Have you ever really gotten anything free? Why does there always seem to be a catch!
Believe it or not, many RV’ers are now getting electrical power FREE- from the sun… without using a power cord!
An RV is probably the best type of unit to be able to use solar power since most of the on-board electrical systems are designed to work from 12 volts DC. Only the microwave and the air conditioner are tied to120 volts AC.
The typical motorized RV comes with a chassis battery that is used to start the engine, and two deep cycle coach batteries to operate lights, pumps, furnaces, radios, etc. - some even have a generator.
The RV coach batteries are quite different from the common automobile battery. Most RV’s will use either “group 24” or “group 27” batteries for the coach. A “group 24” battery can provide 70 ampere-hours of energy at a 10 ampere discharge rate. “Group 27” batteries can provide 90 ampere-hours of energy at a 10 ampere discharge rate. That means that if you draw 10 amperes of current from your battery for a period of 9 hours, your battery will be completely discharged. Two batteries would allow you to use the 12 volt systems for 18 hours. If you draw 50 amperes from one battery it will roll over and play dead in 70 minutes. As higher currents are drawn, the battery can provide current for a shorter time. For best results use Absorbed Glass Matt (AGM) sealed deep cycle batteries since they do not allow any gasses that might corrode sensitive electronic equipment to escape.
The RV generator is used to provide 120 volts Alternating Current (AC) to run the air conditioning system or microwave, and its output is converted to 12 volts Direct Current (DC) to charge the batteries. RV generators can be installed that will run on gasoline, diesel, or propane fuel.
Any way you look at it, when you have an chassis mounted RV generator it costs money to generate electricity… the generator itself can cost $4000 or more even though it may be used for only a few hours each month. To properly maintain the generator, about $300 in parts and labour is required for every 400 hours of use. During this time, the generator will also use about $425 in fuel. The generator is most often operating when you are driving down the road and you want to cool the vehicle with the roof air conditioning system. The only time you can run the rear or bedroom air conditioner on some RVs is when the generator is operating. This rear roof air unit is only connected to the generator, unless you have an RV with a 50 ampere 220 volt system.
Many RV owners have found that a small portable generator is a much more practical way to power their 120 volt appliances when “dry camping” – away from a campground electrical hookup. Portable generators are quite affordable, and offer an alternative to the larger RV generators – but their output is limited, and they cannot be operated while the vehicle is in motion.
Going Solar!
With the advances in modern solar power, RV enthusiasts can enjoy the convenience of a renewable source of energy at a very low initial cost. A 220 watt panel solar array can be installed for about half the cost of a generator. It never makes any noise, it does not require fuel of any kind to operate, causes no pollution, and there is no yearly maintenance fee. It even works when the RV is stored outdoors, quietly keeping the battery system in top working order. All of these advantages come with a ten year warranty.
Most of the people who install solar panels on the roof of their RV use the system to keep their coach batteries up to full charge. As long as there is some daylight each day, the batteries can be topped up, even if the RV is in storage and not being used. Since nothing in life is really “free” the replacement of batteries is the weak point in the solar power system. An RV battery that is not kept properly charged will have a short lifespan. Batteries can cost $90 to $150 each and seem to need replacing every two years.
The key to optimum performance from your solar power system is the selection of the appropriate batteries. A battery is like a pail of water - when you take two gallons of water out, you have to put two gallons back or it gets empty very fast. If we take ten amperes of current out of a battery for a period of 9 hours the battery will be discharged. Most converters in RV’s are limited to a 2 ampere charging rate to protect the battery from overheating and gassing. If you have two group 27 batteries installed in your coach and both are discharged, you may need to have the converter in the RV running for 90 hours to replace the electricity. In plain English, it is impossible to recharge both batteries overnight when you are plugged in at the campground, unless you have an auxiliary high current charging system.
