming down. With the help of solar tax credit, the investment needed to install the solar panels comes down substantially. The federal tax credit for this purpose allows a 30% deduction from federal taxes. There is no cap on the value.

This credit is available to the owner of the solar power setup. It is not available to people who install a solar power system under a lease or power purchase agreement. To avail of this tax credit, it is not necessary that the house is the principal residence of the taxpayer.


Solar energy is now used extensively all over the world. The following are the most prominent applications of solar energy.


Water Heating

In some regions, hot water is used a lot during the winter months. Solar water heating systems are a good solution for these areas. A lot of energy is needed to heat the water. This energy expense can be saved by using a solar water heater. Non-PV solar panels specially designed to heat the water are preferred for this type of setup due to their higher energy efficiency. Solar water heating units are installed for residential, commercial, and industrial applications. In some industries, boilers are run with the help of large solar water heaters. It helps save a substantial amount of energy every year.

Space Heating

Solar energy can be used in two ways for space heating. The first is the active system where PV solar panels are used to generate electricity. This electricity can be used to power space heating appliances. In the passive solar heating system, it is the design and construction of the building that matters most. The building is designed in such a way that it retains the heat inside the room, causing the indoor temperature to rise more than the temperature outside the house.

Solar Heat Pumps

These devices turn the indoor temperature hot or cold with the help of electricity. If the electricity needed for this purpose is sourced from a solar power system, the costs of cooling and heating come down substantially. Homeowners can connect their solar electricity generating set up to the local utility electricity grid.

They earn credits that can be used to reduce their electricity bills. The heat pumps are useful in supplemental heating and help bring the indoor temperature to a comfortable level. Most of the heating can be done with the solar-powered heat pump while oil or propane equipment can be used for the backup. Solar energy-powered heat pumps are an economical solution to warm or cool the indoor areas of a building.


Solar power can be used to run standalone cooling appliances. Using a heat pump to cool the interior areas is the least expensive way. While a room air conditioner can be run solely by solar power, the setup will require a very powerful solar power system. A more economical and efficient solution is to use a heat pump to cool the rooms.

Now there are fewer power-consuming DC air conditioners that run directly from solar electricity. These systems need a very low amount of power to cool the interior. The devices are designed specifically to be run with the help of solar power. The initial cost of such an AC setup is low because there is no need to buy an inverter and a large battery.

Cooking with the Solar Energy

Foods and other items can be cooked with the help of solar energy. There are 2-3 ways used for this purpose. A solar cooker that directly heats the pot containing the food ingredients is an efficient solar cooking device. In this type of setup, sunlight is collected by an umbrella-type reflector and directed at the bottom of the cooking pot.

This helps cook the food inside the pot. Another type of system uses a similar technique as used in the rooftop solar water heater. It is a box that retains the radiant heat of the sun. The increasing temperature inside the box heats up the pot and cooks the food ingredients.

Another option is to use the electricity obtained from a PV solar panel to power a common heating appliance like an oven or a heater. It is less efficient than other solar food cooking systems but allows the use of popular cooking appliances. In some places, companies and organizations involved in cooking large amounts of food daily use heated water to cook the foods.

They use curved reflectors to direct sunlight onto pipes containing the water. The water is heated to a very high temperature. The heated water is used to heat cooking pots. The pipes and reflector are placed outdoors while the remaining parts of the system are placed in the indoor area where the food is cooked. Small units of enclosed box ovens, black box ovens, and parabolic reflector ovens are available for cooking foods using solar energy. These units can be used by individuals to cook foods for their own personal use.

Water Treatment

Solar energy is used in many areas to disinfect and purify water. The solar disinfection system helps remove bacteria, viruses, and protozoa in water. These devices are easy to use and can be installed anywhere. The cost of water treated this way is lower than the cost of branded bottled water.

There is minimal change in the taste of water. There are three different systems for this purpose. The first uses the power generated by solar PV cells. The second type of device uses heat from a solar thermal system. The third one utilizes the ultraviolet light of the sun’s rays to disinfect the water.

Solar electricity can also be used to operate a home water purification unit. Solar-powered small, medium and large reverse osmosis water treatment plants are operational around the world. All these systems can be used to obtain safe and pure drinking water even from seawater, brackish water, and surface water.

Solar Powered Lights

There are two types of solar lighting systems in use. In the first type of setup, the battery of the solar power system is stored indoors while the lights are installed indoors or outdoors. In the second type of setup, an all-inclusive solar light system is used. It is designed for outdoor use only and its installation is restricted to places that receive sunlight.

