1.6.2. Purpose

PVT systems combine photovoltaic (PV) panels and solar thermal collectors into one hybrid unit, generating both electricity and useful heat.

PVT systems are innovative technologies that merge two types of energy generation: solar electricity and solar thermal energy. Photovoltaic (PV) panels convert sunlight directly into electricity, while solar thermal collectors capture heat from the sun to be used for heating water or air. By combining these two systems into a single unit, PVT systems can provide both electrical power and thermal energy, making them more efficient than separate systems.

Imagine a multi-purpose appliance in your kitchen that not only grills your food but also uses the heat generated to boil water at the same time. Just as this appliance saves time and energy by serving dual functions, PVT systems maximize the use of sunlight to produce both electricity and heat simultaneously.

By actively cooling the PV cells (using air or water), their temperature is reduced, which increases electrical efficiency while simultaneously capturing waste heat for water or space heating.

PV cells often lose efficiency as their temperature rises. When they get too hot, the amount of electricity they produce decreases. PVT systems use cooling mechanisms—like air or water—to keep the PV cells at a lower temperature, which helps them operate more efficiently. At the same time, the heat removed from the PV cells can be utilized for heating applications, addressing two energy needs with one system.

Think about a person who runs track on a hot day. As their body overheats, their performance declines. However, if they use an ice towel to cool down, they can run better. Similarly, PVT systems use cooling to enhance the performance of solar panels while also using the excess heat constructively.

Designs: Air-cooled and water-cooled PVTs. Flat plate, double-pass, building-integrated, and concentrator designs.

There are various designs of photovoltaic thermal (PVT) systems, each tailored for different applications and environments. Air-cooled systems use air to cool the PV cells, while water-cooled systems channel water for cooling. Additionally, the designs can vary from flat plates, which are simple and cost-effective, to more complex designs like double-pass or concentrator systems, which optimize heat capture further. Building-integrated systems are designed to be part of the building's architecture, providing a seamless solution for energy generation.

Just as there are various styles of shoes designed for running, hiking, or formal occasions, PVT systems have different designs to meet specific needs and conditions. A flat plate might be perfect for a residential roof, while a concentrator system could be optimal for a large solar farm in a sunny area.

Higher total energy yield (electrical + thermal) per area compared to separate systems. Improved PV cell life and output due to lower operating temperatures. Space-efficient, particularly on rooftops or limited sites.

One of the primary benefits of PVT systems is their ability to yield more energy per square meter by producing both electricity and thermal energy simultaneously. This dual generation not only optimizes land use but also enhances the lifespan of the PV cells because keeping them cool improves their operational efficiency. They are especially advantageous in urban settings where rooftop space is limited, as they maximize energy production in a small footprint.

Consider a restaurant that serves both lunch and dinner. By maximizing the use of their kitchen and staff, they can serve more meals than if they only operated during one shift. PVT systems do the same by getting the most out of the solar energy they capture.

Thermal output often somewhat lower than dedicated collectors. More complex system integration.

While PVT systems have numerous advantages, there are some limitations to consider. The thermal energy produced by PVT systems can be lower when compared to dedicated thermal collectors designed exclusively for heat production. Additionally, integrating these systems can be more complex than simpler standalone PV or thermal setups, requiring more sophisticated designs and engineering.

Think of a versatile multi-tool that can perform many functions, but sometimes not as effectively as a dedicated tool for a specific job. A multitool is convenient, but if you need maximum performance in one area (like cutting), a specialized tool might still be better.

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