October 14, 2020
◼ Photovoltaic heat vs. solar thermal
90 percent less copper consumption than with thermal collectors and a price reduction of 65 percent in 5 years - photovoltaic heat is technically and economically on the advance.
Since 2015, my-PV has been conducting a current price comparison of heat from photovoltaics and solar thermal energy. For this purpose, a polycrystalline silicon module with 1.6 square meters on the one hand and a solar thermal flat plate collector with a surface of two square meters on the other hand are used. Both are industry standard dimensions. It is important to note, however, that photovoltaic modules have increased their output significantly in recent years and now have a standard of 330 Wp per 1.6 square meter in 2020.
The graph shows how prices have developed in recent years. Apart from a marginal reduction in 2019, the price for a flat plate collector has remained practically unchanged since 2015. This is due to raw materials such as copper and aluminium, which are still used in large quantities in production.
On the other hand, there has been a veritable collapse in the price of photovoltaics. In the last five years, there has been a price reduction of 65 percent with higher performance at the same time!
90 percent less copper
Compared to solar thermal energy, photovoltaics for hot water production offers enormous savings in resources. For the pipes alone, which are necessary for the transfer of energy from the roof to the hot water tank, photovoltaic heat offers savings of over 90 percent in the consumption of copper. A calculation example of this: If you take a standard 2.25 mm thin electrical cable (diameter without insulation) and compare this with a copper pipe with an internal diameter of 16 mm, the cross-sectional area of the cable is 4 mm², and that of the pipe 53 mm². In direct comparison, the consumption of copper for the cables is thus 93% lower for photovoltaic heat than for solar thermal energy.
The volume is calculated from the cross-sectional area x length. In this case, ergo the same factor applies because the same distance has to be covered - from the roof (solar thermal or PV) to the hot water storage tank. Therefore the ratio remains the same.
In addition, the installation costs and maintenance effort are reduced when using a photovoltaic system. In addition to the piping, pumps, valves, expansion tanks, antifreeze, etc. are no longer required. "Solar thermal systems were relatively complicated systems," remarks Dr. Gerhard Rimpler. "On top of that, photovoltaics can deliver considerable energy even in diffuse light and overcast skies".