Hi,
I have modelled a borefield that consists of about 10 different pumps that deliver water to a treatment plant. The pumps each draw water from different bores where abstraction quotas and sensitivity limits (preference to draw from deeper bores) apply. Each of the pumps are also subjected to a few different electricity tariffs. It is also preferred that the pumps are started only once a day.
What is the best way or setup to find the most cost effective pump schedule using Darwin Scheduler given these constraints?
Hi Debbie,
The pump start constraint of 1 seems correct as does the energy pricing specific to pump site, so that’s two out of four issues taken care of.
Re: “To mimic the abstraction quotas that apply to the wells, I have represented the wells by tanks , where the tank volumes represent the quotas. I have also set up controls to make the pumps stop once the tanks are empty.”
I don’t think that the controls will work here since if you designate a pump to be a Scheduler decision, it will ignore controls and the pump’s status will be controlled by the optimization algorithm. I would make the tanks larger than required (in terms of vertical range) and then use tank level constraints in Scheduler to penalize the optimization when the levels go outside those ranges. So a tank minimum level constraint should prevent drawing down the well too much. This is likely the cause of the issues you are currently running into (the high fitness values).
Assuming I have understood your posts correctly, then there is one remaining issue.
1. You want to prefer the use of pumps that draw from deeper wells.
A surrogate for might be to artificially increase the tariffs for wells with more shallow wells, to make the deeper wells more favorable. That would in fact allow you to quantify how much money it's worth for you to prefer the deeper wells. There must be some point at which you would use the shallow wells, in terms of cost. This approach allows you to embody that requirement into the optimization in quantitative terms.
Kind Regards,
Wayne.
Answer Verified By: Debbie Chua
Re #1: You would want to adjust your tank definitions so the volume does not change within the expected control range of the tank. That is add additional "fake" volume below the tank, so that when Scheduler exceeds that limit (by drawing too much volume) then the tank is not closed off by the hydraulic simulation, but the cost penalty for breaching that lower limit is applied to the optimization. Re #2: The pump stopping will be controlled by Scheduler, so in that sense it will stop when the penalty accrued by drawing the well down too far is not effective in the optimization. If the lower level limit is not reached then it is simply not cost effective to fully draw down that particular well.
Please let me know if you need any additional clarification. Regards, Wayne