10) Tesla Battery- The Heart of the SunCottage
Energy storage is critical to the SunCottage's mission of self-sufficiency. Without it you're at the mercy of the sun, or the night, or clouds... A battery can store sunlight for use when you need it.
The first question in the subject of batteries is how much storage do we need? And the first answer is, enough to handle a power outage. In rural Vermont we experience probably 10 outages per year. Mostly due to storms and fallen branches. The normal duration is probably 3 to 4 hours.
Occasionally we have outages of a day or more. In major ice storms some locations have been without power for a week. So it's our belief that a battery that can provide 2 days of power to run the basic systems would probably be adequate. We can always hunker down and cut things to the bone during those occasional storms of the decade.
While we intend to heat the SunCottage geothermally, it's always prudent to have a back-up system. To meet this need we plan to install a pellet stove that uses renewable energy in the form of wood pellets. Pellet stoves still require electricity to run the auger that feeds the pellets into the burner, but the energy consumption is minimal, our planned for battery should be able to handle it.
The point is that in a prolonged power shortage, or if we should decide to go off-grid, the cottage will have to move to pellet mode. Given that we expect the normal daily energy consumption will be 7 kWh, and we'd like to have a minimum of two days energy storage, we're looking at a battery with a capacity of ~14 kWh. It turns out that there is a perfect candidate: The Tesla PowerWall 2. A battery that beats the pants off the competitors for price and capacity:
The beauty of the Powerball 2 is that should it's capacity be insufficient, it's completely feasible to add an additional one, and double your safety factor. A luxury or a prudent decision? I can't help but recall my brother's story about the week long power shortage in Connecticut a few years ago, where many of his neighbors fled to far-away places where the grid was still up. He was tasked with emptying all their refrigerators before the food rotted, he made out like a bandit. It was like an episode out of the Walking Dead. It pays to have a generator or a big enough battery.
Here's a graphic of the system from SolarEdge, the inverter company whose systems are Tesla integrated:
Notice how you wire your system to power critical systems during low use situations, ensuring that refrigerators, heating, communications and lighting are backed up, while non-critical appliances like dishwashers and washer/dryers are sidelined.
