Solar floor heating again (part 2)

After some interesting delays created by life involvement (and not least frustrating injuries) I've now just about completed this project and its in what I'll call the tuning phase. Back in this post (part 1, so yes 4 yeas ago) I showed the laying of the pipes (and man wasn't that some hard work) and discussed the insulation and its role in making this effective.

This has a critical role in the success of the system because it confines the heat in the pipes to be all released into the floor above the insulation (and not just carried away by the breeze or radiated into the ground. Recalling from that above mentioned post this is a sample of how I run the pipes under the floor:

and now the insulation holds that heat in as well as drastically reduces any losses from the house through the floor too. This last point is not insignificant.

So to recap the design idea, water is circulated through the (four) floor circuits (each of the above pairs of pipes flows in opposite directions, see the previous article) and out into the yard where it flows through a pipe in the sun to get warmed then back into the floor. This is done with what I call the junction box where water being circulated through the floor goes back into the junction box and meets the water being circulated through the yard in the sun. Because its a syphon arrangement (again, see the previous articles) the requirement for pump "head" is not significant and flow rate is the issue.

So lets have a look at those components. 

Junction Box showing flor circuits and outside circulation (on the left)

the pumps:

and you may have noticed in the above shot over on the left a small black thing, which is this:

A 1000W aquarium heater (themo regulated) which I'll go into later.

How it works:

Basically the design is to take heat that exists outside of the house during the day (especially when the sun is shining) and pump that through the insulation and into the house. Especially in this environment the insulation plays a critical role because if the heat losses are higher than the heat inputs then there will be no effective gain. 

Lets look at those gains, this is a picture of my 3 channel temperature recording station; the three channels are:
RED = inside the house 
GREEN = under the floor (outside the house) and 
BLUE = outside temperature (away from the house).

You can see that inside varies wildly because I heat the house in the day and then turn off the heating when I go to bed (to save money among other reasons) and begin heating in the morning.  The green line in these pictures closely tracks the outside temperature (and you'd be right in guessing my floors are cold underfoot!) which turns out to be an interesting metric (which I'll get to next)

This identifies my goal: to flatten that inside temperature curve and with less expense.

This above image is a snapshot of the 72 hours preceding my placing most of the insulation in the floor (the spike is me handling the thermometer and repositioning it so that that it wasn't trapped between the insulation and the floor forever). Note date's and times in the images.

Quite an impressive result immediately and shows clearly how much heat was radiating out of the house through the floor and out into the world (now trapped by the insulation layer under the floor)... wow.

Indeed this next image shows how now the floor tracks the inside of the house not the outside anymore (note the timebase change on the X axis to zoom in more on the 12 hour period).

again, wow.

The next phase was to then plumb up and turn on the floor heating pumps to transfer energy inside the next day and see what's happened to the floor temperature and test the system (oh, and btw, by this point the floor insulation is not 100% complete, more like 70%)

so above you can see how the house is dragged up now with the warmth of the day, and the floor heating, where I lit the fire (wood burning stove heating which explains why above I mention I don't heat at night after I go to bed), how that as the fire went out the temperature of the house fell down to the floor level and stayed on track until eventually (after this time stamp of 6:55am) the sun came up and things rose again.

Because this is an experiment in progress (still learning about how to tune this in this environment) I ran a few scenarios lets look at the outcomes from them.

Scenario 1 = increase the Junction box (water tank) temperature with the heater to put in (up to) 1000W of energy (as determined by the heater system) by setting the thermostat to 20C and continuing to run the floor pumps all night. Note: some heating with AC during the day and a fire at night. Note 2 we don't have a plot of the water temperature here.

Scenario 2 = passive heating only inside (red curve) but running the floor pumps (note: I am continuing to fit out the floor insulation during this)

Scenario 3 = fully passive with no additional energy added except solar through the heat pump, no aquarium heater (more of the insulation  fitted, nearing 100%).

Discussion

The basic tenet of my process has been to harvest energy when its there, and store it for when it goes away. This is basically energy from the Sun (and when its all said and done what isn't {ans Nuclear}). I havest this in two ways:

1. capturing heat from the sun and shoving it into my house as thermal mass and using insulation to reduce the losses (think water in a bucket instead of just held in your cupped hands)
2. using the outside heat to make reverse cycle AC more efficient (it works on the temperature differential you are facing; there is a hot side and a cold side. The warmer the cold side is the hotter it makes the hot side, the reverse is also true) and thus use less energy

The insulation (also put into the ceiling late last year) massively reduced the losses at night (convection within the room as hot air rose to heat the ceiling and shed it fast without the insulation and radiation losses too) and now this insulation on the floor reduces the losses through the floor from radiation too as well as enabling me to capture the 1000W of heat available per square meter in the sunshine.

I have now cut my wood and energy needs to heat in winter by 75% and have a warmer and more consistently warm house to boot.

Not bad if you ask me ... 

Costs?

The entire costs (ceiling insulation, floor insulation, pipes, pumps and fittings) has been under AU$1500. 

I chose polystyrene because it has both a better R-Value than the messy and horrible mineral glass wool, and unlike that product does not lose its insulation property over the years NOR does it breakdown into a filthy difficult mess in 15 years time; and bonus points for it not being enjoyed by rats or other pests (who love to nest in your ceiling insulation).

Win Win