Solar hot water - Aquaponics - interesting consistency

I've only put half the measures I have in mind to put, but it seems I'm winning.

I planed on trying a few different things in an attempt to stabilise my grow house temperatures. One was adding thermal mass, another was shifting heat from the top where it was hottest, to the bottom where my thermal mass is, and where it is coolest.

So far I've added around 45L of water as additional thermal mass, and have a coil of black 4mm poly pipe at head height (mine not yours), with water flowing through and into the fish tank, gathering some heat as it does. I also have a 12 volt computer cooling fan blowing some air down from the top.

I turn the fan off at night so it isn't blowing cold air around, and stop the flow of water through the coil of polly pipe, so it doesn't act as a fishtank cooler at night. I'll figure out some what to control both of these automatically at some stage.

This morning was my first real test of the hothouse in the last week, as its the first cold rainy, overcast, and generally wintery day. The last few days have all been sunny even when they have been cold.

The fish tank temperature, and the grow house air temperature were both 17c this morning, and gradually lost heat over the day. It's sundown, and they fish tank and air temp are both 16c.

That's an amazing result as far as I can tell. Even though the world was trying to cool the system, it did quite a good job of hanging on to whatever gains it had saved from past days.

I think this is going to work.

I hope we get a few miserable days in a row so I can see how long it's heat reserves last.

Solar hot water - Aquaponics - Thermal mass

One thing I'd like to do is to stabilise my grow house's climate.

Another is to make it warmer throughout winter.

It seems to be getting warmer, but the fish tank water temperature moves around a lot. So I seem to be making some solar hot water, but I am loosing too much heat overnight. Insulating my grow house is too much like hard work, but...

high tech water based heat sinks

I have a plan.

Actually I have two plans.

The first is to add thermal mass to the system. I'm going to move more water into the system. Water has the ability to store more heat than stuff like concrete, and a huge amount more heat than stuff like air. This increases the heat storage capacity of my hothouse and should allow me to "bank" some heat. Water is really cheap. Solar heat is even cheaper.




Heat radiates from where ever it is , to wherever it isn't. If I create less places where it isn't, there will be less places for it to radiate to. Creating less places where it isn't also means creating more places where it is.

That should work.

In other words...

If I add some stuff that holds a lot of heat, and add as much of it as I can I should be able to store some of the excess during the day when it is plentiful, and have that release into the system overnight.

Heat likes to share itself around evenly in a very generous manner, so all I have to do is put something in its way that holds a lot of it, and the storage bit should take care of itself. This is the kind of stuff you would learn if you were to study passive solar design, and renovate your house a bit, so lots of people have done lots of work on the subject.

This will mean the fish tank water should heat up more slowly, and cool down more slowly. That sounds like a definition of temperature stability.

There is only a finite amount of heat entering the system each day. This means that if I add a material that absorbs some heat, it must take that heat from somewhere else. What that means is that by storing some heat in my new thermal mass, I effectively cool my grow house a bit from its crazy afternoon temperatures. This means I will not only be storing some heat for the colder times, but I'll also be knocking off the sharp bits of my graph at the top as well, and cooling it a bit during the hottest part of the day. As the day cools down, my thermal mass will reverse it's attitude, and share its excess heat with the now cooler air within the grow house. It should also share its heat with the fish tank, and give my fishy friends a more stable environment.

Everybody wins.

Except the supermarket, and fish monger.

Does a fishmonger "mong" fish?

wiktionary seems to think so. It starts it's definition with "a mixture, a crowd"

So I'm saying yes. I'm defining "mong" as "to gather a stack of things for sale or for general craziness"

Anyway, I plan on doing this in three different ways.

First, I plan on adding water based heat sinks. I can add a stack of them around the base of my grow house where they wont get in the way, and wont take up any growing real estate. I should be able to add an additional 15L or so of water to my grow house. This should increase the total thermal mass of the system and allow it to store more heat.

Second, I plan on running a heat pump in the form of a solar heat conduction coil in the highest part of the grow house where it's hottest, and pump that heat down to the bottom where it's coldest, and where all my water based heat sinks will be.

The third will be for another post because I'm yet to know much about it.

My high tech water based heat sinks will be recycled, plastic, three litre milk bottles full of water.

My high tech solar heat conduction heat pump will be a 10 metre coil of 4mm black poly pipe stuck up high.

That should work.

