Self-Consumption PV Systems: Page 3 of 10
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The necessary components are a traditional grid-tied PV inverter with open communications and the ability to control power via communications, a power meter at the utility point of interconnection, and a system controller that communicates curtailment signals to the PV system based on the meter measurements. I am not aware of any US equipment specifically certified for nonexport as there is no applicable US certification standard.
—Kent Sheldon, vice president of technology, Greensmith Energy Management Systems
Outside the US, SMA provides the Sunny Home Manager system, which incorporates the required power curtailment control function. Combined with the SMA Energy Meter for grid connection point measurement, the system complies with common requirements in Germany, Australia and some other European countries. The new generation of SMA inverters are compatible with the SMA Energy Meter and do not require the Sunny Home Manager. The SMA Energy Meter has the same regional availability as the Sunny Home Manager. SMA energy management systems will enter the US market in the future. Hawaii has announced regulation for customer self-supply with zero export, and the exact rules are in development. We expect other jurisdictions to follow in the future.
—Martin Volkmar, SMA Solar Technology
What additional components and software are required for nonexport or curtailed residential PV systems with energy storage?
Is this equipment certified and available in the US market?
What are the basic modes of operation for these systems?
There are generally two approaches for integrating storage into PV systems, whether for backup or for self-consumption applications. One is the new application of older, established technologies, which generally rely on two separate devices to manage either the PV or the battery bank. In ac-coupled systems, the two devices are inverters, one for the PV array and one for the battery bank. In dc-coupled systems, a PV controller regulates the battery charge, and an inverter uses energy stored in the battery to run loads. These systems have evolved over the last 10-plus years, primarily from the off-grid market, and have integrated increasing intelligence to meet the new demands of grid-tied applications. They have been available for many years.
What I find particularly exciting are the new generation of hybrid inverters that interface with both the PV array and the battery bank. These multiport inverters eliminate an entire piece of equipment and the associated cost of purchase, installation and maintenance. These advanced inverters must integrate the ability to change modes—from a current-source grid-following device to a voltage-source grid-forming device—based on the presence of the grid. This new generation of devices is either just entering or will soon be entering the US market. 2016 will be a big year for “Euro-style” self-consumption equipment.
—Wes Kennedy, Fronius USA
With intelligent connected energy storage and advanced inverters, JuiceBox stores excess energy and shifts it for use in the evening when PV generation is low and homes have the highest load. JuiceBox Energy is one of a handful of products that are certified for this application and already installed in the US.
—Neil Maguire, CEO and founder, JuiceBox
With a SolarEdge system, the integrator needs to install an energy meter and upgrade the SolarEdge dc-optimized inverter to a StorEdge inverter. These components are all certified. Once installed, the inverter runs in one of four modes of operation: self-consumption, load management, limited power production and, if there is a battery, storage.
—Peter Mathews, SolarEdge
I am not aware of any storage system specifically certified for nonexport as there is no applicable US certification standard. This is a major obstacle for the installation of self-consumption systems in the US. Without certified nonexport products, utilities may require that integrators install a certified reverse-power relay between the PV energy storage system and the grid. However, this is usually cost-prohibitive for residential systems ($6,000–$10,000 per relay).
—Kent Sheldon, Greensmith Energy Management Systems