Glossary

Activity: The input/s or output/s of a process that are limited by its capacity. For example, a 500MW power station can output 500MW of electrical power, or a 50MW electrolyser consumes up to 50MW of electrical power to produce hydrogen. The Primary Activity Commodity specifies which output/s or input/s are linked to the process capacity.

Agent: A decision-making entity in the system. An Agent is responsible for serving a user-specified portion of a Commodity demand or Service Demand. Agents invest in and operate Assets to serve demands.

Agent Objective/s: One or more objectives that an Agent considers when deciding which technology to invest in to serve demand. Objectives can be economic, environmental, or others.

Asset: Once an Agent makes an investment, the related capacity of their chosen technology becomes an Asset that they own and operate. An Asset is an instance of a technology, it has a specific capacity, and a decommissioning year. A set of Assets exist in the base year sufficient to serve base year demands (i.e. a calibrated base year).

Base Year: The starting year of a model run. The base year is typically calibrated to known data, including technology stock and commodity consumption/production.

Calibration: The process of ensuring that the model represents the system being modelled in a historical base year.

Capacity: The maximum output (or input) of an Asset, as measured by units of the Primary Activity Commodity.

Capacity Factor: The percentage of maximum output (or input) that the Asset delivers over a specified time period. The time period could be a single time slice, a season, or a whole year.

Capital Cost: The overnight capital cost of a process, measured in units of the Primary Activity Commodity divided by CAP2ACT. CAP2ACT is a factor that converts 1 unit of capacity to maximum activity of the primary activity commodity per year. For example, if capacity is measured in GW and activity is measured in PJ, CAP2ACT for the process is 31.536 because 1 GW of capacity can produce 31.536 PJ energy output in a year.

Commodity: A substance (e.g. CO₂) or form of energy (e.g. electricity) that can be produced and/or consumed by technologies in the model. A Service Demand is a type of commodity that is defined at the end point of the system.

Commodity Cost: Represents a tax or other external cost on a commodity. Commodity costs can be applied to all commodity production (sum of output of all processes for that commodity), net production (sum of output and input for all processes), or all consumption (sum of input for all processes).

Decision Rule: The rule via which an Agent uses the Objective/s to decide between technology options to invest in. Examples include single objective, weighted sum between multiple objectives, or epsilon constraint where a secondary objective is considered if two options with similar primary objectives are identified.

Dispatch: The way in which Assets are operated to serve demand. MUSE 2.0 uses merit order dispatch, subject to capacity factor constraints that can be defined by the user.

End Year: The final year in the model time horizon.

Equivalent Annual Cost (EAC): An Agent objective, representing the cost of serving all or part of an Agent's demand for a year, considering the Asset's entire lifetime.

Fixed Operating Cost: The annual operating cost charged per unit of capacity.

Input Commodity/ies: The commodities that flow into a process.

Levelised Cost of X (LCOX): An Agent objective, representing the expected cost of 1 unit of output commodity X from a process over its lifetime under a specified discount rate.

Lifetime: The lifetime of a process, measured in years.

Milestone Years: A set of years in the model time horizon where outputs are recorded. For example, with a 2025 Base Year and Time Horizon to 2100, a user might choose to record outputs in 5-year steps.

Merit Order: A method of operating Assets when the cheapest is dispatched first, followed by the next most expensive, etc, until demand is served. Also called “unit commitment.”

Output Commodity/ies: The commodities that flow out of a process.

Primary Activity Commodity (PAC): The PACs specify which output/s are linked to the process capacity. The combined output of all PACs cannot exceed the Asset's capacity. A user can define which output/s are PACs. Most, but not all processes will have only one PAC.

Process/Technology: An available process that converts input commodities to output commodities. Processes have economic attributes of capital cost, fixed operating cost per unit capacity, non-fuel variable operating cost per unit activity, and technology risk discount rate. They have physical attributes of quantity and type of input and output commodities (which implicitly specify efficiency), capacity factor limits (by time slice, season and/or year), lifetime (years).

Region: A geographical area that is modelled. Regions primarily determine trade boundaries.

Season: A year is usually broken down into seasons in the model. For example, summer, winter, other.

Sector: Models are often broken down into sectors, each of which is associated with specific Service Demands or specific Commodity production. For example, the residential sector, the power sector, etc.

Service Demand: A Service Demand is a type of commodity that is consumed at the boundary of the modelled system. For example, tonne-kilometers of road freight, PJ of useful heat demand, etc.

Technology Discount Rate: The discount rate used to calculate any technology-specific agent economic objectives that require a discount rate. For example, Equivalent Annual Cost, Net Present Value, Levelised Cost of X, etc.

Time Horizon: The overall period modelled. For example, 2025–2100.

Time Period: Refers to a specific year in the time horizon.

Time Slice: The finest time period in the model. The maximum time slice length is 1 year (where a model does not represent seasons or within-day (diurnal) variation). A typical model will have several diurnal time slices, and several seasonal time slices.

Variable Operating Cost: The variable operating cost charged per unit of input or output of the Primary Activity Commodity of the process.