7 minutes ago, Dex_ said:

surely 115kW will cost you more than the ~190 it costs to fill a 9kg? (

It does... very slightly. 115kWh costs around R230 where I live now. So the gas is slightly cheaper, but because it is so much less efficient at heating it ends up costing more.

As for the original question about just how much sun we had yesterday. Yesterday was my second best day since enlarging the array. I made slightly more on March 15th this year.

37 minutes ago, plonkster said:

So the gas is slightly cheaper, but because it is so much less efficient at heating it ends up costing more.

Hi Plonkster, I am curious about this - my "subjective" experience is that gas has always been much more efficient for cooking on a gas-top stove. This is comparing between a gas-stove and an electric-powered "ceramic-hob". 

The electricity-powered ceramic hob was reasonably efficient as long as the pot/pan was perfectly flat and a similar size to the hob diameter.  However, I find a gas-hob heats up a pot/pan much faster and has virtually "instant" control of the temperature. This usually results in a faster overall cooking time on gas - and hence improved overall energy efficiency.

One other observation is that the modern obsession with stainless-steel for cooking pots/pans is completely absurd! Stainless Steel has a thermal conductivity about 1/15th that of Aluminium (and 1/20th of Copper) - so most of the stove heat goes into heating the air in your kitchen when using stainless steel pots!

I have little experience with induction stoves, but this could be an interesting comparison.

2 hours ago, The Bulldog said:

Total of 42 panels - mixture of 250W  and 275W panels. That's all I could fit on the roof. Oh wait - there's West facing... Plonkster seems to think that not a bad direction either. Could squeeze another string of 14 panels there I think.

Ready to feed in once COCT gives the go ahead (hopefully soon). Got a 150A three phase connection and they authorized just over 30KW of feed in. Not enough roof space to get to that number though. 

Goeie griet!!!! Oor die 10kw se solar. I guesswe will see your house from space with all that pannels. What you running in the setup? 

17 minutes ago, NigelL said:

Hi Plonkster, I am curious about this - my "subjective" experience is that gas has always been much more efficient for cooking on a gas-top stove. This is comparing between a gas-stove and an electric-powered "ceramic-hob". 

Well... I have been called an google engineer 😛 When I'm unsure, I research what others say. The numbers I found seems to back up my gut feeling. Hold your hand next to the contact surface between the heat source and the utensil and see how close you can get. Do this with both the gas flame and the electric plate. You will note that a heck of a lot of heat from that gas flame just buggers off into space and doesn't heat the cooking utensil. When there's a flat contact surface, and if the container is appropriately sized, the heat transfer is significantly better. This observation plus a simple math calculation to convert the calorific content of LPG to kWh suggests that gas isn't all it is cracked up to be. Not for saving money anyway... but definitely for the pleasure of cooking! No doubt about that 🙂

13 hours ago, plonkster said:

but definitely for the pleasure of cooking!

what about cleaning the stove afterwards 🤣?

17 hours ago, plonkster said:

I still find that people grossly overestimate the amount of electricity they actually use for cooking. The average household that cooks a pot of vegetables, rice and meat (as is typical in South Africa) three or four times a week will end up using less than  10% of overall use in the month for cooking. If your cooking is around 10% more efficient, that means a saving of 1% on the total bill . If you go with gas instead, it costs about 10% more (assuming my previous estimate of roughly half the efficiency to be accurate). Unless you measure carefully the difference is almost negligible.

Yes. We had an incident recently of the oven being turned on late afternoon. After I had recovered and the oxygen mask was removed, I checked my system and it seemed to me that an oven uses less than a regular geyser. Geysers seem to be public enemy number 1 for electricity consumption.
 