Solar hot water - Aquaponics - grow house min max graph

I've been taking some regular notice of the minimum and maximum temperatures of the water in the fish tank since I put it under a grow house.

I made a graph.

I like graphs.

It looks like this....

The red line on top indicates the maximum, the blue line on the bottom, the minimum, and the yellow line in the middle is largely meaningless.

But it does sit in the middle of the other two.

Which is nice.

There is also a thin red trend line and a thin blue trend line which clearly show that my grow house will be hotter than the sun within only a few years, if the trend continues.

I don't think the trend is going to continue.

But it does seem to be stabilising a bit. That could be an illusion due to unseasonable fine weather. It could also be that my concrete has warmed up a bit and is now supplying some heat during the night.

I really have no idea.

I just thought you might like to see my graph.

It will make a bit more sense once I have some more data. After a few weeks, I should be able to make some kind of statement about what it has achieved. I should also be able to do another comparison to the graph I did earlier of a day in the hot house.

I figure, if I pick a similar day, I should be able to read some meaning into a second set of stats, even where there is no meaning.

Poor quality science can do that.

Solar hot water - Aquaponics - NFT worm

[Edit from the future - there is some additional material on NFT ]

That previous post was meant to go out 2 days ago, but I saved it as a draft instead of publishing it.

That sums up my life at the moment.

I'm in draft mode. I found one of my fish dead, on the concrete yeaterday. I'll post about it when I know a bit more about it.

But I did take the time to check the water level in my NFT test, and discovered that not only was the water very hot, but there was a worm in it.

My worm looks like he's all broken and sore, but when I gently teased him out, it tuns out he was faking.

Perhaps he's in labour.

I've always thought that those large, white, thicker sections on a worm indicated the presence of an egg. (seen here on the left in pink)

One of the dangers in always thinking something, is that it might not be true. With anything you have known all your life, there is a fair chance your older brother was the source of the information at the worm wise age of five and a half.

I'll look into it, and if it turns out it's important, I'll let you know.

But the reason this post is in solar hot water, is than on a 17c day, I'm finding my water in the NFT tube, within the grow house, is 36c. I'm pretty sure worms don't like 36c so I moved him back into the main system. There is also the danger that something like a worm could block the plumbing and cause an overflow.

I'm guessing that's a little hot for strawberry plants as well, although they seem content enough.

That's not bad from a heat collecting position though, even if it isn't so good for a strawberry or worms position.

The strange thing is, I'm collecting all this heat from a white PVC tube, that I thought would be one of the cooler sections of my grow house. It's making me rethink the way I might go about collecting some heat to make a solar hot water heater.

The other strange thing is that the air temperature in the hothouse is 29c.

I think I might have a hot house within a hothouse situation going here.

If so it might be very easy to concentrate some pretty hight temperatures, making storage of the heat a lot more compact.

Solar hot water - Aquaponics - a day in the hot house graph

This graph really speaks for itself, but I like the sound of my own typing, so I'll be adding a bit as usual.

This graph represents my attempt to do something every hour, on the hour. If you click on it, it should open up to slightly bigger version that might be a bit more readable.

If you read all the times off the top line, you'll see I'm not so good at doing stuff to a schedule.

There was also a big chunk that should have extended out to the right for another 8 hours or so, but I went to sleep. Not a lot would have happened overnight. There have been some times where I have taken readings in the middle of the night, and the readings fit within a gradual decline over night to a point where they would roughly meet up with the 8am start data. I would expect the changes to be quite straight forward and gradual as the system radiated heat.

The cells with the yellow background represent daylight. Actual daylight at this time of year is from roughly 6:30am to 6:00pm. Roughly.

The solar heater output (graphed in yellow) comes about, as a result of a 10 metre length of 4mm black poly pipe, that I have coiled, and parked near the roof. It siphons a small trickle of water from the tap input to the glass house, up through the coil, then down to the fish tank. As far as I can see, I could just add a few more to shift any amount of heat I desire down into the fish tank, or storage, to be released slowly at night. Obviously there is a limit, but that limit comes down to how hot I want the air to be. I don't really know how hot a hot house should be, so I guess that's the next thing I need to study. It's one thing to decide to work on temperature stability, but I have a feeling I might be better off knowing the temperature I'm seeking to stay stable at.

It's interesting to note how wobbly the temperatures are outside, as compared to inside. Its also interesting to note that they seem to be getting even more stable over time.

