Battery Energy Storage (BES)

This technology represent a battery electric energy storage device. It charges and discharges electric energy. It has the following properties, to be defined in the input file

Attribute	Unit	Data type	Description
deployment	–	bool	If set to ‘true’, the technology will be considered in the energy system model (this does not necessarily mean it will be used). Only relevant for optimisation.
force_asynchronous_prod_con	–	bool	If set to ‘true’, the tes cannot be charged and discharged simultaneously
eta_chg_dchg	–	float	Charging and discharging efficiency (fixed). Roundtrip-efficiency is calculated as eta_chg_dchg*eta_chg_dchg.
bes_gamma	1/timestep	float	Loss rate: fraction of electricity lost during one timestep (e.g. 1 hour)
capacity_kWh	kWh	float	Storage capacity.
chg_dchg_per_cap_max	1/timestep	float	Max. charge/discharge (kW) per storage cap (kWh) per timestep.
initial_charge	–	float	Initial charge of battery (fraction of total storage capacity)
optimized_initial_charge	–	bool
co2_intensity	kg CO2/kWh	float	Carbon-dioxide intensity of technology output (annual average value).
lifetime	years	int	Expected lifetime of technology before replacement is required.
interest_rate	–	float	Interest rate for computing levelised costs (if required).
capex	CHF/kWh		CAPEX cost of technology per unit of capacity.
maintenance_cost	CHF/kWh/year	float	OPEX of the technology

Name	Standard Value	Description
deployment	True	Defines whether this technology is deployed
force_asynchronous_prod_con	global variable	If True, charging and discharging at the same time is not possible
eta_chg_dchg	0.95	Efficiency of charging and discharging
bes_gamma	0.001	Storage losses
capacity_kWh	‘inf’
chg_dchg_per_cap_max	0.1	Maximum charge or discharge flow per time unit (per hour)
initial_charge	global variable	initial charge of the battery at t=0
optimized_initial_charge	True	If True, initial_charge is determined within the optimization s.t. the initial charge and the final charge are the same
co2_intensity	0	CO_2 intensity
lifetime	10	Lifetime of the battery, in years
interest_rate	global variable	interest rate for LCC calculation
capex	500	Capital expenditure per kWh
maintenance_cost	2.0	Yearly maintenance cost per kWh

The variables of the

Contained energy	q_e_bes
Charging power	u_e_bes
Discharging power	v_e_bes
Storage losses	l_q_e_bes
Charging losses	l_u_e_bes
Discharging losses	l_v_e_bes

The relationship between q_e_bes(t) and q_e_bes(t+1) is given by

\[\mathtt{q\_e\_bes}(t+1) = \mathtt{q\_e\_bes}(t) - \gamma \mathtt{q\_e\_bes}(t) + \eta \mathtt{u\_e\_bes}(t+1) - (1/\eta) \mathtt{v\_e\_bes}(t+1)\]

where we refer to bes_gamma as \(\gamma\) and to eta_chg_dchg as \(\eta\). Importantly, the charging and discharging powers are measured at the system connection, not directly at the storage. Therefore, the amount of energy charged into the storage is smaller than the charging power u_e_bes and the amount energy discharged from the storage is larger than v_e_bes, both by a factor eta_chg_dchg.

Importantly, the value given in q_e_bes is the stored energy at the end of a given time period.