"Germany is now the world's largest manufacturer of solar
panels. They have a very ambitious renewable energy program.
Sunlight availability in Germany is much lower than in the
USA where polluting coal and gas power are still king."

 


- Free Tutorials -

 

 
 

 
Lets give you some solid basics about off-grid solar power -
  by introducing some of the big topics
 

 
  Click on the topics to jump to that subject.

  What is a solar panel and how does it make electricity?

  Off Grid VS. Grid Tie system
  Charge Controllers
  Battery types
  Wiring Battery Banks
  Inverters
  Solar Panel types
  Mounting solar panels
  Wiring up solar arrays
  Battery maintenance
  Sun tracking
  Budgetary considerations
 
 

  What is a solar panel and how does it make electricity?

  A Photovoltaic (PV) solar panel is a semiconductor device that is made the same way that transistors
and computer chips are made. It is the exact same material -Silicon Carbide with trace amounts of other   chemicals which enable the silicon (glass) to make electricity from sunlight that hits it. The "photons" of light from the sun -liberate electrons from the atoms in the panel's layers and these are collected by a metal grid on either side of the panel. One side is positive and the other negative. The trace amounts of other chemicals in the silicon give it a negative or positive affinity. These different layers are on top of each other in the panel.
Over many decades, the efficiency of the panel will go down a bit. That said, it will produce over 75% of it's original output for at least 30 years.
 

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 What are Off-Grid and Grid-Tie Solar power systems?

  A "Grid -Tie" system is one which is directly connected with the commercial power lines. There are normally no batteries to store power for cloudy days in a grid-tie system. The advantage is that you don't need to buy batteries. the dis-advantage is that your system will be shut down during general power outages and you will still need a generator for emergency power. Grid-tie systems "spin the meter backwards" during the day and feed power into the commercial power system. In the evening, you draw power from the power lines as usual.
Thus, you only pay for the differential between what you made during the day and what you used at night.
Grid-tie system require a NABCEP certified installer and inspection by the power company before use.

With an off-grid battery-based system, you are autonomous from the commercial power lines. Your system charges a bank of batteries during the day and you use that power at night. Homeowners are allowed to do electrical work on their own homes in most jurisdictions. Thus, you could build an off-grid system without an electrical inspection in most areas. As well, you can build any size off-grid system. You might build one only to power your freezers... or power a weekender cabin. You can also build portable off-grid systems on a trailer.
The downside to off-grid is that you need to buy batteries every 10 years or so. If you don't use no-maintenance batteries, you'll also need to keep them topped-off - so there is a little maintenance involved.

People who just want to cut their electrical bill often opt for grid-tie systems. Those who want to go "off-grid" and be totally self-sufficient opt for off-grid battery-based systems. Federal tax incentives give credit for both types. The tax credit is only for the actual hardware and not labor. Since grid-tie systems normally require a professional installer, a much smaller parts of your investment qualifies for the tax credit with grid-tie.
 

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Charge Controllers - What are they?

  A Charge controller is the device that regulates the charging of your battery bank in an off-grid system. It is just like a battery charger for an automotive battery- but its a lot smarter. These controllers monitor the output of your solar panel array and charge the batteries in several stages. Batteries are best charged more heavily at first and less strongly as they top-off.

MMPT type charge controllers are the latest technology and are able to convert 30%-40% more power from the solar panels into actual battery charging current (compared to the older traditional type chargers. They optimize the battery charging - almost continuously. MPPT stands for Maximum Power Point Tracking. The charge controller must know what the battery bank voltage is. This is set by jumpers on the controller or on the LCD screen of the controller. Each controller has a maximum current it can handle and a maximum voltage input. Having the ability to take a higher voltage from the solar array, it allows you to configure the solar panels for a higher voltage -so that you loose less power on the wire run from the panels to the charge controller. Many controllers also store data from each day. You can also install remote control "heads" so that you can control it from inside the house.

The higher the battery bank voltage you are using, the more power a given charge controller can handle from the solar array. That's because since the controller has a fixed maximum current in amps, when you multiply the battery voltage by that maximum current- you get the total wattage it can handle. The higher that battery voltage, the more watts of panels it can handle. Amps X Volts = Watts. Typically, you use either 12 /24 or 48 volt battery banks. 24 volts is a good balance an popular battery bank voltage.

Cost for medium-sized charge controllers ranges from $250-$550. This is for systems around 2000W. For small systems of under 1000W, you might choose a traditional charge controller of much less cost.
 

