Off-Grid Energy Systems II

Solar Generator Project

By Thomas Anderson

Syllabus

Course: Off-Grid Energy Systems II / Solar Generator
Instructor: Thomas Anderson
Location:
  • Greenly Center
    50 E Main St, Bloomsburg, PA 17815
Course Slides:
Goal:
  • Students will practice the principles of off-grid energy production by building a scale model self-contained "solar generator" system, which will prepare them to install a full-sized off-grid system in their home to free them from dependence on the electrical grid.

Syllabus

Schedule:
  • Class 1 (Thursday, 04/05): Duration 3 hours: Review the concepts and components of off-grid energy systems, the electrical diagram for the solar generator, tools and techniques for assembling the solar generator, and safety considerations when working with electricity. If time allows, students may begin building their solar generators.
  • Class 2 (Thursday, 04/12): Duration 3 hours: Templating the container. Preparing wires. Making connections.
  • Class 3 (Thursday, 04/19): Duration 3 hours: Building the solar generator. Students should finish the bulk of the build during this class.
  • Class 4 (Thursday, 04/26): Duration 3 hours: Final touches on the solar generator. Discussion of how to scale up the components of the solar generator to satisfy the load requirements of an entire home.

Solar Generator Components

case/housing (28 qt roller cooler) $34.99
2x 18 Amp-hr 12 Volt AGM deep-cycle batteries $69.98
60-watt polycrystalline photovoltaic panel $64.99
20 Amp 12/24 Volt PWM solar charge controller $19.99
8A AC battery charger / maintainer $39.99
12 VDC - 120 VAC 600W pure sine wave inverter $89.95
multifunction Volt Amp Power Meter / Display $29.59
100 A waterproof circuit breaker / switch $11.99
triple DC outlets w/on-off switch & 15 A fuse $14.99
AC power surge protector strip $5.00
10-12 AWG insulated stranded wire $10.00
wire connectors & screws $7.35
lexan sheet divider $8.99
sales taxes $4.20
TOTAL $412.00

Case/Housing

28 Qt. Roller Cooler

  • Lightweight molded plastic and foam shell makes for a portable, water-resistant, climate-controlled container
  • Non-conductive construction optimizes safety while providing a solid interior mounting surface
  • Soft ride sports wheels make it highly mobile
  • Push-button, locking, telescoping handle doubles as solar panel support
  • Molded side scoop handles double as water-shedding wire conduit
  • Elevated design minimizes unwanted thermal and electrical grounding
  • Enough interior volume (14.5" x 8.5" x 13") to fit all of our components

Batteries

12V 18Ah Rechargeable Deep Cycle Batteries

  • Sealed Lead Acid (SLA) Absorbent Glass Mat (AGM) technology makes these batteries spill-proof and vibration resistant
  • No off-gassing to worry about or maintenance of electrolyte required
  • 7.13" x 3.01" x 6.57" dimensions fit nicely in our housing
  • At 11.9 lbs each, they're heavier than lithium ion batteries, but we're putting them on wheels
  • Wide operating temperatures
  • High discharge rate, low self-discharge rate (3% per month @ 77°F)
  • Designed for a 5 year lifespan

Batteries

Performance Characteristics

Photovoltaic Panel

12V 60W Polycrystalline Photovoltaic Solar Panel

  • 25 year power output warranty from manufacturer
  • UL 1703 certified
  • 24.8" x 1" x 26.4" dimensions, 11.5 lbs
  • High transmission tempered glass designed to handle 1 inch diameter hail traveling at terminal velocity
  • Anodized aluminum frame
  • At rated power, will charge our 36 Ah batteries in about 7.25 hours

Charge Controller

12/24V 20A Solar Charge Controller

  • LCD display with voltage and charge/discharge status
  • Pulse width modulation (PWM) less efficient but cheaper than MPPT
  • 4-Stage(bulk, absorb, float, and equalize) charge management
  • Under 10 millamp consumption for the controller itself
  • Over-current, short circuit, reverse polarity, low voltage, and overcharge protections
  • 20A rating can handle 240W @ 12V or 480W @ 24V, so our 60W panel can be expanded for extra capacity
  • 2 USB ports included

