## 1. in the same capacity as `rb`, in which there are a set of `cb`
 ## constraints defining heat output. Here `allow_cb` would be disabled 
 ## on `False` and a string when used (i.e. `heat` in this case).  
 chp:
        name: 'Combined heat and power'
        color: '#FDC97D'
        stack_weight: 200
        parent: supply
        carrier: power
        constraints:
            r: inf
            e_eff: 0.4
            e_cap.max: 40000  # kW
            cb_allow: heat
            cb_eff: 0.6 # translates to a heat to power ratio of 0.6/0.4 = 1.5
            cb_dump: True # possible constraint to allow secondary carrier to be dumped if unwanted 
        costs:
            monetary:
                e_cap: 750  # USD per kW
                om_fuel: 0.02 # USD per kWh

## 2. `carrier_2` is defined in the line following `carrier`.
## In this case only one other constraint would be defined: the 
## percentage of `carrier_2` produced when `carrier` is produced (i.e. heat to power ratio).
 chp:
        name: 'Combined heat and power'
        color: '#FDC97D'
        stack_weight: 200
        parent: supply
        carrier: power
        carrier_2: heat
        constraints:
            r: inf
            e_eff: 0.4
            e_cap.max: 40000  # kW
            c_ratio: 1.5 # carrier ratio = heat to power ratio.
                         # forces 1.5kW heat to be produced for each 1kW power
        costs:
            monetary:
                e_cap: 750  # USD per kW
                om_fuel: 0.02 # USD per kWh

## 3. list arrays for certain YAML values, such that `carrier = power`
## becomes `carrier = [power, heat]` and subsequent constraints are
## dealt with in the same fashion or there is simply a heat to power
## ratio which is required when defining more than one carrier.
## This could allow an infinite number of carriers to be defined, 
## which *may* be useful. As a result, the heat to power ratio constraint
## (`htp`) could then also be a list, following the number of carriers defined.

 cchp:
        name: 'Combined heat and power'
        color: '#FDC97D'
        stack_weight: 200
        parent: supply
        carrier: [power, heat, cooling]
        constraints:
            r: inf
            e_eff: 0.4
            e_cap.max: 40000  # kW
            c_ratio: [1, 1, .5] # carrier ratio is now [power:power, heat:power, cooling:power],
                                # obviously the first is 1, but its existence ensures the same 
                                # list position for carrier and c_ratio elements.
            c_dump: [False, True, False] # possible constraint to allow secondary carriers to be dumped if unwanted 
        costs:
            monetary:
                e_cap: 750  # USD per kW
                om_fuel: 0.02 #file=fuel.csv # USD per kWh

## 4. Define a dummy technology which consumes no resources and
## has an additional constraint to force it to follow the output 
## of the primary carrier. This requires the least change in the 
## current code, but puts the onus on the user to understand how 
## to use the fix, and could be misused easier.

 gt:
        name: 'Gas turbine'
        color: '#FDC97D'
        stack_weight: 200
        parent: supply
        carrier: power
        constraints:
            r: inf
            e_eff: 0.4
            e_cap.max: 40000  # kW
        costs:
            monetary:
                e_cap: 750  # USD per kW
                om_fuel: 0.02 # USD per kWh

gt_heat:
        name: 'Gas turbine heat'
        color: '#FDC97D'
        stack_weight: 200
        parent: supply
        carrier: heat
        constraints:
            r: 0
            r_link: gt # links resource to the gas turbine
            c_ratio: 1.5 # carrier ratio = heat to power ratio.
        # note: there are no associated costs