Solar thermal energy for industrial heat with ENESTRA
In Germany (compared to the tropics), solar thermal energy is only a partially viable solution for heating and hot water needs with a timely return on investment.
When talking about solar thermal energy for heating and hot water, one thing must be understood above all else: In Germany, we have a timing problem—we need the most heat in winter, but that is precisely when the sun provides the least.Solar radiation fluctuates greatly throughout the year.
Even though the annual total in Germany is not too bad – in 2024, the average global radiation was around 1,113 kWh per square meter – most of it occurs during the summer months. Typical figures: April to September around 845 kWh/m², October to March only around 237 kWh/m² – roughly a 3:1 ratio between summer and winter.
If you still want to cover a large proportion of your heating needs with solar energy, you quickly come up against the next hurdle: storage. Short-term storage (buffers) help with day-night fluctuations. But the real gap is between summer and winter. To transfer summer heat to winter, you would need very large seasonal storage systems and often more collector area and, if necessary, more expensive collectors. The additional investments are precisely the main reason why many solar thermal heating systems in single-family homes are only of limited economic appeal (due to long amortization periods).
In tropical regions, the logic is different. There, solar radiation is often more consistent throughout the year and there is usually less need for space heating—but there is a fairly constant demand for hot water (pools, hotels, washing processes, etc.). Solar thermal energy can therefore “deliver exactly when you need it” much more often without huge seasonal storage facilities.
It is important to add that this does not mean that solar thermal energy is “always nonsense” in Germany – each case must always be examined individually. It can be very useful for hot water and in certain applications – for example, in industry for process heat with constant and predictable heat requirements, and this applies to both Germany and tropical regions.