Concepts behind the smart grid are growing to tackle an electric power grid system that has changed very little in the 130 years or so of its existence. There is ample room for modernization efforts, to say the least. An updated grid would better be able to take advantage of smart metering and manage data and information, and better able to optimize energy coming from a wider variety of sources.
But as the smart grid evolves, a significant challenge to incorporating renewable resources that are intermittent like wind and solar energies into the power system is the ability to store that energy. In this modernization effort, what better way to tackle this and others conundrums than with a 150-year-old DC technology?
The wet-cell battery, though based on an old design, is now souped up with advanced chemistry and loads of intelligence to deliver multi-megawatt capacities. And UniEnergy Technologies (UET), which makes a highly scalable, next-generation version of the wet-cell in its facility near Seattle, needed a highly scalable automated control system to go with it.
UET houses its Uni.Systems in standard 20-foot shipping containers to keep manufacturing costs low and keep them physically modular—stackable and easy to transport. Inside the containers are tanks circulating an aqueous vanadium electrolyte, plus electrode stacks, controls and electronics. The modular architecture of these massive batteries (one container full of electrolyte weighs 40 tons) makes it easy for users to add the capacity they need, scaling up in much the same way that data storage is added to today’s computer systems.
The batteries have several advantages, including no capacity fade, no flammable components and no risk of thermal runaway, and they are fully reusable and recyclable. They can provide near-instant energy response for various durations as needed—for short periods (milliseconds to seconds) to help regulate AC voltages and frequencies; for medium durations (minutes) to help solar farms deal with passing clouds; or for longer periods (hours) to help utilities shift bulk energy to optimize energy use, storing energy during generation peaks when grid loads are low and discharging the energy during load peaks.
Commercializing the vanadium electrolyte chemistry that UET licensed from the U.S. Department of Energy’s Pacific Northwest National Laboratory required creating a control architecture that’s as scalable as the battery itself, notes David Ridley, UET’s director of electrical engineering. “That way, if customers want to add another megawatt of capacity, no problem,” he says. “Our controls needed to scale easily, so that once we deliver another container and hook it up, we could just increment the counter in our software by 1 MW and the customer is up and running.”
UET also wanted to keep everything as simple as possible to ensure availability and serviceability for its customers. “Of course, for our service business to be profitable, we need to minimize service calls by maximizing uptime and, if problems occur, be able to troubleshoot and fix them remotely as much as we can.”
The solution that UET settled on was to integrate key components from the Siemens Totally Integrated Automation (TIA) portfolio, including software engineering via the TIA Portal, and Siemens WinCC SCADA software and small Siemens variable-frequency drives. “What really stood out about Siemens is its full-line capability. It has everything from PLCs to I/O to industrial computers to HMIs, plus a full line of SCADA software,” Ridley says. “Plus it has variably-frequency drives, circuit breakers and power supplies, motor starters and other gear. And then there’s the fact that its huge energy division is involved with large-scale utility projects all over the world.”
The TIA Portal, Siemens’ software engineering framework, was also key to UET’s decision. “The TIA Portal’s code libraries handle things like communication protocols, distributed I/O, interfacing with the drive for our pumps, so we don’t have to spend precious time doing so,” Ridley says. “You drag and drop the code, and hardware is automatically configured. Assign it an IP address and it’s ready for your code.”
Hundreds of Siemens customers have been able to take as much as 30 percent off their development and commissioning times with TIA Portal—some customers, up to 60 percent. “With the TIA Portal and the Siemens TIA control platform, we can forget all the protocols, drivers and memory management issues that we’d have to code, then compile, test, debug, recompile and on and on,” Ridley says.
The Uni.System’s control and electrolyte pumping systems were built with several Siemens components, including the Simatic S7-1500 PLC, Simatic WinCC open-architecture SCADA, Simatic Comfort Panel HMI, and Scalance X-200 Profinet industrial Ethernet switches. Two Sinamics G120 variable-frequency drives are used in each 20-foot container to drive the electrolyte pumps, enabling the optimization of the electrolyte’s flow and therefore its efficiency. Simatic ET 200SP distributed I/O lets UET use the same I/O for all of its analog and digital connections. “We’re able to use the same type 20-foot box over and over again, which leverages our manufacturing efficiencies,” Ridley says.
Ridley estimates that the Siemens solution helped UET cut its time-to-market in half. In addition to the time savings enjoyed when developing the Uni.System, he also expects that the plug-and-play scalability of the Siemens control system will help reduce site-specific engineering costs to less than 10 percent of a customer’s project costs. “With other large-scale battery systems, onsite engineering can be from 30 to 50 percent of total costs,” he says. “But with the Siemens control system, we run just one Ethernet cable between the containers once they’re delivered and positioned on a customer’s site.”