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Battery Types

 Batteries used for solar applications are always "Deep-Cycle" batteries. This means that the battery can be charged and dis-charged down to about 20% of it's total capacity without damage. Realize that car batteries are designed to give just a high pulse of power to start the motor. Deep-Cycle batteries are used for trolling motors and ranch applications etc. Deep-cycle batteries come in two types, wet-cell and AGM. Wet-Cell batteries are the typical type we see in cars. The "electrolyte" (batttery acid) is a liquid. AGM (absorbed glass mat) batteries use a gelled electrolyte. These are more expensive and are used where you might spill battery acid (electric cars etc). Either type can be used for solar systems.

Battery quality is determined by the size and thickness of the lead plates and the volume of electrolyte. You are paying a price for the lead, so the bigger they are, the more they cost. With wet-cells, you might use golf cart batteries, trolling marine batteries or industrial wet-cell batteries from fork-lifts etc. You should go down to your local industrial battery supplier and see what the best value he has is. You can configure batteries into any voltage "bank" you choose, so really, you can get whatever the best value is and then configure it using jumpers to your desired voltage. The larger the batteries you buy, the less jumpers you will need, so this saves time and money.
 

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   Wiring Battery Banks

  The decisions you will have to make are- what battery bank voltage I want, and how much power do I need in Amp-hours total. Each battery is rated in Volts and Amp-Hours.  The typical battery bank voltages are 12 /24 /48. If you don't need 12 volts DC for appliances like RV appliances or radio equipment, you can and should go with a higher voltage system. Why? Because you loose less in the same wires with higher voltage and your wires are expensive (copper). You'll need thicker and costlier wires for a 12 volt system. 24 volts is a good compromise voltage. Also, other components like the inverter are available easily for 24 volts. 48 volt inverters are un-common... less selection.
Second decision is how many amp-hours total do you need. Well, you take your solar panels total wattage, divide by 24 (if that's your battery voltage) and multiply that by 25. This gives you several days of operation off batteries if it is rainy. I'm writing this on a laptop powered by solar batteries after 4 days of no sun.

So, now you have to wire up the batteries for your desired voltage and amp-hours total. Batteries add up their voltage when you wire them in series (plus to minus) and add up their amp-hours when wired in parallel (positive to positive and negative to negative). So, you first make a first bank of individual batteries in series to get your desired voltage (2 if they are 12 Volt and 4 if they are 6 volt to get 24 volts). The amp hours of that "bank" are the amp-hours of one individual battery. (REMEMBER: you cannot mix batteries of different types or age in the same system). Now you have to clone that first configuration as many times as it takes to add up the amp-hours for your total system. You then wire these clone banks in parallel to get your desired amp-hour total. I show exactly how to do this in the video. You have to be VERY careful wiring these banks. You have to wear safety glasses, no jewelry and tape all the handles of your tools with electrical tape. I don't suggest you attempt this after only reading this briefing. This is the only dangerous part of building a solar system.
 

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 Inverters

Inverters are the electrical device that converts the DC power from your batteries into AC power for your household appliances. These come in two varieties : Sine-wave and modified sine-wave. Sine-wave inverters are more expensive and slightly less efficient. They must be used to delicate equipment such as stereos, TV's, tower computers and all things that have an electrical motor in them (Freezers, vacuums etc). Modified sine-wave inverters are the common ones you see on store shelves used for making AC power in autos and RV's. These are around 97% efficient and are quite inexpensive. They are good for light bulbs, laptop power adapters.. and non-critical applications. Typically, you might use both types in one system. You get what you pay for, so if you buy a cheap sine-wave inverter, it will probably not perform like you expect. With the modified sine-wave units, there is less difference between cheap and expensive. You need to calculate the total wattage of all the appliances you want to power on solar. Then get inverters which can easily power them. Remember, your battery bank can only deliver about 1/4 of it's total amp-hours continuously, so
if you are using say 24 volt batteries and have 500 amp hours of them, 24 X 500 = 12,000 watts available.
1/4 of 12,000 watts is 3000 watts. So, you cannot draw more than 3000 watts with your inverters continuously without damaging the batteries. You'd like to draw less! The less you draw, the longer they will last.

Calculating what you should buy is determined by either your maximum budget or your power needs (if you have unlimited $$) You will typically make less than- or just enough for your needs. I show the exact methods for calculating your outlays on each hardware item in the full course.
 

