2023-12-04 15:35:00
What is the solar energy potential in your area?
Two maps of France of average sunshine reflecting the energy potential of solar power. You will find a more detailed map here: DNI solar map of France
Keywords: solar energy, photovoltaic, sunshine, thermal, water heater, potential, France, region, kWh/year, m2, m²
Average duration of sunshine in hours per year in France: from <1750h à >2750 h !
Example: if you live in Bas-Rhin (Northern Alsace) you will have less than 1750 hours of sunshine per year.
Average energy potential in thermal kWh per year and per square meter: from 1220 kWh/m².year to more than 1760!
Examples of photovoltaic solar production in the North and South of France
If you live in Bas-Rhin (Northern Alsace) you will have less than 1220 kWh of recoverable solar energy per year and per m². If you are in the Montpellier region, you will have 1620 to 1760 kWh/m² each year. This is around 40% more than in Alsace or the North of France.
These are figures for the raw solar energy received at ground level.
To get theequivalent photovoltaic electrical energy produced, these raw solar energy figures must be divided by approximately 6 (taking into account the yields of the panels and the injection inverter). Thus in the Montpellier region, each m² of solar panel receiving 1700 kWh per year will produce approximately 1700/6 = 285 kWh of electricity per year. An installation of 10 panels of 1.6 m², or 16 m², will therefore produce 285 * 16 = approximately 4500 kWh.
The same installation in Bas-Rhin will produce at best 1220/6 * 16 = 3250 kWh per year. We find the 40% more by doing 4500/3250 = 1.38, which is close to the 40% more.
In order to take advantage of this solar potential, some companies offer to set up a photovoltaic shed
Detailed example: thermal solar production in Alsace, in Bas-Rhin
Solar power and energy data from maps
As read on the cards, we have per 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.
Average powers per m2
We therefore have an average solar power when the sun shines of 1100/1500 = 733 W. Which is very correct (the world average is given for 1000W per m2).
For information, the average power over the year, including nights, would be 1100/8762 = 125 W.
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 15% for photovoltaics.
Recoverable thermal energy per year
Each m2 would bring back 1100*0.7 = 770 thermal kWh per year.
We recall 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 speaking, taking into account the various estimates: 100L per m2 of panel.
Each m² of thermal solar panel therefore theoretically allows a energy saving of 100 L of fuel oil per year. Depending on your current fuel oil consumption, you can therefore estimate the number of m2 necessary to completely offset your oil consumption.
We specify in theory because in practice, heating needs are highest when the sun shines least: in winter! Must therefore store this solar thermal energy to benefit from it in winter (concept of production/consumption phase shift). Which is not necessarily an easy thing to set up.
Financial analysis of a solar thermal installation
Thus, an Alsatian house which consumed 2500 L of fuel oil will need, ideally2500/100=25m2 of panels (that’s a lot, the installed m2 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 quite little compared to the price of the 25m2 installation which must be located, in 2010 and excluding subsidies, between 15 and 20,000 €)…
We noted ideally because the reality is not so ideal. Indeed; in winter, solar thermal (due to the fairly low heating temperatures reached) only allows domestic hot water to be heated or to top up (before the boiler) the conventional heating circuit. To go 100% solar, you must have a low temperature heated floor (or walls).
This is why very few people use solar power for heating: the vast majority of installations aim to heat only domestic hot water (which constitutes on average approximately 10 to 15% of annual energy consumption). ).
Conclusion: profitability of solar thermal still difficult in Northern Europe
This brief calculation shows that the profitability of solar thermal is difficult to achieve for people (the vast majority of us) who do not think than by financial calculation. Subsidies and various aids, as explained in a page of this site, do not change much…(quite the contrary!)
This will be the case as long as the non-renewability of fossil fuels and their induced pollution are not taken into account in their costs or as long as ecological aspects come second to financial aspects when making a purchase…The moral aspect should, ideally, also play in favor of the choice of non-fossil energies…Is this not the basis of an eco-friendly society and no longer just a petroleum-financial one?
But in 2023, new installations of thermal solar panels have become anecdotal. The fall in prices (and the end of subsidies) on photovoltaic solar panels make photovoltaic solar panels widely competitive. It is therefore today more interesting to carry out a photovoltaic installation than a much more complex installation of thermal solar panels.
Global warming will also change solar radiation mapsand perhaps much faster than we think…to be continued!
Find out more about solar radiation in France
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