Are you looking for the right solar panel for your house or for your caravan or mobile home? One of the most important decisions before installing a solar system is the selection of the modules or solar panels used. Here you will find important information about the selection and also about other useful components for your power supply at home or on the go.
Because the solar panels are supposed to supply electricity reliably for 30 to 40 years, high quality and efficiency must be taken into account when purchasing. The crystalline cells are still the most common. However, thin-film cells are also increasingly being used. The latter are particularly suitable for sheet metal or foil roofing because they can be rolled up and walked on.
12V or 24V solar system for mobile home, caravan, garden & camping
12V and also 24V solar systems are used for:
In these areas it is often necessary to generate the electricity on site.
Since direct current is generated with solar modules, an inverter is usually not used and devices designed for direct current are used instead. The 12V solar panels are then exactly suitable for the 12V batteries and charge controllers, as well as the consumers.
Incidentally, no electrician is required for cabling in the low-voltage range (12V / 24V). You can complete the installation yourself with proper care. That doesn’t mean that everything is safe here. A short circuit in a battery can be dangerous. So do your research beforehand and, if in doubt, consult a professional.
So can I connect my device directly to the 12V solar panel?
That depends on the device!
Normal household appliances are designed for 230V AC (alternating current). These devices can only be used if you use a 12V 230V inverter that generates the appropriate AC voltage from the 12V battery. So if you want to use 230 V AC devices, you need the right voltage converter in addition to the 12V PV system.
The easier way is to use devices that are built for 12 V DC operation. The solar cells, e.g. on the mobile home, then charge the battery and your devices are supplied with the appropriate direct current via these 12V batteries.
1.2. What is the difference between 12V and 24V systems?
In systems with 12V, larger currents flow through the cables than in 24V systems. This affects the thickness of the cable to be used or the cable cross-section. If a strong current = many amperes flows through a cable, thicker cables are needed. Cables that are too thin heat up and this leads to losses. The less current = less ampere flows, the thinner the cable can be. This means that thinner cables can be used with 24V modules without reaching the performance limit of the cable.
An MPPT solar charge controller works more efficiently with a larger margin between input voltage (solar module) and output voltage (battery). If the voltage drops in 12V modules due to strong heat development (and thus poorer efficiency), then the difference between the input voltage and the output voltage in the controller shrinks. The result is that it no longer works optimally. That reduces the yield.
With 24V modules under the same conditions, these also lose voltage, but the difference (between input voltage and output voltage) remains large enough for the charge controller to continue to work optimally.
Disadvantage: 24V systems are rarer in caravans and mobile areas. If you want to use a 24V system, you have to make sure that all devices are designed for 24V.
How long does the solar panel last?
At least 25 years!
Performance will deteriorate slightly over time (-15% after a number of years) but the module will normally outlive the caravan or garden shed. Many manufacturers give their 12V solar panels a guarantee of 10 years and more.
If there are defects, these are:
cloudiness of the glass
Corrosion on the junction boxes
Degradation (the mentioned loss of performance)
Burn-in caused by spot dirt on the solar modules
Microcracks due to vibration (can reduce current flow in the cell).
How do I have to maintain a 12V solar panel?
You can easily remove the dust with water.
Remove leaves, bird droppings and other punctual contamination, as in the worst case so-called hotspots can burn in (which then reduce the performance of the cell).
Which charge controller is the right one?
Two types of solar charge controllers are used:
PWM charge controller
The PWM charge controller is actually a switch that connects the solar panels to the battery. The system voltage is pulled down to the battery voltage.
2.2. MPPT charge controller
The MPPT controller (Multi Power Point Tracking) is more expensive because it adjusts the input voltage so that the solar system produces the maximum power. Put simply, it adapts the energy to the battery.
For example, there can be a 12V battery on one side of the MPPT charge controller and solar panels generating 36V on the other side.
These solar charge controllers are controlled by a microcontroller and achieve approx. 30% more power compared to conventional PWM charge controllers. So, features of the controller are:
Control via microcontroller
approx. 30% more power
Automatic battery voltage detection (12/24V)
Built-in deep discharge protection
An MPPT solar charge controller is more efficient in cold to moderately warm climates!
Which devices are available for mobile solar systems?
We would like to give you a few tips along the way.
Use TV with the 12V solar panel
Compared to LCD, so-called LED televisions are more economical and the right choice for mobile homes and stand-alone systems.
The size of the televisions varies, of course – and so does the price. From 15 to 22 inches you can expect prices from $80 to $180.
12V TVs can often be used as screens for laptops.
Tip: USB connection, so you can view holiday photos directly.
Audio-Out output: For extra speakers if the sound is too thin.
Headphone output: useful if you don’t want to disturb others
Energy efficiency is important! Pay attention to the highest energy class A.
3.1.1. Can you receive television in the caravan or garden shed?
Most 12 volt televisions have a built-in reception system via DVB-S/S2, DVB-T or DVB-C receiver.
DVB-T: digital transmission via antenna / regional programs only. (e.g. no German channels in Spain). Often sufficient for the garden house. Sometimes an additional DVB-T antenna is necessary.
DVB-C: digital transmission via cable.
DVB-S / DVB-S2: digital transmission via satellite. German language programs can be received throughout Europe. This is the right choice for mobile homes and caravans. A satellite dish with LNB is required (this is aligned manually or automatically, depending on the product).
3.2. Tips for the 12V fridge for camping & mobile homes
Which camping fridge should you buy?
The first question is which type of cold generation makes the most sense in the mobile sector. There are basically three types of cooling devices, which we will briefly explain here.
