Power

Reliable, maintainable, expandable power: 12 kWh a day, year round, with plug-and-play simplicity.

6 x 550 Wbifacial panels, 3s2p

4.8 kWhLiFePO4 battery

3 daysof autonomy in critical mode

$33,887of a $60,000 budget

Budget: $33,887 of $60,000, $26,113 under. Power: 4.22 of 6 kWh a day.

Sebastien Pruneau Team lead

Power lead. System design and the mechanical room

Mechanical and electrical double major. Led his EE senior project.

60 Winverter idle

1.1kWh a day critical load

41.8°panel tilt

Chose the architecture: a Sol-Ark hybrid inverter, LiFePO4 storage and ground-mounted bifacial panels.
Built the appliance list and the shared energy budget with mechanical.
Caught, after midnight on PDR night, that inverter idle draw alone was eating 2 kWh a day.
Defined critical mode: the inverter drops out and the essentials run on DC at about 1.1 kWh a day.
Turned the panels sideways to clear the 30 in code height at a 41.8° tilt.
Set up the Revit central models and drew the mechanical room and wiring sheets.

In the chatWhat if we mount the panel sideways. Now the sin^-1(30"/45") = 41.8 degrees?

Apr 21Argued down the auto-start generator: if it fires at low battery, there is no point in critical mode.

CodesNEC 110, 240, 250, 300, 310, 411, 480, 690, 694, 705, 706, 708, 710

Array and battery sizing, wind study, quotes

Interned on turbine generators and presented designs every week.

3,220 Warray peak

15.9kWh on an average day

3 daysautonomy

Sized the array from 12 kWh a day, 4.84 peak sun hours and a 0.77 derate: six Axitec 550 W bifacial panels, 3s2p.
Sized the battery for three days of critical load: one 48 V 100 Ah EG4.
Modeled a wind turbine from four years of NREL wind data, then recommended dropping it for two more panels.
Built the month-by-month production table and flagged December as the one tight month.
Collected the solar and wiring quotes and compiled the NEC 690 code list.
Ran a shading study after the final presentation and sent it to the professor anyway.

In the chatWhy are days of autonomy the hardest part of all of this 😭

Apr 18Proposed scrapping the $20,000 turbine and adding panels. Josiah agreed the same day.

CodesNEC 690, 240, Cass County Section 16, UL 1703

Array siting, lighting, receptacles and wiring

Thousands of LED retrofits and three years beside licensed electricians.

29LED fixtures

0.448kWh a day lighting

17.5 ftarray setback

Sited the array west of the house, 17.5 ft out and unshaded after 10:30 AM.
Lit the whole house with 29 CLEANLIFE 48 V wafer lights at 800 lumens and 6 W each.
Got lighting down to 0.448 kWh a day, against a typical home's 3.
Laid out GFCI, tamper-resistant receptacles and 20 A kitchen circuits to NEC 2023.
Added a 300 W mini inverter so the UV filter, hydronic pump and one kitchen outlet stay live in critical mode.

In the chatI don't want cheapo lights but we can't be dropping $100 one fixture

Mar 13At 3:44 AM on PDR night, worked out the first panel spot would get under 2 hours of winter sun.

CodesNEC 110, 210, 406

Sol-Ark hybrid inverterCharger, battery manager and inverter in one box with a screen a family can read.
Critical DC modeAt low charge the inverter shuts itself off. Fridge, lights and water keep running on DC.
One EG4 48 V 100 Ah batteryThree days of the 1,100 Wh critical load needs 90 Ah.
Six ground-mounted bifacial panelsEasy to clean, and they catch light off the ground too.
Manual-start generatorA backup for the backup. Auto-start would make critical mode pointless.
48 V DC lightingRuns straight off the battery, no conversion losses.

~~Wind turbine~~Cass County requires an AWEA-certified unit, about $20,000. Two more panels instead.
~~12 panels and a 32 kWh bank~~The PDR design, oversized once critical mode was defined.
~~Roof-mounted panels~~Harder to service, and it wastes the bifacial gain.
~~Lead-acid batteries~~Short life and shallow discharge.

Solar productionHouse demandWh on a typical day

Table