Probably the most important trend in off-grid inverters is the end of single-application off-grid inverters as we know them. More precisely, the category will become dominated by solar inverters that go beyond off-grid operation through a two-stage evolutionary process: convergence of features and technologies into a single unit, and divergence of applications and energy flow to cover a much wider range of needs as residential and commercial power demands also evolve.
Most of today’s typical off-grid inverters are already multitaskers: combination inverter/chargers with bi-directional energy capabilities to convert DC to AC and AC to DC. This allows the inverter to manage PV or other energy sources while also maintaining battery storage. Until recently, the rather clean-cut separation between off-grid systems (mainly for providing power in remote or stand-alone applications without grid access) and grid-tied systems (mainly to supplement utility power for economic reasons) made it easy to segregate solar inverters into two related classes, with little or no overlap between them.
All that is changing with the ascendance of renewable energy sources from niche to mainstream. In many parts of the world, renewable systems are not a green-living socially-motivated luxury but the only means of supplementing weak or non-existent grids with life-improving power. Renewable energy sources are a critical part of the development portfolio of emerging economies, with India as a prime example. While a patchwork quilt of local grids collapsed in headline-making news this past summer, that country’s relatively new wireless telecom infrastructure hummed along powered by locally deployed systems using sealed solar inverters—and some facilities (such as the Malankara Tea Plantation, a historic building converted into one of that country’s first net-zero office buildings, now running off-grid on solar equipment) carried on with business-as-usual while the rest of the country suffered in the dark.
With renewable systems expected to make a greater contribution to conventionally-fueled power grids of every size and type, increasing network complexity will dictate a startling transformation for both off-grid and grid-tied inverters—to the point of combining the best attributes of both into next-grid inverters. While it would take a lot more space to put together an all-inclusive list, here are some of the functions that the next-generation inverters will need to address in order to make a meaningful contribution to an increasingly complex energy world:
Generator: We often joke that the real competition to an off-grid inverter is a generator. Next-gen inverters will continue to have more sophisticated generator functions, capable of auto-starting, stopping and controlling them either to stand in for the grid or augment renewably generated electricity. If a downed grid does not come back up, for example, the inverter in off-grid mode would use both generator and renewable energy sources to run loads instead of running down batteries. Even without renewable energy, an inverter/generator combination is a significant gain in efficiency for a system. If the generator runs loads part of the time, it can simultaneously charge batteries so that the inverter can run those same loads later—without a corresponding increase in fuel usage.
Backup: Both stand-alone and interactive systems will need to protect and manage the expensive battery banks upon which they operationally depend. Next-gen inverters will increasingly provide safety features such as low voltage disconnect, as well as monitor and adjust for battery temperature compensation and other parameters. In locations with computers and other sensitive loads, the value of inverters that can switch between on-grid and off-grid operation seamlessly is obvious.
Support: Some scenarios involve chronic supply problems, such as weak local grids, inadequate local generators, or both. Next-gen solar inverters with battery backup will make all the short-term decisions necessary to balance available sources and maintain stability.
Offset: An inverter capable of energy divergence (managing multiple sources and directional flows) is capable of sending excess energy downstream to run loads after storing up all the DC the system can handle, in lieu of selling energy upstream back to the grid if that is limited by local regulations. In places such as Hawaii, with both high electricity costs and limited sell-back options, the ability to put every bit of renewable energy to work is invaluable.
Minigrid: In systems with sufficient renewable energy, this inverter function (also called HBX/high battery transfer) is really the inverse of a backup system. Here, the batteries and renewable sources are the primary electricity source and the grid is a distant secondary, mostly used for conditions when renewable energy is in short supply. This means that in such a system, an inverter may be an off-grid type up to 90% of the time, but capable of switching over as conditions warrant.
Features previously considered the exclusive territory of off-grid inverters will become increasingly common in grid-tied systems. As more people realize the benefits of combining off-grid independence with grid-tied economics, multi-talented hybrid inverters capable of operating in multiple modes will become more standard at the center of energy systems, relegating single-purpose off-grid and one-trick-pony grid-tied inverters to niche applications and cost-driven installations.
By: Senior Marketing Manager Mark Cerasuolo and Technical Writer Ken Ripley at OutBack Power