Solar Powered Street Lights are a growing use of solar energy and really show how what is otherwise an expensive alternative to traditional electrical supplies can often work out cheaper and more reliable.
Fundamentally, a solar street light can be considered a light on a stick, admittedly a big stick! The normal make up is the standard street light type pole with a solar PV (PhotoVoltaic) panel on the top which collects energy during the day and charges a battery, also often on top of the pole (to stop it being stolen), the battery then feeds the street light during the night! The light is switched on either based on a timer or a light sensor which detects when light levels fall.
In the UK, an increasing number of these units have a wind turbine, this is mostly seen in the UK and Europe where the longer winter nights usually coincide with lots more wind, the amount of daylight not necessarily being enough to charge the battery.
In the UK these solar street lights are increasingly being used to improve security in identified risk areas. This could be a pathway through a park, ally ways, generally locations where laying new mains cable is inconvenient due to the distance from the nearest power point or the disruption in digging up a road or pavement to run cable.
In the UK additional options can include PIRs which detect when somebody is nearby. These are ideal fora number of reasons, in particular extending the length of available battery time which of course is a challenge during the longer darker evenings which in turn mean less daylight for charging. The other big advantage is preserving the night sky! The public can walk through an otherwise dark area, as they walk, the lights come on and provide a level of security and illumination. Reducing the on time also preserves the equipment, particularly the battery!
Use in the Developing World
Solar Street Lights have taken off in the developing world in a big way! The main use being as direct replacements or alternatives to mains powered – on grid – street lights! There are distinct advantages similar to those advantages seen in the west, in particular the removal of any need to lay mains cable!
This advantage is more pronounced in the developing world in that mains electric power is often some considerable distance from the areas where lights are required.
More important though is reliability. Solar Powered Street Lights are not subject to power cuts, either unexpected or due to load shedding! The local power grid might go down but the street lights keep working. This can be vital where the area is not so secure and a street light can be the difference between a crime hotspot and safety!
In the developing world we are of course invariably nearer the equator, the daylight is more consistent, light levels are higher and the solar panels come into their own! Also there is not such a requirement to have them angled towards the south, many are simply laid flat, in particular in countries such as Nigeria which are on the equator! see: solar street light nigeria
Solar Powered Traffic Lights
These have come into their own in South Africa and are increasingly used, often replacing existing mains powered traffic lights! The big advantage being the fact that:
- they are not subject to the load shedding that is endemic in South Africa due to the growing economy outstripping the power generation
- stopped traffic is a target for car jacking!
South Africa has a real security problem, when traffic comes to a stop, the drivers are at real risk of assault and theft, a moving car is far safer, hence working traffic lights are far more than the convenience that they represent in the UK!
see: bbc news – SA traffic light tamperer stopped
Power on a stick
The there are an increasing number of companies offerring solar powered street lights, the technology and integration between Solar PV panels, Charge Controller, Batteries and light – both the local levels of sunlight and the street light to be powered is complex and often can result in a failed system. A well defined and engineered system can be simply assembled, stuck in the ground and apart from a routine check can be left to look after itself!