THOSE CUTE LITTLE SOLAR STORAGE BATTERIES

There are various types of storage batteries on the market today which are used for solar applications. The most common are the lead acid batteries and sealed lead acid batteries. As technology advances toward producing electric vehicles we will be seeing the prices of lithium batteries becoming more accessible to the average user. But until then, most of us will still be mainly using the lead acid batteries. And it is these lead acid batteries I want to address in this post.

Batteries are the backbone to any Off-Grid or Grid-Interactive Solar Installation. They give the life to our alternative electric systems. Batteries like these also get our vehicles started, they are called Cranking Batteries. Cranking Batteries are rated by cranking amps where as Solar Storage Batteries are rated by their amp hour capacity. So whats the difference, an amp is an amp, no?

No, a cranking amp is what your battery can muster up for a rather short period of time. In other words when you crank over your engine it usually happens within a minute, if your vehicle is older it may take several attempts to get it started. And if your vehicle really wants to be difficult you may have to keep cranking it for a longer period of time and as you do, you will notice the battery get weaker and weaker. This is because you are using up its cranking amps. Cranking Batteries are meant to get the vehicle started and then it goes into charge mode while everything in your vehicle or boat runs off the charging alternator.

A Solar Storage Battery stores the amps produced by your generating system (solar modules, wind turbines, micro-hydro turbines, or a fossil fuel generator) up to the amount the battery is rated for. So now you can use those amps to create electric long after the generating source has shut down.

For the most part, you will put a major part of your solar budget into the purchasing if batteries. Because you will want the most amp hours you can afford, your batteries will be either 6 volts or less. This is because the more amp hours your battery puts out, the more lead it will contain, thus making them very heavy. All Lead Acid Batteries are made up of two volt cells such as the two volt battery shown above. A six volt battery is made up of three of two volt cells. When these cells are put together in a neat plastic container, they are referred to as a battery. So when you get into batteries with a thousand or so amp hours, just one cell could weigh a couple of hundred pounds and if you have a forty eight volt system you really want to deal with only batteries that are packaged as one cell.

Okay, enough about types of batteries, this story is more about the importance of battery maintenance.

Why is maintenance important? First of all you have a small fortune invested in batteries so you want to protect that investment. So the most important thing you can do is to think safety when being around your batteries. Keep all flames and sparks out of your battery room!

Always, always, always wear goggles, rubber gloves, an old long sleeve shirt and slacks (this will save alot of ruined clothing) that are just for working with your batteries.

1. Keep your batteries out of your house
2. Provide a separate space for them or put them in a Battery Enclosure.
3. Where ever you put your batteries make sure that they are well ventilated.
   

Here are some of my recommendations and you should get into a habit of doing this at least once a month...

1. Again keep all lit lames away from your batteries!!! I'll give you two incidents I am aware of why this is extremely important before I close this blog.
   
2. Make sure that all your battery terminals are tightened down. Check this every time you do a battery inspection. Loose terminals can produce sparking which can lead to fires and worst.
   
3. The next most important thing you can do is to keep your battery terminals clean. This can be done with carefully using a mild solution of water mixed with a small amount of baking soda (DO NOT ALLOW ANY OF THE BAKING SODA SOLUTION TO GET INSIDE THE BATTERY!!! If you do, you can kiss your battery good-bye.) and scrubing with a copper wire brush. Once the battery is cleaned use a product like Quik-Kote to coat all your battery terminals. This is an acid neutralizing product which will protect the terminals from getting corroded.
   
4. Alway check to make sure your battery liquid levels full (use only distilled water). Low battery water levels help cause sulfation to build up on the batteries lead plates which reduces your batteries ability to hold as many amp hours as it could. There are Battery Desulfator which can help keep your battery's lead plates clean. There is also these little Water Misers, a product which a number of my customers seem to be happy with, which helps retard the rate at which your battery evaporates its liquids.
5. It is important to monitor your battery's acid specific gravity levels as well. This is done with a hydrometer which is placed in the battery's cell opening. The hydrometer has a bulb which you genitally squeeze once its tip is in the acid. Do this about three times and then take your reading. If your readings are in the red, you are reaching the point where your battery's usefulness is about over. I have seen where using a Battery Desulfator has prolonged having to replace the batteries.
6. A key to longer battery life is that when initially installing or when you replace your batteries, always buy your Batteries at one time. In other words don't buy some of them now and then say a year later buy some more. This is a good way to decrease the amp hour levels of the newer batteries.
   

