Thermal energy storage can take different forms.
A geothermal well or set of wells can be considered to be a thermal battery,
storing and releasing heat for heat and for electricity. Heat can even be
stored in oil & gas wells. However, very high temperature heat is required
for many processes in heavy industry. This is known as ‘process heat.’ To reach
those temperatures requires power that is transferred and stored in the medium.
The mediums analyzed here include carbon graphite blocks, silicate refractory
bricks, crushed volcanic rock, and molten salt.
Antora Energy’s Carbon Block Thermal Battery is the
Hottest By Far
Bill
Gates-backed Breakthrough Ventures has invested heavily in Antora Energy’s
thermal battery system which heats up carbon blocks and retains heat at
temperatures above 1,800C (3,272F). The energy can be discharged as heat or electricity.
Heat is converted back to electricity via thermophotovoltaic
cells (TPV cells), which I wrote about back in March. Cement and steel
plants are among the targeted applications. The heat and electricity are
expected to function like a combined-heat-and-power plant to provide both heat
and electricity when needed. Thus, in addition to providing process heat, the
thermal battery can also be tapped to smooth power demand fluctuations due to changing
supply conditions, including renewables intermittency. The main goal is to
provide an uninterruptible and reliable supply of process heat. Breakthrough
Ventures’ partner Christina Karapataki estimates the U.S. market for industry utilizing
process heat is at $60 billion. Potential industries that could benefit in the
future include chemical suppliers, the fuels industry, cement, steel, oil and
gas refining, and food and beverage.
Antora Energy
launched its first commercial-scale system in September 2023 as a first-of-kind
pilot project in Fresno, California. It expects to ship the tech to buyers in
2025 after it completes building a battery manufacturing facility in 2024. They
began producing TPV cells in January 2023. They state that they achieved more
than 40% efficiency for their TPV cells, following 2022 announcements of TPV
cells first reaching over 40%. They expect to produce an initial capacity of 2MW
of TPV cells annually, making it the largest TPV manufacturing facility in the
world. TPV cells have long been used in powering spacecraft. They think the
technology is worked out and are now focused on economics. According to Antora
co-founder and CEO, Andrew Ponec: “This technology breakthrough could have
major ramifications in sectors beyond manufacturing, including the electric
grid, the built environment, and transportation. A new class of efficient,
lightweight, and scalable heat engines could transform how industry thinks
about thermal energy and electricity generation.” TPV cells convert “light
emitted from a high-temperature heat source using cells similar to solar PV.
This conversion occurs directly in a lightweight, solid-state device with no
moving parts.” The TVP development project has been supported by the
California Energy Commission, DOE’s Advanced Research Projects Agency-Energy (ARPA-e),
DOE’s Industrial Efficiency and Decarbonization Office (IEDO), NREL, Berkeley
Labs, the National Science Foundation, and Arizona State University. Funders of
the full project also include Breakthrough Ventures, Lowercarbon Capital, Trust
Ventures, Shell Ventures, BHP Ventures, and Overture VC.
The battery is
considered to be a solid-state carbon block design with battery materials costs
far less than traditional battery materials. It consists of cheap carbon blocks
made of graphite, insulation, a steel shell, and instrumentation and controls
on the outside. China’s recent tit-for-tat tariff on graphite could potentially
affect cost. The carbon block thermal batteries are modular and able to be
transported via truck. The small size indicates the significant power density
of the batteries. Gas, coal, and oil boilers are the traditional means of obtaining
process heat but often require significant scale to reduce costs. This new
modular offering may have some cost advantages for smaller projects since
modularity makes it independent of scale. It remains to be seen if and when it will
be competitive to natural gas boilers, but it does have considerable
flexibility that enables it for niche process heat and power functions. It will
also be a tool in the toolkit for decarbonizing heavy industry. The energy
density advantage over lithium-based batteries is about 3-to-1, meaning three
times the power for the same size footprint. It can store 15 MWh, 5 times that
of a lithium battery. That would make these batteries a medium-duration storage
solution for electricity alone. All the thermal batteries evaluated here do not
require critical minerals aside from Antora requiring graphite, which can be
mined or manufactured. Despite the high heat loads the carbon blocks are not
flammable. They are also expected to have low operations issues. Antora is
expecting 30-year lifetimes with no cycling degradation through time as occurs
with chemical-based batteries. The other companies also tout 30-year lifespans
and no degradation. Antora batteries can be manufactured quickly.
