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Historically, lighting in farming and agriculture was seen purely from a human standpoint.
While all the sound and fury has been coming from the human-centric lobby, there’s been a quiet revolution going on in the agricultural sector. LED technology has brought massive change to the lighting for horticulture sector and the rearing of livestock. By creating LED systems that offer special spectral outputs, crop and livestock production is enhanced, reducing costs and increasing profits for farmers, while at the same time improving the quality of the product.
Historically, lighting in agriculture was seen purely from a human standpoint. It may be that our light sources left us with little option than to make the best use, or what we perceived as best use, of those sources. Now that we have a ‘tunable’ light source we are able to focus on providing the plants, birds and beasts with the best growing environment.
Horticultural lighting
Research has identified specific wavelengths that are needed to promote growth and fruiting in plants. By applying LED technology it has been possible to create dedicated lighting systems.
For example: chlorophyll absorption occurs in two ranges, 400-500nm and 600-700nm, and that means plants grow most efficiently under blue and red light. It’s worth noting here that plants are seen to be green because they reflect that wavelength. Green light is of no use to the plant at all.
The amount of light required for photosynthesis to take place matters because there is a direct relationship between the two, up to a point. There is a light saturation point where the plant cannot absorb any more chlorophyll, at around 700 micromoles per m2 per second. Any further illumination is a waste of energy (and money).
EXPLAINER: Micromoles
Lighting for plants is measured in micro-moles per second. Micromoles measure the number of photons that pass through a target area; one micromole of light equals a little over 62 quadrillion photons. That sounds very complicated but a new range of spectrometers is now available that provides micromoles per m2 per second readings as simply as they do readings in Lux.
Artificial lighting has been used historically to help extend the ‘growing day’ but we are seeing a move towards total managed environments where artificial lighting provides 100 percent of the illumination in the growing sheds. The LED systems are tuned to provide specific wavelengths according to the growth cycle of the specific plants.
Blue light can stimulate flowers to open up, beginning the plant’s daytime circadian cycle
Red light (and enhanced red light) is good for stem growth and flowering
Infra-red light can mimic the effect of sunset
The ratio between blue and red LEDs is specific to the plant type.
Poultry shed lighting
Getting the light right for poultry breeding is essential, because getting it wrong can be catastrophic for the population of a poultry shed. Stressed fowl become aggressive and it has been known for entire flocks of chickens and turkeys to be destroyed overnight as a consequence of the violence wreaked by the birds.
Research has identified the wavelengths that domestic fowl best respond to and it has been possible to create lighting that mimics the forest under-canopy lighting that birds ‘remember’ in their genetic make-up. This means that domestic fowl have peak sensitivity in the blue-green range, from around 500nm – 700nm, but there is also a substantial response in the UV(A) range – chickens can see ultra violet light that is invisible to humans.
Light at the red end of the spectrum needs to be handled very carefully. Red light promotes sexual activity and growth rate, though it is also thought that the excitation caused by the red wavelength can also be the cause of aggressive behaviour in well-populated sheds.
For the producer, the ideal situation is to create an environment where poultry do not exhibit stressful behaviour, such as over-eating. Layers also need to produce eggs with consistent sizes and ample shell thickness and fowl grown for their meat need sufficient environmental stimulation so that they move around, helping muscle development.
An LED system using specific wavelengths during the course of the day can result in an ideal outcome for the producer. It will produce calm birds that eat less but convert more of that food into body mass, they also come to maturity more quickly in a stress-free state, which means better meat for the customer.
Pig and beef unit lighting
Generally speaking, a lot of research still needs to be done on lighting for pigs and cattle. As we get closer to the human condition, the effect of 100 percent artificial lighting environments suggest that the situation is complicated.
Some of the data is to be expected:
24-hour illumination of pig sheds has reported detrimental effects
24-hour darkness is not an optimal condition
Piglets and weanlings benefit from additional daylight hours, but reproductive behaviour in boars is enhanced by reduced daylight hours. It all sounds very human.
From the point of view of the unit manager, one piece of information is valuable; neither pigs nor cattle appear to have any response to red light. This means that units can be supervised during the night-time by using red lighting – sufficient for security and over-seeing without upsetting the desired circadian rhythms of the beasts themselves.
As research data becomes available, it will be possible to design a lighting regime for pig units and cattle units that is cost-effective for the producer and most beneficial for the beasts themselves.
In summary, as the world’s demand for food increases, producers will need to find the most efficient ways of raising crops and livestock. For those products to have any real nutritional value for the (literal) consumer, then it is beholden on those producers to make sure that growing conditions are optimised for each species. LED lighting is well-placed to deliver the appropriate illumination.
agricultural lighting · horticultural lighting · led agriculture · led lighting · Novel Energy Lighting · poultry lighting · tunable light
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Two-minute explainer: Tunable-white LEDs
Comments off · Posted by admin in LED, LED downlights, LED panels, LED Spots
Tunable-white lighting is one of the biggest trends in commercial lighting. LED developers have taken a serious grip on the photo-biological research being produced by university departments and other groups. We know more about the way that humans function than ever before and you might say that it’s fortunate for the LED community that the science appears to support a practical technology that is perfectly suited to LED exploitation.
