CopperEagle

After careful scientific evaluation I bought an Induction cooker. It happened like this. Being a sucker for a bargain I opened the bidding for a griddle pan on Bid or Buy, and duly won the auction. When the pan arrived I was surprised to see that it had a shiny round metallic insert on the bottom of the pan. "What's that for I said to my partner"? Being knowledgeable from a minor addiction to 'new home TV programmes' she said "it's for an induction cooker" To rectify my ignorance of these culinary matters I Googled and U tubed them; then, being a sucker for a bargain I found one with almost R500 off the list price, so I bought it.
It is a Russell Hobbs single plate cooker drawing a maximum of 2100 watts, however it is adjustable down to 100 watts and usually operates at about 500 watts, after I have used an initial setting of 800 watts to heat the pan. It is clean and efficient and has enabled us to bring out of disused storage an old fashion cast iron frying pan and a cast iron cooking pot, both of which function perfectly as long as you can lift them!
It is a useful adjunct to my solar set up as I have left out the oven and hot plates from my system. I would recommend an induction cooker to fellow 'power  forumers, perhaps you can benefit from my careful scientific evaluation!!

Hanging off solar panels with a 5kW Hybrid inverter and 4 'naffed 12V 170Ah batteries with an extension lead to a neighbour (for after hours mostly), solar panels being ( 9 + 8 ) 280W panels.
If you are wanting to get off the grid completely or partially with panels etc. you should expect to change your lifestyle/timing of your consumption somewhat, unless of course you are one the southern hemisphere's Rockefellers.
In addition to the panels etc. we also have a 12glass evacuated tube solar water cylinder, which I think has 200liter capacity (might be 100). We've gone half last winter with this lot, so will have to see how well we do in the winter ahead.
Dishwasher - we run this mid day, so solar power only, the grid does not contribute to the running of the dishwasher at all and in the future when we will be without the extension lead and off a bunch of LiFePO4's we will continue this, if you're short of crockery and thus *have to* run at night, more crockery should be a lot cheaper than battery capacity, it makes sense to time shift this.
For the hot water side, I need to come up with a few things, to make life easier etc. the water here is fed by way of a 500 or 1000liter Jojo tank on a 6 or 8m stand, so gravity fed. We pretty much only shower, so running a bath might occur once a decade, unlike the annual bath of Vitalstatistix, since by the time the bath is more than half way full, you may imagine there's a crocodile hiding in there. What I would want to add, for info is replace the HWC's drain plug with one with 2 pockets in it, one, maybe 8cm deep and the 2nd one 30cm deep then I can run a pair of temperature sensors in these and know whether at 10PM on a cold winters night I can get a shower or not. Also, to reduce the water wasted since the run from the HWC to the main bathroom is probably 30m or more, have a small pump and temperature sensor that feeds the water from the hot water side, that would be too cold, into the cold water pipe (back to the Jojo tank) until a reasonable temperature has reached the bathroom side, this is less important, but I hate wastage and this would appeal to me.
If you are doing a solar hot water system as well, the pocket and sensor option may be something you'd want to consider home brewing, I haven't seen anything like this as yet, but think this would be quite handy. Also if you have a backup element you would at least know what you are looking at temperature wise. (I have messed around with some Arduino's and various sensors including DS18B20 temperature sensors and since I don't have cabling all these talk via 433MHz radio modules back to one of the Raspberry Pi's in the house, which is on the local & WiFi networks.) This would be the way I'll be doing it, when I get a round tuit 🙂
Ideally everyone who is on solar or looking at it, should probably have an interest in power measurement, Ellies used to sell Effergy 15A power meter units that plug into a 15A socket and provide a 15A socket on the other side, so you would be able to get an idea, what the appliance (dishwasher/computer/whatever) consumes that you plugged into it and therefore could figure out what is a *heavy* user as opposed to much less energy hungry items. As for the home in total, I don't know what is available these days, but I still have an old Owl energy meter, which gives me an idea on the kW consumption, updated probably every 30 seconds, or so, the data is chucked into a SQL like database and longer term graphs can give one an idea of when during the day how much energy is consumed.
Our baseline consumption here, for instance is around the 500 to 600Wh mark overnight (3 fridges/freezers + various other energy warts like 4 X Raspberry Pi's a 3G router a network switch or two and two WiFi access points + a 5GHz network link to the neighbour, VoIP phone or two,  laptop on 24/7 less than 30W average for the laptop etc. it all adds up 🙂 and I'm sure I'm forgetting some items.) So, from the extension lead, at this stage we end up using anywhere from 7k4Wh to 10k5Wh, but this could be reduced by, for instance not using the electric kettle until after power production is up to a reasonable level, but I *need* my morning cuppa, else murder may be the order of the day...
If you want to be an energy miser, you may want to either only heat up the amount of water you really need in the kettle, else put the rest in a thermos flask for use later, even if you want to bring it to boil again an hour later, using the thermos will lose a lot less heat/energy than leaving it in the kettle.
Ok, I think enough for now I'm sure not too many will want to read this, but if you do, I hope you find something in it that has value and maybe sparks an idea or two that has value for you as well.
 