If component manufacturing
costs can be economized and power losses can be minimized, the technology may
eventually become competitive with natural gas boilers and steam boilers powered
by turbines. That, however, remains to be seen. Axios Pro’s Katie Fehrenbacher notes,
however, that “new technologies like Antora's often take much longer than
expected to move from the pilot deployment phase to mass-scale commercial
production.” Will they be able to sell finished, readily deployable, manufactured
carbon block thermal batteries to customers at acceptable prices in 2025? That
remains to be seen.
Rondo Energy’s Silicate Refractory Brick Thermal Battery
Antora is not
the only company moving along with high temperature thermal battery projects. Another
California-based company, Rondo Energy, has a thermal battery that does not
utilize TPV cells but can provide energy via steam to power turbines for electricity.
Rondo’s heat battery utilizes thousands of tons of brick that are heated
directly by thermal radiation, and store energy for hours or days with very low
loss (less than 1% per day). Heat delivery is adjusted via changes in airflow.
Temperatures are AI controlled. Air is recycled which minimizes heat loss. Heat
is delivered as superheated air or superheated steam. It is designed as a
drop-in replacement for boilers. Applications are process heat, power,
calcination (in cement manufacture), drying, and evaporation. Rondo’s investors
also include Breakthrough Energy Ventures as well as Energy Impact Partners,
Microsoft Climate Fund, and John Doerr. Rondo’s 2MWh heat battery pilot project
is currently operational. Rondo’s heat batteries utilize alumina silicate
refractory bricks which can be heated to very high temperatures. The project at
Calgren Renewable Fuels produces the world’s lowest carbon intensity (CI)
ethanol, biodiesel and RNG. Rondo’s brick batteries replace the fossil fuels
used to refine the biofuels. Using Rondo’s heat battery, Calgren can reduce the
carbon intensity of their ethanol production by 50%. Heat batteries can be
charged by renewable energy like wind and solar while electricity prices are
low in times when wind or solar are being overgenerated.
According to
Rondo: The “Rondo Heat Battery is among the highest efficiency energy
storage of any kind in the world, with documented efficiency over 90%. Larger
Rondo Heat Batteries store energy at over 98% efficiency.” Like Antora
Energy’s carbon block heat battery, Rondo Energy’s brick heat battery is a
first-of-a-kind technology project. Rondo’s heat batteries can store 100 MWh
and 300 MWh. Thus, they are considered to be a long duration energy storage method.
They are rated for temperatures up to 1000 deg C.
Brenmiller’s Crushed Volcanic Rock TES for Steam, Lower
Heat Industrial Apps and Waste Heat Recovery
Israeli
company Brenmiller utilizes crushed volcanic rock in their TES systems. The company
was founded by Avi Brenmiller, a former CEO of one of Siemens divisions. Like
the other TES systems, they are modular and solid state storage solutions. They
emphasize using their systems with waste heat recovery from exhausts or chimneys.
They too can generate steam for electricity, and they also tout their systems
for ancillary services for thermal power plants, to reduce the amount of starts
and stops of those plants, which helps them to be utilized more efficiently and
lowers maintenance costs. Brenmiller has at least four projects in operation. The
volcanic rocks can be heated up to 750 deg C, so much lower than Antora’s and
Rondo’s heat batteries.
