Published： March 28, 2026
Last Modified：August 5, 2026
Photovoltaic thermal (PVT) technology is not a single collector design.
Different PVT collectors are developed for different operating conditions, temperature requirements, and applications.
The main differences between PVT collector types come from:
Choosing the correct PVT type is essential because the best collector depends on the final energy application rather than the collector technology alone.
A PVT collector has two functions:
These two objectives can create different engineering requirements.
For example:
A heat pump source system may require:
A domestic hot water system may require:
An industrial application may require:
Therefore, PVT technology has evolved into different categories.
The IEA SHC Task 60 framework identifies multiple PVT collector concepts, including uncovered PVT, covered PVT, concentrating PVT, and other advanced concepts.
An uncovered PVT collector is one of the most common PVT designs.
It combines:
Unlike covered collectors, it does not use an additional transparent thermal cover.
The PV module absorbs sunlight.
Part of the energy becomes electricity.
The remaining heat is transferred through the rear thermal collector.
Basic structure:
Solar Radiation
↓
PV Module
↓
Thermal Absorber
↓
Heat Transfer FluidBecause the collector is directly exposed to ambient air, heat can be removed efficiently.
This can support:
Compared with more complex collector designs, uncovered PVT generally has:
Uncovered PVT is commonly considered for low-temperature systems.
Typical applications:
The main limitation is reduced thermal retention.
Without additional glazing:
Covered PVT collectors add a transparent cover layer above the PV module.
The purpose is similar to conventional glazed solar thermal collectors:
The cover creates an insulating effect.
Energy flow:
Solar Radiation
↓
Transparent Cover
↓
PV Module
↓
Thermal Absorber
↓
Heat Transfer FluidCovered PVT can provide:
The additional insulation may increase PV module temperature.
Higher PV temperature can reduce electrical efficiency.
Therefore, covered PVT requires optimization between:
Examples:
Air PVT collectors use air as the heat transfer medium.
Air flows through channels behind or around the PV module to absorb heat.
PV Module
↓
Air Channel
↓
Heated Air
↓
Ventilation / Heating ApplicationAir PVT provides:
Compared with liquids:
Typical applications:
Liquid PVT collectors use a liquid heat transfer medium to remove heat from the PV module.
Common fluids:
Solar Energy
↓
PV + Thermal Absorber
↓
Liquid Circulation
↓
Storage / Heat Pump / Heating SystemLiquid systems provide:
Liquid PVT is commonly considered for:
Brine PVT is a liquid PVT system using an antifreeze heat transfer medium.
The brine loop transfers low-temperature solar heat to a heat pump system.
PVT Collector
↓
Brine Loop
↓
Heat Pump Evaporator
↓
Heating SystemThe main advantage is improved protection against freezing conditions.
This makes brine systems suitable for:
Brine PVT is especially relevant for:
Direct expansion PVT integrates the solar collector directly into a refrigeration circuit.
Instead of transferring heat through an intermediate fluid loop, the refrigerant absorbs heat directly inside the collector.
DX PVT Collector
↓
Refrigerant Evaporation
↓
Compressor
↓
Heat Pump OutputPotential benefits include:
DX PVT requires careful design of:
Concentrating PVT uses optical systems to increase solar concentration.
Examples:
The objective is to increase energy density on:
Concentrating PVT is mainly associated with:
| PVT Type | Heat Transfer Medium | Main Advantage | Typical Application |
|---|---|---|---|
| Uncovered PVT | Liquid | Simple and efficient at low temperature | Heat pumps, heating |
| Covered PVT | Liquid | Higher thermal output | Hot water, higher temperature |
| Air PVT | Air | Simple air-based integration | Ventilation, drying |
| Liquid PVT | Water / fluid | Flexible system design | Buildings, heating |
| Brine PVT | Antifreeze fluid | Freeze protection | Heat pump source |
| DX PVT | Refrigerant | Direct refrigerant heat transfer | DX heat pump systems |
| Concentrating PVT | Various | Higher energy concentration | Specialized applications |
The correct selection process should start from the application.
Consider:
Consider:
Consider:
Consider:
The required operating temperature determines the suitable collector type.
General principle:
Application Requirement
↓
Temperature Requirement
↓
PVT Type SelectionImportant factors:
Cold climates require special attention to:
There is no universally best PVT collector.
The correct question is not:
Which PVT collector is the most advanced?
The correct question is:
Which PVT collector matches the required temperature, system design, and energy demand?
This principle is central to successful PVT system engineering.
The main types include:
Not necessarily.
Liquid PVT generally provides higher heat transport capability, while air PVT may be simpler for ventilation applications.
Liquid PVT, brine PVT, and DX PVT are commonly considered for heat pump integration.
Brine PVT uses an intermediate antifreeze fluid loop.
DX PVT uses refrigerant directly inside the collector.
Not always.
Covered PVT can improve thermal output, but increased temperature may affect electrical performance.
This article applies:
Final system selection should consider:
Different PVT collector types are designed for different applications.
Solis PVT provides technical guidance for selecting suitable PVT solutions based on: