Here are three views of our construction site on a nice day in September. Otherwise, it’s been spring rains, summer rains, autumn rains – so far 2018 has been one of the wettest years on record here in the Mid-Atlantic region. The incessant rains have definitely slowed construction and limited solar output. But, nevertheless, our amazing team completed the house yesterday, about a week ahead of schedule! So now, we’re dealing with the paperwork, yard clean-up and grooming, and some landscaping.
Here’s the energy picture:
1) Solar and geothermal – and major insulation. Rains have severely reduced solar energy production, but on even partly sunny days, energy use has been balancing out this fall – and that’s with HVAC and hot water systems, the kitchen, and lighting all up and running! Energy efficiency is why this is working, i.e., 45 SEER geothermal heat pumps, immense 6” insulation, LED lighting throughout, and more – and all in spite of suboptimal orientation of our 50 SunPower panels, which are hidden from view on flat sections of the roof, see above pix.
2) Three Tesla PowerWalls. Still waiting, but Talbot County recently approved their installation, so hopefully won’t be long now. This house is on-grid, not off-grid. But still, we’ve sized our battery storage large enough to let us use all excess solar energy during evening peak periods and at night. Also, together with the solar panels, the PowerWalls will serve as our emergency back-up generator in case the house loses power (which hasn’t happened in the 19 months since we bought the property, as far as we know).
3) Electric cars. Once we’ve got our Use & Occupancy Permit and some furniture next week, we’ll move in (Yes!) and try charging the electric cars. Will charge them during daylight hours so they’ll be running on solar energy, versus PJM’s coal-dominated daytime energy mix. Then, on evenings after charging the cars, what happens depends on season – on winter nights, the house will probably need to use electricity from the grid, which at that point relies mostly on high-efficiency natural gas turbines; on summer nights after charging the EVs, we expect the PowerWalls will hold enough solar-generated electricity to make it till dawn without buying electricity.
What did all this cost, and will it ever pay back? How much carbon are we preventing from entering the atmosphere, and what’s our per-unit avoided cost of carbon? Will we actually be carbon neutral? Stay tuned. We’ll know once we’ve gotten a full year of operations under our belt. At that point, we’ll do the analysis and hope to present results at the November 2019 USAEE-IAEE North American Conference in Denver.
Meanwhile, another post will follow as soon as our batteries are up and running.