|
|
|
|
Basic Solar Information
A good place to Start
| This section is a great starting point for anyone interested in solar power (photovoltaics), and all that is associated with it. Here we will list out all the components required in a typical solar installation, in the order which they perform their duties. If at any point you feel that you are getting lost, or need more information you can check the Definitions Page, Wiring Pages, the Solar Map, e-mail us, or even give us a call toll free at 1-877-367-3925. Our staff is very knowledgeable, friendly, and always willing to answer questions. Determining how much electricity you use per day Ok, now is time to break out the calculators, slide rules, abacus, or take off your socks, it's time to do some math. First we will need to determine how many watts of electricity you utilize in your household, RV, Cabin, or other application. To help you with this open the Load Worksheet, and print it out. Ok, now that you have your load worksheet in hand you will want to grab a pencil and run around the house looking at your appliances. On the back, side, cord, bottom, of any appliance in your home you will find a sticker or a stamp that gives you the voltage and amperage of the appliance. Can't find it? Look again because the FCC and UL require it to be listed. Now, you list should look something like this:
Note: The wattage of the appliance may not be listed. That's OK, take a deep breath, we've got the solution. All you need is the Volts (V) and Amps (A) to determine the Watts (W). The Equation (a.k.a. The West Virginia Law) looks like this: (W) Watts = (V) Volts x (A) Amps Lets look at the Clothes Washer. 120 Volts x 2.5 Amps = 300 Watts Now you chart should look like this:
Now we see how much electricity we use in a day: Multiply the Watts (W) by the hours of operation per day, like this: Clothes Washer: 300 Watts x 2 hours per day = 600 watts per day Now you chart should look like this:
Now, Take you daily totals for each appliance, and total them up. Now, you've got how many Watt Hours you utilize per day. It should look like this:
Now, keep this handy, we're going to need the numbers in a little bit. Solar Panels Solar Panels are relatively uncomplicated when we get down to it. We won't go into too much depth here, but here's what you should know. Solar panels utilize sunlight to generate power through Silicone cells. Solar Panels produce 12 Volts Direct Current (VDC) power (in some cases 24 VDC) Solar Panels come in a variety of shapes, sizes and outputs. We will discuss a little later on how to determine the size of solar panel that you will need, and how many of them. Solar panels may be wired in Series to increase the voltage, or in Parallel to increase to amperage. Need help with wiring look here! Determining the size of your solar array. OK, time to pull the socks off again, we're going to do some more math. First, make sure you've made a visit to our Solar Map and obtained the PEAK WINTER SUN HOURS. Now we figure array size, here's the equation: Total Watts Per Day/ (Divided by) Solar Panel Size/ (divided by) Peak Winter Hours = # of panels For Example: 1450 watts per day 120 watt Panel 4.5 Peak Winter Sun Hours 1450 watts per day / 120 Watts (AP120) = 12.08 12.08 / 4.5 peak winter hours = 2.68518 Panels ALWAYS round up to the next number to ensure that you do not short change yourself. In this case we would need three 120 watt solar panels. Lets do the equation again, but with a 75 watt panel. 1450 / 75 / 4.5 = 4.29629 Round up to 5 There, now you figured you solar array! Solar Panel Combiner Box The Solar Panel Combiner Box is available to help aid in solar panel wiring and fusing. Do you need a solar combiner box? A good Rule of thumb is if you have more than 4 panels in a system you should include this device to help cut wiring costs. Solar Charge Controllers Solar Charge Controllers help regulate the flow of electricity from Solar Panels to the Batteries. They read the voltage of the battery or battery bank and, when a maximum voltage is reached, shut off the flow of electricity to the battery. They are available in 12, 24, or 48 VDC. How do I determine which Charge controller I need? It's really very simple. Included with the information on each solar panel you will find the Short Circuit Current (Isc) in AMPS. For example, the AP120 has an Isc of 7.7 Amps. Now we get in to a general rule of wiring. When wiring panels (or batteries) in SERIES you increase the voltage, but not the amperage. When wiring in PARALLEL you increase the amperage but not the voltage. So....Here's how we figure out you charge control size. For this example we will use 4 AP-120 Watt Panels. For a 12 Volt system the 4 panels would be wired in Parallel, thus: 4 (sets) panels x 7.7 Amps = 30.8 amps For a 24 volt system the wiring break down would be two sets of two series wired panels wired in parallel. In this case the 2 panels wired together equal 24 volts and 7.7 amps per set. 2 sets of panels x 7.7 amps = 15.4 amps For a 48 volt system all 4 panels would be wired together in series resulting in a raise in voltage