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# Cogeneration unit not turning on in E

### Problem

I'm trying use a micro turbine cogeneration unit in E+ to track the service hot water loop in my building, but I cannot get it to turn on.

### What I've tried doing

I've basically started by copying some objects from the E+ example HeatRecoveryPlantLoop.idf, namely the Capstone C65 Generator:MicroTurbine and all associated curves, as well as the ElectricLoadCenter:Generators and ElectricLoadCenter:Distribution

!-   ===========  ALL OBJECTS IN CLASS: ELECTRICLOADCENTER:GENERATORS ===========

Capstone C65 Generator,  !- Name
Capstone C65,            !- Generator 1 Name
Generator:MicroTurbine,  !- Generator 1 Object Type
65000,                   !- Generator 1 Rated Electric Power Output {W}
Always On Discrete,      !- Generator 1 Availability Schedule Name
;                        !- Generator 1 Rated Thermal to Electrical Power Ratio

!-   ===========  ALL OBJECTS IN CLASS: ELECTRICLOADCENTER:DISTRIBUTION ===========

Capstone ELCD,           !- Name
Capstone C65 Generator,  !- Generator List Name
FollowThermal,           !- Generator Operation Scheme Type
0,                       !- Demand Limit Scheme Purchased Electric Demand Limit {W}
,                        !- Track Schedule Name Scheme Schedule Name
,                        !- Track Meter Scheme Meter Name
AlternatingCurrent;      !- Electrical Buss Type


Then I've created a PlantLoop as follows:

• Supply side: a pump, and three branches in parallel with one WaterHeater:Mixed, one Generator:MicroTurbine and one bypass
• Demand side: a WaterUse:Connections object and a bypass

I've put the Generator:MicroTurbine on the supply side of the PlantLoop according to the I/O reference guide for ElectricLoadCenter:Distribution that says:

The FollowThermal and FollowThermalLimitElectrical schemes are for heat following cogeneration and run the generators to meet the thermal demand. [...] For these schemes, the generator needs to be connected to the supply side of a plant loop and components that request hot water need to be on the demand side of the plant loop.

I've verified that there is a demand on the demand side of my plant loop.

I've added the Generator:MicroTurbineas first in line for the plant equipment operation scheme.

I've tried switching the Generator:MicroTurbine Heat Recovery Water Flow Operating Mode between PlantControl and InternalControl.

I've also hard-sized my loop pump - and made it variable speed - to make sure it's enough to provide the maximum heat recovery water flow rate of the cogen unit as I initially noticed it was autosized to a value below the minimum heat recovery water flow rate of the cogen unit.

I've also tried to remove the WaterHeater:Mixed.

None of the above have managed to get the Generator to come online.

Any ideas?

### Update

Here is the IDF File

edit retag close merge delete

This is a 'meta', but EnergyPlus appears as E in the title although it appears as EnergyPlus when I try to edit.

( 2015-11-03 10:19:42 -0500 )edit

Yes, not the first time I've seen this, title not updating...

( 2015-11-03 10:33:20 -0500 )edit

@Julien Marrec I am also trying to do the exact same thing with OpenStudio (modeling a building powered by gas CHP) and I used Capstone C65, these are screenshots of my HVAC
Plant Loop 1Plant Loop 2AirLoop But I am not that sure about it; eventhough it ran successfully, I still have some doubts, because I didn't find where I could specify that chp uses gas as fuel type, so the results are probably wrong..

( 2018-08-28 06:15:07 -0500 )edit

I also posted a question about that here

( 2018-09-06 11:00:18 -0500 )edit

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So I was using the default Capstone C65 Generator:MicroTurbine from the example file called HeatRecoveryPlantLoop.idf.

The problem is that in the ElectricLoadCenter:Generators list, there is no 'Rated Thermal to Electrical Power Ratio' specified for the Capstone C65 unit. This example file uses Baseload as an operation scheme, while I was trying to use FollowThermal

Once I specified the Rated Thermal to Electrical Power Ratio, the generator suddenly came online.

The Input/Output reference actually has it written black and white, but it's easy to overlook.

In ElectricLoadCenter:Generators, field Generator <x> Rated Thermal to Electrical Power Ratio:

This numeric field contains the ratio of the rated thermal output to the rated electric output. It is only needed and used if the operation scheme is set to FollowThermal or FollowThermalLimitElectrical. This nominal ratio is only used for control and dispatch decisions. This value should be generally consistent with the more detailed performance input for the individual generator component models but it is not used in those component models.

### In conclusion, if you want to use FollowThermal or FollowThermalLimitElectrical you MUST specify a Rated Thermal to Electrical Power Ratio.

!-   ===========  ALL OBJECTS IN CLASS: ELECTRICLOADCENTER:GENERATORS ===========

Capstone C65 Generator,  !- Name
Capstone C65,            !- Generator 1 Name
Generator:MicroTurbine,  !- Generator 1 Object Type
65000,                   !- Generator 1 Rated Electric Power Output {W}
Always On Discrete,      !- Generator 1 Availability Schedule Name
1.72;                    !- Generator 1 Rated Thermal to Electrical Power Ratio

more

That field is only needed for FollowThermal. It is used to turn a thermal load into an electrical load. The example file is using Baseload so it does not need it.

( 2015-11-03 08:30:16 -0500 )edit
2

New issue #5299 posted to throw an error if FollowThermal is specified but all of the generators in the list have zero Rated Thermal to Electrical Power Ratio.

( 2015-11-04 17:12:54 -0500 )edit

@Julien Marrec, could you please share with us IDF File after correction? Because I ran the IDF file you shared above after adding 1.72; !- Generator 1 Rated Thermal to Electrical Power Ratio but it fails and I get erros.

( 2018-09-14 10:21:31 -0500 )edit

I suspect the water heater Use Side in parallel is the problem. It will get the flow instead of the CHP. Report out time series results for System Node Mass Flow Rate on the supply branches to diagnose where the flow is going. The water heater is really sort of passive and does not get dispatched by the plant operation schemes.

I suggest looking at the example file called MicroCogeneration.idf. The topology that works better for this application is to connect the CHP to the Source Side of the water tank with a second plant loop. The CHP heats the water tank when the tank makes a request for indirect heating and if it can't keep up the water tank's heater picks up the remaining load.

more

Like I said, I also tried to remove the WaterHeater:Mixed, didn't change anything. And I've been actually looking at MicroCogeneration.idf. I swapped the Senertech with the Capstone, same problem.

( 2015-11-03 05:49:15 -0500 )edit

I'll add the *idf file to my original question, maybe someone will find what I'm missing.

( 2015-11-03 06:02:12 -0500 )edit
1

Generator:MicroCHP might work better than Generator:MicroTurbine.

( 2015-11-03 07:40:27 -0500 )edit

I'm actually trying to use the Capstone C65 unit per se, and it's part of the example files and uses Generator:MicroTurbine and has all of the curves etc.

( 2015-11-03 07:48:34 -0500 )edit
2

oh I looked at the IDF and you are missing a value here

    !- Generator 1 Rated Thermal to Electrical Power Ratio

( 2015-11-03 08:26:13 -0500 )edit

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