Tired of roughing it without electricity? Batteries that work for only a few days? Generators that disrupt a serene campsite? How about clean, quiet solar power that is environmentally friendly, requires little maintenance, and is free, once you have paid for the equipment and installation. Solar systems are available in capacities from "trickle chargers" to keep batteries charged while parked in storage to sufficient power to run most of the appliances in a trailer, pop-up or motorhome.
With solar power, electricity is produced when sunlight strikes the photovoltaic (PV) cells. Voltage depends on the type of semiconductor material used, whereas the cell area and the intensity of the light determine the amperage. By connecting together a sufficient number of individual PV cells, you can obtain the Watts of power needed. While brilliant sunlight is of best, PV systems will work on cloudy days but with reduced output.
Solar power is used with batteries with the PV cells charging the batteries so energy is available when the sun goes down and to handle peak loads. A charge controller or regulator prevents over-charging. Some of smaller systems use self-regulating solar modules rather than a charge controller. More complex systems include meters to monitor system operation and fuses for protection. You will also need an DC to AC inverter to power appliances that run on AC current.
Deep-cycle batteries are preferred over ordinary automotive batteries. Deep cycle batteries can be repeatedly discharged and recharged, that is "cycled", and discharged to a very low level, thus the term "deep." By contrast automotive batteries are primarily designed to supply powerful, short bursts of electrical energy for starting. Then the alternator takes over and recharges the battery as well meeting electrical needs when the vehicle is running. Deep cycling, that is almost completely discharging, will result in a much shorter lifetime or even a premature failure for automotive SLI (starting, lighting, ignition) batteries.
When choosing the PV and battery system, it must have enough Ampere-hour capacity. Usually the Ampere-hour rating is given along with a standard duration reference, typically 10 or 20 hours. If the specs say the battery is rated at 80 Ampere-hours with a 10 hour reference, it means the fully charged battery will provide 8-Amperes for 10 hours. If the current drain is greater, the time will decrease. Since Watts are determined by volts, times amperes, a 12 volt, actually about 14 volts, this 80 amp-hour battery is capable of 960 tp 1,120 Watt-hours.
To determine the system size needed, pick a typical day and list the DC lighting and appliances used and for how many hours. Read the specification plates on appliances to determine the Watts used. If only the amperage is given, multiply this by 12 Volts to obtain the Watts consumed. If there are no specs available, this list can help in making rough estimates. Note a DC battery allowance representing the Watt-hours the battery bank uses to store energy for DC appliances (about 20 percent) should be added.
|Fan - Ceiling||25|
|Fan - Furnace||48|
|Lamp - Incandescent||25-75|
|Lamp - Florescent||20|
|Television - 9" color||48|
|Water Pump - Circulating||32|
For AC appliances, repeat the process, except now multiply amperes by 120 Volts to determine the wattage. For AC appliances without tags, this list can be used for estimates. Here add an the battery power allowance plus the amount of power the inverter uses to convert DC power to AC power (about 35 percent of the AC daily energy budget) should be added.
|Coffee Maker||375 - 550|
|Lamp - Incandescent||75 - 100|
|Microwave Oven||300 - 1000|
|Refrigerator - 12 cu. ft.||350|
|Television - 19" color||175|
|Toaster||1100 - 1250|
Add up the total Watt-hours used to arrive at the total daily energy budget.
Individual solar modules are available that provide from around 5 to 100 Watts. Multiply this by the number of hours of sunlight you can expect on an average to obtain the output of the module in terms of Watt-hours.
It is important that the solar panel be oriented so that it receives the maximum amount of direct sunlight during the prime sunlight hours from about 9 am to 3 pm. Even something as simple as the shadow from an utility pole or shade from a tree can noticeably reduce the sunlight input to the solar cell. Tilting the panel towards the sun can improve the efficiency. The amount of tilt depends on your latitude. The angle of tilt is measured from the horizontal and the panels should face south.
|0 to 15||15|
|15 to 25||angle is same as latitude|
|25 to 30||latitude + 5|
|30 to 35||latitude + 10|
|35 to 40||latitude + 15|
|above 40||latitude + 20|
There are several companies that offer solar power systems specifically for RVs and motorhomes. They range in sizes from a 5-10 Watt units designed as a trickle charger for a 12-Volt battery plus provides some power for small appliances to 225 Watt systems. Ranging in cost from under a hundred dollars to well over a thousand dollars, they are ready to install coming with controls, connections and mounting hardware. Installation can be done professionally or by competent do-it-yourselfers. Designed for the rigors of camping, these solar panels are weatherproof plus UV, shock and hail-resistant for long life and dependability.