This type of unit has everything needed to power its light bulbs at night. It has a small PV module, a small battery, LEDs, and some electronic parts. It does not require any intervention and works automatically. It has a light-sensitive sensor that activates the light automatically when it gets dark. A similar setup is used for solar streetlights.

Such a system has larger units of a PV solar panel, a battery, a charging system, an electronic kit, and an LED module. It is an automatic system with a manual override option. Solar streetlights are now used extensively around the world to illuminate streets, roads, roundabouts, footpaths, and outdoor areas

Solar Chargers

Solar power chargers are used to charge batteries of different types, sizes, shapes, and specifications. It is simply a PV solar panel connected to a charging system. The charging system includes the electricity conversion system, wires, and electronics. The sunlight is converted into electricity by the PV panel. This power is used to charge the connected battery. It is important to buy a solar charger according to the type of battery that requires charging.

Solar Power Satellites

Space satellites have been powered with the help of solar energy for several decades. Now all satellites have solar panels to power their systems. It helps reduce their weight because they do not need fuel and an engine to power them. These satellites are used for communication, photography, and other purposes.

Solar Cars

Solar Cars

Over the years, researchers and renewable energy enthusiasts have tried various techniques to power a car using only solar power. In some solar cars, only some functions of the car are powered with solar power. There have been many experimental lightweight solar cars that run completely on solar power.

The amount of power that a car generally needs cannot be fulfilled with the power obtained from solar panels. The surface area of a car limits the number of solar modules that can be installed or attached to its top surface. It is only by increasing the conversion efficiency that a truly solar-powered car will be possible in the future.

There are some smaller vehicles with a bare-bone structure that have been run successfully with solar power only. In some vehicles, a hybrid system that uses solar power along with another energy source has been more successful.

Solar planes

Recently a completely solar-powered plane Solar Impulse 2 completed a world flight. Its batteries were charged by the solar panels installed on the plane. It was able to climb up to 29,000 feet during the daytime. It flew at the speed of 30mph. This plane had the pilots flying it. Researchers have been able to fly drones solely using solar power.

These planes are capable of flying perpetually. The planes have batteries that are charged during the daytime. The solar panels on top of the plane power both the battery and the engine. A solar plane that can fly passengers is currently not anywhere in use but researchers are always trying to achieve this goal.

The Position of Solar Energy among Main Sources of Renewable Energy

Hydropower is the number one renewable energy source. It forms 65% of all renewable power sources. This type of power can be generated only at certain locations where a large amount of water is available. Dams constructed on the rivers are used to drive turbines and generate electricity.

Wind power is the second most widely used source of renewable energy. Solar power is the third biggest source of renewable power. Biopower that uses biofuels like agricultural byproducts and wood pellets is the fourth largest renewable power source.

Geothermal power is in the fifth position in this group. It is used for both electricity generation and direct heating of water.

Impact of Solar Energy on Individuals and the Environment

Individuals and the Environment

Humans have been burning fossil fuels for a long. It has led to massive amounts of air and land pollution. Solar power does not emit any greenhouse gas so it is considered a greener energy solution. A large amount of water is currently used in electricity production. This water can be used better for residential, commercial, and industrial applications.

It can be made possible if more and more people start using solar energy. Solar power has made it possible to provide communication, TV, Internet, and other facilities in remote locations. People living in remote areas away from the grid electricity have been able to harness the sun’s energy and use it to their advantage. They use this energy to power different types of appliances and equipment.

It allows them to lead a comfortable life even when they are away from the large cities. Solar energy offers lots of savings. Its users save money that they have to pay to their utility electricity companies. Many homeowners use power purchase agreements with their utility power companies. They give away excess electricity from their solar power system to the power company when they do not need that much power. It helps them earn credits that are redeemed to reduce their electricity bills.

Solar energy helps save the environment. It is a clean and renewable energy that will remain available for the next five billion years. It has helped lower the carbon footprint of many companies and individuals. It makes sense to go solar. This energy can help slow and even stop global warming which is a threat to human survival on earth.

A small amount of solar energy received in a small location in a day is sufficient to provide electricity to millions of people throughout the year. There is no noise problem with a solar power setup, which is not the case with wind energy. There is little maintenance required to maintain the solar panels.

With the increasing efficiency of solar panels, more and more people are going to install solar power systems in their homes, business places, and industrial properties. Researchers are always working to increase the efficiency of solar power harnessing systems. Manufacturers have been able to lower the costs of solar panels. It has increased demand for solar power systems around the world.


Earthava Team
Earthava Team
A collective of experts in Renewable Energy, environment and green living.

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