Ware (?), as you can see, energy consumption and cost may be on very different scales. It is not logical to add them together to form an objective. If the cost numbers are much higher than the energy numbers, the combined objective will be dominated by the cost results, thus dictating the minimum collector area outcome. You have two options here, to use the life cycle cost alone as the objective (as the energy cost should have been factored in), or to switch to a multi-object approach. Jeff, optimisation should not be that hard. I would suggest trying out jEPlus+EA or other GA-based tools. In most cases you can throw in all your design variables and let the algorithms do the hard work. The problem with the tiered search strategy is that you are likely to narrow down the results prematurely (i.e. within the ballpark) and miss solutions elsewhere. The magic with optimisation is that it can give good solutions that you have never expected to exist. :-) Regards, Yi From: TRNSYS-users [mailto:trnsys-users-bounces@lists.onebuilding.org] On Behalf Of Free Dear Yi, Jeff, Marko Sincerely thank you for your answers! The PSO in GenOpt is a Single - objective algorithm,i have tried to set the object function as the sum of energy consumption in a year or the life circle cost of the system, and the result coincided with Jeff's reply exactly. I will try a parametric analysis for system to find the problem as well. Here is another question for Jeff: <We'll use the Hooke-Jeeves algorithm on the tank volume and array area to get us in the right ballpark (with slope = latitude and south facing collectors at standard flow rates)> I am eager to realize the object function and the criterion that you used for optimization，can you give me some suggestions for the unfavorable situation i struggled in? Sorry to bother you again. Ware BR |