In part 1 of this series you had an understanding of how to work out your power requirement.

What is the surface area of your solar panels required for your total power demand?

A typical example will be as follows. 

From the manufacturers catalogue;

The Size of the  PV module with a DC rating of 300W (Nom.) = 2080mm (l) X 992 mm (w) X 50 mm (d).

The weight of each panel is given there as 26 kg for the bare module. (This is important because if you intend to install the array on your roof top or on a built up structure, they should be capable of bearing this weight with strength to spare).

What is your total panel requirement?

Assuming your total building load is 4 kW, by a rule of thumb a PV panel area of 34 m2    is required for your needs.

34/2.08* 0.992 = 16.4 (i.e.17) PV modules as in the example.

And your roof structure or the built up structures should be capable of withstanding the load of;

17*26kg = 442 kg + the support structure weight (minimum).

In addition to this the weight of your maintenance staff, cross winds and any snow in the winter should be included in your structural strength calculations.

What is requirement of floor area for all these panels?

Solar panels are installed in such a way that the module (panel) is at a particular angle to the horizontal axis. This is known as the tilt angle. The Ground cover ratio (the ratio of PV Panel area to ground area required) is generally provided by the manufacturers.( If not in the catalogue ask them for it).

Shade is a critical factor affecting the performance of a solar module. Even if a small portion of it is subjected to it, the whole panel’s performance is jeopardized and that too not only in proportion to the shaded area.

The standard practice is to optimize the area used by working out the PV system to make up to the Ground Cover Ratio that matches the shading derate factor of 0.975 corresponding to a loss of 2.5%.

Work out the space requirement so that they are somewhat clustered together which would minimize power losses in the cables and also cut down the cost of same. The closer the array to the inverter panel, the less will be the power dissipated in the cables.

Where could these be installed?

Today due to new innovations (such as thin film technology) a solar panel buyer has several options in this regard. For example the development of thin film PV technology panels (which are physically flexible) can be blended in to your building architecture conveniently. (Roofing Tiles and shingles are also currently available).

Walls, windows and roofs are typical locations. On the other hand the conventional  rigid Mono crystalline silicon PV panels  having a thickness up to about 50mm, are traditionally installed on metallic supports mounted on roof or roof slabs. These also can be located in the surrounding landscape subject to it being in close proximity to the Inverter Panel (in the building).

There are three types of PV module installations for you to select depending on the Power demand, sophistication desired and the limit of your budget.  i.e. 

• Fixed single axis

• Fixed twin axes

• Tracking type – Single and Twin axes of rotation (generally found in large capacity arrays only)

The Azimuth and the Tilt angle of a PV module installation plays a big role in a good PV panel installation 3rd part of this series deals with it. Stay with us!