Update green gas mapping

[mabijkerk]

The current mapping of green gas presents a number of problems. This becomes especially clear for Cyprus, which has no Natural gas demands in the Eurostat energy balance, only Biogases.

Issues

• Hardcoded loss: the Dataset Manager specifies green gas demand, but the energy balance only gives Biogases demand. In the ETM there is an energy_greengas_upgrade_biogas node that turns biogas into green gas. The demand from the Dataset Manager is however set in the energy_distribution_greengas node, which means that the loss of the upgrade node already has to be included in the value presented for green gas in the Dataset Manager. Currently, this is done hardcoded in the energy_energy_demand interface element on ETLocal. This means that changes on ETSource would not be reflected dynamically on ETLocal (see also Add documentation structure for hard-coded values #417)

  - header: energy_mix_gas_network
    items:
      - key: energy_distribution_greengas_demand
        unit: 'TJ'
        entso: |
          0.995 * (EB("Total energy supply", "Biogases") -
          EB("Transformation input - electricity and heat generation - autoproducer combined heat and power - energy use", "Biogases") -
          EB("Transformation input - electricity and heat generation - main activity producer combined heat and power - energy use", "Biogases"))
      - key: energy_regasification_lng_energy_national_gas_network_natural_gas_demand
        unit: 'TJ'

• Artificial natural gas demand: the green gas is then fed into the gas network, where it is compared against the total network gas demand. The difference between the green gas input and the total network gas demand is allocated as natural gas demand. Some of this difference however only exists because of the loss in the upgrade node. For Cyprus this leads to a natural gas demand which is not specified on the energy balance.

• Error calculating natural gas shares: in the case that there is no natural gas demand, the ETM will not be able to calculate the split between LNG and natural gas on the network, since both incoming natural gas edges will have 0 demand. This was the case for Cyprus before the upgrade loss created artificial natural gas demand.

Solution
Based on the issues above, I would argue that a redesign of the mapping of green gas, natural gas, and LNG is in order. Further investigation is required to determine the best solution.

Notifying @marliekeverweij @Charlottevm

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