A new battery technology has been derived from a widely available pigment which inspired Picasso’s ‘Blue Period’. But could it rival the dominant chemistries currently available on the market? Natron’s Jack Pouchet believes the technology has the potential to transform the data centre sector. Louise Frampton reports…
Prussian Blue is a dark blue pigment derived from ferrous cyanide – a material that has been safely used for over 250 years in paint (leading to Picasso’s famous ‘Blue Period’), blue jeans, and blueprint paper. It is also used in medicine to treat certain types of heavy metal poisoning and in children’s finger paint, where it is considered edible and non-toxic. However, Prussian Blue has now found its way into a new application – battery technology.
Natron Energy has developed a new, patented cell technology based on Prussian Blue electrodes and a sodium-ion electrolyte. The Prussian Blue electrodes produce a battery with extremely low internal resistance and high round-trip energy efficiency. This makes Natron batteries the ideal platform for stationary energy storage and UPS applications where reliability and high-power are paramount.
Natron Energy was first launched in 2012 as a Stanford spin out by founder and CEO Colin Wessells. Wessells’ PhD work at Stanford focused on identifying safe, high power chemistries that would create new battery products. Natron’s concept from the outset was to design a battery using materials that are considered safe and highly available as global commodities. The battery technology does not use any rare earth metals and can be produced in high-volume on standard lithium ion production lines.
“With these advantages, Natron can quickly achieve price parity with lithium ion technologies and, in the near future will reach price levels of lead acid batteries,” comments Jack Pouchet, vice president of sales for Natron Energy. “Our early production units have achieved cost targets that have already caught the attention of customers in the UPS, electrical, and Telecom OEMs markets.”
The sodium batteries are reported to offer round-trip energy efficiency of 97% in normal operation and over 98% round-trip efficiency on a coulombic level.
“As we move to larger form factor batteries for high-capacity UPS and EV/Grid applications, we expect to see additional improvements in system-level efficiencies,” says Pouchet.
He explains that this efficiency stems from the extremely low internal resistance within the Natron sodium battery. The Prussian Blue cathode and anode atomic cell structure are effectively large cages that allow ions and electrons to flow in either direction with ease compared with other chemistries. As a result, the batteries experience no mechanical stress and generate minimal heat under a wide range of operating conditions.
“Our extended lifecycle testing at 45oC with high rates of charge and discharge (and no rest or settling time between cycles) have demonstrated the Natron battery tolerates abnormal abuse. Natron has built the first battery in which chemistry does not limit battery lifetime,” Pouchet claims.
Natron’s sodium battery is also claimed to be non-flammable and, due to its chemistry, has no thermal runaway conditions.
“It was our intention from day one to design and build a safer, more efficient, reliable battery using chemistry and material science to eliminate the characteristics and thermal runaway associated with lithium ion batteries in use today. In addition, our sodium chemistry does not use any rare earth elements – like cobalt or tantalum – and, unlike lithium, that uses a large amount of water in the mining and refining processes, our core materials are readily available at significantly lower cost.”
Natron further claims that its sodium battery offers more power (kW) per unit of energy capacity (kWh) rating than lithium ion or lead-based batteries.
“Our significantly lower internal resistance and high round-trip efficiency enable the sodium battery to excel as a short-term power source. For bridging to a generator in the two to five-minute range, or providing ramp-rate power like a supercapacitor. No other battery chemistry is able to provide as much sheer electrical power. Furthermore, Natron’s batteries can do this repeatedly over a similar temperature operating range as lithium ion, but without costly additional cooling,” says Pouchet.
“For long-term energy supply such as two-hour grid serving applications, the sodium battery performs with significantly higher cycle frequency, recharge rates and no settling or recovery times between charge/discharge cycles. However, we do require a somewhat larger footprint than lithium ion for a comparable kWh rating as the sodium energy density in these types of applications is less than lithium,” Pouchet continues.
Traditional telco customers have been attracted to Natron’s 1U product, which features high peak power capacity that enables new architectures for redundancy. A typical 2N battery design that would be required for either a lead or lithium ion battery deployment is totally unnecessary with Natron’s sodium battery.
The battery can provide 2X its rated two-minute peak power for 30+ seconds without modifications. The loss of a string does not limit the peak power of the battery system.
“We see applications for use in any mission critical infrastructure where bridging to genset/fuel cell or other energy source is required. Due to the sodium batteries’ ability to function like a supercapacitor, the battery can be used with prime power fuel cells to provide ride-through for variable ramp-rate loads,” comments Pouchet.
Other ideal applications include mining and industrial applications, where frequent charge/discharge events are considered normal, or in applications where the operating conditions would put tremendous strain on lead or lithium ion batteries. For off-grid sites such as mines, the sodium battery can be paired with solar, wind or hydro systems to provide long autonomy periods, greatly reducing the demand for stationary generators, fuel deliveries, and generator service/repair cycles. The high peak-power capacity of the sodium battery means that data centre operators can also use their battery plant for grid services such as frequency regulation, demand-side response, or peak shaving to generate additional revenue streams.