but no raise in amperage, thus: 1 Set of panels x 7.7 amps = 7.7 amps Note: Remember that increasing the voltage of the system does NOT effect the out put. Remember the West Virginia Law (V x A = W). The only effect that might occur by raising the voltage of the system is higher efficiency. For help with understanding the wiring, please go to Solar Panel Wiring Oh, uh, you might want to leave you socks off for a while, we've got more math coming up in a bit. Determining Voltage Determining the voltage of your system can seem very tricky. Here are some basic guidelines for determining the voltage of your solar system: Recreational Vehicle, Marine Vehicle, or Small Remote Cabin Sites typically 12 VDC Small Residential Applications in remote or intertie connections up to 7500 watts per day: typically 24 VDC with up to 3 days autonomy. 7500 Watts Per Day and Up: 48 VDC Typical The increase in system voltage occurs in order to prevent damage to equipment, including inverters, batteries, etc. Pulling too much amperage over a short period of time makes things very hot, and can damage sensitive instrumentation. Batteries Batteries are usually required in a solar application to store the energy produced during the day to be used during non-sunlight hours. This is your fuel tank after stopping a the local solar quick stop. There are basically three types of batteries. Lead Acid (most common), Absorbed Glass Matte (AGM), and GEL Cell batteries. Lead Acid - batteries are the most common type of battery and are used in many applications, including residential systems. They are called Lead Acid because they are lead plates immersed in an acid solution. Lead acid batteries are available in a variety of shapes, sizes, voltages, and amperages. Usually when the voltage decreases in a battery cell the amp hour capacity will increase. For example there are some deep cycle batteries that are 12 volt, and can hold 85 - 100 amp hours of energy*, while 2 volt cells can hold up to 1900 amp hours energy*. *based on a 20 hour cycle. These batteries will produce hydrogen gas while charging. Make sure to have them in a ventilated area isolated from other electronics that can make a spark. Cost per Amp Hour - Good, Installation - Typical. Absorbed Glass Matte (AGM) - while we won't get too much into their composition, here's what you need to know. AGM Batteries are generally sealed cells, requiring no maintenance. They are also very tolerant to freezing conditions, making them very attractive for remote applications that can't be reached for long periods of time (i.e. remote cabins, transmitters, etc.). Cost per Amp Hour - Medium, Installation - Special Circumstance. Gel Cell - These cells are the most versatile on the market. They boast that they can be mounted in any position, even upside down. These are ideal for marine applications, as well as other conditions where an acid spill would be less than ideal, or even hazardous. Cost per Amp Hour - High, Installation - Special Circumstance, or Marine. Sizing Your Battery Bank Leave those socks off, we're not done yet... Here are a few things to consider. Batteries should not be discharge below 50% of their capacity in order to prevent damage occurring to the plates inside the cell. This is called a 50% DOD (depth of discharge). Batteries have a lifespan equal to a number of cycles. The larger the battery bank, the less cycles it will have to make, the less cycles it has to make, the longer the battery life. I know, it's a viscous circle. To determine the battery system you will need, you will need the following: The wattage per day the voltage (DC) of your solar system How many days of autonomy you want (how many days the system will operate if there is no power produced by your solar panels) OK here goes...the equation is thus: Watts per day / system voltage x 2 (to offset for the 50% depth of discharge) = Daily AMP hours required i.e. 1450 watts per day / 24 volts (DC) x 2 = 120.8 Amp hours per day Now, for example purposes we will use 2 kinds of batteries. The first will be the Exide FS6D. This battery is a 6 VDC Cell with 350 Amp Hours (AH) capacity. Automatically we can see that the AH are high enough for our needs. To get the number of batteries do this: System voltage / battery voltage = # of batteries 24 volt system / 6 volt battery = 4 batteries Now lets determine the system autonomy: Battery AH rating / daily AH rating = Days autonomy 350 AH / 120.8 AH/day = 2.897 days autonomy. Battery Wiring Need help with battery wiring? Look Here! Inverters What is an inverter? An inverter, truly, is a simple thing. It converts Direct Current (DC) electricity into Alternating Current (AC) electricity which is used by any home across the nation. When you go to your wall and plug in your appliances you are tapping in to an AC current. usually 110 Volts, 60 herz (for America) or 220 volts, 50 herz (for European and South American power). How big should my inverter be? Be glad you haven't put your socks on yet, but his ones pretty simple: The Red numbers in the table below are the wattage's used by the appliances while they operate.