Given I'm aiming for temperature stability, that's a good thing. I might not have to do as much as I thought. I might just have to sit down for a bit and wait.

I'm not very good at waiting, but I consider myself an expert at sitting down.

On this day, the hot house didn't see full sun until 3 hours before sunset, but when it has seen sun as soon as It could, it behaved by just being a bit hotter all round.

Sitting in a hot house is very, very nice.

Aquaponics - Hot house temperature

I've always wanted my own mini-planet, or at least some sea monkeys.

The planet I found in my black soldier fly picture looks a lot like earth, and even conveniently has the equator drawn on.

I think the equator might be the power line from my house to my shed. And Europe is a tree.

But it's still convenient, and there may well be something like sea monkeys living within its watery boundaries.


And while we find ourselves on the subject of black soldier flies. What is a fly doing carrying around, what looks like, a Venus Fly Trap on its back? Goth? Emo? Is it trying to make some kind of political statement?

But this post is about my hot house and other than that photo coming from the inside of said house hot, it has little to do with anything.

My hothouse seem to be working really well. At the very least it's a really nice place to sit when its cold, but sunny. As a result I'm spending way too much time sitting. But it's very nice.

The hot house regularly gets to a tropical 33c in a wintery 12c day, and takes most of the day to bring the fish tank temperature up from an overnight 10c -12c to around 16c - 18c. 16c is when silver perch seem to spring back into life, and so have been feeding with their old summer time vigour. Today actually had an overnight low of 14c in the fish tank, and an afternoon high of 20.

I've had some discussion with people who know such stuff, and I'm told there might be some stress for the fish with such large temperature swings, but I just realised that prior to the glass house, I saw 4c - 8c overnight lows, rising to 10c - 14c in the late afternoon. That's the same size swing, but starting from a perhaps stressfully low 4c, so who knows, but it does seem like it gains 6 degrees max.

The fish don't seem to be showing signs of stress, and are feeding a lot more. But given I like solving problems, I'll just treat this as a problem, even though I'm not sure if it is. Most of these kinds of solutions prove to be useful to someone, somewhere, so even if its not an issue for me, stabilising temperatures could well help someone else. Stable temperatures will no doubt make my fishies even happier.

So that's my new problem, temperature stabilisation within an aquaponics environment.

Wish me luck.

Solar hot water - Solar collector

A foam box with a sheet of glass on top should make a pretty good solar collector. It is well insulated and the glass should stop any captured heat from escaping. If it's painted matt black inside it should work even better.

To have something to compare our results with I have a second identical foam box. I've placed a thermometer in each, but I've placed the digital readout next to the other thermometer so I can see them both at the same time when I take a photo. The box on the right has the digital temperature probe in a similar position to the other box's thermometer. The box on the right also has some black plastic in it and is covered by glass.

To make sure both thermometers were working and showing the same temperature I put them in the same box for a while.

Both thermometers showed 22 - 23 C in the same box after sitting in the sun for around 20 minutes.

 It was 20.8 in the shade according to a third thermometer. I have a lot of thermometers. 

This was the amazing result after 36 minutes!

+ 45 C in 36 minutes!

I knew there would be an effect but I had no idea it would be as big as this.

Did I mention it only took 36 minutes!

And 68 deg C! That's slow cooker temperature! Is that slow cooker temperature? Yes* it is! And on a 20 degree day! In only 36 minutes! I wish I had some aquaponics produce. I want to make some laksa! 

* from Wikipedia RE: food safety ...

HACCP guidelines

Main article: Hazard Analysis and Critical Control Points

The UK Food Standards Agency publishes recommendations as part of its Hazard Analysis and Critical Control Points (HACCP) programme. The relevant guidelines at http://www.food.gov.uk/multimedia/pdfs/csctcooking.pdf state that:

"Cooking food until the CORE TEMPERATURE is 75 °C or above will ensure that harmful bacteria are destroyed.
However, lower cooking temperatures are acceptable provided that the CORE TEMPERATURE is maintained for a specified period of time as follows :

• 60 °C for a minimum of 45 minutes
• 65 °C for a minimum of 10 minutes
• 70 °C for a minimum of 2 minutes"

Previous guidance from a leaflet produced by the UK Department Of Health “Handling Cooked Meats Safely A Ten Point Plan” also allowed for:

• "75 °C for a minimum of 30 seconds
• 80 °C for a minimum of 6 seconds"