The solution is to replace the energy as it is being used, with solar cells. Energy consumed during the evenings can be replaced by the solar cells during the daylight hours. A 220 watt solar cell array can supply up to 18 amperes depending on the brilliance of the sun, the angle the light strikes the panel, and the temperature. Solar cells are more efficient in cooler temperatures so they will lose some of their ability to generate current in hotter southern climates. The light available does not need to be direct sunlight - diffused light on a cloudy day still produces an acceptable amount of current to charge the batteries.
Some of the cheaper solar cell panels are 'self regulating'. That means that as the sun gets brighter, the output voltage keeps rising. But if a cloud blocks the sun the voltage drops down. Units like this are fine for use on a ventilating fan that will only go faster if the sun is bright. That's fine, because that coincides with the time when you most need a ventilating fan. An example of this is the fan installed on the cooling fins behind your refrigerator - this is the device that assists the normal convection air currents to take heat away from the fridge when the sun is beating down. If the sun is not shining, the fan stops working since it is not needed.
Properly installed solar arrays (groups of solar panels connected together) for charging batteries should be installed with voltage regulators and controllers to prevent the output voltage from going too high and “cooking” the battery system. The controller also disconnects the array from the batteries when the array voltage drops lower than the batteries. This prevents the batteries from discharging into the solar cells.
Basic Requirements
One 110 watt panel and a solar controller are usually effective for most RVs operating in the boonies. If more electrical energy is required, an additional 110 watt panel can be connected to the same controller. Remember that conservation of energy helps your battery last longer. During winter, don't turn on all the lights, the TV and the furnace at the same time. RV’ers should consider upgrading their lighting system to fluorescent lamps. Ordinary incandescent (meaning white hot) lamps that are used in RV’s develop 20% light and 80% heat from the energy used, but fluorescent lamps develop 80% light with only 20% heat and have a much greater life span as they are more resistant to breakage from vibrations on the road. There is no white hot filament wire to burn out or break. These lighting fixtures provide much more light with less heat and less current used. Besides saving your battery, you won't need as much air conditioning to get rid of unwanted heat. The only drawback that I have found is that the light from the fluorescent lamps can sometimes confuse the remote control on our VCR.
A solar system will NOT operate an air conditioner, as it draws too much current at 120-volts for a long time. But you can operate a microwave for short periods of time with a device called an inverter. This device will change the 12 volt DC developed by the solar system to 120 volts alternating current to operate equipment other appliances such as televisions, satellite receivers, VCRs, and lights. An inverter is designed to operate appliances that draw low wattage for a long time or high wattage devices for a very short time. One watt is the energy consumed when one volt pushes one ampere through a device. Watts are equal to amperes times volts. Therefore at 120 volts a 1200 watt device draws 10 amperes. Conversely, at 12 volts a 1200 watt device would draw 100 amperes from a battery system. A nine-inch color television receiver that consumes 48 watts at 120 volts will draw approximately one half ampere from the electrical system in the campground, but when you operate it from the inverter at 12 volts the same television receiver would now take 4 amperes from the battery. As you can see, a device or appliance will draw ten times the amount of current from the batteries as it will draw on 120 volts from the campground electrical system.
Some devices draw a significant extra amount of current to get them started. Just think of starting to push a car along the road from a dead stop. It takes more energy to start it rolling than it takes to keep it going. Appliances like lights and motors need this surge of current to get them up and running. It is not unusual for a motor or incandescent light bulb to need ten times as much current to start as it needs to actually operate. This is called a surge rating.
An air conditioner that draws 15 amperes from the electrical system of the campground may require up to 150 amperes for a few seconds to get it working. This is why 15 ampere fuses in campgrounds often blow out when you try to start your air conditioner (especially if it was just turned off a moment before). An inverter would have to draw at least 150 amperes from the battery to keep an air conditioner working and more than that to start it up. Your battery system could not keep up to this demand for current for more than a few minutes.
When solar panels and inverters are installed on an RV, the 120 volt electrical panel should be rewired into two sections. One section will operate the TV, VCR, microwave and other low wattage 120 volt appliances. The other section of the electrical panel will only be live when you are plugged into the electrical system of the campground, or when the generator is running, and this will operate the converter, air conditioner and any other high wattage 120 volt appliances.
