LED vs. HPS: Truth about photosynthetic eff. & uniformity

[desert fox]

Tagging along. They are getting pretty impressive. I would like to see better CRI. I cant have my neighbors think I am getting abducted by aliens if I carelessly leave the tent and door open. I suppose I could rig up a trigger switch to turn off the light and have a some whites. I just find I catch plant issues and deficiency so much quicker with CMH. I only run when its cold. will be running t-5s for flowering next summer, and keeping things vegging with normal outputs t-8.

I think I will get one in the next 5 years.

 

[flat9]

By the way anyone going with Houyis and saw the link I posted, please don't get the 100w COBs -- this is overkill. Well may be okay but only if you buy more smaller units (say four 2 x 2 array units to cover a 4' x 4' grid). But in the link I posted that bombadil.360 quoted above, the problem of irradiance being focused on one spot will only be exacerbated w/ even more unused light. I went with the widest reflector they offered at 110 degrees and got a 4 x 4 unit with 75 watt COBs, and it does pretty well, though I wish I had just gone with 4 of the 2 x 2 units instead.

From the resources I've seen (some research papers floating about on google scholar), cannabis seems to grow very well at 1000 PPFD (neglecting absorption rates at different frequencies and just assuming a flat distribution). Anything beyond 1500 is overkill. So yeah, if you can get a nice uniform coverage of about 1000 PPFD, that's ideal.

It sounds like Cycloptics products do a very good job of this. I'm tempted to buy a couple and try them out. Does anyone know how to cover a 4 x 4 with them? Seems like 2 wouldn't be enough but 3 would be too much....

 

[Beta Test Team]

With Cycloptics you account for wall and ceiling reflectivity, it's unlike using traditional style HID reflectors. For a 4'x4' area 2 or 4 of them, it's generally better to use even number that luminaires, if going with 2 of them keep them farther from the canopy to increase uniformity. Make sure to something like ORCA film, not mylar, on walls and ceiling if possible.

You should probably read my posts in the CMH thread about Greenbeams, like from page 441 and on. There's a lot to consider when using that kind of luminaire.

For irradiance, 1,000 PPF is too great all day; if that much radiation per day doesn't reduce plant growth or photosynthesis, it at least is a waste of energy (and money). That one study all the others cite can't be used to draw conclusions about PPF all day (even though the authors claimed otherwise). Total photons per day are more important than per second. So shoot for around 500-700 in veg and 700-900 in flowering.

 

[Beta Test Team]

To everyone reading, to recap and define (once again):

This thread is about the efficiency of luminaires in converting joules/s (watts) into photosynthetic umol/s (photons within 400-700 nm band). And it's also about the uniformity of that umol/s as irradiance (umol/m2/s) over the canopy (e.g. 3'x3'). As well as it's about cost comparison of luminaires on a umol/s basis.

What this thread is not about is everything else that is not listed above. So if people want to discuss anything not listed above, please do so in a new thread. It's not only rude to the OP to derail a thread, it's rude to any members that want to read or participate in the thread - especially when the people derailing the thread are ignorant and wrong.

I've said it before and it still holds true: Most of the time here keeping a thread on topic is like hearing cats.

 

[Beta Test Team]

@ OIBI:

Looking over the comments* to the study this thread is based upon, I found one that goes to the heart of what we discussed shorty: re-lamping and output degradation over time.
* http://www.plosone.org/article/comments/info:doi/10.1371/journal.pone.0099010

From Dr. Bugbee:

http://www.plosone.org/annotation/listThread.action?root=81189

Early versions of this manuscript included a ten year time horizon, but based on reviewer comments (including economists), the ten-year analysis was not included in this version for two reasons:

1) The efficiency of the best fixtures from both technologies is equal (1.7 umol per Joule) so there are no long-term savings in electric costs among the most efficient fixtures.

2) As discussed in the manuscript, long-term maintenance costs are uncertain and do not necessarily favor LED technology.

For these reasons there is not an economic cross-over point between technologies and a five-year time horizon (commonly used in business decisions) was sufficient to compare options.

Here we compare the costs over the lifetime of an LED fixture.

Operating life for LED fixtures is generally not specified by manufacturers, but a 50,000 hour lifetime is reported for individual LEDs. Extending this lifetime to the entire fixture makes the assumption that no other component will fail (such as power supplies or fans). If we make the assumption of no premature failures and no maintenance costs over 50,000 hours, the initial capital cost of the most cost effective LED fixtures is $3,200 for 1750 µmol/s of output (the equivalent photon output of one HPS fixture; based on photon output and cost of fixtures in Table 3). After 50,000 hours the photon output of the LEDs is predicted to be 70% of initial output.