Actually if you want to get more life out of your cranking batteries follow the above first four check points with them as well.

Lastly I want to share with you the importance of why fire and lead acid batteries do not mix. Recently, well in the last few months anyway the woman that works at our local grocery store had a scare. It seems that her husband walked into the dark room where their battery banks were and being that it was dark, he lite his cigarette lighter. And boom!!! The wife who was doing the dishes heard the explosion and ran to his aid. Fortunately the batteries were at the far end of the large room and that she had the good sense to pour water all over him. I say fortunately because if the batteries were near him he would be dead and if she had not poured the water on him, he would be permanently scared and blind. Not a good thing for an author and artist or for anyone for that matter. So be safe.

The second incidence I am aware of happened off Marina del Rey in California. I had been jogging on a coastal path just after sunset, the sky was getting dark when off shore there came a tremendous explosion. I turned just in time to see a ball of flame rising a good 100 feet into the air followed by a column of fire. A yacht anchored off shore had blown up. The next day I learned that the batteries had a loose connection and when the late owner attempted to start the engines, the batteries exploded. There were no survivors.

I would just like to mention one other fact for all you boat owners, and that is the boat also was carrying propane which helped make the explosion so massive. Propane is heavier then air so if there is a leak it therefore seeks the lowest point on the boat. And that is usually the engine room. So if you are going to carry propane I would suggest keeping it on deck near one of the side gunnals so that should it leak it drops toward the sea and not the engine room.

So my friends, be safe and check your batteries health at least once a month.

Terry R. Wolff

SEASON'S GREETINGS

Well with the holiday season here and with all the things that had to be done leading up to them, this blog seems to have been placed on the back burner. As this is regrettable, I have not been sitting idle for I ve been diligently working on up - my solar website at
Solar-Catalog.com.

Now that this is done, I have up-loaded it to the Web and am requesting you to please browse through it and send me your comments regarding how convenient or inconvenient it may be, and it you notice any areas which are not working correctly. Finally I would like to know what sort of information you feel needs to be addressed.

I am requesting this because I have put many hours into this site and I want it to supply the type of information and products that are important to those who are in need of Solar Energy Information. So any help would be greatly appreciated not only by myself but to those who use the Catalog as a resource.

Again I would like to remind you that if you have any subjects which you would like answered on this blog, please address them to
Info@SolarTaos.com

I trust that you are all having a good holiday season. No matter how you celebrate or don't celebrate this time of year, be safe and be happy. I wish you all a wonderful and rewarding 2010 and may your God be with you. And don't forget to light up you life with solar!!!

Terry R. Wolff

SOLARMAGIC POWER OPTIMIZERS

We just got a lead on this new product by National Semiconductor. These power optimizers allow you to get the maximum performance out of your PV solar strings.

Today’s photovoltaic arrays are defined as strings of series-connected PV panels, which are then paralleled together and converted to AC power through an inverter. The key challenge of these arrays is how a small amount of real-world mismatch with just a few of the PV panels can cut the power output of the entire array in half. This mismatch can come in the form of shading (e.g. trees, chimneys, overhead power lines, bird droppings, handrails, etc.), panel-to-panel mismatch, different panel orientations and tilts, or different string lengths.

As a result of these mismatches, system integrators are often forced to compromise their installation by various methods, such as reducing the size of the array to avoid shade, accepting a lower energy output per square meter, or adding extra panels in a different part of the array, all of which cost money, efficiency, and/or aesthetics for the system owner.

