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Harvesters

Harvesters in MESSY are viewed in 2 different categories, batteries and sources. Batteries are more complex and contain by default AMS level simulation, while sources are defined in a simpler way.

Currently the power scheduling tries to use all the power generated by the sources to contain the system load and eccesses are handled uniformly by the batteries.

In the future, this aspect could be analyzed more and bring more control over power scheduling algorithms,

Battery definition

A battery is defined through several parameters, following an example of a battery called panasonic_batt:

"panasonic_batt" : {
    "harvester_type":"battery",
    "tracing":{
        ...
    },
    "vref":3.8,
    "soc_init" : 100,
    "soc_end" : 0,
    "capacity":32,
    "self_discharge":{
        "resolution":{
            "unit":"SC_S",
            "mult":1
        },
        "value":0.001
    },
    "converter" : {
        ...
    }
}

The firs parameter is the harvester_type one, this has to be set to battery, then tracing can be set as well.

To continue a slate of battery related paramters are present, these are:

  • vref: reference voltage in Volts
  • soc_init: starting State of Charge of the battery
  • soc_end: battery State of Charge that should trigger the termination of the simulation
  • capacity: battery nominal capacity in mAh
  • self_discharge: object that represent the self dischargment of a battery, parametrized by a resolution object and a value, each resolution time the value will be discharged from the battery
  • converter: optionally MESSY allows harvesters to define a converter (better described in Converters)

Source definition

The sources are defined similarly, here an example:

"photovoltaic" : {
    "harvester_type" :"source",
    "vref" :{
        "input_file":"input_files/gmonths.txt",
        "lut":{
            "input_values":[250,500,750,1000],
            "voltage_values":[2.9367,3.0710,3.1334,3.1689]
        }
    },
    "iref":{
        "input_file":"input_files/gmonths.txt",
        "lut":{
            "input_values":[250,500,750,1000],
            "current_values":[13.4031,27.2251,41.8848,56.7245]
        }
    },
    "converter" : {
        ...
    }
}

The firs parameter is the harvester_type one, this has to be set to source, then tracing can be set as well as a converter.

The specific parameters regards the enhanced input values such as iref and vref, these input values can be set statically, or to simulate more precisely natural conditions, they can be retrieved from an input file and generated by a LUT.