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Days in the sun

12d Model software was used by Aurecon in Thailand for the civil design of three Solar Farm projects located in the Tak and Sukhothai Provinces in Northern Thailand. These projects consist of Photo Voltaic solar panels spread over an area of approximately 575,000 m2 in Tak and 150,000 m2 in Sukhothai, with a combined generating capacity of 34 MW.

These Solar Farms will alleviate pressure on existing electrical networks and strengthen Thailand’s target for renewable energy. 12d Model was used for the design of the earthworks, roads and surface drainage.

The solar farms are located on gently sloping to steep terrain. Layers of hard rock also existed below the soil. The challenge was to regrade the land to a consistent and gradual slope that would make the foundations easier to construct.

The aspect of the grade of the sites had to be such that each panel faced south, with no shadow effect from adjacent panels. In Thailand, the optimum slope of each panel is 15° south, with a constant surface gradient of less than 2%.

All of the sites were previously used as farms, and there was no established drainage. Runoff from neighbouring properties needed to be cut-off, and effective drainage was required at each site to prevent flooding. As much of the electrical cabling is underground, the control of flooding was extra important.

Aurecon’s client for this project was Bouygues Energies and Services. The client was interested in cost savings and wanted cut and fill volumes optimised. They also wanted to limit cut in the underlying rock. Rock on the site was hard and is both costly and time-consuming to remove.

Aurecon’s 12d team leader for the project was Keerakiat Khamsee. Using 12d Model for the topographical survey and geotechnical report, the team was able to create TINs of the existing levels and the underlying rock layers. TINs are a form of vector-based digital geographic data and are constructed by triangulating a set of vertices (points). They produce a 3D surface that can be used to determine volumes. Closely spaced range files of 0.5m were used to accurately estimate the soil volumes and rock volumes.

Using experience, good design principles and some trial and error, the final excavation surfaces were created. Slopes and berms were set up to control drainage. The final design levels were then adjusted to balance cut and fill volumes, reduce excavation in hard rock and making sure that the aspect of the final surface maximised the solar gain in the Photo Voltaic Panels.

Several iterations were developed and refined, prior to completing the Final For Construction documents.

Using 12d Model, Aurecon was able to optimise the design to achieve the project objectives of maximising solar power from the Photo Voltaic panels, controlling stormwater run-off, balancing cut and fill, and limiting excavation in hard rock. Aurecon worked closely with Bouygues Energies and Services to complete the project on time and within budget.