UNLIMITED SOLAR ENERGY!
Welcome to a beginner’s guide on solar power basics, where we will walk through a solar electric power system and how to build one – Solar panels, batteries, charge controllers, and inverters. Having built one by myself, I can easily see how this unlimited renewable energy source is quickly being adopted by cities worldwide.
For you guys who are still thinking about adopting the solar technology, I hope the information shared in this guide will prove to be useful. I took a small leap of faith, and just a small solar setup has reduced my bills… Very satisfying, and you can do the same too.
TABLE OF CONTENTS
How to Build
WHAT SOLAR ELECTRICITY? IS IT GOOD ENOUGH?
The core technology behind solar power systems (and solar panels) is Photovoltaic (PV) cells which converts light into usable electricity. While some people may think that this is some kind of advanced rocket science thing, it really has been around since the mid-1800s.
But back then, as you might have guessed, solar technology is just way too inefficient to be useful. It has only become mainstream lately with the progress in technology. But is it really good enough? Personally, I will say yes – Solar panels are affordable these days, and you will get free electricity as long as the sun is shining. What is so bad about that!? 😆
BUSTING THE MYTHS
There are so many objections whenever it comes to solar energy – It is expensive, it does not produce enough power, and it breaks easily. To smash some of those myths:
- Solar panels will work as long as there is direct sunlight. Even on cloudy days, and when it is raining.
- They are getting cheaper over the years, due to mass production and better technology – Check out this article on the cost of solar panels if you are not convinced.
- Solar panels are attached to satellites and launched into space, it IS space-age technology. They will last for a good 30-50 years when maintained properly.
- They may not produce as much energy as a nuclear power plant, but the efficiency is improving.
- Cities all around the world are quickly adopting solar power. In fact, International Energy Agency is expecting solar energy to be a major source of electricity by 2050.
If you are still not sure about solar technology, check out the Solar Impulse – Solar energy is already mature enough to power an airplane. Personally, I think that solar power is the next game changer. So much that electricty might even become free one day with it.
SOLAR POWER SYSTEM OVERVIEW
What do we need to build a solar energy system? Will it cost a bomb? Do we need to know how to build a rocket? No worries, solar systems are actually pretty simple. When it comes to the raw basic components, there are only 4 of them:
- Solar Panels: Convert direct sunlight to electricity.
- Battery: To store the electricity for the night.
- Charge Controller: To regulate the charging process, and prevent the battery from being over-charged.
- Inverter: Optional, if you want a “wall plug” from your solar system. We shall touch more on this later in this guide.
TYPES OF SOLAR PANELS
The fabled technology that turns light into power. While most people only know them as “one kind of solar panel”, there are currently 3 common types of solar panels.
MONOCRYSTALLINE SOLAR PANELS
The oldest and most energy efficient of the 3 technologies. As the name suggests, the solar cells are made with a single continuous crystal structure. It involves some complicated crystal growth process and thus making these pretty expensive.
POLYCRYSTALLINE SOLAR PANELS
The slightly newer technology, where solar cells are made with a large block of many crystals instead of one continuous piece. This results in less wastage, and thus less expensive. While it is generally less efficient, technology is quickly catching up and poly-crystal solar panels are quickly becoming the “cheaper better” technology.
AMORPHOUS SOLAR PANELS
This is the youngest technology among the three, and it is basically a thin layer of silicon over metal or glass. The thin film solar panel is the cheapest to manufacture, flexible, ultra-portable, but also the least efficient.
TYPES OF BATTERIES
Solar panels will only work when there is the sun, and thus we need batteries to store energy for the night. I am sure we are all already familiar with AA and AAA batteries. But for solar systems, we use the slightly bigger batteries.
SEALED LEAD ACID (SLA)
The most traditional form of “heavy duty” battery that is used in cars, golf carts, and airplanes. In a nutshell, this is acid sealed inside a lead casing. Very heavy to be carrying around, but is also pretty much bulletproof.
ABSORBANT GLASS MAT (AGM)
A slight improvement over SLA batteries by using a thin piece of fiberglass mat to absorb the acid, and relying less on a lead casing. While lightens the battery a little, it is still essentially acid inside a box.
One of the safest batteries that I prefer to use. GEL batteries as the name implies, do not use liquid-based acids, but a gel based one. So even if the casing breaks, nothing is going to spill.
More like a character than a type of battery. All batteries take damage when they are over charged-and-discharged. Deep cycle batteries can take more punishments, and thus preferred over the “normal” batteries.
