Grid Performance and Cost Models

This page documents the unified grid_performance and grid_cost models, which together represent a flexible, configurable grid interconnection point within an H2I simulation. These components support both power flows and cost accounting for buying and selling electricity through a constrained interconnection. This is a single model that can be configured to either sell electricity to the grid, buy electricity from the grid, or both.

See example/24_solar_battery_grid to see how to set up both buying and selling grid components.

Grid Performance

grid_performance represents a grid interconnection point that can buy or sell electricity subject to a maximum throughput rating (interconnection_size).

It supports:

• Buying electricity from the grid to meet downstream demand.

• Selling electricity to the grid.

• Enforcing maximum allowed interconnection power.

• Computing unmet demand and unsold electricity due to constraints.

Note

Multiple grid instances may be used within the same plant to represent different interconnection nodes. For buying electricity from the grid, the technology name in the tech_config must start with grid_buy for the logic to work appropriately in financial calculations.

Inputs

Name	Shape	Units	Description
interconnection_size	scalar	kW	Maximum power capacity for grid connection.
electricity_in	array[n_timesteps]	kW	Electricity flowing into the grid (selling to grid).
electricity_demand	array[n_timesteps]	kW	Electricity demand from downstream technologies.

Outputs

Name	Shape	Units	Description
electricity_out	array[n_timesteps]	kW	Electricity flowing out of the grid (buying).
electricity_sold	array[n_timesteps]	kW	Electricity successfully sold to the grid.
electricity_unmet_demand	array[n_timesteps]	kW	Downstream technology demand not met due to interconnection limits.
electricity_excess	array[n_timesteps]	kW	Electricity that could not be sold due to limits.

Grid Cost

grid_cost computes all costs and revenues associated with the grid interconnection, including:

• Capital cost based on interconnection rating.

• Fixed annual O&M.

• Variable cost of electricity purchased.

• Revenue from electricity sold.

Inputs

Name	Shape	Units	Description
interconnection_size	scalar	kW	Interconnection capacity for cost calculation.
interconnection_capex_per_kw	scalar	$/kW	Capital cost per kW of interconnection.
interconnection_opex_per_kw	scalar	$/kW/year	Annual O&M cost per kW of interconnection.
fixed_interconnection_cost	scalar	$	One-time fixed cost regardless of size.
electricity_out	array[n_timesteps]	kW	Electricity flowing out of grid (buying from grid).
electricity_buy_price	scalar/array[n_timesteps]	$/kWh	Price to buy electricity from grid (optional, time-varying supported).
electricity_sold	array[n_timesteps]	kW	Electricity flowing into grid (selling to grid).
electricity_sell_price	scalar/array[n_timesteps]	$/kWh	Price to sell electricity to grid (optional, time-varying supported).

Outputs

Name	Description
CapEx	Total capital expenditure.
OpEx	Annual O&M cost.
VarOpEx	Variable operating expenses (buying), revenues (selling), or net of expenses and revenues (buying and selling).

The costs of purchasing electricity from the grid are represented as a variable operating expense (VarOpEx) and are represented as a positive value. This allows it to be tracked as an expense in the financial models.

The revenue of selling electricity to the grid is represented as a variable operating expense (VarOpEx) and a represented as a negative value. This is allows it to be tracked as a coproduct in the financial models.

Note

If you're using a price-maker financial model (e.g., calculating the LCOE) and selling all of the electricity to the grid, then the electricity_sell_price should most likely be set to 0. since you want to know the breakeven price of selling that electricity.