The LED Solaris Lamp PAR Comparison by PFO

[Matt Rogers]

3reef witnessed an interesting demonstration by PFO lighting recently that compared the PPF PAR output of a PFO Solaris LED aquarium light fixture to a PFO 400w halide fixture using a 15k XM bulb.


The LED Solaris Lamp Demonstration by PFO
Click for large pic to read meter results.


This arrangement was to show that the Solaris LED fixture actually had a higher (PPF) PAR rating than the 400 watt halide bulb. Note: 3reef told the XM bulb used in the demonstration was less than a day old.


The Setup:

Each fixture was hung at the same height (rather high - approximately 18 inches) over the same 25" deep cube aquariums. Each aquarium had a sensor for a Apogee Quantam Meter (Model QMSS-E) at the bottom of the aquarium.


The Apogee Quantam Meter Model QMSS-E Used in this demo

Further info on PAR and the Apogee Quatam Meter:
http://www.apogee-inst.com/pdf_files...ter_Manual.pdf
Apogee Instruments: Frequently Asked Questions


Observations:

The LED Solaris fixture clearly was getting a higher number on the Quantam Meter - nearly 20% higher than the 400 watt halide fixture. 143 to 115. These numbers did not change much over the course of the day 3reef witnessed this setup.

Beyond the numbers, 3reef, having never seen a Solaris LED fixture in action, was impressed by the light spectrum of the LEDs as seen by this observer's eyes - crispy white with a blue tinge.


PAR AND PPF:

Although told that these sensors were measuring PAR (Photosynthetically Active Radiation), research indicated they were measuring PPF (Photosynthetic Photon Flux) PAR.

The April 2008 issue of FAMA magazine describes PAR:

Unlike lumens, which measure what the human eye can see, PAR is the objective measurement of the total light emitted by a lamp in the spectal region of plant response. In the hobbyist's terms, PAR measures the amount of light energy actually useable for photosynthesis. This is useful information for those desiring to propagate corals.

A breakdown of PAR AND PPF from Sun Master Grow Lamps:

PAR Watts for Plants

Watts is an objective measure of energy being used or emitted by a lamp each second. Energy itself is measured in joules, and 1 joule per second is called a watt. A 100 watt incandescent bulb uses up 100 joules of electrical energy every second. How much light energy is it generating? About 6 joules per second or 6 watts, but the efficiency of the lamp is only 6%, a rather dismal number. The rest of the energy is dissipated mainly as heat. Modern discharge lamps like high pressure sodium (HPS) and metal halide convert (typically) 30% to 40% of the electrical energy into light. They are significantly more efficient than incandescent bulbs.

Since plants use energy between 400 and 700 nanometers and light in this region is called Photosynthetically Active Radiation or PAR, we could measure the total amount of energy emitted per second in this region and call it PAR watts. This is an objective measure in contrast to lumens which is a subjective measure since it is based on the response of the subjects (humans). PAR watts directly indicates how much light energy is available for plants to use in photosynthesis.

The output of a 400 watt incandescent bulb is about 25 watts of light, a 400 watt metal halide bulb emits about 140 watts of light. If PAR is considered to correspond more or less to the visible region, then a 400 watt metal halide lamp provides about 140 watts of PAR. A 400 watt HPS lamps has less PAR, typically 120 to 128 watts, but because the light is yellow it is rated at higher lumens (for the human eye).

'Illumination' for plants is measured in PAR watts per square meter. There is no specific name for this unit but it is referred to as "irradiance" and written, for example, as 25 watts/square meter or 25 w/m2.


Photons

Another means of measuring light quantity for plant growth involves the understanding that light is always emitted or absorbed in discrete packets called "photons." These packets or photons are the minimum units of energy transactions involving light. For example, if a certain photosynthetic reaction occurs through absorption of one photon of light, then it is sensible to determine how many photons are falling on the plant each second. Also, since only photons in the PAR region of the spectrum are active in creating photosynthesis, it makes sense to limit the count to PAR photons. A lamp could be rated on how many actual tiny photons it is emitting each second. At present no lamp manufacturer does this rating.

Instead, plant biologists and researchers prefer to talk of the flux of photons falling each second on a surface. This is the basis of PPF PAR with PPF standing for Photosynthetic Photon Flux, a process which actually counts the number of photons falling per second on one square meter of surface. Since photons are very small, the count represents a great number of photons per second, but the number does provide a meaningful comparison.

