Solar to 220V … what happens ?

[ChrisF]

Solar to 220V … what happens ?

With load-shedding a reality many people are considering their options.

So technologically speaking, what options are available to carry on as normally as possible during load-shedding? The answer depends on the time of day and WHAT you need 220V for. So what do we need power for:
- Bath\shower – solar hot water, PV element system, or even a gas geyser are real options.
- Stove – gas is the obvious alternative
- Kettle – camp kettle on your gas stove
- Lights – camp lights, or 12V LED’s fed from a battery
- Fridge\freezers – THIS is certainly the most challenging item. Fortunately it CAN survive a classic 2 hour load shed without any issues. For longer power outages a generator would be the ideal alternative source off energy. Should you wish to power this from batteries and a solar system it would require a MASSIVE inverter, purely due to the large starting currents.
- Then the multitude of electronic devices in the modern home and office, from tv’s to computers. Traditionally speaking an UPS was used for such devices, for the odd power failure. Sadly the typical UPS is NOT up to the task for rolling load-shedding.

This write up will NOT deal with gas, nor with generators, nor with UPS’s, but rather look at the basic maths should a person consider going the road of PV panels and inverters to power their electronic devices.


I have sent a pdf version to Pieter and asked him to post it here :)

[ChrisF]

Electricity BASICS

What is “AC” ?

What is “DC” ?

Consider an electrical circuit with a “battery” as power supply and a lamp :



DC circuits - If you monitor the Voltage across the lamp over a time period you will find this remains constant -





You find the exact same straight line when you monitor the current flow through the lamp. (for the purists – please lets consider the battery to remain full and let’s ignore the temperature effect of the filament on the current flow)

For this DC (direct current) circuit there is one formula we will use :
Power = Voltage x Current
P= V x I

Thus your 36W fridge will draw the following current when connected to a 12V battery:
"I = " "P" /"V" " = " 36/12 " = 3 A"
Thus DC circuit calculations are pretty straight forward.

[ChrisF]

AC Circuits - An alternator is basically a rotating device where wires are moved past magnets, thus inducing a voltage into the wire. When the wire moves parallel to the magnetic field ZERO voltage is induced. On the other extreme maximum voltage is induced when the wire moves at exactly 90 degrees to the magnetic field. As the wire rotates the induced voltage ranges from zero to maximum and then back to zero in the form of a sine wave, then onto a maximum negative value. The number of full revolutions in one second is called the frequency, in Hertz. In South Africa Eskom sometimes supplies us with an average voltage of 220V at a frequency of 50Hz. (those that have bought electrical items in America have discovered the Yanks use 110V and 60Hz)





It is about now that the plot THICKENS !! For the purposes of this document there are TWO types of AC loads:
- Pure resistive loads – the kettle element
- Inductive loads – this cause a “power factor” (pf)
Let’s assume a power factor of 0,9 for the electronic devices in your home\office.

This “power factor” means that the power formula for AC circuits looks like this:
Power = Voltage x Current x pf
P= V x I x 0,9


Okay … let’s keep this SIMPLE (well as simple as possible, without causing the purists too many heart attacks)

For the purposes of this discussion let’s just work with the “VA” rating of the AC devices, thus Power divided by 0,9 for the electronic items.

[ChrisF]

Let’s start

Okay with some basics in place, lets look at some applications.

Solar panel on the roof. Some super dooper solar regulator charging your battery of choice. So you HAVE electrical energy, and connect your inverter to the battery, magic happens inside the inverter and you have 220V to power your devices …..Wooowwwww, hold your horses !! TWO more things to understand before using that 220V :

- Efficiency – in primary school science class we were taught that energy can not be created nor destroyed, but merely transformed from one form to another….. Somehow at that level they did not see fit to tell us about “energy losses” – each and every time you convert power to another form there are losses ! An inverter that converts power from 12V to 220V is typically about 90 to 95% efficient.

- Inverters DON’T have rotating shafts like a generator, and thus does not naturally deliver a pure sine wave. Instead it uses some very fancy electronics to create a wave form which attempts to mimic a sine wave. The early models tried square waves, then came up with something that resembles a triangular wave. Today the very expensive units produce a “pure sine wave”, well something very close to it. The shape of this wave is important to the power supplies of electronic devices, and incredibly important if you intend powering electrical motors.

[ChrisF]

Example 1 –
So your Canon 5D3 camera battery charger requires 10W at 220V.

Allowing for the inverter losses (lets for now just work on 90% efficiency ignoring how this changes with the size of the load)
Power from the battery= "Load Power" /"Efficiency" = 10/0,9=11,1"W"

If the battery has a voltage of 12,5V, the current draw from the battery will be :
"I = " "P" /"V" " = " 11,1/12,5 " = 0,889 A"

Remember your classic 105A.h battery has about 50A.h that can be used without any negative effect on the battery. Drain the battery more than 50% and its number of charge cycles are reduced.

Thus you could charge camera batteries for about 55 hours.