To maximize the energy output of each solar PV panel in the array, National Semiconductor has developed SolarMagic technology, which enables each solar panel to produce the maximum energy regardless of whether other panels in the array are under-performing due to mismatch. SolarMagic technology monitors and maximizes the energy harvest of each individual PV panel through advanced algorithms combined with leading-edge mixed-signal technology, thereby recouping up to 57% of the lost energy due to mismatches.

The SolarMagic power optimizer is designed to be installed quickly and easily within the traditional architecture of a solar array. Each power optimizer comes with a universal mounting bracket for easy attachment to a racking system. The output wires of each solar panel are simply series-connected to a power optimizer (positive wire to positive wire, negative to negative), with the power optimizer output wires correspondingly connecting into the next solar panel’s power optimizer.

The blocking diode is designed to block reverse current flow by allowing current to flow in one direction and disconnect the circuit if current attempts to flow in the opposite direction. Due to the interaction, strings with SolarMagic power optimizers installed – also referred to as assisted strings – will have varying voltage levels during energy production hours.

A single blocking diode must be installed in each assisted string to protect the SolarMagic power optimizers from damage.

All SolarMagic power optimizers come with a limited 20-year warranty, thereby ensuring the reliability of the panel-mounted electronics matches the panels themselves.

See Spec Sheet

You can order these items on-line by going to my solar site at my
Solar-Catalog.com/pv_opt.html or go to Solar-Catalog.com and view all the Solar, Wind, and Hydro energy products I have available.

My 2010 on-line catalog is now available for your viewing. This year I have added more products as well as product and design information. Ordering on-line makes it easy for you to order what you need 24/7.

Until next time, I hope that this has been helpful. Starting in 2010 I will attempt to feature an energy product once a week and do an informational article every month. At least that is my intent. I will also attempt to be more regular on my Woodcarving Blog as well. With that said, lets hope that I am not promising too much. If I am, I will let you know and reschedule my plans.

Terry R. Wolff

OFF-GRID COMPONENTS

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.

• Solar Energy – Is readily available when the sun is shining. The Solar Modules change the Suns energy into DC Electric which is stored in Batteries until the Electric is needed.

• 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.

1. 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.

2. 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.

3. 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.

4. 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.

5. 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
   G. Grounding

6. 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.

7. 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.

8. 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.

9. 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.

Terry R. Wolff

TOUCHING BASE

Wow here we are going into November and I am sorry that I have not really had much time to post a new blog. I am working on a few topics but for now I have work to do in the wood shop and my time for blogging is very limited. I will see if I can get something to you perhaps later this week.

I want to mention that for those of you who are reading this as a note on FaceBook, that you can come join this blog and thereby receive the information in the formate that it was intended. I have noticed that FaceBook does not keep the original format when it up loads from this blog. Here is the blog's web address... solarwindinfo.blogspot.com

Terry R. Wolff

SOLAR ELECTRIC SYSTEMS - GRID-TIE

Grid-Tie System - This means that your solar electric system and your local utility are both tied into your home and the electricity can run in both direction (in other words when you are producing more electric then you are using, the excess is transferred to your utility company. When you need more electric then you can produce the electric runs from your utility). A grid-tie system can be either independent of batteries (Grid-Tie) or it can support a battery bank (Grid-Interactive).

Basically how grid-tie works, is that when your system is generating electric, the extra electric is sent to the utility thus running your electric meter backwards (you are either selling or getting an electric credit from your utility). With a Grid-Interactive System, when your system is not making electric you are either drawing electric off your batteries or if your batteries are low, from the utility thus running you meter forward (you are buying or withdrawing your credit from your utility). In some cases you may not presently see any money from your utility company, however each year that has been changing and it depends on your utility company. Depending on your system and usage, you will be able to either lower your utility bill to none existent or at the very least have lower electric bills and in some cases may receive a check at the end of the month. A good example of Grid-Tie at its best is where you have long sunny days in the summer (selling to the grid) and short snowy days in the winter (collecting your summer credits). So my advise is, if you have the utility near by and expect that someday it will be going past your property or if you are already on the grid and are looking to make an investment in the future to seriously consider a system that can be tied to the grid. Also, in an area like northern New Mexico where power surges and brownouts seem like a daily routine than a Grid-Interactive System makes not only a good back-up system but may very well save a lot of unforeseen expense on replacing sensitive electronic equipment such as computers.