Lithium batteries are commonly used in smartphones, tablets, and laptops these days. The ones used for solar systems are a little larger though. Lithium batteries have an edge over traditional acid batteries in terms of capacity and weight. They don’t spill acid either. But… they explode when punctured. Handle these with care.
The common Joe battery. I have not seen anyone tried using these for solar systems, but I guess they do work… It’s just that AA batteries cannot survive the heavy charge-discharge cycles, and thus, not cost efficient in having to replace them often.
Can we just use solar panels to directly charge batteries? The answer is yes, but that is very risky. There is no way we can tell if the battery is already fully charged, and overcharging batteries usually end up badly.
So this is why we need a charge controller. To stop charging when the battery is full, and to stop discharging when the battery is low. The charge controller basically acts as a safety device to prevent disasters and to extend the lifespan of your batteries.
PULSE WIDTH MODULATION (PWM)
PWM controllers are the time-proven good old reliables. They are generally simple, cheaper and not meant for heavy-duty uses.
MAXIMUM POWER POINT TRACKING (MPPT)
MPPT controllers are more intelligent and heavy duty than PWM controllers. Basically, they do the magic of self-optimizing whatever solar array you throw at it. As you can guess, these toys cost a lot more than PWM.
For a basic solar setup, the above 3 components will suffice. But before you get too happy, there is something that you need to know.
- The power we get from the solar setup is direct current (DC).
- The power we get from wall plugs is alternative current (AC).
Which means, you simply cannot plug your house appliances directly into a basic solar setup. If you want to use your “usual electronics” with the solar setup, you will need a fourth component called an inverter, which converts DC to AC.
As to why are there 2 “types” of power? Well, this is the history of Thomas Edison and George Westinghouse. I am not going into the details, but you can read the war of the currents if you are interested.
CONSIDERATIONS BEFORE BUILDING
Before you build the masterpiece, you need to have a plan. Nope, planning is not about wasting time and being a smart aleck. It is about what you need, buying the correct stuff, and not spending too much money on things that you don’t need.
CHOOSE A SOLAR PANEL
When it comes to choosing solar panels, there are several considerations:
- Which type of solar panel?
- What voltage?
- What wattage? (Measured in watts, the higher the number, the more power the solar panel produces)
- How many to get?
Each technology has its own pros and cons. If you just want a small portable solar charger for your phone or tablet, the thin film makes sense. Otherwise, for general home use, go for monocrystalline or polycrystalline panels. As for choosing the voltage, it’s simple.
- 6v if you just want to charge USB devices.
- 12v for regular setups.
- 24v for heavy duty setups.
Lastly, for the wattage and how many to get, some experts like to throw numbers. But for me, I go with the simplest instinct – How much space and budget do you have? If you have space to deploy and budget to burn, just splurge on a big solar panel array. If not, start small, and you can expand the system in the future anyway.
Choosing a battery (or batteries) is just like choosing a solar panel.
- Which type of battery?
- The voltage of the battery.
- The capacity of the battery. (Measured in ampere hour, the higher the number, the more power the battery can store)
- How many batteries?
There are many kinds of batteries as we discussed above and note that every kind of battery is different. Personally, I recommend GEL batteries as they are probably the safest. Lithium holds a lot of power, but they explode when punctured.
As for the voltage, I like to keep things simple again. 12v batteries to 12v panels, and 24v batteries to 24v panels. There should be no confusion over this one. But personally, I recommend 12v systems as many car and boat accessories run “natively” on 12v; You can just buy these accessories and directly plug into your solar power system.
Lastly, for the battery capacity – The lazy way is to start with one huge battery first (maybe a 100 Ah battery), then expand as your solar panel array is producing way too much power.
Lastly, you will need to choose a charge controller. Which are just 2 questions :
- PWM or MPPT? If you are looking at a large solar setup (now or in the near future), it will make sense to invest in an MPPT charge controller right off the bat. If not, PWM will do the job just fine.
- What are the maximum voltage and current (ampere) that the controller can handle? You do not want to plug a 64V battery into a rated 12V controller… nor do you want to burn a rated 20 amperes controller with 100 amperes of solar power.
Generally, if you are looking for a small and affordable setup, just go with the PWM. If not, get an MPPT to cater for future expansions. If you plan on using PWM controllers, note that the voltage of the solar panel and battery must match. I.E. If you buy a 12V battery, the solar panel must be 12~18V.