PS – the battery voltage should be somewhere between 12 and 13V depending on the SOC.

Example 2
Your notebook charger requires 37W at 220V.
Power from the battery= "Load Power" /"Efficiency" = 37/0,9=41,1"W"

If the battery has a voltage of 12,1V, the current draw from the battery will be :
"I = " "P" /"V" " = " 41,1/12,1 " = 3,4 A"

So you can charge you notebook a number of times, with a total charge time of 15 hours.

[ChrisF]

Example 3
This time you are taking your 17’’ DELL with on safari and need 215W at 220V. HOWEVER, DELL does not spell out that this power is pushed to the absolute maximum when you charge a flat battery AND use the laptop at the same time. So now you need that full 215W for a few hours.

NOTE – most inverters have a “maximum rating” and a “continuous rating”. Most often the latter is NOT spelt out clearly, but rather the max rating.
Power from the battery= "Load Power" /"Efficiency" = 215/0,9=238,9"W"

If the battery has a voltage of 11,8V, the current draw from the battery will be :
"I = " "P" /"V" " = " 238,9/11,8 " = 20,24 A"

Okay, time for a wake up call !!

The wires and circuit breakers supplying your home plugs are limited to only 15A !! You need SERIOUS wiring to run 20A for 2 or 3 hours at a time !!

The second problem is with the classic “500W inverter”, where they conveniently place the actual continuous rating on the back of the unit in small print. And now you have the acid smell of hard working electronics hanging in the camp ground as this inverter struggles to charge the laptop !

Problem three …. So you work on the laptop checking your photos while it is being charged so for the next three hours your laptop charger works at max ….. 20 amps for 3 hours is 3 x 20 = 60 A.h !!! If you did this next to the camp fire you may well find your battery LOW tomorrow morning !!

Result:
Nice pics on your laptop
Laptop charged and ready
Coals dead because you were too busy with your pics …
Mommy with a long lip ……
And it is late afternoon and you have just taken your 2nd battery so low that your National Luna cuts out on its safety setting !!!

Oops, all this talk of solar had me at the camp there for a moment. And this is supposed to be about your HOME PC – that draws MORE power ….

The next two examples will look at what it takes to run the home PC, and also what it would take to run the DStv and flat screen during a load shedding.

[ChrisF]

Example 4 – PC
So how much power does your home PC actually draw ? Do you blindly add all the power specs ? Before answering look at this pic, this is a quad core high spec machine with dual screen setup, and exporting a large number of photos in Lightroom, thus WORKING –



Remember the Power formula for AC : P= V x I x 0,9 = 235 x 0,73 x 0,9 = 154 W.
NOTE – we will be using the “VA” values in our calculations, thus 235 x 0,73 = 171,6 VA

This for dual screen computer that is working hard.

Power from the battery= "Load VA" /"Efficiency" = 171,6/0,9=190,7 "W"

If the battery has a voltage of 12,5V, the current draw from the battery will be :
"I = " "P" /"V" " = " 190,7/12,5 " = 15,25 A"

This may not sound like a lot of current, but this is a mere 3 hours for ONE PC from a 105A.h deep cycle battery !!!!
 
BUT, look what happens when you want to print –

P= V x I = 235 x 0,73 = 748 VA. And I was just too slow with the camera to catch the printer at about 1 000 VA !!!

Power from the battery= "Load VA" /"Efficiency" = (1 000)/0,9=1 111,1 "W"

If the battery has a voltage of 12,5V, the current draw from the battery will be :
"I = " "P" /"V" " = " 1 111,1/12,5 " = 88,9 A"

Even though this will be for a few seconds only you now need a SERIOUS inverter !!!!!

[ChrisF]

Example 5 – DStv and the flat screen
And finally the one that any boer seun wanted to know – what is needed to keep the flat screen going to watch the oval ball.

DStv decoder + video machine + 42’’ flat screen = 188 W, with a power factor of 0,9 the VA is 209VA.

Power from the battery= "Load VA" /"Efficiency" = 209/0,9=232,2 "W"

If the battery has a voltage of 12,5V, the current draw from the battery will be :
"I = " "P" /"V" " = " 232,2/12,1 " = 19,2 A"

That deep cycle should just be able to do the job, as long as the load shed does not axceed 2,5 hours. But then, for the game the battery WILL be drained lower if needed ….

[ChrisF]

Example 6 – Garage door opener
Nothing like having a large garage door, nicely automated, and just as you are about to go to work Eskom decides to declare you a “previously lit area” …. Now your door does have a back-up system, a chain that takes a few minutes to open, and then again another few minutes to close.


The motor is rated at 600W.

So we try my standard inverter … no go …

Next we try a 1600W inverter, with a continuous rating of 800W …. No go …. Remember a few pages back I spoke about the type of wave that the inverter puts out. This MOTOR wants a pure sine wave ! That and the inrush current it takes to start up a motor.

