Photovoltaics and Solar Thermal Energy: Free Energy from the Sun

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Photovoltaics and solar thermal energy are technical processes for extracting energy from radiation. Both heat and electricity can be understood as solar energy. But what are the differences and how do solar systems work?

Differences between photovoltaic systems and solar thermal panels

Photovoltaic systems and solar thermal systems are the two major solar power technologies available today. Photovoltaics uses semiconductor technology to convert solar rays into electricity. Therefore, photovoltaic panels only work when the sun shines and must be coupled with other energy generating mechanisms to ensure a constant supply of electricity.

Because the solar thermal energy produces only heat, it has the great advantage of being able to store the thermal energy produced. A storage tank should have a compact shape in order to have the best efficiency and keep the energy inside successfully.

Another advantage is the economy of space  that can be achieved by using solar thermal panels. As a comparison, a solar photovoltaic system could use up to 10 m² of roof space, as opposed to just 3 to 4 m² for a solar thermal system. This is due to its high efficiency. Thermal solar panels can turn around 80% of the radiation into heat, while photovoltaic panels have an efficiency between 15% and 20%.

Infrared radiation (heat waves) carry more energy than the visible light radiation on which most of the photovoltaics depend. Efficiency is also gained by the fact that it is not necessary to transform light energy into electricity.

How does a solar heating system work?

Solar thermal collectors (panels) are mounted on a roof in sunlight where they can absorb solar thermal energy. The solar fluid flows through the collectors by means of a pump that gives off heat to a water storage tank. When users need hot water, water from the storage tank fuels hot water consumers.


Functionality of a solar collector.

When the storage tank temperature is not sufficient to meet the consumption needs, the classic heat generator is activated to complete the storage tank temperature and assure a comfortable and constant temperature for the domestic hot water application.

Thanks to the free energy income from the solar collector field, the auxiliary heater does not switch on and off as often, therefore its usage is reduced and the lifespan extended.

The outcome? Every month, building owners pay a lower bill for heating and protect the planet at the same time.

Alexandra Dragoi

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