Converter operation flexibility and sizing (performance models)
Converters may be used in simulations to be run forward (input feedstock goes to output product) or backward (product demand is input from some downstream component to get required feedstock to achieve that demand). And their capacity may be defined as an input or calculated based on some requirement. This issue aims to begin the discussion around possible use cases for converters in their operation and sizing.
Currently, converters have an input size and are input their primary feedstock, secondary feedstocks may be assumed to be fully available. I'll be using an electrolyzer to highlight this example and what other options could be relevant for simulating the electrolyzer.
The electrolyzer has:
- primary feedstock (input): electricity
- secondary feedstock (input): water
- primary product (output): hydrogen
- secondary product (output): oxygen
In H2I simulations the electrolyzer is input an electricity profile (flow variable) and rated capacity (model parameter) and outputs the hydrogen profile (output flow variable) and the total electricity consumed (or a proxy variable for this such as efficiency in kWh/kg). I will refer to this case as "Primary feedstock input, limited primary feedstock".
- (the electrolyzer should also output water usage and could output oxygen production profile).
Sizing alternative case: It could also be the case that instead of the user providing the capacity, the user may want the electrolyzer sized to meet some hydrogen demand profile. This is similar to what's done in the hydrogen storage model, the hydrogen storage can be sized automatically to achieve some hydrogen demand profile given the hydrogen production of the electrolyzer (aka - it can be sized based on some requirement). OR hydrogen storage can have a set capacity (defined as an input), such that the capacity constrains what it can do with its operation.
For all the alternative operation cases (listed below), it's assumed that outputs are constrained by the system capacity and operational constraints of the converter. I.e., electricity input to the electrolyzer may exceed the rated electrolyzer capacity but that excess electricity won't be used. Or if hydrogen demand exceeds the rated hydrogen production rate of the electrolyzer system, the excess demand cannot be met. This means that whatever is input to the electrolyzer model (h2 demand or electricity or whatever) may not equivalent to the actual production or consumption of that variable.
Other operational cases (in simulation):
- H2 demand, infinite feedstock: input hydrogen demand profile. Outputs profile of estimated electricity required, water required, and actual hydrogen that could be produced (given capacity constraints).
- H2 demand, primary feedstock limited: input hydrogen demand profile and available electricity. Outputs profile of actual hydrogen that could be produced (given capacity constraints and electricity availability), profile of electricity that would be consumed (given capacity constraints and h2 demand), and water required.
- H2 demand, secondary feedstock limited: input hydrogen demand profile and available water. Outputs profile of actual hydrogen that could be produced (given capacity constraints and water availability), profile of water that would be consumed (given capacity constraints and h2 demand), and electricity profile required.
- H2 demand, limited primary and secondary feedstock: hydrogen demand profile, input electricity profile, available water. Outputs profile of hydrogen produced (given capacity constraints, hydrogen demand, electricity constraints, and water availability constraints), outputs electricity consumed (given capacity constraints, water availability constraints, and h2 demand), and water consumed (given capacity constraints, electricity constraints, water availability constraints, and h2 demand).
- Primary feedstock input, limited secondary feedstock: input electricity profile and available water. Outputs profile of hydrogen produced (given capacity constraints, electricity constraints, and water availability constraints), outputs electricity consumed (given capacity constraints and water availability constraints), and water consumed (given capacity constraints, electricity constraints, and water availability constraints).
Proposed solution
To address all these operation options, the possible input profiles to the converter could be: hydrogen_demand, electricity_available, water_available and the outputs would be hydrogen_produced, electricity_consumed, water_consumed
Or, more generally: converter inputs could be primary_product_demand, primary_feedstock_availability, secondary_feedstock_availability, and the outputs could be primary_product_produced, primary_feedstock_consumed, secondary_feedstock_consumed.
This would require converters (and any of their internal controllers) to be able to handle each of the above cases, which can get tricky for nonlinear systems with complex dynamics. But - for converters that are primarily defined by an input/output ratio (like kWh/kg) and have simple dynamics - then these options can be simple to code up in functions but difficult to handle or integrate into the existing architecture and could be confusing to users (like - why would hydrogen ever be input to an electrolyzer - that's weird!)
Alternatives considered
Split converters into multiple performance models depending on whether the user wants to input the product demand profile or the input feedstock variable. This could get tricky in financial models and could result in converters being double counted in cost calculations.
Additional context
Converter operation flexibility and sizing (performance models)
Converters may be used in simulations to be run forward (input feedstock goes to output product) or backward (product demand is input from some downstream component to get required feedstock to achieve that demand). And their capacity may be defined as an input or calculated based on some requirement. This issue aims to begin the discussion around possible use cases for converters in their operation and sizing.
Currently, converters have an input size and are input their primary feedstock, secondary feedstocks may be assumed to be fully available. I'll be using an electrolyzer to highlight this example and what other options could be relevant for simulating the electrolyzer.
The electrolyzer has:
In H2I simulations the electrolyzer is input an electricity profile (flow variable) and rated capacity (model parameter) and outputs the hydrogen profile (output flow variable) and the total electricity consumed (or a proxy variable for this such as efficiency in kWh/kg). I will refer to this case as "Primary feedstock input, limited primary feedstock".
Sizing alternative case: It could also be the case that instead of the user providing the capacity, the user may want the electrolyzer sized to meet some hydrogen demand profile. This is similar to what's done in the hydrogen storage model, the hydrogen storage can be sized automatically to achieve some hydrogen demand profile given the hydrogen production of the electrolyzer (aka - it can be sized based on some requirement). OR hydrogen storage can have a set capacity (defined as an input), such that the capacity constrains what it can do with its operation.
For all the alternative operation cases (listed below), it's assumed that outputs are constrained by the system capacity and operational constraints of the converter. I.e., electricity input to the electrolyzer may exceed the rated electrolyzer capacity but that excess electricity won't be used. Or if hydrogen demand exceeds the rated hydrogen production rate of the electrolyzer system, the excess demand cannot be met. This means that whatever is input to the electrolyzer model (h2 demand or electricity or whatever) may not equivalent to the actual production or consumption of that variable.
Other operational cases (in simulation):
Proposed solution
To address all these operation options, the possible input profiles to the converter could be:
hydrogen_demand,electricity_available,water_availableand the outputs would behydrogen_produced,electricity_consumed,water_consumedOr, more generally: converter inputs could be
primary_product_demand,primary_feedstock_availability,secondary_feedstock_availability, and the outputs could beprimary_product_produced,primary_feedstock_consumed,secondary_feedstock_consumed.This would require converters (and any of their internal controllers) to be able to handle each of the above cases, which can get tricky for nonlinear systems with complex dynamics. But - for converters that are primarily defined by an input/output ratio (like kWh/kg) and have simple dynamics - then these options can be simple to code up in functions but difficult to handle or integrate into the existing architecture and could be confusing to users (like - why would hydrogen ever be input to an electrolyzer - that's weird!)
Alternatives considered
Split converters into multiple performance models depending on whether the user wants to input the product demand profile or the input feedstock variable. This could get tricky in financial models and could result in converters being double counted in cost calculations.
Additional context