.. SPDX-FileCopyrightText: Contributors to GreenBubble .. SPDX-License-Identifier: CC-BY-4.0 .. _tutorial-2-brownfield: Tutorial 2 — Brownfield & Process Constraints ============================================== Building on :ref:`tutorial-1-greenfield`, this tutorial adds **existing assets** (*brownfield*) and introduces the **process constraints** that shape realistic dispatch: committable operation, ramping, and minimum load. We stay **price-driven**, drop hydrogen-to-grid (``demand_H2: 0``), fix a few plant sizes as pre-existing, and enable **district heating** as a heat off-take. .. contents:: On this page :local: :depth: 1 --- 1 · Greenfield vs brownfield ---------------------------- A technology's investment mode is set by three ``n_config`` keys: .. list-table:: :widths: 22 14 14 50 :header-rows: 1 * - initial capacity - expansion - rif - meaning * - 0 - true - 0 - **Greenfield** — built from scratch (Tutorial 1) * - >0 - false - 0 - **Brownfield, sunk** — fixed size, no capital charge * - >0 - false - >0 - **Brownfield, residual** — fixed size, *partial* capital charge * - >0 - true - any - **Mixed** — existing block + expandable new capacity ``rif`` = ``remaining_investment_fraction``: the share of the *original* investment still being paid off. The annual charge is .. math:: \text{rif} \times \text{investment}(\text{construction\_year}) \times \text{annuity}(r, \text{amortization\_period}). Because ``rif`` is set **per technology**, each existing asset carries its own residual cost independently. --- 2 · Run it ---------- .. code-block:: bash cp tutorials/2_brownfield/config.yaml config/config.yaml cp tutorials/2_brownfield/n_config.yaml config/n_config.yaml snakemake --cores 4 Existing assets (:download:`n_config.yaml <../tutorials/2_brownfield/n_config.yaml>`): .. code-block:: yaml biogas: {initial capacity: 30, expansion: false, construction_year: 2020, remaining_investment_fraction: 0.3} onwind: {initial capacity: 52, expansion: false, construction_year: 2020, remaining_investment_fraction: 0.5} solar: {initial capacity: 30, expansion: false, construction_year: 2020, remaining_investment_fraction: 0.5} options: DH: {enable: true, price: 30} # district heating off-take at 30 €/MWh The biogas plant (30 MW CH₄), wind (52 MW) and solar (30 MW) are now **fixed**; the optimiser sizes only the remaining expandable technologies (electrolyser, biomethanation, storage, …) around them. Each existing asset carries a different residual fraction: the biogas plant recovers 30 % of its original investment, wind and solar 50 %. --- 3 · Process constraints ----------------------- Three constraints make dispatch physically realistic. They are configured per technology in ``n_config``: * **Committable** (``committable: true``) — binary on/off unit commitment. Only valid for **fixed-size** components (``expansion: false``) or rolling horizon, because it turns the problem into a MILP. Leave ``false`` for expandable units. * **Ramp limits** (``ramp limit up`` / ``ramp limit down``) — max fractional change in output per hour (e.g. ``0.9`` = 90 %/h for the electrolyser). * **Minimum load** (``min load``) — fraction of capacity that must run when the unit is on (e.g. ``0.15`` for the electrolyser); below it the unit shuts off. The common result figures (capacities, operation, shadow prices, system cost) are described once in :ref:`guide-outputs` and read as in :ref:`tutorial-1-greenfield`; below we focus only on **what brownfield changes**. --- 4 · Interpret the results ------------------------- .. figure:: /_static/tutorials/tut2_Opt_capacities_SP_vs_WS.png :width: 95% Optimal capacities. The ``EXI_`` assets (biogas 62.85 t/h DM ≈ 30 MW CH₄, wind 52 MW, solar 30 MW) are fixed; everything else is sized around them. .. admonition:: The key change — biomethanation now competes :class: important - **Both biomethane routes are built**: biogas upgrading **22.9 MW** *and* biomethanation **11.1 MW** (vs Tutorial 1, where biomethanation never built). The reason is the **fixed, cheap existing renewables**: 52 MW wind + 30 MW solar power a 24.5 MW new electrolyser whose H₂ makes extra biomethanation CH₄ worthwhile at ``price_bioCH4 = 200 €/MWh``. The brownfield context is exactly where the upgrading-vs-biomethanation *competition* turns into a *mix*. - **District heating** adds value to waste heat: the DH bus shadow price clears at ≈ 25 €/MWh and biomethanation/heat-exchanger links export heat to it. - Net profit ≈ **€48.7 M/y** — the existing assets are largely sunk, so only their residual CAPEX is charged rather than a full greenfield investment. - Electrolyser CF ≈ 0.68, biomethanation CF ≈ 0.92 (running near-constantly wherever H₂ is available), upgrading CF ≈ 0.80. The process constraints shape *how* units run: the electrolyser ramps with cheap renewable hours (visible in the operation LDCs below), while upgrading acts as baseload because CO₂ supply is continuous. .. figure:: /_static/tutorials/tut2_CF_operation_by_scenario.png :width: 95% .. figure:: /_static/tutorials/tut2_shd_prices_mean_bar.png :width: 80% Energy-weighted mean shadow prices at internal carrier buses. Biomethane collection sits at ≈ 200 €/MWh (at its price target), H₂ collection ≈ 134 €/MWh, and heat buses at 23–25 €/MWh. --- What you learned ---------------- - Greenfield vs brownfield vs mixed, and independent **residual cost** per asset. - The **committable / ramping / min-load** process constraints and when each applies. - Adding a heat off-take (district heating) as a revenue stream. - Why brownfield context changes the biomethanation break-even. Next: :ref:`tutorial-3-rolling-horizon` re-dispatches this fixed plant hour-by-hour over the full year using rolling horizon, and :ref:`tutorial-2b-brownfield-heat` extends the brownfield plant with a larger electrolysis and heat-network integration. .. seealso:: :ref:`guide-outputs` · :ref:`config-economics` · :ref:`economics` · :ref:`tutorial-1-greenfield`