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== Introduction== This is a pretty exciting area and we see more RV owners looking into solar power to keep themselves off grid, extend boon docking adventures, or in some cases for better battery management. My hope for this page is to provide some information as I see it today. Most of my information has come from reading information from different sites on Solar, and my own personal usage. *'''National Renewable Energy Lab''' ** http:////www.nrel.gov/gis/solar.html *'''Northern Arizona Wind & Su'''n. ** http://w//www.solar-electric.com/ These guys have been in business since 1979. They have a ride range of good products for solar modules, Batteries, Inverters and Renewable Energy Systems. They have lots of good FAQ's on solar. *'''AM Solar''' ** http://www.amsolar.com/ AM Solar is another company that just does solar for RV’s. They have a couple of good pages dedicated to solar education, although somewhat mixed with marketing. == How Much Power Do I Need == The first thing that you need to do is figure out how much solar you need. That can be a little difficult if you are planning a whole new RV for the first time. The advice given to many new SMB buyers is to get it prewired for solar. This will let you get some real usage models from real camping experience and you can decide where to go from there. Let’s say you have a SMB with one 4D AGM battery (210 AH) or 2 Group 27 (2 X 100AH or 200AH). This is a pretty standard configuration in one of these rigs. So let’s use 200AH for our basic calculations, in general we try not to run our batteries below 50% so that really only gets us around 100AH of discharge. So if you were using 100AH of power in a day then you would need to be able to put back into the system a 100AH of power. On average a 140 Watt Panel will give you about 40 AH (7.91amps 5 hours full power) a day. I get that value by first assuming that you are only using your RV in the summer months, obviously that is not always the case. Let’s look at some maps from the NREL. :[[FILE:Map pv us annual may2004.jpg|frame|none||'''Annual PV Solar Radiation''']] :[[File:Map pv us june may2004.jpg|frame|none||'''June PV Solar Radiation''']] :[[File:Map pv us december may2004.jpg|frame|none||'''December PV Solar Radiation''']] :So you can see that available power from the Sun is going to be based off of when and where you camp. So if we can get on average a 40AH charge back from a 140 watt panel, two panels would give us back 80AH, still 20AH shy of our 100AH theoretical limit. Do I really need 100AH, probably not, first let’s look at one of our bigger power consumption devices the refrigerator. The standard fridge uses about Standard 3.0 amps at 50% duty cycle. This gives us (3.0 * 24) *.50 or 36AH. This would use a good portion of our available 40AH charge back provided by a single 140 watt panel. You would have 4AH left over for some miscellaneous lighting, lap top charging, etc. :Ok, but what if I want to run the inverter? :[[File:Battery Usage.PNG|frame|none||'''Battery Usage''']] :This excel chart shows 4 different AC items being used, the first is a 1000 watt coffee pot, it pulls about 83 amps. It takes about 9 minutes to brew a pot of coffee. This alone drops over 10 AH from the battery. The next is the laptop charging, this starts pulling about 7.5 amps and slowly gets down to about 4 amps after a 40 min charge, that loses another 5 to 6 AH. Then it is time for some microwave popcorn, again it is about 80 amps for just over 3 min for another loss 4.2 AH. Then we move to the 1500 watt hair dryer, at 125 amps for just over a min, we drop another 2AH. So in just over a 1 hour and 20 min I was able to use about 25 AH. The following is a graph of just the coffee pot. Looking closely you can see when I turned the inverter on prior to starting the coffee pot, just having the inverter on draws a amp or two, without even running the coffee pot. The good thing that shows up on these graphs is that my refrigerator cycle time is not even close to 50%, but then again this was done in the winter. :[[File:Coffee pot.PNG|frame|none||'''Coffee Pot In Use''']] :So for me my big use is a pot of coffee a day and my refrigerator, depending how hot it is outside I am looking at about 30 to 40 Ah subtraction a day. So my choice was a single 140 watt panel. ==Panels== {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:Kypcera 140 watt.jpg]] | style="border: 1px solid darkgray;"| [[File:OM150.jpg]] | style="border: 1px solid darkgray;"| [[File:Grape Solar GS-S-160-Fab8.JPG]] |- align="center" | '''Kyrocera 140 watt $265.00'''|| '''AM Solar GO160 Solar Panel $299.99'''|| '''Grape GS-S-160-Fab8 $264.99''' |} :The following are the common specifications that you will see listed when purchasing a panel :{| style="width: 60%; height: 100px" border="0" |Pmp Power || maximum power (Watts) |- |Vmp Voltage || maximum power (Volts) |- |Imp Current || maximum power (Amps) |- |Voc Voltage || open circuit (Amps) or voltage at no load on panel |- |Isc Current || short circuit (Amp) |} :These are almost always listed under Standard Test