Backyard Aquaponics
A place to discuss aquaponics

Is that due to the greenhouse loosing a lot of heat when you had a leak or do you think you'd have the same problem even without the leak (and it's more related to lack of sun)?

Hello Zsazsa!

Just minutes ago I was silently cleaning my onions (a couple of crates actually) and was "brainstorming" about your setup and plants. And loo and behold, you posted an update! :-)

As for the plants I remember an article in one of our gardening newspapers from this spring. In that article some growers were asked questions about the last winter (2010/2011) weather and how their growing operations fared. The consensus was it was a terrible winter regarding sunshine. There was not enough light for weeks and it hindered the growth of most plants.
For producing in winter there are shade tolerant plants. And not only light intensity matters but photoperiodicity (length of daylight) plays a role as well. "Light eaters" -like tomato, peppers, aubergines, cucumber, melons, squash, etc.- that require high light intensity is hard to grow in winter. Brassicas (cabbage-type plants) are less demanding regarding light and temperature. Some (like chinese kale, pak-choi, or what) even likes the shorter daylights of these winter days because if it was longer (the daylight) they would just bolt, produce flowers and shrivel.

Yes, I know, it is not much help now, but maybe, you could try to sow a few seeds of these "winter type" veggies (there are varieties for growers selected especially for winter growing: short season (=fast growing), low temperature types!) Retek (sorry folks, i can't recall its English name) might also be a good choice for short daylight conditions.

By the way, could you post your temperature data for the last couple of days? In and out, water, maybe humidity if you can measure it, something like that?

Keeping the air moving with a fan if you aren't already doing this will really help with reducing condensation and drips onto the plants but probably won't be enough by itself.

Anything that helps de-humidify the air, like covering the tanks or using a dehumidifier.

Vent some of the humid greenhouse air (Get the hot air up near the ceiling if you can) and bring in some cold dry outside air during the sunny part of the day so it has time to warm up before nightime.

Adding heat helps but can be expensive.

Adding a layer of plastic inside your greenhouse in front of the glazing might help but will reduce the light coming in. This adds a layer or air which is warmer than the outside air.

I've been wondering about the tank water and evaporation versus condensation and temperature. Like, if the air temp is always lower than the water temp then water would be evaporating mostly. If water temp is lower than air temp then water should be condensing out of the air into the tank then. So, I wonder if making the air temp always higher than the water temp, maybe by just a little would help to control humidity in the enclosure.

Other ideas would be air exchange with the outside but through an air to air heat exchanger, condensing humidity out of the greenhouse air on the way out, draining back into the tank maybe. I guess they are called recuperators:
http://en.wikipedia.org/wiki/Recuperator

Thy for all the replies, branstorming helps. Im gonna add some more details just as I can recall tham:

- The leak is patched, it has minimum effect.

- I wont heat. Thats against the concept, and energy efficiency.

- Recuperators, I know desinged one for the house, but ist way too expensive for the GH.

- All about the cold and shade tolerant plants are true, I should have plant those, earlier but please remember this is a test. Noone has experience with a passie solar GH&aquaponics in continental climate (or is hiding perfectly) I only have guesses about how the system will handle the forecoming times. (As time goes by I get better in guessing thats called experience.) So right now its very hard to be prepaired with the right plants, in the right time. For example: The tomatoes that did a great job in september are now turnig yellow. It could be the cold or the dark or both. Meanwhile the other tomatoes that produced less and I didnt favour them are still green and doing fine. I have plenty radish (retek) and salads, I planted some cabages, beetroot, spinach, sorel. Also some herdb like the climate others dont. Looks like some my tomatoes will die and than I need stg to replace them. One of my fear against trout was that they are twisted in means of temperature. Imean that they are still eating fine in 8-10C while the plants and bacteria are slowed down. I thought this could cause some problem, it could be resolved with the planting the right greens, but thats not whats happened...

- Moving the air with a fan. Again more energy is used for some effect, may be it worth a try.

- Ventillation in the right time of the day, yould be a solution. The arduino has all the data and possibilities to open and close the window in the right time of the day. This one is an othet worth a try, but needs some investment again.

- On air temp vs water temp. Thats not the ponit. The ponit is that the air temp is alternating. The water likes ot evaporate, so its always trying to get around 100% humidity. Tha amount of water in the air is proportianla with the air temp. So the air is hot, is gets water, than it cools down, so water is precipitated cause the air cant hold it. I guess the hummidity is alway close to 100%, as I always see vapor condensation.

