A Layman’s Guide to Planning and Designing “Off Grid” Energy Systems…
If you are a “Do It Yourselfer” and are planning to design and build your own off grid energy system, then you’ll find this guide very helpful. In particular, you will gain a general idea of the cost involved with each component of the system, but most importantly, you could save money. Firstly, let’s understand, if you are not a trained and qualified contractor, forget about grid tied systems  Grid tied systems involves dangerous work around HIGH voltage and in most countries, it’s illegal to even touch anything connected to the power lines unless the person working with grid connections was suitably qualified and licensed. Off grid power systems however, are not grid connected and so is legal to work with, but that doesn’t necessarily mean it’s safe. If you do have some basic understanding for electricity, then please read on...
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This Basic off grid energy system (below) is comprised of: a 100 amp MPPT charger controller, 6000 watt pure sine wave inverter, 6 x 2 volt deep cycle batteries and solar power can be up to 5000 watts. 
Intro...
I find that planning and designing the energy system is easiest by first starting with the battery or bank of batteries and then working out how much energy will be consumed from the batteries, to then finally working out how much solar power will be needed to replace the used energy. Please note; working from a 24 hour period, we can deduce at least between 5 – 8 hours of available sunlight will be available within that period. The remaining 16 – 19 hours are without sunlight, so careful design of storage requirements should be taken into account given the perimeters.
(above) basic energy system (2Kw)
Let’s begin…
When choosing the energy system, knowing the load that will be powered by the system is the #1 primary important factor  Next, you will need to know the time that the load will be powered for. Once you know the load, and the time it will be powered for, you can start by working out the battery capacity that you’ll need. To do that, you will need to use the total watt hour rating of the load, i.e. I want to power a 100 watt light for 7 hours, so  100 watts for 7 hours, equals, 700 watt hours total and then dividing that by the battery voltage, i.e. 700 watts divided by 12 volts = 58.33 ampere hours (Ah) we get the ampere hour rating a.k.a. AH. So for this example, you would need a 58 Ah battery or larger or rounded off to the nearest higher available value, at 12 volts – Please note, this is the bare minimum for the above example.
(Above) 12 Volt, 260 Ah AGM (Absorbed Glass Mat) Deep Cycle Battery
When choosing a deep cycle battery, choose and AGM type, as they are the best. Avoid using car batteries for storing solar energy, because these batteries were not built to withstand the charge and discharge cycles of an energy system. Deep cycle batteries under a controlled environment (i.e. charger controller), can fully discharge and then recharged without causing damage to the battery. A car battery under similar conditions will not last very long.
6 volt deep cycle batteries, generally does quite well and retains energy better than 12 volt types. These could be connected in series to form any size network. Even better than 6 volt batteries are the 2 volt type. The 2 volt type are commonly used for homes that operate 100% independant of the grid.
TIP!
Deep cycle batteries are expensive but there are ways for getting them cheaper, here's some tips:
Next, are the solar panel(s): Calculating the solar power requirements can be simple; one easy way to work out how much solar power you will need, is to divide the total capacity of the battery by the amount of hours sun will shine on the panels; the number you end up with is the solar power you’ll need – To work out the amount of solar energy you will need, simply divide the battery storage (i.e. 700 watts) by the time the panels will be receiving light from the sun, i.e. 700 watts divided by 6 hours = 116.67 or rounded to the nearest, higher value, i.e. 120 watt solar panel. To work out the storage capacity in watts for a battery: Ah rating x battery voltage = Storage capacity in watt hours, i.e. 58.33 Ah x 12 volts = 699.96 watts. Check out this article: How many solar panels?
(Above) 100 watt, 18 volts Monocrystalline solar panel
When choosing solar panels for an array, ensure that all the panels within a series connected array are of the same power rating. If connected in a parallel network, then panels of different power values can be connected, but they must all be the same voltage rating.
TIP!
