hydro_res.jl treats Eff_Down inconsistently.

[AshwinSandeep1]

I think RHS should be multiplied by Eff_Down

[cfe316]

Hi Ashwin,

Thank you for your careful reading of the code! It would be great if you could explain why Eff_Down is needed here. It would also be very helpful to provide a 'minimal working example' or even an example time series that shows why this is needed or gives an example of erroneous output without this. As a general principal it's also helpful to quote the surrounding code, so that readers can get some context. You can use Github Markdown to insert code blocks.

	### Constraints commmon to all reservoir hydro (y in set HYDRO_RES) ###
	@constraints(EP, begin
	### NOTE: time coupling constraints in this block do not apply to first hour in each sample period;
		# Energy stored in reservoir at end of each other hour is equal to energy at end of prior hour less generation and spill and + inflows in the current hour
		# The ["pP_Max"][y,t] term here refers to inflows as a fraction of peak discharge power capacity.
		# DEV NOTE: Last inputs["pP_Max"][y,t] term above is inflows; currently part of capacity factors inputs in Generators_variability.csv but should be moved to its own Hydro_inflows.csv input in future.

		# Constraints for reservoir hydro
		cHydroReservoir[y in HYDRO_RES, t in 1:T], EP[:vS_HYDRO][y,t] == (EP[:vS_HYDRO][y, hoursbefore(p,t,1)]
				- (1/dfGen[y,:Eff_Down]*EP[:vP][y,t]) - vSPILL[y,t] + inputs["pP_Max"][y,t]*EP[:eTotalCap][y])

		# Maximum ramp up and down
        cRampUp[y in HYDRO_RES, t in 1:T], EP[:vP][y,t] + regulation_term[y,t] + reserves_term[y,t] - EP[:vP][y, hoursbefore(p,t,1)] <= dfGen[y,:Ramp_Up_Percentage]*EP[:eTotalCap][y]
        cRampDown[y in HYDRO_RES, t in 1:T], EP[:vP][y, hoursbefore(p,t,1)] - EP[:vP][y,t] - regulation_term[y,t] + reserves_term[y, hoursbefore(p,t,1)] <= dfGen[y,:Ramp_Dn_Percentage]*EP[:eTotalCap][y]
		# Minimum streamflow running requirements (power generation and spills must be >= min value) in all hours
		cHydroMinFlow[y in HYDRO_RES, t in 1:T], EP[:vP][y,t] + EP[:vSPILL][y,t] >= dfGen[y,:Min_Power]*EP[:eTotalCap][y]
		# DEV NOTE: When creating new hydro inputs, should rename Min_Power with Min_flow or similar for clarity since this includes spilled water as well

		# Maximum discharging rate must be less than power rating OR available stored energy at start of hour, whichever is less
		# DEV NOTE: We do not currently account for hydro power plant outages - leave it for later to figure out if we should.
		# DEV NOTE (CONTD): If we defin pPMax as hourly availability of the plant and define inflows as a separate parameter, then notation will be consistent with its use for other resources
		cHydroMaxPower[y in HYDRO_RES, t in 1:T], EP[:vP][y,t] <= EP[:eTotalCap][y]
		cHydroMaxOutflow[y in HYDRO_RES, t in 1:T], EP[:vP][y,t] <= EP[:vS_HYDRO][y, hoursbefore(p,t,1)]
	end)

I think you have a point regarding the need for Eff_Down here in the cHydroMaxOutflow constraint for consistency with the cHydroReservoir constraint. Should it also be in cHydroMinFlow for consistency?

[AshwinSandeep1]

Hi Jacob

Thank you for your response.

1. Adding Eff_Down to cHydroMaxOutFlow makes it consistent with cHydroReservoir as you suggested. It also makes it consistent with the analogous constraint defined for storage technologies (Line 93 in storage_all.jl).
2. Eff_Down is not needed for cHydroMinFlow since (as the way I understand it), efficiencies need to be included only when referencing energies to convert the actual energy produced by the resource to the energy received by the grid.

[cfe316]

Ok. These values vP, vS_HYDRO, and vSPILL need to be made consistent.