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Energy StorageThe Need
The TechnologyThe Future
The challenges
Benoit Cushman‐RoisinENGS 37: Environmental Engineering
November 2019
With partial credit to Prof. Lindsay Anderson of Cornell University
Tesla’s Megapack, 1 to 3 MWh storagePumped hydro 10,000 MWh and up
Why would we want to store electricity?
The situation
1. Electricity is the highest quality form of energy that we have;it is thus very valuable.
3. But it is very hard to store in large quantities.
2. Electricity is easy to transport(over long‐distance high‐tension transmission lines).
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Need for storage
Before photovoltaic and wind energy were added to the mix, electric power was being generated exactly to meet the demand:
Base loads were accommodated by the most efficient but slow to turn on and off technologies, like nuclear reactors and coal combustion plants.
Peak loads were accommodated by the more expensive but easier to turn on and off technologies, like gas turbines.
That flexibility caused no need for storage.
As they grew in capacity, photovoltaic panels and wind turbines changed the pattern. These energy producing technologies are intermittent in some uncontrollable ways. Clouds pass under the sun, wind varies over time, both in ways that we cannot control.
Credit: Dr. Lindsay Anderson, Cornell Atkinson Institute for Sustainability, Cornell University
Progress of renewable energy: World total, all renewables
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Wind power: Total world capacity
By 2018, at least 196 solar PV plants of 50 MW and larger were operating in at least 28 countries
Solar PV: Total world capacity
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Image Source: Jacobson & Delucchi(2009) A Plan to Power 100 Percent of the Planetwith Renewables. Scientific American
A renewable mix to meet 100% of demand on a typical July day in California
The hope
But can you make the wind coordinate with the sun to make this happen?
Solar PV causes issues, including the notorious duck curve.
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Increasing PV causes its own challenges:• flexibility is required;• other renewables cannot provide this;• may increase complexity.
The reality
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The solution: STORAGE
Pumped Hydro
Massive batteries Small‐battery distributed system
Concentrated solar with transfer fluid
Alternate forms of storagenot yet with large‐scale potential
1. Renewable electricity → hydrogen, stored and later reconverted to electricity in a fuel cellExisting technology that may not be scalable to the desired level of capacity
2. Renewable electricity + captured CO2 → hydrocarbon fuel, stored and later used in avia on or truckingTechnology in an embryonic stage
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Sizing up the need
Quick calculation:
Take a small city of 200,000 people With 2.53 being the average number of people in a US household → about 79,000 homesWith average annual electricity consump on of 10,972 kWh per home → 30.06 kWh per day per homeJust need to shave off the peak, say 10% of the electric consumptionTotal: 10% of 30.06 kWh/(day.home) x 79,000 homes = 237 MWh.
This is not counting non‐residential buildings such as those for commerce, schools, government, etc.So, triple the previous number:
→ 500 to 1,000 MWh of storagewould be nice to have
Pumped storage is by far the most mature storage technology.
Existing storage by type
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Pumped Hydro
The idea here is to operate between two reservoirs, one sitting higher than the other.
To even the electricity load of power generation plants, ‐ During times of low demand, electricity is used to pump water from the lower reservoir to the higher one, and ‐ During times of high demand, electricity is re‐generated by letting the water flow through a turbine back into
the lower reservoir.
Round‐trip energy efficiency is around 76% to 85%.
A reservoir 25 m deep and 1 km in diameter situated 200 m higher than another reservoir (or natural lake) can hold enough water to generate 10 GWh.
www.ab
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www.dena.de/en/topics‐projects/projects/energy‐systems/platform
‐for‐pumped‐storage‐plants/
Deutsche Energie‐Agentur
As of 2017, the 43 pumped‐storage facilities operating in the United States were providing around 23 GW, or nearly 2% of the capacity of the electrical supply system according to the US Energy Information Administration (EIA).<https://energystorage.org/why‐energy‐storage/technologies/pumped‐hydropower/>
https://en.wikipedia.org/wiki/Pumped‐storage_hydroelectricity
Typical power profile over a 24‐hour cycle of a pumped‐storage hydroelectricity facility.
pumping
generation
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Concentrated Solar
The fluid is stored in two tanks—one at high temperature (>500oC) and the other at a significantly lower temperature.
