Energy storage in urban multi-energy systems

Prof. Marco Carlo Masoero

ICARB Workshop: Energy Storage for the Built Environment Edinburgh, 21st October 2014

Outline of the presentation Electrical Energy Storage (EES)

The role of EES

The technical parameters

Electric Energy Storage systems typology

Thermal Energy Storage (TES)

Purpose of TES in Energy Plants

Technologies

Short-term (daily) vs Long-term (seasonal) storage

Applications: District Heating and Cooling

Power-to-Fuels

Conclusions

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The role of Electric Energy Storage I

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Distributed generation development by renewables

More efficient use of HV and MV power grids

Smart Grid in support to Local Energy Communities

Higher flexibility to rapidly respond to variable load demand

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Generation Transmission Distribution End User

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Ancillary services:

Primary regulation f/P Secondary regulation Tertiary regulation Reactive power regulation Black-start Load rejection Remote disconnection service Load interruption

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The role of Electric Energy Storage II

Generation Transmission Distribution End User

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EES could represent a feasible solution to dealing with several aspects:

Secondary and tertiary regulation Over voltage Reverse power flows Resolution of congestions storage of energy in

excess at peak-hours

The role of Electric Energy Storage III

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EES could represent a feasible solution to dealing with several aspects:

Line capacity investment deferral: EES discharges at peak times and charges at off-peak times

Peak shaving long discharge/charge times Power quality short discharge/charge times Reduction of the resistive line losses Provision of ancillary services:

balancing energy Rotary reserve Substitutive reserve

frequency regulation • in normal power grid condition • in islanding working mode

The role of Electric Energy Storage IV

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EES could represent a feasible solution to dealing with several aspects:

control system and power quality improvement • Dip voltage and over/under-voltage • Frequency variations • Low power factor • Harmonic distortion

support service to voltage control • instead of capacitor banks, EES can compensate for

voltage drop provision of black-start services

• overall blackout

The role of Electric Energy Storage V

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Source: Eurelectric, Decentralised storage: impact on future distribution grids, 2012

The role of Electric Energy Storage VI

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Installed capacity (World)

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EES systems are defined by the following technical parameters: • Specific energy (kWh/kg) or energy density (kWh/m3) • Specific power (kW/kg) or power density (kW/m3) • Efficiency • Number of cycles • Useful life • Charge/discharge times (h) • Ramp rate (s) • Specific costs (€/kWh or €/kW) • Maturity

The technical parameters I

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Mainly the electrochemical EES are also defined by the following parameters: • Memory effect • Charge/discharge velocity • Depth of discharge • Self discharge

The technical parameters II

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Energy intensive: Availability to store large amounts of energy Power Intensive: Ability to deliver / absorb great amount of

power in short time

Source: EPRI, Electric Energy Storage Technology Options: A White Paper Primer on Applications, Costs, and Benefits, 2012

Energy and Power Intensity

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• Mechanical energy: • Pumped Hydroelectric Storage (PHS) • Compressed Air Energy Storage (CAES) • Flywheels

• Electromagnetic and electrostatic energy: • Electric Double Layer Capacitors - EDLC • Superconducting Magnetic Energy Storage – SMES

• Chemical energy (hydrogen vector): • Compression • Liquefaction • Chemi-sorption • Physi-sorption

• Thermal energy: • Molten salt • Liquefied Air Energy Storage (LAES) • Phase Change Materials

Electric Energy Storage systems typology

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Storage in potential energy

convenience: 𝑃𝑔𝑒𝑛

𝑃𝑝𝑢𝑚𝑝≥ 1.4

More than 99% of EES Difficulty of installation

Storage in compressed air Integration with thermal power

plants Difficulty of installation

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PHS

CAES

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Mechanical energy EES I

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Storage in kinetic energy Angular speed 60.000-100.000 rpm High energy density Rapid ramp rate High efficiency (90-95%) High self-discharge

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Flywheels

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Mechanical energy EES II

Chemical energy (H2 storage)

Compressed gas: 200-700 bar Liquid H2: -253 °C Chemi-sorption: Metal hydrides Physi-sorption Power to Gas: EC + H2 + FC

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Storage in electric field Specific energy: 1 ÷ 5 Wh/kg Specific power: 100 ÷ 2.000 W/kg High number of charge/discharge

cycles

Storage in magnetic field Superconductors between 4÷100 K Rapid ramp rate (20 ms) High specific power High efficiency (>97%)

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EDLC

SMES

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Electric energy EES I

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Li-ions: high specific power and efficiency

Lead Acid: high specific power, low energy density. Mature

Ni-Cd: high number of cycles. Environmental risk

ZEBRA: high specific power and efficiency. High temperature

Na/S: high number of cycles Ni-MH: high specific power, low

energy density Flux: Vanadium RedOx, Zn-Br

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Electrochemical batteries

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Electrochemical energy EES I

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Purpose of Thermal Energy Storage in Energy Plants

The use of thermal storage systems in energy plants can have multiple purposes: 1. Increase the stability in short term operation of the plants (e.g. load

variation in heat pump systems) 2. Reduce the use auxiliary boilers (e.g. in district heating) 3. Shift the heat production through CHP to periods where the electricity

production is more convenient (in the case of backpressure plants or internal combustion engines) or less convenient (in the case of extraction plants)

4. Increase the use of renewable primary resources (e.g. solar thermal systems)

All these have in common the decoupling between heat generation and utilization.

