Smart solar-and-storage solution poised to displace baseload power and decapitate the duck curve

By on August 4, 2017
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I have a few predictions: Solar-and-storage will replace all solar-only system builds within a few years. The notorious Duck Curve will be decapitated, and baseload will cease to be part of the conversation. Our generation will redefine baseload and energy distribution with a renewably energized, long-duration storage-enabled grid.

Why do I make these bold claims? Because we are sitting on the cusp of a major disruption in the energy sector. For the first time, we have the technology to truly integrate solar, wind and hydro with long-duration storage and intelligent, grid-friendly control systems. It’s time to change the conversation from low-hanging use cases like demand charge reduction to the ultimate goal of providing reliable 24/7 power and strengthening the transmission and distribution infrastructure with nothing but solar and other renewables harvested, stored and deployed.

When we issued our initial request for proposal (RFP) under the title “Decapitate the Duck” and started our due diligence of energy storage, inverter and software options to pair with our solar trackers, we were technology agnostic. We had no skin in the game in any one storage technology, and were focused on finding the best solution for our long-duration, DC-coupled storage vision.

We also sought a software-centric, DC-coupled inverter that was smart and adaptable. Finally, we were looking for a more holistic energy management system (EMS) software platform that would tie together the entire system in a fully integrated way, and help us understand how to play in the energy aggregation markets and learn when a kilowatt-hour is most valuable.

During our evaluations of more than 40 storage alternatives, we looked at many variations on lithium ion to flywheel to flow, as well as a host of software providers. We set our targets aggressively high by looking for a solution that was free of limitations prevalent with many technologies. Limitations characterized by mindsets like “can you use it and how much are you allowed to use it” and quantifying “are you using it in such a way that you’re keeping the product stable, so that it can be used for a long time.” We wanted a storage technology that had 100% depth of discharge (DoD), little or no degradation, little or no safety issues, low lifetime costs, inherent thermal management properties, and a 30-plus-year lifetime without regular augmentation. A storage component that worked the same on day 1 as it did on day 10,000.

It soon became apparent that vanadium flow (VF) batteries met all our visionary requirements and more. Our partner and colleague Matt Harper of Avalon Battery explained many of the advantages of VF batteries in a previous blog entry. As of early August, the Avalon VF battery we’ve been testing has seen an equivalent of 6.5 years of use at 100% DoD, and we still cannot measure any degradation of the system. The only O&M that has been needed is a single filter replacement.

A third-party report from Fire Captain Matt Paiss of Energy Response Solutions shows that vanadium flow faces far fewer safety issues, fire and otherwise, than other technologies. It highlights vanadium’s thermal mass as a key safety driver, where thermal runaway is not an issue and you don’t need a separate AC system, which can experience more than 20% parasitic losses just to cool the system. As far as we know, this combination of intelligent EMS software and a long-duration, DC-coupled system is unique in the storage space, and we believe the whole conversation around large distributed generation and utility storage needs to change.

Another essential part of our solar-and-storage vision has been to create a fully integrated and optimized system, one that comes out of a unified RFP rather than one spread among all the various components. A system that would arrive at the solar farm owner’s site pre-commissioned as a single SKU, and could be easily installed only needing to connect PV DC and grid AC. A system that works on NEXTracker’s existing SCADA and Modbus networks, and runs with NEXTracker’s predictive analytics and O&M to ensure the longest lifetime of the power plant. A modular DC-coupled PV system that captures energy previously lost in AC-coupled systems to inverter clipping for use at the time of the owner’s choosing and highest return. A system that allows customers to focus on kilowatt-hours and reduced installation times instead of laborious component sourcing exercises, on maximizing performance instead of maintaining storage capacity. A system with the potential to provide harvested solar power after the sun goes down to the dawn of the following day.

It’s time to decapitate the duck. The Duck Curve is used to speak negatively about the solar industry, a way of saying there is “too much solar” on the grid. The real problem is the antiquated sources and methodology used for baseload, and the outmoded idea that ramping baseload up and down is inefficient, expensive and polluting. We should have control over when and where the power is transmitted and distributed on the grid. Let’s stop talking about baseload and the duck curve. Let’s redefine the discussion and move toward a flexible grid, one that harnesses clean, renewable energy intelligently paired with energy storage.