Setting up an off-the-grid solar system (this means having electric without having access to a power utility or if you do have access, they would be used as an emergency backup much like having a backup generator) usually seems more complicated than it needs to be. I know this by the number of people that call me that are either completely in the dark or darn near to it. So I am writing this to try to put some clarity to this subject.
When you set up an off grid energy system you become your own energy utility company. This means that your system will be as efficient as the components you use. It also means that you are also the maintenance department as well as the systems monitoring department. I only mention this to make you aware of some of your responsibilities and not to scare you. I have been living off the grid for nearly thirty years, most of that full time (meaning that there were a few times when I had access to shore power) and have never experienced any major issues. Back in the 80's I had to have a relay replaced in my inverter and more recently I needed to replace a temperature sensor in one of my inverters (I have redundant inverters so I have one as a backup). The main issue with an off-grid system is the batteries. As a rule of thumb, the more costly the batteries, the less trouble you should have (if you can afford it, industrial batteries are the way to go).
Now that you know what your responsibilities will be, I would like to mention that I personally prefer living independent of the grid. Here in northern New Mexico those living on the grid are subject to occasion brown outs, black outs, power surges, and low voltage. None of this has ever effected me the whole time which I have lived here. While those here who do live with the grid have experienced these inconveniences which have cost them loss of expensive electronics I might add.
So what is needed to have an independent energy system? You need to have an energy generating system, this could be Solar, Wind, Hydro, or a Fuel Powered Generator. The first three cost nothing to run once they are setup. Lets look at each of these four options.
Wind Energy – Relies on Wind Turbines to provide you the energy. Just like the Solar Modules, most of these residential and small commercial unites make DC Electric which is stored in Batteries also. Since Wind Turbines are mechanical, they could be subject to mechanical issues
Micro Hydro Electric – These are great if you have access to enough steady running water. Again they produce DC Electric which is stored in Batteries as well. Likewise, Hydro Turbines are mechanical devises and may be subject to mechanical issues.
Generators, Fuel Based – These are available in either AC, DC, or both. Since generators have combustible engines, making the electric as needed they will be running whenever you need electric unless you are using it to charge a battery bank. Generators run on gasoline, diesel, natural gas, or propane. Using a generator is the most expensive way to generate electric. While generators have been the standard in remote areas throughout the world, they are rapidly being replaced by Solar and Wind which require less operating costs, maintenance and down time. Most of the Generators I sell today are purchased for System Back-up, most of our Sine-Wave Inverters are capable of starting a generator when the Voltage levels of the Batteries become too low.
For sake of discussion I will be talking about setting up a Solar and/or Wind Systems. Hydro Systems use similar components but also needs a few additional such as a Load Controller and a Load Diverter. Both Solar and Wind can be setup independent or used in conjunction with each other as well.
Below is a list of the components which make up an Off-Grid Electric System. I am listing these items in the order in which they appear in the system. These systems can have an input of 12VDC, 24VDC, or 48VDC depending on your individual requirements. I started with a 12VDC System because back then, that is all that was available. Today the 24VDC and 48VDC Systems are more common place as they require thinner wires and the Solar Modules and Wind Turbines can be further away from the Solar Building. I now have a 48VDC System because of our Solar Well Pump but I would recommend a 24VDC System your system with the exception of mobile and cabins where all the Loads are going to be DC. 48VDC Systems require four 6VDC Batteries for every Battery on a 12VDC System. If you are doing a Battery Based Grid-Tie System that you will have to use a 48VDC input.
Electric Generation – This would be a Solar Module (also referred to as a Solar Panel or PV Panel) or Solar Array (two or more Solar Modules) and/or a Wind Turbine or Turbines. These will produce DC Electric which needs to be stored in a bank of Batteries for current or future use. Other than pumps all AC and DC loads require Batteries and they provide a more stable voltage level.
Mounting System – Both Solar Modules and Wind Turbines need to have a way of mounting them. For Solar Modules there are a number of Mounting Systems available from Pole Mounts, Ground Racks, Trackers, Roof Mounts, and RV Mounts. Wind Turbines are mounted on Wind Towers, Roof Mounts, and Marine Mounts.
Combiner Box – These are Breaker or Fuse Boxes which mount to the Mounting System. The purpose of these is to isolate each Solar Module and to allow you to only have to run two wires back to your Solar Room/Shed.
