Category: Groundworks

 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!

Module-4-lots-of-insulation-under-the-tank

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.

 The “Number 3” Energy Module has been completely buried and all finished. The three set of conduit pipes were inserted and connected all together in a central point, so that it will come up in the hallway, ready for plumbing at a later date.

Module-3-Finished

It was surprising that we used up quite a lot of the sand / soil to fill the gaps, which is good as we are not suffering from too much excess material that we might have to have paid transport to take it away. Maybe later, when we tackle the largest module “Number 5”!

this morning (only), we half buried the Number 3 Energy Module and put on the insulated lid.

Module-3-Insulation-complete

We sliced off all the edges and dumped the pieces in and around the gaps!

We have assembled the third set of our collection of Energy Modules today, the second biggest one! We put down two layers of insulation boards, a total of 240mm thickness of PU foam. Then a layer of geotextile fabric to reinforce the small gaps and edges between the joins of the various boards, to minimise the chance of the rubber stretching and bulging into voids under the crates.

The rubber membrane was unrolled and pulled into position on top, and draped around the edges (down pass the insulation layer) to wait for the final wrap-up procedure.

Then it was the job of moving 48 crates into the hole, to form two layers of 12 crates, all clipped together and also locked together with a forest of vertical tubes

Module-3-First-layer-of-crates-in-place

During the assembly process, the three holes were cut into the plastic of the crates to allow the usual access for our conduit pipes and inspection port to be inserted.

Finally, we got a sheet of DPM plastic to lie over the whole top surface to protect the insides from dust and dirt and also to act as a shield to stop the water evaporating when it gets hot.

We then pulled up the rubber sheet and tucked in each corner, just like a Christmas parcel, to provide a waterproof barrier to hold in the 8400 litres of water!!

Module-3-All-wrapped-up

Tomorrow, in the morning, we will start the insertion of the insulation panels around the circumference of the module, and start pushing the sandy soil back in.

 It was a long day of cleaning our Aquacell crates we need for Energy Module Number 3. Like before, each one had to be split apart and then each half jet blasted with high pressure water to wash out the dirt, spider’s web and plant matter!!

Our large pile of Aquacells has somewhat shrunken, we have now used 98 crates out of the total of 200!

Stack-of-Aquacells-Jun-8th

We ran into the evening in order to have all the crates washed and ready for tomorrow assembly in the Number 3 hole. Phew!

We finished digging out the third  hole. We then inserted two parallel wooden side rails into the ground, set exactly at the required depth (minus 1.7 meters below ground level) and use them to scrape away the final excess sandy soil by moving a plank of timber between the rails.

Shaun-collapsed-in-Module-3-Hole

Then we compacted the whole area using the petrol motor driven vibrating  plate, put in more sand and compacted again. Then we did a final scrape to get a nice flat and level surface to begin the building up of the energy module itself including its insulation layers.

Module-3-Hole-Finished-1

Module-3-Hole-Finished-2

But tomorrow, it is the messy job of taking apart and cleaning 48 Aquacell crates!! Phew!

Here’s today’s timelapse