We then got a test unit from a Forum Commercial Member, a 3 000W inverter with a continuous rating of 1 500W. This unit is a PURE SINE WAVE unit. (Commercial is awaiting stock before I may post more details…)

It drives the door motor 



Power from the battery= "Load VA" /"Efficiency" = 580/0,9=644,4 "W"

If the battery has a voltage of 12,8V, the current draw from the battery will be :
"I = " "P" /"V" " = " 644,4/12,8 " = 50,3 A"

It takes 28 seconds to open the door, and another 28 seconds to close it. Thus about 60 cycles for the 105 A.h battery.

[ChrisF]

Time to recap

Up to this point it was an interesting experiment. But now it is time for a SERIOUS DISCLAIMER !!

- Batteries give off HIGHLY explosive gas during a charging cycle !!!!!!!
- DON’T do this inside the house or in any enclosed area where the gasses may build up !!!!!!!
- Battery rooms are well defined in the Building Regulations, and ventilation requirements have been Gazetted. An illegal installation may well VOID any insurance you have !!!!!!
- Electrical installation work SHOULD be done by an electrical contractor that CAN provide you with a COC.
- The purpose of this article is purely academic, to assist you in planning an alternative power system. This is NOT an installation brochure !!!!!

Based on current prices, and the uncertainty of power supply, and the fast pace of change in the field of alternative energy sources I am taking a conservative approach.

One needs to be able to continue with a reasonably normal life, thus:
- Lights – a camping light is all we need for now. But adding some LED lights are easy enough, and should use only a couple of A.h per day.
- Food – for now our gas bottle and cooker top is on stand by. Should the system deteriorate further we will buy a gas stove. Same for coffee, our camping system is good enough for now.
- Bath/shower – the geyser has enough capacity to carry us through a load shed. I may consider a PV retrofit unit at a later stage, depending how the process unfolds.
- Fridge/freezer – this is the one item can turn costly in the long run. For the standard load shed it should be no issue. But if we are facing extended power outages all bets are off !! Cheapest solution would be a generator.
- The electronic devices may well be considered a luxury, a luxury we could do without. But there is a fine line between luxury and quality of life …. A friend has his load shed schedule just after the kids goes to bed, without additional power his quality of life will be impacted if we get the type of continual outages that Eskom is predicting.

I am NOT going to get into a debate of Generator vs Solar and battery. This certainly is a debate with many factual and emotional key points ….

Should you wish to power your electronic devices from a solar and battery system, here are a recap of some basic numbers :

DStv + video machine + 42’’ flatscreen = 20A from your battery, thus 2,5h from a 105A.h battery
BUT, you KNOW what is going to happen …. You WILL be powering the kids tv as well …. So suddenly a 2 hour load shed will push your 105A.h deep cycle past its magic 50% SOC !

PC = 15A from the battery, thus 3,5h from a 105A.h battery
BUT, you are going to need a serious inverter to drive the printer

What size inverter ?

What type of inverter ?

Goed koop koop is duur koop. Buy big and get done the first time !

A 3 000W inverter with a 1 500W continuous duty should be the smallest unit you consider. And while you are it, get the pure sine wave model. Now you need a couple of batteries depending on what you want to run, and for how long.

Let’s say a small home office with three PC’s, thus 45A. One of 105A.h battery will only give you just more than one hour back-up. In terms of inverter size a single printer and three PC’s will already exceed the capacity of the 3 000W inverter with a 1 500W continuous duty unit !!

Side note – also consider rather buying a laptop instead of your next PC …

[Mr_B]

Chris, once again an extremely informative piece of work! This is exactly what I've been trying to figure out in my head. Do you prepare for the daily loadshedding 2.5 hours(solar+batt+inverter) or do you prepare for the worst case scenario of a longer outage(generator+fuel+fuel+fuel). I'm not persuaded that we won't have longer outages in the near future.

Of course a large size (say 5.5Kva) generator can cover you for both, but at what cost? Add to that the fact that electricity supply tariffs are about to rise sharply and the cost fuels(diesel and petrol) are dropping sharply and it all gets even more confusing.

I've been told that you need to multiple a device like a fridge/freezer's wattage by 6 to get an idea of the startup current requirement. Is the 6x factor correct?

Thank again!

[Mr_B]

A 3 000W inverter with a 1 500W continuous duty should be the smallest unit you consider. And while you are it, get the pure sine wave model. Now you need a couple of batteries depending on what you want to run, and for how long.

3000W inverter = R 20,000...

Well there goes 2x my project budget in one go!

1500W inverter = R 8,500...

Maybe a generator isn't that expensive after all!

[ChrisF]

Chris, once again an extremely informative piece of work! This is exactly what I've been trying to figure out in my head. Do you prepare for the daily loadshedding 2.5 hours(solar+batt+inverter) or do you prepare for the worst case scenario of a longer outage(generator+fuel+fuel+fuel). I'm not persuaded that we won't have longer outages in the near future.

