Energy Dome ($85M for grid-scale storage with CO2 battery)

Energy Dome is a company that offers innovative long-duration energy storage solutions based on a thermodynamic transformation of CO₂ in a closed thermodynamic process to provide electricity storage at low cost, with unprecedented round-trip efficiency and without emissions. Energy Dome’s CO₂ battery can store renewable energy over long periods and discharge it rapidly, making renewable energy dispatchable. In addition, the CO₂ battery costs less than half as much as large lithium batteries.

Challenges: Grid-scale storage

What is grid-scale storage?

Grid-scale storage refers to energy storage systems that are designed to provide large-scale energy storage for electric power grids. These systems are used to store excess energy generated during periods of low demand, such as at night, and release that energy during periods of high demand, such as during the day.

Wind turbines produce clean electricity in Austria.

Grid-scale storage systems can be used to store energy from a variety of sources, including renewable energy sources like wind and solar power. This is important because renewable energy sources can be intermittent, meaning that they generate energy only when the wind is blowing or the sun is shining. By storing this energy, grid-scale storage systems can help to ensure that renewable energy sources can be used to meet demand at all times, even when the wind isn’t blowing or the sun isn’t shining.

Grid-scale storage plays an important role in the Net Zero Emissions by 2050 Scenario, providing important system services that range from short-term balancing and operating reserves, ancillary services for grid stability and deferment of investment in new transmission and distribution lines, to long-term energy storage.

Grid-scale storage technologies

Numerous energy storage technologies are suitable for grid-scale applications, and their characteristics differ.

Pumped-storage hydropower is the most widely used storage technology for grid-scale storage, and it has significant additional potential in several regions. The efficiency of a hydroelectric pumping storage system is high, with a generation efficiency of about 90%. This means that only 10% of the energy stored in an upper reservoir is lost when the water passes through the turbines to generate electricity. Pumped-storage hydropower is the most widely deployed storage technology today, with total installed capacity standing at around 160 GW in 2021, accounting for 2.5% of global installed capacity and 99% of the total capacity of energy storage facilities.

Batteries are a promising technology for grid-scale energy storage, as they can provide fast response times and high energy density. Their market has seen strong growth in recent years. The current market for grid-scale battery storage in the United States and globally is dominated by lithium-ion chemistries.

Other storage technologies include compressed air, flywheel energy storage, supercapacitor, and gravity storage, but they play a comparatively small role in current power systems. However, these technologies have the potential to play a larger role in the future as the demand for grid-scale storage increases.

Grid-scale storage challenges

There are some of the key challenges of grid-scale storage in terms of cost, technical limitations, integration with the grid, and environmental concerns.

The upfront costs of building large-scale energy storage facilities can be high, which may make it difficult to justify investment in some cases. Additionally, the cost of batteries, which are commonly used in grid-scale storage, has been declining in recent years, but it is still relatively high compared to other forms of energy storage.

There are several technical limitations associated with grid-scale storage, including the fact that many forms of energy storage have lower energy density than fossil fuels, which means that more physical space may be required to store the same amount of energy. Additionally, there are limitations in terms of the ability of some forms of storage, such as batteries, to provide energy over long periods of time.

Integrating grid-scale storage with existing electricity grids can be challenging, as it requires careful coordination between energy storage facilities, generators, and the grid itself. This is particularly true when it comes to managing fluctuations in energy supply and demand.

Some forms of grid-scale storage, such as large-scale hydroelectric facilities, can have significant environmental impacts. It is important to carefully consider the environmental implications of different storage technologies before implementing them at scale.

Energy Dome Technology

Energy Dome has developed an innovative energy storage technology based on closed cyclic thermodynamic transformations (TTC) of carbon dioxide (CO₂), known as CO₂ battery. During charging, the CO₂ battery uses renewable energy to power a compressor that compresses gaseous CO₂ stored in a casing at ambient temperature and pressure. The compressed CO₂ becomes a liquid that is stored in a tank with a pressure over 60 bar. The thermal energy that is released during the compression process is stored for use in the discharging process.

