There is a shortcoming with grid-tied photovoltaic (PV) energy systems of which owners are often unaware until an emergency: Although grid-tied systems can save money and earn their owners incentives while the sun is shining and the utility power grid is up, they must disconnect when the grid is down during an outage, leaving unused solar electricity sitting on the roof. As a safety feature within generic grid-tied systems, when the grid is down, users can neither sell energy back to the utility, nor supply their homes or businesses with power per the UL-1741 safety requirement.
Luckily, there is an upgrade for these types of systems called AC coupling that enables one to store energy for use during power outages and emergencies. AC coupling added to a simple grid-tied system converts it to a grid-interactive or Grid/Hybrid type system, providing grid-tied savings when the grid is up and off-grid independence and security when it is down or compromised.
Figure 1– Single line diagram of an OutBack Radian inverter AC-coupled to a grid-tied inverter
1) What elements are in an AC-coupled system?
Although there are several approaches to AC coupling, the systems have some common elements including:
Figure 1– Single line diagram of an OutBack Radian inverter AC-coupled to a grid-tied inverter
1) What elements are in an AC-coupled system?
Although there are several approaches to AC coupling, the systems have some common elements including:
- A grid-interactive or Grid/Hybrid inverter/charger;
- An energy storage system for back-up power consisting of batteries and an enclosure;
- A coupling device or center to tie the new system into the existing grid-tied one; and
- Additional electrical wiring with a second panel for critical backed-up loads that the new energy system’s back-up power capability will support in the event of an outage.
- Dynamic stability: provides clean signal to the inverter, ensuring the inverter stays online and keeps producing power.
- Universal design: makes sure the inverter/charger works with other brands of string inverters.
- Dual AC inputs: allows charging of the energy storage system (batteries) from a backup generator in the event of an extended power outage or when the sun isn’t shining.
- Split-phase design: enables easy integration into standard household wiring, eliminating the need for expensive and inefficient transformers.
- Generator input and protection: protects backup generators from back-feed overload when the PV array is charging.
- UL1741/IEEE1547 ratings: ensures system compliancy by accurately detecting “islanding” conditions and disconnecting from the grid to prevent harm to utility service workers, as required.
0 comments:
Post a Comment