Overview

Solar PV-T: Benefits, Use Cases, Design and Optimization

Solar PV-T panels simultaneously convert solar energy into electricity and hot water, eliminating the need to choose between the two. This blog post summarizes a joint webinar held by Sunmaxx PVT and Polysun, introducing PV-T technology, showing examples of small and large installations, and demonstrating how solar PV-T systems can be effectively designed and optimized. Below we summarize the webinar, the full webinar recording can be found at the end of the blog.

What are PV-T Solar Panels?

PV-T Solar panels, also known as photovoltaic-thermal solar panels or hybrid solar panels, are hybrid systems that convert solar energy simultaneously into electricity and thermal energy. By combining photovoltaic cells with thermal collectors, they maximize the use of available solar energy and provide both electricity and hot water from a single system.
PV-T solar panels can be used in various applications, from residential homes to large industrial facilities. These systems are designed and optimized based on individual energy needs and local conditions.

What is the difference between Solar PV and Solar PV-T?

Difference between Solar PV and Solar PV-T: It shows a PV panel and a PV-T panel and compares the efficiency, electrical yield, thermal yield, CO-2 savings of an average PV panel and an average PV-T panel.

Difference between Solar Panel and Solar PV-T Panel

Traditional photovoltaic (PV) panels convert sunlight into electricity with an efficiency of about 20% (electrical efficiency), while photovoltaic-thermal (PV-T) panels achieve efficiencies of over 80% (20% electrical efficiency, 60% thermal efficiency) by simultaneously generating electricity and heat.
PV panels use photovoltaic cells to convert solar energy into direct current (DC) electricity, which is then converted to alternating current (AC) by an inverter to power household appliances. However, PV panels generate significant heat, often reaching temperatures of 70-80°C, which is typically wasted and causes a loss in cell efficiency.
In contrast, PV-T panels capture this excess heat and use it to generate thermal energy, reducing the overall panel temperature and improving electrical efficiency. These systems circulate a heat transfer fluid through tubes integrated into the panel, capturing thermal energy that can be used for hot water and heating. This dual functionality not only increases overall energy output, but also results in greater CO₂ savings compared to standalone PV systems, as well as space efficiency.

Versatile Solar PV-T applications: Heating, cooling, geothermal loop regeneration

Hybrid solar panels not only harness solar radiation for energy production but can also release or absorb heat from the surrounding environment. This makes them an efficient solution for both heating and cooling when combined with a heat pump.

Illustrates the difference between passive cooling with PV-T solar panels (Southern Europe) and active cooling with PV-T solar panels (Central Europe). It compares the temperature inflow into the PV T solar panel and the temperature outflow from the PV-T solar panel, cooling capacity, PV-T heat pump required.

PV-T Solar Panels Passive Cooling (Southern Europe)

In warm climates, PV-T panels provide passive cooling by radiating infrared (IR) heat into the sky at night. This natural cooling effect significantly reduces the need for air conditioning. During the day, the panels remain cooler due to the heat dissipated at night, maintaining a lower operating temperature. This results in

  • Lower daytime temperatures without active cooling
  • Only one circulating pump is required to maintain cooling
  • Cooling capacity of ~50 W/m², reducing electricity costs
  • A 10 kWp PV-T system (50 m²) can replace 2.5 kW AC

PV-T Solar Panels Active Cooling (Central Europe)

In moderate climates, PV-T panels can actively contribute to cooling when paired with a reversible heat pump. The system works by

  • Extracting heat from the hybrid solar panels during the day, reducing their temperature.
  • Allowing natural convection to cool the panels overnight
  • Eliminate the need for conventional air conditioning, making it a cost-effective solution
  • Provide cooling capacity of >100 W/m².
  • A 10 kWp PV-T system (50 m²) can replace a 5 kW AC

Regeneration of geothermal loops and ice storage tanks

In addition, PVT solar modules can recover heat from the ambient air, enabling the regeneration of geothermal loops and ice storage. By integrating PV-T technology with heat pumps, both heating and cooling needs can be met efficiently, reducing overall energy consumption and operating costs.

PV-T systems are used in different types of buildings. Below, we’ll show how PV-T solar panels are used in different building types and describe the hydraulic diagram, including its components, such as the solar thermal heat pump, needed to design such systems.

For residential applications, PV-T systems can be configured as either monovalent or bivalent setups, providing flexible solutions for space heating and domestic hot water.