Malta’s Molten Salt-based Thermo-Electric Energy Storage
System
Cambridge,
Massachusetts based company, Malta, has developed a molten slat-based thermos-electric
energy storage system. In 2018 they were spun-off from Google’s X. Molten salt
has been used in many different thermal energy storage applications including
concentrated solar power (CSP) and as an added cycle in thermal power plants. Malta
is involved in CSP applications and also plans to be deployed at retired coal
plants. This would require a wind or solar array to provide the power to be
stored. They have developed a 100MW power plant model. They also utilize an
antifreeze-based coolant system for colling applications. Their systems can
provide long duration energy storage from 8-200 hours. Like the other TES
systems, they can provide CHP, rotational inertia, ancillary, and load-following
service for the power grid. According to their website: “Malta’s innovative
thermo-electric energy storage system represents a flexible, low-cost, and
expandable utility-scale solution for storing energy over long durations at
high efficiency. The system is comprised of conventional components and
abundant raw materials – steel, air, salt, and commodity liquids.” Molten
salt is a very functional form of TES but is limited to maximum temperatures of
565 deg C with feasible improvements to 600 deg C. That puts Malta’s systems at
the low temperature end of the systems evaluated here.
Thermal Energy Storage Development and Economics
As McKinsey
& Company show in the following graph, heating and cooling accounts for
about 50% of global final energy consumption. Heating and cooling are also emissions
intense in most cases.
Thermal energy storage (TES) is already can
be economical compared to natural gas boilers for low temperature applications.
It should be pointed out that the McKinsey & Company graph below uses very
high 2022 natural gas pricing, so it is not accurate for today. I modified the
graph to give an estimate of the gas boiler range in 2023 vs. 2022, when the
graph was made. They used natural gas prices of $6-12/MMBTU which now have been
averaging around $3/MMBTU in the U.S. European prices are higher so the reality
in Europe is likely between the two ranges. Electricity prices also dropped in
2023 and due to lower natural gas prices, hydrogen prices are also lower in
2023. The graph does show the economic risks of high natural gas prices for
gas-powered industrial heat. We are unlikely to see any natural gas price spikes
in the future that resemble the price spikes in 2022 so the original version of
the graph is not likely to be accurate going forward.
Justin Briggs,
co-founder and COO of Antora Energy, in a July 2023 article in PV Magazine,
writes: “While easily achievable from a technology perspective, electrifying
industrial heat has rarely been economical to date: using grid electricity to
create industrial heat is about five times more expensive than burning natural
gas onsite. Ultra-low power prices during peak renewable-generating hours
enable electrified heat to undercut fossil fuels on cost, but only for a small
portion of the time. Traditional energy storage technologies like lithium-ion
batteries certainly have the potential to smooth out this variability, but they
add costs that largely negate the benefits of cheap renewable electricity.”
My gas boiler range for 2023 more or less reflects that cost difference when
compared to the electric boiler with lithium-ion storage values. One thing the
graph shows without a doubt is that TES is significantly cheaper than
lithium-ion storage for making steam to generate electricity.
Economic
evaluations of TES show that all of the current methods are still in the
de-risking phase and are not yet guaranteed to become commercial solutions
adopted by industry. Cost hurdles are the biggest to overcome. Upfront costs
are high, even with subsidization, so TES is likely to remain niche in applicability
for the foreseeable future. Even so, the technologies are promising if costs
can be lowered and needs for such services and low-carbon storage increase due
to things like mandates, carbon taxes, and the desire to decarbonize.
TES has long
been touted as a way to deal with renewables overgeneration. That overgeneration
grows as more variable generation (wind and solar) enters the grid. Grid energy
is cheapest when supply exceeds demand so energy can be bought and stored with
TES systems during those times. Antora Energy plans to test their thermal
battery in the Midwest in the future where wind overgeneration is growing and
then in California where solar overgeneration is already common. TES is one way
to address curtailment and interconnection issues. Briggs also writes:
“For developers and financiers, thermal batteries open
up thousands of new solar and wind projects that offer a unique hedge against
many of the development risks and barriers that projects face today. By
unlocking a reliable long-term offtaker that circumvents power market
congestion and grid connection wait times, thermal batteries can reduce project
risk and cut off years of expensive waiting time.”
“These factors combine to create robust, financeable
projects, all enabled by a low-risk storage technology that reconfigures proven
systems to convert electricity into heat and store it for days on end.”
Thus, he thinks that TES can also address the significant interconnection issues, including long wait times, facing solar and wind project developers.