18 hours ago, plonkster said:

How many times have you heard people tell you that gas is so efficient, they've been using a single 9kg bottle of LPG for 6 months now? Well, as we know, energy is neither created nor destroyed, and with 115kWh in that bottle, the electricity bill would have been about the same, and possibly quite a bit less (due to efficiency). But since nobody (or few-bodies) does a before and after test, everyone just marvels at how awesome the gas stove top is 🙂

I am no engineer, but it seems intuitive to me (because I have been told this since I was knee high to a grasshopper) that the big plus for gas is that there's no waiting for things to get hot, and that's where the saving is.

They do need some maintenance. Every couple of months I clean all the burners and jets with a needle or an old guitar string. 

26 minutes ago, Bobster said:

Geysers seem to be public enemy number 1 for electricity consumption.

Swimming pool pump is a contender as well.

 

8 minutes ago, Bobster said:

I am no engineer, but it seems intuitive to me (because I have been told this since I was knee high to a grasshopper) that the big plus for gas is that there's no waiting for things to get hot, and that's where the saving is.

They do need some maintenance. Every couple of months I clean all the burners and jets with a needle or an old guitar string. 

I think the convenience, is that it's still there when all else has failed. 

15 hours ago, NigelL said:

I have little experience with induction stoves, but this could be an interesting comparison.

Referencing somebody's google tests an induction plate was 30% more efficient.

That didn't mean it used 30% less power, it used the same power, just boiled the water 30% faster.

18 minutes ago, phil.g00 said:

Swimming pool pump is a contender as well.

 

not when it runs on the solar 😛

Just took receipt of one of these.

360USD + +/- 130USD (shipping) (its 22kg) + customs duty & VAT.

The 1200W  72V version.

Not installed yet, but looks and feels like quality. I have bought a couple of solar borehole pumps off them before and was quite happy.

https://kairuijidian.en.alibaba.com/?spm=a2700.8443308.0.0.20083e5f8OBXYw

Edited September 28, 20196 yr by phil.g00

My plan is that besides the main system, I will have several satellite offgrid systems. 

The satellite system are very simple, but dedicated to specific jobs, no batteries  and in the case of the borehole pumps, just straight off two panels. ( the controller is built into the pump).

(The swimming pool pump has an external controller as do the 300W transfer pumps.)

This saves me on cabling from the main system, ( just a couple of panels here and there) and things are sized so they can just do their thing all day, everyday.

Basically, the water supply to the guesthouse will be immune to load-shedding.

1 hour ago, phil.g00 said:

Just took receipt of one of these.

360USD + +/- 130USD (shipping) (its 22kg) + customs duty & VAT.

The 1200W  72V version.

Not installed yet, but looks and feels like quality. I have bought a couple of solar borehole pumps off them before and was quite happy.

https://kairuijidian.en.alibaba.com/?spm=a2700.8443308.0.0.20083e5f8OBXYw

wowsers that's a bit of a penny for a pump though.

6 minutes ago, Dex_ said:

wowsers that's a bit of a penny for a pump though.

Yep, compared to a straight 220Vac, I suppose so.

But the satisfaction.....priceless!

7 hours ago, Bobster said:

because I have been told this since I was knee high to a grasshopper) that the big plus for gas is that there's no waiting for things to get hot

Right. I have been told that over and over as well, and also when you turn it off. No wasted heat because the plate is till hot long after you're done cooking. And there might be some truth in that for the first minute or so (would be interesting to know when the break-over point is), but eventually the efficiency of the heat transfer will catch up with you.

Interesting related topic: Does stop-go systems in cars really save fuel? It takes a tiny bit more fuel to restart an engine, so again there will clearly be  a break-over point where leaving the engine running stops being more efficient. Interestingly... that number is 7 seconds 🙂

 

On 2019/09/28 at 6:15 PM, plonkster said:

Right. I have been told that over and over as well, and also when you turn it off. No wasted heat because the plate is till hot long after you're done cooking. And there might be some truth in that for the first minute or so (would be interesting to know when the break-over point is), but eventually the efficiency of the heat transfer will catch up with you.

