Solar power in the motorhome

- Function
- Concept
- Installation

Basic ideas about solar power:

Due to the growing number of electricity consumers in the motorhome, almost everyone does Thoughts on how he can secure the energy supply for his needs.

The energy supplier should cover daily electricity needs, be environmentally friendly and available at all times. Of course, the amount for the necessary investments also plays a role that should not be underestimated.
If you only look at the money, electricity from the socket is the cheapest alternative, even if you often have to pay very high fees for it on campsites or parking spaces. .

An essential point for the use of solar power is the availability. Whenever daylight falls on the solar cells, a current is generated that can recharge the on-board batteries.
All of them without doing anything, without noise or exhaust emissions for the environment and without having to do anything about it yourself.
Depending on the design of the solar system, the electricity consumed is only supplemented so that the possible service life is extended or the electricity consumed is cpl. Replaces.

Summary:
Apart from occasional cleaning, solar modules are maintenance-free.
Solar power is free of charge and is generated without generating any noise

The solar system in a motorhome works in a similar way to a charger, only without a power connection. Basically, a solar system consists of one or more solar modules on the vehicle roof and a controller that is located in the vehicle interior. When light falls, the solar modules emit electrical power, which is fed to the batteries via the control system. The on-board batteries take up the current until the control system detects that the batteries are fully charged.
The solar system works like a second charger that is simply connected to the on-board battery via the solar controller. As before, charging can be carried out while driving via the alternator and via the on-board charger via 230V. These chargers work independently of each other without influencing each other.

Performance data / efficiency

The maximum output of a solar module is specified in Wp. This performance is determined according to international standard conditions. This is based on a certain amount of solar radiation combined with a fixed temperature.
This specification must not be confused with the specification Wh / d. This information is not subject to any international standard and therefore does not offer the possibility of comparing different solar modules.
Since the maximum possible output of solar modules is specified in Wp, a module with a higher degree of efficiency does not supply more power than another module with the same output and a poorer degree of efficiency. For example, 85WP always remains 85Wp. A module with better efficiency is then only smaller.

Solar battery / storage capacity

It is often wrongly claimed that a solar system only works with a solar battery. This is wrong.
A starter battery is also charged by the solar system.
It is true, however, that a starter battery cannot cope with the corresponding loads caused by cyclical operation in the long term.
So when choosing a battery you should make sure that you buy a battery that is described as deep cycle. It does not matter whether you use an acid, gel or AGM battery.

The nominal capacity of the battery must never be completely removed, as this leads to a harmful deep discharge and the battery is destroyed or irreparably severely damaged in the process.
A remaining capacity of around 30% should always remain in the batteries. The deeper the batteries are discharged, the greater their wear and tear. It follows that those who use the battery the least can expect the longest service life. To save the existing battery, you can install an additional battery. Then the battery, assuming the same power consumption, is only used with 50% of the power.
In order to increase the service life of the battery, it is important to recharge the current as quickly as possible. This can be achieved with an appropriately designed solar system.

How big should the solar system be dimensioned?

To determine the required solar power, you have to think about some important things.
How many and which electrical consumers do you want to operate
How long should these consumers be operated
Do I just want to extend my possible service life or do I want to fully reduce the electricity consumed. Replace
at which time of year and in which region I am traveling

my own energy requirements.

In order to get an overview of the amount of energy required per day, you have to make a list of the consumers and note the operating time in hours and the power consumption in watts of the consumers.
Here are some typical consumers:
Transistor lamp (fluorescent tube) 12 W = 1A
12V television set 36 W = 3A
12V satellite receiver 24 W = 2A
Halogen spotlights 10W = 0.8A
Circulating air fan of the heating 12 W = 1A

With these values ​​you can estimate your daily electrical energy requirement.
e.g. B. the transistor light is switched on for 3 hours a day. Results in a daily requirement of 3AH

Now that it is known how much energy is required on average each day, one can proceed to the selection of the solar modules. Since only the theoretically possible maximum power is given for solar modules, it is unfortunately not possible to use this value to determine the size of the solar system. Too many factors reduce the energy yield. Of particular note here are: the duration of sunshine, the angle of incidence of the sun on the modules, the temperature and much more.
But in order to have an almost realistic calculation basis, there are tables in which the average power output of solar cells can be determined.
Here, for the following modules, the values ​​given are approximately that can be expected (from spring to autumn):
55 watt module (55WP) approximately 15AH / day
85 watt -Module (85Wp) in about 22 AH / day
120 watt module (120 Wp) in about 30 AH / day

Which solar system should I take?

If you are now has done the work and has its energy balance, you still have to think about how long you want to stand without a power connection. Certainly it would be optimal if the solar system fully consumed the electricity. Can complement.
However, this is not necessary for many motorhome owners. In this case, a supplement to the battery charge is sufficient to achieve the desired independence from the external power supply.
Here is an example:
The amount of electricity per day determined in the calculation is 30AH, which is a realistic amount under normal conditions from spring to autumn. The existing battery capacity is 200AH, of which the battery still has 180AH available due to aging and wear. In order not to damage the battery by discharging it too deeply, an amount of energy of 90AH can be drawn. This means that the service life without a solar system is around 3 days. In connection with a 55W module, the possible downtime is 6 days, with an 85W module a good 10 days and with a 120W module the amount of electricity drawn would be complete. Balanced.
As you can see from the example calculation, it is not necessary to install an extra large and therefore very expensive solar system. If you don´t want to stay in one place for several weeks, even relatively small systems are sufficient to have sufficient power during the idle time.

If you are still unsure about your power consumption or simply want to have the option of expansion for the future, choose the cabling and the controller so large that the possibility there is a further solar module to be connected and thus to double the charging current. Even relatively small systems are sufficient to have sufficient power during the idle time.

If you are still unsure about your power consumption or you simply want to have the option of expansion for the future, you should choose the cabling and the controller so large that the possibility there is an additional solar module to be connected and thus to double the charging current. Even relatively small systems are sufficient to have sufficient power during the idle time.

If you are still unsure about your power consumption or you simply want to have the option of expansion for the future, you should choose the cabling and the controller so large that the possibility there is an additional solar module to be connected and thus to double the charging current.


oceanline, 2009-03-22