- If the sun is shining, condensation is on the thermal mass (thats the coldest spot)
- If its no sun or night condensation is on the glazing and on the walls (the coldest spot again)

And this is the point when I realized that covering the tanks wont help by it self. As the hummidity will still get out and the vapor would be all around, soon the wet surface will be almost as big, as befor the covering. The vapor supply is probably almost the same.

Ventillation is a byfar the best option. A daily few minutes of full ventilation would do the job.


Any better ideas.

Hello,

When is the right time to open the window for an air-exchange if we want drying?

It is when the air outside is colder than inside!

Otherwise the introduced warmer air will cool down say 10 celsius while the heat mass in the drums would warm up say 0.1 celsius (rough calculation, but heat capacity and mass of water is much bigger than that of the air). As the air cools RH goes up to 100% and then condensation occurs.

On the other hand if you let colder air in then it would warm up, RH would go down and there is some drying. Unfortunately the price of this drying is paid by heat, which is lost in the process.

And now comes the fun part:
If you don't want to heat the house then the condensation has something to offer you though: it protects you from frost!!!

Think of it this way: until there is 100%RH and condensation is ongoing the temperature of the air DOES NOT CHANGE! Condensation is just another form of phase-change like reversed evaporation and everyone knows that the temperature of the boiling water at see level is 100 celsius. And it stays there until there is the last drop of water in the pan!
When there is frost outside the condensing water vapor puffers the inside temperature! If there were no condensation then the daily temp fluctuation, the nighttime temperature drops would be more pronounced.

With no auxiliary heating the best thing you can do is let as high the temperature and as high the RH to climb as they can during daytime! Because on that same frosty night the condensation will actually heat your building...

Now try to be clever. Which of our fingers should we bite?

What do you mean by continental? Eastern Europe, or just in the middle of a continent? If the latter, I've repeatedly posted information about a book written about an almost identical greenhouse built here in Minnesota (damn cold winters, far from any large bodies of water). It includes lists of things like good varieties of plants to grow through cool, low-light winters and such.

http://www.gardengoddessenterprises.com/

Karen@ I have checked the Garden Goddness system, I found tham because you posted it repeatedly

The two building may look similar from outside, there are some huge differences.

I have thermal mass barrels, while they are heating the ground bellow with air ventilation through pipes (Similar to Rob's geodome http://www.backyardaquaponics.com/forum/viewtopic.php?f=18&t=8898 project.)

I have an aquaponics system inside while they have a dirt garden. The water surface, and hummidity is quite different.

They even have heating inside as well, see the gas heater on the wall.


They stop the production in the summer to sterilize the system. Thats because hummidity inside their pipe system.

The amonunt of vapor in winter is quite different, I'm respecting their experiences but they dont really answer my problems.


Pumukli@

If the outside air was warmer then the inside, the hole GH would make no sense.


This is only true if you assume high RH for the incoming air. The hummidity to temp diagram is exponential.

true! The heat loss is way over-estimated because: Volumetric heat capacity air: 0.001297 water:4.2160 (data from: http://en.wikipedia.org/wiki/Heat_capacity )



If this would be true, the only thing would be needed to run a greenhouse in alaska is sparying water, keep RH on 100% non stop...

Brain dump here:

If I were going to exchange air with the outside in Winter I would definitely use a heat exchanger to not lose heat. They don't have to be expensive, just some corrugated plastic or metal in alternating horizontal and vertical layers in a box with maybe computer fans to blow the air. Drains to collect the condensation.

It seems you definitely want to condense pro-actively in the evening, getting the humidity out of the air to where you want (in the system) before it gets out of hand on your glazing or walls or barrels. I'm thinking a fan aimed at the FT water surface would get some out when the air is warmer than the water.

In my cold frame (so far) it seems that the condensation on the walls is changing from one day to the next. Right now there isn't much at all after a cloudy day, probably because the temps match more closely inside to outside. Probably the worst would be a sunny day followed by a cold night (clear sky). In that case get the air temp as close to the glazing temp as you can when the night starts, condensing as much out of the air into the FT as you can rather than letting the glazing condense it?

You could make an air chiller with a fan through it using a thermoelectric chip (I have a tiny battery operated refrigerator that uses these), run air past the chip to condense excess humidity out when the night begins?

