⚡The missing key to going fully renewable lies in heat.
Scaling up renewable energy 10x means to develop and implement innovative large-scale renewable energy storage.
hey! welcome to our newsletter.🌿 in case you do not know us: we’re mafer and allison, 18-year-old peruvian incoming freshman at stanford university and ucsd. we’re very glad to have you here.
We need to get rid of fossil fuels, and while renewable energy is the solution, we are still facing challenges.
The concept is simple: the sun is not always shining. Sometimes, the supply of this source does not meet the demand curve throughout the day. In fact, according to the International Energy Agency, over 20% of renewable energy is lost due to a lack of long-duration storage. A specific example of this is the recent case study of the United Kingdom:
“In the U.K. alone, 1.35 trillion watt-hours of solar energy were lost in a span of 2 months. With this energy, they could have powered 1.2 million homes.” - Electrical Review, 2023
After some calculations, that amount of energy could have powered all of those houses for 7 months.
This example serves as a microcosm of a bigger reality: potential is being lost. And wrongfully so, since the large-duration energy storage industry is heavily neglected in comparison to other energy-related issues.
Lithium-ion batteries for long-duration energy storage. Source: Energy Storage.
Today, lithium-ion batteries (LIB) are the most widely used method of LDES. And even though they have a 90% of energy storage efficiency, a bigger problem is still present – they are expensive. Or at least more expensive than the prices that we will need for an effective energy transition in the next 10 years. Let’s look at the numbers:
The cost per unit of energy of LIB is $152/kWh
Until now, LDES needs to reach at least $20/kWh to reduce electricity costs by ≥10%.
With current electricity demand profiles, energy capacity costs must be ≤$1/kWh to fully displace all modelled firm low-carbon generation technologies.
LIB batteries also provide between 4-10 hours of storage, when we will actually need at least 300 hours to hold the intermittencies of renewable energy. This is because a total of 7200 gigawatts (GW) of electricity capacity needs to be built worldwide to keep pace with increasing electricity demand while also replacing existing power plants expected to be retired by 2040 (around 40% of the current fleet).
But that is not the only issue. If we now focus on alternative LDES limitations, we have multiple standpoints to consider.
To understand it better, let’s connect it to the 5 LDES technology parameters to consider when breaking down the problem:
Energy storage capacity cost
Charge power capacity cost
Discharge power capacity cost
Charge efficiency
Discharge efficiency
The first and third bullet points are the current relevant focuses. One of the most promising technologies that take advantage of the cost per energy stored is thermal energy, which also is considered to have the potential to be applied in diverse geographical areas. But nothing is always that straightforward. So, let’s dive into the diverse types of energy storage, their limitations, and current research.
🔋The big picture: what is being done today?
There are four main types of LDES on the loop:
Overview of types of LDES. Source: McKinsey & Company.
💡Electrochemical storage: includes flow batteries and liquid metal batteries. The main issue is its elevated costs.
🧪Chemical storage: includes hydrogen and hydrogen-derived fuels. It is one of the cheapest forms of chemical storage as it relies on geological features. The energy capacity costs range from $1 to $5/kWh for hard rock caverns all the way down to around $0.5/kWh for some depleted gas or oil fields. Its main issue is the infrastructure and conversion processes involved in making hydrogen, storing it, capturing CO2, combining hydrogen and CO2, and then burning the resulting fuel in combustion turbines.
⚙️Mechanical storage: examples include pumped hydroelectric energy storage and compressed air energy storage (CAES). It is the oldest and one of the most common LDES today. The main mechanism consists of water being pumped from a lower reservoir to a higher one and then running back down through turbines to recapture the energy. The main challenge with that both heavily depend on geographical characteristics, creating restrictions for their large-scale implementation.
🔥Thermal storage: useful for both heat and electricity storage. One of the most familiar mechanisms is using concentrated solar power using molten salt, and the most “promising” is pumped thermal energy storage.
Research and startups delve more deeply into the nuances of LDES to not only increase the flexibility of renewable energy but also find a solution to do so with net zero emissions.
Antora Energy ($51.5M in funding) uses zero-carbon heat and electricity to electrify heavy industry and develop thermal energy storage technologies. The increased funding of this startup shows the potential of these LDES.
