Solar System

Solar System

how to design my rooftop solar system?

how to design my rooftop solar system?

  • 2020/09/27
The capacity design of photovoltaic power generation system mainly involves the calculation of battery capacity, the number of batteries in series and parallel, the generation capacity of photovoltaic power generation system, and the number of photovoltaic modules in series and parallel.Design of Solar PV System is a very deep subject which needs lot of experience,expertise and skills .Then, I mainly from the design ideas following to express it.

Major system components:
  • PV Module – converts sunlight into DC electricity.
  • Inverter– converts DC output of PV panels
  • Battery –stores energy to supply electrical appliances when needed.
  • Load –whether the appliance is connected to the solar photovoltaic system, such as lamp, TV, computer, refrigerator, etc.
  • Solar Charge Controller– regulates voltage and current from photovoltaic panels to prevent overcharging and prolong battery life.

photovoltaic power generation system

1. Solar System
  • Determine power requirements
The first step in designing a solar PV system is to find out the total power and energy consumption of all loads required by the solar PV system
  • Calculate total Watt-hours per day for each appliance used.
Add the Watt-hours needed for all appliances together to get the total Watt-hours per day which must be delivered to the appliances.
Total energy requirement/day (Wh) = Wattage of appliance*No. of appliances*Hours of working
(Divide the above value by 1,000 to arrive kWh/day)
2.PV Module

The amount of solar energy available is limited by the amount of sunlight that falls on a solar panel per day and is expressed in kWh/m2/day. Insolation level varies from 4-7 kWh/m2/day in India.

As a Thumb rule- 4 kWh/day/kwp can be considered and is an average value which may vary across different regions in India.

Space Requirement : As a thumb rule 100-130 Square ft/kwp or about 12Sq.Mtr of shade-free roof area can be considered

System size = (Energy Requirement as estimated above*1.3) /insolation level

No. of panels = System size/Panel Rating

(Panel size varies from 130Wp to 325Kwp)


30- 45% safety margin may be considered while arriving the required inverter rating.

Required Inverter size = Total Wattage of all appliances*(1+45%)

Inverter size should be minimum 3 times the capacity of those appliances and must be added to the inverter capacity to handle surge current during starting if appliances like Compressors/Motos are part of the load consideration.

4. Battery

The battery type recommended for using in solar PV system is deep cycle battery. Deep cycle battery is specifically designed for to be discharged to low energy level and rapid recharged or cycle charged and discharged day after day for years. The battery should be large enough to store sufficient energy to operate the appliances at night and cloudy days.

Size of battery can be arrived by applying the below mentioned guidelines/Thumb rules

Calculate total Watt-hours per day used by appliances.

Divide the total Watt-hours per day used by 0.8 for battery loss.

Divide the above value by 0.6 for depth of discharge.

Divide the above value by the nominal battery voltage.

Multiply the above answer obtained with days of autonomy (the number of days that you may require the PV system to operate when there is no power produced by PV panels) to arrive the required Ampere-hour capacity of deep-cycle battery.

Battery Capacity (Ah) = Total Watt-hours per day used by appliances x Days of autonomy

(0.8 x 0.6 x nominal battery voltage)

5. Solar charge controller

The solar charge controller is typically rated against Amperage and Voltage capacities. Select the solar charge controller to match the voltage of PV array and batteries and then identify which type of solar charge controller is right for your application. Make sure that solar charge controller has enough capacity to handle the current from PV array.

As per standard practice, the sizing of solar charge controller is to take the short circuit current (Isc) of the PV array, and multiply it by 1.3

Solar charge controller rating = Total short circuit current of PV array x 1.3

I hope the above introduction can help you.If you have any questions about these, you can consult us.

AnHui TopSolarPower Tech. Co., Ltd.

AnHui TopSolarPower Tech. Co., Ltd (“TopSolarPower”) is the brand withover 1GW installed worldwide as of December 2019.Founded in 2004 by Bernie Zhou, TopSolarPower is offering PV system residential applications, floating PV plant.As a innovation in the solar industry, TopSolarPower possesses a dynamic team which consists of over 100 employees. Offering a wide range of solutions and services,TopSolarPower is committed to providing clean power for all and is steadfast in its efforts to becoming the global member of clean power conversion technology.

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