What is the solar potential of your region? Here are 2 maps of France showing average sunshine reflecting the energy potential of solar energy.
Keywords: solar energies, photovoltaic, thermal, water heater, potential, France, region, kwh / year m2, m².
Here is a more detailed map: DNI solar map of France and some panels and solar photovoltaic products here
1) Average sunshine duration in hours per year.
Example: if you live in the Bas-Rhin (North of Alsace) you will have less than 1750 hours of sunshine per year.
2) average energy potential in thermal kwh per year per m2.
Example: if you live in Bas-Rhin (North Alsace) you will have less than 1220 kWh of recoverable energy per year.
3) Example with a concrete case: a thermal solar panel mounted in Alsace in the Lower Rhine.
As read on the cards, we have a year:
- less than 1750 hours of sunshine, let's take 1500 hours arbitrarily.
- less than 1220 kwh / m2 of energy, let's take 1100kwh arbitrarily.
b) Power demand by m2.
We therefore have an average solar power (when the sun is shining) of 1100/1500 = 733W. Which is very correct (the world average is given for 1000W per m2).
For information, the average power over the year calculated over half a day (over the 12 hours of “day”) would be 2 * 1100/8766 = 251W.
At these values to obtain the recoverable thermal energy, it is necessary to multiply by the efficiency of the solar panel (assuming that there are no other losses which is generally false) i.e. 70% for thermal and 10% for photovoltaics.
c) Recoverable Energy annually.
Each would bring m2 * 1100 0.7 770 = kWh.
We remind you that a liter of petroleum fuel has a calorific value of around 10 kWh. Assuming a boiler efficiency of 0.8, one m2 of panel will give the equivalent of 770 / (10 * 0.8) = 96,25L of fuel oil, or roughly, given the various estimates: 100L per m2 of panel.
Depending on your current fuel consumption, so you can estimate the number of m2 required to fully compensate your oil consumption.
d) Financial "analysis"
Thus, an Alsatian house that consumed 2500 L of fuel oil will be needed, ideally, 2500 / 100 = 25m2 of panels (that's a lot, the m2 installed costs on average, with tank and installation, around € 1000 currently, price excluding aid and subsidies) and will save per year the equivalent of 2500 * 0.65 = 1625 € of fuel oil (this is not much compared to the price of the 25m2 installation which must be located, in 2010 and excluding subsidies, between 15 and 20 €) ...
We noted ideally because the reality is precisely not so ideal. Indeed; in winter, solar thermal energy (due to the fairly low heating temperatures reached) can only be used to heat domestic hot water or to supplement the conventional heating circuit (before the boiler). To switch to 100% solar, you need a low-temperature heated floor (or walls).
This is why very few people use solar for heating: the vast majority of installations aim to heat only domestic hot water (which constitutes on average and about 10 to 15% of the annual energy consumption). ).
Conclusion: difficult profitability, attitudes to change ...
This brief calculation shows that the profitability of solar thermal is difficult to achieve for people (the vast majority of us) who do not understand that the financial calculation. Subsidies and various aids, as explained in a page of this site, do not change much… (on the contrary!)
This will be the case as long as the non-renewable nature of fossil fuels and their induced pollution are not taken into account in their costs or that ecological aspects take precedence over financial aspects during a purchase ...
The moral aspect (exactions of certain multinationals) should, ideally, also play in favor of the choice of non-fossil fuels ...
Isn't that the basis of an ecological society and no longer just oil and financial…