Of course a large size (say 5.5Kva) generator can cover you for both, but at what cost? Add to that the fact that electricity supply tariffs are about to rise sharply and the cost fuels(diesel and petrol) are dropping sharply and it all gets even more confusing.

I've been told that you need to multiple a device like a fridge/freezer's wattage by 6 to get an idea of the startup current requirement. Is the 6x factor correct?

Thank again!

Thanks B

I think the CAPE is in for FUN !! Apparently one of the Koeberg units is due to go off line for maintenance shortly .....

With the last round of load shedding we had TWO sessions per day, each 2 hours.


Thanks to our camping gear it was not a major issue for us.


My laptop battery last the time, and my reads a book .....


but my mind IS going over the options ....



My neighbour is an electrical contractor and we tested the inverter at his house. He also did a PV geyser retrofit on Friday, jip today is the 2nd day that we are testing his new geyser system - in the cloudy weather !! Working perfectly !! Sorry going off topic.


I am considering a deep cycle on a trolley, solar/220V charging, then a brad harison to connect it to my tv UPS. The UPS is purely to protect the tv against surges in eskom power, can only power the tv for a few minutes - just enough for me to get the battery ....

[ChrisF]

A 3 000W inverter with a 1 500W continuous duty should be the smallest unit you consider. And while you are it, get the pure sine wave model. Now you need a couple of batteries depending on what you want to run, and for how long.

3000W inverter = R 20,000...

Well there goes 2x my project budget in one go!

1500W inverter = R 8,500...

Maybe a generator isn't that expensive after all!

HANG IN THERE !!!!!!!!!!!!!!!


soon you will be able to get a pure sine wave 3000W inverter with a 1500W continuous duty for a DECENT PRICE !

WATCH THIS SPACE !!


Daai man beter solank nog n container bestel ...

[Mr_B]

I've done the solar evac tubes(36) thing... with 2x 150L kwikot geysers... I know it's summer but the system is working superbly. Electricity bill has dropped by R1000 in the first month. I guess if you going green... keep going green! I've got 100ltrs of Engel camping fridge/freezer to help out should Eksdom pull the plug a little longer...

Keep me posted on that inverter... asseblief!

[Mr_B]

Chris, for the budget constrained amongst us... what do you think of investing in a decent 220v charger, say 1 x 200ah deep cycle battery and a decent inverter to start with, without the solar panels. The charger can charge the battery bank off the Eksdom grid and the supply via the inverter during loadshedding. Then as budget allows you can add solar PV panels to take over from the 220v grid charging. That way I could buy a better battery(capacity wise) and a better inverter to start with??

Would you need a special charger or would something like a Benton BX2 do?

I thought a battery something like this could be handy: http://www.gwstore.co.za/site/store/ind ... uct&id=938" onclick="window.open(this.href);return false;

B

[ChrisF]

Chris, for the budget constrained amongst us... what do you think of investing in a decent 220v charger, say 1 x 200ah deep cycle battery and a decent inverter to start with, without the solar panels. The charger can charge the battery bank off the Eksdom grid and the supply via the inverter during loadshedding. Then as budget allows you can add solar PV panels to take over from the 220v grid charging. That way I could buy a better battery(capacity wise) and a better inverter to start with??

Would you need a special charger or would something like a Benton BX2 do?

I thought a battery something like this could be handy: http://www.gwstore.co.za/site/store/ind ... uct&id=938" onclick="window.open(this.href);return false;

B

Ja nee ....

JA - it IS possible.

NEE - the way I look at it there are TWO issues that needs consideration
1) a battery room MUST be ventilated ....
2) HOW do you intend using the power ??????


This second item is NOT an easy one to answer !!!!!!!!!!!!!!!!!!!!!!!!!!!

Running a split DB in a house is going to COST you !!

so now you add extra light circuits .... ugly ....


tv in one room, computer in another ... so how do you connect this to your battery bank ??


I can just see the spagetti of extention leads ....


And with a FULL solar going for about R250 000 very few will go this route .... so now to find a workable partial system ....

[pietpetoors]

Thanx a million Chris, that is a very good writeup.

Here is the attachment Chris asked me to load.

Solar to 220V.pdf

solar to 220 volt

(922.11 KiB) Downloaded 117 times

[stephanvaneeden]

Chris, wat sal 'n ou nodig hê om 'n 750 watt swembadpomp vir so 2 na 3 ure in die dag te laat hardloop, en sal dit die moeite werd wees. Ek dink daaraan om als so stuk vir stuk van Eskom af te haal. ( son panele na inverter ).

[george]

Excellent work Chris .

[ChrisF]

Chris, wat sal 'n ou nodig hê om 'n 750 watt swembadpomp vir so 2 na 3 ure in die dag te laat hardloop, en sal dit die moeite werd wees. Ek dink daaraan om als so stuk vir stuk van Eskom af te haal. ( son panele na inverter ).

Stephan jy lees my gedagtes ...


Ek is juis nou besig met n swembad installasie by die huis.

