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Jakes
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Hi guys

 

I'm new to the forum, and my contribution can initially not be anything else than a lot of questions.

 

I'll appreciate your input on the way forward for me.

 

We are moving to Robertson, probably later in the year or early next year. The plan is to be totally independant of supplied electricity.

I'd like to start purchasing the components now.

 

We will mostly be 2 in the house using gas for cooking (except for a microwave oven) and solar water heating.

 

I've contacted 2 suppliers and the suggestions for the power supply for our house seems to look as follows:

  • (Up to) 10x300W solar panels. (One guy suggests ReneSola panels @ R10/W, the other Tenesol @ R21/W).
  • A 60A charge controller. (MicroCare @ R5 200).
  • A 5kW inverter @ R20 000. (MicroCare from the one guy, an 3kW unknown brand from the other @ R15 000).
  • The battery options vary between R30 000 and R70 000).

Now some questions:

  • How would you guys specify the power system?
  • Which batteries do you think will be best to use? I'm specifically trying to find a good value for the money solution. Paying more for batteries that will last longer seems to make a lot of sense, although I will steer away from a R70k battery pack.
  • What are your feelings about the solar panel recommendations? Also as far as brand names are concerned.
  • In my mind it makes a lot of sense to also install a wind turbine to help on cloudy days and to maybe extend the life of the batteries. The suppliers don't really seem to agree with my thinking about a wind turbine. It would seem that our farm lies in a yellow or maybe orange area on the wind atlas, 7-8m/s wind speed. (Although it seems that the measurements were taken at 100m above the ground. So I don't know if I'm jumping the gun to even be looking at those figures).

 

I also need to take water out of a borehole. The borehole depth: 65m, The water level is about 20m below the ground level, the tank will be about 70m above the borehole ground level. The total head will be around 100m if I'm not mistaken. My thinking is that we will not need more than 1 000 litres of water per day.

 

So I'll need a power system for the house and a solar powered borehole pump, and would really appreciate your inputs.

 

Thanks a million.

 

J.

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Hi Jakes 

 

Many thanks for your first post. No problem at all with the questions. This is the purpose of the forum.

As a forum founder I am not able to promote any supplier over the other-this is my duty and promise to all the members. However I may give you market rates and what you can expect roughly. Your post is perfect in a sense that allows other members to share their experience and allow you to get the best value for your money. This making the market fair and safe for new members that want to get into renewable Energy. I'm sure the other members will welcome your questions and all support you in what ever way they can with a host of great recommendations.

 

My Rough Recommendations:

 

With Regards to Solar Panels. You would want to look for brands with a good power and product warranty. TUV Certifications. Mono crystalline Panels are great as they are about 15% smaller in size than Poly for the same power rating.

No matter what the brand you should be Paying about R10-11 p / w. for the Units. 

 

To specify the power requirements. I have uploaded a straight forwarded excel power consumption calculator you are free to use. This will give the members a basic idea of your load requirements and I am sure they will want to hear more.

 

Battery recommendations will be better calculated once the forum members get an idea of your load requirements from the completed excel.

 

A good quality wind Turbine with a good warranty is always a good investment if you have a good site. It wont be any good if you do not have open clean air for the unit. Wind Turbines protect the batteries and supply power all the time when the wind is blowing. In the late after noon and night time when there is no solar, as you said the wind turbine protects a expensive battery bank from deep discharges.

 

Borehole pumps are always a great project. There are some awesome brands on the market with big dynamic heads.

 

I am sure a lot of the members will be able to assist you in spending your capital correctly and getting best value and performance.

This is the essence of the forum- Share Knowledge , great ideas and promote healthy fair advise.

Thank you for your exciting post.

Regards

E

Off Grid Loads.xls

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Hi E

 

Thanks so far for your response. Please guide if I should overstep the lines of the forum.

 

I've completed the spreadsheet. Where I couldn't alter the "hours" I halved the "number". Half a hair drier for an hour would be the same as one hairdryer for half an hour.

 

I chose 48V as the system voltage thinking that the cable from the wind turbine might be very long and the higher voltage should make for a thinner cable?

 

I'll supply answers to the questions as they arise and I learn more.

 

The ideal would obviously be to deal with suppliers with knowledge and integrity. If they've got good prices that will make for a nice red cherry on the top.

 

Thanks again.

 

J.

 

Solar Calculator.xls

 

 

 

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Hi Jakes,

 

You load list looks a bit light, but lets work with it as is.

I would say the 10 x 300W panels and the 5kW invertor does seem fine for your use according to the load list.

The 60Amp load controller might be a bit light (60Amp * 48V = 2880W) but it is still within reason, so no problem there.

 

I do think the battries will be your stumbling block.

Do not work on a discharge of 50% capacity, as that will destroy your battries very quick. (Look at cycle live VS depth of discharge)

Rather work on 20% discharg, so for a 105AH, you should only use 21AH.

Also, only 1 day of backup time is very optimistic, if you have 3 days of winter storms, but a genny might sort that problem out.

