Build a solar system for the camp
Through our work with the solarsystem of OrangeCamp, we had some experience with solar panels. We would like to share that experience with all of you. Our motivation is basically, to get a cleaner festival and nature, and furthermore it will save you many trips to the shop to buy batteries, or to carry car batteries for recharge
If you consider how many boomboxes and various types of lamps that are at the festival site, even just in the camps around your own, try to consider how many batteries being used during the festival. Many of those do not even end up in the trash can and very few are collected and send for properly environmentally sound destruction. That is what we, together with the sun, will try to change.
For this description is the starting point is a general Roskilde camp that need power for music and some light in the camp. We have chosen a relatively small system. This makes it possible for everyone price-wise, but the philosophy is the same if you want to build bigger.
We'll go through what it takes, how it is built and not least, where you can buy the parts cheap. We will guide you completely from scratch, and all can participate. Something might be common knowledge for some, if so you can skip parts of the description.
What are we building?
We are building a small 12-volt direct current (DC) system charged by the sun. A 12V DC system is also used in a car. Because of this it is possible to buy lots of accessories that can be connected. Lights, music, cell phone charger ect
What is necessary?
We need a few components:
- A car battery
- A solar panel
- A charge controller
- Cables and connectors to connect the parts
Description of components
This section is a bit technical. Does this sound too technical, do not give up. You do not need to understand it all to build your system. Further down the page usable components will be listed
The car battery is the heart of the system. It stores the current to be used later. A car battery is available in many sizes, but is typically around 40-60Ah. Ah mean amperes (A) hours (h). If you use a 40Ah battery you can, in theory, use 1A for 40 hours or 40A for 1 hour and everything in between. The important thing in this is that the higher the number, the more power the battery can store. The number is printed at all new batteries.
If you are willing to spend a little more money on your system you should buy a battery of the type known as a deep cycle battery. These are slightly more expensive but they are more suited for the needs you will have in a system like this. They are made to provide a lower power during a longer period of time and is better suited to be discharged and then recharged again. They have a longer life span and can be used for many years.
The solar panel convert the sun rays into electricity. For this system we will use a small solar panel rated 30-50Watt. In this case watt indicates how much power the panel is able to produce on a nice sunny day. The higher the number, the more power.
The most important here is that the panel is designed to charge a 12V system. To charge a 12V system, you need a panel with an output of 16-20V. This can be read on the panel and at the specs where you buy it.
The charge controller controls the charge cycle from the solar panels to the battery. Most controllers ensure the battery not being overcharged and some also makes sure that your battery is not discharged too much. Both will damage the battery. Here it is important that you ensure that your controller is rated for the power produced by the solar panel. If the label at the solar panels states that it produces 2 Amperes, the controller need to be able to handle at least 2A. This is stated on the controller or in the manual. Most controllers can handle systems of this size.
The wires must be of good quality. In larger systems, the wires needs to be very thick. On systems of this size only a good quality wire is needed. You should be aware that the longer the wire is, the thicker it must be. Therefore it is wise to keep them as short as possible.
How do I get components cheaply?
Car battery. In Denmark there is a high tax on batteries, so they are quite expensive. You should be able to find one around €50.
Solar panel. The price varies a lot between the countries(easily 100% more expensive in some countries) depending on the political focus on solar power. With internet shopping thats not the big problem anymore. You should however be aware of one thing: the customs rules. It is depressing to have found a cheap panel in Asia or USA and when you receive it, it comes with a tax bill. However within the EU there is no problem. We would recommend Germany as they are cheap, and then freight costs relatively low for most of EU. If you enter www.ebay.de and search "photovoltaik 30w" (or press here) you should be able to find a panel around €40-€60.
Charge Controller. The same as solar panels applies here regarding purchase. At www.ebay.de you can search "phocos cml" (or press here). This is a good quality controller, which is available about €25. This controller protects the battery against both overcharge and too much discharge.
The wires are available in any DIY shops, electricians etc
If you follow these instructions, you should be able to buy all the necessary parts around €140.
How do I connect the components?
When working with DC, there is one important rule: positive to positive and negative to negative. This means that the wire that comes from solar panels, which is positive(+) to be connected to charge controller which is positive(+) and similarly where it is negative (-). These things are easier to see in the scematic below.
How should solar panels be located?
This depends on the path of the sun and therefore it varies depending on the season. Since we will use our at Roskilde Festival, it is optimal that the panel faces south and has an angle of approx. 30 degrees
How much power does the system provide?
The most important thing is of course the weather is sunny, otherwise the output logically is very limited. If the weather is sunny the battery is charged and you can continuously use the power. If the battery becomes completely empty, the charging time will be quite long, but the point of the system is of course to maintain battery power.
What can be connected to the system?
Everything is designed for 12V. Music and light is probably the most important thing at Roskilde Festival. When choosing a boombox/radio, it is important that you ensure that it can be driven by 12V. Some have connectors for 12V then it's very easy. Otherwise you can try to find one that is build to use 8 normal batteries. These are each 1.5 V and 8 of them provide 12V. Then you simply connect the positive(+) wire, where the positive(+) end of the batteries should have been, and negative(-) wire where negative(-) end of the batteries should have been. A car radio can also be used as it is designed for a 12V system. When you choose your light, it should also be made for 12V, but here is a lot of this. Everything is made for campers etc, made to put the cigarette lighter socket in a car can be used. Go for the LED light, since it uses a very small amount of power.
The things to be aware of with such a system are:
The battery contains acid. It should not be punctured, tipped over ect. And generally handled with caution.
Possitive(+) connected to possitive(+)and negative(-) connected to the negative(-)!
Battery and charge controller must be kept dry
Q. Is the current dangerous?
A: No, you cannot get electric shock from 12v, not even by direct contact.