Die swembad pompe wat direk van solar af loop is NET te duur !! 25 tot 30k !! EN dan is die 300W pompe wat te lig is om die werk te doen !!


So ek sit nou n 750W pomp in.

Die installasie behoort laat Februarie klaar te wees. Ek sal dan daai lekker sinus golf inverter TOETS :) :)

Ek HOOP dit sal werk .... selfs al moet ek dan die 2kW continuous duty inverter gebruik.

Dink so 500W se solar panele wat oor n gemiddeld van 6 uur laai, en trek dan 750 vir 3 tot 4 ure ....


Ek sal beslis toets en laat weet of ek dit kan laat WERK.


Groete

[stephanvaneeden]

Dankie man, daai is my presiese denk rigting, het 'n onnodige groot motor in. Wil hom vervang met 'n 750 W en daai tipe instelasie doen sodat hy op sy eie funksioneer. Wat reken jy sal die kostes uitwerk op daai tipe inverter ?

[zepplin]

Great explanation & write up Chris. But could you slow down a little with all the new info so us lesser mortals can digest?

[Hilux 1]

Great explanation & write up Chris. But could you slow down a little with all the new info so us lesser mortals can digest?

+2

kan net konsentreer vir 2 lyne op n slag. en dan skrik die formulus my ook nog af

[WayneSchalk]

It puts it all in perspective :?

I got my inverter, 4000w pure sign wave, and at least 2 x 102Ahr to start with. I will be running my lights, all LED. And a coupe of dedicated plugs for the TV, fridge, alarm and electric fence.

I'll do the math and total cost once all is done. I'd better get going this weekend

[ChrisF]

Great explanation & write up Chris. But could you slow down a little with all the new info so us lesser mortals can digest?

+2

kan net konsentreer vir 2 lyne op n slag. en dan skrik die formulus my ook nog af

hehehehe .....

Skip to the 7th post - nice recap ... :)

[Rian]

Interesting subject.

I have seen 180w Solar panels at Chinese mall Zambesie Pretoria for R1800-00 each. What do you guys think about should I try it? Or do you get better deals somewhere else?

[ChrisF]

Interesting subject.

I have seen 180w Solar panels at Chinese mall Zambesie Pretoria for R1800-00 each. What do you guys think about should I try it? Or do you get better deals somewhere else?

was waiting for the price war ...


For a few years the "cheap" imports were going for R12/W ....

SA's first solar manufacturer came on line late last year, selling at R12/W ....


chinese MUST drop in price to sell .......

[stephanvaneeden]

Kyk GW Store, en Bushpower se pryse.

[pietpetoors]

Because there is so much competition in the market, the markup on solar panels is very small.
The factory in CPT actually increased their prices this year, we decided to stay on the old price for now.

I am not sure if it will drop much further.
If I look at the size and weight of those panels, pretty much about 40% of the price you pay must shipment and VAT on imported ones.

As for the CPT factory, we all know what minimum wages and red tape does to production cost, thank the anc for the high prices we have to pay for the products.

[Hunter26]

Sorry for the hi jack. I see people are going for 180w solar panels to charge a 100ah battery. Why can't a 60w or 90w panel do the job since a battery charges at 14v as an average. Lastly is there a formula to work out panel wattage needed to load draw. Ie panel size to charge battery etc. Newbie to this. Thanks


Craig

[ChrisF]

Sorry for the hi jack. I see people are going for 180w solar panels to charge a 100ah battery. Why can't a 60w or 90w panel do the job since a battery charges at 14v as an average. Lastly is there a formula to work out panel wattage needed to load draw. Ie panel size to charge battery etc. Newbie to this. Thanks


Craig

160 W panel (2 off 80W) laying flat dont often exceed 10A !! This is at a charge voltage of 14V.

Thus MOSTLY it does not exceed the 10% rule - old rule of thumb to not exceed a charge rate of 10% of your battery capacity ....



but YES, a much smaller panel will do the job - DEPENDING on your load !!!!

The solar MUST put in more than your load or you will end with a flat battery ....

[Hangover]

Sorry for the hi jack. I see people are going for 180w solar panels to charge a 100ah battery. Why can't a 60w or 90w panel do the job since a battery charges at 14v as an average. Lastly is there a formula to work out panel wattage needed to load draw. Ie panel size to charge battery etc. Newbie to this. Thanks


Craig

Hi Craig

You can charge a battery with a 5W solar panel if you want to... It is all about time you have to charge to use the power at night... you can calculate using roughly 5.5hours of sunlight at "full power" if you take reduced "power" (or what we can call solar radiation) into account in dusk and dawn times... So by having 150W panels at 90% (which is normal losses for charger panel etc) you charge 135Watts per hour or roughly 11AH at 12V... Thus by having 50Ah of usable battery power on a 105Ah deep cycle you can charge the battery to max capacity within a day(5.5x11 = 60Ah) if the sun and clouds play along... So once again you need to go through all the steps chris explained to calculate the panel size to charge rating...