Grid/Generator AC Charger

12V 8A Battery Charger/Maintainer

  • Will fully charge our batteries in about 4.5 hours
  • Start/stop button with auto-start after 8 minutes in case of interruption
  • 4-Stage(bulk, absorb, float, and equalize) charge management
  • LED indicators for charging status
  • Reverse polarity protection

Inverter

600W Pure Sine Wave Inverter

  • 600W continuous / 1,200W surge
  • 60Hz 120V AC output with 2 AC sockets and 1 bonus 5V DC USB port
  • LED indicators for status / errors
  • Thermal, over current, over voltage, and under voltage protection with alarm
  • Total Harmonic Distortion (THD) <3%
  • About 6W consumption for the inverter when idle

DC Power Outlets

Automotive Cigarette DC Power Outlets

  • Tap battery voltage directly (12 or 24V)
  • Dust covers
  • Switch to kill/enable loads without unplugging
  • 18 AWG wire with inline 15A fuse included

Amp/Volt/Power Meter

Multifunctional Digital Bi-directional Meter

  • Measures voltage, current, power, and battery capacity
  • Both charging and discharging are recorded without rewiring
  • LCD color display interface
  • Wireless transmission between meter and display
  • USB power for the display

Breaker Switch

100A Inline Circuit Breaker

  • Protects against over-current condition
  • Manual open circuit push button to disconnect system from batteries
  • No need to replace fuse
  • Sized to protect 10 AWG wire

10 AWG Wire

What It Can Power

Load Power From Full to 80% Depth of Discharge
40W-equivalent LED lightbulb 5 Watts 69.1 hours
Cable/DSL Modem 6 Watts 57.6 hours
Cellphone Charger (2.1A charging) 10 Watts 33.9 hours
Notebook Computer 25 Watts 13.8 hours
15 ft3 Chest Freezer 34 Watts 10.2 hours
40" LCD Television 36 Watts 9.6 hours
25.5 ft3 Fridge w/Ice Maker51 Watts 6.8 hours
52" Ceiling Fan (Max Speed) 66 Watts 5.2 hours
4.7 ft3 Front-Load Washer 70 Watts 4.9 hours
Keurig Coffee Maker 300 Watts 1.2 hours
1/4 HP Submersible Sump Pump 456 Watts 45.5 minutes
5000 BTU Window Air Conditioner 560 Watts 37.0 minutes
0.6 ft3 Microwave 600 Watts 34.6 minutes

Advanced Option
Solar Generator Components

Mounting surface (4'x4' 1/2" plywood) $15.00
2x 100 Amp-hr 12 Volt AGM deep-cycle batteries $369.99
280-watt monocrystalline photovoltaic panel $309.00
60 Amp 12/24/36/48 Volt MPPT solar charge controller $164.99
Xantrex Freedom HFS 2000 Watt Inverter / 55 Amp Charger $840.51
Multifunction Volt Amp Power Meter / Display - 500 A $36.50
200 A waterproof circuit breaker / switch $33.00
SquareD QO 100-Amp 6-space load center & breakers $82.21
4-10 AWG insulated stranded wire $75.00
Wire connectors & screws $40.00
Sales taxes $30.00
TOTAL $1996.20

