Modules & Mounting — how the park is built technically

In short: The technology choice determines yield, cost and maintenance. Today's standard is monocrystalline silicon with 21–23 % efficiency, often as a glass-glass bifacial module, on a single-axis tracker structure or fixed mounting. Trackers add roughly 10–15 % extra yield, but cost more and require more maintenance.

Module technologies

Mounting: fixed vs. tracker

What drives the choice in practice

• Site: in southern Germany with high direct irradiation, trackers pay off sooner than in the cloudier north.
• Land type: agri-PV favours vertical rows, normal grassland uses fixed mounting or a single-axis tracker.
• Investor profile: tracker installations deliver higher absolute yield and are attractive for PPA models; classic EEG (Renewable Energy Sources Act) projects are often fixed-mounted.
• O&M strategy: those doing their own maintenance tend to choose trackers; those wanting a full O&M contract choose fixed.

Modules and mounting — technology comparison, tracker options and decision matrix

Frequently asked questions

How long do the modules really last?

Manufacturers specify 25–30 years of linear performance degradation (e.g. after 25 years still ≥85 % of the initial output). Real long-term data confirm the trend for established manufacturers; with no-name modules the warranty is only worth as much as the manufacturer staying in the market.

Is bifacial worth the premium?

Clearly so over bright ground (gravel, snow); over normal grass, a moderate extra yield for a small premium. A standard decision in today's large-scale projects.

What happens if modules fail?

Individual modules can be swapped, and the full O&M contract covers the logistics. For larger serial damage (e.g. PID, glass breakage from hail), insurance applies.

Single-axis vs. dual-axis — the difference in detail

A single-axis tracker rotates the module row around a horizontal north-south axis and follows the sun from east to west — the tilt angle itself stays fixed, only the azimuth changes over the course of the day. This is the standard design in Germany and Central Europe, because it is mechanically simple, low-maintenance, and economically sound at moderate direct-irradiation levels. A dual-axis tracker additionally adjusts the tilt (elevation axis) and points the module almost perpendicular to the sun. This delivers the highest yield per module area, but doubles the number of mechanical components, drives and maintenance points. In regions with a high share of diffuse irradiation — as is the case across much of Germany — the extra yield from a dual-axis system usually does not justify the significantly higher cost; dual-axis trackers are found mainly in sun-rich regions with high direct irradiation (Southern Europe, North Africa, the south-western United States).

Yield gain from tracking — an estimate, not a guarantee

The commonly cited range of +10 to +15 % annual yield for single-axis trackers versus fixed south-facing mounting is a rough estimate that can vary considerably by site, latitude and the weather in any given year. The decisive factor is the share of direct irradiation: the more clear days with a high sun angle a site gets, the more it benefits from tracking. At cloudier sites with mostly diffuse light, the extra yield drops noticeably, because tracking brings little advantage over fixed orientation under diffuse irradiation. A reliable figure for a specific project only comes from a yield simulation using site-specific weather data (TMY data sets), not a blanket percentage taken from a tracker manufacturer's data sheet.

Added cost: weighing CAPEX against OPEX

Trackers increase capital expenditure (CAPEX) through drives, control electronics, extra foundations per row and a more elaborate mounting structure. The added cost compared with fixed mounting typically falls in the low-to-mid double-digit percentage range of the mounting cost — the exact figure depends heavily on the chosen system, row length and terrain, and should be confirmed project-specifically with the manufacturer or EPC contractor. On the operating-cost (OPEX) side, trackers add further line items: regular inspection of the drives, lubrication, replacement of actuators after a given number of operating hours, and — in case of a fault — repair of individual tracking units rather than a purely static structure with no moving parts. Whether the extra yield pays off against the higher CAPEX and OPEX is an economics question that should be checked over the project lifetime using the yield calculator and an LCOE assessment — as a rule, neither design is inherently superior.