When you are connected to the electrical system in the campground or your generator, the two electrical panels in the RV would be automatically connected together by a device called a relay or transfer switch. If you are operating in the boondocks, the only thing connected to the inverter output would be low wattage electrical appliances. The converter of the RV should be turned off during operation of the inverter to prevent it from trying to charge the batteries with the current drawn from the batteries. That's like trying to push yourself up the hill!
The typical RV inverter comes in one of two types. The first, and least expensive type acts like a switch to turn the direct current on and off 60 times a second. This fools a transformer into thinking that it is connected to alternating current. The transformer works on changing currents that create changing magnetic fields. The transformer then changes the relationship between the voltage so that 120 volts of alternating current comes out. This simplified switch type is using what is called square wave switching. The output of this type of inverter is not properly shaped for use with VCRs and some motor type appliances. The modification required to make it operate VCRs, microwaves, and motors needs a more sophisticated switching system of transistors to produce a modified sine wave, or smooth waveform of constantly changing electricity.
The second, and more expensive type of inverter, uses a transistor control circuit to switch the direct current thousands of times a second. Transformers can be physically smaller in construction and weight when they are designed to work on high frequency current. The transformer steps up the voltage, and a rectifier system is used to convert this high frequency 120 volts to 120 volts of direct current. Then a frequency controlled transistor oscillator converts the 120 volts of direct current to extremely stable 60 cycle 120 volt alternating current. This is the best quality inverter to operate sensitive electronic equipment such as VCRs and computers.
The inverter should be mounted in a dry, well ventilated area not far from the battery system so that the 12 volt wiring does not have to be too large in diameter. But, it should NOT be in the battery compartment (unless you are using AGM batteries) because it will be subject to corrosive fumes that come from the batteries during high current drains that occur during operation of the inverter. Remember, the inverter is used for low wattage 120 volt appliances and devices that you need to make life bearable on the road and in the back country campgrounds without the noise of a generator in the background.
Inverters can be purchased that will operate appliances from 45 watts up to 3000 watts. Of course the more sophisticated inverters with the high wattage will cost more dollars. Try to match your inverter to the power rating that will most often be used. Some inverters come with high powered battery chargers that will recharge your battery system at a rate faster than your converter is capable of when you are connected to the electrical system in the campground.
Be sure that you really need the high wattage unit before you spend your hard earned dollars on an inverter than can power something that will only be used infrequently. In our own RV, we use a small wattage inverter to operate the satellite receiver, television set, and laptop. A second, larger unit would be used to operate the microwave when needed.
An RV owner can estimate the number of solar cell panels appropriate for the installation by calculating the total number of watt-hours of energy required for his unit. The wattage drawn is usually marked on a nameplate at the back of each appliance. If the figure shown is amperes, calculate the wattage by multiplying by the normal voltage. Estimate the number of hours each appliance will be used each day, and you can then add up the watt-hour requirements of your RV for the day. Each 62" x 26" panel can generate an average of 110 watts at 12 volts during each hour of direct sunlight. With a worst case scenario of four hours of sunlight each day, each 110 watt panel can generate 440 watt-hours of energy.
Solar energy is a natural for RVs, it will boost your enjoyment of camping in Provincial, State and National Parks where you can operate your RV appliances free of electrical cords and pollution. That’s the eco-friendly way to enjoy RV’ing in the backcountry - catch the sun!
--------------------------------
Typical RV Power Demands
Incandescent lamps 24 watts each
Fluorescent lamps 20 watts
TV 9" Color 48 watts
Stereo radio 30 watts
Water pump 32 watts
Furnace fan 48 watts
--------------------------------
Solar Suppliers
Carmanah Technologies
Victoria, BC
www.carmanah.com
ICP Global Technologies
Montreal, QC
www.icpglobal.com
Matrix Energy
Kirkland, QC
www.matrixenergy.ca
Kyocera
Scottsdale, AZ
www.Kyocera.com/solar
Siemens Solar
Camarillo, CA
www.siemenssolar.com
(Page
Top) |
