The market for cleaner energy is an exciting one, with news about solar power modules and renewable power generation coming out every day. Amid that buzz, significant advances at the system integration level are quietly taking place. Battery-backed photovoltaic (PV) inverters are enabling grid-interactive systems that solve multiple challenges suffered by both off-grid and grid-tied applications. By overcoming the substantial reliability and flexibility hurdles the industry previously faced, grid-interactive PV systems are clearing the way for integrators to successfully complete high-end renewable energy deployments.
An all-or-nothing history with the traditional grid
Historically, clean energy systems have either steered clear of the traditional energy grid altogether, or tied themselves so closely to it that users lost the flexibility and choice they might have sought by adopting renewable power in the first place. Let’s look first at off-grid systems. These were the prevalent option among PV users in the early 2000s. In rural regions or locations where traditional utility costs were too high, users chose off-grid PV modules. As the only source of power, the inverters and conversion systems had to be steadfast in their reliability; if they faltered, there was no alternative energy source. Not surprisingly, off-grid users suffered frequent outages when weather conditions were poor. If those users were not able to bring in generators, they suffered the significant downside of off-grid power.
Tying one’s energy use tightly to the grid has its problems, as well. The high-voltage string inverters in grid-tied systems convert direct current from the PV modules to the alternating current of the utility, and then deliver that energy back to the grid. This is a less expensive choice for the user, but it’s also a less flexible one. By tying to the grid, the user gives up the option to switch to renewable energy if the utility has an outage. If the traditional grid goes down, the grid-tied system has to disconnect for safety reasons, too, leaving the user in a blackout without the option to shift to solar or other power sources.
An interactive energy option that benefits users
Grid-interactive PV systems give users the option to draw on the local energy utility when they need to and switch to renewable power when appropriate. These interactive systems protect the savings that come from lower utility costs and production incentives that grid-tied users enjoy. At the same time, grid-interactive PV systems deliver a better backup option when the traditional utility grid goes down. In an outage, interactive systems draw power from PV modules, generators, wind turbines or backup battery systems. Users can call on similar renewable energy sources for other purposes, as well. If they want to lower their energy costs and consumption, they can limit their grid use to moments when cleaner resources are unavailable.