Monovalent Solar PV-T thermal heat pump system

shows a example of a residential building with hybrid photovoltaic thermal collectors, monovalent thermal heat pump, buffer tanks
Hydraulic diagram monovalent solar thermal heat pump in residential buildings. It consists of PV T solar panels, a solar pump, a source mixer, and a thermal heat pump, 2 buffer thanks

In a monovalent system, PV-T modules on the roof serve as the sole heat source for a thermal heat pump. The system consists of PV-T solar modules, a solar pump, a source mixer, and a heat pump. A source buffer tank with a backup heater stores the collected thermal energy. In this example, the heat pump then distributes the energy to separate buffer tanks for space heating and domestic hot water. This configuration, as seen in Gernsbach, Germany, can effectively meet all heating needs using only PV-T and a thermal heat pump, even with complex pitched roofs.

Bivalent Solar PV-T thermal heat pump system

Residential building monovalent hybrid solar thermal heat pump system. It shows source mixer, heat pump, PV-T solar panels, earth collector /geothermal loop
Hydraulic diagram bivalent hybrid solar thermal heat pump system. It includes hybrid solar thermal panels, a heat exchanger, solar pump for regeneration, source mixer, earth collector, heat pump and puffer tank

Bivalent systems combine PV-T solar panels with geothermal energy sources. In this setup, PV-T solar panels work alongside an earth collector called a geothermal loop. The system includes PV-T modules, a heat exchanger, a solar pump for regeneration, a source mixer, a ground collector, and a heat pump. Buffer tanks store the thermal energy, which is then distributed for space heating and domestic hot water. This configuration allows for efficient heat source management and can regenerate the geothermal loop, improving overall system performance. An example of this system is in operation in Regensburg, Germany, with 20 modules producing 8 kWp electrical and 24 kWth thermal power.

PV-T Solar panels on larger multifamily residential buildings

For multi-family buildings, PV-T systems can be scaled up to meet higher demands. A case study in Berlin shows a 5-story, 4,481 m² building with a heating load of 245 kW. The system uses 66 PV-T modules (26.4 kWp) as a direct source for the heat pump and to regenerate geothermal probes. This installation demonstrates how PV-T technology can be effectively applied to larger residential structures, using external source management to optimize performance. It is also an excellent example of alternatives to air-to-water heat pumps, which are not allowed in this area of Berlin due to their noise emissions.

For multi-family homes, PV-T systems can be scaled up to meet higher demands. Examle in Berlin showcases a 5-story, 4,481 m² building with a 245 kW heating load. Shows large multifamily residential building and PV-T solar panels on the roof in Berlin.

Hybrid solar systems in industrial buildings

Industrial applications of PV-T systems offer significant potential for energy savings and CO2 reduction. A case study of a manufacturing plant illustrates the scale and benefits of such installations:

Shows installation of hybrid photovoltaic thermal panel on industry building.


The system consists of 1,000 PV-T modules generating 5.4 GWh/year of electricity and 1.9 GWh/year of heat, with a total capacity of 560 kWp. This will result in CO2 savings of 900 tons per year, twice the savings of a standard PV system. The installation, planned for 2025, reduces the investment from €10 million for a conventional system to less than €3 million, with an expected payback period of 7-9 years and a levelized cost of heat (LCOH) of 6-8 ct€/kWh.

Hydraulic PV-T diagram industrial buildings. Contains PV-T modules on the roof, a buffer tank for thermal energy storage, a heat pump to upgrade the thermal energy, an earth probe system for additional heat sourcing and storage, a source management system to optimize heat flow


The hydraulic scheme for industrial applications typically includes:

  • PV-T modules on the roof
  • A buffer tank for thermal energy storage
  • A heat pump to upgrade the thermal energy
  • A ground-source loop system for additional heat sourcing and storage
  • A source management system to optimize heat flow

This setup allows for efficient space heating, water heating, and even process heat generation. The system can operate in a bivalent mode, using the geothermal probe as an alternative or supplemental source during peak load periods. The flexibility of this design allows it to be adapted to different industrial processes and heating requirements.

Commercial Buildings with Solar PV-T Heating

PV-T systems in commercial buildings provide a comprehensive solution for both electricity and heat generation, as illustrated by the installation at a multi-purpose sports arena. This system will generate 3.0 GWh/year of electricity and 1.4 GWh/year of heat using 1,134 PV-T modules with a total electrical capacity of 465 kWp. The installation, scheduled for the second half of 2024, combines PV-T technology with geothermal probes, demonstrating the versatility of hybrid systems in meeting the diverse energy needs of large commercial spaces.