Now, we find all of the appliances that operate at the same time. In this case we will say they all do, bringing us to a total of 1600 watts continuous. Inverters are classified by their operating. in continuous watts available (the first 2 numbers in a thousand i.e. 15 for 1500 watts), and battery voltage. Let's say we have a 24 volt battery bank, which inverter will be required?
If you said the 20/24 you would correct. The 20/24 would provide 2000 watts continuous power from a 24 volt DC battery bank. What is surge capacity? Inverters can only provide so much power. The continuous power is rated at how much the inverter can handle before shutting down. The surge capacity, rated in milliseconds, is the power that the inverter can supply for a SHORT amount of time. This ability is provided for instruments that usually contain a motor. Most motors will have a start up amperage, and an operating amperage. The start up amperage can be up to 3 times that of the operating amperage. Make sure to note any large motors in your home, such as a swamp cooler, water pumps, AC, etc. If you have any questions about the surge capacity of an inverter, don't hesitate to call (that's toll free 1-877-367-3925). Can I get 220 VAC out of my inverter? YES! There are 2 ways of getting 240 volts out of an inverter. The first option (and usually the cheapest) is to purchase a step up transformer, such as the T240, which will take 2 wire 120 and output 3 wire 240. Voila, you have power for up to a 1 horse motor, such as a clothes dryer, water pump, or others. The second option, for larger motors, or homes and businesses with multiple 240 VAC appliances, stacking inverters would be the answer. Available as an added option there are kits which will connect two inverters together to put out 240 VAC and 120 VAC. What is a Sine Wave? When analyzing an AC current, utility grade power comes to us in a Pure Sine Wave Format. Most inverters produce a Modified Sine Wave, which is produced in steps. Not all instrumentation will run properly on a Modified Sine Wave.
Do I need an inverter that produces true Sine Wave? You do if you operate any of the following equipment:
None of the above appliances, some motors, and other time sensitive equipment will operate correctly when powered by a Modified Sine Wave. In this case, you will need a sine wave inverter. Note: If you are considering selling power back to the utility company, you can ONLY utilize a pure sine wave inverter, such as those produced by Trace . Does my inverter have transfer switching? Most inverters nowadays do, however, there are some that don't, make sure to read the fine print, or call us. DC Disconnection You will need some method of DC disconnection to go between the batteries and the inverter to prevent any damage to the inverter in the case of a "catastrophic event". A "catastrophic event" can occur when a short happens in the system (i.e. a wrench dropping and making a connection between battery posts). There are two methods of disconnection, either by fuse or by breaker. You should also consider placing a form of disconnection between the solar panels and the batteries in case some work needs to be done to the system. What else will I need? There are a few other little components here and there that will need to be included. These can include Solar Panel Mounts for your roof, or on a pole, Ground Fault Interruption for roof mount applications (required by the UL), transfer switching, battery enclosures, wire, conduit, battery interconnects, a sub-breaker panel, and/or a battery monitor. Can I install this myself??? In many cases, our clients have been able to do most, if not all, of the installation of their system themselves. In fact, it helps them learn everything that is involved in their home power production, and the key points to check IF something were to go wrong. However, having an electrician on standby might be of help in some aspects of the installation (especially if doing a grid intertie system). Make sure to check all local codes before beginning any installation, and call the appropriate people before doing any digging. If you have some kids in your neighborhood, or a local school you might arrange with them to lend a hand. Kids will learn a lot about electricity, energy conservation, and more! Kids are our future, and teaching them about solar will help ensure a cleaner planet in their future. OK...open top of sock, lift foot, and insert foot into sock, your done! We hope we've covered everything well enough to help you out. However, if you still have questions, or need information about a specific product, please feel free to e-mail us, or call us toll free 1-877-367-3925. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
