Solar Panel

The solar panel works during the day, but at night there is the greatest demand for energy. A group of scientists has managed to design a model so that solar panels can remain active, even without light, as they have published in a recent study. The plates not only absorb the heat they receive but also take advantage of the heat they radiate. 

Solar panel works during the day, without light, this alternative is no longer effective. 

For this reason, a group of scientists has wanted to find a solution to this problem, managing to design an installation that can be active, even after the sun’s rays have disappeared.  As they have revealed in a recent study, 2.2 watts of energy per square meter can be generated during sleep hours and, in addition, using existing technology. 

But how do these solar panels work in reverse? The infrastructure absorbs the heat that, not only during the day but also at the end. The plates radiate the energy from high temperatures and also take advantage of it, creating an output circuit and an input circuit.

This phenomenon is known as radiative cooling, which occurs when a body loses heat through thermal radiation. It is about hoarding that surplus, which the panels continue to detach, even at night. 

If this research materializes, this proposal could generate 120 times more energy, according to Science Alert .

“These results are significantly higher than those available up to now and lead us to a potential application that allows storing electrical energy at night”, the study collects.

In addition to radiative cooling, scientists use thermoelectric generators. They have already tested a model, which works with a specific program, which has been placed on a ceiling. With this system they  have managed to replicate their reverse solar panel design. 

“We are working to develop even higher yields. Sustainable light generation can provide everyone, even in rural areas, with access to cheaper and green energy sources,” the researchers conclude. 

They also hope that this discovery will have other applications and that the heat radiated by other structures or transport, such as cars, can also be used. 

For the moment, fossil fuels are still needed to supply energy demand, although this proposal may be scalable in the medium term.

Difference of thermal solar panels versus photovoltaic panels

Today in the market there are many solar panels, however there are two main types of solar panels, commonly called thermal solar panels , which are used to heat DHW and photovoltaic panels , which are used to produce electricity.

Thermal solar panels for ACS 

The thermal panels produce hot water through thermal energy, as its name suggests. There are two types:

  • Flat collector: it  has a series of tubes under glass inside the panel and they are the most common
  • Vacuum tube collector : they are a superior technology to the flat collector, they are made to minimize heat losses to the outside, so they have better performance and are more expensive.

The operation of this technology is simple, the thermal panels contain a liquid that heats up when exposed to the sun, then that liquid transfers its heat to the water in the house. The temperatures reached by the liquid inside this panel are higher than the ambient temperature where they are, therefore, we can get hot water even on the coldest days as long as there is a minimum of solar radiation.

 Photovoltaic panel

The photovoltaic panels absorb solar energy and transform it into electricity. It is a technological advance superior to that of thermal panels and is still in the process of improvement in both efficiency and performance.

All photovoltaic panels are built mainly with silicon crystals, a material that is responsible for absorbing photons of light, and then emitting electrons that help us get electricity.

There are different types of photovoltaic solar panels that we can basically summarize in 3. We present them to you in order of efficiency and cost, with monocrystalline ones being the most efficient and expensive:

Types of photovoltaic solar panels. Image: Solectric

  • Monocrystalline, they have a single crystal that has had a controlled growth. This causes the entire surface of the panel to go in the same direction, making it the most efficient photovoltaic system.  
  • Polycrystalline, crystal growth is not controlled and therefore its surface has all directions, making them less efficient than monocrystalline ones
  • With a thin layer, they are the most traditional panels and represent an efficiency between 7-13%, being 4 times lower than monocrystalline ones. They can be made of different materials: amorphous silicon, cadmium telluride, copper, and photovoltaic cells.

What are the differences of photovoltaic and thermal panels?

If it is still not clear with the definition of each one, we leave a table with their differences:

Thermal panels

  • They are a simpler technology
  • Captures thermal energy
  • Produces domestic hot water
  • Shelf life 10 years approx.
  • Average efficiency of 90% (very varied depending on time and type)

Photovoltaic panels

  • They are a more advanced technology
  • Capture solar energy
  • Produces electricity
  • Shelf life 20 years approx.
  • Efficiency between 10 – 15% (very varied depending on time and type)

Is there a combination between photovoltaic panels and thermal solar panels?

Yes, they are called hybrid panels. They produce electricity and heating both in a home and in a business.

At the end of it all, we are going to opt for a photovoltaic panel or thermal solar panel depending on what our greatest need is: heating or electricity. However, there are hybrid panels that do both.