Savings attributable to PV System

[Chris Hobson]

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.

[Mike]

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.....

[Chris Hobson]

That is the hassle with Eskom. If you want to go over to solar you have to go cold turkey. You cannot slowly over time reduce you load  because it does not really make any difference to your power bill.

[Carl]

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?

[Chris Hobson]

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?

[Carl]

I don't think many of the farmers in the Steytlerville district have embraced solar yet, well not that i know of. Mostly use either eskom or diesel generators.

 

Do you ever pass that way? 

[Chris Hobson]

I seldom do was in Steylerville about 3 years ago. I pass through Wolvefontein on the way to PE.

[Mark]

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?

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[Chris Hobson]

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.

[Mark]

How often do you actually use the load shedding gennie

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[Chris Hobson]

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.

[Mike]

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

[Mark]

Scary stuff...

 

http://www.iol.co.za/business/news/high-power-hikes-seen-until-2022-1979167

[subok01]

Hi Chris, what is the kWp of your panels and inverter type and size?

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[Chris Hobson]

Morning Subok01

 

Welcome to the forum.

 

I have 12 x250w Yingli panels (3kW) and a 4kW Axpert/Mercer inverter and a 260Ah battery bank.

 

Do you have a system up and running?

[DeepBass9]

The problem with your 6 to 10pm staff electricity ration is that will need to be powered by batteries which will probably negate any savings you make on the generator.

[Chris Hobson]

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. 

[DeepBass9]

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

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?

[Chris Hobson]

My skapies roam free so collecting their manure is not going to be easy. I have considered putting prepaid for the staff. We will see how it goes.