The City of Monte Sereno reviewed our photovoltaic solar panel installation and signed off on all the components that Real Goods Solar are responsible for. The one remaining component is a cover for the 200 amp electrical panel in the East Mechanical room.
Although the cover is required, there is no current flowing through our electrical system as we are not connected to ‘the grid’.
We were honored to have Bob Sobota and Eufermiro Cariaga from Schneider Electric, and Jim Laberty of Lighting Systems tour our project site today. Bryan met Bob Sobota when Bryan attended the C-Bus training course in Palm Desert in March 2011; Bryan had hosted Jim’s visits to our project site previously, and it was Eric Westphal and Jim that recommended that we engage Randall Whitehead Lighting Solutions to design the lighting throughout the house. Eufermiro and Bryan met for the first time today.
Bob works in the lighting controls division and Eufermiro is in the Juno Lighting Group. Jim Laberty is the local distributor for both C-Bus lighting controls and Juno lighting.
Changing Our System to 100% Micro-Inverters
Solar photovoltaic panel installations are new and evolving. One of the technology elements that is continuing to evolve is the inverter. Usually, an entire array of panels (or string of arrays of panels) are connected to a single inverter. The inverter takes the DC and converts it to AC.
For our installation, we changed the design from a mix of one string inverter (for 32 panels) and 16 micro-inverters, to 48 micro-inverters. Changing to all micro-inverters reduces the conductors (wiring), increases the efficiency of the electricity generation, and increases the safety of the overall system.
One of the challenges with micro-inverters is that not many people understand how these systems work. Liam Ryan, from Real Goods Solar, explained the details to Bryan.
Before Operating, Micro-Inverters Require a Connection to the Grid
Generally, when solar photovoltaic panels are exposed to sunlight they produce electricity. The panels create direct current (DC) electricity and that flows to the inverter. In the case of a micro-inverter, the transmission of DC is only a couple of feet as the micro-inverter is mounted to the panel. The micro-inverter then creates alternating current (AC) which is connected to the building’s electrical system.
Enphase micro-inverters are ‘UL-listed’ as they have been certified (tested and approved) by Underwriters Laboratories. Products certified by Underwriters Laboratories are identied with a UL Mark. According to Underwriters Laboratories’ web site:
The UL Mark on a product means that UL has tested and evaluated representative samples of that product and determined that they meet UL requirements. Under a variety of programs products are periodically checked by UL at the manufacturing facility to make sure they continue to meet UL requirements. The UL Marks may be only used on or in connection with products certified by UL and under the terms of written agreement with UL. In addition to these marks, UL also provides access to the marks required in a number of other key world markets.
Liam explained that the Enphase micro-inverters in our system cannot convert the DC current to AC unless the micro-inverter has recognized the 60 Hz wave form has been stable for five minutes. The 60 Hz wave form is present in the electrical grid throughout the U.S. and Canada. Thus, the micro-inverter cannot create AC current unless our system is connected to the grid.
In addition, Liam explained that the micro-inverters will stop creating AC current immediately upon losing recognition of the 60 Hz wave form. The software in the Enphase micro-inverters is what recognizes the 60 Hz wave forms and then controls the output.
Underwriters Laboratories has certified the Enphase micro-inverters that we are using.
Consequently, although we have our entire solar photovoltaic system built, installed and inspected, we cannot create electricity until we are connected to the grid. There is no electricity present in our system.