Solar panels have come down quite significantly in price, but still, it's not within everybody's price range, so here's a couple of tips that could help get them cheaper:
(Below) 12/24 volt, 30 amps,
solar charger controller
Working out the type of charger you will need involves working out the maximum capacity of the solar power divided by the battery voltage, i.e. 120 watts divided by 12 volts = 10 amps. So in this example, you would need a 10 amp solar charger controller. The charger controller usually has a regulated 12 volt output, which can be used for some 12 volt dc powered appliances. Choosing the right solar charger may depend on the total expected battery storage  So if my future battery bank is going to be 2000 Ah, 48 volts, then I am going to need a charger that can replace full capacity within the batteries. Say for example, we used up all the energy in a 2000 Ah battery bank. If that were the case, then we will need to put 2000 Ah back in! This would have to be accomplished during the time that the solar panels will receive sun light. So say for example, the solar panels only get 6 hours of sunlight a day, then that would mean we would have 6 hours each day to charge the batteries back to its full capacity. So if our battery bank were of 2000 Ah capacity, then we could divide the capacity by the amount of sunlight that will shine on the panels, so for example: 2000 Ah divided by 6 hours = 333.33 Ah. So our system would need to produce 333 Ah per hour to fully recharge the battery bank. Working out the power for a 48 volt system is: 333.33 Ah multiplied by 48 volts = 16000 watts. So to fully charge a 2000 Ah, 48 volt battery bank from fully flat and within 6 hours, you will need 16000 watts of solar panels and a charging system capable of producing 16000 watts per hour (in a 6 hour period). So the type of charger would have to be around ~350 amps!
The best type of solar charger controllers are MPPT (Multi Power Point Tracking) types, which can also be cascaded with other similar chargers.
Working out the type of inverter that you will need requires a couple of things. Firstly, what are you powering? Does the appliance you want to power work from 12 volts DC or 240/110 volts AC? If AC, you will need an inverter. The size of inverter you will need will depend on the load rating of the appliance you plan to power and the type of appliance you want to power, for example, if powering sensitive electronic appliances, such as computer or plasma TV, then a Pure Sine Wave inverter (recommended) is what you will need, but for appliances such as lights, toaster and power drill etc. a modified Sine Wave or Square Wave inverter is sufficient, these type of inverters are usually cheaper than their pure sine wave adversaries, so knowing this bit of information can save you money. Choose an inverter that has a larger capacity than the load it will power, i.e. For a 200 watt TV, choose a 500 watt inverter.
(Above) 2000 watts, 4000 watt peak, Pure Sine Wave Inverter
Choosing a really large Pure Sine Wave inverter is the ultimate goal, however, this could set you back a few dollars! When choosing an inverter, choose the biggest that you can afford. If you are like most us solar DIYers, then wisdom has it, you will want to go larger later on!
Some appliances may not require an inverter, such as a light for example. In that case, the light or other can be hard wired to the charger output – This output is usually indicated as “load” on the solar charger. The load output is ideal for 12 volt lighting or even a 12 volt TV!
Examples...
Below is an example of a basic system and some of the calculations you will need to know, if planning to design and build your own energy system. The calculations and designing are based on a 12 volt, 100 AH deep cycle battery…
System specifications:
Here’s how much you can power, based on a 100 Ah battery 
Load (watts) 
Run Time (hours) 
Examples 
100 watts 
12 hours 

200 watts 
6 hours 

400 watts 
3 hours 

Calculations for the above chart:
Solar power needed to charge battery, from completely flat.
Solar Panel (watts) 
Charging Time 
Charger capacity (amps) 
100 watts 
12 hours 
10 amps 
200 watts 
6 hours 
20 amps 
240 watts 
5 hours 
20 amps 
Calculations for the above chart:
Solar power is definately the way of the future. I just wonder, what happens when the majority of households are run by solar power  Does that mean electricity prices increase further to make up for the lack of business? I can see the power company losing business to individuals that choose to make their own electricity and I think this will be common place in the future. In Australia, literally every second household has solar power on their roofs. It is used extensively here and I just wonder if the high energy prices ($0.26 cents per KWH) has anything to do with it. I can't be sure, but one thing is certain, the power company doesn't have as many customers as they did 10 years ago and they will lose many more!
