Complete guide 2026
Designing and building an industrial solar farm: foundation piles, time per MW, up-to-date costs and ROI. Written by the company that builds the solar pile drivers for plants from 500 kW to 50 MW.
A ground-mounted solar farm is a power generation plant made up of dozens or thousands of photovoltaic modules installed on metal structures fixed directly into the ground. Unlike rooftop systems, a solar farm is built on marginal farmland, disused industrial land or dedicated sites: this makes it the standard solution for capacities above 500 kW and up to 50 MW and beyond.
The most important difference from residential solar is not size but design logic. In a solar farm the dominant constraint is the density of foundation piles: each MW needs between 350 and 450 piles for fixed structures, and up to 600 for single-axis trackers. How well these piles are driven determines the structural life of the plant over its 25-30 years of service.
A modern solar farm is not simply a collection of panels: it is an engineering project that brings together geotechnical assessment of the ground, choice of pile profile, mechanised pile driving, optional BESS storage, monitoring systems and connection to the high-voltage grid. Get the foundation phase wrong and you will pay for extraordinary maintenance throughout the life of the plant.
Understanding how the cost of a solar farm breaks down lets you judge which items can be squeezed and which cannot. The six main items:
This is the largest cost item and the one with the widest room for negotiation. 600 W mono-PERC modules are today's standard, but the choice between Chinese, European and Korean Tier 1 manufacturers has a significant impact on warranty, performance and EU anti-dumping clauses.
Single-axis trackers or fixed structures. A tracker produces 15-25% more but costs twice as much and needs more maintenance. The choice depends on latitude, ground type and expected payback time.
The piles are the structural element that ties the structure to the ground for 25 years. Galvanised steel C or H profile, 2-3.5 m long, driven with a self-propelled hydraulic pile driver. A typical MW needs 350-450 piles for fixed structures and up to 600 piles for trackers.
Central or string inverters, DC and AC cables, combiner boxes, step-up transformer, MV substation. The choice between central and string affects cost, reliability and continuity of service.
Connection to the primary substation of Terna or of the local distributor. This is the most variable item: a plant close to a substation can get by with a few hundred thousand euros, an isolated one may need kilometres of dedicated power line.
Autorizzazione Unica or PAS, detailed design, site supervision, safety, municipal fees, grid connection. In Italy, permitting time is the most unpredictable item and can range from 12 to 36 months.
The foundation phase accounts for only 5-8% of the total cost of a solar farm, but 100% of the structural risk. A plant with badly driven piles will run for its whole service life with misalignments that reduce yield, eccentric loads that stress the structures and, in the worst cases, settlement that means replacing entire rows of trackers.
There are two solutions for the foundations of a solar farm: piles driven with a hydraulic pile driver and cast-in-place concrete foundations. The pile driver is the dominant choice in 90% of solar farms because it eliminates concrete curing time (7-28 days), needs no formwork, generates zero site waste and guarantees consistent quality whatever the weather.
The self-propelled hydraulic pile driver is the reference technology for driving. The TURCHI 300F is a self-contained tracked pile driver that moves around the site under its own power, with no support excavator: a single operator positions the machine, aligns the pile and drives it. The result is millimetre-accurate, repeatable driving, with GPS traceability of every pile for structural acceptance testing.
The choice of pile profile is just as important. C profile (cheaper, for light trackers), H profile (for heavy structures and difficult ground), tubular (for high-load single-axis trackers). TURCHI makes custom dies on request for any profile.
The machine that carries out this phase: TURCHI 300F, data sheet and full specifications
Anyone designing a solar farm needs to be clear on two numbers: the cost per installed MW and how long the site work takes. In 2026 the reference values for a well-designed utility-scale plant in Italy are:
| Item | €/MW range 2026 | Notes |
|---|---|---|
| Photovoltaic modules (Tier 1) | 280,000-360,000 | 600 W mono-PERC |
| Structures (fixed/tracker) | 70,000-140,000 | Tracker +70-100% |
| Piles and driving | 35,000-55,000 | 350-450 piles/MW |
| Inverters + electrical BoS | 90,000-140,000 | String or central |
| HV connection | 40,000-120,000 | Varies with distance to substation |
| Permitting and design | 35,000-80,000 | Lead time 12-36 months |
| Site and services | 40,000-80,000 | Site supervision, safety |
Indicative 2026 total: €600,000-950,000/MW turnkey, excluding land. Figures updated to the first quarter of 2026: swings of 10-15% are normal depending on size, location and supply conditions.
Actual site time (excluding permitting) for a 1 MW solar farm is typically 6-10 weeks: 2 weeks of ground preparation, 3 days of pile driving with the TURCHI 300F, 2-3 weeks installing structures and modules, 2-3 weeks of cabling, testing and commissioning. For 10 MW plants the time factor scales linearly on the piles (30 days) and sub-linearly on modules and cabling, thanks to parallel crews.
An average 1 MW plant typically needs 400 piles for fixed structures. With a conventional excavator attachment the pile-driving phase lasts 6-8 working days: one operator on the pile driver plus an excavator operator, with frequent stops for repositioning.
With a TURCHI 300F the same job is finished in 3 working days with a single operator. The tracked machine moves along the layout line under its own power, the arm positions the pile, the hydraulic hammer drives at controlled energy and the GPS records the coordinates of every pile for acceptance testing.
The economic advantage is measurable. Direct saving: 3-5 person-days on site (operator plus excavator operator), no excavator hire, simpler site logistics. Indirect saving: earlier commissioning (2-3 weeks gained on the overall schedule), less exposure to weather risk and a driving quality documented by GPS traceability.
On a 10 MW solar farm, which would take 60 days with traditional solutions, a TURCHI 300F completes the driving in 30 actual days: 30 fewer days on site, which typically means commissioning the plant a fiscal quarter earlier.
Choosing the pile driver is the most important operational decision of the foundation phase. Four parameters guide the choice:
For plants above 1 MW you need a self-propelled machine able to drive 100-200 piles a day. Below 500 kW an excavator attachment can still make sense. The TURCHI 300F is designed for the 500 kW to 50 MW range, with a declared productivity of 150 piles a day.
Single-axis trackers need large-diameter tubular piles (Ø 114 mm and above), while fixed structures need C or H profiles. The pile driver must accept custom dies for the chosen profile: TURCHI makes dies on request for any profile in 2-3 weeks.
Soft clay soils allow fast driving at reduced energy. Compact ground, gravel and rock layers call for one of the three blow energies available on the hammer (950 / 1,200 / 1,500 J) and sometimes controlled pre-drilling. A geotechnical assessment before work starts is always recommended.
Anyone building more than 10 MW a year is better off buying: the TURCHI 300F pays for itself in 10-14 months on medium volumes. Below 5 MW a year, a used machine with warranty is the best choice. TURCHI Daniele SRL is the manufacturer and does not offer direct hire: for hire there are authorised dealers throughout Europe.
Solar plants of 3+ MW and large projects
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