Welcome to the Smart ‘Fusion’ of Solar Trackers with Vanadium Flow Batteries

By on May 30, 2017
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Guest blog by Matt Harper, Avalon Battery

While lithium ion-based battery systems have received the lion’s share of energy storage news, there are other technologies such as vanadium flow batteries (VFBs) that not only have cost-effective, multi-gigawatt-scale potential, but also the ability to be intelligently integrated with solar power plants. As VFB producers, we believe that our technology provides commercial and utility solar owners a superior solution to the incumbent energy storage technologies. But we also realize that we can’t go it alone.

If solar and energy storage are to become viable replacements for traditional power plants, a truly intelligent integration of these technologies must take place deep within the individual components as well as via a software platform that connects, optimizes and manages each component. That’s why we’re excited to be partnering with NEXTracker on the NX Fusion Plus, the first truly integrated solar tracker and storage system, which combines industry-leading tracking, storage and inverter technologies, along with predictive smart control software, analytics and monitoring capabilities.

Why is vanadium a smarter choice than traditional lithium ion options? First, unlike lithium ion, VFBs are designed from the ground up to be durable assets as this recent Wall Street Journal article explains. One of their fundamental values is that they do not degrade over the life cycle of the system. The flow battery architecture allows the charge and discharge to take place entirely in the liquid phase. With conventional batteries, the electrodes degrade with each charge-discharge cycle, and the cells lose performance over time and must be replaced. VFBs, however, can essentially live as long as the solar plant they’re integrated with—30 years or more. Here’s a helpful chart from a recent article in Forbes of what I’m referring to:

VFB_LI_chart

VFB systems also have fewer components than competitive solutions and have a significantly lower cost of ownership than the incumbent technologies.

Here’s another way that VFBs are different from other batteries. Since the energy is stored in liquid, the batteries can effectively manage the heat that’s generated inside the battery during the charge-discharge cycle, thus preventing the possibility of accidental overheating and prolonging the service life. VFBs are safe: they are not susceptible to the thermal runaway reactions seen with lithium-ion batteries from time to time.

VFBs are also essentially application-specific storage systems. Because of the separation of the cells and electrolytes, the batteries can be designed for either power or energy apps. If you add more cell stacks, you increase the power; make the electrolyte tanks bigger, and you get more energy. With conventional batteries, the cells and electrolytes are contained in the same device, so you’re stuck with the power and energy locked into them.

This design flexibility comes into play when we look at the fully integrated NX Fusion Plus system. Both tracking and storage share a common goal: broadening and flattening the energy generation “shoulder” over the course of the day, so that the plant performance is optimized and the kilowatt-hour production is maximized. By combining solar and storage, we’re going to flip the traditional AC/DC ratio model on its head. Here’s a chart that demonstrates how our joint solution extends the life of solar on a given day.

NX Fusion Plus graphics-03_revised

While the usual approach has been to overdrive the inverter so that some of that DC power might be clipped in the middle of the day, the value of that lost revenue, those lost kilowatt-hours, is less than or equal to the marginal increase in cost of using a larger inverter. With batteries, we can pump up the DC side of the ratio further and use even smaller inverters. As the DC current from the array can flow directly to the battery, bypassing the inversion phase altogether any potential energy that would be clipped by a conventional inverter can be realized and stored in the battery. Not only is there the benefit of shifting the energy around with the battery to generate more revenue, but much of the balance of systems and associated labor costs on the AC side can be greatly reduced as well.

What really brings all this energy-harvesting capability together is the fully integrated system intelligence within the components themselves and across the platform of connected devices. As NEXTracker software guru Allan Daly explained in the previous blog, the company has made a big push into leveraging the intelligence of machine learning and smart connected sensors to  get data back to a central location, efficiently and at comparatively low cost.

We’re putting that same control intelligence into the battery itself. Rather than a system with thousands of batteries requiring the management of individual cell voltages, we’re looking at a small number of components—and potential failure modes—inside the battery that are key performance indicators, and we’re watching as that performance changes over time. We will be able to proactively do any maintenance work that’s required over the 30+-year lifetime of the system, long before there’s any degradation in performance. The ability to have this kind of intelligence and diagnostics is really beneficial with our particular technology. Listen to NEXTracker CTO Alex Au and VP Software Allan Daly in this video talk about the genesis of the software connection.

AD_AU Chat

We’re connecting the trackers, batteries and other devices together on an identical network using identical components, which will give us the ability to optimize and manage the performance and dispatch of those individual devices. Rather than solar-plus-storage, the NX Fusion Plus represents the first deeply integrated solar-and-storage system. The era of renewable baseload generation may be closer than you think.