As street lighting accounts for 10% to 38 % of a city’s electricity consumption and energy costs keep rising at staggering rates, it must be a first priority for any council or private organisation to lower energy costs for street lighting.
The development of highpower white LED light sources has brought about a revolution in street lighting and greatly facilitated the task of reducing electricity bills and maintenance costs.
Beside the benefit of increased luminous efficacy and superb colour rendition of white LED light, carbon emissions are reduced as a result of lower energy consumption and dimming regimes.
The progress in LED light sources has also helped to improve the performance and image of solar street lighting and the sector will become even more competitive when pv modules with higher conversion efficiency become commercially available. These new modules will reduce surface area, wind resistance and weight. High power street lanterns will then enter the realm of solar street lighting, too.
As stand-alone solar street lights are autonomous and produce clean energy from a photovoltaic module on site, they are best-suited to contribute to a low carbon economy. Each installed unit will reduce carbon emissions during life span depending on the output and energy mix found in a comparable grid-connected street light.
Some local councils may still be sceptical of introducing solar street lighting, based on the assumption that they may not be cost-effective, or provide reliable lighting throughout the night. There are also concerns that the lights are easily vandalised and stolen, need to batteries replacing and cannot be used in high power applications. However, if one takes the latest developments into account, most of these assumptions can be disproven.
For instance, Solar LED street lights from SolarTech with a 8 to 26 watt LED array may be installed at the same or lower cost than grid-connected street lights for a scheme quantity of 100 units. Grid connection, excavation and cabling may substantially add to the installed cost of traditional street lighting so that savings may be achieved immediately. While the replacement of worn-out batteries should occur every seven years at about 10% of the total solar equipment cost.
Solar LED street lights may be made available as retrofit kits with light-weight aluminium supports or enclosures and fitted to an existing column if structurally fit and can include Smart Energy Management (SEM) to reliably provide lighting throughout the night in all seasons.
SEM reduces the current to the LED driver via an algorithm, in case battery voltage reaches an adjustable preset value. Reduction in brightness is hardly visible when this process starts. In such a way continous lighting of 16 hours can be achieved daily.
The remote controlled dimming of grid-connected LED street lights by various councils is a comparable procedure. SolarTech street lights are photometrically tested and have a high S/P ratio of 2.36. This means that the human eye senses a brightness which is, by this factor, larger than the lumen output suggests. SolarTech street lights are suitable to be installed in streets with a width of 3 to 12 metres and comply to Lighting Standards S3 to S6 when adequately spaced. It is estimated that for a scheme of 100 units, the total savings for supply and electricity will amount to £100,000 or more.
A renewable finance package is available through SolarTech where convenient repayments are made via realised savings.
The benefits of Smart SolarTech Street Lights can be be summarised as follows: No grid connection charge, no waiting time for grid connection and immediate operation, no cable trench excavations, no cable cost, no metering, zero electricity cost and zero carbon emissions for life span, will work during power cuts or emergencies, programmability of lighting and theft-protected components.
David Lindenberg works for SolarTech www.solartechuk.co.uk