If double –ended HPS lamps (bulbs) are replaced every 10,000 hours (at 95% of initial output), and the entire fixture is replaced at 30,000 hours, it would cost $420 (3 x $140) for three replacement lamps and two fixtures (2 x $500 = $1000), for a total of $1,420 capitol and maintenance cost for the same 50,000 operating hours.

LED fixtures do not necessarily have a long-term economic advantage when capital costs are included.

As the title indicates, this article focuses on greenhouse applications, but the data and principles can be applied to indoor plant growth. Indoor lighting can take advantage of unique spectral effects, which we are currently investigating (Cope and Bugbee, 2013; Cope et al, 2014). LED fixtures have many unique properties and have the potential to revolutionize the industry.

We hope the data in this manuscript will help analysts giving energy rebates and incentives to make informed decisions. These incentives should be allocated based on independently verified efficiency ratings (in µmol/J). Both HPS and LED manufacturers tend to inflate claims of fixture efficiency. Bulk discounts and rebates are available for both technologies. The associated on line calculator (http://cpl.usu.edu/htm/pu...) allows users to incorporate individually quoted costs, maintenance estimates, electricity rates, and differences in photon capture efficiency.

 

[Beta Test Team]

This is also interesting, a new DE by PARsource:

http://www.plosone.org/annotation/listThread.action?root=83088

We tested a new, double-ended, 1000-W HPS fixture from PARsource (Petaluma, CA). Measurements in an integrating sphere indicate an efficiency of 1.76 micromoles per Joule at an input voltage of 208 V and an efficiency of 1.77 micromoles per Joule at 240 V.

These measurements indicate no significant change in efficiency with input voltage. This finding may apply to other DE-HPS, electronic-ballast fixtures. (Greenhouses with 3-phase power have 208 volts; greenhouses with single phase power typically have 240 volts).

This fixture has an open luminaire similar to the ePapillion fixture, and thus has a broad photon distribution. The manufacturer’s suggested retail price is $599. The company has plans to release this DE-HPS lamp with a more focused luminaire. They also plan to release a version that operates on 120 volts.

 

[wordsux]

To me it seems to me led's would make most sense in a commercial application. I think the power savings in cooling would really add up the most.

 

[wordsux]

Also for home growers it allows you to run more lighrs without showing up on leo's radar with less power being used.

 

[guen]

It's also just a matter of efficiency per watt. In places like California and Hawaii, electricity bills can easily get into the thousands, and amperage is sometimes limited, so getting better results with less power is important. Growing is finally a legitimate business, where we have to be conscious of the carbon footprint (which is huge for all indoor growers combined) and always improving the bottom line.

 

[tenthirty]

Are you sure we don't want photorespiration? Why?

And why is there no way that's the real spectrum? I'll ask them about the low resolution spectroradiometer. Would a low resolution somehow give a full-spectrum result like this? Because it's not "zoomed in" enough so just gets a general reading? Tell me specifically what equipment at what settings would be accurate to use, and I'll see if I can get that data.

I'd like to find an equivalent graph of the sun's spectrum. Anyone got it? Or does it vary too much between latitudes and seasons?

Here ya go.

 

[Beta Test Team]

To me it seems to me led's would make most sense in a commercial application. I think the power savings in cooling would really add up the most.

Except:

a.) They are likely not going to give you a power savings vs. best-of-breed HID, maybe in a few years when the technology develops more, as this thread as pointed out many times:
https://www.icmag.com/ic/showpost.php?p=6679113&postcount=72

b.) The poor irradiance uniformity (footprint) of LEDs means they're not well suited for commercial grows with large canopies.

 

[Beta Test Team]

It's also just a matter of efficiency per watt. In places like California and Hawaii, electricity bills can easily get into the thousands, and amperage is sometimes limited, so getting better results with less power is important. Growing is finally a legitimate business, where we have to be conscious of the carbon footprint (which is huge for all indoor growers combined) and always improving the bottom line.

As has been pointed out many times in this thread, current commercial LEDs are not more efficient than best-of-breed HID. On a per watt basis (joules per second) HPS gives better efficiency of creating photosynthetic photons than best-of-breed LEDs. Well, at least out of the studied commercial luminaries.

The best HPS was at 1.77 umol/joule, while the best LED was at 1.7 umol/joule.

 

[Beta Test Team]

Not really spamming, because I'm here to have a substantive conversation. Spamming is BS only. The title of this thread is "LEDs vs. HPS lamps: A reality check" I'm writing within this topic.

If you weren't spamming you have my apologies.

I'm happy to see your critical response to the link I left because I'm not techy enough to be able to notice those issues. I will ask the company owners about them.

So you think they are lying on that spectrum graph? Or could they just have another way of approaching it? I'd love to know exactly what questions you'd ask to clarify, because I will ask them.

