Energy Storage:Existing Technologies and

their Importance for Renewable Energy

Alexandre Immas

Maggie Richani

Romina Rodriguez

Nicolas Zweibaum

CE 292 - Technologies for Sustainable Societies

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What is “Energy Storage”?Storing some form of energy to use at a later time to

perform a useful operation

Batteries: most successful example

3The Challenge: Storage of Electricity

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How it works now…

How do we know how much energy to produce in order to meet the current demand?

There exists an Energy Market regulated by the ISO (International Organization for Standardization)

ISO is a non-governmental organization that forms a bridge between the public and private sectors by collecting data about the current supply and demand of electricity and issues an hourly release of information

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Today’s Energy Outlook

Source: CAISO, September 2011

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If only we could store it!

Mitigate risks related to climate change because energy storage requires high integration of renewables as we will see

Guarantee energy supply security

Improve the economic efficiency and utilization of the electric system

There exists some technologies that allow us to store energy and use it when needed

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Thermal Energy Storage

Districht heating accumulation tower of Theiss, near Krems an der Donau, Lower Austria with 50000 cubic meters volume.Source: http://en.wikipedia.org/wiki/Thermal_energy_storage

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Thermal Energy StorageWhat is it?

• Store thermal energy in energy storage reservoirs for later use

• Balance energy demand between day time and night time

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Thermal Energy StorageVarious Technologies

• Water storage (e.g. hot water storage tank):• High specific heat capacity• Non-toxic• (relatively) cheap  

• Ice-based technology:• Large heat of fusion of water• Ice can be produced during off peak periods and used for

cooling at later time• One metric ton of water stores 334 MJ (energy used per

day to cool a 3000 square-foot house in Boston in the summer, source: http://en.wikipedia.org/wiki/Thermal_energy_storage)

 • Molten salt technology

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Molten Salt Technology

• Retain thermal energy collected by a solar tower or solar trough

• Mixture of 60% sodium nitrate and 40% potassium nitrate

• Non-flammable and nontoxic• High specific heat capacity• Can operate at high temperature and low

pressure to achieve high efficiency Rankine cycle (~ 40%, Yang 2010)

• Solar power tower: as low as 5.47 cents per kWh by 2020 (Sargent & Lundy 2003)

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Two Main TechnologiesSolar Tower

Solar TWO molten-salt power tower systemSource: Ortega 2008

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Two Main TechnologiesSolar Tower

Solucar PS10 (Spain): first solar thermal power plant based on tower in the world that generates electricity in a commercial waySource: http://en.wikipedia.org/wiki/Solar_power_tower

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Two Main TechnologiesSolar Trough

• Heat transfer fluid (HTF; oil, molten salt…) pumped through collector field

• HTF can : • go through heat exchanger in steam

generator: production of electricity

• go through heat exchanger with molten salt loop: energy storage

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Two Main TechnologiesSolar Trough

The thermal storage system is loaded during the day. During the night, the power plant can be operated with the stored energy.Source: Solar Millennium 2008 

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Current ImplementationAndasol 1-3 (Spain)

• 50 MWe• 200 ha of land• Solar electricity for up to 200,000 people

(Solar Millennium 2008)

Source: Solar Millennium 2008

16Compressed Air Energy Storage (CAES)

What is it?

Source: NewEnergy News, 2008

Advantages

• High power capacity (50–300 MW)• Large energy storage capacity (2–

50+hours)• Quick start-up (9 min emergency start, 12

min normal operation)• Long storage period (over a year)• Relatively high efficiency (60–80%)• Smaller environmental impact

Source: Beaudin, 2010

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Huntorf, Germany

Source: Crotogino, 2001

• Built in 1978• 11 million ft3 of air stored

at 1000 psi• Requires 12 hours to fully

recharge• Delivers 290 MW for 4 h

Source: Gardner 2007

CAES Plants

Source: renewableenergyworld

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McIntosh, Alabama

Built in 1991

110 MW for 26 h

19 million ft3 stored at 1080 psi

New plant in IowaContract terminatedStorage reservoir not

suitable for size of project

Source: Beaudin, 2010; ISEP

Source: ISEP

Source: Energy Storage & Power

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SetbacksFinding the storage

space, such as geological caverns

Availability of natural gas 1 kWh worth of natural

gas will be needed for every 3 kWh generated from a CAES system (Gardner 2007)

Storage induces losses

• Energy from renewable sources can be stored

Importance for Renewables

• Suitable for long storage duration

• low cost technology for storing large quantities of electrical energy• 2-50 ($/kW), • 15-100 ($/kW)

Source: Beaudin, 2010

Source: Energy Storage & Power

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Research Focus

Locating geological sites for storageLaboratory for Advanced Subfurface Imaging (LASI)-

developing high-resolution underground imaging systems to find salt deposits, porous rocks and other natural underground storage reservoirs.

