Solar Rooftop On Grid System Design

How To Design Solar Rooftop On Grid System:

    In this session we are going to discuss how to design solar rooftop on grid system. In this context I also want to say that solar rooftop on grid system is also known as grid tie or on grid solar system. Grid connected solar rooftop systems are not suitable for areas where transmission and distribution lines (electricity grids) are not available such as areas, hilly areas and villages. In this context, I would like to explain why such systems are not suitable in that area. Because the grid-tied solar inverter had an automatic relay system inbuilt when AC power is not available it does not work and shows an alarm.

    Solar PV systems can be divided in to two part one is stand alone PV system (Which use battery for energy storage) and other is Grid connected solar PV system. Grid connected PV system further categorized in to two parts.

1. Grid connected solar PV system for small power application i,e in households.
2. Grid connected solar PV system for Large power application i,e solar power plants.

Grid connected solar PV system for small power application:-

The main purpose of this type solar rooftop grid connected systems that are used for small power household application is to generate energy and consume it with in the house hold itself . Typically, the power rating of this type PV system can be in the range of 1 KW to Several 10 of KWs. The role of grid connectivity in case of small households system is to supply excess generated energy to the grid or take energy from the grid if there is any shortage.

    Under Jawaharlal Nehru National Solar Mission, it is planned that there will be approx 2000 MW of such PV systems to be installed in India by year 2022.

Grid connected solar PV system for small power application:-

    The grid connected PV systems for large power applications are mainly designed to act as power plants and the main purpose of these power plants is to generate power and supply it to the grid. In this way, they are equivalent to coal power plant or hydro power plants. Typically , the power rating are normally in the range of 1 MW to several 10 MW.

    Under Jawaharlal Nehru National Solar Mission, it is planned that there will be approx 1800 MW of such PV systems to be installed in India by year 2022.

For more information about Jawaharlal Nehru National Solar Mission - Click Here 

Components:

    Main components of a grid connected solar PV system are mentioned below :-

1. Solar PV module
2. A power conditioning unit / Inverter 
3. Load or grid 

    An electric grid can be considered as a large sink of energy wherein energy generated by solar PV can be supplied or taken from the grid when required. The idea of connecting PV system to the grid is to use the grid as energy storage so that the use of battery can be avoided as much as possible.

Configuration of grid connected solar PV system shown in below figure

Click Here For Single Line Diagram 

Design 300 Kw Solar Rooftop Grid connected ( Grid Tied)  PV system using 3 inverter each of 100 Kw with the following Specification's which are given below.

Module Specifications

1. 896x Waaree WSM-335 (April 2019)

   STC Rating 335 W

   Vmp 37.9 V

   Imp 8.84 A

   Voc 47.05 V

   Isc 9.45 A Click Here For Module Datasheet 

2. Inverter Specifications

   3x ABB PVS-100-TL

   Max AC Power Rating 100 kW

   Max Input Voltage 1,000 V

   Min AC Power Rating 600 W

   Min Input Voltage 350 V Click Here For Inverter Datasheet 

                   I.            No. of PV module

300,000 _÷ 335 = 895.52 ≅ 896

Approx. 896 Module

                   _II.            No. of panel in a string

As per inverter datasheet

MPPT voltage range – 480 to 850

Maximum input DC voltage range – 1000 V (Mentioned on Inverter specification)

Maximum voltage range of inverter ÷ Module V_oc

1000 ÷ 47.05 = 21.25 ≅ 22 Module we can connect is series but maximum voltage range of one sting should be must lies between inverter MPPT range so lets find this 

22 X 37.9 =833.8 V this data range lies our MPPT voltage range.

13 * 37.9 = 492.7 V this data is also lies our MPPT voltage range.

Hence

Maximum & Minimum numbers of series connected PV modules are respectively 22 Module and 13 Module 

Thus

                   We are connect 20 module in series.

             III.            String Power

Module wattage * No. of PV module connected in series

                   335 * 20 = 6,700 Watts

            IV.            No. of sting

Total No. of PV module / No. of PV module connected in series

                   299 ÷ 20 =14.95 ≅ 15

Or

                         Total wattage of plant / String power

                                      100,000 ÷ 6,700 = 14.92 ≅  15 Strings

                                      15 * 6,700 = 100,500 Watts or 100.5 Kw Approx.

                                                     ≅ 100 Kw

No. of strings * 13 module per string * wattage of module should be equal to our plant capacity

                   15 * 20 * 335 = 100,500 watts Or 100.5 Kw

               V.            Conclusion

S.No.	Item	Make	Quantity
1	Solar Photovoltaic Module	Waaree	896 No’s
2	Grid Tied Inverter	ABB	3 No’s
3	No. of Module Connected In Series		20
4	Total No. of Strings		15
5	Total Capacity of plant	100 X 3 = 300 Kw

Here Report copy of above design is attached for your better experience,you can find these copy  by clicking on fallowing links which is given below.

1. Project design report get by Helioscope - Click Here 
2. Project design report get by PVsyst - Click Here

Click here for off grid system Design