“Our ongoing life-cycle testing has demonstrated approximately 18,000 full discharge/charge cycles at a 12C rate with no impact on battery performance. We fully expect to exceed 50,000 cycles,” comments Pouchet, adding: “We can go from zero to 99% charge in as little as eight minutes. This scenario is highly unlikely in a data centre application as operators will want to keep a minimum reserve on their battery, say 25% of capacity.
“That level would be considered heresy for a lead or lithium ion battery plant but the sodium battery’s high peak power capacity and ability to delivery extreme amounts of energy over short durations (such as bridging to genset) ensures there will be sufficient reserves available whenever they are called upon, regardless of the state of charge.”
Natron is in the process of securing UL certification for its 1U tray and expects to formally launch the product in Q3. The 1U tray platform scales easily within a standard IT rack for increased power. The batteries can be used in applications from 12V to 1,000V DC.
“Market interest has been quite high. All of the major data centre owners and operators have expressed an interest. Many have visited Natron’s Santa Clara facility to inspect our manufacturing methods or witness test performance,” comments Pouchet.
He adds that no single chemistry can support the growth rates being seen within the global mission critical markets. Between data centres, telecom, 5G, EV fast charging, smart cities, transportation, industrial automation, mining, and grid services, there will be requirements for all chemistries – lead, lithium ion, zinc, and sodium.
“Over time we expect there will be a net migration to sodium for mission critical stationary power applications. Especially those where high peak power capacity, cycle-count, ambient operating conditions, life / fire safety, and risk management are concerns.”
Will sodium batteries reach 10% to 20% of the market by 2025? “We would like to think so,” he continues.
So, how could the technology be transformative in the future? According to Pouchet, the performance characteristics of the chemistry is prompting businesses to consider entirely new uses for their existing and future infrastructure deployments.
“Perhaps one of the most significant, from an environmental and business perspective, is the new-found ability for data centre operators to provide grid stability and grid storage services. The data centre industry is currently around 2% of the electrical grid and expected to be in the 4-5% range within the next five years. We are also rapidly moving to a 100% renewable energy mix for data centres and that move to renewables creates new pressures on the electrical grid,” says Pouchet.
“Data centres and utilities can now develop public-private partnerships to leverage these untapped data centre assets to create new revenue streams for the data centre and reduce the need for expensive investments within the public sector.”
He points out that the sodium battery is ideally suited for frequent use:
“You can hit the battery repeatedly with varying demand profiles over an extremely wide ambient range without adversely impacting the batteries’ state of health, availability, peak power capacity, or life expectancy. These characteristics can be put to use by any industry deploying mission critical infrastructure,” explains Pouchet.
He also predicts that sodium battery technology will accelerate further adoption of, and entirely new uses for, fuel cells (solid oxide and PEM) and renewable energy sources, as the characteristics of the sodium battery are well matched to address bridging, ramping, peak power, and extended ride-through requirements that limit the scope and scale for many of these systems.
“I don’t expect anyone is going to immediately convert 100% of their facilities to sodium batteries. But as they gain experience with the battery and realise they don’t need any service, monitoring, cooling, or reserve battery capacity, mission critical site operators will begin to truly realise the available opex savings,” comments Pouchet.
He anticipates that the technology will become more common place, not only for new builds, but also with legacy infrastructure refresh and upgrades.
“We anticipate that many existing lead and even some lithium ion battery plants will start to be converted over to sodium to take advantage of the improved opex, footprint, and improvement to one’s business continuity and risk portfolio,” says Pouchet. He claims there will be continuing pressure on the lithium ion battery market from several fronts.
“The continued global growth of the EV market will see new manufacturing lines become available to keep up with demand. We, at Natron, welcome this, as our battery is also manufactured on these very same production lines.
“However, the EV market will command a premium in terms of volume commitments and force infrastructure markets to either double-down on blanket orders for lithium ion to ensure lead times are within reason (20-26 weeks) and/or pay a premium thereby driving net pricing or margin in the wrong direction.
“A second factor that is looming on the horizon are the total environmental impacts associated with lithium and cobalt. The data centre industry has already faced some difficult headwinds from addressing CO2 emissions and renewable energy reporting requirements. We believe the battery composition, sourcing, and manufacturing processes will be coming under similar scrutiny over time.
“Lastly, in the long run, we believe there will be a bifurcation in the market, with lead and sodium as the preferred stationary power chemistries and lithium ion will transition to mobile and transport platforms where its energy density provides the most intrinsic value,” he concludes.
The sodium battery technology is designed to:
- Produce high power and fast recharge time
- Deliver a long life with up to 100,000 cycles
- Sustain energy capacity with minimal degradation under float conditions
- Operate safely, even under fault conditions that lead other batteries to combust