Cost-effective?What is the size of the market and growth potential?

Improving round-trip efficiency Improve efficiency of individual components in CAES

system

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Hydrogen

Dihydrogen Energy carrier

Feedstocks and process technologies to produce H2

(Source : Riis & Hagen 2006)

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Water Electrolysis

H2O + electricity -> H2 + 1/2O2

Chemical equation

Electrolysis schematic

(Source : Riis & Hagen 2006)

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Hydrogen Storage

Volume and weight for the storage of 3kg of H2

(Source : Riis & Hagen 2006)

Gas- Low energy

density- High pressure

Liquid- Better energy

density- Low temperature

(-253 °C)

Solid- Early development- Good energy

density- Safe

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Economic aspects

Hydrogen from renewables

- Distributed production

- Small-scale unit- 20 – 40 USD/GJ

Hydrogen from fossil fuels

- Central production- Large-scale unit- 5 – 8 USD/GJ + 15-20

USD/GJ/100miles

-> Competitive for industries-> Still a big gap for transportation: Gasoline = 2.5 USD/GJ

(Source : Riis & Hagen 2006)

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Social aspects

Hydrogen has bad press :

explosive, flammable

Storage issue

Hidenburg disaster Hydrogen car

(Source : Gonin 2010)

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Environmental aspects

• Hydrogen production is : - 96% from fossil fuels- 4% from electrolysis(Source : Riis & Hagen 2006)

• Policy must incite production of H2 from renewables and not from fossil fuels

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In Conclusion…

Energy Storage Technology

Current Capacity (MW)

Discharge Time(hours)

Setback

Thermal Up to 150 15 • Only coupled with thermal solar

• High capital cost

Compressed Air

50-300 2- 50+ • Finding the storage space, such as geological caverns

• Availability of natural gas

Hydrogen (Rastetter 2011)

< 1 MW 5 min • 96% of hydrogen produced is from fossil fuels

Reach feasible and practical solutions that:1) Reduce emissions by integrating renewables 2) Secure the future of energy supply

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References• International Energy Agency (IEA). "Cities,Towns and Renewable

Energy." 2009. Web. 18 Sept. 2011. <http://www.iea.org/textbase/nppdf/free/2009/cities2009.pdf>.

• Gardner, John, and Todd Haynes. "Overview of Compressed Air Energy Storage." Sustainability Research, Boise State University (2007). Print

• Crotogino, Fritz, Klaus-Uwe Mohmeyer, and Roland Scharf. "Huntorf CAES: More than 20 Years of Successful Operation." (2001). Print

• Beaudin, Marc, Hamidreza Zareipour, Anthony Schellenberglabe, and William Rosehart. "Energy Storage for Mitigating the Variability of Renewable Electricity Sources: An Updated Review." Energy for Sustainable Development (2010). Print

• Iowa State Energy Park (IESP). http://www.isepa.com/• NewEnergy News. http://newenergynews.blogspot.com/2008/09/new-

ideas-in-new-energy.html• http://www.renewableenergyworld.com/rea/news/print/article/

2010/09/extending-performance-energy-storage-takes-on-the-variability-conundrum

• Trygve Riis, Elisabet Hagen, Preben Vie, and Oystein Ulleberg. "Hydrogen Production and Storage." International Energy Agency (IEA). 2006.

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References• Michel Gonin. Lecture. Energy and Environment. Ecole Polytechnique,

Palaiseau. 2010.• Aline Rastetter. "Le Stockage Des énergies Renouvelables, Une

Opportunité Pour L'hydrogène ?" Speech. Salon Des EnR. Alphea Hydrogene, 2011.

• Wikipedia, The Free Encyclopedia. « Thermal Energy Storage. » http://en.wikipedia.org/wiki/Thermal_energy_storage. Accessed Sept 19, 2011.

• Yang Z., Suresh V. Garimella, “Thermal analysis of solar thermal energy storage in a molten-salt thermocline.” Solar Energy, 84, pp. 974-985, 2010

• Sargent & Lundy LLC Consulting Group, « Assessment of Parabolic Trough and Power Tower Solar Technology Cost and Performance Forecasts. » National Renewable Energy Laboratory Subcontractor Report, October 2003

• Ortega et al., « Central Receiver System Solar Power Plant Using Molten Salt as Heat Transfer Fluid. » Journal of Solar Energy Engineering, 130, May 2008

• Wikipedia, The Free Encyclopedia. « Solar power tower. » http://en.wikipedia.org/wiki/Solar_power_tower. Accessed Sept 19, 2011.

• Solar Millennium, “The parabolic trough power plants Andasol 1 to 3.” 2008

• Energy Storage & Power-LLC http://www.energystorageandpower.com/