Model 100% Efficient Battery and Calculate TDV

asked 2019-06-19 18:12:55 -0500

mldichter gravatar image

updated 2019-06-23 09:10:41 -0500

I'm trying to determine TDV savings from charging a battery at night and discharging between 5pm and 8pm. However, I am getting a worse TDV value when the model has the battery vs when I don't have the battery. The opposite of what I expected.

I suspect the inefficiencies of my battery explain this, but I wanted to check by modeling a 100% efficient battery to make sure I didn't do something wrong. I think I made the battery 100% efficient, but I'm still getting a worse TDV value with the battery. Can anyone spot something I did wrong? Or maybe another object I should check in the IDF file that I overlooked?

Okay, so then I thought that I could test if my battery simulation really is 100% efficient by making an enormous battery with a huge initial charge that could supply the entire building for a year, set the charge schedule to 0 all the time, and set the discharge schedule to 1 all the time. That gave me these TDV values:

                        Total Energy [GJ]   
Total Site Energy       553.57
Net Site Energy         -5753.6
Total Source Energy     9.13
Net Source Energy       -46417.4

This makes me think that I'm not interpreting these values correctly. I took my interpretation from this post, but that doesn't make sense with the large negative Net Source Energy value. I would think the Total Source Energy, which I think represents TDV, would be the large negative value.

So what's going on here. Should I add the numbers or something?

    Storage Inverter,        !- Name
    ,               !- Availability Schedule Name
    ,                        !- Zone Name
    0.00,                    !- Radiative Fraction
    14000,                   !- Rated Maximum Continuous Output Power {W}
    0.0,                   !- Night Tare Loss Power {W}
    368,                     !- Nominal Voltage Input {V}
    1,                   !- Efficiency at 10% Power and Nominal Voltage
    1,                   !- Efficiency at 20% Power and Nominal Voltage
    1,                   !- Efficiency at 30% Power and Nominal Voltage
    1,                   !- Efficiency at 50% Power and Nominal Voltage
    1,                   !- Efficiency at 75% Power and Nominal Voltage
    1;                   !- Efficiency at 100% Power and Nominal Voltage

    Battery,                 !- Name
    ,               !- Availability Schedule Name
    ,                        !- Zone Name
    0.0,                     !- Radiative Fraction for Zone Heat Gains
    1.0,                     !- Nominal Energetic Efficiency for Charging
    1.0,                     !- Nominal Discharging Energetic Efficiency
    1.0E12,                  !- Maximum Storage Capacity {J}
    200000,                  !- Maximum Power for Discharging {W}
    200000,                  !- Maximum Power for Charging {W}
    1.0E12;                  !- Initial State of Charge {J}

    Grid Battery Load Center,!- Name
    ,                        !- Generator List Name
    ,                        !- Generator Operation Scheme Type
    0,                       !- Generator Demand Limit Scheme Purchased Electric Demand Limit {W}
    ,                        !- Generator Track Schedule Name Scheme Schedule Name
    ,                        !- Generator Track Meter Scheme Meter Name
    DirectCurrentWithInverterDCStorage,  !- Electrical Buss Type
    Storage Inverter,        !- Inverter Name
    Battery,                 !- Electrical Storage Object Name
    ,                        !- Transformer Object Name
    TrackChargeDischargeSchedules,  !- Storage Operation Scheme
    ,                        !- Storage Control Track Meter Name
    Grid Charge Converter,   !- Storage Converter Object Name
    0.96,                    !- Maximum Storage State of Charge Fraction
    0.4,                     !- Minimum Storage State of Charge Fraction
    500000,                  !- Design Storage Control Charge Power {W}
    Charge ...
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