If you going totally off grid, rather look at something like the 2Volt MSolar battries, but yes, they very expencive, but would last you a lifetime if properly cared for.

Also include a good battery monitor that can give you AH readings and not just a volt reading.

 

Another plan could be to run a cheap 3kva genset for when you ironing and vacuuming. Would save you more money in the long run.

 

Water - What it the cost these days of a "windpomp"? If there is enough wind to consider a wind turbine, why not use a "windpomp"?

I know the electrical borehole pumps is extremely costly, but how they compare to a windpomp, i'm not sure.

 

When going for solar water, vacuum tube is the best IMHO.

 

Good luck and let us know how you getting on :)

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  • 4 weeks later...

Hi Guys

 

Thanks for the responses so far. I really appreciate the help.

 

I've also had a response from a supplier here, thank you.

 

The homework thus far would indicate a system as follows: (Mainly dictated by my (lack of) finances).

  • 2000W worth of solar panels. I can expand later, or add a wind charger.
  • A 60A charge controller.
  • 4 x M-Solar batteries. I'm thinking the 3MIL17S-600's would work well. That might be light, but it's more than R30 000 worth of batteries. I'll expand on the battery bank as I expand on my knowledge of how to withdraw money from the Red Bank without a credit card. (I believe you go at 02h30 in the morning).
  • A 5000W inverter.
  • A battery monitor.
  • Maybe a small generator for days on end with no sunshine.

Some questions:

  • What is needed for the generator to be able to charge the batteries? Does that ask for a different inverter, like the Oasis of MLT Drives?
  • Will it be easy to add a wind charger at a later stage?
  • Some would certainly think that the charge controller and the inverter are too big. Is there a disadvantage using a larger inverter and controller, other than financial?
  • Can I buy the components and do the installation myself? A chat to a supplier seemed to indicate that they will supply and install R85 000 worth of equipment, and the total account would be for R200 000, if everything goes smooth, he said.

Wetkit. I did some homework on a windpomp. It seems that you'll fork out north of R50 000 for an entry level one. For the borehole pump I'm thinking going 220V, with solar panels, a controller, batteries and an inverter. This way one can save between R5 000-R10 000, compared to a solar borehole pump. (Correct me if I'm wrong, I'd love to be).

 

I'd like to hear from suppliers here to quote on the complete system, and to suggest changes if needed.

 

Thanks again.

 

J.

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@Jakes, I'm not a supplier, but I hope you do not mind me making a few comments....

 

I can see that you a bit stuck between a rock and a hard place.

You most important decision will be to select a system voltage and stick to it.

If you looking to change later on, you would have to replace the invertor :(

Invertors DC voltage is fixed, so can not change from 24V to 48V later on with the same invertor.

 

Your new proposed system is 24V.

To get the max out of your 2000W PV, you will need at least an 80Amp controller. 2000W/24V=83A. (The Microcare 80Amp controller works out the cheapest when comparing rand/Amp)

You will need some good wiring on your invertor. 5000W/24V=208Amp.

If you now go to a 48V system, you will be able to add another 2000W of PV panels later without having to install a new solar controller, but it would also mean you have to double the battery bank, so more battery cost :(

 

I believe you have to find a tradeoff point, where you happy with what you getting for what you spending.

 

Managing your daytime and nighttime load, might save you more in the longer run.

With that I am saying run more PV panels with smaller battries, but use all the power during the day and only use minimal power at night.

 

With a bi-directional invertor, you should be able to charge the battries via the genset.

Most gensets have a 12/24V DC output, but it is normally limited to 8Amps. (100w to 200w)

When using the genset 230V AC output and running a bi-directional invertor, you should be able to use the full power of the genset to charge the battries.

 

Perhaps you might even look at getting a remote start genset? You can then start the genset automatically when your battries is running low.

It does increase the system complexity a bit, but it would enable you to go for a higer system voltage and decrease the battery bank AH capacity.

If cost is such an issue, with the above changes, you could even look at using truck battries, but you propably going to have to replace them every 3 to 5 years. You would also put on more hours on the genset this way.

 

There is nothing wrong with Outback, Oasis and MLT, but they extremely expencive.

I like Microcare as their prices is good and they based in PE.

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Thanks for the guidance.

 

Yesterday I also realised that my attraction to M-Solar batteries and trying to limit the capital outlay will get me stuck with 24V. Let us try and move a little wider then.

 

  • If we decide to look at more than the Raylites, what batteries would you recommend then so that the system can run on 36V or 48V DC? Somehow my thinking is that "goedkoop koop is duur koop" as far as the batteries is concerned. I've actually got a transport business, and truck batteries are a weak link in our industry, but I'm not saying that they will not be a feasible solution in this application. They just seem to finally greet the living amongst us the moment "deep cycle" is mentioned in their presense. We can obviously try and avoid them cycling too deep.
  • It seems that an Outback 80A controller would cost less than R9 000. That's still acceptable.
  • We can run a MicroCare 5kW inverter off 36V or 48V. R20 000 still seems fair. Can the MicroCare inverter charge the batteries from external 220V like a generator?
  • I'd like not to exceed R50 000 for the batteries, less if at all feasible.
  • Is there an 80A MicroCare MPPT controller?