Two Newer Mediums and Configurations in R&D Phase:
Pea Gravel and Sand
Sandia
National Laboratories and CSolPower have partnered to develop a thermal storage
project using pea gravel as a medium. They are using renewable energy to heat
the pea gravel to 500 degrees C. An electric heater heats the air which is
transferred to the pea gravel. Like the other thermal storage methods, the flow
is either electricity-to-heat or electricity-to-heat-to-electricity. Pea gravel
is both cheap and abundant. However, it does not retain heat as well as
volcanic rock like basalt. That suggests that in comparison storing heat in pea
gravel will be of less duration. As a short-duration storage method it can be
cheaper than lithium-ion. However, it would likely need to be used more quickly
than lithium-ion storage. It can be used for industrial heat, particularly
low-temperature heat or as a component of high temperature heat.
Developer Homerun Resources entered into a Cooperative Research and Development Agreement (CRADA) with DOE’s National Renewable Energy Lab (NREL), and Babcock and Wilcox Enterprises to develop a project using a “novel energy storage technology to upgrade Homerun’s silica sand while providing clean, reliable energy.” The project combines the refining process of Homerun’s silica sand with thermal storage. The high-purity silica sand is used in renewables projects such as solar panel manufacture. The method has been tested successfully in the lab and is now ready to be field tested. The system utilizes gravity fed sand, heat exchangers, a Brayton power cycle, and steam turbines. They dub this method as particle thermal storage and tout its low cost and long duration. They plan to test the system for energy storage, grid services, and energy arbitrage, with the electricity and heat also helping to purify the sand.
Source: Homerun Resources
According to Homerun
Resources’ website:
“The ENDURING project led by NREL and collaborated
with industry partners has developed key components in the storage system and
verified their operation mechanism through laboratory prototypes testing and
modeling of the component and system performance. The development supports
designs of an electric-charging particle heater, a fluidized bed heat exchanger
driving a power cycle, and a particle storage design for storing hot particles
at 1200°C. An integrated storage system was designed and analyzed for performance
and cost to verify the technoeconomic goals of LDES applications.”
“The ENDURING technology works by heating stable,
low-cost solid silica particles—which unlike molten salts, are stable at both
high and ambient temperatures—to over 1,000 degrees Celsius. This charging
process happens when electric power is cheapest, allowing the resulting energy
to be stored for several days in large storage modules. To discharge this
energy, the hot particles are fed through a heat exchanger, ultimately driving
an electric generator.”
Below is a
summary table I made of each of the TES technologies evaluated here. It shows
that Antora and Rondo are really the two companies able to produce the highest
temperature heat needed for heavy industry. The other two are limited to lower
temperature process heat, but can be useful for grid services, long duration energy
storage, and CHP.
References:
How
heat batteries promise a cleaner future in industrial manufacturing. June Kim.
MIT Technology Review. October 26, 2023. How
heat batteries promise a cleaner future in industrial manufacturing | MIT
Technology Review
Bill
Gates-backed startup launches wildly hot thermal battery system: ‘uninterruptible,
reliable supply of process heat.’ Erin Feiger. The Cool Down. October 7, 2023. Bill
Gates-backed startup launches wildly hot thermal battery system:
‘Uninterruptible, reliable supply of process heat’ (yahoo.com)
Bill
Gates-Backed Startup Pilots Unique Battery to Help Heavy Industry. Michelle Ma.
