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Savings attributable to PV System


Chris Hobson
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The continuing rise in the diesel price caused me to act. I had been considering solar for some time but a series of fuel hikes caused me to bite the bullet.

 

In my calculations I worked out that (with a bit of thumb sucking) that we could repay our investment in 19 months.

 

Now that I have access to real data I thought I would revisit my calculations.

 

My generator still runs and we generate about 10 kWh/day(shared between myself and our staff cottages) which uses about 7 litres of fuel a day. Fuel costs are about R10/litre .So fuel costs run at about R7/kWh. Add to that servicing R2000 every 3 months and overhaul R25000 every five years and 1kWh costs about R10.56. We are producing  an average 12 kWh a day (last 6 days 2 sunny 4 cloudy or partial records) . So a saving of R126.72 a day.

 

R80000 divided by R126.72 = 631 days or 21 months. I am still very happy on our ROI. 

 

P.S. If you think that is expensive pity anyone who has a rural Eskom connection. Fairly often they pay R1500 -R1700 p/m just in connecting fees and levies.

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you are quite correct Chris, and by the way well done. I had a client on a small farm who had 3 phase supply plus a smallish solar system, paying R1500 a month connection fee plus the small amount of R190 for usage. we decided on a slightly larger inverter with a few more pv panels, and told eskom to disconnect and remove the supply poles from the farm or pay rental....she has now been Eskum free for a year, and as happy as.....

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you are quite correct Chris, and by the way well done. I had a client on a small farm who had 3 phase supply plus a smallish solar system, paying R1500 a month connection fee plus the small amount of R190 for usage. we decided on a slightly larger inverter with a few more pv panels, and told eskom to disconnect and remove the supply poles from the farm or pay rental....she has now been Eskum free for a year, and as happy as.....

 

Hey Mike, how did you go about sizing the batteries for going off the grid completely?

 

Surely you would need quite a large battery bank to allow for say 2 -3 days autonomy?

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Hi Carl

 

Dependant on where you live it is cheaper to have a standby generator to cover periods where there is insufficient sun. Yesterday it rained and we still managed to generate 7kWh. I see batteries as a necessary evil and try and utilise energy as it is generated. Batteries are by far the biggest expense. For me to have 3 days autonomy would have more than doubled the cost of the system. I have about 12 hrs autonomy (DOD 30%)  without the generator but then again I do live in the Karoo.

 

How have your Steytlerville relatives solved the problem of energy in periods when solar production is not enough?

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Hi Carl

Dependant on where you live it is cheaper to have a standby generator to cover periods where there is insufficient sun. Yesterday it rained and we still managed to generate 7kWh. I see batteries as a necessary evil and try and utilise energy as it is generated. Batteries are by far the biggest expense. For me to have 3 days autonomy would have more than doubled the cost of the system. I have about 12 hrs autonomy (DOD 30%) without the generator but then again I do live in the Karoo.

How have your Steytlerville relatives solved the problem of energy in periods when solar production is not enough?

What size bank and generator do you have. I am considering this but have 3 house to manage. 2 tenants so I need to have a little quality consideration. Salem also has less cloudless days than the karoo?

Sent from my SM-P605 using Tapatalk

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Hi Mark my bank is 260 Ah. we generally use our appliances during the day. Night time draw is TV, computers, lights and microwave for a minute or two to heat up coffee/milo.

 

The generator is a 10 kW 3 phase Lister plant with a Compton-Greaves generator . Believe it or not Compton-Greaves is a Indian company. Been very happy with the generator. The generator is too big but does get use occasionally to pump water 180m up a mountain. I plan to put in a piston pump and perhaps reduce the energy required. 

 

Since my staff do not pay for electricity quality consideration is a low priority. They have power from 6pm to 10pm like we use to. 

 

Edit: we have a 5kVA "loadshedding" gennie which I have yet to test on my inverter but it would be my choice if it works in support of an Axpert. They are amazing machines - cheap - require zero maintenance (checking on the spark plug and oil don't count as maintenance) and seem to run forever. It was my sole power source after a series of mishaps after a Lister overhaul with counterfeit parts.

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I used it every day for more than 6 months. My missus left a newspaper on the stoep and the wind swept it into the fan which shredded the newspaper and lodged bits of newspaper in the fins. End result was that it blew a gasket. A new gasket cost R70 and we have used it off and on for about 5 years. Have not used it much since the solar installation.One hassle is that our one tends to hunt under low load but I think that has been cured now.

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Hey Mike, how did you go about sizing the batteries for going off the grid completely?

 

Surely you would need quite a large battery bank to allow for say 2 -3 days autonomy?

Hey Carl, as Chris does, they have a 5kw Genie for backup, most of the appliances are used during the day, night time, lights, tv, etc, water if wind okay via windmill to dam. I will be putting in a Grunfos water system for them soon. Their battery backup is only 600ah

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  • 1 month later...

HI DB9 - you have been quiet.

No my 6 - 10 ration costs R70 a day. For me to be completely independent would require probably a battery bank 2.5x my current bank 600-700Ah and perhaps 1kW extra panels.

My staff I would put onto a 3kW Axpert with probably 1500 -2000W of panels and my current battery bank. We could be independent for another R60 -70k. The repayment would be under 30 months based on a R10+ price for 1 kW/h. 

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Put in a prepaid meter for the staff, you'll recoup your cost even quicker.......:D

I've been quiet because my system is working like a charm. 10 months off eskom now....

Been playing with biogas. You should try it, you have a few skapies don't you?

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