The terrible weather conditions associated with Hurricane Sandy have made us all aware of the need to be self-reliant in the face of massive power outages. For most families, a standard grid-tie system is designed to be a supplement to your current electricity source (the Electric Company) but when the the grid is down, a grid-tied inverter is designed to recognize this loss and your solar system also shuts down. The reasons for this design feature are related to safety for the power company employees restoring power, and technical in that your PV system can not be counted on to deliver power at the level needed to protect household devices.
The alternative to standard grid-tie systems are systems that combine grid-tie functionality and then back up the grid with a high-tech battery system. The technical term for this system is bimodal ( two modes), grid-tie and also off-grid capability when the grid is down. When the grid is down, the inverter draws from the battery system and the DC electricity is converted to AC to power critical circuits that you have designated in your design.
In 2012 we have installed bimodal solar systems over much of West Virginia and can tell you that they truly are two systems in one — supplementing your household electricity when the grid is up, and providing an automatic, seamless transition to batteries when the grid is down. This was proven during the storms this summer when some customers were without grid power for more than a week, and also during the Hurricane Sandy recovery.
Bimodal system are more expensive, more complicated and technically challenging to install. But when you compare our bimodal systems with a standard grid-tie system and a generator system. the bimodal system wins — hands down in every respect.
Please contact us if you are interested in learning more about this technology. We can also put you in touch with existing customers who will give you first-hand accounts on the advantages of this system design.