During discharge, liquid CO₂ from the tank is heated using thermal energy previously stored. The expanded gaseous CO₂ fluid drives the rotation of turbines to generate electricity. The gaseous CO₂ returns to the casing for the next cyclic thermodynamic transformation.

Energy Dome’s CO₂ battery is a promising technology for grid-scale energy storage due to its high round-trip efficiency, stability, and low cost, without carbon emissions.

Energy Dome CO₂ battery

The diagram below depicts the CO₂ battery system of Energy Dome.

The system comprises a CO₂ tank, a CO₂ casing with a pressure balloon inside, a compressor, a motor-generator, a turbine, heat exchangers, thermal storage devices, and pipelines.

CO₂ tank

The CO₂ tank stores liquid CO₂ at ambient temperature and a pressure of over 60 bar.

CO₂ casing

The CO₂ casing has a pressure balloon inside for storing gaseous CO₂ at ambient temperature and pressure.

Compressor

The compressor compresses gaseous CO₂ during the charge process and is at rest during the discharging. During charge, the compressor is driven by a motor that is powered by renewable energy.

Motor-generator

Depending on the conditions, the motor-generator operates either as a motor powered by renewable electricity or as a generator to produce electricity.

During charge, the motor-generator is only connected to the compressor and is disconnected from the idle turbine. It functions as a motor that powers the CO₂ compressor.

During discharge, the motor-generator disconnects from the compressor and only connects to the turbine. It functions as a generator powered by the turbine to produce electricity.

Turbine

Turbine operates during discharge and is at rest during charge. During discharge, the expanded gaseous CO₂ fluid powers the rotation of the turbine, which in turn drives the rotation of the generator to produce electricity.

Primary heat exchanger

During charge, the primary heat exchanger is only in fluid communication with the compressor’s outlet pipe. It functions as a cooler to remove heat from the compressed CO₂ fluid and stores the thermal energy.

During discharge, the primary heat exchanger is only in fluid communication with the inlet pipe of the turbine. It functions as a heater and releases the previously stored thermal energy to heat the CO₂ fluid to a critical temperature before the fluid enters the turbine.

Secondary heat exchanger

The secondary heat exchanger is in fluid communication with a secondary thermal storage device. The secondary storage device is combined with a radiator equipped with fans mounted on a recirculation duct which cools overnight and heats during the day.

During charge, the secondary heat exchanger works as a cooler and removes further heat from the CO₂ fluid as it flows from the primary heat exchanger and into the tank. The heat is stored in the secondary thermal storage device.

During discharge, the secondary heat exchanger uses the previously stored heat in the secondary thermal storage device to preheat the CO₂ fluid as it exits the CO₂ tank.

Additional heat exchanger

The additional heat exchanger is also in fluid communication with the secondary thermal storage device. During charge, the additional heat exchanger preheats the CO₂ gas that enters the compressor. During discharge, it cools the CO₂ gas that returns to the casing.

Auxiliary heat storage

During charge, the auxiliary thermal storage device connects to the compressor in order to achieve an inter-cooled compression with one or more inter-coolings.

During discharge, the auxiliary thermal storage device connects to the turbine to achieve an inter-heated expansion with one or more inter-heatings. The heat accumulated in the auxiliary thermal storage device during the inter-cooled compression is used for the inter-heated expansion.

How does the Energy Dome CO₂ battery work?

CO₂ battery charge

The diagram below depicts the CO₂ battery charging process.

During charge, renewable electricity powers the motor that is connected to the compressor. The motor powers the compressor, which compresses the gaseous CO₂ that is expelled from the casing. Before entering the compressor, the CO₂ gas fluid is preheated by the additional heat exchanger.

The auxiliary thermal storage device connected to the compressor operates one or more inter-coolings. Heat is stored in the auxiliary thermal storage device for the inter-heatings during the discharging process.

