battery.rst

Battery

The DISPATCHES Battery Model represents electricity energy storage with efficiencies for charge and discharge as well as capacity degradation with cycling. Electricity inflows and outflows determine the state-of-charge and energy throughput of the battery.

Degrees of Freedom

The Battery Model has X degrees of freedom.

Model Structure

The Battery Model uses the inlet and outlet electricity to determine how the stored energy and storage capacity of the battery changes from the user-defined initial conditions. The initial conditions consist of the initial_state_of_charge and initial_energy_throughput. A parameter, dt, is required to convert between electricity flows and stored energy. The degradation_rate describes how the storage capacity of the battery decreases with use, accounted for by energy_throughput.

Variables

The Battery Model uses the following variables:

Variable Name	Symbol	Notes
nameplate_power nameplate_energy charging_eta discharging_eta degradation_rate initial_state_of_charge initial_energy_throughput	P E ηc ηd d SOCinit ETinit
dt elec_in elec_out state_of_charge energy_throughput	Δt It Ot SOCt ETt	Used to convert power flows into energy holdup

Constraints

State of charge evolves with electricity in and out flows:

$$SOC_t = SOC_{init} + \eta_c \times \Delta t \times I_t - \frac{\Delta t \times O_t}{\eta_d}$$

Energy throughput is accumulated over time:

$$ET_t = ET_{init} + \Delta t \times \frac{I_t + O_t}{2}$$

Storage capacity is limited by degradation which increases with energy throughput:

SOC_t ≤ E − d × ET_t

Battery Class

dispatches.unit_models.battery

BatteryStorage