Now, let’s take from my own experience to show how easy it can be in designing your energy system – My computer needs to run for 24 hours and it has a power draw of 500 watts. I needed a system that could cater for that, so I first started with the battery. I needed to power the computer off, of the batteries for at least 16 hours – So I calculated that 16 hours multiplied by 500 watts equals: 8000 watt hours or, 8kw. Now, I needed to know the battery size, so I calculated that as: 8000 watts divided by 12 volts equals: 666.67 AH. So I needed a 12 volt deep cycle battery of 666.67 AH. I chose 3 x 260 AH deep cycle batteries connected in parallel, which has a total storage capacity of 9,360 watts.
Next, I chose a Pure Sine Wave inverter of 2000 watts, with a 4000 watt peak output. 500 watts of the 2000 was going to be the drive power for the PC. I chose 2000 watts because I may want to power other appliances in the future.
Now, I needed to work out how much solar power I was going to need for the system. I took my figures from the lowest light levels of the year, which is during winter. We get at least 6 hours of direct sunlight average during this time. What I needed to do is, work out how much solar power I would need to replace the charge (energy) that was used the night before, which was 500 watts for 18 hours. So, 18 hours multiplied by 500 watts equals 9000 watt hours, and, 9000 watts divided by 6 hours (sunlight) equals: 1,500 watts. So my system required 1,500 watts of solar panels to charge the batteries and an extra 500 watts to both keep the batteries charging and keep the computer powered. So the total solar power that I needed for my system was 2000 watts worth of solar panels, which equates to 8 x 250 watt panels.
The solar charger was calculated at the full capacity of the solar panels, which was: 1500 watts (2000 watts500 watts) divided by battery voltage 12 volts equals 125 amps.
The system runs 500 watts of power continuously for 24 hours! It saves me $1,160.64 a year (At $0.26 per Kwh, we have one of the world's highest electricity prices) and has a payback time (returns) of about 2 and a half years. The system is not affected by blackouts or any power failure associated with the power lines. Connected to the system is a backup generator and then grid connected. So if power fails for both solar and generator, then control goes to the grid. The system is designed to only use the grid as a last resort. The generator takes priority over the grid and the energy system takes priority over all.
Currently, I am “eyeing” off some 2 volt, 2200 AH batteries. 6 of these batteries would be ideal for an off grid energy system that could power everything! The batteries alone have a 28,800 watt storage capacity, but I would need at least 5000 watts of solar panels. This is when we enter into the realms of industrial power systems and on that note, I have to stop right here. If you want to read further about off grid energy systems, then check out this page
TIP!
Here’s a tip that could save you dollars: Go to eBay (the best auction site) and locate the components that you need, starting with the battery. Getting a real bargain could take some time, but what you will save makes it all worth it. For example, I won a $1000.00 battery, for less than $380.00 and a 100 watt solar panel for $43.00! Getting these bargains is not easy. You will have to watch the best deals and then bid on last seconds! Yes I got a super cheap solar panel, but that took some careful watching and about 2 weeks… Be patient! Oh, and make sure you check the postage costs and insure that it’s within your budget – if not, move on or look for free shipping.
Below (eBay) is the deal I missed out on  Some lucky person won a 200 watt Monocrystalline solar panel for $46.00 bucks!
As you can see, it can be done; you can get extremely great deals  patience pays!
Final Notes
Building your own solar panels is still a fun project and could save you some money, but at the current prices that solar panels are selling for these days, I don’t know if it really is worth the effort anymore, to build your own solar panel rather than to buy it already built. Besides, when the difference between building it to buying it is about $20 bucks, I think it’s worth paying the 20 and saving yourself the effort.
Also, when choosing a system, in my opinion I think it’s best to go for the biggest inverter you can afford and as well as the biggest charger controller – Everything else is scalable, so you can add additional batteries and solar panels when practical to do so.
"Make It Solar Powered"