All Grid-Tie systems stop selling to your utility should there be an interruption of utility service. This is required by law to protect any linemen that may have to work on the outage problem. A Grid-Interactive System on the other hand will provide you with uninteruped back-up power as long as your batteries are full enough.

Presently there are three types of Grid-Tie Systems.

1. GRID-TIE WITH STRING INVERTERS: This is where your system sells when you are producing and you purchase when you are not producing. The reason why the inverters are referred to as String Inverters is because each inverter must be matched to a string or strings of solar Photovoltaic (PV) Modules or Solar Panels.
   
   When you are setting up your system you need to match the inverter you choose to the size and make of module you plan on purchasing. In other words, you can't purchase some panels because you think you are getting a deal and hope that they may work with a grid-tie inverter.
   
   You need to decide what you can afford to invest and make your purchase at one time. You can always add additional inverters and panels to increase your system at a later date.
   
   
2. GRID-TIE WITH A DEDICATED INVERTERS: This is a relativity new technology in the solar market. This system will cost you less to get started. Each solar PV module (solar panel) is connected with its own dedicated inverter. As you may see, with this system you can purchase as little as one inverter and one module and you could be up and running.
   
   To expand your system you just add modules and inverters as you desire. Another advantage is that if some of your modules are clouded over, the remaining will still be selling energy to your utility.
   
   
3. GRID-INTERACTIVE INVERTERS: These systems also have their advantages and disadvantages. Their main advantage is that they can provide you with electric when there is a utility outage because they have a battery back-up. They function much as any Grid-Tie System does except you will have a battery backup when your utility goes down. Here in the Taos area, those on the grid experience frequent brown outs.
   
   Unlike an Off-Grid System you do not have to have a large battery bank, usually enough storage to supply your critical loads for a day or two is all that is normally required.
   
   Another advantage is this type of system can have additional solar modules added at a later date so you can increase your output over a period of time.
   
   This system is not as efficient as the other two Grid-Tie Systems mentioned above
   

Which ever type of system you choose, you will be rewarded for your investment in the long run.

Terry R. Wolff

P.S. There is a glossery of Solar Electric Terms on my Solar-Catalog.com website. If you are unsure about any of the terms used in Solar Energy, this would be a good resource to use. There is also a glossery for Solar Water Heating Terms.

Did you know that New Jersey and Colorado are tied for second place in states installing Grid-Tie Solar Systems with California is still holding at number one.

SOLAR ELECTRIC SYSTEMS - OFF-GRID

The following information may help you with your off-grid system design...

Off-grid systems are electric systems where you are your own electric supplier. In the past, such systems relied on the use of noisy generators to supply the electric. Today however, we are fortunate to have other options such as Solar Panels, Wind Turbines, and Micro Hydroelectric Turbines. This means that you can have a good source of electrical energy even if there is no utility to get it from. So now you can produce electric with the help of our planets natural resources. All three of these methods are producers of DC electric and therefore require solar storage batteries to store the electric you produce. Even though Micro Hydroelectric runs 24 hours a day, you will still have to have batteries plus a load diversion in your design. All of these energy generators are relying on energy sources whose energy output varies. For example the Sun Rays hitting your Solar Panels will increase and decrease because of clouds and the time of day, Wind speeds are also variable causing the electric output to vary as well. So the batteries not only store the electric but also provide a more consistent supply.

Should you wire your electrical system for AC, DC or Both?

To design your system output you need to decide which type of voltage you will use, ie. AC, DC, or a combination of both. Most off grid homes, and some RV's and boats use a combination of both.

I will use our Off-Grid Solar Ranch as an example of a working off-grid independent system.

