Limited Roof Space? How PVT Hybrid Solar Systems Maximize Dual Energy Output from a Single Roof Area
Limited Roof Space? How PVT Hybrid Solar Systems Maximize Dual Energy Output from a Single Roof Area
Introduction: When Roof Space Becomes the Real Energy Bottleneck
In modern building energy projects, one constraint appears repeatedly across residential, commercial, and industrial sectors: roof space is limited, while energy demand keeps increasing.
Project owners, EPC contractors, and developers are often forced to make an early and uncomfortable decision:
Should the roof be used for photovoltaic (PV) panels to reduce electricity costs?
Or should it be reserved for solar thermal collectors to supply domestic hot water or space heating?
In theory, both options are attractive. In practice, however, roof area is rarely sufficient to deploy two separate systems at meaningful scale—especially in urban environments, retrofit projects, or buildings with complex roof geometry.
As electricity prices rise, fuel costs fluctuate, and carbon regulations tighten, this "either-or" choice becomes increasingly inefficient.
This is precisely the problem that PVT (Photovoltaic Thermal) hybrid solar systems are designed to solve.
Why Traditional Solar Solutions Compete for the Same Roof Space
To understand the value of PVT systems, it is important to first examine why traditional solutions fall short when roof area is constrained.
Photovoltaic Systems: Electricity Without Heat Utilization
Conventional PV systems are optimized solely for electricity generation. While they are highly mature and widely deployed, they have two fundamental limitations:
Excess heat is wasted
PV cells heat up during operation. This heat is typically dissipated into the ambient air, despite the fact that elevated cell temperature reduces electrical efficiency.
No contribution to thermal demand
PV systems do not provide hot water or heating. Buildings still rely on gas boilers, electric heaters, or heat pumps to meet thermal loads.
For buildings with significant hot water or heating demand, PV alone addresses only part of the energy equation.
Solar Thermal Systems: Heat Without Electricity Generation
Solar thermal collectors—such as flat plate collectors or heat pipe collectors—are designed to efficiently capture solar heat.
They perform well in applications like:
Domestic hot water
Space heating
Industrial low-temperature process heat
However, they also have clear limitations:
⚠ They generate no electricity
⚠ Electrical demand remains fully dependent on the grid
⚠ Additional roof space is required if PV is added later
You can explore these traditional solutions here:
Flat plate solar collectors:
→ /flat-plate-solar/pressurized-solar.html
Heat pipe solar collectors:
→ /evacuated-tube-solar/heat-pipe-collector-0.html
The Result: Inefficient Energy Density per Square Meter
When PV and solar thermal systems are installed separately:
⚠ Roof space must be divided
⚠ Mounting structures are duplicated
⚠ Hydraulic and electrical systems become more complex
⚠ Total usable energy per square meter remains limited
For projects where roof area is the limiting factor, this separation becomes a structural inefficiency.
What Is a PVT Hybrid Solar System?
A PVT hybrid solar system integrates photovoltaic electricity generation and solar thermal heat recovery into a single panel.
Instead of allowing excess heat to reduce PV performance, a thermal absorber mounted behind the PV layer captures this heat and transfers it to a circulating fluid (water or glycol mixture).
As a result, one panel delivers:
✓ Electricity from photovoltaic cells
✓ Useful thermal energy for hot water, heating, or process use
This integrated approach significantly increases the total usable energy output per square meter of roof area.
To learn more about the system concept, visit:
PVT Hybrid Solar Systems →
Core Advantage of PVT: One Roof, Two Energy Outputs
Energy Density in Practical Engineering Terms
From an engineering perspective, the key advantage of PVT is not theoretical efficiency, but energy density—how much usable energy a roof can deliver.
Based on typical project experience:
1 m² of PVT panel can deliver a combined energy value roughly equivalent to
0.5 m² of photovoltaic panels + 0.5 m² of solar thermal collectors,
under comparable operating conditions.
This is an indicative engineering estimate. Actual performance depends on climate, system design, and operating temperature. However, the underlying principle remains consistent: PVT maximizes roof value by serving both electrical and thermal demand simultaneously.
A Practical Example: 100 m² Roof Area Energy Comparison
To illustrate this concept in real terms, consider the following simplified but technically realistic example.
This example is for reference only. Final performance must always be calculated using project-specific simulations.