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Technologies

Water Tanks Phase Change Materials

TABS

Other (Ice Storage, Pebble Systems,…)

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Technologies: Water Tanks

DHW systems Solar Heaters

Daily Storage Systems

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Technologies: Water Tanks

Seasonal Storage Systems

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Technologies: Embedded Systems

In Thermally Activated Building Systems (TABS) the thermal capacity of the building is enhanced by the installation of water pipes within the slabs.

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Technologies: Embedded Systems Phase Change Materials (PCM) can be installed within structural elements of buildings (typically walls).

Their fusion temperature being around 25°C, their phase (liquid/solid) changes in a temperature range that is practical for normal building uses and allows to store/release thermal energy

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District Heating (DH) Networks

Total Heat Load results from the aggregation of multiple users

Need of adapting the heat demand side with the

heat supply side along the day

Need of operation optimization for different generation units (e.g. CHP, boilers, heat pumps, solar collectors)

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The role of Thermal Storage: Decoupling Supply and Demand

Supply Side Demand Side

DH systems have to match the user demand, as a result it is difficult to optimize CHP size and operation

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Current District Heating Network in Turin

As of 31-12-2012:

• largest DH system in Italy

• 53,4 Mm3 supplied buildings (88 Mm3 in future planning)

• 1.89 TWh heat supplied

• 467 km grid length

• 1.77 GW peak heat generation

• 1.14 GW of power (CHP)

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Current District Heating Network in Turin

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Current + Forecasted DH Network in Turin

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The role of Thermal Storage: Turin DH daily profiles

January

April

July

Daily peaks

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The role of Thermal Storage: Decoupling Supply and Demand

Turin Politecnico:

Re-Heating and Pumping

Plant with 2.500 m3 storage

North Turin:

Combined Cycle

Cogeneration Plant

with 5000 m3 storage

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Heat storage systems behaviour

Storage

Unload

Storage

Load

Heat storage systems

CHP units

Boilers

DH system of Turin

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Heat storage systems behaviour

Heat Storage Systems CHP Units Boilers

The heat storage allows to increase

the utilization factor of CHP units

DH system of Turin

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Biomass DH System Configurations

CHP Boilers + Boilers only

Heat storage

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Biomass DH System Simulation

The heat storage helps to increase the overall efficiency of the system

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Biomass DH System Simulation

• The heat storage systems move and lower the optimum pay back time. • The incentives change the convenience of installing heat storage systems.

Best PBT Ther

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District cooling - Gotehnburg

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District cooling- Paris Centre

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Water cooled Air cooled Total energy storage: 140 MWh

Outine: Power-to-Fuels

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ENERGY CONTEXT: THE NEEDS: 1. Large size storage of RES: storage in forms of chemicals 2. Chemicals that can have interest for the energy sector: existing distribution

and utilization infrastructure; several final users (e.g. stationary systems, automotive, etc.)

3. Chemicals as CO2 sink A POSSIBLE SOLUTION: GREEN FUELS One option for fast and sustainable storage is the production of gaseous fuels to be fed in the distribution grid: those fuels could be produced by means of electrolysis processes and thus converted into synthetic methane to be fed into the existing distribution infrastructure. PROS 1. conversion of relevant amount of renewable sources from “flow” to “stock” 2. chemical fixing of carbon recycled from CO2 3. easy utilization of synthetic methane into existing energy infrastructure

(distribution and final uses)

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Integration of Electric and Gas Networks

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GAS DISTRIBUTION GRID

ELECTRIC GRID

Electrolysis Low-priced surplus electricity

H2

Methanation

CH4

CO2

Biomass, biogas, industry, CCS

Up to 5% in CNG Mobility (road transportation)

Gas-to-power

Power-to-gas

H2

Wind, solar, nuclear

H2/syngas

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Conclusions

Energy storage is a key issue in any multi-energy system applied at the urban scale

Integration of distributed generation should compete with quality standard warranty

The role played by EES will be fundamental to shift towards a smart grid concept

TES is essential for an efficient integration of thermal energy production and distribution, using both fossil and renewable sources

The choice to install a certain typology of storage system depends on the application desired

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Thank you for your attention!

marco.masoero@polito.it