Solar Power for Caravans,
RV's and Camper Trailers
Solar panels or solar modules
– solar power can be an initial expensive
cost but it is one of the cleanest (and quietest) forms of
power. Solar panels convert light into electrical energy
and the amount of energy captured is determined by the
number of solar panels, the angle of exposure of the solar
panel to the sun, the size or the number of cells in
parallel of the solar panel and your location ie: ‘peak sun
hours’ (determined by the latitude and the season as well as
the time of day). This light energy is converted to
electricity and a solar regulator regulates the charge to
the deep-cycle batteries.
Average daily sunshine hours maps showing
‘peak sun hours’ are available from the Australian
Government, Bureau of Meteorology website.
Solar panels in daylight are ‘live’ so care should be exercised in
handling or testing.
looking into solar panels you will come across the term
‘photovoltaic’ (PV) which Wikipedia defines as ‘the
field of technology and research related to the application of solar
cells for energy by converting solar energy (sunlight, including
ultra violet radiation) directly into electricity (solar
Solar panels are made up of cells and there are three
types of cells – monocrystalline solar cells, polycrystalline (or
multi-crystalline) solar cells and amphorous solar cells. These
solar cells are then physically and electrically joined and placed
in a frame forming a solar panel or PV module. A number of solar
panels joined together is called a solar array.
BP Solar and Kyocera use polycrystalline or
multi-crystalline cells in series for their solar panels. BP Solar
states these type of solar panels charge batteries virtually in any
panels or solar modules come in various sizes and capacity
ranging from 5W up. To some extent the number of solar
panels and the size of the solar panels you can have or fit
to your RV will be dictated by the dimensions of the roof
and the available space after the placement and number of
roof hatches such as the four-season hatch or skylight as
well as any roof top air conditioner.
panels are heat sensitive so that is why you see them mounted on a
bracket spaced above the roof of your caravan or RV leaving some air
space underneath them for cooling. Also, as the solar panels are
heat sensitive they produce less power when they get hotter
particularly in the north of Australia and even around Brisbane in
summer as the writer has experienced. Some solar panels are less
affected by some shade, some will completely shut down if shaded by
as little as 5%, but as yet no solar panel will work in complete
Rivers * has stated - ‘Outputs vary from type to type, but in
typical RV installations most solar modules produce a bit over 70%
of their apparently claimed output. Many modules have a small panel
on their rear face that shows what they actually produce. For an
'80-watt' module this is usually about 58 watts’. Collyn
suggests dividing the watts by 16 or 17 (not 12V ie: 80W ÷ 17 =
4.7A) for a truer output.
* Reproduced by express permission, Collyn Rivers,
Caravan & Motorhome Books, Broome, WA 6725. This article is
protected by Copyright. www.caravanandmotorhomebooks.com
Using the example above, 22 watts is ‘lost’. Essentially the solar
panel may be rated 80 watt at full sunlight at a particular
temperature but if the temperature is too hot then the voltage
produced is less than the rating. There is a feature called Maximum
Power Point Tracking (MPPT) used in some of the more expensive solar
electric charge controllers which you could investigate further.
Wikipedia defines MPPT as follows - 'Maximum
power point tracking (MPPT) is a technique that grid-tie inverters,
solar battery chargers and similar devices use to get the maximum
possible power from one or more photovoltaic devices, typically
solar panels, though optical power transmission systems can
benefit from similar technology. Solar cells have a complex
relationship between solar irradiation, temperature and total
resistance that produces a non-linear output efficiency which can be
analyzed based on the I-V curve. It is the purpose of the MPPT
system to sample the output of the cells and apply the proper
resistance (load) to obtain maximum power for any given
environmental conditions. MPPT devices are typically integrated
into an electric power converter system that provides voltage or
current conversion, filtering, and regulation for driving various
loads, including power grids, batteries, or motors.'
Essentially, the power point
tracker is an high frequency DC to DC converter that takes the DC
input produced by the solar panels, changes it to high frequency AC,
then converts it back down to a different DC voltage and current to
exactly 'match' the panels to the batteries. A MPPT is used to track
the maximum power point as the sun, cloud cover and heat build-up or
cool-down of the solar panels changes the output. The charge
controller monitors the output of the panels, compares it to the
battery charge and converts it to the best voltage to input the
maximum Amps into the battery/ies.
Recently released microprocessor
controlled MPPT models know when to adjust the output that is being
sent to the battery and completes any adjustments needed.
Recent advances have also made
way for use of solar panels with lithium batteries. For example,
Kedron Caravans now offer a Lithium battery option, through
Enerdrive products, to reduce weight in their off-road caravans.
Kimberley Karavans also have a lithium battery option.