Geeky Groving, or a basement farm

Good day to you, dear geeks and sympathizers! In this publication I want to raise the topic at the intersection of physics, biology and common sense.

As a matter of fact, it makes sense to do, describe and read these things only in the presence of boredom and languor of spirit caused by self-isolation. This is about common sense. The rest is under the cut.

Everyone knows that in our century of industrialization, an intensive way to increase production volumes and general marketing, the quality of food products is the tenth or even the fiftieth, according to effective managers and other similar malicious fauna. At the same time, many people confuse safety, durability or other qualities of the product with the main criterion for the quality of food products - their taste. Otherwise, where would tasteless tomatoes, cucumbers with the smell of fish come from on our tables, etc.

I, as a person who was unsatisfied with the stomach, did not want to put up with this unfortunate fact, and therefore stood on the slippery path of partial self-sufficiency. In my region (Bavaria, Germany) the summer is short, the weather is changeable, and generally narrow latitudes. The people grow everything in greenhouses, but this semi-natural action disgusts me for various reasons. I want, you know, to grow corn beyond the Arctic Circle (C). My plan was simple and naive, so it was a success: we grow plants in the basement to the maximum possible size, then we plant them in open ground after reaching acceptable temperatures.

A bit of philosophy: a plant is the essence of a factory for creating substances from substances through the use of radiation energy. One of the substances - carbon dioxide, is everywhere and always. Other substances - minerals and organics, are present in the soil. It is possible to simply and reliably create beautiful soil by applying fertilizers and additives, the plant itself will take what is needed.

But with radiant energy, everything is not so simple. The current trend in this regard is to illuminate plants only with the spectrum used in photosynthesis (420 and 640 nm) in order to save electricity. I personally consider this a dead end for several reasons: 1. For millions of years, plants have developed under the sun, which hints at their maximum fitness specifically for the full solar spectrum. 2. It is difficult (as an option - expensive) to get lamps that REALLY emit the above spectra. 3. Taste qualities of vegetables grown under such light compete on equal terms with cardboard, but lose to wet wipes. Sad but true.

In short, for my basement plantation I needed light sources with the following properties: 1. As close as possible to the solar spectrum of radiation. 2. As even as possible illumination of plants. 3. High energy efficiency.

Having absorbed a little of the collective wisdom of civilization, I did start an experiment with the following participants:

1. Electroluminescent lamps, a combination of five Philips TL-D 23W 840 Super 80 (MASTER) 97cm and four Osram L 30W 880 Lumilux 89.5cm - SkyWeiß. The total capacity was 205 watts (made two, because these lamps are the cheapest option of all available). By the way, all the lamps have electronic ballasts, for archaic chokes and starters are not our method. Energy Efficiency: 80 to 88 Lumens per Watt. So-so, but better than Ilyich’s bulb. Their spectra complement each other:



The design is simple, everything is wooden and plastic. Well, besides a metallized mirror film.

Trying:



In the work:

2. Home-made LED panel made of tape with a color temperature of 6500 Kelvin, the total power of 200 watts. Energy Efficiency: 96 Lumens per Watt. This is already good. Power supply - computer PSU. The spectrum is typical for inexpensive tapes:



Tape glued to a frame assembled on rivets from an aluminum corner 15x15x2 mm. The design is simple, cheap and efficient in terms of passive cooling. Scalability is limited only by the material and angle design:



3. Crème de la Crème: Metal halide discharge lamps Philips MASTERColour CDM-T Elite 50W 942 G12 (not to be confused with DNAT!). With these lamps, everything is not so simple: they are point sources with high brightness and heating, they need special ballasts, and they are explosive. Energy Efficiency: 100 Lumens per Watt. Parity with LEDs. Spectrum:
Complete from ultraviolet to infrared, closest to the sun:



For a more even distribution of light, four 50-watt lamps were used.
The design of the luminaire was created taking into account safety requirements, a thick (0.5mm) aluminum reflector / diffuser, high sides from a tin corner:


All light sources are 60x100 cm in size, are located on shelves with wall tires from the building belt:



Their advantages: low price and prompt installation at any height.

I took tires 2 meters long, thereby getting four boxes 1x1x0.6 meters. The total area of ​​the illuminated surface was 2.4 m². For Count de la Fer, this, of course, is not enough, but for the experiment it is quite enough.

Suspended walls were made from thin fiberboard and mirror film, designed to return the prodigal photons back. For “for which it is repaired, it must be swallowed”:





A view with closed walls: In



total, it turned out to create a system of punitive psychiatry for growing seedlings suitable for the purposes of the experiment under the control of the great helmsman. All types of light sources are in equal conditions and consume an equal amount of energy.

As probands, tomatoes were chosen as heat-loving and capricious plants with a pronounced taste of fruits.

As it turned out, the best conditions for the initial development of seedlings were created in boxes with electroluminescent lamps. It is not for nothing that technologists are in no hurry to switch from electroluminescent lamps to LEDs at many Chinese mega-greenhouses. The LEDs in my experiment showed nothing special, except for the simplicity and lightness of the design of the lamp. Slightly grown seedlings developed well under the LEDs, but the control group under electroluminescent lamps gave a greater increase in green mass and the number of ovaries.

And finally, we turn to metal-halide lamps. Under them, tomatoes not only grow, but also bear fruit.



Ripe tomatoes have a taste and aroma.



The solar spectrum rules, dear comrades.

Metal halide is at the bottom left, LEDs are at the bottom right, two boxes with electroluminescent lamps are on top:



Now, on April 15, 2020, some of the grown plants have been planted in open ground. It is possible that low night temperatures can kill them. But this is also part of the experiment. The world is cruel.



The result of the experiment: electroluminescent lamps - the undisputed leader for seedlings. Metal halide is excellent for the later stage of plant development. LEDs - no advantages justifying the high price. Many will say that they would take a branded lamp, everything would be different. I will answer: one such lamp would cost like all other equipment plus electricity for three months.

Boring you self-isolation, dear coplanters!