Solar Insolation: will solar panels work in my country or location?

A question frequently asked about solar energy systems by prospective buyers is: Will solar panels work at my location?

A simple answer to that is: If you can see the sun at where you’re planning an installation, solar energy systems will work!

Solar activity is universal in nature

Solar activity of the sun and its irradiance which the earth receives is wide spread and universal in nature.

Irradiance is defined as a measure of the power per unit area of Earth’s surface produced by the sun and is expressed in kilowatts per square meter (or foot).

This is in form of electromagnetic radiation and is commonly referred to as sunlight.

Another important term used very commonly is insolation:

Insolation is the measure of the total solar irradiance that a particular area receives at any given time.

Although total energy output from the sun could be assumed to be constant, insolation varies from one place to another and changes from season to season.

A misconception about solar energy

One misconception about solar energy is that it will only work in sunny parts of the world like Africa or Mexico.

The truth is that since solar radiation is a universal phenomenon, a PV cell will work irrespective of the geographical location. Though it is true that some areas on the earth will receive more solar irradiance than others at any given time.

Sun’s rotation, its revolution, its angle of inclination upon earth and its orbital distance changes over the course of the year, making sure that no area on the earth receives the same solar irradiance all throughout the year.

India, for example, has a four month summer season when sun is directly overhead and experiences a huge amount of insolation. During the winter season when sunlight is inclined at an angle, it experiences a lower value of insolation.

The more sun the better for solar energy systems?

A high level of insulation definitely contributes to a high performing solar system.

However the regions on earth with highest insulation levels, countries at the equator, are not necessarily the very best places to install solar panel.

Heat can drastically decrease the performance of any solar system. Solar panels made with Si solar cells, any temperatures above 25 degrees C will cause a decrease in panel efficiency. Thin film solar panels are less sensitive to higher tempratures.

Will solar panels work in my country or location?

Coming back to the question asked above: Will solar panels work in my country or location?

It can be safely said that no matter what your geographic location may be, solar energy will work. However depending on insolation levels, which you can see on the world solar insolation zone map above, your solar energy system will perform better or worse compared to other locations in the world.

How many sunlight hours I get where I live?

As the electrical output of a solar energy system is directly proportional to the amount of sunlight solar panels are exposed to, it is extremely important to analyze beforehand the availability of sunlight in your area.

There are many factors which decide the availability of sunlight at any given geographical area.

The top four factors which dictate the availability of sunlight to be harnessed by solar cells are:

1. Location of solar panel and its angle of inclination.
2. Time of the year when the solar system is intended to be used (summer, winter, year-round)
3. Typical local weather conditions
4. Type of solar system used (fixed mounting, solar tracking system, etc.)

Optimal inclination or striking angle of sun’s rays

It should be noted that the generating capacity of a PV Panel is also depends upon the striking angle of the sun’s rays.

Maximum power can be generated when the sunrays strike the PV Panel at an angle of 90 degree (rays perpendicular to the PV Module’s surface).

When the angle is not in this optimum angle, a lot of energy is lost in reflection. A 90 degree angle ensures that most of the energy is absorbed by solar panels and very little is lost in reflection.

Sunshine recorders to determine the total sunshine in your area

Sunshine hour data is readily available over the internet for a lot of countries.

An empirical way of calculating the total sunshine is by using a device called a sunshine recorder or Campbell-Stokes recorder. These determine the number of hours on a day during which the sunshine is above a certain threshold (typical value is 200 mW/sq.cm).

Sample data can be collected for any number of days and then averaged over a week, month or year.

This method of calculating the solar radiation and sunshine hours is not the most accurate, however it’s inexpensive and provides a fair idea of the total sunshine hours, which can be used to determine the feasibility of using solar panels at your location.