Promethean Homes is proud to announce that we recently started construction of our first zero energy house. Like all of our projects we will build this one in a cost-conscious and energy-efficient manner. However, this house will feature two additional systems designed for resiliency: an islandable PV array and a small wood burning stove.
Islandable PV System
So, let's ignore the question that's nagging you right now (is islandable even a word?) and move onto describing an islandable PV system.
Simply stated, an islandable PV system provides the benefits of a grid-tied system AND an off-grid system. During normal operation the PV system will sync with the electrical grid to provide electricity to the house.
When the grid is operational the PV system will feed electricity to the house AND to the electrical grid. When it produces more electricity than is consumed by the household that electricity will be fed back into the grid (to be used by neighboring houses and businesses). When it produces less electricity than is consumed by the household that deficit will be supplied from the grid.
But what happens when the grid goes down? In a standard grid-tied PV array the system disconnects from the grid and shuts down. This is a safety feature that prevents electricity from backfeeding the grid (which could potentially injure those people working to repair service lines or components).
An islandable PV system works in conjuction with a battery bank to supply power to the house while the grid is down. Key circuits will remain active:
- Well Pump
- Refrigerators and Freezers
- Lighting Circuits
- Dedicated Outlets
It works much like a whole-house generator. The controls disconnect from the grid, but then restart to supply power to just the house. Unlike a whole-house generator this system will produce power with ZERO noise.
Although the house will be equipped with two Fujitsu slim duct heat pumps, it will also feature a small cast-iron woodstove. The owner will be able to heat the house during a power outage---using a locally sourced biofuel.
This woodstove will be connected to a dedicated outdoor air supply. This will prevent the woodstove from depressurizing the house; it will also ensure that the appliance does not backdraft.
In addition to the resilience provided by this woodstove, let's not forget comfort and ambiance. The high-temperature radiant heat from a woodstove is nearly impossible to match.