 

I am having a borehole installed to share with some neighbors. 
The installer has placed a pressure tank on the system that feeds water from the borehole to each house. 
When this water arrives at my property i will have a tank to store water and a filtration system. The installer insists that I do not need a pressure tank for the system in my house, is that true? 
 
Also here is a screenshot of the parts he has quoted me. 

 
Also I am considering changing out the pump he has quoted me for a 1.5Kw JoJo branded VSD Pump as it is much more affordable.

Personal take: Batteries, geyser blankets and geyser timers.

I am not an expert in the field and just like to share the info and ask for opinions and views on the problem. I do not consider Li batteries here. I have a Kodak 3kW 24V inverter, and 24V Li batteries are very expensive (about R17,000-20,000 for BlueNova 26V-77-2k and R17,000-22,000 for Pylon UP2500 2.84kWh). Second generation 25.6V Li batteries by e.g. Revov are currently sold with a minimum capacity of 5.2kW and go for more than R30,000.

The information in this document is collected and compared with a focus on a low-consumption off-grid scenario. Solar panels (1,320W) supply enough power during the (sunny) day to run all appliances with a minimum energy contribution by the batteries (maybe max. 10% capacity). During the night (14 hours without energy supply by solar panels), a fridge is a major consumer and I like to cater for about 1.2 kWh during this time.

I consulted the spec sheets of AGM or GEL batteries advertised (but some not available anymore as I found out) in South Africa. I compared the data on constant power discharge down to a cell voltage of 1.8V. I adjusted the rating of a battery for a 10h constant current discharge to 1.8V per cell (10.8V per battery) since some battery model names refer their capacity to a 20h discharge and/or to a discharge down to a cell voltage of 1.75V (10.5V per battery). As a second adjustment, I multiplied with a factor to “simulate” a 200Ah battery. I assumed that with this approach a common base is created for a better comparison.

The second info I compared was the cycle life at different depth of discharge (DOD). It refers to the number of discharging/charging cycles until the battery drops to a capacity of 60% of its original rating. These discharging and charging cycles are mostly laboratory experiments under idealised conditions. I focused more on the ratings up to a maximum of 30% discharge per cycle. To strike a balance between my battery size requirements and acceptable daily discharge, I am considering a battery bank of a minimum of 4.8kWh (4x 12V 100Ah or 2x 12V 200Ah) which would give me 25% DOD at an overnight consumption of 1.2kWh. For a 20% DOD, one would need a capacity of 6kWh which can only achieved by combining four 150Ah or six 100Ah batteries since one or multiple sets of two batteries have to be connected in series to obtain 24V for the inverter.

For the two “simulated” 200Ah batteries with a total number of 12 cells and a DOD of 25%, one would require for a constant power discharge of 85.7W per hour over 14h (1200Wh) a discharge per cell of 7.1W per hour for 100% DOD and a possible discharge of 28.6W per hour for 25% DOD. So, the value of 28.6 at a discharge time of 14h is considered here as the minimum requirement per cell of the two simulated 200Ah batteries. Squeezing the power consumption of 1200Wh into 10h would increase the value to 40W per cell at a time of 10h (which is 4.8kW energy). These values are only indications of what kind of performance figures to expect.

The constant power discharge graphs are shown in Fig. 1 and the cycle life graphs in Fig. 2. Green circles indicate acceptable performance.




Fig. 1: constant power discharge for “simulated” 12V 200Ah batteries given in W per cell



Fig. 2: cycle life of batteries according to spec sheets or website information, 60% capacity as end-of-life is not always explicitly mentioned in the source

There are a number of other battery companies which I did not include here. Some perform too bad to be considered and others seem to be a rebranded product of another manufacturer.

According to one supplier, batteries based on lead crystal technology are not available in the country. The formerly supplied batteries by Betta Batteries are manufactured by GreenRhino, an American company. The Dutch office confirmed via email to me that they do not have an agent in South Africa. One can order from them and a 12-GRGS-200 battery costs €409 excl. shipping.

The Narada ICS range seems very good. In South Africa I could only find the NDF-Acme range which does not perform well enough and cost about R7,500 for a 12V 200Ah battery. I could not find a supplier for the lead-carbon battery Ritar DC12-100C. So, the good performers Narada ICS, Betta Lead Crystal and Ritar Lead-Carbon can be excluded since one cannot purchase them in South Africa.

The capacity of the Trojan SAGM 12 205 is only 174Ah which requires four batteries for the given scenario. One battery cost more than R8,000. Therefore, this battery can be ruled out.

