Wind tunnel optimization of FluxScale cooling

We are obsessed with energy efficiency and reliability at GrowFlux. When our engineers set out to squeeze every last bit of efficiency out of our FluxScale LED fixtures, they took a very close look at the cooling fans.  

FluxScale uses two high performance IP68 waterproof ball bearing fans to provide cooling to the 318 tunable LEDs, allowing these devices to efficiently convert electricity to photons. FluxScale automatically adjusts the speed of these fans in real time based on an array of temperature sensors placed among the LEDs. The fans are hosted on a user serviceable fan tray which interfaces to the cooling fins within the fixture - the aerodynamics of these assemblies has a significant impact on fan performance. Minor design adjustments can result in enhanced airflow, allowing FluxScale to operate the fans at lower speeds, improving the energy efficiency and reliability. 

FluxScale features a removable fan assembly, making it the only horticultural lighting fixture in the industry designed to facilitate rapid maintenance of cooling fans. FluxScale is designed for very low fan failure rates, however in the rare occurrence of a fan failure, fixtures can be serviced on site in minutes. 

FluxScale features a removable fan assembly, making it the only horticultural lighting fixture in the industry designed to facilitate rapid maintenance of cooling fans. FluxScale is designed for very low fan failure rates, however in the rare occurrence of a fan failure, fixtures can be serviced on site in minutes. 

Assessing these design features can be done with computational fluid dynamics (CFD) simulation tools, however nothing compares to real world measurements on physical hardware. GrowFlux worked with engineers from ebm-papst, a world leader in cooling fans and motors, to optimize the performance of the the removable fan assembly and cooling fins. 

FluxScale 600AC instrumented and connected to a wind tunnel at ebm-papst. This tunnel precisely  measures airflow; laser tachometers measure fan speed, and other instruments measure power and thermal performance.

FluxScale 600AC instrumented and connected to a wind tunnel at ebm-papst. This tunnel precisely  measures airflow; laser tachometers measure fan speed, and other instruments measure power and thermal performance.

The first step in assessing the cooling performance of the fans within FluxScale is to instrument the fixture with temperature sensors attached to various components inside the fixture; lasers are directed at the fan blades to allow optical tachometers to measure actual fan speed.

In addition to these instruments, every FluxScale fixture is able to internally measure 9 temperature points across the LED array as well as real time fan speed - in normal operation these measurements are reported to the GrowFlux Cloud Control solution for quality assurance within our PrecisionPAR management service. 

Pressure plot showing the relative performance of various fans and fan speed settings against the system airflow resistance within FluxScale.

Pressure plot showing the relative performance of various fans and fan speed settings against the system airflow resistance within FluxScale.

ebm-papst engineers then attached FluxScale to a calibrated wind tunnel.  The wind tunnel is designed according to AMCA210, a standard which establishes laboratory methods to assess the aerodynamic performance of fans. The principle of the chamber is to measure the differential pressure through an array of nozzles. The differential pressure, along with the geometry of the nozzles, is used to calculate a volumetric flow rate of the air moving through FluxScale. An auxiliary blower on the chamber is used to remove any pressure drop caused by the air flow chamber. This assures that FluxScale is being measured at its true operating conditions. Input power, current draw and fan speed are all recorded during the measurement. Subtle design changes were made to the FluxScale fan assembly to fully optimize performance.  

Thermal image showing the LED array within FluxScale operating at full power, indicating effective and uniform cooling due to the low board temperatures and absence of a central hot spot in the middle of the LED array.

Thermal image showing the LED array within FluxScale operating at full power, indicating effective and uniform cooling due to the low board temperatures and absence of a central hot spot in the middle of the LED array.

The detailed analysis of fan selection, fan speed, and design for optimal airflow using these tools is a small part of the work GrowFlux has done to ensure optimal cooling of its LEDs. Effective cooling of LED emitters improves energy efficiency and longevity, allowing our customers to save more energy for a longer period of time. 

GrowFlux featured by Samtec

Samtec connectors in FluxScale LED grow lights

Samtec, a world leader in high reliability connectors for industrial electronics, recently featured our FluxScale fixture on their blog. We use Samtec connectors for one of the most critical electrical connections in FluxScale - the Engine Control Module, which hosts a powerful ARM Cortex M3 processor and has 40 high speed digital and analog connections to the underlying LED engine. 

FluxScale LED grow light and engine control module

When we designed FluxScale, we had to address the design challenge of reliably interfacing a complex multi layer processor module to our high power LED engines while withstanding heat and vibration for upwards of ten years. We selected a particular Samtec connector which offers vibration resistant electrical contacts and a locking connection in a compact footprint. As an added bonus, the connector mates with a tactile and audible click when installing the Engine Control Module, which helps us eliminate quality issues during production. Selecting quality suppliers such as Samtec is an important component of our own commitment to reliability and quality. 