[Mr_B]

Is a 250w panel overkill to charge a 200ah battery?

Specs for the 250w panel:
*Power Tolerance: +/- 3%
*Min Power: 246W
*Voltage at Max Power (Vmp): 29.80V
*Current at Max Power (Imp): 8.10A
*Open circuit Voltage (Voc): 37.00V
*Short Circuit Current (Isc): 8.90A

The thought is to pair this panel with a 200ah battery, a 20 amp MPPT solar charge controller(LED display) and a 1000w pure sinewave inverter.

Is this an acceptable combo?

[ChrisF]

the battery-pv panel combo sounds correct.


the size of the inverter is a totally different story !!


you could decide to use that to drive a 100W load for multiple hours - with a small inverter.

OR - should you decide this is for your pc and printer .... well the printer (laser unit) alone will push you towards a substantially larger inverter, just to deal with that initial spike when the laser heats up ....

[Mr_B]

the battery-pv panel combo sounds correct.


the size of the inverter is a totally different story !!


you could decide to use that to drive a 100W load for multiple hours - with a small inverter.

OR - should you decide this is for your pc and printer .... well the printer (laser unit) alone will push you towards a substantially larger inverter, just to deal with that initial spike when the laser heats up ....

Thanks Chris.

To be honest the cost of the inverter is the killer... the 1000w one I'm looking at is R5,390.00 already. It does have a surge capacity of 2000w... does that helps a bit?

In terms of future scalability... I wonder if it's better to start with a bigger inverter and smaller solar+battery combo? Obviously on a small budget I would like to try buy components wisely. I can imagine as a system grows, so will your components have to keep up, especially the charge controller and inverter!

[ChrisF]

the battery-pv panel combo sounds correct.


the size of the inverter is a totally different story !!


you could decide to use that to drive a 100W load for multiple hours - with a small inverter.

OR - should you decide this is for your pc and printer .... well the printer (laser unit) alone will push you towards a substantially larger inverter, just to deal with that initial spike when the laser heats up ....

Thanks Chris.

To be honest the cost of the inverter is the killer... the 1000w one I'm looking at is R5,390.00 already. It does have a surge capacity of 2000w... does that helps a bit?

In terms of future scalability... I wonder if it's better to start with a bigger inverter and smaller solar+battery combo? Obviously on a small budget I would like to try buy components wisely. I can imagine as a system grows, so will your components have to keep up, especially the charge controller and inverter!

PLEASE wait a couple of weeks !! PLEASE !!!!!


unfortunately cant say much more at this stage ,,,, sworn to secrecy and all that ....


maar so tussen ons dames van die tee klub - HOPELIK einde Februarie, moontlik einde Maart ..... maar die manne WEIER om iets te sê tot die container hier gedock het ....


so please wait ......

[Mr_B]

PLEASE wait a couple of weeks !! PLEASE !!!!! unfortunately cant say much more at this stage ,,,, sworn to secrecy and all that ....

maar so tussen ons dames van die tee klub - HOPELIK einde Februarie, moontlik einde Maart ..... maar die manne WEIER om iets te sê tot die container hier gedock het ....

so please wait ......

Ok Chris... I'll instruct Eskom to hold back on the loadshedding... lol!

Good things come to those who wait!

[stephanvaneeden]

Okay nou verstaan ek ook die stilte agter die swembad projek.

[ChrisF]

Okay nou verstaan ek ook die stilte agter die swembad projek.

manne het gister my bad gepleister ..... nou so drie weke voor hulle hom kan glasvesel.

so die swembad pomp eksperiment sal Maart begin ....


intussen toets ek solak n paar ander goed .... maar mag nog niks se nie ....

[Mr_B]

Okay nou verstaan ek ook die stilte agter die swembad projek.

manne het gister my bad gepleister ..... nou so drie weke voor hulle hom kan glasvesel.

so die swembad pomp eksperiment sal Maart begin ....


intussen toets ek solak n paar ander goed .... maar mag nog niks se nie ....

I've got a pool with 0.75kw pump... you welcome to experiment at my place for now!

[ChrisF]

Okay nou verstaan ek ook die stilte agter die swembad projek.

manne het gister my bad gepleister ..... nou so drie weke voor hulle hom kan glasvesel.

so die swembad pomp eksperiment sal Maart begin ....


intussen toets ek solak n paar ander goed .... maar mag nog niks se nie ....

I've got a pool with 0.75kw pump... you welcome to experiment at my place for now!

mmmmmmmm tempting ....


how is your pool wired ??

permanent to the house DB OR plugged into an external wall socket ?


Mine will be installed with and externa plug - specifically to allow for the testing ...

[Mr_B]

I've got a seperate DB board in the garage for all "outside" circuits(pool, workshop and lights)... at the pool pump itself there's 2 plugs, one for pump and another for the chlorinator unit...

So testing should be possible... if you need to tweak and hack that's fine too!

