Objective
• Powering a self-sufficient combination workshop / living structure designed to provide preparedness for natural and other disruptions
Benefit
• Comfort and security of a self-sufficient structure ready for harsh duty and extended off-grid autonomy
While the theory of envelope design is proven in simple , smaller home construction , this project was more than a house : it also included a 2-bay garage and a working shop area as well as living quarters . To achieve the project ’ s ambitious design and self-sufficiency goals , Marshall Contracting ’ s Kent Marshall knew two things .
First , he ’ d need to modify the envelope design principle to fit a unique structure to achieve passive solar heating , which he did by designing the home around an integral greenhouse structure on the “ warmer ” south side with warmed air circulating through a ceiling return to the north side and downward into a concrete “ thermal collector ” for heat storage . And second , he ’ d need to come up with equally innovative methods to provide for water and electricity for the home — and in fact solar energy with large-capacity electricity storage provided the means for both of those as well .
Solution
Kent turned to Sustainable Laramie ’ s Jim McGrath , maverick engineer and solar designer who enlisted the help of OutBack Power ’ s tech support group for an all-in-one solution . Jim worked with the project ’ s electrical contracting firm Voltech Electric to configure and install an off-grid electrical system that could power a 240V deep well water pump designed to supply 500 gallons of water per week , plus large-capacity freezers and other refrigeration , a working shop , two large automatic garage doors , and finally a complete , self-contained back-up living quarters with lighting , microwave , 16-head automatic sprinkler system to maintain an aesthetic blanket of green grass around the structure , and other amenities . The entire system had to be contained inside the structure to protect it from temperature extremes .
To harvest , convert and store the output of the PV systems twelve 250W solar panels generating 6kW hours / day , Jim selected an OutBack FLEXpower TWO with twin 3524 inverter / chargers as the heart of the renewable energy system , and to achieve the home ’ s autonomy requirement of remaining off-grid without using a generator upgraded the energy storage system to the OutBack EnergyCell 2700RE-24 battery bank , which consists of twelve large 2V batteries connected in series to form a 24V high-capacity bank . Complete with plexi-shielding and structurally sound UBC steel racking , this battery bank can store 54.9kWh nameplate energy storage safely and securely .
“ This upgrade gave us the storage capacity and high cycle-life needed to meet the project ’ s power requirements ,” explains Jim McGrath . “ And the battery bank had the right mix of safety features , construction quality , and ‘ fit-and-finish ” necessary to enable it to ‘ live inside ’ the structure without causing the owner any anxiety whatsoever about sharing a close-quarters living-space with big batteries . This system is literally right at home .”
With the innovative home undergoing its first trials during the upcoming winter , McGrath and Marshall are confident it will exceed the owner ’ s expectations . “ We may add wind power later ,” noted McGrath ,” but even when it ’ s minus 20 degrees outside everything should be able to avoid freezing and the living quarters remain tempered based entirely on what the sun — augmented by OutBack technology — can provide .”
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Energy Storage eFeature | January 2015