We have a 15 acre parcel of land in northern New Mexico, which contains our home, office and studio, and our motor home (a converted bus that resembles a boat from inside).

Our motor home and house both use AC and DC, while the woodcarving studio runs strictly on 120 volts AC. The house operates primarily on 120 volts AC with the exception of our hot water Circulating Pump and Booster Pump (12VDC) that provides us with water from our cistern. These two pumps run from a separate self contained system which is made up of our 12vdc panels and batteries which I gave a second life to when I up-graded our solar system from 12vdc to 48vdc. Our well (which is 480 feet deep) uses a 48 Volt DC Lorantz ETA Pump and runs directly off our 48 Volt battery bank. And this Blog and my websites are all generated on computers that are powered by sun and wind power which is stored in Solar Storage Batteries. This stored energy is than transformed into 120vac by an inverter. We started with a 12 Volt input system but once we installed our well, we had to convert to a 48 Volt system. So from my example, you can see how a system can evolve over the decades. I hope this may help you in figuring out your own system.

What about PV System Voltage Input?

Before I go any further on your system's output, I need to mention a little something about your Systems DC input voltage. Today there are three main voltages you can choose from, 12, 24, and 48vdc. 12vdc had been the standard in the US for years before solar became popular. The main reason for 12vdc is that is what vehicles and boats used. As solar use in homes increased the manufactures started looking into more efficient options thus the creation of 24 and48vdc systems. Early on PV Panels were only available in 12vdc but this has now changed.

So which one of these input voltages should you choose?

• The 48vdc systems are the most efficient and also using smaller connection wires. However, you need to take into consideration that you will need to purchase four times as many batteries as a 12vdc system. With this system you can take advantage of the larger wattage of the 24vdc PV Panels. So if you can afford the extra cost of the batteries I would recommend the 48vdc system. Also you might take this into consideration, if there is a possibility that some day in the future you may have access to selling your extra energy to the grid, with the 48vdc system you can just swap out your Off-Grid Inverter for a Grid-Interactive Inverter.
  

• The 24vdc systems are the most common as it uses half the number of batteries as that of the 48vdc system and half the wire size of a 12vdc system. With the 24vdc system you can also use the larger 24vdc PV Panels as with the 48vdc systems.
  
  
• The 12vdc systems are being used less these days mainly because of the limitation in 12vdc PV Panel wattage output (basically from 5 to 140 watts per panel while the 24vdc panels put out 160 to over 200 watts). Also your wiring sizes on these systems is much larger and should be taken into consideration. If your system is going to be strictly DC, a system in say an RV or boat I would recommend the 12vdc system

Back to your systems voltage output

If you have a small system or if cost is a consideration, then you might consider a DC only. DC is simpler and is a less expensive way to go because you will not require having an inverter. I see DC systems used a lot in remote cabins, on small boats, and in under developed countries. However, if you plan to run appliances that you already own (Stereo, TV, Power Tools, Toaster, etc.) you will need an Inverter (an inverter is an electronic piece of equipment which turns DC electric power into AC electric power). Since AC products are more readily available and generally less expensive you may want to run AC. Remember, that if you go 100% AC, you are relying on an inverter. If the inverter goes down there goes your electric. The good news is that today's inverters are very sturdy and long lasting. At the Solar Ranch we run redundant inverters with a backup generator just to be on the safe side. In the near 30 years that I have been living with solar I have only had two minor problems, one was a relay on my original Trace square wave inverter and the other was a faulty temperature sensor.

Wiring your home for both AC and DC is another option. By doing this, you can run both AC appliances, some DC appliance and lights. When you are running your wires to your outlets use 12 gauge wire and if you think you may want to have some DC outlets, run a set of wires for each outlet you want. You can run 10 or 12 gauge wire for your lighting. Run all your AC outlet wires to your main AC Load Center, all your DC outlets to a DC Load Center, and all your lighting wires to a third Load Center. By doing this, you can use either AC or DC lighting depending on which of the other two Load Centers you connect to. This also allows you to change your mind at a later date.

Terry R. Wolff