Solar Panels

This article relates to the solar panels fitted to our motorhome and I should point out that there are numerous different panels for sale and as time moves on it is inevitable that there will be improvements in efficiency that will only serve to make solar even more cost effective in the future.

Our Panels

Type: Polycrystalline Photovoltaic Sizes: 2 x 130 Watts and 2 x 87W Output: 7.39 amps and 5.5amps Price range: £400 – 520 Size: L = 1425; W = 652; D = 56 mm Weight: 12.2 kg/8.7kg

 

The Rationale My initial reason for wanting a solar panel (or panels) was to extend the life of our leisure batteries during periods of wild camping when EHU was not available. I had experience of solar panels many years ago during my years of sailing and was not impressed. They only worked under ideal conditions and that rarely happened, producing only a small amount of power relative to a fairly large size, heavy panel. This new generation of solar panels was reported to be much more efficient and lighter than the previous generation and in a small way contributes towards reducing global warming. In an ideal world the panel or panels would replenish all the power we consumed during a 24 hour period and give us a form of self sufficiency. I can hear all the voices saying ‘how naive can this man be’ Well on paper is should be possible, however in reality; well read on.

Fixed or Rotating I spent a considerable amount of time researching the issue of fixed verses raised and rotating panels. I reviewed all the posts in the forums, even starting a couple myself. I accept that for the same size panel a rotating one could produce up to 2+ times more power than a fixed panel over a full year.  I used the MHF solar panel calculator to assess power output etc. and came to the conclusion that a large fixed panel would be more useful than a small rotating panel and of course, cost much less. In my particular case 2 x 130 w plus two 87W panels would cost significantly less than a single 75 or 100 W rotating panel and, using the MHF calculator and manufacturers fact sheets, getting (in ideal conditions) 25+ amps for 5 hours a day from our fixed panels in the summer was better than 5 amps for 10 hours a day for rotating panel. Cost must come into the equation and rotating panels at £2200+ plus fitting and possibly additional accessories such as a wind vane, verses around £1250 for two 130 watt and two 87W panels, the Kyoceras wins on economics alone. I chose the Kyocera because of a combination of price, output and size in relation to roof space availability. I also have the option of adding a 5th additional panel if needed for an extra £400. So far I have 434 watts or, using the calculator, the potential of up to 396 amps per day in summer in the south of France.    I’m sure the debate will go on and on regarding this topic, however based on output and cost this was my decision.

Fitting the Kyoceras was easier than I thought as I was able to bolt the 130 watt panels on to the roof bars, allowing me the option of removing them if needed to transfer onto another MH if necessary. Actually this turned out to be a smart move on my part as I changed MH’s some 10 months later and was able to swap the panels over very easily. I utilized an existing hole to route the cables and I fitted the regulator in a locker out of sight and ran the wires direct to a bus bar and to the leisure batteries. I opted at a later date, for the split charger device (£100) that directed the majority of the charge to the leisure batteries and 1.5 amps to the engine battery. The whole job was done in a day without any drilling of holes in the roof.  I didn’t fit the two 87W panels until later.

Results Throughout the summer months the two Kyoceras produced on average, around 150 amps of power per day. Some days were better with over 200 amps registering on the Sterling Battery Management System, others were much worse at around 80 amps. There were one or two days of bad weather when we were down to no more than 40 amps. (its these times that total battery power available comes into its own).  Bad weather would affect both rotating and fixed panels, however a fixed 130w would still work out much better than the theoretical maximum of the 75 w rotating panel. We are heavy users of mains electricity and the leisure batteries are linked up to a 2.5 kw inverter to power our mains only microwave, electric kettle, toaster, TV and a variety of chargers for the phone and cameras.  Using these 240 volt appliances also help reduce the amount of gas we would use.

We were fortunate to be parked next to a French Motorhome owner who had the Alden Phenix panel and we were able to compare output over a couple of days while in the Camargue. At 7pm in early September the Alden was showing 4.2 amps while our Kyoceras was showing 5.2. At midday the following day the Alden was showing 4.8 amps while the Kyoceras showed 17.9 amps. In reality both fixed and rotating panel types rarely operate to maximum efficiency and ideal conditions are few and far between. The Kyocera would still produce something even on grey rainy days and on good days would produce around 3 amps from early in the morning rising to almost 14 amps after 11 am through to 3 pm dropping back to 5 or less after 6pm. The fixed panels however are pretty poor in winter months and even with 434W panels we are getting less than 20 amps per day when the sky is cloudy and cold in northern England with the sun low in the sky – at a time when we are using more electricity during the long nights and very short days. I am not convinced that a 100w rotating panel would be that much better during winter but concede that it would be a little better at northern latitudes. One clear day in December, the regulator on the Kyocera went up to 5 amps and gave me a total of 25 amps for the day but that was exceptional and not the norm. I am not convinced that fitting another panel would improve matters a great deal. We have sufficient power in summer and another would not help much in winter. One obvious tip though – we park our MH under trees on our drive when not in use and it is surprising the effect dirt can have on solar panels and we have found that cleaning them before each trip improved performance significantly.

 

 

Pros 1. Much cheaper than rotating panels 2. Smaller footprint on roof (size for size) as you don’t have to worry about rotating diameters 3. Can make you self sufficient in summer, more so the further south you go.

 

Cons 1. Not very efficient during winter months – when you arguably need more power 2. Don’t buy solar panels if you are justifying them on break even or positive return against the cost ofEHU. They are convenient but you can buy a fair few amps of electricity for the cost of solar panels 3.  Parking can be a problem on some sites where there are lots of trees.  Solar panels don’t like trees and even partly shaded panels will loose much of their power

Verdict Overall I’m pleased with the Kyocera (s) and don’t regret the purchase. It has taken some 4 years to get our money back as we use the camper for approximately 20 weeks every year, but they are worth it to eliminate the time of getting out the generator or having to go to a site with EHU. During the summer and winter we spent six weeks wild camping and have never needed the generator once.   I still deliberate on fixed verses rotating types but remain convinced that we made the right decision. As stated earlier, we are heavy users of battery power so I would expect more frugal users to make more efficient use of their power. Our solar panels make us self sufficient for pretty much the whole year. The introduction of MPPT controllers will add a new element to the debate however for me I need to be convinced on two points.  One is what is the difference in performance between a £100 MPPT controller and a £400 controller?  Secondly what are the true gains between PWM and MPPT?.  The sales information would suggest up to 40% increase in output for a given size solar panel – if true that would be worth it.

 

Finally over the past years I have spoken and listened to fellow travellers that have purchased solar panels from as small as 5 watts to 50 watts and they have been generally disappointed in the results so my advice to those would be don’t mess around – buy the largest panel you can afford as only then will you see any benefit on your investment and usage.  In my opinion you need at least 100W+ to have any real impact and if you only use campsites and always use EHU then any solar panel – large or small is a waste of money.  The usual rationale given for using a small panel has been – I only use it to keep the battery topped up during winter – if I can only get 20 amps in winter in northern England using 434W of panels then think what a 20W panel will produce.  Also note that engine batteries will discharge at rates of up to 6 amps per day under normal circumstances so topping up with an average of 1 amp per day isn’t going to help that much.

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