In general, solar photovoltaic plant require the geological report during feasibility study, because a proper geological report can provide the information about soil condition, rocks underground, water level and corrosion factors. Specifically, corrosion factors can ensure the proper design of anti-corrosion protection.
Once we have the geological report, we can start selecting the foundation type.
There are mainly three kinds of foundation: Ground screw, driven pile , and concrete foundation.
Ground screw can be divided into two kinds, with flange or without flange.
And according to the shape of blade, there are narrow continuous ground screw and the broad interval helical one. The broad interval kind has better pull-out strength than the narrow continuous one. It’s recommended to use the broad big blade ground screw in the high wind zone.
Pile driven mainly use pile driver machine to make the C post or H post directly into the ground. It’s so quick to install and no need for digging, which is more eco-friendly and go without the seasonal temperature restriction. But as for the hard soil areas or containing more gravel ,it’s may damage the galvanized layer. And it’s no good to use in the saline-alkali areas for the poor corrosion resistance.
So how to choose to the foundation for the solar farm?
1: If the site contains strong soil cohesiveness, and no rocks underground, then ground screw or driven pile are the best option. Driven pile is compatible with this type of soil. But if there rocks underground, then pre-drill and concrete might required.
2: If the site have poor soil cohesiveness and with rocks, concrete is the only option, because ground screw does not have enough resistance in poor soil cohesiveness; helical screw cannot go through the rock. Therefore, concrete is the only option for the foundation.
3: If the site contains loose sand and high water level or otherwise very low soil cohesiveness, this will cause driven piles or ground screw does not fit due to easily pull out, then the preferred foundation type would be broad interval helical screw or concrete foundation. Helical screw is ideal for locations with poor soil cohesion with high water level. The special design of the blade can provide strong enough pull out resistance in this type of soil.
The above information is just the preliminary guideline. The final selection has to follow the information of local geological report to make final decision. Antaisolar mounting systems is compatible with all foundation type, our engineers can also provided relevant information to assist you with your next project.