Types of PVT Collectors: Complete Guide to Different Photovoltaic Thermal Technologies

1. What Is a PVT Collector?

A photovoltaic thermal collector is a hybrid solar collector that produces:

• electricity;
• thermal energy.

A conventional PV module converts sunlight into electricity.

A PVT collector adds a thermal recovery system behind or around the photovoltaic layer.

Basic energy flow:

Solar Radiation

↓

PVT Collector

↓

Electricity

+

Thermal Energy

The IEA SHC Task 60 describes PVT collectors as hybrid systems combining photovoltaic conversion and thermal energy collection.

2. How Are PVT Collectors Classified?

PVT collectors can be classified from different perspectives.

Classification by Heat Transfer Medium

Liquid PVT

Uses liquid as the heat transfer medium.

Examples:

• water;
• glycol;
• brine solutions.

Air PVT

Uses air as the heat transfer medium.

Examples:

• ventilation air heating;
• building air systems.

Classification by Collector Structure

Flat Plate PVT

The most common configuration.

Structure:

PV Layer

↓

Thermal Absorber

↓

Heat Transfer System

Concentrating PVT

Uses optical concentration to increase solar energy density.

Structure:

Sunlight

↓

Optical Concentrator

↓

PV + Thermal Receiver

3. Liquid PVT Collectors

What Is Liquid PVT?

Liquid PVT uses a fluid circulation loop to remove heat from the collector.

The fluid absorbs thermal energy and transfers it to a useful application.

System concept:

PVT Collector

↓

Liquid Loop

↓

Heat Exchanger

↓

Heat Application

Common Heat Transfer Fluids

Liquid PVT systems may use:

• water;
• water-glycol mixtures;
• brine solutions.

The choice depends on:

• operating temperature;
• climate;
• freeze protection requirements.

Advantages of Liquid PVT

1. Higher Heat Transfer Capability

Liquids generally transfer heat more effectively than air.

This allows:

• efficient heat extraction;
• compact system design.

2. Suitable for Heat Pump Integration

Liquid PVT is commonly considered for:

• heat pump source systems;
• low-temperature heating;
• domestic hot water.

3. Flexible System Integration

Liquid loops can connect with:

• storage tanks;
• heat exchangers;
• heat pumps.

Limitations of Liquid PVT

More Components Required

A liquid system usually requires:

• pumps;
• piping;
• controllers;
• hydraulic components.

Maintenance Requirements

The system requires attention to:

• fluid quality;
• leakage prevention;
• circulation performance.

Typical Applications

Liquid PVT is suitable for:

• residential heating;
• hot water systems;
• heat pump applications;
• commercial buildings.

4. Air PVT Collectors

What Is Air PVT?

Air PVT uses air circulation to recover heat from the PV module.

System concept:

PV Surface

↓

Air Channel

↓

Warm Air

↓

Building / Ventilation System

Advantages of Air PVT

1. Simple Heat Transfer Medium

Air is:

• easily available;
• non-corrosive;
• simple to handle.

2. Suitable for Ventilation Applications

Air PVT can provide:

• preheated ventilation air;
• space heating support.

3. No Fluid Leakage Risk

Compared with liquid systems:

• no antifreeze;
• no hydraulic leakage.

Limitations of Air PVT

Lower Heat Transfer Capacity

Air has lower heat transfer capability compared with liquids.

Larger Air Channels Required

Effective airflow may require:

• larger ducts;
• ventilation integration.

Typical Applications

Air PVT is suitable for:

• ventilation systems;
• agricultural buildings;
• air heating applications.

5. Flat Plate PVT Collectors

What Is Flat Plate PVT?

Flat plate PVT is the most common PVT collector architecture.

The collector has a flat photovoltaic surface combined with a thermal absorber.

Basic structure:

Solar Radiation

↓

PV Module

↓

Thermal Absorber

↓

Heat Transfer Fluid

Advantages of Flat Plate PVT

1. Mature Design Concept

Flat plate structures are widely used because of:

• simple geometry;
• practical manufacturing;
• compatibility with building installation.

2. Flexible Integration

Flat plate PVT can be adapted for:

• liquid systems;
• air systems;
• different mounting solutions.

3. Suitable for Building Applications

Common applications:

• residential buildings;
• commercial buildings;
• energy-efficient projects.

Limitations of Flat Plate PVT

Performance depends strongly on:

• absorber design;
• insulation;
• heat transfer structure;
• operating conditions.

6. Concentrating PVT Collectors

What Is Concentrating PVT?

Concentrating PVT uses optical systems to focus sunlight onto a receiver.

Concept:

Sunlight

↓

Concentrator

↓

PV / Thermal Receiver

Advantages of Concentrating PVT

1. Higher Solar Energy Density

Optical concentration can increase energy intensity at the receiver.

2. Potential for Higher Temperature Applications

Concentrating systems may support applications requiring higher temperatures.

Limitations of Concentrating PVT

More Complex System Design

Requires:

• optical components;
• tracking systems in some designs;
• precise alignment.

Less Suitable for Simple Building Applications

The complexity may limit use in ordinary rooftop projects.

Typical Applications

• research projects;
• high-temperature solar applications;
• specialized energy systems.

7. Comparison of Different PVT Types

8. How to Select the Right PVT Collector

The correct PVT type depends on the project.

Step 1: Define Energy Demand

Ask:

Do you need:

• electricity only?
• heat only?
• electricity + heat?

Step 2: Define Thermal Application

Heat Pump System

Recommended:

• liquid PVT;
• brine PVT;
• DX PVT depending on system design.

Ventilation Heating

Consider:

• air PVT.

High Temperature Requirement

Consider:

• specialized concentrating PVT.

Step 3: Consider Climate and Installation

Evaluate:

• outdoor temperature;
• solar resources;
• available installation area;
• maintenance requirements.

Step 4: Evaluate Complete System Performance

Do not select only by collector efficiency.

Consider:

• annual energy yield;
• system integration;
• operating conditions;
• energy demand matching.

Decision Guide