The optional component if you want to use household electronics. This is simple. Get a small 1000w inverter for light-weight systems, get a 10000w for heavy usage. One thing you should be aware though – inverters are inefficient. Use 12v DC accessories if you can.
HOW TO BUILD
So now we know all about solar panels, batteries, charge controllers, and inverters. But how do we put them together into a system? How do we design one, and what are the tools that we need?
BEFORE WE START By reading this guide and/or building this project, you fully understand the risks and agree to the site terms. Red Dot Geek is not responsible for any personal injuries and property damage. Build this project at your own risk.
SAFETY & DISCLAIMER
You are dealing with electricity in this project, and it can potentially cause harm when you mishandle it. If you are unsure, please consult a professional. Always stay safe and wear appropriate safety gear at all times.
TOOLS YOU WILL/MAY NEED
We are not going to build a system with rocks and sticks. These are the tools that you might need, and just to make your life a lot easier. Reminder, these are referral links from eBay and I will get a small commission when you buy from these links; It helps to keep this blog alive. 🙂
|Crimp/Cutter Tool [Link]||A convenient tool to cut wires and crimp connectors together. You can also get this from a hardware store, or work around with a pair of scissors and pliers.|
|Wires [Link]||Do your own estimation and get however much you need to stretch out your system. Take note that American Wire Gauge (AWG) is a commonly used standard to denote how thick a piece of wire is. The smaller the number, the thicker it is. For light usage, AWG 14-16 should be sufficient. For heavy duty systems, go for AWG 10 or smaller.|
A word of warning – Don’t try to cut costs by getting those thin pieces of wires. If you pass too much electricity through a thin piece of wire, it will catch on fire. Definitely not worth it to endanger your own life.
|MC4 Connectors [Link]||Most modern solar panel will have a male/female MC4 connector attached to it “by default”. So at the bare minimum, you are going to need another pair of male/female MC4 connector to tap the solar power. If you want to join multiple solar panels together, you are going to need the MC4 splitters.|
|Soldering Iron [Link]||You can actually get this in any hardware store, but I will just leave the link here. For you guys who are lazy to solder, you can probably just twist 2 pieces of wires together and tape them shut.|
|Electric Tape [Link]||The one thing you can’t live without.|
|Heat shrink tube [Link]||Another recommended convenient cheapy for lazy people who do not want to solder. Put on the heat shrink tubing, twist 2 pieces of wire together, then shrink them shut with a hairdryer.|
|Solar Panels [LINK]||The heart of the system, and I leave it up to you on how many to get. As for the recommendation, I started with a single 18v 100w semi-flexible solar panel. Yes, I used an 18v panel to charge a 12v battery. If you have the sun, space and budget, feel free to get more.|
|Charge Controllers [PWM] [MPPT]||There are plenty of cheap PWM options on eBay, but beware when purchasing MPPT on eBay. An MPPT can easily cost from USD60 to even thousands. If you see one going for like, USD10-20, something is wrong. Some of those bad sellers don’t even know the difference between PWM and MPPT. If you need a recommendation, go for the cheap-and-decent EPEver (previously EPSolar) MPPT controller.|
|Batteries [LEAD ACID]||Take note that some countries might have import restrictions on batteries. Importing batteries from eBay may not be the best idea, and the shipping is can be expensive. Your best bet to get batteries is from an auto supplies store or a gas station. Recommendation, I started with a 40AH GEL battery. Good enough to power a long LED light strip, and charge my phone. Get bigger batteries if you want.|
|Inverter||Please check the rating of the inverter before buying one. Depending on where you are, the wall plugs might supply 110v or 220v. Get the proper voltage and not fry your electronics. [1000w] for light usage, [5000w] medium usage, and [10000w] if you run a mini solar power plant.|
STEP 1: WIRE THE BATTERIES TOGETHER (IF YOU HAVE MULTIPLE BATTERIES)
If you have purchased multiple batteries, you will need to wire them together first. If not, keep this as knowledge for the future. There are two ways to connect your batteries together – parallel and series.
- Series connection: Wire the + terminal of one battery to the – terminal of the other battery.
- Parallel connection: Wire all the + terminals together, then wire all the – terminals together.
- In a series connection, the voltage stacks but capacity remains. E.g. If you put 4 X 12v 100AH batteries in series, they will act like a single 48v 100AH battery.
- In a parallel connection, the voltage remains the same but capacity “combines”. E.g. If you put 4 X 12v 100AH batteries in parallel, they will act like a single 12v 400AH battery.