What It Can Power

Load Power From Full to 80% Depth of Discharge
40W-equivalent LED lightbulb 5 Watts 16 days
Cable/DSL Modem 6 Watts 13.3 days
Cellphone Charger (2.1A charging) 10 Watts 8 days
Notebook Computer 25 Watts 3.2 days
15 ft3 Chest Freezer 34 Watts 2.4 days
40" LCD Television 36 Watts 2.2 days
25.5 ft3 Fridge w/Ice Maker51 Watts 1.6 days
52" Ceiling Fan (Max Speed) 66 Watts 1.2 days
4.7 ft3 Front-Load Washer 70 Watts 1.1 days
Keurig Coffee Maker 300 Watts 6.4 hours
1/4 HP Submersible Sump Pump 456 Watts 4.2 hours
5000 BTU Window Air Conditioner 560 Watts 3.4 hours
0.6 ft3 Microwave 600 Watts 3.2 hours
2-slice bagel toaster 850 Watts 2.3 hours
1/2 HP Submersible Deep Well Pump 1380 Watts 1.4 hours
12-Amp Commercial HEPA Vacuum Cleaner1440 Watts 1.3 hours
7.25" Circular Saw 1800 Watts 1.1 hours
2 HP 20-gallon air compressor 2000 Watts 57.6 minutes

Tools

wire stripper, cutter, crimper $10.00
needle nose pliers $6.00
precision screwdriver set $10.00
black & red electrical tape $5.00
TOTAL $31.00

Safety

  • Electricity can kill you. (But low-voltage, direct-current is relatively safe)

    Physiological Effect 60 Hz AC Threshold DC Threshold
    tingling sensation 0.7 - 1.1 mA 3.5 - 5.2 mA
    noticeable shock 1.2 - 1.8 mA 6 - 9 mA
    painful shock 6 - 9 mA 41 - 62 mA
    muscle contraction 10 - 16 mA 51 - 76 mA
    breathing difficulty 15 - 23 mA 60 - 90 mA
    ventricular fibrillation 30 - 50 mA 300 - 500 mA
    respiratory arrest 50 - 150 mA 350 - 1800 mA
    nerve damage, burns 200 - 1000 mA 4 - 5 A
    ventricular defibrillation N/A 6 A
  • Alternating current (AC) is more likely than direct current (DC) to break down the dielectric epidermis barrier, causing burns and significantly reducing electrical resistance across the body. This risk also increases with voltage. AC is also more likely to induce fibrillation. So AC, particularly at higher voltages, is more dangerous than DC for various reasons.
  • Safety

  • The resistance of the human body varies depending upon the points of contact and the skin condition. The skin resistance is your primary protection, and may vary from 1000 ohms for wet skin to over 500,000 ohms for dry skin.
  • Because of galvanic skin response, fear or anxiety can increase skin conductivity, so remain calm.
  • By Ohm's Law (I=V/R), wet skin (1000 ohms) could permit a current of at most about 0.012 A (12 mA) from a 12 V source, or 0.024 A (24 mA) from a 24 V source, which is not only below the lethal range but below the "let go" threshold, making the risk of prolonged exposure very remote.
  • Safety

  • Moreover, in dry conditions, the internal resistance between a person's two hands across their torso is closer to 1 million ohms, putting the risk of a lethal shock from a low voltage source into the extremely unlikely category. Even inadvertent shocks from 120 VAC to dry, intact skin rarely cause more than a surprise and tingling.
  • But any shock could be painful and maybe even cause local involuntary contractions if the skin is wet, especially with an open wound. If the skin is punctured, the internal resistance of each limb is about 500 ohms and between the ears only about 100 ohms.
  • Safety

  • Regardless, always be cognizant of where your body parts are in relation to electrical wires and devices. You can only receive a shock if you make yourself a part of a circuit, which should never happen.
  • Also watch where tools are going. Shorting the battery terminals with a screwdriver, even at only 12 V, can cause arc flash burns and spray you with molten metal.
  • It's also best to remove any jewelry on or about your hands and wrists or dangling from your neck or ears.
  • Safety

  • Pay close attention to the polarity of your wires. Hooking something up backward can have the effect of shorting it. Always use color coding appropriately -- in DC, red for positive, black for negative; in AC, white for neutral, black for hot, and green or bare copper for ground. You should never be confused about which wire carries which voltage or polarity.
  • Use color-coded electrical tape or heat shrink tubing to finish and protect bare metal ends of connectors in order to decrease the surface area of potential inadvertent contact between conductors.
  • Install appropriate current-limiting, voltage-limiting, and ground-fault protection devices as soon as possible in the construction of circuits.
  • Only work on non-energized wires whenever possible.
  • First Aid