Maybe a last question: If you've got R90 000-R100 000 to spend, what will be on the back of your bakkie and trailer leaving the green shop?

 

Thanks for your input, it makes life interesting.

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  • 4 months later...

Hi SR

 

I've started buying some of the components, as I'll only need the system operational by August.

 

I've bought some solar panels, the charge controller (100A M/C) and the inverter (5000W M/C). I'll buy the batteries closer to the time. I bought more pv than what I need for the house, but there's still a borehole to get equipped as well.

 

GW store supplied.

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Hi SR

 

I've started buying some of the components, as I'll only need the system operational by August.

 

I've bought some solar panels, the charge controller (100A M/C) and the inverter (5000W M/C). I'll buy the batteries closer to the time. I bought more pv than what I need for the house, but there's still a borehole to get equipped as well.

 

GW store supplied.

Nice 

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Hi W

 

Thanks for the encouragement. I need that, and a lot more. I'll give you a shout closer to the time of construction, somewhere after winter.

 

I've bought:

  • Sunpower 300W 50V panels.(16)
  • a MicroCare 100A controller
  • a MicroCare 5000W Bi-directional inverter.

There's too many panels for the house. The recommendation is for 6 panels, but I made use of the good offer at GW Store for the panels. At R6/W (plus VAT) I thought it good to buy some extra. We hope to get consent from the authorities to also put up some guest/weekend chalets in future. I'd like to make them work off the grid as well. Then there's still the borehole. I haven't got final answers about that, but some of the panels will do duty there.

 

The system voltage will be 48. You agree?

 

I haven't decided about the batteries yet. Would like them M-Solar's, but I'll need  a very special "special" to buy 500Ah of those. I'm impressed by what I learn about the batteries of electric forklifts. It seems that their DoD/lifespan ratio is extremely good. It would seem that one could save R20-R30k on the battery bank going that route. They are just far from maintenance free. They need water frequently.

 

The plan is to put the panel structure on the ground, not on the roof. I believe that they can heat up on the roof, influencing their output. Our house will get a flat roof, so it can make sense not to put them there. Like most other users, I've got a bag full of plans to make the panels follow the sun, but I don't know if I'll have decent success.

 

 

I would still like to add a 1kW wind turbine at some stage. I just need to sell the farm first to be able to pay for that. ;)

 

What else must I know?

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Hi Jakes

 

Living off grid have a lot of challenges. From my experience you will have to also build a small 12Volt system as a back-up to the big system. That said, hot water in winter can be a problem. If suggest you try a low pressure solar geyser and a some type of a metal fireplace i.e jet master. You can place a radiator (from a car made of aluminium) a half inch in an enclosure behind the fireplace, this will allow you to use the radiator reverse to what is is being used for in a car. You will be able to heat water while heating up your home with the fire place. The piping is fairly easy, you will be needing a few one way valves.

 

Wind turbines are far less efficient then solar. The problem with wind turbines are the charge controllers. If you do get a turbine put is 12 meters high and get a PWM controller and you will harvest the power from all gust winds more effective.

 

Hope this information will assist you in your off-grid system. 

 

Off Grid the way to go :)

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With regards to your battries....

Is the forklift battries Trojan perhaps? Very good and reliable make.

I have seen installations where they put up 25L drums of distilled water and run piping to each battery.

This way you can top-up each battery without any hassels.

Just make sure you have a "dedicated" battery room that is well ventilated and do not get like a sauna in summer.

Heat is one of the biggest killers of battries.

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Hi Regie

 

Thanks for the advice. I'll bare in mind.

 

We have been using a low pressure solar geyser for the last 3 years, where we currently live.  It uses a little electrical help, but has saved us a lot. We have made most of the necessary lifestyle adjustments. We're prepared for some more when we move down to the WesternCape.

 

It is our intention to install a stove. The design of our house asks for a centrally mounted one. I've done some reading on a "wet stove", but was not seriously considering it. Maybe I should re-consider.

 

Wk

 

I popped into CPR batteries in Brakpan to start gathering info. They manufacture forklift batteries. I will do some more homework on using a forklift battery. If somebody in the meantime knows about a supplier who could give a decent price on a bank of M-Solar's of 600Ah at 48V, I'll make a plan to rob the other bank for them.

 

Some time ago I bought a couple of kW-hour meters to measure the consumption of some of our appliances. Some information gathered:

  • Double door LG fridge/freezer, 560l, nothing indicating that it's a very "green" appliance. Opened a couple of times a day, serves a family: Measured over 138 summer days - 1.48kWh/day.
  • Bosch freezer, 260l, opened maybe once a day. Measured over 119 summer days - 0.96kWh/day.
  • Samsung bar fridge, 120l, opened maybe once a week. Measured over 119 summer days - 0.29kW/day.
  • Bosch dishwasher. We use its 35
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