Bloomberg. September 12, 2023. Bill
Gates-Backed Startup Pilots Unique Battery to Help Heavy Industry - Bloomberg
This
Company Wants To Replace Fossil Fuel Heating With Batteries. Alejandro de la
Garza. Time. October 24, 2023. This
Company Wants To Swap Oil, Gas Heating With Batteries | TIME
Antora
Energy turns on first thermal battery. Katie Fehrenbacher. Axios Pro. September
13, 2023. Antora
Energy kicked off its pilot plant and plans to fundraise (axios.com)
Antora
Energy Launches Ready-to-Scale Industrial Decarbonization Technology &
Establishes New Ultra-High-Temperature Record. Business Wire. September 12,
2023. Antora
Energy Launches Ready-to-Scale Industrial Decarbonization Technology &
Establishes New Ultra-High-Temperature Record | Business Wire
Antora
Energy Begins Production of Highly-Efficient Thermophotovoltaic (TPV) Cells in
New 2MW Manufacturing Facility. Antora Energy. January 24, 2023. Antora Begins TPV Production — Antora
Energy
Antora
Energy: Thermal Batteries Revolutionizing Industrial Decarbonization. Rich
Powell and Mitch Kersey. Clear Path. March 8, 2023. Antora
Energy: Thermal Batteries Revolutionizing Industrial Decarbonization –
ClearPath
Thermal
Storage Solutions to Decarbonize Industrial Heat. Felix Hennebert. The Gigaton.
October 3, 2023. Thermal
Storage Solutions to Decarbonize Industrial Heat (substack.com)
Calgren
Renewable Fuels Case Study. Lowering the Carbon Intensity (CI) of Ethanol.
Rondo Energy. Calgren Renewable
Fuels Case Study — Rondo Energy
Net-zero
heat: Long-duration energy storage to accelerate energy system decarbonization.
McKinsey & Company. Martin Linder, Jesse Noffsinger, Robert Riesebieter, Ken
Somers, Humayun Tai, and Godart van Gendt. November 9, 2022. Net-zero
heat: Long-duration energy storage to accelerate energy system decarbonization
| McKinsey
Thermal
batteries unlock new opportunities for solar developers, financiers. Justin
Briggs. PV Magazine. July 27, 2023. Thermal
batteries unlock new opportunities for solar developers, financiers – pv
magazine USA (pv-magazine-usa.com)
Utilites
TES Allows Flexible Operation And Reducing Emissions. Brenmiller Thermal Energy
Storage. Utility TES -
brenmiller (bren-energy.com)
bGen™
E2S. Decarbonization of Heat. Thermal Storage based Steam Generator. Brenmiller
Thermal Storage. ברושור_
V2 (bren-energy.com)
Malta.
The Grid of the Future Today. malta-flyer-APRIL2023.pdf
(maltainc.com)
Analysing
Malta’s molten salt energy storage technique incubated at Google’s X lab. NS
Energy Staff Writer. June 21, 2019. Profiling
Malta's molten salt energy storage method made at Google's X lab
(nsenergybusiness.com)
Concentrating
solar power at higher limits: First studies on molten nitrate salts at 600 °C
in a 100 kg-scale hot tank. Sebastian Kunkel, Freerk Klasing, Andrea Hanke,
Thomas Bauer, Alexander Bonk. Solar Energy Materials and Solar Cells. Volume
258, 15 August 2023, 112412. Concentrating
solar power at higher limits: First studies on molten nitrate salts at
600 °C in a 100 kg-scale hot tank - ScienceDirect
Concentrating
solar power at higher limits: First studies on molten nitrate salts at 600 °C
in a 100 kg-scale hot tank. Sebastian Kunkel, Freerk Klasing, Andrea Hanke,
Thomas Bauer, Alexander Bonk. Solar Energy Materials and Solar Cells. Volume
258, 15 August 2023, 112412. Concentrating
solar power at higher limits: First studies on molten nitrate salts at
600 °C in a 100 kg-scale hot tank - ScienceDirect
How gravel
could become an inexpensive clean energy storage solution. Hannah Grover. New
Mexico Political Report. November 1, 2023. How
gravel could become an inexpensive clean energy storage solution | NM Political
Report
Exclusive:
A Sand Battery? DoE Picks These Firms For Revolutionary New Energy Storage. Vandana
Singh. Bezinga. November 7, 2023. A
Sand Battery? Department Of Energy Picks These Firms For Revolutionary New
Energy Storage - Babcock & Wilcox (NYSE:BW) - Benzinga
Cooperative
Research And Development Agreement With The U.S. Department Of Energy’s
National Renewable Energy Laboratory And Babcock & Wilcox. Homerun
Resources. Homerun
Resources | Energy Storage
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