What is your solar panel requirement?

Solar power calculation might sound so hard but actually it is simple. First and foremost, each system has different solar panel requirement. Of course, the requirement depends on how big your load is. Solar panels are clean source of energy which help the environment. In solar power calculation is it important to know the solar peak hours in your area. The solar peak hours or the average solar radiation is the particular hours the sun is shining in certain location. Furthermore, the number of average solar radiation is dependent on the average daily solar insolation.

In the solar power calculation the battery is also a critical part of solution since there are different kinds of a battery. Each battery comes with different characteristics that should be studied upon. Moreover, your solar panel requirement depends on your usage. It is also important to note, that every appliance has different power consumption Thus,  your solar panel computation should be accurate to make sure there is no shortage of energy.

Solar Panels and Solar energy

Solar Panels mimics plants ability to convert solar energy into useful energy. Furthermore, the world captures around 173 x1015 watts or 173 tera watts of solar energy. Solar panels generate energy through sunlight. Moreover, this technology converts sun’s energy into electricity. In fact, it is composed of solar cells which is made of silicon. In addition, with the photons that hit the solar panel causes the electrons  to move. Indeed, there many times of solar panels which are crystalline silicon, monocrystalline silicon solar cells, polycrystalline silicon solar cells and thin-film solar cells.

Solar Power History

Early days

In 1860,  solar technologies started it was driven by a foresight that coal would soon become scarce. Twenty-four years later, Charles Fritts installed the world’s first rooftop photovoltaic solar panel, it was made of 1%-efficient selenium cells, on a New York City roof . Sadly, due to increasing supplies of coal and petroleum the development of solar power technologies was static in the early 20th century . In 1974, the number of houses power entirely by functional solar power systems are estimated only about six homes.

Mid-1990s to early 2010s

Due to supply issues of oil and natural gases, growth of solar panels accelerated once again raising demands in residential and commercial rooftop solar as well as utility-scale photovoltaic power stations. Morevoer, the improving economic position of PV relative to other energy technologies also drive the sales of solar panels in the market. Moreover, with positive lobbying of policies in Europe which such as adoption of feed-in-tariffs that empowers renewables to be priority in the grid and fixed price for generated electricity. Indeed, with all of these policies it lead to a high level of investment confidence for investors and large market leaders thus increased the number of solar PV installation in Europe.

Current status

For many years, worldwide growth of solar photovoltaic was lead by European deployment. On the other hand, the growth has shifted to Asia, especially China and Japan. Next, there are growing number of countries and regions all over the world that promotes solar power. and also, these countries are one of the leading solar power generators: Australia, Canada, Chile, India, Israel, Mexico, South Africa, South Korea, Thailand, and the United States.

Furthermore, the world’s largest manufacturers are located in China making them one of the cheapest source of solar PV. Moveover, since 2000 the the worldwide growth of solar PV averaged 40%.  Last 2013, the total installed capacity reached 139 GW.  Presently, the leaders of solar power generation is Germany having the most cumulative installations (35.7 GW). Finally, Italy has the highest percentage of electricity generated by solar PV (7.0%).

You might find these terms useful:

1. Solar constant

 First, it is the amount f solar energy received per unit of time on a unit area of surface perpendicular to the radiation. Moreover, the outer limit of the atmosphere when the earth is at its mean distance from the sun.

2. Direct radiation

Furthermore, the solar radiation received by the earth’s surface without having been deflected/ intercepted. However, it can also be absorbed by the atmosphere.

3. Diffuse radiation

Next, the solar radiation that is first intercepted or absorbed by the atmosphere.

4. Pyranometer

Furthermore, this instrument is for measuring total solar radiation.

5. Pyrheliometer

Moreover, this instrument is for measuring direct solar radiation

6. Solar collector

Next, this device collects solar radiant energy and transform it into some useful forms. Of course, collectors can be flat plate or focusing type.

7. Photovoltaic cell

Finally, this device converts solar radiation directly into electricity. Moreover, the most common type is single crystal silicon solar cell.


Step 1. Load Calculation

First and foremost, calculate the daily energy demand. Identify each load, its wattage and the hours per day each appliance operates. Of course, make this is correctly solve in order know your solar panel requirement.