Conditions (STC) or 1000 watts per square meter of sunlight intensity, hold a cell temperature of 25°C (77°F), and assume an airmass of 1.5. Because this is a not realistic outside of a lab, you will sometimes see Normal Operating Cell Temperature (NOCT) ratings. NOCT recognizes a bit of reality and assumes the following: 800 watts per square meter of Sunlight Irradiance, an average of 20 ° C (68°'F) Air Temperature, an average wind velocity of 1 meter per second (2.24 miles per hour) :To get a better understanding I have taken numbers off of a Kyocera Panel that is commonly used on SMB’s The KD135SX 135 watt & KD140SX 140 watt, 12 volt Solar Panels. :{| style="width: 60%; height: 100px" border="0" |+'''Standard Test Conditions (STC)''' |+STC = 1000 W/M2 irradiance, 25°C module temperature, AM 1.5 spectrum* |- | || KD135SX-UFBS || KD140SX-UFBS || Unit |- |Pmp || 135 || 140 || W |- |Vmp || 17.7 || 17.7 || V |- |Imp || 7.63 || 7.91 || A |- |Voc || 22.1 || 22.1 || V |- |Isc || 8.37 || 8.68 || A |- |Ptolerance || +5/-5 || +5/-5 || % |- |- |} :{| style="width: 60%; height: 100px" border="0" |+'''Nominal Operating Cell Temperature Conditions (NOCT)''' |+NOCT = 800 W/M2 irradiance, 20°C ambient temperature, AM 1.5 spectrum* |- | || KD135SX-UFBS || KD140SX-UFBS || Unit |- |NOCT || 45 || 45 || ° C |- |Pmax || 97 || 101 || W |- |Vmp || 16.0 || 16.0 || V |- |Imp || 6.10 || 6.33 || A |- |Voc || 20.2 || 20.2 || V |- |Isc || 6.78 || 7.03 || A |- |} :Now it may make a little more sense why you never seem to get 140 watts out of a 140 watt panel. In reality the KD140SX at NOCT at 45°C (113°F) is really about a 100 Watt Panel. If that is not confusing enough then look at below at some additional spec data that they provide. Kyorcera also provides a temperature coefficient table. This would actually let you calculate the output of the panel with a TNOCT at any temperature. Do you really need to do that? No, but the key take away here is as the panel temperature goes up the Voltage (Vmp) goes down. :{| style="width: 60%; height: 200px" border="0" |+'''Temperature Coefficients''' |- |Pmax || -0.45 || -0.45 || %/ ° C |- |Vmp || -0.52 || -0.52 || %/ ° C |- |Imp || 0.0066 || 0.0066 || %/ ° C |- |Voc || -0.36 || -0.36 || %/ ° C |- |Isc || 0.060 || 0.060 || %/ ° C |- |Operating Temp || -40 to +90 || -40 to +90 || °C |- |} ::System Design ::Series Fuse Rating 15 A ::Maximum DC System Voltage (UL) 600 V ::Hailstone Impact 1 i n (25mm) @ 51mph (23m/s ::Subject to simulator measurement uncertainty of +/- 3% ::'''KYOCERA reserves the right to modify these specifications without notice.''' :So what if the panel you are looking at does not provide the NOCT data? While it would be nice if they all did I would not say that it would be a deal breaker, I would say that they need to provide you with a STC data at a minimum :The key specification we are looking at in the STC data is (Vmp) and not (Pmax). Let’s say I have two panels both with a Pmax of 140 Watts, would they not work the same? Well looking at our power formula we use Pmax = Vmp X Imp : :Panel 1 is 140W = 17.7 V X 7.91 A and Panel 2 is 140W = 13V X 10.7A. Why would we want a Panel1 versus Panel2, they both put out 140W and panels 2 puts out more amps. As we saw above as temperature goes up the voltage output of a panel goes down. In very hot conditions the panel can lose almost 20% of their voltage output This would take our 17.7V Panel1 and put the voltage at 14.16Volts, while our 13V panel 2 would be at 10.4 Volts. :What else to look for, is the process used to make the panel. Currently the two major ones are Poly crystalline versus Mono crystalline panels, so what are the differences here. The following article from http://www.civicsolar.com/resource/monocrystalline-vs-polycrystalline-solar-panels gives a great explanation of the difference in the two processes.The key take away is that mono crystalline panels are more costly compared to the same size polycrystalline panels. Poly crystalline panels have an efficiency of 13% to 16% efficiency while mono crystalline panels have an efficiency of 15% to 20%. Mono crystalline panels also have better performance when the temperature goes up. :Most polycrystalline panels have a warranty of 25 years. Mono crystalline could last up to 50 years. Of course the advantages of mono crystalline comes at a cost, as in higher price. :I have left out another segment, Thin Film Solar Cells. The flexible panels that you see are usually made out of Thin Film Solar Cells, there are some various technologies but in general their efficiency ratings are somewhere between 7% to 13%, but one advantage is that high temperatures and shading has less impact on the performance of the solar panel. :You are also starting to see some “flexible” panels being made with Mono Crystalline technology. ===Junction Box or MC4=== You are actually getting less choice on this lately MC or Multi-Contact 4 (latching) are becoming widely used on the majority of panels over 100 watts {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:MC$ Connector.PNG]] | style="border: 1px solid darkgray;"| [[File:MC4 Removal