Page 70 - North American Clean Energy March April 2016

energy storage
70
MARCH/APRIL 2016
nacleanenergy.com
Energy Storage
New technologies
address obstacles to
system deployment
by John Merritt
e energy storage industry is growing rapidly as new technologies develop, markets expand, and new applications have the potential to provide greater bene ts to end users. As this dynamic corner of the energy industry comes into its own, new obstacles to deployment continue
to arise. A number of considerations must be taken into account, like broadly varying regulations and standards, as well as overall system design a ecting cost, logistics, interconnection, and the ease of energy storage system deployment. Considering these factors when designing or integrating a battery energy storage system can potentially save energy storage system companies, installers, integrators, facility owners, and other end users headaches in the long run.
System design
Reduced footprint
A key part of the cost puzzle for energy storage is the size and weight of the overall system. Currently, lithium-ion batteries are the incumbent technology because they have a high power density and a small footprint. While there are alternative battery chemistries, lithium-ion remains the most viable for behind-the-meter Commercial and Industrial (C&I) applications where size is an important equipment siting consideration. What remains, then, is the power converter. Advanced power conversion systems are not only more e cient, but dramatically smaller and lighter as well, providing signi cant logistical and cost advantages.
High e ciency
Energy storage presents a unique challenge in that its applications are inherently bi-directional, AC to
DC and DC to AC, making an energy storage system more complicated than its PV inverter counterpart which operates in only one direction, DC to AC. In systems designed with conventional power electronics, magnetic components contribute to signi cant power losses. For example, average round-trip losses created by transformers and line reactors are roughly 5 percent, resulting in typical system round-trip e ciencies of 90 percent or less.
Advanced power conversion technologies, particularly those with high nameplate e ciency ratings, greatly reduce round-trip power losses for energy storage systems. Due to lower conversion losses, energy storage systems based on transformerless power converters require about 10 percent less electrical power input and 5 percent less battery capacity to generate the same energy output. Over time, this increase in e ciency results in accelerated energy storage system payback.
Differentiators
Multiple value streams
e ability to incorporate multiple value streams can dramatically accelerate storage system payback, compared to equipment supporting a single application, such as peak shaving/demand management. ose value streams can bene t both the commercial customer and the local utility. Hundreds of commercial-sited storage systems were deployed in California in 2015, and the vast majority of those
targeted a single value stream: demand management. Going forward, the industry is expected
to embrace a broader set of storage applications, including backup power/critical load support, improved facility power quality, and self-consumption which directly bene t the building owner/operator. Volt/Var features will also be added, bene tting the utility. Monetizing just two or three of these emerging value-streams can dramatically impact return on investment (ROI).
PV + storage
Integrating PV with energy storage utilizing an advanced multiport power converter, compared to the incumbent approach of using separate stand-alone converters for PV and the battery, provides additional value. ese multiport converters can support critical loads in a building using solar as the primary energy resource during grid outages and natural disasters, a capability PV inverters and most energy storage converters installed to date cannot deliver, as demonstrated by superstorm Sandy. Managing separate power converters is a daunting real-time backup power control
and management challenge which is eliminated by the use of an advanced multiport (AC/DC/DC) converter architecture. e costs of these multiport systems are rapidly declining and are already competitive with the 2-converter solution noted above.
Smart inverter features
Advanced power converters must support a broad range of new capabilities to support emerging smart grid requirements. Both California and Hawaii are on the forefront of this e ort, and industry groups such as the SunSpec Alliance and Modular Energy Storage Architecture (MESA) have published open control and monitoring standards to further accelerate the adoption of energy storage.
Logistics
Shipping, siting, and installation
e rst bene t to the form factor reduction in power conversion systems is dramatically lower costs associated with shipping and installation. Conventional power conversion systems can easily weigh six times that of the newest transformerless technology. Compared to a 30kW system weighing less than 100 pounds, a 650-pound piece of hardware is at a great logistical disadvantage. Conventional systems incur high shipping costs due solely to size and weight. A system of this size requires more dedicated space, limiting siting exibility, and possible oor re-enforcement, whereas a sub 100-pound system is wall-mountable, and easier to ship, install, and integrate into the rest of the energy storage equipment package.