Hydroponics BC

Water Cooled Lights

Since water cooled growing lights have been in use by the hydroponics industry for a number of years now, it seems like a good time to look at them more closely and the best place to start is by showing just how leading edge a development they are - probably much more so than most people imagine. Why do I say that? It is because I have in front of me, a scientific research paper from NASA, the people that send out the space missions. The author is a researcher at the NASA Ames Research Center, and the research was conducted in early 1996 at an Antarctic research station.

The project purpose was to develop a mini-farm sufficiently productive to supply food for a manned mission to Mars. It had to be energy efficient, small, light weight, and most importantly, highly productive - all desirable attributes for the home grower as well. The research was done using a high productivity growth chamber (CAAP chamber) fitted with lighting which featured " ....a recirculating water jacket that absorbs and removes non-photosynthetic energy". In plain English, they used water cooled lights - the same type of water cooled lights that have been available to home hydroponic growers for several years already.

To quote the report:

"The high-efficiency lighting system, providing unmatched photosynthetic radiation production and delivery efficiencies.........."

"The area required to produce the necessary human diet is much less in the CAAP"

"Yield expressed on an area, volume and integrated resource input basis are all greater for CAAP"

"Performance of the lighting system has been excellent........."

"The performance per unit area is so much greater in CAAP......."

Their conclusion at the end of the project was that even the results they got from this preliminary study met the minimum requirements for a mini-farm in space, something they had not been able to achieve with standard hydroponic practices and lighting,, and they saw many areas which they could still improve.

While growth chambers have been used for decades, the report stresses that it was through use of the water cooled lights that the performance has been optimized to the point that it may be feasible to grow the food in space. One has to think that if research scientists and engineers at NASA conclude that water cooled grow lighting has proven itself in their application, it is probably worth looking at for use in other applications.

Can home hydroponic growers benefit from these lights as well as NASA? Yes, because using a growth chamber doesn't require rocket scientists - there are several manufacturers of perfectly suitable growth chambers in Canada, the US, etc. How do the results obtained from these chambers compare to those of NASA? With billions of dollars to play with, NASA can spend a lot on fancy equipment and will probably do better than a home gardener, but still, the home gardeners have done very well and they got there long before NASA.

The growth chambers already available to the home grower have been shown by numerous growers to provide increases of about 30% - 50% beyond what was produced from standard hydroponic systems with everything else being the same - the same person doing the growing, the same strain of plants being grown, the same nutrients being used, etc. If the only thing they changed to obtain the increased production was to use a water cooled light equipped growth chamber, it suggests that using a similar growth chamber could provide anyone with a similar increase in productivity. What does a growth chamber consist of ? At its simplest, it's a box fitted out with everything needed for growing. It would have the light, fan, controls, ballast, watering and any other necessary equipment, already assembled.

One great advantage of these units is the ease of use. There is no trial and error period, or any of the trouble of installing a system assembled from parts. The growth chambers are already proven products with all the components provided, all sized properly and all assembled correctly. They can sometimes be purchased as kits for self assembly but generally they are sold in the completely assembled form so they are true plug and grow units - plug them into the power and water supplies and start growing.

And what are the advantages? Why should anyone bother with water cooled lights in a growth chamber if they've always grown OK without them before? There are many answers, but to quickly summarize:

  • 1.Greater productivity at all times in a properly built growth chamber
  • 2.Easier control of disease and insect pests
  • 3.Increased efficiency of CO2 enhanced operations
  • 4.Reduced size of the installation
  • 5.Reduced ventilation needs and no noise, odor or light glare into the surroundings
  • 6.Better isolation of the growing environment from it's surroundings
  • 7.Enables year round operation during any weather conditions.
  • 8.Ability to use a modular, plug and grow approach for rapid, easy setup and expansion.
  • 9.Fast and easy teardown and removal when needed

Since use of the water cooled lights is what makes the growth chambers practical, some discussion of the lights themselves is called for. The hydroponic industry has had water cooled lights available to it for a number of years already and like any other new innovation they've had their teething pains. The initial offerings from several different manufacturers were either huge, heavy and difficult to handle, leaked constantly, were difficult to take apart for cleaning, prone to cracking and meltdown, or just too expensive but these problems all seem to have been overcome finally. The latest version on the market exhibits good design, ease of use, and finally a reasonable price for a complete package of parts - including a reflector.

The lights use standard HPS and Metal Halide lamps, which are fitted into a water jacket that removes the heat while still allowing all the visible light to reach the plants. This warm water can either be run to waste if there is no wish to use the heat in another application, or the heat can be recovered for use elsewhere. The number of cooling options is considerable, so only a few will be mentioned here.

Run to Waste

For growers with just a few lights, it is entirely practical to just run a hose from a tap to the light and then to waste. This is the cheapest and easiest way, but you do need good quality water and so have to use the municipal supply.


Recirculating System

For those with a bit more concern for the environment or who want to keep water costs down, there are a number of cooling options which can cut down on the consumption of water and/or electricity. One of these is simply to use a recirculating system which will allow you to use other sources of water and is in fact the system recommended by the manufacturers of the water cooled lights. The heat exchanger keeps the water flowing through the lights completely separate from whatever the cooling supply is, so the cold water can be from any source. Common examples are sea water, streams, lakes, wells or even swimming pools.


Extra-low Water Consumption System

An interesting variation on a recirculating system is one which allows use of city water without increasing a facilities water consumption by much. It does this by tying the heat exchanger into the domestic water supply in such a location that whenever any water is used for any domestic purposes the light cooling system is also cooled. Depending on where one puts the reservoir it can also provide heating for a solarium or greenhouse too. While it does require a fair sized reservoir, a considerable number of lights can be cooled with very little extra water, which is a great advantage for the areas where water is metered.


Lights as a Pool Heater

Another option is to waste the heat from the lights to a swimming pool. For people who don't have an in-ground pool installed in their back yard, a coated steel above-ground pool is a great alternative. They are cheap, easy to install, and enjoyable. You not only can get rid of the heat from your greenhouse or solarium, but you also get a heated pool.


The Easiest Way of All

The easiest way of all, is great for people who just want to get rid of the heat and are lucky enough to live on a lake, stream or the ocean. All that is required is to string several hundred feet of garden hose from the pump in the reservoir, out into the lake and then back to the house where it is connected to the inlet to the lights. You then just pump the light cooling water from the reservoir, through the hose in the lake where it gives off its heat before re-entering the lights. No expense for cooling water, no fancy plumbing, no heat exchangers - just the lights, a pump, a filter, a small reservoir and some hose.

References:
Bubenheim, D.L. 1998
Demonstrating Feasibility for Regenerative Life Support Systems
The CELSS Antarctic Analog
SAE Technical Paper 981532

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