Wind load and storm-protection mode

Tracker structures are more exposed to wind than flat, fixed mounting, because depending on the tracking angle the modules present a larger surface area to side wind. That is why practically every tracker system on the market has a storm-protection mode (stow position): once defined wind-speed thresholds are exceeded, the controller automatically moves the modules into a flat or slightly tilted protective position to minimise wind load. The design of the support structure, including stow logic, must meet the local wind zone requirements and forms part of the structural proof submitted during the permitting process. When choosing and dimensioning the site, it is worth checking this against the requirements of the permitting process, since wind-load calculations and structural stability must be documented there.

Maintenance burden: moving parts as a cost factor

The core structural disadvantage of trackers compared with fixed mounting is the number of moving parts: drive motors, gearboxes, shafts, bearings and sensors (anemometers, sometimes astronomical or optical sun-position sensors) must keep working over the entire 20–30-year plant lifetime. Every moving component is a potential failure point and raises maintenance effort compared with a purely static substructure without drives. Larger tracker systems often link several module rows to a shared drive (linked-row systems), which reduces the number of drives and therefore potential fault sources, but affects several rows at once if something fails. O&M contracts should therefore explicitly clarify who stocks spare parts for the drives and how quickly a fault is fixed — a tracker stuck in the stow position produces markedly less yield than planned.

Suitability criteria: when does tracking actually pay off?

Whether tracking makes sense depends on several site factors that should be checked before the technology decision is made:

• Direct-irradiation share: the higher the share of direct (non-diffuse) sunlight at a site, the greater the tracking advantage.
• Shading: tracker rows generally need wider row spacing than fixed south-facing mounting to avoid mutual shading at low sun angles — this reduces the installable capacity per hectare compared with more densely packed fixed systems.
• Ground conditions: tracker foundations (usually driven piles) must absorb the additional dynamic loads from tracking and the drive; on rocky or very soft ground a separate foundation assessment is needed.
• Plot shape: long, rectangular plots without a strong slope are better suited to tracker rows than heavily fragmented or sloping sites.
• Grid-connection profile: where the most even feed-in profile possible is wanted over the day (e.g. for PPA offtakers with a flat load profile), both east-west mounting and tracking support that goal.

Trackers in combination with agri-PV

On agri-PV land that is farmed in parallel, trackers also raise the issue of clearance height for agricultural machinery. The substructure must be sized so that tractors, harvesters or grazing livestock have enough room even in the tracker's least favourable position — depending on the type of use (arable farming, grassland grazing, specialty crops), the requirements for clearance height and row spacing differ considerably. Vertically mounted, usually bifacial modules without active tracking are often the more pragmatic solution for agri-PV, because they provide a fixed, predictable clearance between rows and have no moving parts near ground level that farm equipment could damage. A single-axis tracker with sufficient mounting height is still possible with appropriate site planning, but requires carefully coordinated structural and land-use planning.

System types on the market

Two basic designs have become established for single-axis trackers: independent-row trackers, where each module row has its own drive and can be controlled independently, and linked multi-row systems, where a central drive moves several rows simultaneously via a mechanical linkage. Independent-row systems are more flexible on uneven terrain and are less affected by partial failures; linked systems are often cheaper to buy per watt because fewer drives are needed. Control is either astronomical (the sun's position is calculated from date, time and site coordinates) or sensor-based, using optical sensors that respond to actual light conditions — in practice, many systems combine both approaches to get the best possible tracking behaviour under diffuse light or gaps in cloud cover. Specific manufacturer choices and product names are project-specific matters to clarify with the EPC partner and are deliberately not listed here in detail, to avoid promoting individual suppliers.

Grid integration: smoothing the feed-in profile

An often underestimated advantage of tracking systems lies not in the absolute extra yield but in the shape of the daily profile: while a fixed, south-facing plant produces a sharp midday peak, a single-axis tracker spreads the feed-in more evenly across morning and afternoon, because the modules actively follow the sun rather than being optimally aligned at a single point. That can benefit market-value revenue when negative or heavily depressed electricity prices occur around midday on sunny days (a cannibalisation effect under high PV penetration in the grid), because part of the generation shifts to off-peak hours with typically higher prices. For PPA contracts with offtakers wanting the most even load profile possible, this smoothing effect is often a standalone argument for trackers — independent of the pure yield figure. A quantitative assessment of the effect for a specific project should be based on market-value models rather than a blanket assumption.