The compressed CO₂ fluid exiting the compressor is still hot. Thus, the primary heat exchanger, which is only in fluid communication with the compressor’s outlet pipe during charge, cools the CO₂ fluid and stores the thermal energy. The temperature of the CO₂ fluid falls below the critical temperature.

The CO₂ fluid exits the primary heat exchanger and enters the secondary heat exchanger, which cools the fluid further and stores the thermal energy in the secondary thermal storage device. After leaving the secondary heat exchanger, the liquid CO₂ is stored in the tank at 65 bar and ambient temperature. In this storage condition, CO₂ has a density of 730 kg/m³, which is 400 times greater than its gaseous state in the casing, indicating that the CO₂ battery has a high storing capacity.

CO₂ battery discharge

The diagram below depicts the discharging process of the CO₂ battery.

The discharge of Energy Dome CO₂ battery.

Liquid CO₂ leaves the tank and enters the secondary heat exchanger, which now uses previously stored heat to preheat the CO₂ fluid.

The preheated CO₂ fluid enters the primary heat exchanger, which is now only in fluid communication with the turbine’s inlet pipe. The primary heat exchanger uses the previously stored thermal energy to further heat the CO₂ fluid which becomes gaseous.

The heated CO₂ steam enters the turbine. The motor-generator now is coupled to the turbine only and is decoupled from the idle compressor. It functions as a generator. The auxiliary thermal storage connected to the turbine operates one or more inter-heatings by using the previously stored heat in the auxiliary thermal storage device. Thus, the CO₂ fluid expands, causing the turbine to rotate. The turbine powers the generator to produce electricity.

The gaseous CO₂ fluid exiting the turbine is further cooled by the additional heat exchanger and returns to the casing at atmospheric pressure. The additional heat exchanger stores heat in the secondary thermal energy storage device, which will be used to preheat the CO₂ fluid in the next charge phase.

Energy Dome CO₂ battery performance

Energy Dome’s CO₂ battery is capable of storing 100 MWh when the volume of the pressure-balloon is about 400,000 m³ and the volume of the tank is about 1,000 m³.

The round-trip efficiency of Energy Dome’s CO₂ battery is between 75% and 80%. Energy Dome’s CO₂ battery has a higher round-trip efficiency than any other long-duration energy storage technology currently on the market, including liquid-air, compressed-air, and gravity-based solutions.

The CO₂ battery has a projected operational life of around 25 years. It is significantly less expensive than large lithium batteries.

Advantages of Energy Dome CO₂ battery

There are several advantages of Energy Dome CO₂ battery, including

capable of being done in different geo-morphological situations;
able to obtain high round-trip efficiency;
capable of working with adjustable storage tank pressures;
construction cost of less than 100 USD/kWh;
safe and environmentally friendly;
modular and compact;
lasting or having an increased useful life of 30 years;
flexible and able to get into operation quickly;
corrosion resistant; and
having low levels of vibrations and noise.

Energy Dome Patent

US20230072638A1 Energy storage plant and process
WO2022064533A1 Plant and process for energy storage
WO2021255578A1 Plant and process for energy management
EP4127418A1 Plant and process for energy generation and storage
US20230046094A1 Plant and process for storing and discharging thermal energy
WO2022101727A1 Plant and process for energy storage and method for controlling a heat carrier in a process for energy storage

Energy Dome Products

Energy Dome’s products include the CO₂ battery, which is a long-duration and large-scale energy storage system based on a thermodynamic process that efficiently stores energy by manipulating CO₂.

Energy Dome has also developed a sister system, the CO₂ Energy Transition Combined Cycle (ETCC), which combines gas-fired power production with large-scale energy storage.

Energy Dome’s business model is to license the technology to EPC companies or IPPs, utilities, and the final user. The company has signed a commercial agreement with Italian gas-focused power-generation equipment supplier Ansaldo Energia to bring to market the CO₂ battery and the CO₂ ETCC.