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Self consumption

You can activate the Self-consumption calculation by defining a valid user's needs profile:

Self_Cons_Def

Context

For historical reasons, building-integrated grid-tied systems are connected independently from internal building electricity use.

They are directly connected to the grid through a dedicated electricity meter for PV production.

The reasons are:

  • for medium or big systems on collective building, the PV system owner has no relation with the building consumption.
  • with domestic systems, the Feed-in tariffs were very favourable to the PV production.

With the reduction (or disappearance) of feed-in tariffs, or even the drastic decrease in reinjected electricity prices, people increasingly find it advantageous to consume as much of their own PV production as possible. Optimizing self-consumption requires demand-side management (DSM) strategies, such as shifting some consumption (washing machines, cooling, water or space heating, etc.) to periods when solar electricity is available.

When the price of the injected electricity is equal to the price of the purchased electricity, these installations may simply involve one only counter, accounting the balance of electricity in both directions. This is named the "Net-metering" option.

Simulation process

The simulation has to evaluate:

  • E_Avail - The PV produced energy (output of the inverter, after eventual AC losses),
  • E_User - The energy needs (consumed by the user),
  • E_Grid - The excess energy injected into the grid,
  • EFrGrid - The energy drawn from the grid for the internal consumption (when PV is not sufficient), and during night.
  • E_Solar = E_User - EfrGrid - The PV energy internally consumed.
  • SolFrac = E_Solar / E_User - Ratio of the user's consumption covered by the solar production

Such an evaluation has to be performed at each simulation time step, as the energy exchanges are instantaneous. Therefore, this requires the definition of the User's needs profile as input parameter. In the project's dialog, the self-consumption will be activated as soon as you define a valid user's needs profile.

Now during the simulation, there are several running modes:

Self_Consumption

The resulting loss diagram shows the different contributions.

Self-consumption with storage

NB: The self-consumption may be enhanced by an internal storage. This is also treated in PVsyst now.