Solar Power Basics
Danny Iland
Components of a Solar Setup
Devices (Load)
Battery
Charge Controller
Solar Panel(s)
Wires and connectors
1. Determine power requirements
Power (watts)= Voltage (volts) X Current (amps)
Energy (watt-hrs)= Power (watts) X Time (hrs)
Use a INA219+Arduino, 2 Multimeters, or a Watts-Up to determine power consumption and energy usage
Example: TP-Link 703N
Load Voltage: 12.21 V�Current: 82.30 mA��Power consumption of TP-Link 703N:�1.0049W = 12.21V * .08230A
Daily energy usage of a TP-Link 703N running 24/7:
24.12Wh = 1.0049W * 24h
2. Determine battery size
To maximize your battery lifespan, you should plan to use less than 50% of your battery capacity.
So your battery should be at least 2x your daily consumption, even if you live in the sunniest place on the planet.
Backup for days without sun
How many days in a row without sun could you have? Multiply that by your average daily energy usage. Now double that to prevent >50% battery utilization!
24.12Wh* 2 days without sun= 48Wh
So you would want a 96+ Wh battery
96Wh battery = 12V 8Ah battery
3. Determine required energy generation
Goal: Enough panel capacity to charge the battery from 50% to 100% AND power your device in one day of winter sun.
24.12 Wh to power the 703N for a day +
48 Wh to charge the battery from 50% to full
= We want 72Wh of energy generation per day from our panel.
4. Select a charge controller
$10 ones are fine (AGPTek or similar)
Maximum Power Point Tracking is more efficient, worth it for larger systems.
Prevent overcharging battery
Protects against over voltage of battery
Protects against under voltage of load
5. Determine worst-case sun
Depends on your location, time of year, the path of the sun, and obstacles.�
Gather elevation and azimuth information of objects around your site from the perspective of your panel and plot them on an elevation/azimuth Sun Chart. �
http://solardat.uoregon.edu/SunChartProgram.php
http://solardat.uoregon.edu/AboutSunCharts.html�http://tinyurl.com/chartSun
Even bare branches are obstacles!
Source: Steven Dufresne rimstar.org
6. Determine solar panel size
To generate 72Wh per day (assuming 80% charging efficiency) :
10W panel with ~9 hours of sun
30W panel with ~3 hours of sun
90W panel with <1 hour of sun
7. Buy things and hook it up!
12V 8 AH UB1280 Battery | $19.65 |
2-Port USB Car Charger with 2.1 Amp Output | $9.54 |
10A 12V/24V Solar Charge Controller | $10.17 |
10-Watt Monocrystalline Solar Panel�or�90-Watt Monocrystalline Solar Panel | $39.99 �or $175.00 |
Female Cigarette Adaptor | $7.42 |
Wires, connectors, etc. | $1.50 |
TOTAL | $88.27- $223.28 |
Links!
Calculation spreadsheet
http://tinyurl.com/is4cwnsolar
Making a Raspberry Pi 25% more efficient
@dannyiland
Open source Arduino power monitoring:
https://github.com/dannyiland/SolarPower