Friday, 20 August 2010

Sheep Yards on Ochre Arch

In response to the recent article published in The Grenfell Record titled “Shearing with Sunshine at Ochre Arch” we received a fabulous letter from David and Jenny Johnson who now live at and farm using Permaculture techniques near Woolgoolga on the north coast of New South Wales. David’s father Clarrie at one point owned the property “Rutland” located about 5 km from us further along and to the east on Goodes Lane. David’s sister Marie and her husband Don Hampton owned “Ochre Arch” (“Cleveland” as it was then known) from around 1965 to 1977.

The sheep yards on our place are quite unusual as far as materials go, with the main steel pipes having originally been manufactured for and used as steam engine pipes. The accompanying photograph was taken 15th June 2010 and shows the pipes quite clearly, as well as some of our wether lambs prior to them being transported for sale at Forbes. Our shearing shed can be seen in the background.

In David and Jenny’s letter they explained that the steam pipes Don Hampton used when constructing the yards in came from a large batch that Clarrie Johnson had procured from the railway workshops in Sydney in about 1963 when David owned neighbouring property (to the north of us) “Pinnacle”. “They came as four pipes about 12 foot long in a continuous session with two open ends along side each other with a double flange and three of the joiners like shown in the yard picture”. David used pipes from the same batch for manufacturing cattle yards at the property he owned at that time “Braeside” near Bogolong towards Grenfell. He slipped the pipes over the top of the weldmesh and cemented them in as the corrosion from prior use made the material extremely difficult to weld.

Friday, 13 August 2010

Batteries for Our Remote Power System

Yesterday I re-read the ‘Operating Instructions’ for the batteries that are installed as part of our remote power system and was reminded of quite a few important things to keep in mind about them. To be specific we have 24 X 2 volt ‘valve regulated lead-acid’ “type 8 PVV 1200” batteries manufactured by the German company BAE Batterien GmbH. The purpose of our batteries is to store and provide direct current for conversion to 240 ac volt via the inverter.

The valves on the top of the batteries allow for release of hydrogen and must not be opened as doing so permits the access of oxygen which discharges the energy in the battery cells. Adequate ventilation is essential.

The batteries have to be kept out of direct sunlight and need to be installed and operated such that the ambient temperature difference between the cells or blocks within individual batteries is very small (less than ‘3 K’ … whatever that means!). The strings of batteries are best to be installed in specially designed cabinets for temperature evenness control and the connectors between the cells all need to be the same diameter and length.

During discharge (supply of an electrical current) the active materials in the batteries are converted to lead, sulphate and water. Curiously, the faster the rate of discharge the less amount of aggregate current ends up being available.

For long life the batteries need to be returned to full charge within a period not exceeding 4 weeks. Our batteries are classed as ‘deep discharge’ which means they can be totally discharged from time to time, however it is not our intention to do this. We have our back-up generator set up to auto recharge the batteries by 20 % from 65 % as and when this reduced charge level occurs (as mentioned in a previous blog post). I’m assured that the 65 % minimum is about optimal but have not seen any empirical data supporting this. Car batteries are not at all ‘deep discharge’ and will deteriorate rapidly if this occurs regularly.

If the battery voltage is permanently less than full it will discharge by itself resulting in ‘loss of capacity and possible sulphation of the electrodes’.

What I found particularly interesting is that when a battery is classed as ‘fully discharged’ this does not mean that it has zero voltage. By way of example, each of our ‘2 volt’ batteries are considered fully discharged (called the ‘final’ voltage) when their voltage falls to 1.8. Conversely a ‘full’ battery holds more than 2 volts … and for us this generally occurs when the voltage is 2.4.

The ideal operating temperature range for our batteries is 10 to 30 degrees Celsius. The rated maximum is 45 degrees C however they will handle temperatures for very short periods of up to 55 degrees C. High temperatures have the affect of reducing the operational life of a battery. I was unable to find information on the absolute minimum temperature batteries can handle and have noticed that cold nights do seem to reduce battery voltage more. Cold temperatures have the long term impact of reducing battery storage capacity.