Fluid from the low-temperature tank flows through the solar collector or receiver, where solar energy heats it to a high temperature and then flows to the high-temperature tank for storage.
https://www.energy.gov/eere/solar/articles/concentrating‐solar‐power‐thermal‐storage‐system‐basics
This system is used in combination with parabolic power plants in Spain and has also been proposed for several US parabolic plants. The plants can use organic oil as the heat‐transfer fluid or eutectic molten salt (mix of sodium nitrate and potassium nitrate) as the storage fluid.
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Ivanpah Solar Electric Generating System
Largest in the world
located across 3,500 acres of federal land in California’s Mojave Desert
began operations in 2013
392 MW solar generation by 173,500 heliostatsfocused on 3 three power towers
capacity to provide clean, sustainable power to over 100,000 American homes.
Solana Generating Station
Built by Abengoa Solar, about 70 miles southwest of Phoenix, Arizona
parabolic trough solar plant
operating since 2013
280 MW
enough power to supply 70,000 homes
thermal energy storage system provides up to 6 hours of generating capacity after sunset.
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Cheapest way to store solar energy over many hours
Concentrated polar with sun‐chasing flat panels in Port Augusta, Australiamore than 800 hectares generating 300 MWenough electricity to power about 82,000 homes.
For reference, average cost of 1 kWh
US average: $0.10‐$0.12/kWhCalifornia: $0.17/kWh
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Batteries
Until recently, batteries were only for small application, like:‐ Starting a car engine,‐ Flashlights and toys,‐ More recently powered
tools.
The Tesla Megapack
Tesla claims:
Each Megapack can store up to 3 MWh of energy at a time, and it is possible to string enough Megapacks together to store more than 1 GWh of energy.
This would be enough energy to power “every home in San Francisco for six hours.”
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Tesla built the largest lithium‐ion battery in the world in southern Australia using Powerpacks. This system has a capacity of 100/129 MWh and can deliver 100 MW of power.
The system provides the same grid services as peaker plants (using natural gas), but is cheaper, quicker, and with zero-emissions.
The giant battery cost about $66 million and reportedly saved $17 million during the first 6 months of operation.
Overall, it is estimated that Tesla’s giant battery in Australia has reduced the grid service cost by 90%.
Installed in 2018,on time and on budget.
The batteries work in tandem with a nearby wind farm.
Of the three large‐scale energy storage systems mentioned here, batteries are the most versatile because they can regenerate the energy most quickly.
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Applications of the Tesla technology
UK’s first football stadium battery at Arsenal’s Emirates builds business case around tradinghttps://www.energy‐storage.news/news/uks‐first‐football‐stadium‐battery‐finds‐a‐home‐at‐arsenals‐emirates‐ground
Tesla’s Megapack battery is big enough to help grids handle peak demandhttps://www.theverge.com/2019/7/29/20746170/tesla‐megapack‐battery‐pge‐storage‐announced
Tesla’s installation in southern Australiahttps://electrek.co/2018/09/24/tesla‐powerpack‐battery‐australia‐cost‐revenue/
More to come. Stay tuned.
Utility scale renewables create uncertainty
Responsive loads, and distributed resources
Image source: Wikipedia (edited by Lindsay Anderson)
The Future: A coordinated grid paradigm
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Image source: OATI Energy solutions
New challenges exist in- Managing under increasing uncertainty;- Coordination of ubiquitous, distributed, resources and consumers;- Efficient integration of transmission, distribution, and microgrid systems.
Another view of the coordinated grid paradigm
Challenges
1.Pumped hydro is not for everywhere.For example, it can’t be done in Florida or Illinois where the land is flat.
Topographic map of the Taum Sauk pumped storage plant in Missouri
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Challenges – cont’d
2.Tesla’s batteries are based on the lithium‐ion cartridge battery, which uses lithium, nickel and cobalt. Of these, cobalt is the least available.China has been buying the largest cobalt mines across the world.
Now non‐Chinese companies try to reduce or eliminate the cobalt contents of their batteries.
Challenges – cont’d
3. Land availability‐ Not in my backyard (NIMBY)‐ Permitting issues
4. Large investments needed‐ Government support needed
5. Unforeseen environmental impacts‐ All new technologies deployed at large scales eventually cause problems.