Thermal Energy Storage (TES) - large scale

The TES technology represents a large scale thermal energy Storage connected to the district heating network. It can be charged by all the technologies that are defined via the connections parameters in the input file. The thermal energy storage is modelled as a simple thermal battery. It has a given maximum capacity that can be set by the optimizer if optimization is activated. When charging and discharging, a fixed loss rate is applied. Furthermore, the storage loses energy at a constant rate. The heat stored in the TES is assumed to be useful heat that can be directly used in the district heating network.

Using the parameter force_asynchronous_prod_con, the optimizer can be forced to never charge and discharge the storage at the same time. This can be useful to prevent the energy system from disposing of thermal energy using the charging and discharging losses of the storage.

The initial charge of the storage is usually set to be optimized. Then, the constraint is that the initial and final storage level have to be equal. Alternatively, a fixed initial state of charge can be defined.

Attribute	Description	Standard value	Unit	Data type
deployment	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.	False	—	bool
force_asynchronous_prod_con	If set to ‘true’, the tes cannot be charged and discharged simultaneously	True	—	bool
eta_chg_dchg	Charging and discharging efficiency (fixed). Roundtrip-efficiency is calculated as eta_chg_dchg*eta_chg_dchg.	0.95	—	float
tes_gamma	Loss rate: fraction of heat lost to the environment during one timestep (e.g. 1 hour)	0.001	1/timestep	float
capacity_kWh	Storage capacity.	inf	kWh	float
force_cap_max		False		bool
chg_dchg_per_cap_max	Max. charge/discharge (kW) per storage cap (kWh) per timestep.	0.1	1/timestep	float
initial_charge	Initial charge of storage (fraction of total storage capacity)	0	—	float
optimized_initial_charge	If True, initial_charge is determined within the optimization s.t. the initial charge and the final charge are the same	True		bool
connections	Technologies connected to TES can be switched on (True) of off (False).		—	dict
connections: district_heating_network	If set to ‘true’, the district heating network is connected to TES. Technology must be deployed accordingly.	True	—	bool
connections: district_heat_import	If set to ‘true’, district_heat_import is connected to TES. Technology must be deployed accordingly.	True	—	bool
connections: chp_gt	If set to ‘true’, the CHP gas turbine is connected to TES. Technology must be deployed accordingly.	True	—	bool
connections: steam_turbine	If set to ‘true’, the steam turbine is connected to TES. Technology must be deployed accordingly.	True	—	bool
connections: waste_to_energy	If set to ‘true’, the waset-to-energy plant is connected to TES. Technology must be deployed accordingly.	True	—	bool
connections: oil_boiler_cp	If set to ‘true’, a centralised oil boiler is connected to TES. Technology must be deployed accordingly.	True	—	bool
connections: electric_heater_cp	If set to ‘true’, a centralised electric heater is connected to TES. Technology must be deployed accordingly.	True	—	bool
connections: wood_boiler_cp	If set to ‘true’, a centralised wood boiler is connected to TES. Technology must be deployed accordingly.	True	—	bool
connections: gas_boiler_cp	If set to ‘true’, a centralised gas boiler is connected to TES. Technology must be deployed accordingly.	True	—	bool
connections: heat_pump_cp	If set to ‘true’, a centralised heat pump is connected to TES. Technology must be deployed accordingly.	True	—	bool
connections: heat_pump_cp_lt	If set to ‘true’, a centralised heat pump converting low-temperature waste heat to high-temperature useful heat is connected to TES. Technology must be deployed accordingly.	True	—	bool
connections: waste_heat	If set to ‘true’, a waste heat source is connected to TES. Technology must be deployed accordingly.	True	—	bool
connections: biomass	If set to ‘true’, a biomass technologies are connected to TES. Technology must be deployed accordingly.	True	—	bool
co2_intensity	Carbon-dioxide intensity of technology output (annual average value).	0	kg CO2/kWh	float
lifetime	Expected lifetime of technology before replacement is required.	25	years	int
capex	CAPEX of TES per kWh capacity	1.67	CHF/kWh	float
maintenance_cost	OPEX of TES per kWh capacity and year	0	CHF/kWh/year	float
interest_rate	Interest rate for computing levelised costs (if required).	0.025	—	float

The symbols and names of the flows are