[ChrisF]

I've got a seperate DB board in the garage for all "outside" circuits(pool, workshop and lights)... at the pool pump itself there's 2 plugs, one for pump and another for the chlorinator unit...

So testing should be possible... if you need to tweak and hack that's fine too!

Bretton we are away this weekend.

Let's try to set up something for next weekend :)

[Mr_B]

I've got a seperate DB board in the garage for all "outside" circuits(pool, workshop and lights)... at the pool pump itself there's 2 plugs, one for pump and another for the chlorinator unit...

So testing should be possible... if you need to tweak and hack that's fine too!

Bretton we are away this weekend.

Let's try to set up something for next weekend :)

Cool... I'll PM you my cell num.

[ChrisF]

Thanks Mr B.

Was nice meeting you. and thank you for providing us with an opportunity to play a bit ....


For the benefit of those that were not in attendance -

the 1500W PSW inverter did run the 750W pool pump - BUT, it took three tries to do so. The first two times it could not start the pump. Seems this size inverter is JUST too close to the limit during start-up.

I had placed a load on the battery earlier in the day to deliberately lower the SOC.

Thus the 65A draw from the battery managed to push the battery LOW in about 20 minutes !!! The inverter tripped out, started the most irritating squelling, and kept on squelling until I turned it off. Even though I moved the bakkie into the sun and the solar panels had lifted the voltage of the battery the inverter required a manual reset - GOOD :)



Conclusion - I happily use the battery and inverter combo to drive my DStv and TV during a load shed. But if you wanted to use this for a pool pump, I would seriously recommend solar panels to suit the load, thus the effective current from the battery would be minimal .... the concept sounds okay, until you start looking for a regulator to push 70A into a battery !!


THIS is why larger systems work on 48V battery banks - which in turn means much lower amps. But now you are moving into industrial systems, and expect to PAY !!



PS - to be CLEAR - I do believe the inverter is VERY GOOD !! I will be buying one for myself. For longer use I would not recommend exceding 300 to 400W. Even though I DID use it to power my 750W Makita rotary hammer for drilling three holes into facebrick ! JIP, this has potential for small DIY jobs where power is not available .... SO TEMPTED to try my inverter welder on it ... Think about it - less than 60 seconds of total welding time for a bush repair ....

[pietpetoors]

On the weekend we tested the CPT branch's inverter setup.
We installed the same make of inverter as Chris, but the 2500 watt version.
We run it on one of the un-sealed Dixon batteries which we sell in the shop.

We were concerned that maybe the setup will not outlast a load shedding period and tested it to see if our system will work.
We also wanted to see if the low battery protect system will only sound an alarm or switch it off.

We have on it
1x PC with LED monitor
1x PC - monitor turned off (it is our server)
1x D-link wireless router
1x Credit Card machine
1x Laptop
2x HP Laser printers
1x Cordless phone base (phone was already charged but base still needs power)

Note the lasers pulls about 1000 watt on startup , but only takes 3 or 4 seconds to print a page.
We only printed about 26 invoices for the morning.

The battery was fully loaded.

We switched it on at about 08h20
By about 13h50 the alarm sounded and the battery was on 11.55 Volt then.

That was more than 5 hours and we were pleasantly surprised by the performance.
So we know our business will be up and running during load shedding.

We have a very simple system, we have the battery, with inverter connected to it and we connected a Benton BX-2 to the battery.
Once power comes back on, the Benton will charge the battery.

Our server has one of them cheap UPS systems which powers it for about 10 minutes just to give you time to switch it off.
So our main inverter is not switched on all the time.
If power goes off, the server is still running on the UPS. That gives us time to unplug the multiplug's plug and plug it into the main inverter and switch the main inverter on.

I've plugged everything we have to run on the inverter into one multiplug
Thus we only have to switch one plug to power things up again.

Because the server runs on the small UPS, once power comes back on again we can unplug from inverter and plug into mains again.
It is only the PC at the till which we need to shut down and start when we do the switchover. But those small UPSes are only about R800 so I am considering getting another one for the till PC as well.

PS. I know one can unplug the laptop because it has its own battery, but we deliberately kept the laptop plugged in to get the worse case results.

[ChrisF]

got some better test equipment, and started pushing the limits of what the UPS can do ....


TV - the most common question now is how to power a DStv and TV during a power outage.

Our system draws about 160 to 170W.

I connected the PSW inverter to the battery in the bakkie, ran a lead in and powered the tv system from this ..

1 DStv (Small).JPG (36.01 KiB) Viewed 4628 times

Left running for a bout 20 minutes. works like a charm !!



The rig was still setup on Saturday morning ... so I ran the lead outside for the 750W Rotary hammer drill !!

Truly did not expect too much.

1 boor (Small).JPG (52.3 KiB) Viewed 4628 times

3x 6mm holes in face brick -

1 boor W (Small).JPG (33.9 KiB) Viewed 4628 times

it WORKED

Opens up a whole world of opportunities for small DIY tasks where there is no power .....




