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Performance

Page history last edited by pinkhamc@... 4 years, 9 months ago

Table of Contents (Items Covered on This Page)

HOW DOES THE WoW WORK SO WELL?

DOESN'T THE WATER FREEZE?

IMPORTANT PROPERTIES OF WATER

SHOULD I COVER THE WoW IF FROST THREATENS?

PERFORMANCE OF THE WoW OVER SEVERAL DAYS

CAN YOU BEAT THIS?

 

HOW DOES THE WoW WORK SO WELL?

The ability of the WoW to protect your plant is remarkable. The tepee WoW has protected tomatoes to -3°F; the open WoW to 16° F. Thus if air temperature were the limiting factor, plants could be put into the ,ground even before 8 weeks prior to the ALF date (see "Wallo’Water USE CHART'' for explanation of ALF

date).   However, with the Wallo’Water, soil temperature becomes the limiting factor. That's why it's necessary to warm the soil with the tepee WoW for a

week or so before transplanting into the WoW. In places where the frost line goes below 12 inches or so, it is best to warm the soil for up to two weeks (see "WARMING THE SOIL").

 

During the 4 weeks in the tepee WoW, the plant won't grow a great deal. In part this is because it is getting over transplant shock and in part this is because it is spending its energy developing it's root system.

 

Once you open your WoW, with a healthy root system and summer-like temperatures inside, the plant will grow rapidly.    Figure 1 gives a diagrammatic summary of the above

                 9-7 weeks before normal:                   8-4 weeks before normal:      1 month before­ - 1 month after normal:           4-7 weeks after normal:

                            WARM SOIL                                  DEVELOP ROOTS                           RAPID GROWTH                                     BEGIN HARVEST

 

Figure 1. General Use Schedule for the Wallo'Water. "Normal" refers to normal planting time (when you could safely put out an unprotected tomato plant).

 

DOESN'T THE WATER FREEZE?

Yes, the water freezes. If it's cold enough long enough it will freeze solid. Generally, this question is prompted by one of two concerns:

1) What does freezing do to the plastic? Nothing. It stretches enough to accommodate the expansion of ice.

2) What does freezing do to the plant? A lot, but all good! When water freezes, it gives off a slug of heat (see "IMPORTANT PROPERTIES OF WATER"). When the water in the WoW freezes, it gives off the heat equivalent of almost a cup of fuel oil.

 

IMPORTANT PROPERTIES OF WATER

Water does a number of important things in the Wallo’Water. Two of them are called the "specific heat of water" and the "latent heat of water."

 

The specific heat of water is its ability to capture heat from the sun (or other energy sources) and release that heat when it cools. Technically, the amount of heat is described as one calorie of heat lost from each gram of water per degree Celsius of cooling down to O°C. What does this mean in simple language? There are 3 gallons of water in an open Wallo’Water. Assuming the water temperature was 65° F on a day when the air temperature was 50° F and the temperature fell to 32°F, by the time the temperature had fallen to 32°F, it would have given off over 200,000 calories of heat which is the amount of energy you get from burning about one fifth a cup of fuel oil.

 

Next assume the ambient temperature drops to 18°F over the night. Now the latent heat of fusion takes over. In order for 1 gram of water to go from 0°C (32°F) liquid to 0°C ice, it has to give up 80 calories. Although it may sound a little strange, think of it this way: How could it freeze if it didn't give up heat? Now, by the time the 3 gallons of water have frozen solid, it has given up almost 900,000 calories of heat or the equivalent of burning almost a cup of fuel oil! In other words, the water takes the frost instead of the plant. Another way to think of it is that you have a furnace around your plant thermostatted at 32°F and the furnace is refueled every day by the sun! Incidentally, this "refueling" takes place even on cloudy days.

 

Some of our users wonder if the WoW acts as an insulator. One-and-one half inches of ice has an R-value of about 3. Since it freezes from the outside in, the outer layer does provide some insulation. But it is primarily the latent heat of water which makes the WoW work so well. (See PERFORMANCE OF THE WoW OVER SEVERAL DAYS).

 

SHOULD I COVER THE WoW IF FROST THREATENS?

We recommend that you never cover the open WOW. First of all, it's not needed to protect the plant (see "WHAT IF WE GET A FREAK LATE FROST?") and secondly, if you forget to uncover it in the morning, you run the risk of either interfering with the sun's recharging the WoW (melting the ice) or cooking the plant because the trapped heat from the sun can't escape.

 

PERFORMANCE OF THE WoW OVER SEVERAL DAYS

Although knowing the minimum temperatures to which the tepee and open WoWs will protect is important, it does not tell the whole story. If the temperature hovers around 20°F for the whole night and then falls to 15° F before dawn because of loss of cloud cover, you would expect the tepee WoW to protect your plant based upon our earlier claims. But what if the temperature is well below 20°F for the entire night? Will the tepee WoW still protect your plant?

Chart 1 shows actual continuous temperature readings taken over several days from the tepee WoW and Chart 2 shows similar readings taken from the open

WoW.

 

Chart 1. Performance of the Tepee Wallo'Water Over Several Days

 

A number of interesting aspects of the performance of the WoW can be noted. Chart 1 reveals that the tepee WoW will protect your plant even when the ambient temperature only briefly rises above 32°F each day for several days. Not only does it protect, but it also provides warm daytime temperatures. It is only when the ambient temperature falls below 10°F for several hours, that the WoW fails. It also demonstrates the characteristic stabilization of the internal temperature at 32°F as the water freezes and gives off its latent heat. It should be noted that cold-sensitive plants can tolerate temperatures slightly below freezing.

 

Chart 2.  Performance of the Open Wallo'Water Over Several Days

 

Chart 2 reveals that the open WoW protects even when the ambient temperature falls well below 32°F for 15 hours. It further confirms the stabilization of the internal temperature at 32°F due to the latent heat of water.

 

CAN YOU BEAT THIS?

On April 28th, 1984, Minot, ND experienced the worst blizzard in 60 years, with over 2 1/2 feet of snow falling in 24 hours. One user dug down to his WoW, found the tomato plant thriving, covered the WoW back up and in late May took a picture of the thriving, 2 1/2-foot-high plant.

Jim Bennett, the "Weekend Gardener" on Nationally syndicated TV, was eager to give the WoW a try. He poured boiling water on the ground (what an interesting way to warm up the soil!), planted six tomato plants and put tepee WoWs around them. That night the temperature fell to -3° F. The next day it never rose above 32°F [1]. The following night it was in the low 20's and the next day it finally warmed up. Expecting he'd have to replace all six plants, Jim was amazed to find four of them still alive and well. 


[1] When ambient daytime temperatures are below 32° F, we know from our experiments (See PERFORMANCE OF THE WoW OVER SEVERAL DAYS) that daytime temperatures inside the tepee WoW get into the high 30's to high 40's because of the greenhouse effect.

 

Return to WalloWater Page.

 

Return to Mentiscopia.

 

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