Tom's Alternative Energy Micro-systems website
While not inherently dangerous to the human body in the same way that household current is, 12 Volts DC can be very dangerous in indirect ways and should always be treated with respect, especially in situations where a large amount of current is available. Low voltage at a high current is capable of welding or vaporizing metal and can do a number on even heavy-duty wire in the event of a short circuit. Here are some guidelines for using the power from a 12-Volt battery or alternative energy system safely.
- FUSE THE CIRCUITS. Perhaps the most important thing you can do to insure safety in your low-voltage system is to install plenty of fuses. These should be appropriately sized to the gauge of wire being used and/or the anticipated current draw. Make sure you install your primary fuse right close to the storage battery. I use a number of fuse sizes in my system. Attached to each of my two paralleled storage batteries is a 20A fuse. These protect my 12ga. wiring. The 16ga. cables are additionally fused at 10A and the 18ga. wiring for the "emergency" lighting circuit, which runs low-current LED lamps, has a 5A fuse. In addition, certain cables that I plug into the system on a regular basis have their own in-line fuse or fusible link, which can be as low as 2A if the wire is thin or current draw especially low.
- USE APPROPRIATE WIRE. Always size the wire for the electrical load it will carry. The larger the wire (lower the AWG number), the more current can be handled and the less the voltage will drop over its length. For 12 Volt applications, it should be okay to use high-quality landscape wire or automotive-type wire, provided it is thick enough to handle the current. However, under no circumstances should this type of wire be used to distribute the AC output of a DC-AC inverter. For that application, use only approved extension cord wire or that used in house wiring (such as Type NM or UF). This type of wire is also suitable for low voltage applications.
- COLOR CODE YOUR WIRING. In DC applications, proper polarity is generally very important. Red indicates positive and black indicates negative. If the particular wire you're using for 12V doesn't match this standard, use some paint or a marker to color the ends red or black, as appropriate. Simple household AC wiring uses black and white, the former being "hot" and the latter "neutral". When connecting a standard outlet or AC plug, the black wire goes to the narrower slot or the prong that would fit it, usually having a brass-colored screw.
- TERMINATE WIRES PROPERLY. Make sure that whatever you have connected to the ends of your 12 Volt cables doesn't create a safety hazard by exposing the contacts in such a way as they can be shorted out should a piece of metal accidentally be pushed up against them. Also, if those using the system aren't knowledgeable about polarity, some sort of fool-proof connection should be used to avoid accidental damage to devices being connected. Under no circumstances should outlets or plugs intended for household power be used on low-voltage lines! I can tell you from experience that it is a recipe for disaster.
Storage Battery Safety
The 12 Volt lead-acid storage battery must be treated with respect as it contains more than enough power to cause serious damage to anything conductive connected to its terminals. In addition, the chemical reaction occuring in its cells during the charging process produces flammable hydrogen gas.
- Care must be taken to have the battery in a well-ventilated location and not to produce flames or sparks near to it that may ignite the gas. I'd advise against putting the battery in a box or other enclosure unless there are air holes as this can cause a buildup of hydrogen gas that may ignite from the sparking of a loose electrical connection to either terminal. Never put other electrical/electronic devices in the battery enclosure.
- Don't make or break electrical connections that are carrying current or provide a load right next to or at the battery if it has been recently charging.
- Protect the terminals from accidentally shorting together should a piece of metal such as a long screwdriver fall or be pushed against them.
- Wear safety goggles when removing cell caps to check the electrolyte level. In fact, it's a good idea to wear them whenever you're working around the battery.
- Neutralize any battery acid (electrolyte) that gets on skin, clothing or other objects with a solution of baking soda (bicarbonate of soda) in water.
Wind Generator Safety
Wind generators are inherently dangerous, if only because of the unpredictable nature of the wind. Serious injury can result directly or indirectly from an unexpected gust.
- SPINNING BLADES ARE DANGEROUS. Never carry a wind turbine outdoors without holding onto or otherwise securing its blades if there are strong or gusty winds. It may not take much to start the thing turning and blow the assembly right into your face.
- KEEP ABREAST OF THE WEATHER FORECAST. Winds that are too strong for the wind turbine to handle can send blade fragments or pieces of the whole thing flying through the air with enough force to kill. Always know what the weather conditions are likely to be that day and if there is any doubt, take the turbine down.
- PROTECT AGAINST LIGHTNING. A metal pole high in the air is a magnet for electrical discharges from the sky. Be sure to make a good earth ground connection to the pole and provide fuse and spark-discharge protection on the incoming wires. My system uses a neon lamp between each wire and ground to help bypass any static electricity.
- INSPECT THE TURBINE REGULARLY. The PVC blades used on the typical micro wind turbine will become brittle with age and exposure to sunlight. In addition, bolts and other hardware may loosen from vibration or become severely oxidized from moisture. Try to anticipate problems before they cause a catastrophic failure.
Solar Panel Safety
While small solar panels do not have a high risk factor, there are some things to keep in mind.
- Anchor the panel securely if it's located in a position that is susceptible to wind gusts. This is especially important when mounted high off the ground.
- Avoid the use of ordinary, fragile window glass when building a panel.
- To reduce the chances of receiving a burn, wear gloves when handling a panel that is in the sun or on which the sun has recently been shining.
- Be aware that the current produced by even a 60W panel in strong sunlight can produce quite a spark, so avoid making or breaking electrical connections in an atmosphere that may be flammable (such as right above a lead-acid battery).
Exercise Equipment Safety
Adding electrical generation capability to a piece of exercise equipment can create some potential hazards, especially when operated by the young. Children will be attracted to these devices because of the novelty of making electricity and the fact that they observe adults using them.
- Restrict the very young from operating the devices and make older children aware of any potential mechanical dangers as well as issues regarding electrical connection to the charging system.
- Attach a note the device warning of any potential hazards or instructing about its proper use.
- Shield any moving mechanical parts that are in a position where they might entangle loose clothing or a body part.
- Anchor generators and drive parts securely so there is no chance of them flying off during use.
- Be sure that a homemade bicycle stand is build sturdily enough to avoid tipping.