Maybe cover over the FT and do the beds constant flood during the night (not sure if you're flood and drain) to reduce evaporation during the night.

It sounds like any heat gained in the air should go into the water to keep the humidity down, but then if the water is warmed then evaporation will increase.

An other great idea just popped up, thx Dave!



A plan is forming:

1. Covering the FT and the Sump.

2. Yes, Im FD, but I can pull the siphons and go CF in no time, and this reduces water-air contact area. I go even one step furter -> What is I cover the GB-s with a layer of hay? This wont harm the greens and could make an other barrier for humidity. Would that work?

I'll put a plastic foil on a non two used GB areas, to see how much hummidity is collected. One is gona be FD the other is CF. Lets see whats happen!

Quote:
This is only true if you assume high RH for the incoming air. The hummidity to temp diagram is exponential.

I know the diagram, I was referring to the current weather conditions in the country. Cold and wet, fairly humid air in the past few weeks. (It causes problem for my onions too, it is very hard to clean them in this humid environment because their outer dry leaves just don't want to easily separate from the bulb, they are almost sticky!)

Quote:
true! The heat loss is way over-estimated because: Volumetric heat capacity air: 0.001297 water:4.2160 (data from: http://en.wikipedia.org/wiki/Heat_capacity )
Yes, it was intentionally a factor of 100 in the example. Though you should take into consideration the "evaporation heat" of water too. Btw. the heat capacity of 1m3 air is 1.29 kj/m3K, while it is 4.2 kj/kgK for 1 LITRE of water. If you have say 1000 litres of water then it would be in "balance" with cc. 3000 cubic meter of air.
But it is a theoretical thing anyway.

Quote:
If this would be true, the only thing would be needed to run a greenhouse in alaska is sparying water, keep RH on 100% non stop...

You can protect plants from frost by spraying water on them. It is a well-known practice and is used in high value orchards (apricots, peaches, etc) when there is a danger of spring frost... Of course you can't keep an orchard flooded and your pump (and tubing, and sprinklers) has limitations on the available heat, so you can't win against very low temps. But the method still works and can save your orchard on that very critical april-may night... Although you actually extract the "thawning heat" or "frosting heat" of water, not the evaporation-condensation heat this way.
Regardless, what I wrote is still true, condensing water vapor release heat, hence buffers against the cooling process.
On a cold night, when the air is humid, and the dew point is above 0 Celsius, you can be pretty sure your plants would survive the night without frost because the condensation of water vapor (dew) will protect them. It stops the cooling of air at the dew point temperature. On the other hand, if the air would be drier on that same night, and the dew point would be under 0 C, then you could be pretty sure you have to do something, because there is good chance your plants would be damaged by the frost. By the time condensation (dew deposition) would start, the temperature would be dippped into below zero territory...

Covering the beds with a (very thin) plastic is a good idea! You can basically make a "small growing house in a bigger room" arrangement. Then covering the sump and fish tanks would be good too. But then where is the "breathing surface" to provide air for the fish? When plants make O2 in daytime, then OK, but what happens at night, when the plants stop producing O2?

quick 2c from me, just remembered something. When i was visiting a farm in austria, a guy has constructed his food storage under ground, and he has prevented the condensation with two things:
1. his air intake was brought through an underground ducting(10m of ducting) at a slight angle(so that the condensation happening in the duct flowed down the the duct) and while he had his duct underground the air got heated a lil bit by the ground
2. his air exhaust was positioned at the highest point in the cellar


Covering your gb with hay doesn't sound good to me, as it would attract mold and u are still left with the plant transpiration which gives off most of the humidity in your system.
I tried indoor ventilation in my gh for lowering down the humidity, it helps a little, but it sure isn't the solution, the above actions seem like a way to go.


See ya!

Underground piping would surelly help but I dont feel like digging that much again...

I switched to CF today morning, Im starting a bussy day but tomorrow I'll have time to do the nylon covering...

data from (8:20am)
inside air temp: 8,5C
system water temp: 10,5C
outside temp: 6C

And we are looking for a bright sunshiny day!

Tools of a 21th century farmer: Laptop, voltmeter, hair drier, saniter silicon, pliers, knife

I finally had time to for things that are on the waiting list for some time now.


I repaired the datalogger as some of the digital voltometers where short-circuited. I have sealed tham with silicon, and now they work again perfectly.