tool.PNG]] |- align="center" | '''MC4 Connector'''|| '''MC4 Removal Tool''' |} This in some ways make connecting the Solar panel or panels in a standard way. Also if you were to start out with one panel you could easily add a second one with the appropriate connector. {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:MC4 Parralel.PNG]] | style="border: 1px solid darkgray;"| [[File:Capture MC4 Branch.PNG]] |- align="center" | '''MC4 Parralel'''|| '''MC4 Branch cable''' |} You can purchase an extension cable, to run from the panel to your controller. Get one that is twice the length that you need and cut in half, you then have both a female and male end. The MC4 cables come in 10AW and 12AWG. They are outdoor rated and sunlight resistant {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:MC4 Extension cable.PNG]] |- align="center" | '''MC4 Extension Cable''' |} {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:Junction box.PNG]] |- align="center" | '''Junction Box''' |} You may also find panels with just a Junction Box, the junction box lets you attached standard cable terminals to the panel outputs, some will allow room to connect additional panels in parallel or series and some you may need a separate combiner box. Kyocera makes two 140 watt panels, the KD140GX is a MC4 connector panel while the KD140SX has a junction box. Doubling up panels, if you have two panels you can either put them in parallel to each other or in series with each other. In almost all cases you are going to stick with parallel over series. First If I put two panels is series I am going double my voltage and keep the current the same, using the Kyocera as an example I would have Vmp of 35.4 volts and an Imp of 7.91. Well the only way you can make use of this is with a MPPT controller, going in series with a PWM controller would be a complete waste. Also if you are hooking panels in series you need to make sure the panel has a bypass diode or install one yourself. Shading really hurts the performance of panels in series, so if that is remotely going to be an issue, it is not advised to go in series ===Blocking Diodes=== :Most panels do not have blocking diodes installed and most controllers incorporate a nighttime disconnect feature. ===Bypass Diodes=== :Many panels have a Bypass diode already installed, Bypass diodes are not needed in a 12 volt system. == Solar Controllers == ===Types=== {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:Blue sky.jpg]] | style="border: 1px solid darkgray;"| [[File:Morningstar_tristar.jpg]] | style="border: 1px solid darkgray;"| [[File:Sunsaver.jpg]] | style="border: 1px solid darkgray;"| [[File:Samlex .jpg]] |- align="center" | '''Blue Sky'''|| '''Morningstar Tristar 45'''|| '''Morningstar Sunsaver'''|| '''Samlex SCC30AB''' |} Samlex .jpg ==== Shunt Controller==== :These are very basic, just turning on and off a certain battery voltage levels. Other than the fact that they are cheap and reliable (only because of the limited number of parts), they should not really be considered for long term solution. They usually have only one battery setting, and a very limited charging algorithm. ==== PWM ==== :The next type would be a 3 Stage with PWM. The three stage means that they have 3 stages for battery charging, Bulk, Absorption, and Float. PWM stands for Pulse Width Modulation, and means that it can control both the current level and duration of the current pulse. Overall this results in better battery charging and longer life than just a on off controller. A good PWM controller will have different battery set points for different battery types, other features may be voltage sensing and temperature feedback. ====MPPT==== :A good PWM controller should work for most van setups, but for a little more money you get the next level called MPPT or Maximum Power Point Tracking. This does not have anything to do with tracking the sun, instead its goal is to maximize the power output of solar panel. MPPT controllers are only useful if you have a high Vmp of at least 17.5 volts. Since to charge are batteries we are looking to provide a bulk charge of 14.3 volts (Lifeline AGM @ 77 f) you can see that we have some headroom of 3.2 Volts Vmp (17.7) – Battery Set point (14.3) = 3.2 volts. So the goal of the MPPT controller is to take that extra power that we are leaving on the table, because if we just regulate the voltage down to 14.3 we are only getting still only getting the Imp (7.91 A) out of the panel. So the most power we can get out of the panel is 14.3V * 7.91A or 113 Watts. With the MPPT charger we are trying to get closer to the 140 Watt output so it comes the current becomes 140(W)/14.3(V) = 9.7A Which give me an increase of almost 1.8 amps (22%) over a standard PWM charger. Note: none of these calculations take into account power loss from conversion, and or cable loss in your system. So at least on paper it looks like MPPT controller would be worth the extra cost. Well then we get back to that real use situation again, remember that we have the issue of the effect of temperature on the output of the panel. Remember the NOCT rating for this panel at 45°C or 