Sizing up solar panel requirements : Level Undergraduate 1st Year, 12th Standard

 What is Sizing up solar panels?

It refers to figuring out the right solar system size for your home, or institute. In other words, calculating solar system size is required in order to find out what is worth it for you. Moreover, it will let you know the solar panel system's electricity capacity.

Thus, it is learning, knowing and applying the concepts in calculating the solar panel system that fits your requirements. 

How will solar sizing help?

Solar sizing will help you in understanding and finding the following,

1. In reducing the carbon footprint
2. The total cost estimation of the solar panel installation
3. The roof space required for the installation
4. In offsetting the proportion of your electricity bill
5. In decentralizing the dependency on coal-based gird electricity supplies. 
6. In finding the total savings.

What are the factors that affect solar panel sizing?

There are the following factors that will help in finding the right solar panel size.

1. Solar insolation and weather: The number of hours and the amount of solar radiation are affected by the geographic location, altitude, and weather of the location. For e.g. India has a tropical/sub-tropical climate and has more summer months in comparison to Sweden. Therefore India receives more solar insolation than Sweden. 
2. Roof orientation: For e.g. The roof that is facing away from the sun, or has obstacles by trees or vegetation, will affect the sunlight from reaching solar panels.
3. System and battery losses: Besides solar panels, the system contains batteries, charge controllers, inverters and wires. They all contribute to some electricity losses. Thus, none of these is 100 % efficient. All such losses need to be taken into account by putting extra energy into the system.

How to calculate the solar size?

The following step-wise instructions will make it easy to calculate and estimate the solar size for your requirements.

Step 1: Find the average daily kWh usage of your house.

This can be done by collecting the bills for a year and averaging it down for a month i.e. by dividing the total electricity consumption (reported in the bills in units) by the number of months (by 12). To average the electricity consumption further down to per day requirements, divide the average monthly consumption by the number of days in the month (by 30 days). 

X units/month is an average electricity consumption for a month, then the average electricity consumption for a day will be,

X/30 = Y units/day.

Units can be converted to kWh as follows,

1 units = 1 kWh.

Thus, the average daily consumption of electricity in a house is Y kWh/day.

Step 2: Find the 'peak sun hours in your region.

A peak sun hour refers to 1,000 watts (= 1kW) intensity of light falling per meter-square of an area in an hour, i.e. 1 kW/m^2/h. In other words, the number of hours a meter square of an area receives 1,000 watts intensity of sunlight are the peak sun hours. The daily sun hours help you figure out the peak watt requirement from the panels. The peak sun hours vary with regions, seasons and weather. 

You can find a table and the reference below for a month-wise distribution of peak sun hours in India.

*http://www.indiaenvironmentportal.org.in/files/srd-sec.pdf

 

Step 3: Calculate the peak wattage rating of the solar panel.

Step 4: Sizing up the accessories i.e. batteries and inverter.

Step 5: Calculate the number and the cost of the solar panel system.

Method II: Sizing up the solar panel using roof size.

Calculating the total savings 

Numericals for practice:

Q.1. Your house consumption of electricity for a year is given in the table below:

MONTHS	TOTAL UNIT CONSUMPTION
JANUARY	400 units
FEBRUARY	500 units
MARCH	800 units
APRIL	1200 units
MAY	1800 units
JUNE	2000 units
JULY	1800 units
AUGUST	1300 units
SEPTEMBER	1200 units
OCTOBER	1200 units
NOVEMBER	700 units
DECEMBER	600 units

The standard wattage of a solar panel is 250 watts. The sun-peak hours of your area are 4 h.

Calculate,

1. The total power requirements from the solar panel array.
2. Calculate the number of solar panels that will be required.

Q.2.

The dimensions of the rooftop and the standard size of a solar panel are given. Based on the information calculate the following,

1. Find the number of 300 wattage solar panels for the roof (Note: report your answer in whole numbers)
2. What will be the total wattage electricity if the entire roof is utilized in installing 300 wattage solar panels?

You have decided that out of the total electricity produced from the panels 70 % will be consumed for the house and the remaining will be sold at 4 Rs/unit.

3. Calculate the earnings from selling solar energy for a month.

Also, you have calculated that the average grid electricity consumption of your house is 52.5 kW/day. You were initially paying 7/- per unit.

4. How much you were paying on the electricity bill for a month?

5. How much will you save once you decide to replace this electricity with solar panels?

6. Calculate the total savings

(Hint: total earnings from selling solar electricity (3) + payment on the electricity bill (4))