Another measure appropriate for plant growth, called YPF PAR or Yield Photon Flux, takes into account not only the photons but also how effectively they are used by the plant. Since red light (or red photons) are used more effectively to induce a photosynthesis reaction, YPF PAR gives more weight to red photons based on the plant sensitivity curve.

Since photons are very small packets of energy, rather than referring to 1,000,000,000,000,000,000 photons, scientists conventionally use the figure "1.7 micromoles of photons" designated by the symbol "µmol." A µmol stands for 6 x 1017 photons; 1 mole stands for 6 x 1023 photons. Irradiance (or illumination) is therefore measured in watts per square meter or in micromoles (of photons) per square meter per second, abbreviated as µmol.m-2.s-1

The unit "einstein" is sometimes used to refer to one mole per square meter per second. It means that each second a 1 square meter of surface has 6 x 1023 photons falling on it. Irradiance levels for plant growth can therefore be measured in micro-einsteins or in PAR watts/sq. meter.

These three measures of photosynthetically active radiation, PAR watts per square meter, PPF PAR and YPF PAR are all legitimate, although different, ways of measuring the light output of lamps for plant growth. They do not involve the human eye response curve which is irrelevant for plants. Since plant response does "spill out" beyond the 400 nanometer and 700 nanometer boundaries, some researchers refer to the 350 – 750 nanometer region as the PAR region. Using this expanded region will lead to mildly inflated PAR ratings compared to the more conservative approach in this discussion. However, the difference is small.

PFO on it's LED SOLARIS Aquarium Light Fixture:

The white LED used in the I4 series is producing more than 80 lumens/watt.

The new I4 series produces PAR light output levels equal to a 400W MH 15k. It uses 40% less energy than the 400W MH 15k fixtures it replaces. The life of the LEDs is approximately 50,000 hours, so it almost eliminates metal halide and fluorescent bulb replacements. All heat is radiated up and away from the tank; therefore, it does not heat the water like Metal Halides or Fluorescents. This eliminates the need for Chillers. The room air conditioner needs to work ½ as much since the light fixture produces only ½ the heat of Metal Halides which saves even more energy over traditional lighting methods.

A recent 3reef discussion on PAR:
par or lux meter?



Final thoughts:

3reef's Matt Rogers is not the brightest bulb in the box so to speak. So talk of falling photons had his eye's glazed over for a while. But boiling it down. Way down.. It seemed that the LED Solaris fixture was producing more light that could be used by corals going by the numbers shown in this demo. Is that enough to offset costs? Hmmm.. well this could turn into the hybrid car argument which is highly debatable as well. But what the numbers clearly show is that LED light fixtures should not be quickly discounted as a gimmick or fad. That perhaps there are some real merits to an LED light fixture for the aquarium after all.

What do you think?

Has this demonstration changed your opinion of the LED Solaris fixture? Or the future of LED fixtures for aquariums?
Tell us why.

[YellowBelly]

Thanks, in the next couple of years they will perfect the LED technology and the price will come down with more competition.

[lunatik_69]

I saw the 72" model on friday and it looked interesting. It was capable of producing sunny day, over cast days, cloudy days and more. pretty cool.

[baugherb]

They do seem interesting....

[Matt Rogers]

Thanks guys.

By the way - I apologize for the lack of photos. I was using my camera phone and a couple didn't come out. I really wish I had one that showed the tanks too. I am a little embarrassed about that. In spite of that, I had to share.


Do the meter numbers surprise you?

[YellowBelly]

No, at my LFS they switched from two 250w MH's with two 54watt T-5's to the 250w version of the Solaris and the coral growth and colors are much better. The light is on a 90 gallon tank. The Solaris light doesn't have good coverage, especially for the price. The fixture probably covers a distance of 12" wide and the 90g is 18" wide.

[Matt Rogers]

That is an interesting observation. I wonder if that influenced the use of cube tanks in the demonstration?

[YellowBelly]

Probably, what are the dimensions of the Zero-Edge cubes?

[Notturnia]

i love leds.. but the solaris are still too much expencive..
did they told you what kind of leds they used ?

watching that thread i'm thinking about to build one.. no heat... no trouble changing bulbs.. just a "big" investiment on the startup..

[YellowBelly]

Just because LED's last longer doesn't mean they don't lose their intensity and spectrum. The Solaris LED's may need to be replaced as often as our current light bulbs. Metal Halides and fluorescent bulbs can run for years but should be replaced every 8-12 months because they lose their intensity and usable spectrum.