Photovoltaics versus solar thermal energy: comparison of technologies, advantages and areas of application

Both technologies are excellent means of utilizing renewable energies. They are therefore suitable as tools for the so-called energy transition. Since photovoltaics is a means of converting solar energy into electricity, while solar thermal is used for generating hot water, the two technologies should be seen as complementary rather than opposing. An exception would be the use of solar power to operate heat pumps or instantaneous water heaters.

Basics of Photovoltaics and Solar Thermal: An Overview

While a photovoltaic module converts sunlight into electricity, solar thermal uses sunlight to produce hot water, which can be used to support a heating system.

Photovoltaics works by a solar module absorbing solar energy and converting it into direct current. To use the electricity in everyday life, an inverter is placed between the solar module and the household electrical system, which converts direct current into alternating current.

In solar thermal, water is pumped through the tubes of the solar thermal modules, where it is heated by solar energy and becomes part of the building's heating circuit.

Efficiency Comparison: Which Technology Provides More Energy?

The efficiency of photovoltaics compared to solar thermal is significantly lower. Photovoltaics has an efficiency of about 20%, while solar thermal can achieve an efficiency of about 80%. Therefore, comparing photovoltaics and solar thermal purely in terms of efficiency clearly favors solar thermal. However, this is only part of the truth, as solar thermal is limited to hot water production and is much less versatile than photovoltaics.

Applications: Where is Each Technology Best Suited?

Photovoltaics is suitable where electricity is needed. To bridge periods without sunlight, more and more households are investing in additional energy storage and focusing on efficient energy use with the help of smart home systems. Current applications include generating electricity through roof and facade installations, free-standing systems, and fence systems in the private sector. The generated electricity flows into the household grid to support daily needs, and can also be used to charge energy storage systems and electric vehicles.

Solar thermal, on the other hand, is used for hot water production and heating support. Although the applications of solar thermal are limited, the high efficiency of these systems and the need for hot water should not be underestimated.

Cost Efficiency and Economic Viability of the Systems

The cost efficiency and economic viability of both systems are high. Solar thermal is significantly cheaper than photovoltaics, but high electricity prices make the cost of purchasing a photovoltaic system relatively low. This also applies to the lower efficiency of photovoltaics. The advantage of solar thermal over photovoltaics is that heat storage is cheaper, and the space requirement for solar thermal modules is smaller than for photovoltaic panels.

The decision to choose one system or a combination of both is usually based on individual requirements. However, the general trend is towards a complete switch to electricity-based systems.

In summary, photovoltaic systems pay for themselves after about 10 to 15 years, while solar thermal systems take about 20 years. Photovoltaic systems are more expensive to purchase, but offer greater savings potential, provided that self-consumption is high.

Future Prospects: Development Potentials of Photovoltaics and Solar Thermal

Since almost all areas of life, including mobility, are currently undergoing a transformation towards electricity, the future prospects for photovoltaics are not only good, they seem to be an essential part of development, especially for households but also for companies to reduce costs and ensure a certain degree of autonomy.

However, solar thermal also has its justification due to its high efficiency. So the question is not "photovoltaics vs. solar thermal," but rather the specific application purpose and the corresponding suitability of one or the other means of using solar energy. Hybrid concepts can also be meaningful.

Promising for the future are smart concepts combined with artificial intelligence, which could give efficiency another significant boost. We can look forward to the changes and improvements that await us in the coming years.