Q1: Why should I use electronic ballasts?
A1: Firstly Electronic ballasts are more efficient and completely silent with built-in circuitry protection, so they are very safe to use. What's more, electronic ballasts can work with varying supply voltages by adjusting itself to an optimal output, while magnetic ballasts by having a reduced output when the input voltage is lower than specified. An electronic ballasts will adjust the output to the lamp during its lifetime. It has a soft start which puts less stress on a lamp when starting it up.
Q2: Why should I replace my reflector periodically?
A2: Reflectors get dirty and unfortunately cleaning them does more harm than good to a aluminum reflector. Dust, dirt and deposits depreciate the reflector efficiency by as much 5% per year. So why would you only change a lamp when 2/3 of the light that comes from your fixture is reflected light? Replacing your reflector is the cheapest way to get more light on your crop. If you want to clean it then do it very carefully with only a soft cloth. Never use detergents, some vinegar might work for calcium spots, but rinse with distilled water after that to prevent spots. Never polish a reflector, you will scratch the surface. Built in any case: a cleaned reflector will never be as efficient as a new one.
Q3:What is Photosynthetically Active Radiation (PAR)?
A3: PAR is an often used (and often misused) term. It is NOT a measurement or "metric" like feet, inches, or kilos. Rather, it defines the type of light (scientists call light "electromagnetic radiation") needed to support photosynthesis in plant life. Through photosynthesis, plants convert light energy into chemical energy, which is the food they use to grow and thrive.
Q4: What is Photosynthetic Photon Flux(PPF)
A4: The first measurement is Photosynthetic Photon Flux or "PPF" which measures the total amount of light that is produced by a light source each second. Put another way, PPF tells us how much PAR is emitted by a light source per second. More technically, PPF measures the "photosynthetically active photons emitted by a lighting system per second". This measurement is expressed in "micromoles per second" and we'll get to micromoles in a minute. Note though, that PPF does not tell us how much of the measured light actually lands on the plants or any other surface. It is probably the second most important way of measuring a lighting system, but, for whatever reason, 99.9% of lighting companies don't list it. PPF is expressed by scientists and light engineers as: μmol/second.
Q5: What is Photosynthetic Photon Flux Density (PPFD)
A5: The second measurement is PPFD which measures the light that actually arrives at the plant or algae. Photosynthetic Photon Flux Density or "PPFD" is a measurement of the amount of light that actually reaches your plants and algae or, as a scientist might say: "the number of photosynthetically active photons that fall on a given surface each second". PPFD is a 'spot' measurement of a specific location on your plant canopy, and it is measured in micromoles per square meter per second. This measurement is expressed by scientists and light engineers as: μmol/m2/s.Daily Light Integral (DLI)
Q6: What is Daily Light Integral (DLI)
A6: The third measurement is DLI (Day Light Integral) which measures the total amount of light that is delivered to a plant every day. The grower can think of DLI as the plant's daily "dose" of light, though a scientist would probably say DLI is a cumulative measurement of the total number of photons that reach the plants and algae during the daily photoperiod. DLI measures the number of "moles" of photons per square meter per day and is expressed as mol/m2/d.
Obviously, if you leave your lights on longer, your plants absorb more light. Or, put in more technical language, a lighting system with a lower PPF can deliver the same DLI to an aquarium compared to a lighting system with a higher PPF if the photoperiod is extended. DLI is analogous to the total amount of rain that falls during a storm, as opposed to how fast the rain fell (which would be PPFD). DLI is the most important metric for determining the overall growth rate of plants and algae. Once you know the preferred DLI of your plants and/or algae, you can easily set up a lighting system to deliver the required amount of light. Properly designed photosynthetic lighting systems start with defining the required DLI.
Q7: What is Moles?
A7: There are huge numbers of photons or "light particles" in visible light --- in fact, the quantity is so large that we cannot easily express it using normal numbers, so we use two measurements commonly used by scientists when measuring huge quantities. The first number, which is called a Mole, is equal to something called "Avogadro's number", which is 602,214,150,000,000,000,000,000! For a more manageable number, a micromole is a millionth of a mole. Much better, right?! In plain English, a micromole of photons (which would be one millionth of Avogadro's number) is 602 quadrillion. Since these numbers are so large, it is easier to reference quantities of light in moles and micromoles.