Category: Build Progress

 Today, under the glorious hot sun, we finished digging out the hole, for Energy Module Number 5. We then started on the smoothing and leveling process, with the insertion of the guide rails down each side, doing section by section.

When we reached the middle section, we discovered that the wall just didn’t want to stop “pouring” into our hole, the sand was a very large grain size mixed in with small gravel and it just simply kept falling down into our hole, no matter how much of it we removed!! This was the spot where the mini-digger was also struggling to make it way along the top to do the digging task and it kept slipping slightly sideways towards to the hole – very scary! So We had to shore up the side with a sheet of OSB and posts and it seems to be holding

Module-5-Flat-bottomed-hole-1

Anyway, we have finally finished removing all the excess sandy soil by hand and it is now all flat and level and ready for the next step of the insulation boards for underneath the bottom of the module.

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Tomorrow, it is sorting out the pile of the insulation panels to gather up about 60 to 70 pieces of 120mm thick boards plus an extra strip to fill down the middle. More will be revealed tomorrow – grin!

 Today, we started the major task of digging out the hole to receive our largest Energy Module we are assembling underneath our house. But first, we tidied up various bits and pieces like old concrete post with their  concrete footing still attached and moved them away. We need all the room we can get to store the sandy soil being excavated.

The hole we need, measures 10 metres long by 3.5 metres wide and the usual 1.2 metres deep, this amounts to over 40 cubic metres or well over 80 tons of the sandy stuff to move!

It was tricky to position the mini-digger in the various places and angles to do the job, firstly, cutting one long side to make it neat and tidy. We discovered that this patch of our ground, is rather made up of course sand particles and it was a fluffy nature and didn’t hold together too well, so we had some slippage in some spots around the edges.

Module-5-Mid-way-through-digging-hole

We loaded as much as we could against the wooden wall of the mountain of dirt we placed there last year, and we still had loads more to shift. We had to use our dumper truck to ferry a large amount away and dumped near our holly tree!!

By the end of the day, we managed to dig out pretty much all the material at last.

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Tomorrow, we will do the more accurate scraping of the bottom of the hole and start assembling a rather large number of insulation boards to form the bottom layer for the tank to sit on.

 Today, we carried on with the filling operation for our Energy Module Number 3. We had pulled most of the water out of the swimming lane and the meter reported that we got about 1900 liters from that source. We then switched over to ordinary mains water and did another 2500 litres before stopping for the night. Tomorrow, we will finish off the fill with another 2500 litres more to bring the total amount to about 8400 litres!

 This morning, we connected the conduit pipes and inspection tube down into the Number 4 Energy Module. Then we pushed in the remaining sand / soil from around the hole and covered it all up.

Module-4-Finished

Finally, we pegged out the red and white warning tape to enclose the area, to prevent accidental “driving” over the module!

 Today, we put on the insulation panels around the number 4 Energy Module. We inserted at least 300 mm thick of insulating boards, more like 350mm to 380mm thick!

Module-4-and-lots-around-the-outside

We did forget to drill down underneath the tank and insert our conduit pipe for the temperature probe so instead, we pushed it (the conduit) directly underneath the insulation layer so it will at least give us some idea of what the temperature is doing in the sandy soil underneath the module. Oh Well!

We then put on 300 mm to 350 mm thick layer on top to form the lid.

Module-4-and-heaps-on-top

Tomorrow, we will put in the two usual conduits for the water “high” and “low” fill points and the two temperature probes for those same points. Then we will push the final sandy soil around and on top of the module.

Also today, we started filling up the existing and completed Energy Modules (number 1 and Number 2) to make sure we don’t suffer from another incident of rainwater getting underneath our water tank and rising them up!

We poured about 3.5 tons of water into our 1st Energy Module (under Bedroom 3) which holds a maximum of 3.7 cubic metres (or 3700 litres) in capacity. Our meter went from a start reading of 200 liters (it is a brand new digital water meter!) and we stopped filling at 3727 liters!

The second tank, under bedroom 2, will need more like 4500 liters to fill it up mostly full. We started and got about 1900 liters in before we stopped work for the day. the rate of filling is only about 12 liters per minute so it will take a while to do the job. Phew!

Today, we dug out the bottom of the hole of the Number 4 Energy Module and inserted the two guide rails to scrape flat the bottom. We then washed the 12 Aquacell plastic crates we needed for this module. We also selected a heap of PU insulation boards and started lying them out on the bottom to form 4 layers, one of 100mm thick, followed by a 140mm thick layer and topped with two layers of 120mm thick foam boards, making a grand total of 480mm thickness of insulating barrier to keep as much heat in this energy module. PU foam is about 0.02 Watts per Celsius per metre thickness so with the thickness at nearly 500mm or 0.5 of a metre, then the U value of this particular part of the insulated bottom of the tank is approximately 0.04 Watts per degree Celsius per square metre of exposure. Now the square area of the bottom is 2metres by 1.5metres which makes 3 square metres so the total heat loss of the bottom portion is 3 times 0.04 (the U value) which is 0.12 Watts per degree Celsius. The maximum temperature we are likely to get in this energy module is about 80°C and so the temperature different between the hot water and the surrounding sandy soil would probably be about 70°C (hot water at 80°C and sandy soil about 10°C so the difference is 70°C). So we would be losing about 70 times 0.12 which equals 8.4 Watts. Another way to look at this heat loss is to change the word Watts into the SI units of Joules per second and there you have it! The hot water would be losing nearly 9 Joules every second all the time, until all the heat is gone! It is a little more complex than that (sigh!) but that is basically the calculation to work out what heat loss we would have to suffer when we have maximum heat storage. Don’t forget, this 9 Joules per second is ONLY for the bottom insulated layer – we have NOT calculated the 4 sides yet and the top too!!! Smile!

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Tomorrow, we will start assembling the plastic crates!

 This morning, we started on our “Number 4” Energy Module. It is our smallest one at “only” 2 meters by 1.5 meters for the water tank itself and the hole we dug is over 3 meters by 2.5 meters wide but it is 1.7 meters deep! We had some problems with slippage where one of the walls kept breaking away and slipping down into the hole. This perhaps was because we have dug an extra 500 mm deeper to allow for more layers of insulation boards, so this perhaps is making the walls having to cope with higher sides, but also we had rain during the night and that had softened the ground too.

We got most of the sandy soil out when we stopped for lunch.

Module-4-Hole-dug-and-Flooded1

This module is our primary “large” hot water tank that has the hottest water from the solar array and also would receive any “compressed” heat during the cheap overnight electricity hours by taking low temperature water from other tanks and topping up this primary tank.