The FlexVal project, part of the IEA DHC Annex XIV programme, investigates how flexibility measures can improve the cost‑effectiveness and decarbonisation of district heating (DH) systems. The study combines a systemic view (top‑down, bottom‑up and hybrid approaches) with detailed modelling and case‑studies across five work‑packages: (1) long‑term heat‑mix optimisation using the TIMES Gotland model, (2) operational flexibility in Nordic DH (Backbone model and a Kuopio case), (3) building‑level design and control for low‑temperature DH (Viborg case, heat‑cost‑allocator methodology, DHW substation concepts and business‑model analysis), (4) network‑design flexibility using VITO’s STORM controller and PathOpt topology optimiser (Menen case), and (5) joint synthesis of findings. Key insights include: • Flexibility measures (thermal energy storage, demand response, flexible heat supply, low‑temperature distribution) significantly shape long‑term system cost and technology mix, especially when coupled with pricing mechanisms such as capacity fees or motivation tariffs. • At the system level, added TES and DR modestly improve the wider European energy system but can markedly reduce operational costs and increase robustness for individual DH operators. • Building‑level actions—digital diagnostics, improved control, and advanced DHW substations—unlock low‑temperature operation without major retrofits, yet incentives and ownership structures are critical for adoption. • Designing networks with smart control assumptions (peak‑shaving) reduces over‑dimensioning and total cost of ownership, though unit energy cost may rise in low‑density areas. • Flexibility is highly context‑specific; early integration of flexibility into planning, appropriate regulatory frameworks, and tailored tariff designs are essential for large‑scale uptake. The report concludes with four overarching lessons: (i) building‑level measures are pivotal, (ii) flexibility is a systemic feature linked to the broader energy system, (iii) solutions must be adapted to local conditions, and (iv) anticipating future developments is crucial.
Topics
Systemic Flexibility Approaches: Top‑Down, Bottom‑Up and Integrated DH Planning
Introduces three conceptual frameworks – top‑down (supply‑centric), bottom‑up (demand‑centric) and systemic (combined) – that guide the FlexVal analysis of flexibility in district heating.
Long‑Term Heat‑Mix Modelling with TIMES Gotland – Scenario Impacts of Offshore Wind, Capacity Fees and Low‑Temperature DH
Presents the TIMES‑based modelling of Gotland’s DH system (2020‑2050), comparing offshore‑wind (OS) and no‑offshore‑wind (NOS) scenarios, the effect of a DH capacity‑fee tariff, and the introduction of low‑temperature DH (LTDH) with or without a cooling bonus.
Operational Flexibility in Nordic DH – TES, Demand Response and the Kuopio Case Study
Uses the Backbone energy‑system model to assess how adding thermal storage and demand‑response capacity influences operational costs and fuel mixes in a medium‑sized Finnish city, highlighting sensitivity to weather years and electricity price variations.
Building‑Level Low‑Temperature DH Design – Viborg Methodology and DHW Substation Innovations
Describes a data‑driven methodology (heat‑cost‑allocator and energy‑meter data) to lower supply‑temperature curves in multi‑apartment buildings, and evaluates after‑cooling and booster‑heat‑pump DHW substations together with business‑model (owner vs. utility) cost analyses.
Network‑Design Flexibility with STORM & PathOpt – Menen Peak‑Shaving Optimisation
Combines VITO’s STORM controller and PathOpt topology optimisation to design a district‑heating network that exploits peak‑shaving control, showing reductions in total cost of ownership and trade‑offs in unit energy cost for different demand‑reduction strategies.
FlexVal Project Scope and Systemic Approach
Introduces the project’s aim, the three analytical perspectives (top‑down, bottom‑up, systemic) and the consortium of VTT, IVL, DTU and VITO.
Long‑Term Heat‑Mix Optimisation with TIMES Gotland
Uses the TIMES model to explore scenarios (offshore wind, capacity‑fee, low‑temperature DH) for Gotland 2020‑2050, showing how TES utilisation, capacity fees and low‑temp distribution reshape the heat supply mix.
Operational Flexibility in Nordic DH – Backbone & Kuopio Case
Applies the Backbone energy‑system model and a city‑scale model of Kuopio to assess demand response and thermal storage impacts on costs, fuel mix and system robustness under different weather years.