PV-T solar panels on a commercial building: a multifunctional sports arena installation


The design of solar PV-T systems for commercial buildings often involves complex integration with existing HVAC systems. According to the Polysun manual, these systems can be modeled using specialized software that allows detailed simulation of energy flows and system performance. The software can take into account various factors such as building orientation, shading, local climate data, and the specific energy consumption patterns of the commercial space.
Commercial installations often benefit from economies of scale, with larger roof areas allowing for more extensive arrays. These systems can be particularly effective in buildings with high heating and cooling demands, such as hotels, office complexes, and shopping centers. The integration of hybrid solar modules with heat pumps and thermal storage can provide a balanced energy supply throughout the year, reducing reliance on grid electricity and conventional heating systems.

PV-T District Heating

The technology is increasingly being applied to district heating networks, providing an innovative approach to low-temperature heat distribution in urban areas. One notable example is a district heating project in a historic city center that uses PV-T as part of a low-temperature network for both heating and cooling.
The first phase of this project, which is scheduled to be operational in Q3 2024, includes the installation of a rooftop system with 156 PV-T modules generating 64.4 kWp. This system is designed to work in conjunction with geothermal probes, contributing to their regeneration and overall system efficiency.

Distric heating using hybrid solar panels. Shows the thermal pipes of a district heating.


District heating systems with can be modeled and optimized using specialized software such as Polysun. These systems can be simulated to account for multiple heat sources, distribution networks, and varying consumer demands typical of district heating scenarios. The software allows the integration of sola PV-T with other renewable and conventional heat sources, enabling designers to design efficient and sustainable district energy systems.

Hydraulic diagram district heating including hybrid solar thermal panels, buffer tanks, thermal probes, heat exchanger, geothermal loop

PV-T in district heating offers several advantages:

  1. Decentralized heat production, reducing transmission losses
  2. Integration of renewable power and heat generation
  3. Potential for seasonal thermal storage
  4. Flexibility to meet both heating and cooling needs
  5. Contribution to urban energy transformation and carbon reduction goals
    The implementation of PV-T in district heating networks represents a significant step towards creating more sustainable and efficient urban energy systems, particularly in areas with limited space for large-scale renewable energy installations.

The Importance of a Design and Simulation Software


Engineers working on solar PV-T systems require sophisticated design and simulation software such as Polysun to optimize system performance and ensure project success. Here’s why such software is critical:

  1. Accurate performance prediction: Polysun allows engineers to simulate PV-T system performance under various conditions, providing detailed projections of electrical and thermal yields. This accuracy is essential for setting realistic expectations and designing efficient systems.
  2. Component selection and sizing: The software assists in the selection and sizing of appropriate system components and hybrid solar panels dimensioning, ensuring optimal integration of hybrid solar modules, heat pumps and storage systems.
  3. Financial analysis: Polysun provides comprehensive financial analysis tools that allow engineers to forecast system profitability, calculate payback periods, and demonstrate economic benefits to clients.
  4. Multi-system integration: PV-T systems often interact with other building systems. Polysun’s ability to simulate the integration of loads, battery storage, electric vehicles, and heat pumps is critical for designing holistic energy solutions.
  5. Regulatory compliance: By accurately modeling system performance, engineers can ensure that designs comply with local codes and qualify for incentives or feed-in tariffs.
  6. Professional reporting: Polysun generates comprehensive, visually appealing reports that engineers can use to present proposals to clients, stakeholders and regulators.
  7. Continuous Optimization: The software allows for continuous system optimization, enabling engineers to fine-tune designs and improve performance over time.

In conclusion, design and simulation software such as Polysun is essential for renewable energy engineers. It provides the tools necessary to design efficient, cost-effective and compliant hybrid solar systems, ultimately contributing to the wider adoption of this promising technology in residential, commercial and industrial applications.

Speakers:

Mirko Köhler (Business Development Manager at Sunmaxx PVT)

Hanna Gäbelein, Expert Design and Simulation Software Polysun

FAQ

Solar PV-T systems offer significantly higher total efficiency, exceeding 80%, compared to traditional PV panels which have an efficiency of around 20%. PV-T modules generate both electricity and thermal energy, effectively doubling CO2 savings compared to standard PV systems.

