chrisjx
New Member
My first shot at trying to design an off grid system for a new house near Brenham Texas.
In my existing home, I use about 19kWh/day. It is a small house with no AC, only gas heating. Also gas stove and gas clothes dryer. The biggest draw in the house is a home lab server system which draws about 400W continuously. In any case, this will be far a new house (2400 square feet) on 10 acres so low energy components will be favored and because space is not a problem, we plan to set up the array on a ground mount system. I've set the sizing to support 30kWh per day and perhaps that's a first problem but it's what I've calculated so far.
What follows is a very basic overview of the primary requirements and some components I think will be required and some generic prices I've pulled from the internet. No manufacturers defined yet. I know I'm missing some of the smaller items like breakers and bus bars but I need to get this out to some people with experience and see if I'm even on the right track, regardless of how accurate I am in this first pass.
Any tips or advice appreciated.
Location and Requirements
- Average Daily Usage: 30 kWh
- Days of Required Autonomy: 3
- Location and Solar Irradiance: 30.15, -96.46 - open field, no trees
- Soil Analysis: Dark clay soil
Components and Pricing
- Solar Panel Type: Mono-crystalline panels, 400 Watt each = $400
- Charge Controllers: 3200W/48V = $300
- Battery Type: Lithium-phosphate batteries, 10kWh each = $1800
- Inverter: 6000W = $1600
- Ground-mounted Racking: Aluminum or galvanized steel = $8000
- Single strand 2/0 AWG copper wire: $200 / 100 feet
Calculations and Design
# Expected Hours of Full Sun
- Average of 5 hours of full sun per day.
# Solar Panels and Strings
- Total Energy for 3 Days: (30 kWh/day times 3 days = 90 kWh)
- Energy Production Per Day: (90 kWh / 5 hours/day = 18 kW)
- Panels Required: (18,000 W / 400 W/panel = 45 panels)
- Optimal String Configuration: 5 strings of 9 panels
- Total Cost for Panels: (45 times $400 = $18,000)
# Charge Controllers
- Controllers Needed: 5 (one per string)
- Total Cost for Controllers: (5 times $300 = $1,500)
# Inverters
- Inverters Required: 2 (for resilience and 240VAC capability)
- Total Cost for Inverters: (2 times $1600 = $3,200)
# Breakers
- Breakers for Panels: 5
- Breakers for Inverters: 2
# Cabling
- Distance to Inverter: 60' underground
- Wire Required: 2/0 AWG copper wire (60 feet)
- Total Cost for Wiring: ( frac{60}{100} times $200 = $120)
# Batteries
- Batteries Required: 9 (to meet 90 kWh for 3 days)
- Total Cost for Batteries: (9 times $1800 = $16,200)
# Tilt & Orientation
- Fixed: 30 degrees
- Tilt for Winter: 40 degrees
- Adjustment Dates: October 15 to April 14
- Tilt for Summer: 20 degrees
- Adjustment Dates: April 15 to October 14
- Orientation: South facing
# Ground Mount and Foundation
- Material: Aluminum or galvanized steel
- Total Cost: $8000
Summary
- Total Solar Panels Cost: $18,000
- Total Controllers Cost: $1,500
- Total Inverters Cost: $3,200
- Total Batteries Cost: $16,200
- Total Ground Mount and Foundation Cost: $8000
- Total Cabling Cost: $120
# Total System Cost: $47,020
In my existing home, I use about 19kWh/day. It is a small house with no AC, only gas heating. Also gas stove and gas clothes dryer. The biggest draw in the house is a home lab server system which draws about 400W continuously. In any case, this will be far a new house (2400 square feet) on 10 acres so low energy components will be favored and because space is not a problem, we plan to set up the array on a ground mount system. I've set the sizing to support 30kWh per day and perhaps that's a first problem but it's what I've calculated so far.
What follows is a very basic overview of the primary requirements and some components I think will be required and some generic prices I've pulled from the internet. No manufacturers defined yet. I know I'm missing some of the smaller items like breakers and bus bars but I need to get this out to some people with experience and see if I'm even on the right track, regardless of how accurate I am in this first pass.
Any tips or advice appreciated.
Location and Requirements
- Average Daily Usage: 30 kWh
- Days of Required Autonomy: 3
- Location and Solar Irradiance: 30.15, -96.46 - open field, no trees
- Soil Analysis: Dark clay soil
Components and Pricing
- Solar Panel Type: Mono-crystalline panels, 400 Watt each = $400
- Charge Controllers: 3200W/48V = $300
- Battery Type: Lithium-phosphate batteries, 10kWh each = $1800
- Inverter: 6000W = $1600
- Ground-mounted Racking: Aluminum or galvanized steel = $8000
- Single strand 2/0 AWG copper wire: $200 / 100 feet
Calculations and Design
# Expected Hours of Full Sun
- Average of 5 hours of full sun per day.
# Solar Panels and Strings
- Total Energy for 3 Days: (30 kWh/day times 3 days = 90 kWh)
- Energy Production Per Day: (90 kWh / 5 hours/day = 18 kW)
- Panels Required: (18,000 W / 400 W/panel = 45 panels)
- Optimal String Configuration: 5 strings of 9 panels
- Total Cost for Panels: (45 times $400 = $18,000)
# Charge Controllers
- Controllers Needed: 5 (one per string)
- Total Cost for Controllers: (5 times $300 = $1,500)
# Inverters
- Inverters Required: 2 (for resilience and 240VAC capability)
- Total Cost for Inverters: (2 times $1600 = $3,200)
# Breakers
- Breakers for Panels: 5
- Breakers for Inverters: 2
# Cabling
- Distance to Inverter: 60' underground
- Wire Required: 2/0 AWG copper wire (60 feet)
- Total Cost for Wiring: ( frac{60}{100} times $200 = $120)
# Batteries
- Batteries Required: 9 (to meet 90 kWh for 3 days)
- Total Cost for Batteries: (9 times $1800 = $16,200)
# Tilt & Orientation
- Fixed: 30 degrees
- Tilt for Winter: 40 degrees
- Adjustment Dates: October 15 to April 14
- Tilt for Summer: 20 degrees
- Adjustment Dates: April 15 to October 14
- Orientation: South facing
# Ground Mount and Foundation
- Material: Aluminum or galvanized steel
- Total Cost: $8000
Summary
- Total Solar Panels Cost: $18,000
- Total Controllers Cost: $1,500
- Total Inverters Cost: $3,200
- Total Batteries Cost: $16,200
- Total Ground Mount and Foundation Cost: $8000
- Total Cabling Cost: $120
# Total System Cost: $47,020