Concerning the Allgrand batteries, the data are inconsistent. There seem to be a CNF and a CNFJ range and some spec sheets available from South African supplier cannot be found on the Allgrand website itself. For the Allgrand Gel 6-CNFJ-150 (12V 150Ah) battery, some data, e.g. a constant current discharge of 15A for all given cut-off cell voltages between 1.6V and 1.8V after 10h, can’t be correct; from the constant power discharge data, the battery might actually have a capacity of 135Ah instead of 150Ah, which means that the adjustment in Fig. 1 would not be correct and the battery would perform better than illustrated. More confusing, Allgrand states “up to 2000 cycles” and “up to 1000 cycles at 30% DOD” in writing which is far lower than the data published as a life cycle graph by the company. While their prices in South Africa are the best of all AGM/GEL batteries, one would like to have a better idea about their performance data.

Surprisingly, the expensive Victron range does not feature with noteworthy cycle life. In general, the spec sheets do not give a lot of information. A number of other batteries show a comparable performance on cycle life.

With the limited information presented here, the best choices for the mentioned requirements are the Omnipower and Oliter batteries. While the Oliter 12V 200Ah is a “genuine” 200Ah battery, the capacities of the Omnipower OPR 120-12 and 240-12 batteries are not 120Ah and 240Ah but 100Ah and 200Ah for a discharge to 10.8V over 10h, respectively. The Oliter with ca. R5,000 is less expensive than the Omnipower which costs ca. R7,000.

I must stress, that I have no experience in the use of any particular battery and merely oriented myself on the available data.

Any views on the validity of the analysis? Any real-life experience to share? I would welcome your comments.


 

 

 

Heat pump has been in for a little over 2 weeks now. From my observations, it runs for 30mins when the time kicks in. This is around midday. It then kicks in again with the bath/shower routines between 6 and 8pm. The latter times.. for about 15 or 20 mins. So in all. It appears to run for some 1h15 a day given the current weather and the current useage pattern. My guestimate is thus 1400w odd for hot water. 
So far so good. No noticeable difference in water temperature. Going to wait until May or June to gauge how it runs before I then move it onto essential loads. I can then also verify whether it does in fact run per spec at around 1200w. This should be easily covered by my PV which does virtually no work from 12pm currently.
My billing cycle runs from 18 to 17 of each month. So i will obly get to see its effect on total power from the next month cycle. However i am curious to see what these 10 days would have done.. for a change I am actually eager to receive the bill

One option would be to use the old fashioned CBI load-shed relay, they are quite robust and I’m sure you would still get them somewhere if you really need one. You wire both geysers through the relay and it will ensure one is always switched off while the other can be on. They look like the came from the ark but works well and come in various amp ratings.

My apologies, I used an arbitrary diameter without measuring it, I based it on my own (arguably smallish) 200 litre 800W heatpump that has a (now measured😎) 110mm inlet and outlet. 110mm PVC pipes are quite cheap, R349 for six metres, and I use one coupled on my heat pump to cool my home in summer. But larger diameter PVC pipes are available, maybe not as cheap, but certainly workable.
The important thing is that the heat pump itself will generate heat, and that's why I suggested it to be outside, it's important to separate these components of the design, much in the same way that a fridge motor and compressor are outside of the "cooling box". @CopperEagle actually has a great idea to use the "free" heat generated by the inverter's MPPT, battery charger and other DC--> AC -->DC circuitry, in order to increase the heatpump's efficiency. So what is stopping us using it to also cool the batteries and inverter at the same time? We know that the enemy of all electronic circuitry is heat, so reducing it would be beneficial.
The air pumped in will be colder, but due to the heat exchange, also drier. Drier air may increase the build-up of static electricity (so earthing of the PVC ends or "nozzles" may also be necessary, but these are easy problems to solve (using an earthed grid on the nozzle)). Drier air would also be less corrosive to electronic components, so there is another win. It might be prudent to include automated summer and winter (butterfly?) valves on the (100-300mm) piping, because a heatpump's output can reduce the temperature of a small room quite quickly, and it may be too cold for the Lithium batteries. A good design may therefore include a few heat sensors in strategic places, and the necessary automation to provide automated opening and closing of the winter and summer valves.       
 
 
 

I would consider installing the heatpump just outside of the room, use the room as input (ceiling high) sucking air in using a 120mm pipe, and then use another 120mm pipe to pump the output of the heatpump in (at around floor level) to cool the inverter and batteries

Generally and due to heat loss the heat pump should be not more than 5m from your geyer/tank. All the cold air that exits the heat pump will be sucked in and this will cause a very inefficient unit. Normal outside air is better. Our winters are not that long to have a major affect on the heat pump. In winter the heat pump could have a COP of only 1 which means it will take a lot longer but then be on par with a element from a power used point.