Project Assumptions
Available roof area: 100 m²
Location: Southern Europe / Mediterranean climate (e.g. Italy, Spain, Greece)
Annual solar irradiation: 1,600–1,700 kWh/m²
Building type: Small hotel, residential complex, or commercial building
Energy demand profile:
Daytime electricity consumption
Year-round domestic hot water demand
Scenario 1: PV-Only System
If the entire roof is covered with conventional PV modules:
Installed PV capacity: ~18 kWp
Annual electricity generation: ≈ 26,000–28,000 kWh/year
Thermal energy production: 0 kWh
Limitations:
⚠ Hot water demand remains unmet
⚠ Gas or electric heaters are still required
⚠ Excess PV heat is wasted
Scenario 2: Solar Thermal Only
If the same roof is used exclusively for solar thermal collectors:
Installed collector area: ~100 m²
Annual thermal energy production: ≈ 45,000–55,000 kWhth/year
Electricity generation: 0 kWh
Limitations:
⚠ No on-site electricity production
⚠ Grid dependence remains unchanged
Scenario 3: PVT Hybrid Solar System
Using a Soletks PVT hybrid system on the same 100 m² roof:
Electrical Output
Installed electrical capacity: ~16–17 kWp
Annual electricity generation: ≈ 23,000–25,000 kWh/year
Thermal Output
Annual recovered thermal energy: ≈ 30,000–38,000 kWhth/year
Combined Energy Output Comparison
| System Type | Electricity (kWh/year) | Thermal Energy (kWhth/year) |
|---|---|---|
| PV Only | 26,000–28,000 | 0 |
| Solar Thermal Only | 0 | 45,000–55,000 |
| PVT Hybrid System | 23,000–25,000 | 30,000–38,000 |
Key Insight: Although PVT does not maximize a single energy form, it delivers the highest total usable energy per square meter, which is critical when roof space is limited.
Economic Implications of the Example Case
Assuming typical European energy prices:
Electricity price: 0.18–0.25 EUR/kWh
Replaced gas or fuel cost: 0.06–0.10 EUR/kWhth
The PVT system may deliver:
Electricity savings: ≈ 4,100–6,200 EUR/year
Thermal energy savings: ≈ 1,800–3,800 EUR/year
➡️ Total combined annual energy value:
≈ 6,000–10,000 EUR/year, depending on usage patterns and local tariffs.
This combined value is the fundamental reason PVT systems outperform single-purpose solutions in roof-limited projects.
Choosing the Right Soletks PVT Solution
Not all PVT systems are designed for the same priority. Soletks offers two clearly positioned hybrid solutions.
PVT-E: Electricity-Priority Hybrid Panel
PVT-E is optimized for projects where electricity generation is the dominant objective.
Recommended for:
Commercial rooftops
Industrial buildings with high electrical loads
Office buildings and schools
TPV-Pro: Thermal-Enhanced Hybrid Panel
TPV-Pro is engineered for applications where hot water or heating demand is critical.
Recommended for:
Hotels and resorts
Hospitals and healthcare facilities
Residential heating and industrial hot water
Why PVT Simplifies System Design
From a system integration perspective, PVT reduces complexity by:
✓ Combining mounting structures
✓ Reducing roof penetrations
✓ Simplifying coordination between electrical and thermal systems
✓ Lowering long-term maintenance requirements
This integrated architecture is particularly valuable for EPC contractors and project developers.
Reliability, Quality, and Trust
Soletks PVT systems are developed under internationally recognized management systems:
ISO 9001 ISO 14001 ISO 45001
Products are designed in compliance with CE requirements, ensuring reliability, safety, and long-term performance in global markets.
Conclusion: Maximum Energy Value from Limited Roof Space
When roof space is limited, choosing between PV and solar thermal is no longer an efficient strategy.
PVT hybrid solar systems allow one roof to deliver both electricity and heat, maximizing energy density, improving economics, and simplifying system design.
With PVT-E and TPV-Pro, Soletks Solar provides application-driven solutions that align hybrid technology with real project needs.
🔗 Recommended Products
| Application | Link |
|---|---|
| Electricity-priority projects | View PVT-E Solutions → |
| Heat-dominant applications | View TPV-Pro Solutions → |
| Complete system solutions | View All Solar Systems → |
