Documentation Index
Fetch the complete documentation index at: https://docs.transitionzero.org/llms.txt
Use this file to discover all available pages before exploring further.
Summary
An energy system model includes a set of ‘technologies’ – a broad term that encompasses all forms of energy infrastructure, including power plants, transmission lines, and storage systems.
Techno-economic inputs describe the characteristics of these technologies
Below is a representative list of technology groups and the specific technologies they include.
The full set of technologies available in Scenario Builder is detailed below.
Technology set
thermal
coal
coal-subcritical
coal-supercritical
coal-ultrasupercritical
coal-circulating-fluidized-bed
coal-integrated-gasification-combined-cycle
coal-unspecified
gas
gas-internal-combustion-combined-cycle
gas-combined-cycle
gas-turbine
gas-open-cycle-gas-turbine
gas-steam-turbine
gas-integrated-solar-combined-cycle
gas-allum-fetvedt-cycle
gas-unspecified
oil
petroleum-products-internal-combustion-engine
oil-unspecified
cofiring
gas-coal-cofiring
gas-oil-cofiring
coal-bio-cofiring
gas-bio-cofiring
cofiring-unspecified
gas-ammonia-cofiring
cogeneration
gas-cogeneration
coal-cogeneration
bio-cogeneration
cogeneration-unspecified
waste
thermal-unspecified
bioenergy
biomass
biogas
bioenergy-unspecified
storage
battery
utility-scale
domestic-scale
battery-unspecified
battery-energy-storage-system
carbon-capture-and-storage
coal-ccs
gas-ccs
ccs-unspecified
renewables
marine
wave
tidal
marine-unspecified
solar
solar-unspecified
solar-thermal
concentrated-solar-thermal
solar-thermal-unspecified
photovoltaic
concentrated-photovoltaic
photovoltaic-unspecified
wind
wind-nearshore-intertidal
wind-onshore
wind-offshore
wind-offshore-unspecified
wind-offshore-hard-mount
wind-offshore-floating
wind-unspecified
geothermal
geothermal-unspecified
geothermal-flash-steam
geothermal-flash-steam-unspecified
geothermal-flash-steam-single
geothermal-flash-steam-double
geothermal-flash-steam-triple
geothermal-dry-steam
geothermal-binary-cycle
enhanced-geothermal-system
low-carbon
nuclear
hydro-reservoir-storage
hydro-reservoir
hydro-reservoir-and-run-of-river
hydro-pumped-storage
hydro-pumped-storage-unspecified
hydro-reservoir-and-pumped-storage
hydro-run-of-river
ammonia
interconnection
transmission
Technology costs
Generator Capital Costs (CAPEX)
CAPEX refers to the upfront investment needed to build new energy infrastructure. These are one-time costs for purchasing and installing technologies. The costs applied here are overnight costs - they do not include the interest during construction. This could lead to an underestimation of capital costs, especially in cases with high upfront costs, construction times, and interest rates.
- Includes: equipment, engineering, procurement, construction (EPC), land, grid connection, permitting, environmental impact assessments.
- Units: typically expressed as currency per unit of capacity (e.g. $/kW for power plants and transmission, $/kWh for storage).
The default capital cost of battery energy storage is calculated as the sum of its power and energy components, following the NREL approach, using the following equation:
Total capital cost (USD/MW) = power component (USD/MW) + storage duration (hours) × energy component (USD/MWh)
The power and energy component costs are taken from national or regional technology catalogues, and a storage duration of 4 hours is assumed.
Operating expenditures (OPEX)
OPEX refers to the ongoing costs to operate and maintain energy infrastructure over its lifetime, after the initial CAPEX.
- Variable Operating costs: proportional to the amount of electricity generated or activity level
- Includes: fuel costs (though sometimes treated separately, Commodity (Fuel) Price section), consumables.
- Units: $/MWh of electricity generated.
- Fixed Operating costs: incurred regardless of energy production level, typically time-based
- Includes: salaries, insurance, routine maintenance, property taxes.
- Units: $/MW/year (or $/kW/year).
For the majority of countries or nodes, all costs are expressed in 2023 USD.