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PV Panel Types

Photovoltaic solar panels come in many types. The most common are:

Single-Crystal
Poly-Crystalline
Amorphous
Thin-Film

The first two types are used to make rigid solar panels that are used in 90% of all solar installations. They look very similar, but the poly-crystalline have a multi-faceted look to the individual cells themselves.
Both are about the same efficiency. This is about 16%. This means that you can get well over 300 watts per square meter of panel area. Typically though, a 200Watt panel is about 16 square feet.
Poly and mono crystal panels are of high-quality and very preferable for standard PV installations.

Amorphous panels are made by coating glass with photovoltaic material. These are cheaper to produce and have some issues with longevity and consistency of output over time. If made by well-known manufacturers, they can be a good choice. You'd like a warranty!

Thin Film technology is the latest craze. It uses only 10% of the materials as a traditional panel and can be used on unconventional surfaces (such as roofing tiles). Thin Film panels are becoming available and when made by reputable companies, they are a good option.

The most important things to desire in a solar panel is a good value, a warranty and a reputable manufacturer.
 

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 Solar Panel Mounting

Individual panels are assembled into arrays using panel mounts. Panel mounts allow you to raise the the panels up into the sun's path and away from harm. They allow you to secure the rather weak frames that panels are made with -and rigidify them for weather resistance. It is possible to construct panel frames from treated wood or metal. As well, you can buy commercial mounting frames from companies such as Zomeworks. Professional mounting frames can me ordered so they mount on schedule 40 metal pipe.
This is a very popular mounting arrangement. The mounting frames should allow for adjusting the angle of the
panels to face the sun in different seasons. Many people use angle-iron with perforated holes which the panels can be screwed to. Panels are pre-drilled with mounting holes. When designing frames, these should be your criteria:

Mechanical rigidity
Angle adjustable
not-unwieldy... able to me handled by installers

You need to choose your location for full sun exposure- then design panel frames to fit that location. If you have tree shading, you'll need to raise the panels up into the tree canopy. The angle adjustability needs to be from at least 45 degrees to the ground and fully parallel to the ground for northern latitudes. If you cannot adjust the angle, you should set them so as to be fully facing the Winter sun mid-day. This is because you need to favor the Winter sun's lesser hours. In Summer, you'll still get good sun coverage. Modern panels have a coating so they make good energy from off-axis sunlight.
 
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  Wiring up Solar Panel Arrays

   Wiring up solar panels into "arrays" is very similar to wiring up the battery banks. This is because the BIG rule applies. Wiring in series adds up the voltage and wiring in parallel adds up the current. Series is like in a flashlight.. negative to positive again and again. Parallel is wiring positive to positive and negative to negative.

The process is this:

You select the battery bank voltage you want to go with first. Then you select your charge controller- one that it big enough to easily handle all your solar panels. You will have spent about 50% of your total budget on panels themselves. You then check your charge controller and KNOW it's maximum voltage in. You then wire up a bank... a set.. of panels- usually 2-5 in a series "string". You then clone these sets until all panels are gone. Of course, you'd buy the right amount of panels so that you have full sets. The total voltage of these individual sets have to be at least 50% more than the battery bank voltage to a maximum of about 20% less than the charge controller maximum input voltage. You HAVE to be 50% higher than the battery bank, but that's easy because individual panels are now normally 29 Volts. If you need to get further from the batteries and CC to get full sun, you should go to a higher voltage. The higher the voltage, the less loss in the run to the batteries.

You will have to buy MC connector jumper cables or adapters to configure the panels correctly.  Ask your dealer exactly which you'll need. they are "genedered" for plus and minus, so wiring sets in parallel requires cable adapters or soldering. It's fairly complex. I show you all the normal wiring situations in the video.

You should run the output of the panel array down to a dis-connect box at the mounting stand's base. This can be a typical AC disconnect. You may use flexible blue conduit or grey electrical PVC for the run from array to box. This allows you to dis-connect the array from the other equipment when you are working on it.

Another AC dis-connect box is used at the input to the battery box. This is a good place to install a Lightening arrestor. (also all covered in the video)

Remember, panels CANNOT be turned off when in the sun. You should NOT connect the connectors together while they are in full sun. This will cause a spark and damage the metal inside the connectors. Do your wiring in the evening.. at sundown. You can also cover them all with cardboard. You only do the connections once..

