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Lights or Solatubes

Posted by Master_Eeyore 7b (My Page) on
Sun, Jun 26, 05 at 15:21

New here, and had a question about lighting, it seems to be the greatest expense. What is your opinion on installing a couple of solatubes in the room directly above the area where I want to start growing? According to the web site, the 21" is the equivalent to 60% of a 400 watt Metal Halide light. I primarily want to do this in the winter, my other concern is the length of the day. Thanks for your time.


Follow-Up Postings:

RE: Lights or Solatubes

If you want to grow in a controlled environment year-round, HID or other lighting source is a better idea.

The solatubes have the same problem as the sun in the winter, it's only out for a few hours and it's very low intensity and will be much less light than 60% of an HID lamp.

That 60% claim assumes full sunlight in the middle of summer.

Solatubes will work if you only want to overwinter the plant and don't expect fruit.

RE: Lights or Solatubes

We have smaller (21" is for commercial apps I think) Solatubes in a bathroom and our laundry area. I will sometimes set seedlings on the cookbook shelf in the laundry area to get some filtered sunlight, but I don't think you'd grow more than an indoor houseplant in a spot like that. It provides pleasant light but it's not particularly intense.

RE: Lights or Solatubes

I looked into these and talked with several companies. The best claim any of them made was that a larger one would equal 10,000 watts of incandescent light.

One rep was very nice but I was surprised in that they had never taken before and after light meter readings, just photos (which can be photoshopped to make it look much lighter).


RE: Lights or Solatubes

There are actually some commercial grade Solatube Daylighitng Systems that can bring in massive amounts of light, especially during the Summer months. Some of the 21" dia. units offer Fresnel lens technologies or internal reflectors in the domes to more efficiently capture low angle sunlight, so the products can maximize daylight early morning, late day, and during winter months. There is even a new 29" dia. tube, the SkyVault M74 DS that is designed for large industrial spaces. In sunnier climates at peak times of the year, this product can deliver 40,000 lumens of light. This is pure daylight, focused on the visible spectrum (400-760) nanometers, reflected by teh Spectralight Infinity tubing, which has the highest specular reflectance in the world at 99.7%. Harmful UV light is filtered out at the dome and the tubing itself focuses only on the visible spectrum of light, so very little infrared is delivered to the interior. Basically, these systems don't produce nearly the heat that the equivalent electric lights would produce. The tubing can run extensive distances and these products are used to light all sorts of commercial buildings, allowing the electric lights to be turned off during daylight hours. We have seen several algae companies use Solatube technology in their production process and also have several test projects with hydroponic/aquaponic projects.

Here is a link that might be useful: Solatube Daylighting Systems for Commercial Applications

RE: Lights or Solatubes

Welcome to the forum Solatube. Are you a supplier of these?

When I looked at them, I decided it was not worth it in my case, as efficiency is lost as tube is lengthened and with every curve or turn. If you can build your grow setup directly under the holes you will put in the roof and keep the distances short, the common fresnel lens types on the market are a decent option. When I did the economics, though, it was simply a far more attractive option to make or buy a small greenhouse.

Problems that made me prefer the greenhouse - the sun tube requires certain inclinations on the roof to properly catch light and if you don't have them you have a bigger project on your hands. Also the shape and orientation of my pitched roof would not allow placement except near the high edge, or the roof itself would have poor exposure for parts of the day that I would lose decent Watts/sq meter.

There are comments online about people growing crops inside that are concerned they need to hide their high electric consumption from authorities, and they had special motivation to use this product.

It really is a good concept,especially if you have a flat roof such as in an industrial warehouse and you absolutely must work inside as in a an induistrial warehouse or plant, but as was pointed out, in winter the Sun intensity is lesser and days shorter so the benefit is less so to install these for growing it would be advisable to use realistic outputs and carefully study the arquitecture of your roof, distances involved, etc.

It was a nice option in Florida to grow a hobby stand of sweet shelling peas inside in the summertime though.

Also from what I remember, these would transmit most IR just as great as visible (as high as 1600 nm), but I seem to recall that the polycarbonate domes used have additional coatings on them that reflects IR like greenhouse panels. So for my use, I'm just saving up for a greenhouse, though if money were no objective this would be a fun experiment.

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