GE’s unique energy storage innovation

One of the most talked about advanced energy equipment innovations in the past year has been the Durathon battery from GE Energy Storage. TowerXchange wanted to understand the unique capabilities of this potential game-changing innovation, how the battery was performing in the field, and how widespread deployment may be within the next year.

TowerXchange: How does the technology and capabilities of the Durathon sodium nickel chloride battery differ from the lead acid and lithium based energy storage solutions currently in use on most African cell sites?

Durathon Battery technology is based on an advanced industrial battery design engineered to meet the growing need for safe, reliable and high performance energy storage for both stationary and motive applications.

The electrochemical reaction within the Durathon battery is quite unique. Each cell is a sealed metal can, with no secondary chemical reactions. Sodium ions travel back and forth across a solid beta alumina electrolyte, which creates stable performance over long life.

There is no self-discharge with Durathon batteries. Because all internal materials are solid at room temperature, they can stay in that state for years with no impact on performance. This characteristic is particularly useful when you consider the inventory management challenges for emerging market cell site equipment.

The Durathon battery has applications across industries, including transportation, telecommunications and back-up power. GE initially began to explore alternative battery technologies that could power large equipment such as locomotives, which meant it required deep cycles, and had to survive temperature extremes as locomotives moved from the warmest to the coldest regions on Earth. It was also designed to be very safe as in a transportation context you couldn’t afford catastrophic failures like fires. Thanks to improvements we have made to the cell design, we’ve created a safer battery.

We noticed that the requirements necessary for its application in transportation - long life, abuse tolerance, deep cycling - were similar to those necessary for telecoms and industries needing stationary power. Currently, there is quite a bit of demand in places close to the equator. To deploy energy storage solutions close to the equator, the solution has to be able to withstand high temperatures and be robust enough to perform in tough conditions.

Another characteristic of Durathon which makes it suitable for deployment in Africa is that it’s built in a single 48v block weighing 120kg. We intentionally didn’t add integrated handling features as a lot of tower operators in Africa have a problem with pilferage. The weight of Durathon doesn’t eliminate theft, but it’s a strong deterrent!

TowerXchange: Tell us about the battery management system built into Durathon.

Because the Durathon battery runs warm, we built in a battery management system (BMS) to manage each module’s temperature, ensuring safe and consistent operation.

But our electronics package does more than just monitor and manage the module’s temperature. As tower operators become more sophisticated about site operations, they need a richer set of information passed to their network monitoring center. Durathon’s BMS can communicate most of its operating data, in real time, to the NOC or even via SMS to technicians.

TowerXchange: How does Durathon’s initial capex, battery lifetimes and Total Cost of Ownership (TCO) compare to alternate energy storage solutions?

Being an advanced battery, Durathon is more expensive than the prevalent lead acid batteries. However, lifecycle is key to TCO, and Durathon has a significantly longer life - up to 15 years in float, and up to 8 years in heavy cycling applications. Durathon also charges in less than half the time of conventional lead-acid batteries.

As a result, payback can be achieved in less than 24 months in Africa, with a longer post-payback lifecycle in which to benefit from efficiencies than with many other energy storage solutions.

TowerXchange: How does the energy density of Durathon compare with alternate energy storage solutions?

Energy density is one of the reasons GE went for this particular technology. We pack a lot of energy into a small package - for example, we can get 150-200Wh per litre from the battery, making Durathon an attractive option on rooftop sites where space is often limited.

We may replace a 1000Ah lead acid battery with our 276Ah module, which is the size of a carry-on suitcase. Which means those large battery banks on rooftops can be removed. For longer autonomy, the site owner may need two units, connected in parallel, to get 10-12 hours of backup time.

Comparing our sodium solution with a lead-acid battery bank, Durathon would typically be one quarter of the weight, and half the volume.

TowerXchange: How does Durathon compare in performance in terms of charge/discharge cycles? And what kind of autonomy can be achieved?

We’ve done a lot of work worldwide on this, achieving 50% fuel savings compared to generator-only operation.

Durathon can typically achieve an 80% state of charge in five hours. When we’re deep cycling, Durathon can repeatedly discharge almost fully without damage.

For our 276Ah standard module we get around 15kWh over a very flat discharge curve. Of course runtime depends on load - for a fairly typical telecom load of 1.5kW, we’ll have usable capacity of 13.8-14kWh, which equates to nine or more hours of discharge per battery.

That’s based on a single 276Ah module. Of course you can place more batteries in parallel to achieve greater autonomy.

The way Durathon charges and discharges is unique, such that older and new batteries will work fine in parallel, which means you don’t have to change whole battery bank if you’re upgrading the energy storage capacity of a site. This is key for towercos as they move from one to two to three tenants - adding extra energy storage capacity usually requires replacing the whole battery bank.

TowerXchange: Is there a sweet spot in terms of the energy load on a site most suitable for Durathon?

Our best performance is 800w-2.4kw per battery.

This is a hot battery - it runs at 300°C, although the outside temperature is only about 10°C above ambient.  During discharge, the electrochemical reaction is slightly exothermic, so at higher loads the battery temperature will rise. While not a safety issue, excessive temperature can reduce the life of the battery, so the battery management system monitors and protects the battery against overheating.

TowerXchange: How is Durathon cooled to adapt to some of the harsh environments in Africa?