Note: When the sun comes back out from behind a cloud, there is a temporary magnification effect while it emerges. This can result in a short-term rise in voltage and current from your system. You will see this on your charge controller meter when it happens. This is why you leave a little "headroom" in the voltage your panels are wired up to provide - so as to not exceed the maximum voltage input specification of the charge controller. The charge controller (MPPT) will convert all the extra voltage from the panels into charging current at the desired battery bank voltage you are configured for. You set the charge controller for the battery bank voltage you've chosen- with either jumpers or selections on a menu- depending on your brand/type. 
 

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Battery Maintenance

Lead-Acid deep-cycle batteries require maintenance. Batteries with liquid electrolyte (sulfuric acid) require
filling periodically... just like a car battery does. The more you charge and discharge them, the more they need to be topped-off. You check the acid level by removing the battery's caps and visually checking the level.
You need to have safety glasses on. You might as well use rubber gloves. Some people are more sensitive to sulfuric acid than others. You will be topping-off the batteries with distilled water. Never add battery acid.
NEVER let the electrolyte get below the tops of the actual battery lead plates. Use a plastic funnel to fill the battery cells. DO NOT wear metal jewelry or a watch when doing this. Also, the acid will eat through cotton clothes. Wear old clothes. Slowly fill each cell to about 3/4 inch from the top. Do not fill them all the way to the top. Acid will bubble out during charging. If you see your charge controller voltage go up to 15V or more when charging, it is a good indicator that your batteries are low. Don't let it get to this stage. Check them every few weeks.

Wipe off any spilled acid or water on the battery tops with a disposable cloth. You should also consider spraying anti-corrosion spray on the battery terminals. An old trick is to put two shiny pennies near the terminal. These will draw off any corrosion and can be replaced when shot. There are also treated red and green anti-corrosion disks that you can buy and they go under the terminals.

Once a year, check tightness of all connections... they loosen up sometimes. Put electrical tape over all your tool handles so they cannot short the batteries out if you drop them.
 

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Sun Tracking

The solar panel array needs to be as perpendicular the the sun as possible. There are two paths involved.
First is that the sun's path across the sky changes from season to season. The second is that the sun moves from east to west during the day.

Your panel array needs to be adjustable for seasonal change. The sun's path is nearly overhead in Summer in North America and quite a bit lower in Winter. Thus, we are talking about the panel's angle to the horizon.
You can do these seasonal adjustments a few times a year. The more you do them, the more energy you will make. Really, twice a year is fine. This is because the panels have a coating on them that captures off-axis light well. In Summer in the northern hemisphere, your panels will be almost horizontal in southern latitudes and somewhat less than that as you move north. If you are roof mounting panels and cannot adjust them, you should position them for the Winter sun angle. Winter has fewer hours of sunlight and you are indoors more using more energy... so favor the Winter. The course teaches you exactly how to mount and adjust them for your location.

As far as tracking for the sun's daily movement, you can buy tracking mounts, but since the panels are so good at making energy from off-axis light, the payback period for the extra cost of the trackers is too long in my opinion. I opt for fixed mount panels. You do want to mount the panel array so that it is due south.
 

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Budgetary Considerations

If you are wondering about the economics of building a solar system, read my page on that.

This is about the cost break-down when building.

When you are designing your system, you may be coming at it from three possible positions:

1. You have an un-limited budget and want to make ALL your current power needs with Solar.
2. You have a budget limit and want to make as much power as you can inside that budget.
3. You want to power a specific set of appliances or a cabin (small system design).

In each situation, you will be spending about 50% on your panels themselves, 10% on the Inverter, 5% on the charge controller, 25% on batteries and 10% on the hardware and wire. As panel prices drop (they are), you'll spend a slightly lower percent of the money on the panels themselves.

If you have an unlimited budget, know that to generate 1KWH of power a month, it takes 6 watts of solar panels (with 5 hours of sun a day). Check your electric bill and multiply by 6. Then look online for package deals on equipment at that level. With the limited budget, take 50% of your money and see how many panels you can get. Shop for best price and name brand. Then talk to the vendors about the rest of the stuff you'll need. They will be super-happy to configure all the parts required - inside your budget.

If you are making a small system for a cabin or dedicated application, you'll need to do an energy budget.
The videos tell you exactly how to make this calculation. It's not difficult but beyond the scope of this lesson.
 

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I hope this gave you some real insight into the process of building your own system. My goal is to get you to the level where you'll understand all the concepts involved and how they are applied in the field. If you can handle small tools comfortably and could build a small backyard project, you can absolutely do this. Start with a small system and add to it later. I often build small systems just for emergency power or powering refrigerators / freezers in power outages.  The full course gives you all the skills required to build a system of any size.

Best of luck with your solar projects!


 

 

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