Addressing challenging terrains; optimizing production


India aims to achieve 450 GW of renewable energy capacities by 2030, of which about 280 GW is expected to be solar energy. The country has huge potential for solar power due to its geographical location and terrain.

While solar energy continues to gain currency the world over, a key hurdle is the availability of contiguous land receiving high irradiance suitable for solar PV plants. Solar plants need large chunks of contiguous lands that receive high irradiance.

Utility-scale solar PV plants are usually built on flat and open spaces, but as demand for solar energy rises, projects are developed in areas where topography presents multiple challenges. Such uneven terrains can reduce the usable land area and cause shading on solar panels, resulting in low energy yield.

The land available for solar power construction is often a wasteland that inherently has design and construction-related restrictions and challenges. In the early stages of designing a solar project site, several phases such as site feasibility and offtake strategies are critical for delivering a successful project.

Site layout can influence the areas of design and budget and can often be infeasible or dangerous for equipment and laborers. Hence, there is an urgent need for solutions that manoeuvre terrain flexibility and enable EPC companies, developers, and operators to maximize production in challenging locations.

Certain markets, such as Florida in the United States, have naturally leveled land, which makes the installation of solar PV plants easier.

However, flat terrain isn’t always an option. Solar PV plant sites in hilly regions need to undergo civil engineering to make the ground leveled for mounting. Undulating topography and grading land can alter rain run-off patterns on the site and displace native species. This often leads to installation delays and swelling project costs.

Some key terrain-related challenges during the construction of solar PV plants are land accessibility, low water table, land undulation, the load-bearing capacity of the soil, the mineral content of the soil, and its impact on below-ground corrosion.

Importance of topography

Topography is of great significance for designing of solar power plants. A solar PV site’s topography is capable of affecting project economics and deciding whether a project will be profitable. To illustrate, if the soil is not suitable for making a concrete foundation or if there is uneven terrain that requires grading, it can either cause project overruns or increase the project cost. Often in such cases, if there is an area of land that cannot be used at all, the plant ends up with a smaller capacity.

Topography is also crucial for estimating solar yield as shadow can impact the final result. Manufacturers often provide intelligent tracking algorithms to decrease this impact. For the above reason, during the site survey, it is crucial to check whether the terrain is feasible and suitable for the installation and placement of solar panels.

Mitigating terrain challenges

Based on decades of engineering experience in the solar industry, companies are developing new tools for solar power plant design on terrains with complex topography. Software are being developed with the ability to accurately calculate the groundwork associated with each possible implementation within the plot.

The 3D backtracking algorithm allows the positioning of trackers at an optimal angle to maximize electricity production. This tool also analyses different combinations of panels, trackers or tables, inverters, and storage systems.

Another such solar energy player has come up with a PV plant design software for conceptual and detailed design and analysis for solar PV plants. These tools empower EPC companies and designers to work within unconventional site boundaries, further promoting flexibility in the face of challenging site conditions.

The software combines thoroughly validated PV simulation algorithms with a user-friendly modern interface. It is an efficient and traceable method for reliable modeling in complex terrain and for accurate energy calculations and allows quick configuration of PV plant designs and simulation of PV layouts. The tool saves time in taking a plant to design by using an automated layout for fixed-tilt mounting systems and trackers.

Companies also use ground-mounted racks and install clusters of landscape panels fitted differently to the ground and placed close to each other. Arrays are installed on slight, steady grades with posts deeper into the ground, following the contour of the land.

Adopting a radical approach

A 290 MWp solar power plant in Gujarat, recently installed by Sterling and Wilson Renewable Energy Ltd (SWRE), is a good example of how various terrain-related challenges can be successfully mitigated.

As the uninhabitable land for plant construction had naturally occurring challenges, the state government was keen to convert this into industrially usable land for setting up gigawatt-scale solar power plants. The area receives a high level of solar irradiance and has huge swathes of contiguous and barren land.

SWRE adopted a different and radical approach to overcome the challenges at the project site. As the land fell under seismic zone IV, the pile depth was increased to various depths and diameters. Further, the local soil had lower SBC, and the ground condition had a liquefaction factor, which would have resulted in limiting the building foundation. Hence, for the building design to sustain these challenges, the MCR building foundation was supported with a higher diameter and deeper length pile foundation with pile caps.

Further, the plant was almost at sea level, adjacent to the local pond area with saucer-shaped pockets. Heavy rains and all the other challenges led to water stagnation and marshy soil conditions, causing hurdles in accessing the land.

To overcome these challenges, elevated roads with culverts were constructed and land ploughing was done for quick percolation and evaporation of stagnated water. In addition, waterproof insulation-type cables were used for underground usage and high-pressure pumps were installed to remove water from stagnated areas.

In another such example, SWRE successfully commissioned a 300 MWp solar power plant in Karnataka, even as the land was situated on hilly and rocky terrain. Small rivers passing through the project site caused disjointed and uncertain land parcels. The large-sized boulders obstructing plant construction were blasted and transported outside the plant.

Undulated lands were filled and compacted, and an array layout was designed. As the land was previously used for mining and had large, excavated pockets, it was first leveled up using normal soil and compaction.

With the river and nullahs passing through the land, a culvert and bridge were specially constructed for the movement of material, machines, and manpower.

The scattered and disjointed land parcels severely impacted the array layout and affected the inverter sizing and design process. This ultimately impacted material and cable quantities, resulting in a high-cost impact.

The array layout was customized to minimize land wastage and table sizes. Moreover, as the plant boundary fencing was porous due to land issues leading to the theft of critical material, the SWRE team ensured intensified night patrolling with additional security and drone surveillance.

In conclusion

As countries around the world look on, India is leveraging the opportunity to tap energy resources and bring in the latest technology to navigate complex geometry for the future of solar energy. The top Indian companies engaged in solar energy are fast exploring the need to use inclined terrains for siting PV power plants close to urban areas to reduce power transmission losses and avoid the high cost of transmission line infrastructures.

SWRE is a global pure-play, end-to-end renewable engineering, procurement and construction (EPC) solutions provider with a total portfolio of 12.6 GWp (including projects commissioned and under various stages of construction). It also manages an operation and maintenance (O&M) portfolio of around 7 GWp solar power projects. 

The views and opinions expressed in this article are the author’s own, and do not necessarily reflect those held by pv magazine.

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