1 MW Solar Power Plant: Engineering or Tonnage?

Same Power Plant, Two Different Quotes

Imagine you receive two quotes for a 1 MW solar power plant. One proposes a 30-ton steel mounting system, the other a 48-ton system. Both are priced similarly. Which one would you choose?

Most investors think, "48 tons should be stronger." But in engineering, more material doesn't always mean better. In fact, sometimes it shows the opposite: inadequate engineering.

This article explains, using technical data, where tonnage discrepancies in solar energy mounting systems come from, the critical errors in calculation methods, and how pricing models mislead investors.

S450 vs S235: Same Strength, 37% Less Steel

The quality of steel used in solar energy installation systems directly determines the overall weight of the structure. Here's a comparison:

Parameter	Design with S235	Design with S450
Yield Strength	235 MPa	450 MPa
Total Steel Per 1 MW	~48 tons	~30 tons
Shipping Cost	High	37% lower
Foundation Load	Heavy	Lightweight — lowers foundation costs
Installation Time	Longer	Shorter — lowers labor costs

In the early years of the sector, for 1 MW 60–70 tons of steel were used, whereas today, with proper engineering 30 tons/MW It's possible. If you're still receiving offers for 48 tons, the question is: Is this additional 18 tons a structural requirement, or a product of the calculation methodology?

The Unseen Danger in SAP2000: Lateral Sprains

One of the most critical control points in steel structure design is lateral buckling(Lateral Torsional Buckling — LTB). Especially in solar mounting systems, purlins are subjected to compression at their upper flanges under wind suction loads and are prone to lateral buckling.

Where does the problem begin?

In structural analysis programs such as SAP2000, the program assumes the nodes to be laterally braced by default. When a member is divided at intermediate nodes, each sub-segment is treated as a separate unbraced length. This misleads many engineers, because:

• Solar panels do not give the purlins sufficient lateral support. The panel connection only partially restrains one flange; the opposite flange remains free to buckle.
• Under wind uplift, the compression flange is left unrestrained — compared with the design wind, the structure at much lower loads can collapse.
• Even if the program says "stress is sufficient," this result is unacceptable if LTB (Low Voltage Testing) is not checked. is not reliable. The user needs to manually define the unbraced lengths according to the actual situation.

So how is it done correctly?

To shorten the lateral buckling length, between the profiles sag rod (cross bracing) is added. The cost of a right rod increases by one cross-sectional size of the profile. is much more economical —because a 12-16 mm diameter steel bar is many times cheaper than increasing the profile along the entire purlin. Proper engineering doesn't increase the profile — it adds lateral support.

Instead of conservatively using a Cb (moment modification) factor of 1.0, calculating it according to the actual moment distribution is also part of section optimization. According to AISC 360, Cb=1.0 is the worst-case assumption (constant moment); in actual load distributions, the Cb value varies between 1.14 and 2.27. With the correct Cb value, the same profile can be achieved at the same safety level. longer spans can be spanned.

Wind Load Calculation: TS 498 or Eurocode?

Wind load is the most crucial parameter in solar energy installation system design. However, the standard used for its calculation fundamentally changes the outcome.

Parameter	TS 498 (Old Turkish Standard)	TS EN 1991-1-4 (Eurocode)
Turbulence Effect	Not calculated	Detailed model with turbulence intensity Iv(z).
Topography Factor	Limited	Hills, slopes, and coastlines are modeled separately.
Edge/Corner Region Separation	Simplified	Regional external pressure coefficients (cpe) — the edge area is up to twice as high as the center.
Dynamic Effect	It is neglected	Structural factor cscd modeled with
Conclusion	Significantly lower wind load	Realistic and safe.

Wind load calculated according to TS 498 is based on Eurocode. between 20% and 40%, depending on the configuration It could be lower. In TS 498, velocity pressure is simply calculated using the formula q = v²/1600 — there is no distinction between turbulence intensity, the first mode frequency of the structure, and the regional pressure coefficient. What does this mean? Choosing a thinner profile means a lighter structure and a "cheaper" offer on paper. But in real wind, this structure will start to stress much earlier than it was designed.

Low wind load = thin profile = cheap quote. But it is also the first plant to fall in a storm.

Eurocode is mandatory in Europe. However, in Türkiye, projects are still being produced that "pass" using TS 498. Investors only realize the difference when the first serious storm hits.

Pricing Model: Selling Steel Like a Sack of Flour

There is a fundamental difference in approach between Türkiye and Europe when it comes to pricing solar mounting systems:

European standard: $/kWp (or cents/Wp)

• The price automatically scales up when the panel power increases from 550W to 700W.
• The investor directly links the cost of the mounting system to the plant capacity
• Quotes for different panel power ratings can be compared

Türkiye practice: $/ton

• The comparison becomes meaningless when the panel power changes.
• The tonnage calculated with a 550W panel is not the same as with a 700W panel.
• Heavy construction looks less like it's "expensive" and more like it's "purchased a larger quantity."

Tonnage-based pricing rewards heavy construction. More steel = more sales. By reducing weight through clever engineering, the company ends up selling less in the $/ton model.

kWp-based pricing rewards engineering quality. A company that can achieve the same capacity with less material offers a more competitive bid to the investor.

The question is simple: Are you buying a mounting system or steel?

Conclusion: Engineering Makes a Difference

Choosing a solar mounting system is not a steel purchasing decision. It is an engineering decision..

• The difference between 30 tons and 48 tons stems from the quality of the materials and the calculation method.
• A structure that "passes" SAP2000 without lateral buckling control may be unsafe in the field.
• Wind loads calculated using TS 498 may not reflect actual conditions.
• Pricing based on tonnage rewards heavy construction — pricing based on kWp rewards smart engineering.

Our only question to the investor is: Are you buying engineering services or tonnage?