Solar Power Designer Explains Some RV Applications

June 29, 2009 by · Leave a Comment 

Editor’s Note: Miguel Scaccialupo is a qualified solar power systems designer and solar panel consultant. This article was distributed by

Solar power systems are a great addition to recreational vehicles that are used for any length of time in remote areas. They are relatively simple to install and if well maintained can provide years of clean, reliable electrical power without having to resort to the use of noisy generators which produce pollutants and greenhouse gases.

Most RV solar power systems of any size will require three or four basic components: solar panels, batteries, regulator (charge controller) and inverter. The solar panels are the source of electrical energy, which is converted directly from sunlight by the silicon cells in the panels. Batteries store this electrical energy and make it available for use at any time of the day or night. A regulator is required to maintain the batteries in a good state of charge and to prevent harmful overcharging. An inverter is necessary only if main voltage AC power is required.

Solar panels are manufactured in three basic forms: monocrystalline, polycrystalline and amorphous. These terms refer to the type of silicon cells used. While monocrystalline panels are typically the most efficient, there are good reasons to consider amorphous panels as they are much more tolerant of heat and shading than other panels, and they are also more robust. The only drawback associated with amorphous panels is that a larger area of panels is required for the same energy output.

While many types of batteries are available, the most practical and cost effective solution remains the tried and proven lead-acid battery. In a recreational vehicle, sealed AGM (absorbent glass mat) or gelled electrolyte batteries are a good choice as they cannot spill electrolyte (sulphuric acid) and can even be mounted on their side or upside down if necessary. These batteries are also low-maintenance because the electrolyte does not require regular topping up. AGM and gel batteries must be charged with care, however, and it is especially important to avoid overcharging. This is the job of the regulator or charge controller.

Regulators control the charging voltage supplied to the batteries, ensuring that it is high enough to maintain a good state of charge without overcharging. Overcharging is a problem as water in the electrolyte is boiled off, making the sulphuric acid stronger and decreasing battery life, but also creating explosive hydrogen gas. It is therefore important that batteries are always well ventilated. A wide range of regulators is available, with the more advanced models providing multiple charging modes (boost, float and equalization) and features such as programmability and data logging.

While it is possible to source 12-volt DC versions of most appliances, there is a growing trend towards the use of inverters, which make it possible to use standard main voltage appliances with the solar power system. Typically, a greater range of standard appliances is available, at a lower cost, and standard plugs and fittings can also be used. The efficiency of many inverters is now over 90%, meaning that they can be used with little overall efficiency penalty.

RV solar power systems are flexible and can be configured in many ways. The solar system batteries (or “house” batteries) can be configured in parallel with the vehicle battery to allow the vehicle alternator to charge them while they are on the road. Other configurations allow parallel batteries to run power hungry devices and solar panels to charge the vehicle starting battery when necessary.

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