Replacing your HPS lighting with LED

A greenhouse with lots of HPS lights

A greenhouse with lots of HPS lights

Introduction

GrowFlux isn't the first LED manufacturer to tout LED technology to stalwart growers who have stuck with high pressure sodium (HPS) lights over the years. The most common reasons for not adopting LED we hear from growers are:

  • I'm waiting for the next generation of LED products to come out
  • There are too many outlandish claims made by LED manufacturers and not enough standardization
  • The spectrum isn't "right"
  • The efficiency claims aren't valid
  • I need the radiated heat for my crops in the shoulder seasons

We understand the concerns these growers have, and want to present an honest picture of our products so these customers can make the best decisions for their own situation. We hope to show that our FluxScale 600 top light is the industry's best HPS replacement fixture, but we want our customers to make this decision for themselves. Lets go into some detail:

Spectrum differences

Yes it is true, LED horticultural lights DO have a different spectrum compared to HPS lights, which are commonly used for flowering due to the high levels of red light. HPS lights also cover nearly the entire PAR spectrum, while many red/blue LED lights are missing PAR spectrum in the middle of the PAR range.

With GrowFlux tunable broad spectrum technology, growers can choose the spectrum that works for their unique situation while covering the entire PAR range from 400-700nm. In fact, we have developed light formulas which mimic the HPS spectrum nearly identically. While our spectrum is not an exact fit to the HPS spectral curve, the key aspect to our spectrum match is that the proportion of light in each spectrum band is very similar to HPS. This results in predictable flowering results for customers whom are accustomed to HPS fixtures. 

Flowering

Having covered the spectral differences between HPS and GrowFlux LED products, there are a few other elements to touch on related to flowering. Since HPS lights are not tunable, precise manipulations to flowering spectrum are not possible. In addition, GrowFlux lighting products incorporate far red LEDs, allowing growers to further manipulate phytochrome response in short day flowering plants. 

Efficiency & maintenance

The most efficient HPS light on the market produces 2.2umol / watt with a brand new bulb. There, we said it - HPS lights are pretty efficient. Not all LED manufacturers want their prospective customers aware of this fact because many have trouble passing even 2.0 umol / watt efficiency. Keep in mind though that this efficiency figure is with a brand new bulb, and as that bulb progresses through its useful lifespan, the efficiency drops far below 2.0 umol / watt. With high efficiency bulb prices ranging from $70-90 each, and approximately annual bulb changes, the maintenance costs add up with HPS lights. 

Differences in light penetration

We have heard concerns over light penetration into the canopy with LED products from some growers. Since there is a lot of variation in LED fixture optics across manufacturers at the moment, this is not a surprise. We can speak to this specifically as it relates to GrowFlux products; our FluxScale 600AC version 2.0 fixture contains 318 LEDs with an approximate 130 degree beam pattern in a tight array (with outstanding thermal performance).

This LED array packs a serious penetrative punch directly below the fixture (the light from approximately 0-30 degrees from fixture center) . At high angles (between 60-90 degrees from the fixture center), we direct this light around this central hotspot on the canopy with our high efficiency FluxScale reflectors, resulting in highly uniform light. Our reflectors happen to be made of the same Alanod 9033AG material many HPS reflectors use. 

Heat & heat stress

Finally we have heard a lot about heating greenhouses with HPS lights - that the radiated heat from HPS lights is a side benefit to growers in cold regions such as Canada, the Northern US, Scandinavia, and the UK. While heating greenhouses with HPS lights might be a simple solution, we would like to point out that the efficiency is relatively poor from a lifecycle point of view, and this can cost growers a lot of money over time. 

GrowFlux begins FCC testing

We recently tested our AetherMesh IoT wireless modules for compliance with US, EU, and Canadian wireless regulations! Compliance with these regulations ensures that our wireless tech won't emit electromagnetic radiation and radio frequency radiation which might interfere with other equipment and communications. Thanks to the hard work of our engineers, our AetherMesh module passed all of the required tests on the first attempt!

Antenna directed at GrowFlux sensor
AetherMesh Module

Product design for ingress protection

Microscopic view of an engineered silicone foam we use to seal FluxScale from the elements. Ball point pen shown for scale. 

Microscopic view of an engineered silicone foam we use to seal FluxScale from the elements. Ball point pen shown for scale. 

Equipment designed for challenging environments such as greenhouses and indoor farms face the constant threat of dirt and moisture ingress due to exposure to humidity and wet conditions caused by maintenance, rain, and irrigation. Horticultural lighting products in particular can be negatively impacted by ingress of moisture and dirt which severely impact the performance and longevity of the product. In many cases, ingress of dirt and moisture happens despite the equipment manufacturers best intentions- such as sealing an equipment enclosure with air and water tight seals and implementing IP 5x or 6x ingress protection.  So what goes wrong here?