113°F was a Vmp of 16 volts with an Imp 6.33A or 101 Watts so are equations change 14.3 * 6.33 = 90 Watts , compared to 101/14.3 or 7.06 amps so now we only get an increase of .73 amps or 11% increase . So is a MPPT controller really worth it? I think a lot depends on your location, number of panels you have and such. In the northern latitudes in December you are looking for any extra output that you can get out of your solar system, and because the temperature would be cooler you could get the most out of MPPT controller. For that matter when you think about your standard charge cycle with solar it is going to start in the morning when the temperature affect is much lower, this is also the time when you want to put out the most current that you can, (bulk phase) and as the temperature heats up you should hopefully be moving to the lower current absorption and float stages. :So if I had Mono Crystalline panel (less affect from temperature). If I had multiple panel (such as two 140 watt panels) or if my panels Vmp was over 18 volts I think I would put a check mark next to MPPT charger. ===Features=== As with a good PWM controller you will find some options such as Battery Types, Temperature compensation, voltage sense wires, Float voltage timers and more. ==== Battery Settings==== :One of the most important Settings for a Charge Controller would be battery charge settings :{| style="width: 60%; height: 200px" border="0" |- ! ||Battery ||Absorption || Float || Equalize || Absorption || Equalize || Equalize |- ! ||Type || Stage(v) || Stage (v) || Stage (v)|| Time (mins) || Time (mins) || Interval (days) |- !1- ||Gel || 14 || 13.7 || 15 || || || |- !2- ||Sealed* || 14.15 || 13.7 || 14.4 || 150 || 60 || 28 |- !3- ||Sealed* || 14.3 || 13.7 || 14.6 || 150 || 60 || 28 |- !4- ||AGM/Flooded || 14.4 || 13.7 || 15.1 || 180 || 120 || 28 |- !5- ||Flooded || 14.6 || 13.5 || 15.3 || 180 || 120 || 28 |- !6- ||Flooded || 14.7 || 13.5 || 15.4 || 180 || 180 || 28 |- !7- ||L-16 || 15.4 || 13.4 || 16 || 180 || 180 || 14 |- !8- ||Custom || Custom || Custom || Custom || Custom || Custom || Custom |- |} :The above are the settings from a Morningstar Tri Star MPPT controller, they provide 8 different battery settings, actually 7 and one that you can program yourself. Do you really need to have all that flexibility? While 8 setting might seem like overkill I would think you should at least have three Gel, AGM, and Flooded. As you can see they also have equalize stage available, while this is nice I would not consider this a must have feature, mainly because you probably also have this feature on your Inverter/Charger. :Another feature that this Tri Star controller has is a float voltage timer, what this says is that once you go into float mode you need to go below the float voltage for 30 mins cumulative, this helps prevent things like the refrigerator coming on and sending the controller back to the Bulk Charging phase. ==== Temperature Compensation ==== :Many controllers have temperature compensation. All charging settings are based on 25°C (77°F). If the battery temperature varies by 5°C, the charging setting will change by 0.15 Volts for a 12 Volt battery. This is a substantial change in the charging of the battery, and the use of the Remote Temperature Sensor (RTS) is recommended to adjust charging to the actual battery temperature. ==== Battery Voltage Sensing==== :Even with proper cabling from controller to battery you will have some voltage drop between the battery and the actual controllers terminals, this drop means that your actual voltages that your controller are set to take action on are wrong, For this reason higher end controllers will have voltage sense wires, They can be between 16 to 24 AWG wires, that go from the controller to the actual battery terminals, because they carry no current the voltage is the same at the battery terminal and the controller. This will give the controller a more accurate reading of your battery voltage. ====Displays==== :Almost all controllers will give you some kind of display, they may range from some LED lights to a multitude of information such as total amp hours or total system charge watts, or they may even break those into daily output. I am pretty much a strong believer in having a separate Battery Monitoring system, so I don’t really need it tell me much about the battery, I do believe the panel voltage and current from the solar panel would be my minimal must haves. This becomes more a preference issue, and in many higher end controllers you can purchase a remote display. ==Installation== ====Panels==== [[File:Roof Mount.png|frame|left|alt=Roof Mount.