Data sourcing standards for technology costs are detailed below.
Data sourcing standards – technology costs
| Input Variable | Model Type | Gold Standard (‘Best in Class’) | Silver Standard (‘Good’) | Bronze Standard (‘Publishable’) |
|---|
| Technology costs - current (Generator Capital Cost, Fixed & Variable Operating Cost) | CE & UD | For deregulated or liberalised markets: Auction results. Analysis based on equipment manufacturers, project developers, country-specific studies. | National-level estimates from data owner or specific national reports. | IEA region-level data, or global averages, applied to the country/region. |
| Technology costs - future projections | CE | Detailed, country-specific cost projection studies incorporating learning curves, R&D impact, and local manufacturing potential. | IEA scenarios (e.g., WEO) or other reputable international projections. | Extrapolation of current costs or application of generic global learning rates. |
Efficiencies
Efficiencies are represented by Fuel Use Rate input, which is the amount of fuel energy input required to produce one unit of energy output. Expressed as a value representing the ratio of energy input to energy output. For example:
- A coal power plant with 40% efficiency has a Fuel Use Rate of 2.5 (meaning 2.5 units of fuel are needed to generate 1 unit of electricity).
- A CCGT gas plant with 60% efficiency has a Fuel Use Rate of 1.67 (meaning 1.67 units of fuel are needed to generate 1 unit of electricity).
- A battery with 85% round-trip efficiency has a Fuel Use Rate of 1.18 (meaning 1.18 units of energy input are needed to discharge 1 unit of energy).
In general: Fuel Use Rate = 1 / Efficiency.
Data sourcing standards for efficiencies are detailed below.
Data sourcing standards – efficiencies
| Input Variable | Model Type | Gold Standard (‘Best in Class’) | Silver Standard (‘Good’) | Bronze Standard (‘Publishable’) |
|---|
| Efficiency / Losses | CE & UD | Observed data by asset or specific technology from data owner, adjusted by age/retrofits. | Regional/country-level technology studies. | Global technology catalogues. |
Utilisation rates (Operational constraints)
Maximum Annual Utilisation defines the highest level at which a power plant can operate within a given period, constrained by technical capability, economic viability, or regulatory requirements. For example, if a scenario sets a maximum annual utilisation rate of 80%, the model will cap the plant’s total output to 80% of its theoretical maximum capacity annually.
Minimum Annual Utilisation defines the lowest operating level required for a power plant, determined by plant-specific or technology-specific operational requirements. For example, if a scenario sets a minimum annual utilisation rate of 30%, the model will ensure the plant operates at least 30% of its theoretical maximum capacity annually.
Minimum Hourly Utilisation is available only for dispatch scenarios, which sets the lowest required operating level at the hourly resolution.
Samples of constraining factors:
- Maintenance: Planned and unplanned maintenance reduces annual output and capacity availability.
- Resource availability: Some technologies (e.g., geothermal) face natural limitations on output potential.
- Regulatory constraints: Policy can mandate minimum or maximum operating hours to balance grid supply and emissions reduction.
- Technology specification: Inflexible technologies such as coal plants have minimum operating levels to avoid excessive ramp-up and ramp-down costs.
| Power Plant Type | Suggested Default Maximum Utilisation Rate | Reference |
|---|
| Nuclear | 91% | ‘Electricity Annual Technology Baseline (ATB) 2024: Technologies and Data Overview’, National Renewable Energy Laboratory (NREL), 2024 |
| Coal | 80% | ‘Electricity Annual Technology Baseline (ATB) 2024: Technologies and Data Overview’, National Renewable Energy Laboratory (NREL), 2024 |
| Natural Gas (CCGT) | 88% | ‘Electricity Annual Technology Baseline (ATB) 2024: Technologies and Data Overview’, National Renewable Energy Laboratory (NREL), 2024 |
| Natural Gas (OCGT) | 88% | ‘Electricity Annual Technology Baseline (ATB) 2024: Technologies and Data Overview’, National Renewable Energy Laboratory (NREL), 2024 |
| Biomass | 83% | ‘Electricity Annual Technology Baseline (ATB) 2024: Technologies and Data Overview’, National Renewable Energy Laboratory (NREL), 2024 |
| Geothermal | 90% | ‘Electricity Annual Technology Baseline (ATB) 2024: Technologies and Data Overview’, National Renewable Energy Laboratory (NREL), 2024 |
Operational life (Lifetime)
The expected number of years a technology can operate before needing replacement. This is a key input for investment decisions. Sourced similarly to technology costs. The following table consolidates the operational lifespan data for various power plant technologies as identified from the referenced sources.
