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As a project to learn more about solar power, reduce my electricity usage, and build a small bit of resilience against power outages, I’ve build a small-scale (two 100W panels panels, 440Wh of battery capacity) solar system. The outcome: it’s been a lot of fun, I’ve learned a ton, and I can keep my essential battery-powered devices running for longer when the power’s out (indefinitely if it’s sunny), but not my whole home or even HVAC. Cost-savings was not a primary goal, which is good because I’m saving only about $1/month on my power bill (electricity here is cheap at $0.16/kWh), and would need a much larger solar setup to increase that.
Components of Solar Generation
- Solar panels: solar panels work when the sun’s rays knock electrons out of silicon crystals by giving those electrons a place to go and generate a voltage that can do work along the way.
- Wires: called “conductors” by electricians, these carry the voltage to where it can be used or stored. Solar panels commonly use waterproof, locking MC4 connectors between conductors. Make sure the type of connectors used by your panels are compatible with the other components, with adapters if needed.
- Battery: while some electronic devices like fans could be run directly off solar panels, most devices need a consistent voltage and current. Batteries provide that, while also letting you store energy to be used after the sun goes down. They come in different chemistries, including lead-acid (i.e. car batteries, the least expensive), lithium-ion (the lightest), and LiFePO4 (lithium-iron-phosphate), the safest and longest-lasting but heavier than Li-ion.
- Charge controller: a charge controller’s primary job is to regulate the power produced by your solar panels in order to safely charge a battery. That means providing a consistent voltage to the battery until it’s charged, and cutting off power to the battery once it’s full, so as to avoid dangerously overcharging it.
- Inverter: batteries produce direct current (DC) which is fine for many electronics (e.g. anything with its own battery), but household appliances (anything with a plug) run on alternating current (AC). If you want to run any of those, you’ll need an inverter to convert your panels’/batteries’ DC to AC.
- Portable power station: a class of consumer device which combines the battery, charge controller, and inverter into one package.
My Setup
- Panels: two Renogy N-type 24V solar panels rated at 100W each for a total of 200W of potential solar generation. So far the most I’ve gotten on a sunny day is 160W, but I’m only a couple weeks in.
- Portable power Station: Bluetti AC50B 448Wh, chosen for its decent capacity, ample array of output ports, and that it came with an adapter for MC4 solar cables.
The power station accepts up to 200W of solar input at 12-28V. Two 24V panels wired in series would double their voltage to 48V, so I wired them in parallel with this MC4 parallel adapter cable to keep their voltage at 24V. I also bought a 30’ MC4 extension cable so I could sit in the shade with my laptop plugged into the power station while leaving the panels out in the sun.
Lessons Learned
- When the sun’s out I can easily charge the 448 watt-hour battery in a couple hours, leaving me looking for ways to use all the extra free energy my panels can capture. I’ve started waiting for a sunny day to charge my big lawnmower battery with solar.
- Boiling a pot of water with my electric kettle uses about 80 watt-hours of energy, or about 30 minutes of full sun on my two panels. I like the thought of drinking tea steeped in a half-hour of sunshine.
- Clouds drastically reduce solar panel output. When a cloud passes in front of the sun it doesn’t look that much darker outside, but my panels’ output can drop by 80%.
- The angle at which the sun hits the panels (ideally 90°) matters. I’ve found I can get about 30% more energy out of them if I move them to directly face the sun a few times during the day, though of course that’s not an option if you mount them.
Next Steps
We’ll see!