1  Introduction

The Danube Indeet Model (DIM) helps to design and evaluate future green energy systems. It answers practical questions such as:

The DIM automatically calculates the most cost-effective system design and operation based on the technologies you select and the data you provide.

The tool focuses on combined EV- and hydrogen-based energy hubs (e.g., chargers, electrolysers, hydrogen storage), but it also includes renewable electricity generation (PV), batteries, grid interaction, heat recovery, and water supply.

In addition to technical results, the DIM provides a full techno-economic evaluation, including:

The goal of the tool is to support informed investment and planning decisions.

1.1 What does “optimal size” mean?

An optimal size is the capacity of each system component that results in the lowest total cost while meeting all constraints.

Examples:

  • For a PV plant, the size is its installed peak power [kW\(_p\)].
  • For a battery, the size is its energy capacity [kWh].
  • For a hydrogen tank, the size is the amount of hydrogen it can store [kg].

The DIM determines the best size for each selected component. In some cases, the optimal size may be zero, meaning that the optimal solution does not include that component.

1.2 What is operational schedule?

An operation schedule describes how each component operates over time during the simulation period (typically one year).

For example:

  • An electrolyser may run at full capacity during hours of low electricity prices, and at partial capacity during high electricity prices.
  • EVs may charge with the maximum power during midday solar peaks and with partial power in the evening.
  • Hydrogen may be stored in summer and used in winter.

If the model uses hourly data, the operation schedule consists of 8,760 hourly values (24 hours × 365 days). This helps planners understand not only what to build, but also how the system should behave in practice.

1.3 What can the DIM model?

The tool can model integrated energy systems consisting of interacting technologies. It allows you to combine and evaluate:

Electricity generation and supply

  • Photovoltaic (PV) plants
  • Grid connection
  • Electricity supply
  • PPAs from renewable energy plants
  • Fixed electricity demand
  • Flexible electricity demand (EV chargers)

Storage

  • Battery energy storage systems (BESS)
  • Hydrogen storage tanks
  • Oxygen storage tanks

Hydrogen production and use

  • Electrolysers
  • Fuel cells
  • Hydrogen compressors
  • Hydrogen sales (market and gas grid injection)

Oxygen as a byproduct

  • Possibility of using oxygen from the electrolyzer or releasing it into the atmosphere
  • Oxygen compressors and tanks
  • Oxygen sales

Heat recovery and use

  • Waste heat from electrolysers and fuel cells
  • Heat exchangers
  • Local heat consumption

Water supply and treatment

  • Water grid
  • Rainwater
  • Demineralization and pumping systems

The tool evaluates all selected technologies together and determines the most economically efficient system configuration.

1.4 Basic workflow

The DIM is organized by projects and scenarios. Typical workflow:

  1. Create a new project (or open an existing one)
  2. Add a new scenario
  3. Select system components and enter their parameters
  4. Run the optimization
  5. Review and analyze the results
  6. Compare scenarios if needed

Scenarios allow you to compare different technology combinations, cost assumptions, or policy conditions.

1.5 How does the optimization work?

The DIM minimizes the total annual system cost.

Total cost includes:

  • Investment costs (CAPEX) Equipment purchase, construction, installation.
  • Maintenance and degradation costs Inspections, servicing, insurance, component replacement, etc.
  • Operational costs Electricity purchases, grid fees, water supply.
  • Revenue Selling electricity, hydrogen, oxygen, heat.

The tool simultaneously determines:

  • The optimal system structure
  • The optimal size of each component
  • The optimal hourly operation over the year

This ensures that investment and operation decisions are consistent.

1.6 Features

1.6.1 Investment and financial constraints

The user can:

  • Set a maximum total investment budget
  • Set a maximum acceptable payback period

The model ensures that solutions respect these limits. If the calculated payback period is shorter than the maximum allowed, it means the constraint was not binding and the project performs better than required.

1.6.2 Simulation settings

These settings allow balancing precision and computational effort.

  • The default simulation period is one full year.
  • The time resolution (e.g., hourly or daily) can be adjusted.
  • A shorter simulation period or larger time steps reduce calculation time but may slightly reduce accuracy.

1.6.3 Existing infrastructure

If certain components already exist at the site (e.g., grid connection, PV plant, storage), the tool can:

  • Keep the existing capacity
  • Optimize only the expansion
  • Optimize joint operation of existing and new components