[BUG] Thermal storage loses no energy over the first interval (soc_initial has no standing-loss decay)

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Valutazione

Difficoltà
3/5
Tempo stimato
1-2 giorni
Idoneità per principianti
69/100
Tipo di issue
Bug
Chiarezza
Specificata chiaramente
Stato di attività
Attiva
Stack tecnologico
julia, python
Ambito
backend

Direzione di ricerca

Read edisgo/opf/eDisGo_OPF.jl/src/core/constraint.jl, starting with constraint_store_state_initial and comparing it with the inter-step constraint; check _build_heat_storage in edisgo/io/powermodels_io.py to confirm how p_loss is assigned. Update the initial heat-storage balance to include the matching interval decay, then verify the first-interval energy balance across the time steps listed in the issue.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

bug

Type: bug
Affects: edisgo/opf/eDisGo_OPF.jl/src/core/constraint.jl::constraint_store_state_initial
Found while: reviewing #717

Problem

The thermal storage loses no energy over its first interval, at any time resolution.

constraint_store_state_initial couples soc_initial to the state at t = 1:

function constraint_store_state_initial(pm::AbstractBFModelEdisgo, n::Int, i::Int,
                                       energy, charge_eff, discharge_eff,
                                       time_elapsed, kind, p_loss)
...
    elseif kind == "heat_storage"
        ...
        JuMP.@constraint(pm.model, hse - soc_initial == - time_elapsed * phs_1)  # Eq. (3.23)

There is no decay factor on soc_initial. p_loss is handed to the function and never
read — it appears in the signature and nowhere else in the body, for any of the three
kind branches.

The general inter-step constraint in the same file does apply it:

    JuMP.@constraint(pm.model, hse_2 - hse_1 * (1 - p_loss)^(1/24) == - time_elapsed*phs_2)

(with time_elapsed/24 in the exponent once #717 is merged).

Effect

p_loss is 4 % of the state of charge per day for sector == "individual_heating"
(edisgo/io/powermodels_io.py, _build_heat_storage). The first interval of every OPF
therefore keeps the storage's initial energy intact where every later interval decays
it.

The size of the error scales with the step length, because the missing decay is the one
belonging to that step:

time step missing decay on soc_initial
15 min 0.04 %
1 h 0.17 %
4 h 0.68 %
24 h 4.0 %

Small at fine resolutions, the full daily loss at a daily step. It also makes the first
interval inconsistent with all the others, which matters for anyone reconciling the
energy balance from opf_results.heat_storage_t — the identity
e[t+1] == e[t] * (1 - p_loss)^(time_elapsed/24) - time_elapsed * p[t+1] holds between
every pair of steps except the first.

Suggested fix

Apply the same decay to soc_initial that the inter-step constraint applies to
hse_1, i.e.

hse - soc_initial * (1 - p_loss)^(time_elapsed/24) == - time_elapsed * phs_1

and decide whether the battery (kind == "storage") needs the same treatment — it has
no loss term at all today, in either constraint, so p_loss is 0 for it by
construction (_build_heat_storage sets p_loss = 0 for anything that is not
individual heating) and this is consistent rather than missing. Worth confirming before
changing it.

Note

Out of scope for #717, which fixes the exponent of the inter-step decay and does not
touch the initial step.

Lingua principale
Python
Stelle
48
Fork
22
Merge medio
1g 8h
PR unite (30g)
37

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