Photovoltaic thermal collectors or hybrid thermal panels are a combination of PV panels and thermal panels in one module. So, the typical structure of the panels includes an insulation layer on top with the solar cells below them and below the panels, the Heat accumulator absorbs the remaining solar energy, which is not converted into electrical energy, and transmits this energy to a hydronic coil where a heat transfer fluid is heated.
Difference between Solar panels vs PVT panels
Photovoltaic Cell is the heart of a solar module that produces Electricity by Solar Energy conversion. The electricity generated is DC (Direct Current) electricity which will be converted to AC (Alternating Current) allowing the electrical appliances in the property to be powered by solar energy.
More information on Photovoltaic cells/modules and their material structure and technology can be found in one of the previous articles “PHOTOVOLTAIC CELLS”,” WHAT PV MODULES ARE MADE OF?”.
Solar thermal panels:
Thermal panels contain fluid (usually a mix of water and antifreeze) that is heated by sun rays and this heat is used to heat the water in a stored cylinder. The main purposes of this technology are space and water heating, and they’re a very popular solution for swimming pool heating too.
Figure 1: Solar thermal collector
These two panels work in completely different ways and the outcome is also very different. One technology produces DC Electricity the other one produces heat. Combining these two technologies into a single hybrid system – solar photovoltaic thermal panel. A photovoltaic/thermal panel, or PVT panel, is a combination of photovoltaic cells with a solar thermal collector. The excess heat that is generated in the PV cells is removed and converted into useful thermal energy. As a result, PVT panels generate more solar energy per unit surface area than a combination of separate photovoltaic panels and solar thermal collectors. Moreover, PVT panels share the aesthetic advantage of PV. There are two different types of PVT systems. One is a PVT collector very similar in appearance to a regular solar thermal collector, consisting of a PV-covered absorber in an insulated collector box with a glass cover. The other one is a PVT panel. these are similar in appearance to regular PV panels. One difference is that there is a large amount of insulation in the former one which gives you high thermal efficiency at the cost of slightly lower electrical efficiency. The latter one has low thermal efficiency due to a lack of high insulation but has a relative construction which results in lower costs.
Figure 2 : (a) Solar thermal collector (b) PVT panel
Benefits of solar PV-T panels
There are many benefits to combining photovoltaic and thermal energy generation into a single hybrid system.
Electricity and hot water: It can be a source of electricity generation and also a source of hot water.
- Module cooling system:
Many factors affect the functioning of photovoltaic panels, including external factors and internal factors. One such factor is the PV panel temperature. Some of the radiation falling on the surface of the PV cell turns into electricity, while some of the incident radiation is absorbed inside the PV cell. This, in turn, increases its surface temperature. So, if there is a higher surface temperature there will be a drop in the efficiency of the solar panels and this means less reliability over the long term. With a solar thermal collector beneath the panels, the excess heat is removed from the PV module. The capture of both electricity and heat allows these devices to have higher exergy and thus be more overall energy efficient than solar PV or solar thermal alone.
- Low Maintenance:
In general, PV panels and thermal collectors are very low maintenance and the same goes for solar PV-T systems too.
In general, three market segments can be distinguished for the application of PVT panels: the residential market, the utility market, and the third one is mainly for industrial applications. Of these, the residential market is by far the most promising market for PVT. In residential buildings, both heat and electricity are required, and roof space is generally limited. The residential market for PVT panels extends over three existing market segments: the photovoltaic market, the solar thermal collector market, and a market for new low-energy system concepts. In all the markets, PVT panels have distinct advantages. Even with a small initial market share, the expected market potential for PVT panels is very large. There aren't as many solar PV-T panels available on the market as there are solar PV and solar thermal nevertheless there are companies that produce PVT panels. AE Solar’s Neptune module series produces more electrical yield compared to standard PV modules. These monocrystalline halves cut cells come with a power rating ranging from 370 W to 380W. Figure 3 shows electrical, mechanical, and thermal specifications for Neptune solar panels.
Figure 3 : AE PV-120 Series 370W-380W specification sheet.