Subject: Hydropower calculations Posted: 6/29/2016 Viewed: 11499 times
I'm new to WEAP and I'm trying to model a pretty big system in Brazil (the Paraiba do Sul river-basin). I've modeled reservoirs that should be generating energy. I've added as inputs: storage capacity, volume elevation curve, net evaporation, Max. turbine flow, Top of conservation and top of buffer. I've seen that: VolumeThroughTurbineH = Min( ReleaseH , MaxTurbineFlowH ). However, I'm not understanding how ReleaseH is modeled. Could someone please explain it to me?
I've looked into my results and there's only being energy generated when the reservoirs are at their total storage capacity! Does anyone know why this is happening?
Also, I want to add some restrictions. If I've understood, water is being thrown out because there isn't a spillage restriction. Could someone help me with that?
(obs: I've already tried to add operational restrictions, but for some reason I'm not succeeding on it, so if someone had a file with examples it would be very helpful!).
Reservoir release is calculated based on the needs of the system. Using the default values of WEAP, if you have demand sites downstream (or instream flow requirements), the reservoir will release enough water to supply the demand site, and otherwise it will try to hold back water so it can be full (or to the top of the conservation, if you've plugged that in). So if there is zero demand downstream, and there's still room in the dam, the volume through the turbine would be zero.
There are many ways to fix this. You can add hydropower priority and energy demand into your reservoir (under the hydropower button), to tell WEAP to prioritize water releases over water storage. You could also add in demands (or instream flow requirements) downstream to reflect the situation that drives water demand. It depends on your system, but I would recommend doing whatever is most realistic. Remember to calibrate - if you have historic volumes for the reservoir, you can plug them into Observed Volume (under the physical button).
I'm not sure what you mean by restrictions. Can you explain?
Thank you for your reply. I've added an energy demand and a high pririty to it. However, it is not working, since the energy demanded is not being generated (for example I've established a fizer 600,000 MWh of energy demand, and the reservoir is only producing 400,000 MWh).
By restrictions I mean constrains. Say, I have an operating rule that says that a specific amount of water should be released from a reservoir (for example the min(natural inflow from a reservoir, 150 cms)). How can I model this?
I thought I could add it in the expressão builder, but I'm not being able to do so.
You may not be able to produce 600,000 MWH of energy because there may not be enough water. Have you looked at the reservoir level?
The demands downstream are also determining how much water is released. And remember, that there is the demand priority for filling the reservoir (and supplying downstream/hydropower demands) and the hydropower priority, so you'll have to figure out how those need to interact.