Energy Vault focuses on gravity and kinetic energy storage systems and has $110M funding in store.
There are also larger-scale companies such as ESS Inc., specialising in iron flow batteries for a low cost. They have unlimited cycle life and, now, they have 19 investors and $297M in funding.
Another interesting field is liquid-air energy storage, where Highview Power is a pioneer. Their product can deliver enough electricity to power over 200,000 homes for 12 hours in two weeks.
These are just some examples of what is being done today.
As more and more renewable energy sources are added to the grid, more and more flexible resources that can fill those demand gaps will be required. So sit back and relax, because we will now take you into the specifics of long-duration energy storage (LDES), its problems, and our proposed solution for the next big thing in climate: pumped thermal energy storage.
📌Pumped thermal energy storage 101.
Temperature-Entropy diagram for ideal PTES system, charge mode is anticlockwise, discharge mode is clockwise.
Thermal energy storage (TES) is a technology that helps us to store heat or cold energy for later use. Specifically for pumped thermal energy storage (PTES), the system has a fluid used to store and release energy. This is a reversible cycle where, in charge mode, the fluid is compressed, giving off heat to a hot storage area, then it expands and cools a cold storage area. This process absorbs mechanical energy and turns it into stored heat.
The achieved turn-round efficiency depends on the thermodynamic reversibility of the compressor and expander, the effectiveness of the thermal stores at returning the gas during discharge as near to the charging temperature as possible, pressure drops in the circuit, and heat leaks to and from the circuit.
As we understood more about the technology, we then dived into the technical breakdown of the limitations of this type of this LDES.
Problem breakdown: Thermal energy storage.
We found out that the problems were, in fact, interconnected and correlated. As we broke down the lack of cost efficiency, we concluded that it was highly dependent on the material used, as well as its energy density, thermal stratification, and safety considerations.
🤔Then, what are we propsing?
In the pursuit of a groundbreaking solution to the persistent challenge of achieving efficient long-term energy storage, we present SaveHeat—a pumped thermal storage technology that departs from convention by focusing on heat, rather than electricity, as the key to unlocking sustainable energy storage capabilities.
But, why thermal energy?
Our decision to delve into the realm of thermal energy storage is rooted in two compelling reasons that underpin the superior potential of this approach:
🔝Enhanced Energy Density: In the realm of storage technologies, thermal energy storage boasts the remarkable ability to achieve significantly higher energy densities compared to certain conventional electrical storage methods. This inherent advantage translates into the capacity to store more energy within a given volume or mass, ushering in a new era of compact and potent storage solutions.
⭐Efficiency at Its Core: Embracing the thermal frontier empowers us to circumvent some of the efficiency bottlenecks encountered by conventional electrical storage systems. These bottlenecks manifest in the form of energy loss during charging, discharging, and self-discharge processes. By harnessing heat storage, we strategically sidestep these energy conversion inefficiencies, paving the way for a more efficient and cost-effective energy storage landscape.
🔥Storing heat is 2x more efficient.
At the heart of our revolutionary SaveHeat technology is a system that harnesses the intrinsic power of thermal energy. This is our first design:
First, solar energy is harnessed—nature's most abundant and renewable resource.
The captured solar energy is channeled into a network of resistance heaters that conjure a searing heat akin to the brilliance of a 2500-degree Celsius incandescent light bulb filament.
This intense heat is then channeled into transforming a liquid metal into a veritable thermal powerhouse, attaining a temperature of 2400 degrees Celsius.
Enter our storage unit, brimming with an assembly of affordable graphite blocks. These unassuming blocks transform into guardians of heat, absorbing the thermal energy with unparalleled efficiency.
As the graphite blocks bask in the intense heat, they ascend to a blazing 2400 degrees Celsius, effectively storing the thermal energy within.
When the need arises. The liquid metal, now carrying the stored heat, embarks on a journey back to our power conversion unit.
With each flow of the liquid metal, the heat is gradually extracted and converted into a formidable surge of electricity, ready to power our world.
As the liquid metal bestows its heat, it cools, undergoing a transformation that leads it back to the embrace of the graphite blocks.
