SPIRIT solar lighting enables you in enlighten your urban or rural environment in a sustainable way; off-grid based on solar energy technology. Selecting the best solution for your environment is not easy. The market is emerging and the number of alternatives is equally increasing. We’d like to help you out in focussing on the right questions during the selection process, by providing this mini masterclass. The masterclass has three focusses on the next pages: location and configuration, light effects and total cost of ownership (TCO).

Location predetermines a lot: actually the whole configuration. We try give a hint on two items and explain why we think these are important:

1. A park or a high way require different lighting approaches. A highway with intense traffic has to be lighted very efficient with a great uniformity - parks are more often ambiant illuminated with sophisticated sleek designs - masts or even bollards. Rule of thumb: >6 meters height is for street lighting. Lighting in residential areas may start at >5 meters. The higher the luminaire on the mast, the better the uniformity. Though if the mast is higher, the scattering of the light is more fragmentated/less focussed.
   Obviously, intersections should require more attention and specifically illuminated with more care.
   
   
2. ‘What’s the location?’, is one of the first questions which always pop into our minds. For us - location equals sun irradiation. The closer the location is to the equator, the higher the sun irradiation. Not only the solar energy generation is higher, also the length of days/nights are more or less equal in summer and winter. The energy requirement determines in the end the amount of solar panels needed, and in our case therefore the height. For example: 7000 lumen (or 50W) is to be achieved with a 8 meter high mast.
    

Our advice: rather focus on light effect on your environment than the amount of ‘watts’. The ‘watt’-input of the luminaire actually only informs about the amount of energy needed to activate the luminaire, not about the effect on the road, your final objective. Two effects that in our opinion are worth to take note of:

1. The power of solar energy systems is traditionally lower than for conventional systems. Besides the conversion losses to DC (LED is DC), the conventional systems do not have the urge to be as efficient as possible. With the public lighting on solar energy, all energy to be used also has to be regenerated. So we trust to state, that all solar street light provider value energy more than the conventional public lighting industry. And do their utmost to provide a luminaire as efficient as possible, with the best result on the surface. Therefore focus on the ‘cd/m?’ instead of the ‘watt’.
   
2. Make a light design with a photometric calculation. In that way, you can calculate the effect on the surface and also the needed intermediate distance of the masts for certain standards (M1 - M6 for motorized traffic or P1 - P6 for pedestrian areas). Keep an eye on:
    
   - Lighting level: an average of light intensity on the surface. In cd/m² for road lighting and in lux for pedestrian areas
   - Glare restriction: a value to prevent discomfort or even disability. This threshold increment should be as low as possible
   - Uniformity of illuminance: the value of how equal (or spotted) the lighting is. Fragmented light, when the eye has to adapt frequently to light-dark, is perceived as distracting.
   
   An extra note: ask for an assessment report of the luminaire to check the lumen/watt-promise that is made.  
   

1. Choose proven technologies. Disruptive innovations are often promising, but are you willing to be the first to try with your large investment? Curved or thin film solar, or an extremely efficient luminaire? We opt to test them first in the lab or as a demo in the field. And also in this case: if it seems to good to be true, it often is.
    
2. Get insight and knowledge about the different lifetime expectancies of the elements. And how to replace or maintainance. Will it be time consuming in the future? Or is the lifetime expectancy of a battery twice as long as the other? That might be a cost effective consideration.
    
3. The choice of materials and the holistic design. The material used has a strong influence on the strength and the perceived quality. We prefer steel over aluminium, and powder coating over regular paint. Also, check the design measures for the conditions in your environment. Some examples:
   
   - design for higher wind speeds in construction and mounting on foundaton
   - sea air and oxidation of metal elements
   - heat and the effect on the lifetime of the battery (e.g. It is not unusual for the lifetime of a battery to be limited to 50% when it is used in an environment of 30°C) 
   - the effect of the depth of decharge and the lifetime of the battery
   - the influence of dust (in case of electric components/sensors), etc.
   
   

We have over 40 years of experience in the public lighting business. Please, do not hesitate to contact us to come to the best lighting design for your situation together.