Ingress happens when atmospheric pressure changes act on a sealed equipment enclosure. As the pressure changes, a small amount of positive or negative pressure develops inside the enclosure. These atmospheric pressure changes can cause a daily shift in the differential pressure between the enclosure and its environment. When negative pressure develops inside the enclosure – due to increasing atmospheric pressure – a small vacuum is formed inside the enclosure. Over time, the daily shifts in atmospheric pressure also cause wear and tear on enclosure seals. If a seal becomes compromised at any point due to stress, vacuum pressure inside the enclosure will draw moisture and dirt into the enclosure.

Standardized tests for ingress protection can be performed informally by the manufacturer or can be performed by a certified third party lab. We should note here that these tests are typically done once, in absence of cyclic changes in atmospheric pressure and normal wear and tear. Further, these tests typically won’t catch ingress of water vapor, which can later condense into liquid water, causing condensation and damage. Water vapor can also penetrate joints, seals, and materials much more effectively than liquid water since it lacks the surface tension of liquid water.

Based on our experience working with horticultural equipment and lighting, GrowFlux believes the best design practice for ingress protection is to consider the challenges presented by changing atmospheric pressure, wear and tear, material performance over time, and water vapor ingress. In designing its horticultural lighting product line, GrowFlux has employed several design features to boost our ingress protection:

Pressure equalized enclosures

Mitigating differential pressure in an enclosure is easily achieved by designing in a specialized vent which allows only a small amount of air to pass while blocking moisture and liquid water. Not everyone in the industry is doing this as it increases cost and assembly complexity, however in our experience protective vents pay for themselves. The protective vents we install in every product with a hollow enclosure incorporate PTFE fabric at the core, passing only the amount of air necessary to remove pressure from sealing gaskets. These vents are also commonly installed in high quality LED street lights.

Fully potted power supply

Our FluxScale Series fixtures use the Meanwell HLG driver, which offers the highest efficiency of any 300-600W driver we have seen on the market. This driver is also fully potted (or filled) with thermally conductive, high temperature silicone which protects the electronics inside the driver from water, dust, and moisture while also dissipating the small amount of heat created by the driver – resulting in its high efficiency. These drivers were originally developed for stadium lighting applications, and are well suited to challenging agricultural use.

The fully potted Meanwell HLG IP67 power supply inside FluxScale. We use the highest efficiency drivers on the market in our lights!

The fully potted Meanwell HLG IP67 power supply inside FluxScale. We use the highest efficiency drivers on the market in our lights!

Gasket material selection

Gaskets, O-rings, and other compressible seals can be made of a wide variety of materials. Proper material selection and extensive design for manufacturing is critical to maintaining ingress protection in a seal; designers must consider manufactured part tolerances, material properties at operating temperature, degradation mechanisms in the seal materials, and the sealing material's ability to resist permanently compressing over time (called compression set resistance), among other factors.

GrowFlux encases LEDs in our FluxScale product in extruded T60603 aluminum and anti-reflective coated glass for optimal protection from the elements. We use an engineered silicone foam which is die cut into several custom sealing gaskets; these materials maintain their mechanical properties at high temperatures and compression force for very long periods of time. Wear and tear due to differential pressure in the enclosure is mitigated with the protective vents mentioned previously.

Die cut silicone foam gaskets within FluxScale provide superior ingress protection

Die cut silicone foam gaskets within FluxScale provide superior ingress protection

Potted fans & sealed connectors

The GrowFlux FluxScale 600AC is a fan cooled horticultural lighting product; compared to passively cooled fixtures, lights with fans exhibit better heat dissipation, resulting in higher efficiency, smaller size, and a lighter weight fixture. To ensure that our fans are reliable in wet, humid, and condensing environments, GrowFlux directs its manufacturers to apply a a potting compound to the entirety of the fan drive circuit, rotor and winding, and internal electrical connections, protecting these sensitive components from corrosion and moisture. And since our fans are user-serviceable (in the very rare event we experience a fan failure during the 10+ year design lifetime of FluxScale), we use sealing connectors inside FluxScale to connect our fans. 

FluxScale is the only fan cooled horticultural lighting fixture on the market with user-serviceable fans

FluxScale is the only fan cooled horticultural lighting fixture on the market with user-serviceable fans

Rated liquid tight cable fittings

GrowFlux installs high quality liquid tight cord grips in its LED engines, control modules, and fixture housings to protect cables and to further prevent ingress of moisture, water and dust. FluxScale fixtures specified for wet locations feature a waterproof twist lock power connector and heavy duty UV resistant cable designed specifically for FluxScale. We even have this cable and connector made in Chicago by the legendary industrial cable maker Switchcraft

FluxScale specified for wet locations features a waterproof twist lock power connector

FluxScale specified for wet locations features a waterproof twist lock power connector