Solar Building – This is where you keep all your Components, Disconnects, and the Battery Bank to protect them from the elements. Whatever you choose to use, this is entirely up to you and I am only mentioning this to bring it to your attention. Just make sure that you allow enough room to move around and that there is a minimum of three feet in front of the Inverter and Disconnects.
DC Disconnects – These are Breakers which are used to isolate various components from each other. Some times there are more than one Breaker Box but today there are DC Disconnects that are designed for Solar Systems. These Disconnects include space to do all your DC Wiring and Breakers to isolate the...
A. PV Panels from the Charge Controller
B. Charge Controller from the Batteries
C. Ground Fault Breaker
D. Inverter(s) from the Batteries
E. DC Loads from the Inverter(s)
F. Lightning Arrestors
a. At the Combiner Box or base of the Wind Tower
b. In the DC Disconnect
c. In the AC Disconnect
Charge Controller(s) – Every Battery Based Solar System requires a Battery Charge Controller. The Controller protects the Batteries from becoming over charged and distributes the charging Amps in three Phases - Bulk, Float, and Equalize. Controllers range in Amp output from as small as a couple Amps to 80 Amps. If mixing different size Solar Panels or if the Amperage is more than 80 Amps than additional Charge Controllers would be required. There are two types of Controllers, PMW and MPPT. They will be further discussed in another posting. Some Wind Turbines come with built-in Controllers.
Inverter(s) – These convert DC Electric to AC Electric. Not all Systems have AC loads and if they don't, then an Inverter would not be required. When it comes to Inverters, there is a wide range of them, ranging from small cigarette lighter models and up from there. Here we will be referring to the most common which are used in homes. These are Modified Sine Wave or Sine Wave Inverters. Some Inverters include built in chargers and can be set to accept Utility Power or start a Generator if the Voltage in the Battery Bank fall below a predetermined Voltage.
Solar Storage Batteries – These are Deep Cycle Batteries needed to store the electric which is produced by the PV Panels or Wind Turbines. Due to weight and cost issues most people will choose using a commercial grade Battery which come packaged in six Volt units. All Batteries consist of 2VDC Cells which are packaged together to form larger Voltage Batteries ie. 6VDC, 12VDC. The 6VDC L-16 Batteries are the most common as the only weigh about 130 pounds each. Industrial Batteries can weigh up to 1,000 pounds per Cell and multiply that by 6 and you have one heavy Battery, so these are not a convenient as the commercial Batteries. The Batteries are wired together to create your required Voltage so if you are doing 24VDC with an L-16 you will need to wire four of them together to create one Battery. To increase the Amp Hours (AH) you need to do this in increments of four Batteries per Bank. For example, I have a 48VDC System presently with sixteen L-16 Batteries. This is 2 Battery Banks of 350 AH each which gives me a total of 700 AH.
AC Disconnect – This includes all the Breakers that are required for disconnecting the Inverter, Loads, and By-Pass if you are going to be connected to the Grid or a Generator. The AC Disconnect is where you will do all your AC Wiring.
This completes my list of the main components which you will need to get yourself started to being self sufficient from Utility Electric. What I find interesting that during the past several years there has been a big push in the industry toward Grid-Tie and yet I find that there are a good number of people that just want to be off the grid even though they may be in a position to sell electric back to their Utility. So we have been selling Off-Grid Systems along with Grid-Tie Systems to the same customer. Whatever your needs are feel free to contact me and see whats available.
The above image is similar to my OutBack System except that I have two Charge Controllers on my System. From left to right I will explain what we have here. The box on the left is the AC Disconnect Box, just to its left is the Communications HUB, to its right are the two OutBack VFX Inverters, to its right is the DC Disconnect Box, and finally to the far right from top to bottom is the MATE Systems Control Unit, and the MX60 MPPT Charge Controller. The reason for the redundant Inverters is so that there is a back-up should one of the Inverters have to be taken out of service, to provide additional charging Amps during back-up charging from the Generator, and finally it shares the Load when the demand on the master Inverter reaches three-quarters capacity. These two Inverters are set up so one is the Master and works all the time and the second is a Slave Unit which is called into action only when required. OutBack Systems are the flagship of our product line but we offer components from all the major manufactures.
I hope that this answers your questions and has been helpful to you.