|'''Roof Mount''']] I was able to install my panel using the Yakima Tracks that were already installed on the van. The panel is raised up off the roof slightly to provide good airflow under the panel. You can find many examples of roof mounted systems. You may also look into the ever popular portable market, a big advantage of this may be that you can park the rig in the shade but still have your panels in the sun. Or even better, a combination of the two can be used. {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:Portable.png]] |- align="center" | '''Portable''' |} ====Solar controller==== A big part of the install is going to be the controller. I am of the opinion that I want to make the distance from the controller to the battery to be a minimal distance. If you already have an inverter-and/or – charger, you probably want to install it relatively close to the same location. The reason for this concern is voltage loss, since the controller is really being used as a Battery Charger, I think we want to make sure that the voltages that we are providing during the different charge phases are as accurate as possible. My connection to my battery is very short run of 6 AWG wire (less than 2 feet) and the rest of the run is 1/0 AWG at 10 feet which gives me a voltage drop of 0.00802 Volt from the controller. My longer run of 10 AWG 16 feet is from the Panel to the controller, using NOCT of 16 Vmp I still get a less than 1% drop of 0.13030 or a voltage of 15.869. {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:Voltage_Drop_Calculator.JPG]] |- align="center" | '''Voltage_Drop_Calculator''' |} The following is pretty much a standard install for solar in a SMB, With some controllers you may be limited to mounting locations depending if the control panel can be remote or not. In the below diagram the Morningstar Tristar -45 has a remote panel, this allows more flexibility in keeping the controller close to the battery. Other features of the Tristar are voltage sense cables (small gauge twisted pair cable for voltage monitoring) and the temperature probe for temperature compensation. In this example my long cable runs are from the Panels to the controller, the short runs are from controller to battery. {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:Perm Solar.JPG]] |- align="center" | '''Permanent Solar Install''' |} The example below is the same as the previous permanent mount except, now I have added a portable solar panel. In many cases the portable panel comes with its own controller, with this set up we remove the controller and run the panel out put in parallel with the existing permanent controller. I use a MinnKota MKR-18 12V Plug & Receptacle
 (40 Amp)to connect from the outside of the van. To be able to do this you need to know that the panels have relatively the same specs ad the permanent panel. {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:Perm & Portable Solar.JPG]] |- align="center" | '''Permanent & Portable Solar Install''' |} The following diagram is again like the above but we remove the permanent panel. Again we may have to remove the existing controller and go directly to the controller from the panel. While the cost of a permanent controller may sound like an extra expense, with this configuration we are getting the accuracy that is expected from a good permanent mount controller. {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:Portable 2 Solar.JPG]] |- align="center" | '''Portable Solar Install with separate Controller''' |} Now when we look at portable solar panels we many times see that the controller is located on the actual solar panel. This will be very good if we are worried about the panel Vmp to the controller, in the case of PWM we would not care. But let’s now look at the Controller to the battery, many of these say the cable was 5 meter or 16.4 feet, that is of course without even connecting to the battery yet. Add another few feet to get to the battery and we are at 20 feet. Here we are looking over a 3% voltage loss. For 14 AWG or over 2% for 12 AWG. So with the voltage at 13.5 the battery could be getting 13.04 or 13.21 Volts instead of the 13.5. {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:Portable 1JPG.JPG]] |- align="center" | '''Portable Solar Install with its own Controller''' |} This is a good time to look at the angle, obviously with a portable panel you probably have some easy way to control the angle. There are all sorts calculators do figure out what your best angle should be. One being located at http://www.solarelectricityhandbook.com/solar-irradiance.html or http://www.solarelectricityhandbook.com/solar-angle-calculator.html. I have attached some photos of the calculators here, if you are really interested in figuring out the best angle please go visit this site or one like it. For a panel attached to the roof, I don’t think I would find value in making it adjustable, obviously with a portable you could take the time to set up the correct angle. ==== Angle Calculators==== {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:Solar Irradiance figures flat.PNG]] | style="border: 1px solid darkgray;"| [[File:Solar Irradiance figures best all year angle facing south.PNG]] |- align="center" | '''Solar Irradiance Figures Flat'''|| '''Solar Irradiance Figures Best All Year Angle Facing South''' |} {| cellpadding="2" style="border: 1px solid darkgray;" |- align="center" | style="border: 1px solid darkgray;"| [[File:Solar angle calculator.PNG]] |- align="center" | '''Angle Calculator''' |} * '''''In Progress'''''

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