Solar PV-T systems improve electrical efficiency by cooling the PV cells. This cooling effect can increase annual electrical energy output by 4-12% compared to standard PV systems, with smaller systems (1-2 kWp) showing the largest improvement.

You may be confused by the terms. And you have every reason to be confused, as we’ve come across various names used to describe the same technology: the Photovoltaic-Thermal (PV-T) Solar Panels. The terminology can vary depending on the region, but they all refer to a hybrid technology that combines photovoltaic (PV) and thermal (T) elements into one unit, capturing both sunlight for electricity generation and heat for heating applications.

In English-speaking countries, you’ll typically see the following terms used interchangeably:

In the Netherlands and Belgium, the term PVT Panelen is most commonly used to describe these hybrid solar systems. The term is derived from the Dutch language and is widely recognized in those regions.

However, if we move beyond these countries, there are some subtle differences in the terminology used across various regions:

Norway

In Norway, PVT panels are generally used in technical and industry contexts, though the concept is gaining traction as part of the country’s growing interest in sustainable energy. The terminology is becoming more standardized, and you might find both photovoltaic-thermal panels and hybrid solar panels being used, especially when referring to products for residential and commercial use.

Sweden

Sweden has a strong focus on renewable energy, and solar PVT panels are referred to both in industry and governmental contexts as hybrid solar panels. Sweden’s push towards reducing carbon emissions has made PV-T technology a subject of much interest, especially in the context of energy-efficient buildings. PVT-moduler (PVT modules) is a common term in Swedish as well.

Denmark

In Denmark, the terminology is similar to Sweden and Norway, with solar PVT panels commonly used in both professional and everyday language. The Danish energy sector is highly innovative and open to new technologies, and hybrid solar panels are frequently discussed within sustainable energy forums. The term solcelle- og termisk paneler (solar cell and thermal panels) is also sometimes used, reflecting the hybrid nature of the technology.

United Kingdom

In the United Kingdom, PV T panels are increasingly recognized within both professional and consumer markets. The term hybrid solar panels is commonly used to describe these systems, though solar photovoltaic-thermal panels and PVT modules are also encountered in more technical contexts. The UK’s renewable energy market has been growing, especially with the government’s commitment to achieving net-zero carbon emissions by 2050. As a result, technologies like PV T are gaining attention for their ability to provide both electricity and heat from the same surface area.

In the UK, PV T systems are often highlighted in discussions about sustainable building practices, especially for residential properties. The term photovoltaic-thermal systems is also seen in the context of governmental and industry-led research into reducing energy consumption. Terms like solar thermal panels and solar photovoltaic panels may also be used, though these generally refer to separate technologies—one for electricity and the other for heating.

United States

In the United States, the terms PVT panels or PVT modules are gaining recognition, especially among professionals in the renewable energy field. The U.S. market is increasingly exploring hybrid solar systems as a means to optimize both electricity and heat generation. In casual contexts, you’ll likely encounter the term solar hybrid panels or solar photovoltaic-thermal systems. The technology is still emerging in the U.S., but there’s significant interest due to the potential energy savings and space efficiency of PV T systems.

Canada

In Canada, the terminology for PVT systems is becoming increasingly common, particularly as interest in renewable energy solutions grows across the country. The terms PVT panels and hybrid solar panels are widely used in both technical circles and by consumers. Canada’s cold climate makes it an ideal region to adopt PVT systems, as the ability to capture both heat and electricity is a huge advantage for energy-efficient homes and buildings. In French-speaking regions, the term panneaux solaires hybrides (hybrid solar panels) is frequently used, while modules photovoltaïques-thermiques (photovoltaic-thermal modules) may also appear in more technical documents. Additionally, some regions may refer to these systems as panneaux solaires thermophotovoltaïques (thermophotovoltaic solar panels), especially in Quebec.

The interest in PVT systems in Canada is also driven by government incentives aimed at promoting renewable energy solutions, as well as the potential for reducing energy costs in both residential and commercial buildings.

While PVT systems alone cannot meet all heating and electricity demands year-round in the UK, when incorporated as part of a hybrid heating system with an appropriately sized thermal store, they have the potential to meet about half of the electricity demand and over one-third of the hot water demand for a typical UK domestic property.

PV-T systems are commonly used in zero or near-zero carbon private new build homes or refurbishments, and by social or local housing associations aiming to reduce household energy bills significantly. They are also increasingly applied in commercial and industrial settings, as well as in district heating networks.