What does the message “Energy demand not covered” mean?
It may be that the energy from solar collectors and auxiliary heating is not sufficient to meet the energy demand prescribed in the project. In these cases, the hot water or building temperatures deviate from the target values prescribed in the project. Polysun marks such installations in graphs and reports with the message “Energy demand not met”.
Possible causes and recommended system improvements:
- A shortage can result from too little energy being added to the system overall. The shortfall can be seen in the component results. If there is a shortage only in winter, the non-solar auxiliary heating should be increased, rarely the full coverage can be achieved again by increasing the collector area. In most cases, however, there is not too little energy in the system, which is why the following points must also be checked:
- It is possible that a poorly sized heat exchanger is blocking the heat flow (compare flows and temperatures upstream and downstream of external heat exchangers and check the surface of internal coil heat exchangers).
- Likewise, incorrectly set temperature sensors or faulty controller parameters in the control systems can be the cause of a shortfall.
- However, the most frequent cause of the “Energy demand not covered” message is directly caused by the hot water draw. It should be noted that in Polysun the hot water is tapped every hour. With long pipelines and large pipe cross-sections, only the water that has cooled down in the meantime reaches the consumer and not the hot water from the storage tank. This results in an energy deficit. This can be remedied by shortening the pipelines and reducing the pipe cross-section or by increasing the tapping quantity per hour.
