Guessing is Not an Option
Before detailed design can be done, many important planning steps have to be made:
Collecting basic information Rough dimensioning Cost estimate Simulation Design optimization
and only then...
Collecting Basic Information
Let us start today by talking about the first step: Initial object data input - or Collecting Basic Information.
You see - because of varying energy supply from the sun, we need to know precisely the volume of hot water consumption, the consumption profile and desired water temperature. By having fewer variables in equation the result could be more accurate. To have that information is critical because all further dimensioning tasks are based on it.
The values for DHW consumption data given in different literature have been found too high in practice; and result of their use is over-sizing of the solar system with all other consequences. Often these references are old, and have been calculated to cover highest possible demand factor.
Imagine - you are just breaking-even finishing the job and the customer is demanding to fix the overheating issues on warranty... - nice prospect, isn't it?
Another very important sizing criterion is the consumption profile.
Similar buildings/institutions can have absolutely different load profiles. For example: 100 room student dorm of the Faculty of Music and 100 room dorm of the department of Physical Education. In the second one the students are taking showers after the gym, outside the dorm.
Once again - the consumption volume and profile are so crucial in getting your design done right that you don't need to even think of "guesstimating" it, but measure it!
Read more: Designing Large-Scale Solar & Hydronic Systems