Also the calculations revealed in this thread would cater for the reduced warm up time, and show that even with that the damage to one's wallet is about the same.

So it's not a money saver really. But there remains convenience and not loading your backup power system.

On 2019/09/28 at 6:15 PM, plonkster said:

Interesting related topic: Does stop-go systems in cars really save fuel? It takes a tiny bit more fuel to restart an engine, so again there will clearly be  a break-over point where leaving the engine running stops being more efficient. Interestingly... that number is 7 seconds 🙂

It depends on how long the average stop is. If it's more than 7 seconds then you score.

But the point of this system, it seems to me, is to cut emissions, to not have cars belching gasses out of their exhaust whilst standing. Then it's one of these cases where the multiplier affect comes into place: One car will cut emissions only a little, but millions of cars make an impact.

1 hour ago, Bobster said:

But the point of this system, it seems to me, is to cut emissions

It's two sides to the same coin. Fuel not burnt (and not paid for, therefore economy) is also emissions not... uhm... emitted 🙂

Of course it comes at the cost of a larger battery, beefier starter motor, and so on, so that in terms of TCO (total cost of ownership) this might actually not save the consumer's wallet as much as it saves the environment 🙂

Still... it was very interesting to see the numbers. If I recall it was from a youtube channel named "Engineering explained". Seven seconds. The average traffic light stop is longer than that, so the argument is settled.

29 minutes ago, plonkster said:

It's two sides to the same coin. Fuel not burnt (and not paid for, therefore economy) is also emissions not... uhm... emitted 🙂

Of course it comes at the cost of a larger battery, beefier starter motor, and so on, so that in terms of TCO (total cost of ownership) this might actually not save the consumer's wallet as much as it saves the environment 🙂

Still... it was very interesting to see the numbers. If I recall it was from a youtube channel named "Engineering explained". Seven seconds. The average traffic light stop is longer than that, so the argument is settled.

I think that depends very much on where you are. I remember being on holiday in Wales a few years back, in Llandrindod Wells. And the robots in that turn seemed to take forever to change. The locals were already turning off when they saw a red light because they knew they'd have a long wait.

And, of course, it's not just for traffic lights. It's for traffic jams as well, or waiting outside a shop whilst a passenger is buying a couple of items - any occasion on which your car may be standing and you have not though to turn off the engine (and it would do you no great disadvantage if you did).

TCO... yes.

But... these always get cheaper as they become prevalent. ABS and ESP are common place now, and you're hard pressed to find a new car that doesn't have airbags. These were all exotic items 20 years ago.

Edited September 30, 20196 yr by Bobster
wait, not weight

13 minutes ago, Bobster said:

But... these always get cheaper as they become prevalent. ABS and ESP are common place now, and you're hard pressed to find a new car that doesn't have airbags. These were all exotic items 20 years ago.

Very very true. ABS is practically standard. Traction control is still a bit of a luxury. Reverse Cameras seems to be the next item to become mandatory (either legally or just because consumers want it).

I always thought it is ridiculous... just teach people to use their mirrors, like we did when I learned to drive! (Grumble grumble these millenials are so spoiled... etc etc).

Then I got a car with a reverse camera and the beeping sensor thing (cause when you buy second hand you get whatever options the previous oke chose). Man... what a pleasure! I can absolutely see the point of this system in our crowded urban areas.

(With my previous car I would open the door and look out towards the side. A trick I learned from my dad and his Bedford truck).

Edited September 30, 20196 yr by plonkster

On 2019/09/27 at 3:27 PM, Bobster said:

Highest I've seen is about 3200. I have a theoretical peak of 3900, but half the panels face north and the other half faces east, so I'll never see that peak, even for a split second.

Though yesterday I hit 3500 odd. Which surprised given that the theoretical peak power is 3900 (that's if you just add up all the panels) and the panels don't all face the same direction.

Also had some good peaks the last two days.

1396 North
1924 East
1809 West