I think they are either using a low resolution spectroradiometer (which means for example, data points at 10 nm, instead of every 0.5 or 1 nm), and the rest is filled in with linear interpolation (or other math). Or, they're making the SPD look how they want it to look.

The reason I made that claim is the SPD is too flat, it should be more spiky - at least there should be more a difference between some nm ranges.

Granted, I could be wrong, but I strongly doubt it.

I've already got a few thousand bucks into this, and like I said, it'll take a few months to really have a sense of it, but these LED's look like normal lights, and they are bright. Those two factors together are encouraging.

Are you sure we don't want photorespiration? Why?

Yes, I am sure, for C3 plants like Cannabis. Because photorespiration is basically a stress response (in very simple terms), and increasing photorespiration generally means reduced rate of photosynthesis (by upwards to 25% reduction). We want plants to respire most at night, not the day. There will always be photorespiration (from nitrogen metabolism), but we do not want to increase it.

http://hyperphysics.phy-astr.gsu.edu/hbase/biology/phoc.html#c5

And why is there no way that's the real spectrum? I'll ask them about the low resolution spectroradiometer. Would a low resolution somehow give a full-spectrum result like this? Because it's not "zoomed in" enough so just gets a general reading? Tell me specifically what equipment at what settings would be accurate to use, and I'll see if I can get that data.

See what I wrote above.

What should be done is using a good spectroradiometer at 0.5 or 1 nm step size.

I'd like to find an equivalent graph of the sun's spectrum. Anyone got it? Or does it vary too much between latitudes and seasons?

See what tenthirty posted. The spectrum of radition plants get does not change much over the seasons (which is why MH for veg and HPS is flowering is not accurate). Please note how spiky that SPD is from the sun (high resolution), and compare that to the SPD from the luminaire you're selling.

 

[Beta Test Team]

guen,

One more false claim from that site is how they claim yellow light is best for opening stomata, that's not correct. UV to blue is best at opening somtata, then comes red in terms of efficiency. And red is around 5-10x less effective than blue.

Also, yellow light has been found to cause photoinhibition, and reduce plant growth. It used to be thought that was from green light, but more recent research has found yellow light more the culprit.

So limiting yellow light is good idea, not increasing it, as LEDs go. But that company seems to try to tout their yellow light...

 

[guen]

Any chance you'd be willing to call them and hash it out, then report back? You know way more than I do about the technical stuff. You can get the owner (Rami) on the phone and it would be great to hear the results of that call. The reason I think it's worth pushing is because I've seen these lights in person, and as I said before, they are very bright, and very normal looking in comparison to the red/blue weirdness we've all been stuck with for a few years here.

 

[flat9]

Except:

a.) They are likely not going to give you a power savings vs. best-of-breed HID, maybe in a few years when the technology develops more, as this thread as pointed out many times:
https://www.icmag.com/ic/showpost.php?p=6679113&postcount=72

b.) The poor irradiance uniformity (footprint) of LEDs means they're not well suited for commercial grows with large canopies.

I really don't think (b) is true. It's more that people splurge on huge panels rather than buying multiple smaller panels and thus they focus too much light on one spot. This isn't a failure of LEDs themselves, it's a failure of those who use them.

 

[Beta Test Team]

Any chance you'd be willing to call them and hash it out, then report back? You know way more than I do about the technical stuff. You can get the owner (Rami) on the phone and it would be great to hear the results of that call. The reason I think it's worth pushing is because I've seen these lights in person, and as I said before, they are very bright, and very normal looking in comparison to the red/blue weirdness we've all been stuck with for a few years here.

No, sorry. I am pretty sure how such a call or email interaction would go (not well). I don't think it's a good use of my time.

 

[Beta Test Team]

Except:

a.) They are likely not going to give you a power savings vs. best-of-breed HID, maybe in a few years when the technology develops more, as this thread as pointed out many times:
https://www.icmag.com/ic/showpost.ph...3&postcount=72

b.) The poor irradiance uniformity (footprint) of LEDs means they're not well suited for commercial grows with large canopies.

I really don't think (b) is true. It's more that people splurge on huge panels rather than buying multiple smaller panels and thus they focus too much light on one spot. This isn't a failure of LEDs themselves, it's a failure of those who use them.

Very good point, and I agree. Though at this time most LEDs are too focused (poor footprint uniformity), however, as you and Habeeb pointed out, there are newer LEDs that are moving to less focused energy so the future is bright for LED and LES.

I totally agree that the way LEDs are used has a big impact on their efficacy (for large canopies in particular) - I made this point in the first post, I think. But I'm glad you raised it again.

Thanks.

 

[stoned-trout]

the reality is led aint happening for commercial growers only small scale or those with money to waste..end of story

 

[DarkGreenGoo..]

the reality is led aint happening for commercial growers only small scale or those with money to waste..end of story

There are a number of commercial grows running LED's now. As well as medical collectives.