Orientation & Positioning of solar module

31st Oct 17  

With the latest quoted tariff of Rs 2.65per unit energy from solar energy in Gujarat post Goods and Service tax (GST), it seems that price close to Rs. 3/kWh from solar energy would be a new normal. Such low prices would mean that the developers (of the power plant) need to have the entire system and its applicable parameters optimized for maximized energy output to ensure their maximum profitability. The solar PV modules are heart of the power plant and in order to generate maximum energy it needs to be positioned at an optimum location. Any variation in the placement (in terms of orientation and inclination) may lead to loss of energy (and hence money) which may inturn damage the modules (due to differential output within modules) in long run. It is hence important to understand the placement of solar module in the power plant.

The figure below shows typical layouts of solar power plant. The figure on the left shows a solar power plant where the modules are facing towards south (generally what we see in India). The figure on the right shows the solar power plant installation where the modules are facing east west. Such configurations while not prevalant in India may have to be considered if there are installation constraints. This article would help the readers understand why such configurations are required.

Figure 1: Typical layouts of solar power plant. South facing module (in the left) (Source: Waaree project gallery) and East West facing modules (in the right)(Source: Google images)

The sun as we know rises in east and sets in west. Additionally, it also changes is position (season wise) in sky with respect to a fixed pointon earth. The orientation of solar module may be defined by two parameters namely azimuth and tilt angle (Figure 2). Tilt angle of solar module is defined as angle between the horizontal ground and the solar module. Azimuth angle of solar module is an indicator of alignment of the module with respect to (true) south. For modules facing (true) south this angle is 0o and for module facing (true) north this angle is +/- 180o.

Figure 2: Azimuth and tilt angle of solar panel (Source: Google Images)

India encompasses 29 states and 6 union territories spread between 84' to 376' north latitude and 687' to 9725' east longitude which causes varied climatic conditions across the country. Such varied climatic conditions coupled with varying latitude would affect the solar irradiance between places at same time.Hence in order to reach the countrys target of 100 GW from solar energy by 2022, it is important to understand the effect of orientation and positioning of the module at various locations. For this study, the locations are selected based on all the four directions(Ahmedabad in west,Delhi in north, Kolkata in east andTiruchirappalli in south).

The sun (in the northern hemisphere) traverses from east to south (in the sky) to west. Hence the orientation of solar panels can only be directions other than the north. In order to understand the best orientation for solar modules, a comparison (of specific production) between south facing module and east-west facing modulefor the cities (mentioned above) is carried out. Additionally, the tilt angle of the modules was varied at 0o, 5o, 10o, 15o and the latitude of the place for both the orientations. These conditions are simulated in PVsyst (which is industry standard software) and a plant size of 100 kWp is considered. The system components i.e the modules and inverters are standard Waaree products.

As evident from the figure below, the south facing modules at any location due to increased irradiance falling on it (at peak noon) compared to east west facing modules would generate more energy. Additionally comparing the varied tilt angles, the modules placed at tilt angle equivalent to the latitude (of the city) would generate the maximum energy output compared to any other tilt.

Figure 3: Specific production of south facing modules in Ahmedabad (Data source: PVsyst)

Figure 4: Specific production of east-west facing modules in Ahmedabad (Data source: PVsyst)

Figure 5: Specific production of south facing modules in Delhi (Data source: PVsyst)

Figure 6: Specific production of east west facing modules in Delhi (Data source: PVsyst)

Figure 7: Specific production of south facing modules in Kolkata (Data source: PVsyst)

Figure 8: Specific production of east west facing modules in Kolkata (Data source: PVsyst)

Figure 9: Specific production of south facing modules in Tiruchirappalli (Data source: PVsyst)

Figure 10: Specific production of east west facing modules in Tiruchirappalli (Data source: PVsyst)

While there are conclusive results on orientation and tilt angle of the solar module there are various other considerations required before installing the system in particular orientation and tilt. Firstly, increasing the tilt angle (and sometimes installing it at latitude angle) would lead to decreased shadow-free area at any given rooftop space. Such reduction would lead to significant reduction in capacity of solar power plant and reduced energy generation. Thus it is important to optimize the tilt angle to maximize energy generation while maintaining the performance of the plant. Secondly, while the south facing modules perform best, there may be various instances where due to constraints (say a tall building in south direction) or an east west building (where south facing modules may lead to reduced capacity and increased cost of under-structure) the modules may have to be placed east-west. While the energy output of east west facing module (as evident from above) decreases with an increase in tilt angle, the dust accumulation decreases with an increased tilt angle. While we recommend a tilt of close to 10o it may vary location wise based on various calculations.

Waaree is committed to delivering Avant grade products and services to its consumers. We have developed an online solar calculator which would give you an estimated cost of the solar system based on various inputs (such as total energy consumption or total connected load or required system size or available area). An additional customization of Module Mounting Structure (MMS) is also provided. While these costs are indicative in nature they can educate the consumers on their (approximate) initial investment.

Let us all pledge to make solar energy the primary source of energy in the near future.

RAHE ROSHAN HAMARA NATION