So which connection to use? Normally, it will be in parallel. But if you want to “convert” your 12v batteries into 24v, just wire a pair of them in series.
Safety note: Please do not handle the battery, wires or electronics with wet hands. Especially touching the – terminal with one hand, and + terminal with another hand. This may cause the electricity to pass right through the heart and is potentially fatal.
Safety note: Please do not touch 2 bare terminal wires together (one wired to -, and the other to +). This may cause sparks to fly and cause a fire. It’s fun to watch, but not fun to get burnt.
STEP 2: WIRE THEM PANELS TOGETHER (IF YOU HAVE MULTIPLE PANELS)
Next stop, wire the panels together if you have decided to get multiple panels. Remember the series/parallel from 30 seconds ago? Yep, it’s the same with solar panels.
- When wired in series, the voltage stacks up. E.g. Wiring a pair of 12v solar panels in series will act like a single 24v solar panel.
- When wired in parallel, the current stacks up. E.g. Wiring a pair of 12v 100w solar panels in parallel will act like a single 12v 200w solar panel.
So series or parallel again? It’s up to you, but the parallel is the easier way out. There is a good reason to use series though, and that is to stack up the voltage. In some shady places, solar panels don’t exactly produce enough power. When the voltage falls short, it will not charge the battery.
Which is why some people prefer to use 24v (or even more) solar panels to charge 12v batteries; The other way around is to connect the panels in series to stack the voltage. This, however, will require you to have a charge controller that can handle a higher input voltage.
STEP 3: CONNECT BATTERY TO CHARGE CONTROLLER
On the charge controller, there should be at least 6 terminals – check your user’s manual. 2 of them should go to the battery, 2 of them goes to the solar panels, and the final pair to whatever you want to run from the batteries – lights, fans, etc…
This part should be dead easy. Just connect the battery to the correct terminals on the charge controller (plus to plus, minus to minus). The charge controller should power up when you connect the batteries correctly.
STEP 4: CONNECT SOLAR PANEL TO CHARGE CONTROLLER
Next, connect the solar panels to the charge controller. The same thing again, plus to plus, minus to minus. The charge controller should indicate that the batteries are charging when plugged in correctly… and of course, when there is enough sun.
STEP 5: LOAD IT UP!
That’s it, you now have the sweet power of the sun stored in a battery. But I am sure you did not buy an entire solar setup to store energy and not use it. How we tap the power is very simple. Remember – to -, + to +? Remember series and parallel. It’s the same thing again, rig your devices in parallel, the plug them into the “load” terminals of the controller.
For those who are curious what happens if you put your gadgets in series – The first gadget will get all the juice, then the rest of the gadgets gets progressively less power and will not run properly.
Safety note: It is a good idea to have some kind of a “master switch” to shut down the whole system. Put some fuses in as protection as well.
Safety note: If you have decided to go with a 24V battery, do not plug 12V devices directly into the system. Chances are, you are going to fry the 12v gadget. Use a voltage step-down (see recommendations below).
All right! If you have walked through all the above steps, you should have a fully functional solar rig. Here are a few recommendations on 12V gadgets that you can directly stick into a 12V system, and of course, for the people who are lost, you can get the same parts as my starter rig.
MY STARTER RIG
Here are the parts of my starter rig. It charges smartphones, tablets, power banks, and runs LED light strips… Don’t expect too much, but it works.
- 18v 100w semi-flexible solar panel
- 20A PWM charge controller with built-in USB ports
- 40AH 12V GEL Battery
Just these 3 main components, and if you don’t stretch out too much on the wiring, it should cost about US$300.
Here are a few of the “good stuff” that you can directly plug into a 12V system. In fact, if you buy a car plug, you can even use your existing car accessories.
GO BIG, GO GREEN!
Congratulations on finishing this long guide. If you have constructed your own solar rig, welcome to the club! I am sure it is satisfying to watch the rest of the world curse at paying more electricity bills, while we just shrug at our shrinking bills.
For you guys who live in a city and still wondering if solar makes sense, yes it does. As long as you have a sunny window or balcony, it will work. Just imagine having a small solar setup to charge your phone, power bank, and light a small room for years – just how much will this save you?
So if you have not adopted solar yet – It is time to seriously consider getting started now, and you can enjoy the fruits of labor. Cheers!
W.S. Toh is a senior web developer and SEO practitioner with over 10 years of experience in building websites. When he is not secretly being an evil tech ninja, he enjoys doing photography and working on DIY projects.