  • If someone has received an electric shock, do not touch them until you're sure the source is disconnected.
  • Turn off any breakers or open the circuit by moving wires with a non-conducting tool such as a wooden broomstick, plastic chair, rubber doormat, etc. Or push the victim away from the source with a non-conducting tool.
  • If the victim is conscious, but experiencing tingling, chest pain, etc., call 911 immediately. Lay them down in a recovery position. Remove any smoldering clothing to prevent further thermal damage.
  • First Aid

  • If the victim is unconscious, instruct someone to find an Automated External Defibrillator (AED) and instruct someone else to call 911 while you assess for a pulse and breathing. If the victim is not breathing and has no pulse, begin chest compressions while the AED is being set up and until the AED indicates it is actively analyzing the heart rhythm or shocking the victim. Recheck breathing and pulse and resume chest compressions until vitals are restored or professional help arrives.
  • If there's a pulse but no breathing, perform rescue breathing.
  • General System Layout

    Wiring Diagram

    Circuit Schematic

    Advanced System Layout

    Scale-Up to Full-size System

    432 Wh System43,200 Wh System
    $34.99 Custom Battery Box $100.00
    $69.98 12x Rolls Surrette 2KS33P $9,360.00
    $78.99 15x Canadian Solar 280W $2,400.00
    $15.59 3x FlexMax 80 MPPT $1,563.00
    $29.98 IOTA Engineering DLS2740 $289.00
    $79.95 Outback 3500W Pure Sine $1,764.00
    $26.99 Bogart Eng. Pentametric $650.00
    $12.99 Outback & Square D panels $500.00
    $14.99 10x 12 VDC Receptacles $65.00
    $5.00 10x 120 VAC Receptacles $20.00
    $10.00 2/0 Cables, 8,10 Ga. Wires $400.00
    $7.35 Ring lugs, wire nuts, etc. $250.00
    $8.99 Misc. mounting materials $100.00
    $399.98$17,461.00

    Scale-Up to Full-size System

    Load Power 432 Wh System 43,200 Wh System
    40W-equivalent LED lightbulb 5 W 69.1 hours 287.9 days
    Cable/DSL Modem 6 W 57.6 hours 240.0 days
    Cellphone Charger (2.1A charging) 10 W 33.9 hours 141.2 days
    Notebook Computer 25 W 13.8 hours 57.6 days
    15 ft3 Chest Freezer 34 W 10.2 hours 42.4 days
    40" LCD Television 36 W 9.6 hours 40.0 days
    25.5 ft3 Fridge w/Ice Maker51 W 6.8 hours 28.2 days
    52" Ceiling Fan (Max Speed) 66 W 5.2 hours 21.8 days
    4.7 ft3 Front-Load Washer 70 W 4.9 hours 20.6 days
    Keurig Coffee Maker 300 W 1.2 hours 4.8 days
    1/4 HP Sump Pump 456 W 45.5 minutes 3.2 days
    5000 BTU Window A/C 560 W 37.0 minutes 2.6 days
    0.6 ft3 Microwave 600 W 34.6 minutes 2.4 days
    1 HP Wet/Dry Micro Vac 746 W 27.8 minutes 46.3 hours
    Mini-split Heat Pump 800 W 25.9 minutes 43.2 hours
    Angle Grinder 900 W 23.0 minutes 38.4 hours
    Upright Vacuum Cleaner 1.0 kW 20.7 minutes 34.6 hours
    Circular Saw 1.5 kW 13.8 minutes 23.0 hours
    1 HP Well Pump 2.0 kW 10.4 minutes 17.3 hours
    Central Air Conditioner 3.5 kW 5.9 minutes 9.9 hours
    3 HP Well Pump 5.0 kW 4.2 minutes 6.9 hours

    * 80% Depth of Discharge

    Scale-Up to Full-size System

    Scale-Up to Full-size System

    Scale-Up to Full-size System

    Scale-Up to Full-size System