Other batteries need a temperature controlled room, whereas all Durathon needs is a waterproof container. There is no need for air conditioning - the electronics can handle temperatures up to 65°C, and the internal cells have no trouble with temperature extremes. So you can eliminate air conditioning for batteries, and just use a DC fan or convective cooling to keep other electronics inside the cabinet within temperature limits.

TowerXchange: Can you give us an idea of the number of cell sites currently using Durathon batteries?

We’re progressing from pilots to launch orders in several key markets such as Kenya, Zambia, Nigeria, Ghana, Egypt and South Africa. As you know, telecoms operators typically run small scale pilots initially - we’re progressing over the next six to eight months to larger orders in 100s and 200s of units. By the end of 2014 we should see Durathon deployed at 1,500-2,000 sites in Africa.

We have deployed 20MWh across all applications since GE Energy Storage started up in the middle of last year. We’ve had very good performance in the field, proof that the solution meets market needs.

TowerXchange: How do you see the balance of business opportunities between green field new site rollouts versus upgrades to the energy storage systems at existing sites?

With many markets approaching saturation, there are a finite number of green field site deployments, even in Africa. Some key countries still have significant numbers of new towers being deployed, such as Nigeria and Kenya.

Sometimes the customer has the budget to invest up-front in an advanced sodium or lithium based energy storage solutions with a high warranty. At other times the rollout might only have budget for low cost lead-acid solutions.

However, there are 150,000 cell sites in Africa, many running primarily on diesel generators. So we see 90-95% of our market in Africa being retrofits.

TowerXchange: What role could GE play in a zero capex, ESCO business model?

GE has a financial arm that is working on financing distributed renewable energy in Africa.

Our ideal business model would be to support local lenders and local managed service providers who have “boots on the ground” in Africa. Typically these local managed service providers have the experience and expertise to develop ESCO offerings, but their capital is bound up in their existing business and they struggle to secure the funding to acquire advanced renewable and energy storage technologies which require higher up front capex but which deliver better TCO over longer periods. GE would be interested to use our financial horsepower to work with local banks and managed service providers to develop the ESCO proposition.

TowerXchange: What is the potential for GE Energy Storage to join forces with the GE Critical Power business?

GE acquired Lineage Power several years ago. They’re now GE Critical Power, one of the leading suppliers of electronics and conversion equipment for telecom. We’re finding that as GE Energy Storage matures as a business there are increasing opportunities to marry GE technologies into a single solution.

By combining energy storage with power conversion and power components we can develop compact energy storage solutions that initially are finding a market in North America, but which will meet a global need eventually. This would enable us to support not just BTS, but BSCs and Switching Centres as well.

Working with GE Critical Power particularly enhances our offering to towercos. We can then offer everything the towerco would need from a passive system perspective, including Eco-Priority rectifiers that manage energy from grid and solar and wind sources. With advanced batteries too, we have the makings of a market-changing offering.

TowerXchange: What are the implications of the release of Durathon for hybrid and renewable energy solution developers? Have you established any relationships with hybrid energy solution developers?

We’ve been dipping our toe in the hybrid market, working with solar-diesel hybrids in a few cases. Some of our pilots have yielded energy savings significantly better than 50%.

Durathon works better with solar-diesel compared to solar-only hybrid sites as ours is a warm battery and needs to stay warm.  In situations that require long periods of autonomy, Durathon consumes its own power, reducing the amount of autonomy available. We’ve found that Durathon works best at sites that need 20 hours or less autonomy. If you’re looking for two days of autonomy or are deploying solar arrays in areas affected by frequent cloud cover, Durathon may not provide enough autonomy alone, you may need a diesel generator to ensure long term availability.

TowerXchange: Finally, please tell us how GE’s re-entry into the energy storage market came about.

GE has been in and out of the energy storage business for almost a century, starting with our involvement in early automotive batteries.  GE offered consumer batteries through the 1960’s, but exited that business.

It was around the millennium when we identified a growing need for industrial batteries. As market leaders in locomotive production, we were constantly seeking for ways to differentiate ourselves and stay ahead of the competition. We were seeking to “hybridise” locomotives, doing the equivalent of what Prius did for cars.  If, by hybridising a locomotive, you can save 10% of fuel consumed you have a game-changing technology. The transportation market was very hot until the world economic markets crashed, leading to a slowdown in locomotive sales, but by that time we’d done a lot of the R&D to get into energy storage.

We also purchased Beta R&D located near Derby, UK - fourteen guys who had developed technology for commercial energy storage since the late 1960’s - we saw them as having the expertise to commercialise the technology. From late 2007 to 2009 we did a lot of work to understand the potential of the technology, layout the business plan, and determine the markets we wanted to be in.

Stationary energy storage solutions in telecom backup power and industrial applications both needed the same ruggedness, abuse tolerance, deep cycling and long life as was needed in transportation. So we found there was demand for advanced energy storage solutions in those markets, which stimulated the company to invest in energy storage.

GE decided to bet big on batteries - investing US$150 million to incubate and commercialise the new technology, effectively creating a startup within the company. The resulting business, GE Energy Storage, is focused on delivering Durathon products, which offer a safe, reliable and cost effective option for a broad range of industries and uses. This is what GE does throughout its businesses: marrying best-in-class technology with deep market insights to bring innovation to market, on a large scale.