The future of light: HPS vs LED

HPS is the well-known and traditional fixture for growing all plants, so why should you take the “risk” of choosing LED for your greenhouse - and is it more beneficial to grow plants under LED light? Explore why controllable LED fixtures are a bright choice, and why more and more growers consider this a better solution than HPS.

Let's start with the plant's requirements
Dotted lines on the graphs indicate the active area of the photosynthesis. Note the difference between the spectra (colours) of HPS and LED respectively. It is vital to know that especially red, somewhat blue and only quite a little green / yellow is essential for the plant’s growth. Also note the beam heat: It is a very expensive way of heating.

HPS or LED?
Below you will find statements of both HPS and LED - and each statement must be considered to be opposed to each other - meaning HPS versus LED. This will give you an insight in the difference between the two kinds of fixtures.

HPS

  1. Significant beam heats from fixture in the top of the greenhouse = Price-raising heating.
  2. Frequent ventilation required due to beam heat coming from the HPS.
  3. One spectrum (colour) to fit all plants' needs.
  4. No possibility of changing the spectrum and thus the amount of the blue light.
  5. Traditional light strategy = Limited opportunity for production optimization.
  6. On/off use.
  7. Low efficient μmol/w/s.
  8. Decline in the bulb’s light output - at the same cost of energy consumption.
  9. Shorter lasting bulbs, approx. 10,000 h.
  10. Needs maintenance for stable output.

LED

  1. A minimum of heat dissipation ensures better heat control = Financial savings.
  2. Optimum utilization of insulation screens and CO2.-supply.
  3. Control of spectrum (colour) and light intensity needed for different stages of all plants.
  4. Less Plant Grow Regulation treatment by using blue light (results in a more compact crop).
  5. Optimized production time.
  6. Dynamic light control = energy savings.
  7. Highly efficient μmol/w/s.
  8. Steady light output of the diode with unchanged power consumption.
  9. Long lasting diodes, approx. 70,000 h.
  10. Hardly any maintenance.

Heat circulation, and why it is evident that the use of HPS will result in significant heat loss
The beam heat from HPS will raise the temperature in the top of the greenhouse. This heat will circulate to the temperature sensor, which will close/reduce the bottom heat. This results in “cold roots”, which affects the crop’s growth. To avoid this situation, the windows open, temperature is dropping and allowing the temperature sensor the opportunity to open the bottom heat. As a result, the open windows will cause loss of heat and CO2.

At a working temperature at only 45°C for the Senmatic LEDs, the climate condition for the crop is significantly more comfortable. Bottom heat can be active under all conditions, to secure active roots and resulting in optimum growth conditions. The significant lower working temperature of the LED fixtures allows less ventilation and protect heat and CO2 loss, too.

Savings by using LED
When considering an investment in LED fixtures, you usually only calculate on the exact cost - how much does a fixture cost, and what is the Return On Investment? But there are many more savings and advantages to consider than simply the cost of purchasing and installing a LED fixture. Are you aware of those? 

Direct financial savings

  • Electricity consumption
  • Light intensity and spectral composition are optimized in relation to the plant’s needs (thinking like a plant)
  • Consistent light output year after year

Secondary savings

  • Better control of heating in greenhouses consisting of:
    • Better heat control (ratio of top and bottom heat)
    • Less overproduction of heat, so screens can be used as insulation screens
    • Closed windows secure a controlled CO2 level 
  • Less use of chemicals for healthier plants (and protection of the environment)
  • Optimized production time (considerable yield)
  • Greater uniformity of the crops results in higher efficiency and less labour.
For more information:
Senmatic

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