HPS lighting or High pressure sodium lamps is a High intensity discharge (HID) form of lighting that is commonly used as indoor grow lights for hydroponic production of plants, flowers and vegetables.
The HPS light operates when an electrical current is run through an arc tube that has been filled with a gas. In this case the gasses found within a HPS globe is a mixture of sodium and an inert gas Xenon. The Xenon is used as a starting gas in the high pressure sodium lamp. The current and temperature increases in the arc tube until it reaches a high pressure operating state.
High pressure sodium or HPS lamps have a higher efficiency than the older style of metal halide or mercury vapour lamp, reaching around 150 lumens per watt or 90,000 lumens for a 600w HPS lamp and around 55,000 lumens for a 400w HPS lamp.
HPS lamps have a spectral range from 570nm up to 750nm which are the yellow, orange and reds. With some versions of the HPS lamps they have been tuned more for horticulture and have spikes in the blue at around the 450nm to 500nm range this makes them a fantastic choice all around for horticultural lamps to be used as indoor grow lights and hydroponic lighting. These grow lights have had their spectrum optimized to provide the exact spectrum for use as an indoor grow light.
Lamps such as the GE Lucagrow, Phillip SonTagro, Gavita Enhanced and Osram plantastar ae all examples of these style of full spectrum HPS lamp.
All lamps have a limited life span, as the sodium is highly reactive this leads to a slow loss of gas over time and this eventually will lead to the lamp cycling.
As a result the lamps will start to overheat during operation which increases the pressure in the arc tube and more than normal voltage is required to maintain the discharge from the arc tube. The expected life span of a HPS is around 20,000 hours but it is recommended that the lamps be changed after around 3000-5000 hours, as they will have lost significant lumen output.
In conclusion HPS grow lights have an ideal spectrum for flowering plants. HPS growlights are cheap to purchase compared to LED grow lights and they are a lot more efficient than older style metal halide grow lights. HPS grow lights are the indoor grow light of choice for most hydroponic grow light kits that are purchased today.
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