Tunable whites use colour mixing
Standard LED colour-mixing uses red, green and blue channels that are adjusted to deliver the entire range of the colour spectrum. Tunable-whites work in the similar way, using of a number of controllable channels to adjust the colour temperature of the luminaire’s white light output. The channels in a tunable-white system all produce white light, but with varying colour temperatures, from a warm tone to a cool tone.
Inevitably, there are levels of sophistication involved in tunable-white systems and it’s vital that the specifier understands not only what is required from the lighting, but also what any particular system is capable of delivering.
Simple systems use two lines of LEDs
Take a warm white LED and sit it next to a cool white LED and cross-dim between the two. Job done? Well, not quite. It’s true that the cheapest tunable whites work in exactly this way. The most basic tunable linear systems use LED strips mounted side-by-side. One channel will be close to 2700K in colour temperature, with the other up around a cool 6000K. The LED strips are mounted inside an aluminium extrusion fitted with an opal diffuser, which does the colour mixing as the light passes through it. It’s very simple engineering but satisfies a basic market with low performance expectations.
Multi-chip versions do the mixing at chip level
More products are using ‘multi-chips’ where a number of tiny LED chips are combined into the same module. This means that the colour mixing occurs as the light leaves the module. Their very small size means that tunable-white products can be made much smaller, so we’re starting to see downlights using the technology as well as linear systems. These multi-chips tend to have a higher performance specification than the individual LED strips, but nothing should be left to chance.
Colour rendering can be compromised
A lot of fuss is made, quite rightly, over the way that white light presents surface colours. We’ve come to expect a good quality of colour rendering, regardless of light source. Tunable whites are not exempt from this issue but it’s not always clear from manufacturers’ data how well a system is performing.
Cheaper products may advertise good colour performance at the extremes of the tunable range, where light is being delivered from either the warm or the cool channel, but there’s no certainty that the mixed light performs equally well. Generally speaking, the greater the number of channels, and systems vary from two-channel to five-channel, the better colours will look under them.
Not all tunable-white systems cover the same colour range
If there is one aspect of tunable-whites that the specifier needs to take great care over, it’s the colour temperature range that’s on offer. While some systems offer a wide natural ‘circadian rhythm’ range that shifts from candlelight to daylight, there are other systems with a much smaller range, from 2500K to 4000K, which should only be considered as a decorative option.
There are three ways to control the tones
- The simplest systems use manual control to alter the white outputs. Expect to see a wall-mounted control panel or a hand-held remote control that enables you to adjust the colour of the light and the amount of light output. There is nothing scientific about this. It’s left entirely to personal preference, which may – or may not – be a good thing.
- Some tunable controls are designed to replicate the effect of dimming on a filament source, where two things happen at the same time. As the light output is dimmed, the lamp warms up in the same way as a traditional tungsten filament lamp. This is still a manual control method, but has the benefit of mimicking a filament light source. The tunable range tends to be very small, again mimicking the conventional tungsten lamp.
- More sophisticated control strategies are designed to manipulate the circadian rhythm of room occupants. This means that the lighting settings are programmed into the control architecture. Shifts in colour temperature and light level can be pre-set or can be instigated by a manual over-ride. This is the method that’s being used in recent school installations in Scandinavia.
Three discrete channels could be a solution
It’s been pointed out that not all ‘tunable-white’ mixing requires a full colour range. Complex tunable-white schemes mean that you should be able to call up any colour temperature within the mixing range. But some clients will call for specific colour temperatures, often those that are commercially available, such as 3000K, 4000K, 6500K. If that’s the case, then it may be simpler – and cheaper – to consider having three discrete lighting channels operating separately within a bespoke housing.
Photo credit: Glamox Luxo
colour temperature · LED downlights · led lighting · led panels · Novel Energy Lighting · school lighting · tunable light · tunable wite light
The lighting industry is gearing up to launch a key weapon in the war on the deadly Zika virus – special LED lights.
Fred Maxik, the chief technology officer of Lighting Science, is exploring the possibility of constructing a special trap for the mosquito which carries the life-threatening infection.
Transmitted via a bite from the yellow fever mosquito, Zika is extremely serious for pregnant women, as there’s evidence it causes birth defects such as abnormally small heads. Experts now warn that they expect the Zika virus to spread to all countries in the Americas, including the Caribbean, except Chile and Canada.
Lighting Science – which uses special tuned lighting for applications such as water purification, turtle protection and space use – is developing a tuned light trap for the yellow fever mosquito. The company is already working with the US Department of Agriculture on its programme of light-based insect traps. With a little modification, it thinks it can develop one specially to help in the war on the Zika virus.
This is because different mosquitos are attracted to different wavelengths of light. By ‘tuning’ the light specifically at the yellow fever mosquito – or Aedes aegypti, to give it its scientific name – the light traps can be targeted.
‘There’s no one size fits all,’ Maxik told Fortune magazine this week. By testing the traps in the field, the company can work out exactly which spectral signature attracts and which repels the creatures. Special lights can then be developed to deter the mosquitoes from approaching buildings such as ante-natal clinics and hospitals in high-risk zones. ‘We’re trying to create light that’s useful for our own purposes.’
LED lamps · led lighting · led tubes · Novel Energy Lighting · tunable light · zika virus
