Industrial solar heating is the integration of solar heat into industrial production processes is a challenge to both: the process engineer and the solar expert. Usually the thermal solar system will be only a part of the total process energy system and will supply only a fraction of the total energy demand. Existing heating system – based on steam or hot water from a boiler – don’t have to take care of temperature level too much. In general they are designed at much higher temperatures compared to what the processes need in order to keep temperature differences – and by that heat exchanger surfaces – small. Very often we can find steam temperatures at 150 to 180°C while the processes run below 100°C or even much lower. Applying solar heat, much more attention has to be paid to the temperature levels.

Another challenge in applying solar thermal energy to industrial production processes is the time dependency of the solar energy supply and the heat demand of the processes. Only very few production lines run at constant loads all over the day. Most processes in smaller companies run for one or two shifts per day and are batch processes by themselves. The question of how to deal with batch processes will be discussed in a later newsletter.

Direct process heating or feeding into existing heating system The easiest way of integrating solar thermal heat into industrial energy systems, is to supply it to the existing heating system In that case, the solar collector has to be operated at the same temperature level as the existing heating system, which will be above 100°C in general. The heat transfer medium should be water and not steam if possible. Such a set up is easy to install and to control, but the thermal efficiency will be low.