1. The use of a fluid as a heat sink (e.g. distilled water or oil) will enable cooling of the individual LED chips very efficiently and quickly, and without the need for expensive metal heat sinks.
2. The use of heat transfer fluid will enable efficient transfer of heat between the lighting system and the growing solution (aquaculture and hydroponics solution).
3. The use of a non-conductive fluid will avoid the need to encase the LED reducing cost.
4. The use a lay-flat tubing will enable a low cost solution for casing the lead and to contain the thermal fluid.
5. The use of a diffused material in the lay-flat tube will enable light scattering to all directions without the need of optical lens (preferred material is diffused ETFE lay-flat tubing due to the superior optical properties).
6. The use of the lay-flat tubing will enable easy disassemble when lighting is not needed (e.g. summer).
7. White plastic beads suspended in the fluid could enhance scattering of the light even more if diffused plastic is not enough.
A device to encase high power lead chips for plant lighting, and therefore avoiding the need of an expensive metal heat sinks, and with the added benefit of heat collection to use in other heat demanding process is described.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 – Shows the image of one individual and complete system. In reality, we would have several lay-flat sections connected to a circulation fluid grid on the top and one in the bottom. *The circulation grid would have only one (water to water) heat exchanger.
*The circulation grid has a pump to keep the fluid circulating (pump will supply energy loss due to resistance and turbulence in the fluid, although there will be no need to elevate water as the whole system is connected and full of fluid).
Fig. 2 – Shows the ideal circulation in respect to the natural convection flow.
Fig. 3 – Shows the disposition of several lighting systems between plant growing towers. The height of the lighting system will depend on the height of the vertical growing system. We could have anything from a few metres up to a few dozen metres up.
Fig. 4 – Shows a schematic of the inside of the lay-flat with white matt plastic beads suspended in the fluid. Plastic beads will be present throughout all the fluid.
Their function is to increase light scattering and create an appearance of a fluorescent tube. Their size will likely be much smaller than the one that is seen in the drawing.
DETAILED DESCRIPTION OF THE PREFERRED MATERIALS
====Thermal fluid- Heat sink and heat transfer fluid=====
- Compatibility with the LED chip. (e.g avoid the silicon coat damage and delamination problem).
- Low/no conductivity.
- Available worldwide.
- High specific thermal capacity.
- Environmentally sound to obtain and dispose.
- Distilled water (e.g. rain water) – Free, available everywhere, and good spectral transmittance on the full PAR region.
- Vegetable oil – Costly, poor, and spectral transmittance on the blue region.
–Considerations about the thermal fluid–
The challenges to immerse LED chips in a fluid is:
- Electrical conductivity of the fluid.*
- Compatibility with the silicone overcoat.**
- Electromagnetic Spectrum absorption of fluid – spectral transmittance profile.***
- Delamination of chip cause by moisture or other solvents.****
*Electrical conductivity tends to be zero in distilled water. What could happen is that the left over of the industrial process and solder fluxes may dissolve in water, so it may be necessary every few water exchanges to fully clean the electronics (EC could be monitored to achieve it).
**Compatibility with the silicon overcoat should be fine with pure water. Both chemical and volatile organic compounds (VOC) should be considered as silicon overcoat is normally gas permeable (and could present discoloration and surface damage when exposed to VOC).
***Water spectrum absorption is low for PAR (Photosynthetically active radiation) band.
****Delamination: Some of the new LEDs have JEDEC Moisture Sensitivity Level 1, so they can be fully immersed in water for longer periods, even for considerably longer period than what is the normative guarantee. If long time resistance is a problem, an extra layer of silicon could be consider, and if this is not viable the use of oil should be consider.
====Layflat Tubing material=====
The ideal material for the Layflat tubing is ETFE, due to the excellent transmittance properties (this material is quickly becoming the standard for new greenhouse cover installations).
Layflat should be of the diffused quality to scatter light. Different than most diffuse material, diffuse ETFE doesn’t present any light loss when the precision experiments are realized. Check F-CLEAN diffused version.
====Micro Plastic beads for enhanced diffusion=====
No specific material has been considered. Material will need to be compatible with the thermal fluid.
====Micro Plastic beads for enhanced diffusion=====
No specific pumps have being considered.
However, the pump will ideally be low power, high efficiency (it will only have to add the energy loss by resistance and fluid turbulence; there is no potential gravitational energy to be added or lost). It will also have to be compatible with the size of the plastic beads if they are used.
====LED Power Supply=====
A constant current power supply would be the ideal driver, and the LED would be connected in series; respecting a limit of 60 V to class as safe voltage.
Open Source License
====Copyright Aquaponics Lab 2015==== www.aquaponicslab.org
This documentation describes Open Hardware and is licensed under the
CERN OHL v. 1.2.
You may redistribute and modify this documentation under the terms of the
CERN OHL v.1.2. (http://ohwr.org/cernohl). This documentation is distributed
WITHOUT ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING OF
MERCHANTABILITY, SATISFACTORY QUALITY AND FITNESS FOR A
PARTICULAR PURPOSE. Please see the CERN OHL v.1.2 for applicable
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