                                                     Total daily Energy Demand 

Load Wattage No. of Hr used Quantity Energy Consumption
DVD 30 4 1 120
TV 55 4 1 220
CFL 15 8 5 600
  Total Daily Energy Demand 940 Wh/day

Step 2. Calculate the size of the PV Array (Wp)

PV array size  = Total daily Energy Demand/(Peak Sun Hours x Eff.)

Ex.  Use Daily energy demand in step 1 and assume 90% efficiency. For example the peak sun hours is 5 hours

PV Array Size = 940/(5 x 0.9)  = 208.89 Wp

Step 3. Determine the number of PV module

Npv = PV Array Size/PV Capacity

Ex.  How many 53 Wp PV module is needed?

Npv53 = 208.89/53  = 3.94 ; use 4 modules to prevent power shortage


Step 1. Calculate Safe Battery Size (Ampere-hour)

Bat. Size = (Total daily Energy Demand x Autonomy day)/(eff. X Depth of  Discharge x System Voltage)

Ex.  Next, if allowable depth of discharge is 70% and 12 V system voltage. Then, assume 3 days autonomy in this problem. What is the size of the battery bank needed?

Battery size =  (940 x 3)/(0.9 x 0.7 x 12)  =  373.01 Ah

Step 2.  Determine the number of battery to be used

Nbattery = Battery size / battery rating

Ex. How many 100 Ah battery is needed for the system

Nbattery 100Ah = 373.01/100 = 3.73  Use four (4) batteries to prevent power shortage or battery overuse.

How to compute number of battery if the system voltage is not the same with nominal voltage?

Nbat Total = NB series X  NB parallel

Ex. How many 100 Ah battery is needed if the system voltage is 24V

NB series = system voltage/nominal voltage = 24/12 = 2

NB parallel = Bat size / battery rating

Bat. Size = (Total daily Energy Demand x Autonomy day)/(eff. X

Depth of   Discharge x System Voltage)

= (940 x 3)/(0.9 x 0.7 x 24) = 186.50

NB parallel = 186.50/100 = 1.86 use 2

NB total = 2 x 2 = 4 batteries

PV ARRAY/MODULE SIZING: Aquaphonics Example (Another Practical Way of Solving it) 

A water pump with 1.9 meter pressure head enough to bring the water to the top part of the aqua phonics system.  Next,water pump will run for 24 hours to maintain good water quality and dissolved oxygen for the system.  For this reason, the assigned agricultural engineer will use a timer in order to cut down the running time of the system by 50 percent. Therefore, the system will run for 30 minutes interval to minimize electrical cost. What is the required solar panel wattage? What is the required size of battery? Since, power required for the pump to run for one hour is 18 watts. What is the total solar panel requirement?

What is the power Requirement for 24 hours operation?

Correction factor (energy lost in the system)

What wattage of the Solar Panels?

Solar Panels are divided the number of hours of solar illumination.

Therefore, the solar panel requirement is 70 watts.

What is battery needed for the solar panel?

Next, battery capacity is measured in Amp Hours (e.g. 20AH). You need to convert this to Watt Hours by multiplying the AH figure by the battery voltage (e.g. 12V).

Use 24AH battery to operate the water pump.

Do I really able to take all the power from the battery?

Lead acid battery’s will give you around 50% of their rated power. Li-ion battery’s will give you around 80% of their rated power.

Lead acid Computation: 24 AH x 1.5 =36 AH

Lion Battery Computation: 24 AH x 1.2 =28.8 AH

Solar Power Calculation made easy

Finally, to know your solar panel requirement is a great advantage for your household needs and even to your business. I provided two examples in which it solve differently. Of course, there are different ways in solar power calculation. Moreover, you could use these examples depending on the situation. I hope this solar panel computational guide will help. Solar panels are the fuels of the future. Indeed, this technology will soon power most of our appliances, cars and more. Do you want to cut your bill? Contact your nearest agricultural engineer now. No doubt, you want to have premium service? Then, learn more about solar panels is one the best investments you could ever have! If you have question regarding the solar power calculation, please comment down below.