3.2.1. compressor refrigerator
The refrigerant is in a closed cooling circuit and is compressed. This creates heat that escapes to the outside. In the so-called evaporator, the refrigerant evaporates and generates the cold (when water evaporates on the skin, you notice that it is getting cooler). The principle is simple and the most economical way of cooling.
The compressor refrigerator is technically the better device, energy-efficient and powerful.
3.2.2. Absorption refrigerator GAS / 12V / 230V
A water-ammonia mixture is heated (by a gas flame or electricity) and when it cools down again, the resulting cold is used. Because of the possibility of using electricity and gas, the system is often used in mobile homes.
The absorber fridge runs silently on gas and then does not consume battery power. But he has less cooling capacity. The limit is often reached at temperatures above 30 degrees. Depending on the holiday destination / countries you should pay attention to that!
3.2.3. Thermoelectric cool box
Very inefficient! Useful at most for cooling drinks while driving.
3.2.4. What is better? A cool box 12V or a refrigerator?
The difference is in the opening for filling.
The refrigerator is filled from the side through the door. This gives you easy access to everything stored inside.
The cool box is filled from above. In order to get to the lowest part of the cool box, you have to rummage around.
Cold is heavier than warm air. If you open the cool box, the cold stays inside, so to speak. This saves energy and is perfect for the RV.
3.2.5. Is a 12V fridge necessary or is 230V also possible?
12V fridges are often more expensive but the better choice because,
230V refrigerators require an inverter, which consumes additional electricity. For mobile applications, it is better to pay attention to efficiency!
3.2.6. Save electricity with ice packs in the caravan
Ezetil cold packs are filled with a special agent that freezes/thaws at +6 degrees.
Cold accumulators release the most energy when they change their aggregate state.
During the day (when the sun provides energy), the cold packs are cooled down and the agent in them freezes. Freezing is slow because the transition from liquid to solid requires additional energy.
The refrigerator can then be switched off overnight:
it then consumes no electricity
this saves the battery
the refrigerator is silent
it is cooled overnight by the cold store (which only thaws slowly).
For hobbyists – build a solar panel yourself?
Quite apart from the relatively large effort to create your own solar panels, it is possible to build them yourself. Individual parts such as wafers, frames, protective glass, cables, etc. are actually all available individually on the Internet. In the following video, a tinkerer shows how he solders the solar wafers together and creates his own module.
For a larger system, in order to use the electricity profitably, this procedure is probably not recommended to many. In order to understand the principle of the panel and to try oneself as a photovoltaic manufacturer, DIY solar system would definitely be an exciting leisure project!
4. This is important to choose the solar panel
The thicker the glass in crystalline solar cells, the more stable the cells are. A larger edge distance protects the cells. In addition, the edges of the modules get dirty more easily – which is also why a larger edge distance is advantageous.
For modules with junction boxes, make sure that these are as small as possible, because the cells get warmer at the point of adhesion and impair the performance of the solar panel.
Panels with a white background color are uglier but more effective than those with a dark background color. With the solar panel calculator you can clearly know how many solar panels you should install to meet your daily electricity needs.
4.1. Thin film modules good for large areas
Thin film cells absorb the light better. In diffuse light, the harvest is higher and shading is not as important as with the crystalline cells. They are cheaper to manufacture and are therefore cheaper. The layer can also be vapour-deposited on mobile carrier materials. They conserve raw materials and energy resources during production – the energy payback time is two to three years.
Shortcomings: Lower efficiency, no long-term experience and partly unexplained recycling.
4.2. Do the modules lose power?
No matter which solar panel, all types lose performance after commissioning. That’s called degradation. With crystalline modules, the degradation can take up to 50 hours and amount to up to two percent. After that, they deliver constant performance. By the way, solar panel tax credit is still available for installing solar panels now
Some experts then consider the degradation to be over, while others report further losses of up to 0.5 percent per year. With thin-film modules, a 1,000-hour degradation must be expected. According to this, the system operators have to be prepared for an increase in output in summer and a decrease in winter with otherwise stable output. Which solar panels can actually be expected to provide the best performance?
4.3. Solar panel certifications
The advantage for the customer is when manufacturers specify plus tolerances. Few do so in the +5 to 0 percent range. In practice, solar modules work in summer with a drop in performance of 20 percent. In addition to the 2-year product guarantee prescribed by law, the solar panel manufacturers give performance guarantees of between 10 and 25 years.
The most important institution for certifying the modules is the International Electrotechnical Commission (IEC) in Geneva.
Quality modules have a certification mark (CE), the IEC 61215 for crystalline modules and the IEC 61646 for amorphous modules.
4.3.1. Certification according to IEC 61215 – Crystalline PV modules
This certificate is a quality mark for crystalline panels.
For most national and international funding measures, the IEC certification is a mandatory criterion for approval.
IEC certification according to test certificate 61646
The IEC certification tests how photovoltaic modules behave under the artificial load of influences that have an impact on the degradation of PV modules. The load groups to which the modules are exposed are:
sunlight and UV light
Mechanical stress (snow, hail, wind)
Climate (cold, heat, humidity)
4.3.2. Certification according to IEC 61646 – thin-film modules
This is the test standard for thin-film modules. Here, too, the degradation is tested with regard to:
sunlight and UV light
Mechanical stress (snow, hail, wind)
Climate (cold, heat, humidity)
The IEC 61646 certificate is also a standard requirement for most grants.
4.3.3. Certification according to IEC 61730 – Panel security
The certificate is mandatory for photovoltaic systems in Europe. It describes the safety standard for solar panels and addresses 3 areas:
Class A building
Class B utility applications
Class C low voltage applications
The certificate describes the construction requirements and the
material-specific requirements regarding:
Fire protection of the photovoltaic modules
as well as the standards for the test procedures.
The aim of the IEC certification is: mechanically and electrically safe operation over the expected service life