Public Lab Research note

Analyzing optimum sites for installing solar panels by estimating solar panel size

by silentsairam | August 07, 2019 17:59 07 Aug 17:59 | #20459 | #20459

We all are aware that Solar energy is an important and easily available form of energy that can be stored and used in our daily life for various electrical and electronic devices to power it ON.

Real questions we do have would be,

  • What is the size of the solar panel has to be ordered to power our devices(ex: Fan, Lights, TV, Washing machine, etc)
  • Comes the size of the battery (storekeeper) that needs to be life long with less sun or without the sun.

Key factors we need to know,

  • The time that sun hits the roof in a given day which is generally known as sunshine hours.
  • Total electricity units (power consumption) we generate in our house/school/office etc.
  • Electricity Rates and Solar subsidies.
  • Equipment costs. (Panel, inverters )

How can we optimize the site for installing Solar panels?

  • The actual size of the Roof (Length and Breadth)[ The roof can be open space or triangle shaped]. For Rectangular shaped roof, Area = L X B; For Triangle shaped roof, Area = 1/2 X L X B. The usual math.

With this alone, we cannot estimate the exact kW or MW for solar panels and the total number of panels required for a rooftop.

  1. We need to know the Tree spacing in the area to check the carbon savings.
  2. The Direction at which the House/ building is facing. This helps in knowing the daylight hours of sunlight that hits the roof easily.
  3. Most important, appliances we use and connect directly to Grid.

How can we do this in the community or site?

  • With the help of Mapknitter(Ballon or Kite) capture the Aerial view of the whole rooftop of the site. This gives the exact view of the rooftop. This helps the community on whole to install solar panels and share the electricity in Off-Grid manner.

  • Using GoogleMap for the area we captured over the camera, measure the dimensions(Lx B) of the captured rooftop which has space in it to install Solar panels and we need to keep in points 1, 2, 3 also.

A formula that we could derive with all these measurements,

Total Watts we consume(based on monthly bills)(A),

Sun shining hours(summer and winter) for one year in months (B),

One Tree is equivalent to 2-3 kW panel (c),

EX: In my college, the per-day of electricity consumption is 198 W and Daylight is for nearly 6kWh and 8 Trees are there at my house( in & around that gives shade to the rooftop in the evening).

Now, A/ B gives , 198/7 = 28.2 W (approx, inculding all seasons)

Estimated panel size, 28.2 - (Tree spacing) = 28.2 - (2.5*8) = 28.2 - 17.0 = **11.2 W solar Panel size would be required for the site. **The number of solar panels varies with location, annual production (kWh) of the panel post-installation and manufacturing unit.

The above data is calculated for NIT Trichy, TamilNadu, India area where,

Average solar irradiation in TAMIL NADU state is 1266.52 W / sq.m

1kWp solar rooftop plant will generate on an average over the year 5.0 kWh of electricity per day (considering 5.5 sunshine hours)_



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