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This article will describe how solar energy is created and cover some of its basic principles.

Solar energy is created by light and heat which is emitted by the sun, in the form of electromagnetic radiation.

With today’s technology, we are able to capture this radiation and turn it into usable forms of solar energy – such as heating or electricity.

Although one could go into technical dissertations on the subject of electromagnetic radiation, how it is converted into solar energy, and the exact qualities of its electromagnetic rays, this is not something the average person needs or wants to know.

But in order to be able to benefit from the use of solar energy, there are a few facts you should know. Knowing these facts can assist you to make a sound decisions, when looking at the use of solar power as a clean energy source for your home, RV, or whatever the case may be.

Available Solar Resource

The technical feasibility and economical viability of using solar energy depends on the amount of available sunlight (solar radiation) in the area where you intend to place solar heaters or solar panels.

This is sometimes referred to as the available solar resource.

Every part of Earth is provided with sunlight during at least one part of the year. (I say “part of the year” as the north and south polar caps are each in total darkness for a few months of the year.) The amount of sunlight available is one factor to take into account when considering using solar energy.

There are a few other factors, however, which need to be looked at when determining the viability of solar energy in any given location. These are as follows:

Geographic location Time of day Season Local landscape Local weather

Because the Earth is round, the sun hits its surface at different angles, at different locations on the globe. This ranges from 0º (just above the horizon – a good example of this is the north pole during the winter) to 90º (directly overhead, at and near the equator).

When the sun’s rays are vertical (directly overhead), the Earth’s surface gets a maximum of solar energy. The more slanted the sun’s rays are, the longer they have to travel through Earth’s atmosphere before reaching the surface (becoming more scattered and diffuse as they go along).

The more scattered and diffuse the sun rays are, the less concentrated the solar energy is. Because of the fact that the Earth is round, the polar regions never get direct sunlight, and, during their respective winter months, they receive no sun at all.

The Earth travels around the sun, in an elliptical orbit. Because of its elliptical path, the northern hemisphere of the Earth is closer to the sun during one half of the year, and the southern hemisphere is closer during the other half of the year.

When one part of the Earth is closer to the sun, it receives more concentrated solar energy. This is the time of year that is referred to as “summer.”

But regardless of summer or winter, the 23.5º tilt of the Earth’s axis plays a larger role in determining the amount of sunlight striking Earth at a particular location. The Earth’s tilting results in longer days in the northern hemisphere during one half the year, and longer days in the southern hemisphere during the other half of the year.

Areas such as the United States and Europe receive more solar energy between May and September – not only because days are longer, but also because the sun is almost directly overhead during this season. The sun’s rays are far more slanted during the shorter days of the winter months. Cities such as Denver, Colorado, receive nearly three times more solar energy in June than they do in December.

Diffuse and Direct Sunlight

As sunlight passes through Earth’s atmosphere, some of it is absorbed, scattered, and reflected.

The following is a general list of materials which cause the sunlight to become diffused:

Air Molecules Water vapor Clouds Dust Pollutants

Sunlight affected in this way is referred to as diffuse solar radiation or diffuse sunlight.

Sunlight that reaches the Earth’s surface without being diffused is called direct beam solar radiation or direct sunlight.

The sum total of all diffuse and direct solar radiation in a given location is called global solar radiation. It is the total amount of sunlight hitting the Earth at any specific spot, both direct and diffuse combined.

Pollution and other atmospheric conditions (such as weather patterns) can reduce direct sunlight by 10% on clear dry days. They can reduce direct beam radiation by 100% on thick, cloudy days.

Note that the absence of direct sunlight does not imply total darkness, as some diffuse light will still get through.

Measuring Sunlight and Solar Energy



Scientists measure the amount of sunlight available in specific locations during the different times of year.

They are then able to estimate the amount of sunlight which falls on similar regions at the same latitude with similar climates and conditions.

Measurements of solar energy are normally expressed as “total radiation on a horizontal surface”, or as “total amount of radiation on a surface tracking the sun”.

In this last case, the assumption is that one is using a solar panel that automatically tracks the sun.

In other words, the solar panel would be mounted on a tracking device so that the panel would remain at right angles to the sun throughout the day.

This system is primarily used for industrial setups, when it is used at all.

Solar Energy Measurements

Radiation data (the amount of solar energy available at a given location) for solar electric (photovoltaic) systems is often represented as kilowatt-hours per square meter (kWh/m2). Direct estimates of solar energy may be expressed as “watts per square meter” (W/m2).

Radiation data for solar water heating and space heating systems is usually represented in British thermal units per square foot (Btu/ft2).



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Every day, households around the world are using up the planet’s resources for energy. If this continues, these energy sources will be depleted quickly -unless alternative renewable energy sources are utilized.