As far as maintenance goes, during the whole life (estimated at 15 years) our batteries do not need to be refilled with water. “The electrolyte is diluted sulphuric acid and fixed as GEL made with micro porous SiO2.” It is recommended that every 6 months the voltage and surface temperature of a sample of batteries be checked and recorded together with the room temperature. Every 12 months the voltages and surface temperature of all batteries are to be measured and recorded.

If the batteries ever need to be stored for extended periods they should be left fully charged and in a dry frost-free room.

So … what does all this mean in the context of how our batteries are presently installed? In short our location and set-up augers well for good extended life and performance of the batteries. We experience very few frosts each year and having the batteries off ground level within a cabinet within a closed room means that they should never reach zero degrees C … especially given that each one weighs 70 kg and they are installed side-by-side effectively creating a 1680 kg block. Whilst our summers are hot it is not common for temperatures to exceed 45 degrees C and since climate records have been kept in the district the hottest day on record was 48 degrees C … well within the 55 degree C maximum. Added to this we do have an additional roof over the container where we keep the batteries, virtually eliminating the chance of temperatures getting higher than the external ambient within the storage room due to heating by sunlight on the roof and walls. The set-up of our back-up generator means that the batteries should never be discharged to high risk levels and the sunlight patterns are such that I’m confident the batteries will get to fully charged levels for short periods at least once every 4 weeks regardless of season.

Wednesday, 11 August 2010

Dew Quantity Variations

We’ve yet to connect the guttering on the solar-panel shed to one of our new tanks. Consequently each morning when dew has formed on the roof the resultant water runs out of the guttering onto the ground. I decided to measure the quantity of water generated by the dew process over 3 nights by placing a 200 litre drum under one of the gutters.

The shed dimensions are 12.2 metres width and 17 metres in length giving a total roof area of 207.4 square metres. The roof is peaked in the middle with gutters along both of the long edges. This means that the roof area feeding into a single gutter is half of 207.4 square metres = 103.7 square metres. The quantity of water captured from ‘normal’ overnight dew was 3 litres; on a ‘light frost’ night 8.5 litres water was measured and on a ‘heavy frost’ night 22 litres resulted.

22 litres from 103.7 square metres equates to receiving 0.21 litres (210 millilitres) of water per square metre of roof area … or the same as receiving 0.21 mm of rain. This is just less than a cup of water (250 millilitres) per square metre … quite a bit of water in the scheme of things.

Thursday, 5 August 2010

Rain Water On Tap

Yesterday we finalised connection of rain water (cold only at this point) into the pipes in the cottage on Ochre Arch. The set-up for rain water supply was described in broad terms in the blog article we posted on 28th May 2010 titled “Planning Our House Water Supply”. We ended up using 63 mm outside diameter polythene pipe in the ground, meaning that there is virtually zero friction loss. The pump is a Grundfos model CH 2 60. After correct priming the flow rate to the top (balance) tank was 22 litres per minute and the pressure was 450 kPa. Both of these figures were / are spot-on with what we were hoping for.

In this photograph you can see the actual connection from the poly pipe into the copper cold water pipe at the rear of the cottage. The internal diameter of the flexible connecting hose is very small at about 4 mm but the pressure generated from the balance tank located 45 metres in elevation above the house ensures adequate volume.

It is worth recording what having the water connection means in practical terms. In the accompanying photograph are the items we can now retire. What we did routinely was:
• Use the 2 X 10 litre containers to carry drinking water from the concrete tank at the shearing shed to the house. The distance is about 75 metres and on average we used 20 litres a day for drinking and hand washing
• From these containers we’d fill on a needs basis the blue 5 litre plastic drink bottle (kept on the bench in the kitchen), the green with white spots jug (kept on the wash-basin in the bathroom) and direct-fill other water bottles, hot water kettles and jugs, and drinking glasses
• Use plastic buckets and 20 litre containers to source washing water for the washing machine from the galvanised iron tank at the house

Right at this minute Jan has a load of washing underway via the washing machine. Not only does the new set-up save a lot of physical energy but it also avoids water inadvertently spilling on the bathroom floor and requiring subsequent clean-up.