As with the rest of this site, information is only intended to be guide, in easy to understand terms, and to give an understanding why there may be regulations which need to be followed for safety reasons. This article does not attempt to include all possible risks or dangers.
Danger of Electric Shock
Some people may have the misconception that as the solar power they are using comes from a battery, then that electricity is somehow safer. However if you have an inverter which producing mains voltage, this should be treated with the same care and respect as normal mains electricity. Any installation should have normal electrical protection equipment in the high voltage circuit. Any portable systems should be treated with care.
As for the solar panels/modules, these are generally, but not always, at a lower voltage and therefore safer. However, many will be surprised to know that the lowest voltage believed to have caused a person's death, is around 60 volts. Also, the direct current (DC) produced by solar modules is more dangerous to humans, volt for volt, than an alternating current (AC) due to the ways it affects the muscles of the body.
While many modules in current use may not produce more than 30 volts, they may be used in systems where they are connected in series to produce much higher, and therefore dangerous, voltages.
This has been a concern for fire fighters who may have to be on a roof around a solar power installation in an emergency situation, as although there may be a cut-off switch to disconnect the modules from the rest of the system, the modules themselves and their associated wiring could have dangerously high voltages.
Danger of Fire
Evidence of solar power installations being the cause of a fire are limited, but as with any electrical installation, the risk exists, particularly if a fault occurs. This risk will be higher if incorrect equipment or wiring has been used. A factor to be considdered is the low voltage DC wiring connect to the modules, which may be carrying a high current. The high current, particularly when it is a direct current, can cause high temperatures or arcs if there is a bad (high resistance) connection, or in an isolating switch. An isolating switch designed for an AC current is not suitable for a DC current.
Danger with Batteries
Batteries pose a particular danger as they store a large amount of energy, and if that energy is is dissipated (used or released) in a short period of time, for whatever reason, the consequences can be substantial. The energy contained in a battery for an off grid domestic system is likely to be 20-50 Kw hours. To put this in automotive terms, this would power a Formula 1 racing car for around 3 minutes, or in aeronautical terms, a Jumbo Jet on full power for around half a second. This hopefully illustrates the potentially explosive effect that could occur if this amount of energy were to be released in a very short period of time due to a short circuit.
If this energy is released over a period of minutes rather than seconds, a large amount of heat can be generated, possibly resulting in fire. In the case of a lead acid battery, acid could be released. There is also the potential for a large amount of arcing.
A very important factor to considder is that lead acid batteries give off hydrogen while being charged (and for some time afterwords). Hydrogen is combustible, and when mixed with air, explosive. Any spark due to a short circuit or from connecting/disconnecting a battery while charging or soon after, can cause an explosion resulting battery damage and acid spillage.
There have been cases recorded where people have been seriously injured in this sort of situation with a vehicle battery, which may only store 1/100th of the energy of a solar power battery.
Danger from Toxic Chemicals
Although toxic chemicals are used in the manufacture of solar panels and batteries, there is no evidence to suggest that there is any possibility of these being in danger of being released into the evironment or as being a danger to people in normal situations. However there is some concern that if the installation is involved in a fire, toxic chemicals may be released and be of particular concern to fire fighters.
As a seperate subject, some of the manufacturing processes have been a concern to environmentalists due to the chemicals involved.
Someone once calculated that with knowledge of current known risks, more people where likely to die as a result of falling off a roof whilst installing a solar power system, then were likely to die due to radiation from atomic power - but who knows.