Among the high-temperature storage solution providers that have reached an advanced stage in terms of commercialization are also Brenmiller from Israel and Rondo Energy from the USA. Brenmiller, with its bGen product, has already commissioned four projects at its clients’ sites in the USA, Israel, Brazil and Italy since 2022. Rondo Energy put its first commercial project in the USA into operation in March 2023. Both companies primarily offer power-to-heat solutions for industrial clients. They were both founded by people with a history in concentrating solar technologies. They have both also announced that they have production capacities for their storage systems in place. The photo shows the inauguration of Rondo’s Heat Battery installed at ethanol producer Calgren Renewable Fuels in California in March 2023. Managing Director John O’Donnell introduced the technology on site during the inauguration. You can find the entire results of the study on high temperature storage solution providers here.
Photo: Rondo Energy
Rondo Energy offers heat-as-a-service with a stack of bricks
Rondo Energy is a fairly new company, founded only in 2020 by one of the top managers of the former company Glasspoint. John O’Donnell left Glasspoint shortly before its insolvency in March 2020 and founded Rondo Energy. The company aims at offering large industrial heat consumers, ranging from cement and steel factories to textile and food producers, a flexible way to use power-to-heat. In February 2022 Rondo Energy closed a series A funding round with USD 22 million led by two investment firms: Breakthrough Energy Ventures and Energy Impact Partners. One and a half years later in August 2023 the series B funding resulted in USD 60 million of new capital contributed by ten investors.
The storage system consists of stacked refractory bricks, an established technology used for centuries to recycle heat from blast furnaces in the steel industry, as O’Donnell put it in an interview. The bricks are heated up to 1,500 °C via a resistance heater using excess renewable electricity from the grid. Hot air flows through the bricks and is superheated before being delivered to a customer or being passed over to a standard boiler tube to generate steam at variable temperatures and pressures. To mitigate the risk of investment for the industrial clients, Rondo offers them a heat delivery contract, supplying energy at costs per kilowatt hour that are lower than for gas-fired heat. The first client to profit from such a heat-as-a-service contract is the ethanol producer Calgren Renewable Fuels in California (see table below). The 2 MWh Rondo Heat Battery started operation in March 2023. It provides hot water to the customer to preheat existing boilers.
The bricks, the battery’s storage medium, are currently produced in a facility in Thailand owned by the Siam Cement Group. The storage system is assembled on-site at the client’s facility. According to a press release from Rondo Energy from June 2023, the factory in Thailand can produce bricks at a capacity of 2.4 GWh per year.
Rondo Heat Batteries are offered in two sizes 100 MWh and 300 MWh. “A full-size heat battery storage system will have in excess of 1,000 bricks, with each brick storing power equivalent to a Tesla Model X”, compared Conner Gordon, Marketing Director at Rondo Energy.
Scheme of charging and discharging Rondo Heat Batteries Source: Rondo Energy
| Storage system provider | Rondo Energy, USA | Brenmiller, Israel | Brenmiller, Israel |
| Client name | Calgren Renewable Fuels, California | Enel, Italy | Fortlev, Brazil |
| Name of storage | Rondo Heat Battery | bGen | bGen |
| Type of storage / storage material | Bricks | Solid-state storage with crushed vulcanic rocks | Solid-state storage with crushed vulcanic rocks |
| Operation mode of storage | Power-to-heat | Heat-to-heat | Power-to-power |
| Maximum storage capacity | 2 MWh | 24 MWh | 1 MWh |
| Which application is stored heat used for? | Pre-heating boilers | Providing hot air to the factory | Providing stored heat to the steam turbine for balancing the grid |
| Heat-transfer medium | Air for charging and discharging | Steam | Air |
| Range of temperature for operating storage | Above 1,000 °C | Up to 750 °C | Up to 750 °C |
| Date of commissioning | March 2023 | n/a | 2022 |
Key data for the first commercial plants from Rondo Energy and Brenmiller. A critical point in the table above is the maximum storage capacity information in megawatt hours. There is no standardized method to calculate the heat capacity of a high-temperature storage system and therefore numbers reported by each provider may be inconsistent or vary based on what calculation has been used. On this aspect, please also read the interview with storage expert Annelies Vandersickel.
Source: companies’ information
Brenmiller’s first commercial plants in Italy and Brazil
Brenmiller Energy was founded in 2012 by Avi Brenmiller, former CEO of Siemens CSP and Solel. After he sold his company to Siemens in 2008, he shifted his focus on power-to-heat storage solutions. As per the current Chief Business Officer, Doron Brenmiller (son of Avi), the company is placing a significant emphasis on their patented thermal energy storage system named bGen. It uses crushed rocks to store heat at temperatures up to 750 °C.
He highlighted that the modular design allows to stack units ensuring a minimal footprint while maintaining good energy density. Another noteworthy feature according to Brenmiller is the incorporation of electrical heaters inside the pipes of the system: “Some of the pipes are filled with electrical heaters, some include tubes for the steam cycle. But the advantage of doing this instead of using external heaters is that we can achieve high efficiency in the charging cycle, with almost no energy loss.”
Brenmiller produces the bGen storage units in Dimona, Israel. Inauguration of the factory was celebrated in May 2023. The related press release states that the factory has a capacity of producing storage systems with 4 GWh annually.
Brenmiller’s storage bGen filled with crushed rocks is charged with electric heaters which are included in the pipes. Source: Brenmiller Energy
Brenmiller asserted a focus on industrial clients, “particularly in sectors such as food and beverage, pharmaceuticals, district heating, and healthcare”. The CEO highlighted their traditional markets in Israel and the USA, where the company is listed on both the New York Stock Exchange (Nasdaq) and the Tel Aviv Stock Exchange. However, he expressed particular interest in two additional markets. The first is Brazil, where in 2022, they inaugurated their first commercial demonstrator for a plastic factory in Anapolis. The 1 MWh bGen plant is a pioneering project that might be expanded to include some more units in the same factory.
Another key market for them is Italy, where they executed the so far largest storage system with 24 MWh together with the utility Enel. The power-to-power solution is integrated into a 400 MW gas-fired thermal power plant in Santa Barbara, Tuscany. The storage system ensures a reduced number of starts of the power plant and greater speed when making power adjustments. This is necessary to operate the power plant in a grid with a high share of renewable electricity. The project was partly financed by the Israeli Innovation Authority, which supported Brenmiller with EUR 1 million in financing.
This news article was written in cooperation with Alejandro Diego Rosell, freelance journalist from Spain.