But we don't stop there. To elevate the efficiency even further, we've incorporated the prowess of Aluminum Oxide—a nanoparticle that shields against heat losses and fortifies our system against corrosion. This nanoparticle coats the internal surfaces of our thermal energy storage unit, ensuring minimal energy wastage.
🔛SaveHeat is different because heat makes it 50% more efficient.
Here's what makes SaveHeat shine:
Reversible cycle: At the heart of SaveHeat lies a reversible thermodynamic cycle—a mesmerising dance that enables us to transition between energy storage and release with remarkable efficiency.
Costing a New Horizon: The levelized cost of storage (LCos) associated with SaveHeat is nothing short of competitive and even surpasses the established methods of pumped hydro and compressed air energy storage (CAES).
Everywhere, Anywhere: Unconstrained by geographical limitations, SaveHeat is a versatile solution that can be implemented anywhere on the globe—a far cry from the site-specific requirements of pumped hydro and CAES systems.
Nanoparticle Prowess: By incorporating Aluminum Oxide nanoparticles, we've endowed our system with an additional layer of excellence. This nanoparticle actively minimises heat losses and wards off corrosion, ensuring our technology's durability and efficiency stand the test of time.
💰SaveHeat, save money.
In the relentless pursuit of sustainable energy storage solutions, the bottom line often looms large—the cost.
Graphite Medium ($3.6): At the core of our thermal energy storage prowess lies the dependable graphite medium, a cornerstone component that facilitates heat absorption and release with remarkable efficiency. This secures the foundation of our system.
Graphite Insulation ($2.3): Surrounding our graphite medium is a cocoon of insulation—a strategic shield that traps the stored heat within and prevents unnecessary losses.
Heat Transfer Fluid (HTF) ($0.7): The Heat Transfer Fluid (HTF) plays a pivotal role, orchestrating the fluid movement that encapsulates the essence of energy storage and release.
Construction ($4): Building a robust infrastructure is the cornerstone of any technological venture, and SaveHeat is no exception. We establish the stage upon which our thermal energy storage masterpiece unfolds—a stage that's as durable as it is dynamic.
Zinc Oxide Nanocoating ($8.5): The innovation doesn't stop with construction. We introduce the brilliance of Zinc Oxide nano coating. This is the guardian that shields our system against the ravages of time, maximizing its lifespan and optimizing its efficiency.
Tank Base ($0.6): The bedrock’s modest investment ensures that the structural integrity of our storage unit is unwavering, providing a solid foundation for the dynamic interplay of heat and energy.
Pumps and Piping ($0.2): The conduits of energy transfer—pumps and piping—are the arteries that ensure the rhythmic circulation of heat. This ensures the seamless flow that defines the heart of SaveHeat's thermal cycle.
Inert Containment ($0.2): The stability of our system hinges on the containment of all elements within an inert environment.
💡Why this is the better alternative.
As mentioned in the table below, If we compare our solution with Lithium-ion batteries and compressed air energy storage, SaveHeat offers more advantages regarding cost-effectiveness, with lower costs, positive geographical flexibility, and more than 16 hrs of electricity, which makes up for the difference between the energy conversion efficiency of Lithium-ion batteries and compressed air energy storage systems.
Comparison of advantages between SaveHeat, Lithium-ion batteries, and CAES systems.
👀But… why hasn’t this been done before?
Even though this technology complies with the needed prices to be a viable LDES option for renewables, there are still some limitations that we are striving to solve.
The efficiency of electricity conversion, for example, is lower compared to other LDES, which is a critical factor to meet the fluctuating electricity demand during the day. Since the charging efficiency (40.2%) is lower than the discharging efficiency (85%), our next step is to double its charging efficiency by the end of 2033. This would not only make the main barrier of this technology to the market but also achieve the long-desired cost-efficient and energy-dense solution needed for LDES to be even an option in the future. Thus, one of our next milestones will be to close this gap through the improvement of insulation materials around the storage facility.
Additionally, in the mires of the need to valorize CO2, SaveHeat aims to include CO2 to revalorize it as graphite through molten salt CO2 capture and electro-transformation (MSCC-ET), putting our efforts into net zero emissions.
With these ideas in mind, SaveHeat positions itself to make sure all renewable energy is used, through both an intersectional and environmentally conscious lens. Be sure to stay in touch for the next steps this idea has ahead!
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