Models for choice in street lighting :

① power o bulb: low pressure sodium bulb 55W

②Wrangler Limited electronic ballast for direct current low pressure sodium ballast: Wrangler Limited electronic low pressure sodium ballast for 24V direct current lamp--adopts the CPU, and top quality electronic components from world famous manufacturers in its products. Distinctive features is as follows: the internationally original created controlling system matches the parameter of bulb accurately; multi-protectional function; high frequency ignition and operation, which makes the life of bulb extended by 2.5 times; lighting efficiency of bulb is improved by about 10%; advanced and rational design of the circuit, high quality component as its parts, and strictly quality testing and production management, all of which insures the top quality of Wrangler Limited products. Operated in ambient temperature of -30℃---50℃,the life is as much as 20,000 hours .

③Matching of light source In operation, the surface temperature of low pressure sodium lamp is as low as ≤70℃. So that, there is no high temperature oxidation, which causes the decline of reflecting effect on the lamp reflector. The reflector of the lamp is made from aluminium material whose mirror plate is high in reflecting index; moreover, the alumnium material is processed by oxidation craft. Thus the reflecting efficiency is as optimum as ≤85%.

Contrast of Advantages and disadvantages between low pressure sodium lamp and high pressure sodium lamp in application:

① Color: The light from high pressure sodium lamp comes from the discharge of a mixed halogen vapour. The color temperature is 2300K, and color rendition index is 40-60Ra. The light from low pressure sodium lamp comes from the discharge of low pressure sodium vapour. It is monochromic in nature. As the monochromic illuminant ，it irradiates sodium wave of 589.6 in wavelength. The color of the light is yellow. The color temperature is equal to 1700K or so from the multi-color light. The color rendition index is ≤20Ra In practical application, the color rendition of high pressure sodium lamp is better than low pressure sodium lamp, and the visual effect is prior to low pressure sodium lamp. In rainy and foggy days, the yellow light from low pressure sodium lamp possesses higher penetration power than high pressure sodium lamp.

② efficiency: appended diagram -- efficiency of low pressure sodium lamp and high pressure sodium lamp. efficiency diagram of high pressure sodium lamp

The diagram shows that low pressure sodium lamp is better in efficiency than high pressure sodium lamp, and the energy saving effect is much higher than high pressure sodium lamp too. It deserves the most efficient (lumen/watts) light source of the world, and is the optimum light source for solar street lighting system.

③Matching of the lighting fixtures The lighting area on the low pressure sodium bulb is large, and low in temperature. It is small in the high temperature oxidation effect to lamp. Aluminiunm of high reflecting index is available. The reflecting efficiency of the lamp is improved by 85%. Large in luminant area, and the controlling of glaring phenomenon is prior to that of high pressure sodium lamp. To summer up, in solar street lighting and energy saving lighting system, low pressure sodium lamp is the optimum products among all light source.