| Power Plant Type | Operational Lifespan (Years) | Reference |
|---|
| Coal | 50 | ‘Mineral requirements for electricity generation’, 2021, World Nuclear Association (citing IEA) |
| Natural Gas (CCGT) | 30 | ‘Mineral requirements for electricity generation’, 2021, World Nuclear Association (citing IEA) |
| Natural Gas (OCGT) | 30 | ‘Mineral requirements for electricity generation’, 2021, World Nuclear Association (citing IEA) |
| Nuclear | 60 | ‘Mineral requirements for electricity generation’, 2021, World Nuclear Association (citing IEA) |
| Solar PV | 25 | ‘Mineral requirements for electricity generation’, 2021, World Nuclear Association (citing IEA) |
| Wind-Onshore | 25 | ‘Mineral requirements for electricity generation’, World Nuclear Association (citing IEA), 2021 |
| Wind-Offshore | 25 | ‘Mineral requirements for electricity generation’, World Nuclear Association (citing IEA), 2021 |
| Hydropower | 100 | ‘Hydropower Explained: Hydropower and the environment’, U.S. Energy Information Administration (EIA), 2023 |
| Geothermal | 30 | ‘FAQ (Geothermal Energy)’, Enel Green Power |
| Biomass | 25 | ‘Biomass CCS Study’, Global CCS Institute, 2015 |
Growth or Build Rates (Capacity addition constraints)
Maximum allowed increase in capacity for a given technology year on year. There are two growth rate constraints: Relative and Absolute Maximum Growth Rate.
Relative Maximum Growth Rate is defined as the maximum allowed annual percentage growth in the given technology’s capacity year on year, expressed as a decimal (e.g. 0.2 for 20%). The growth rate is applied to total capacity in the preceding year.
Absolute Maximum Growth Rate is expressed in absolute values. If used in conjunction with Relative Maximum Growth Rate, the model may build new capacity at this floor value, in addition to the product of the previous year’s total capacity and the Relative Maximum Growth Rate. This parameter can also act as a ‘seed’ value where no or minimal capacity exists for the technology to which a growth rate is applied. Expressed in absolute values.
Emission rate
The rate at which a technology emits pollutants, especially greenhouse gases (CO₂), per unit of energy produced or fuel consumed (e.g. tonnes CO₂/MWh or tonnes CO₂/TJ). Where available, this is derived from the technology’s emission factor and heat rate. Sources include IPCC guidelines, national emissions inventories, and specific studies. These rates are critical for calculating total emissions and assessing alignment with climate targets.
The following table summarizes the life-cycle GHG emission factors for various electricity generation technologies based on the IPCC AR6 WGIII.
| Technology | Median (gCO2eq/kWh) |
|---|
| Coal | 980 |
| Natural Gas (CCGT) | 490 |
| Natural Gas (OCGT) | 680 |
| Oil (Heavy Fuel Oil) | 740 |
Scenario Builder currently evaluates only CO₂ emissions and does not yet account for other regulated air pollutants such as NOₓ and SOₓ.
Data sourcing standards – emission factors
| Input Variable | Model Type | Gold Standard (‘Best in Class’) | Silver Standard (‘Good’) | Bronze Standard (‘Publishable’) |
|---|
| Emission rate (CO2) | CE & UD | Plant-specific or country-specific, fuel-specific, technology-specific data from official national reporting (e.g. EUTL). | Default factors from IPCC or reputable regional databases, differentiated by technology and fuel. | Global average IPCC default factors. |
Reserve Margin
A constraint that ensures the total available generation capacity exceeds the peak demand by a specified percentage. It represents a reliability requirement to maintain operational flexibility and hedge against unexpected outages or demand variations.
