This article summarises the findings of: Hernández et al. (2026), “Comparative evaluation of semi-transparent monocrystalline silicon and cadmium telluride photovoltaics for tomato cultivation in Mediterranean agrivoltaic greenhouses,” Smart Agricultural Technology, Vol. 13, 101848. https://doi.org/10.1016/j.atech.2026.101848 — Open access, Creative Commons CC BY 4.0.
#TLDR
- A controlled two-season trial in Murcia, Spain directly compared two semi-transparent PV technologies in agrivoltaic greenhouses over tomato crops.
- Monocrystalline silicon (PV-Si) outperformed cadmium telluride thin-film (PV-TF) on every key metric: energy output, crop yield, and light availability.
- PV-Si generated 726.8 kWh vs 488.4 kWh for PV-TF across both seasons.
- PV-Si tomatoes were 25% heavier than the control in winter-spring.
- The critical variable is Daily Light Integral (DLI): PV-TF dropped below the minimum crop threshold in winter. PV-Si did not.
- The PV-Si “checkerboard” panel layout is identified as a key design feature for maintaining light distribution quality.
Why This Study Matters
Agrivoltaics — growing crops under or alongside solar panels — is rapidly becoming a mainstream land-use strategy across Southern Europe, the Mediterranean, North Africa, and semi-arid agricultural regions worldwide. The concept is sound: the same land generates food and electricity simultaneously, and panels can moderate heat stress and water evaporation for crops during summer peaks.
But the design question that persistently divides developers and agronomists is: how much shading is too much?
The answer depends entirely on which PV technology you use, how the panels are arranged, and what the crop’s photosynthetic requirements are across different seasons. Most agrivoltaic studies address outdoor open-field systems. This trial specifically examines semi-transparent PV integrated directly into greenhouse structures — a format gaining significant commercial interest in Mediterranean tomato production regions.
Study Setup and Methodology
Location: Murcia, Spain — semi-arid Mediterranean climate with average summer temperatures of 30°C and winter temperatures of 12°C.
Duration: Two consecutive tomato growing seasons:
- Winter-spring season: 120 days (December 2023 – April 2024)
- Spring-summer season: 98 days (April – July 2024)
Greenhouse dimensions: Four independent, identical polyethylene greenhouses — each 3.9 m long × 2.0 m wide × 3.1 m high. The identical design across all four units isolates the PV technology variable from all structural and environmental confounds.
Measurements recorded:
- Air temperature, relative humidity, and solar irradiance — every 2 minutes
- Photosynthetically active radiation (PAR) — every 2 minutes
- Soil temperature and humidity — every 5 minutes at depths from 10 cm to 60 cm
The Four Greenhouse Configurations
| Configuration | Description | PV Technology |
|---|---|---|
| Control (C) | Standard polyethylene film only | None |
| Shading Net (SC) | Polyethylene + shading net in selected zones | None |
| PV-Si | Semi-transparent monocrystalline silicon PV | 18 modules, 59 W each, 50% transparency |
| PV-TF | Cadmium telluride thin-film PV | 18 modules, 40 W each, 50% transparency |
Both solar greenhouses used 18 modules per unit — nine installed on the roof and nine on the south-facing façade. Both PV technologies were specified at 50% nominal transparency, which is why a direct comparison is so valuable: nominal specs matched, but real-world performance diverged significantly.
The Critical Metric: Daily Light Integral (DLI)
DLI measures the total amount of photosynthetically active radiation (PAR) a plant surface receives over a full day. Tomatoes require a minimum DLI of approximately 10–12 mol m⁻² day⁻¹ for basic growth, with optimal development at 15–20+ mol m⁻² day⁻¹.
Winter-Spring DLI results:
| Treatment | Average DLI (mol m⁻² day⁻¹) | Above minimum threshold? |
|---|---|---|
| Control | ~20+ | Yes |
| PV-Si | 18.1 | Yes |
| PV-TF | 10.8 | Borderline / No |
Spring-Summer DLI results:
| Treatment | Average DLI (mol m⁻² day⁻¹) | Above minimum threshold? |
|---|---|---|
| Control | ~28+ | Yes |
| PV-Si | 25.4 | Yes |
| PV-TF | 17.0 | Yes (but with restrictions) |
Energy Generation: PV-Si vs PV-TF
| Season | PV-Si (avg daily) | PV-TF (avg daily) | PV-Si advantage |
|---|---|---|---|
| Winter-Spring (120 days) | 3.92 kWh | 2.58 kWh | +52% |
| Spring-Summer (98 days) | 4.07 kWh | 2.79 kWh | +46% |
| Total (both seasons) | 726.8 kWh | 488.4 kWh | +49% |
Crop Performance: Fruit Count and Weight
Winter-Spring season results:
| Treatment | Fruit count | Average fruit weight | Notes |
|---|---|---|---|
| Control | ~21 fruits | ~59 g | Reference |
| PV-Si | 21 fruits | 74 g | +25% vs control |
| PV-TF | 18 fruits | 50 g | Below control on both metrics |
Spring-Summer season results:
| Treatment | Fruit count | Average fruit weight |
|---|---|---|
| PV-Si | 30 fruits | 93 g |
| PV-TF | 23 fruits | 79 g |
The Checkerboard Advantage
One structural detail stands out in the study’s findings: the checkerboard (alternating) arrangement of PV-Si panels on the roof and south façade surfaces. Rather than covering the greenhouse roof with a continuous sheet of semi-transparent PV, the PV-Si configuration used an alternating panel-gap-panel pattern. This creates a spatial variation in light distribution across the plant canopy — no single zone is in permanent deep shade.
This finding has direct implications for how agrivoltaic panel layouts should be engineered. Uniform coverage at a fixed transparency percentage produces different results than an alternating coverage pattern at the same average transparency.
Key Conclusions
- PV-Si is the more suitable technology for Mediterranean agrivoltaic greenhouses across all evaluated dimensions.
- Nominal transparency (50%) is an insufficient specification metric. Two technologies at identical transparency produced dramatically different DLI outcomes.
- The checkerboard PV layout prevents shade-avoidance responses and maintains yield levels comparable to or exceeding outdoor controls.
- Nighttime thermal buffering and soil moisture retention are co-benefits of PV integration that can improve crop quality during winter-spring cycles.
- Summer heat mitigation via PV shading has limits. Panels reduce thermal fluctuations but do not eliminate peak temperature stress in extreme Mediterranean summers.
- PV-TF underperformed on both food and energy metrics. It is not recommended for agrivoltaic greenhouse integration in low-irradiance winter environments.
Solaracks Agrivoltaic Mounting Systems
Solaracks designs and supplies the elevated racking structures for open-field agrivoltaic installations. Our systems are engineered with the structural variables that this research identifies as critical:
- 3.5–5 m ground clearance — full tractor and machinery access, and greater light diffusion under the canopy
- Configurable inter-row spacing — calibrated to crop-specific DLI requirements and local winter solar angles
- Ground screw (helical pile) foundations — no concrete, minimal farmland disturbance, fast installation on active agricultural land
- HDG steel structure — hot-dip galvanized for 25+ year service life in outdoor agricultural environments
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