One of the energy sources that modern technology has recently put to good use is solar energy. Solar energy isn’t anything new, but new technology advancements have placed solar power more into the mainstream, and it may one day be one of our primary sources of power.

Advantages of Solar Energy

Since solar energy comes directly from the sun, it is not only renewable, but also accessible in any part of the world. As long as the proper equipment is utilized, unlimited amounts of solar power can be collected and put to good use.

Solar power is also one of the cleanest forms of energy, since it creates no pollution, and produces no greenhouse gases or waste products. For residential uses, the use of solar power minimizes negative impacts on the surrounding environment, making it a safer alternative to wind or hydro power.

Not only is solar energy non-pollutant, in terms of gases, but it also causes zero noise pollution – since there are no moving parts in any of the devices which are used to capture the sunlight. Due to the fact that no moving parts are used, maintenance costs are low as well – only occasional cleaning and periodic battery replacements are needed. Most manufacturers of solar panels provide twenty-year warranties for their equipment, guaranteeing long-life operation.

Solar panels placed on rooftops also double as a heat absorbers, slightly cooling the top area of the house which is directly below the roof.

Disadvantages of Solar Energy

The most obvious drawback of solar energy is its sole dependence on the sun. Once the weather becomes cloudy, or night strikes, energy collection comes to a halt. However, recent advancements of technology now allow the generated power to be stored in special batteries which provide roughly enough electricity to last a night.

This is why solar-powered devices, including flashlights, are gaining in popularity and are proving to be efficient energy savers. Solar panels can also be expensive, because of the materials that are used to create them. And even when these materials are taken out of the equation, the entire process, considering the other devices involved, can be a bit costly. This includes portable devices that utilize solar energy. But most of the cost involved is in the initial purchase and installation of a solar power system – not running costs.

Fortunately, there are some people who sell damaged solar cells, which are much cheaper. These damaged solar cells can be used to build fully functional solar panels, using the application of simple do-it-yourself techniques. Although in every part of the world, there is at least some point in time when the sun shines, it is also true that direct sunlight is needed in order to make the most of the sun’s energy – and to generate the highest amounts of power. This significantly restricts the placement of solar panels. And some areas in the world may receive little benefit, due to lesser sunlight.

What’s the Bottom Line?

More research and development continues to be invested into this growing technology, and that’s a good sign for the future of our households – as solar power may one day be used more frequently than other energy sources. Of course, solar energy isn’t perfect, but it makes a great complimentary addition to other energy forms.

Throughout man’s history the sun has always been a subject of speculation and worship. In fact, most ancient cultures have deified the sun, due to its life-giving and energy-giving qualities.

Thus, the subject of solar energy is one of the oldest subjects on Earth. It has gone through many evolutions and has been the subject of many schools of thought – starting with religion, and ending up in the field of science.

In fact, though not many people know this, a large portion of the western civilization celebrates the returning of the sun each year, just as the ancients did thousands of years ago.

I am, of course, referring to Christmas – which dates back to the celebrating of the winter solstice, the point in time when the Earth has reached its furthest point away from the sun, and starts returning.

Of course, the story of Christmas has radically changed from its original meaning. It has gone through its own evolution. Originally being a celebration of the sun’s return, it then became the celebration of the birth of Christ, and eventually wound up with a friendly old man bringing Coca Cola on Christmas Eve. But this last point is simply modern marketing at work.

The First Uses of Solar Energy

It is almost impossible to exactly date the first uses of solar energy.

But we do know that the ancient Greek and Roman civilizations, among others, made use of “passive solar energy” in their building designs.

Passive solar energy is the use of a building’s architecture to capture the sun’s heat and light.

In 200 B.C., the Greek scientist, Archimedes, used concentrated solar power technology, (now referred to as “CSP”) by combining the reflective properties of many polished bronze shields, in order to focus sunlight and thus set fire to an invading Roman fleet while it was besieging Syracuse.

(In 1973, The Greek Navy recreated this scenario as an experiment, and succeeded in setting fire to a wooden boat 50 meters away.)

Socrates and the Romans

Even the famous Greek philosopher Socrates has commented on the benefits of facing one’s house toward the south, in order to make use of the heat provided by the sun in the winter.

The Romans also used this technique, of facing their houses southward, but they took it a step further. They also installed more windows on the south side, allowing the heat and light of the sun to freely enter the buildings.

Throughout the first four centuries after Christ, Roman bath houses employed passive solar heating. The Romans built the bath houses with large, south-facing windows, to let the sun’s warmth in. This aspect of passive solar technology is still used by architects today.

With these methods, they were able to reduce the amount of fuel they needed to heat their buildings. And considering that you had to go out and chop your own wood in those days, it was well worth it.