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.

Wind energy - Blades

It turns out, there is a stack of energy in the wind. In fact the more I research, the more I see it that way. I'm starting to get some kind of grip on this energy stuff. I'll try to explain what I've understood so far.

Water pumping windmill

Just looking at the traditional windmill for now, (traditional to me) the one that looks like a fan, we see there are a stack of different blade shapes, and some seem to have more blades than others. Some seem to be always used for pumping water, and others seem to be always used for generating electricity. In keeping with 120 things in 20 years tradition, I'll start an explanation of wind energy by talking about cogs.

Connect two different sized gears together. Choose two cogs so that when the small one rotates 100 times, the large one rotates only once. Now give the gears some power by turning them. The same amount of power exists in the big and small gears, but in the small gear, its spread out over 100 turns. This means that you can slow it down by resting a feather on it. It has no grunt. Try the same feather trick with the large gear, and your large gear wont care a bit. 

If you put a set of wheels on the axle of the small gear you will zoom along until you get to a steep hill, or a feather.

If you put a set of wheels on the axle of the large gear, you will drive slowly through a pillow factory with ease.

Having just described this, for the first time in my life I suspect I might be leaning toward some vague understanding of "torque" that I didn't have when I started this post. I think torque might be rotational grunt, where power is what the engine has. If this is true, you can express an engine's power as more grunt or more speed while keeping the same power (the engine). That must be it. Or not. But for now, I'm sticking to "grunt", so now might be a good time to edit your dictionaries and engineering manuals.

A windmill's power comes from the wind. If the wind is fast we get more power. Now, picture a string of air 100 metres long. That's called a string of air. Now move it at 100 kph. That's called wind.

If we slice that 100 metre string of wind 100 times we get 1% of it's power in each slice.
If we slice that 100 metre string of wind 10 times we get 10% of its power in each slice.
That's simple enough.
If we have a 10 blade windmill, it makes 10 slices every time it does one revolution. That means it will make 10 revolutions as that 100 metre string of wind blows past.
If we have a 100 blade windmill, it will make 100 slices for each revolution. That means it will make one revolution as that 100 metre string of wind blows past.

The same amount of power is in that 100 metre string of wind, but we can harvest it in such a way that suits any combination of grunt and speed that we might need for our application.

The 10 blade windmill spins 10 times with stacks of speed, and the 100 blade windmill turns only once, but with more grunt.

It turns out that lifting water from a well requires lots of force, so we use windmills that have a lot of blades, and generating electricity requires a lot of speed, so we tend to use windmills with fewer blades in power generation.

A 100 metre string of air doesn't really get you 100 slices. Actually for all I know it might. But it probably doesn't. I made those numbers up to make the calculations easy to see, but it all works pretty much the way I described.

So anyway, that's the story of where babies come from.

Aquaponics - Glass bell siphon

It's been said before, even by me, that a picture paints a thousand words. So imagine how many words a short video paints.

I made a glass bell siphon in an attempt to discover what actually goes on in one as it starts to siphon. It involved taking a glass jar, and turning it upside down.

I think the key when building a siphon is to place a tap at some point on the hose coming from the pump to allow a small percent of the flow to be diverted. This allows you to increase or decrease the flow and makes making a siphon very easy. The most difficult thing to get right is to match the flow against the size  of the standpipe (the standpipe is the white PVC pipe the water drains out of the bucket through.

in this video...

• the siphon starts at around 00:20. Even though there is some flow before 20 seconds in, it doesn't really start properly until enough water is entering the standpipe to create the required suction)
• then stops at around 00:40. Note the rush of air in through the small hose within the jar and how quickly it stops the siphon. 
• then the cycle repeats. 

A bell siphon does that. It also generates a tide-like ebb and flow in the grow bed(s). This test siphon is in a small bucket, so the time it takes to flood and drain is only a few seconds. We could flood and drain as fast as this in aquaponics, but would then normally turn the pump off for up to an hour each cycle in order to let the plants breath for a bit. Alternatively we might use a smaller pump and run it all the time.

Solar hot water - Heat

There's really no such thing as cold.

Unlike politics, just because it can make you miserable, numb, or even dead, cold doesn't actually exist.
What you are feeling when you feel cold is actually heat moving away from you and toward something else. Things lose heat or gain heat but don't lose or gain cold. Heat is so generous that it simply wants to share itself evenly everywhere. Unfortunately for you, that means if you are warmer then the winter around you, all that generous warmth you make is going to try to spread out to everywhere else.

"My air-conditioner makes cold" I would sometimes hear myself say. "But it doesn't" I might reply. It turns out an air-conditioner is what is known as a heat pump. All it does is finds some heat and shifts it to somewhere else. In the case of cooling, it takes the heat out of your room, and throws it outside where it belongs. In the case of heating it grabs heat from outside and sticks it in your room. That bit is most amazing as far as I'm concerned. Its incredible to think that there is so much heat out there in chilly winter, that an air-conditioner or a solar hot water system can pick up great wads of the stuff and jam it into my house to make me warm.

Thanks science.

Another important and useful thing about heat is that it rises. That's because when stuff is hot the little stuff that stuff is made of move about a lot. This means the stuff expands a bit. When an amount of stuff is bigger than the same amount of the same stuff, it weighs less. Which is to say it displaces more of some other stuff. I'm glad we cleared that stuff up.

Hot stuff rises above its neighbouring less hot stuff. That means we can move heat for free. If hot air rises and we need to move it up, all we have to do is let it move there. If we need to move it up and to the side, all we need to do is put it in a pipe.