Next we headed of to Mr B ... and the pool pump

roled out the leads .... switched on .... the inverter showed "Fault".

okay ... so is the pump drawing too much power at startup ?

Off .... wait ..... ON .... "Fault"


Let's try once more .... it WORKS

1 Swembad pomp (Small).JPG (39.57 KiB) Viewed 4628 times

Thus the 1500W PSW inverter CAN start a 750W pool pump. BUT, I do believe this is just too close to the limit and would rather use a larger inverter for this purpose .... OR WOULD I ????


TIME FOR A REALITY CHECK !

This pump is SUCKING about 70A from the battery !!!!!!!!!!!!!!!!!!!!!

You would need a serious battery bank to keep the pump going. Alternatively you need about 800W worth of solar panels ...

The whole system goes "crooked" with insanely high currents and cables that could jump start a boeing!!

The industry solves this by working with battery banks connected to provide 48V, and reduced currents .... THIS is a whole new ball game !!!!!

[ChrisF]

We were concerned that maybe the setup will not outlast a load shedding period and tested it to see if our system will work.
We also wanted to see if the low battery protect system will only sound an alarm or switch it off.
....

Pieter we also tested the low voltage cut out function


I used the tv test to lower the battery SOC before doing the poolpump test.

It took about 15 minutes (sadly we did not time it properly) for the pool pump to DRAIN the battery.

It goes down to about 11,4V then the UPS switches off, and starts the alarm.

I moved the bakkie into the sun, with the solar charging the battery. Even with the higher battery voltage the inverter did NOT switch on again. I had to manually switch it OFF, then ON again before it would start up again. GOOD !! LAst thing you want is an inverter that keeps on rebooting automatically each time the battery voltage recovers.

[pietpetoors]

I also wondered about the inverter welder.
We should test that some time.
If your inverter is too small we can use the one at our office.

[Mud Dog]

One of my inverters is an identical unit ...... question ..... can one get spare fans for them? (My one is noisy - missing a blade or two).

[george]

I also wondered about the inverter welder.
We should test that some time.
If your inverter is too small we can use the one at our office.

Julle 2 gaan nie ons kantoor sin breek nie Julle kan eers speel as daar 'n replacement unit is

[ChrisF]

I also wondered about the inverter welder.
We should test that some time.
If your inverter is too small we can use the one at our office.

Julle 2 gaan nie ons kantoor sin breek nie Julle kan eers speel as daar 'n replacement unit is

blerrie spoil sport ...

[ChrisF]

TIME TO RECAP -

our classic 12V battery is a very handy package of electrical engergy. And with the use of a quality inverter it certainly CAN assist during a load shed !!


Both Pieter and I have opted for the cheap UPS to keep everything going when the power goes off, we can then at leasure move the UPS plug from the wall socket to the inverter.

Thus NO touching and fidling with the house wiring !!


Nice cheap and practical solution for small power consumption.



The problem starts when you need more power ... PERSONALLY I would hate to provide more than 300W via an inverter for extended periods from a single battery.

NOTE - as in Pieter's test you may still need a 2 500 W inverter, purely to power the printer for those few seconds !




so what about that pool pump ?

[pietpetoors]

Andy isn't that a normal PC fan?

The ones we are testing now is totally different from those I imported 2 years ago.

[ChrisF]

Driving items such as the pool pump from a 12V battery cant end good ! I just dont believe a battery was meant to deliver 70A for extended periods.

And switching to a 48V battery bank is a whole different field of expertise !!


Thus the search continued for a suitable PV driven pool pump.

The number of people, people in the pool industry, that told me "It is just too expensive" ......


First supplier I spoke to said R30k ! JIP, that is a bit rich, and that did not even include all components.


I spent an hour or two per day for more than a week emailing and phoning people. The worst was those "phone operators" that had NO idea of what they were selling !! One kid in a pool shop in Brackenfell, near 4x4Direct, even made the statement that if I used pump X instead of pump Y my electrical savings would be more than R100 PER DAY.


Okay, on to the possible options -
1) Lorentz solar pump(s) (German) - R25 000 to R 61 000 (YES, one company sent me a written quote for R61 000!)
Various different sizes, so you need to buy the correct size - for costing reasons some suppliers offered me an undersized unit ...
Components:
- PV panels
- Control Panel (physically a MASSIVE unit)
- Motor & Pump unit

Note - NO battery. Straight from the panels to the controller to the pump

2) Bundu Power solar pump(s) –
Two different sizes, R 16 000 for the smaller unit
Components:
- PV panels
- Control Panel (substantially smaller unit)
- Motor & Pump unit
NO STOCK. I emailed again and asked when they expect to have stock - got another "Thank you for the enquiry, attached find a quote.."


4) Grundfos PoolFlex solar pump (Denmark) – R 18 000 for the complete system with 4 PV panels (typical small pool under 20m3)
Grundfos is very well known in industry for top quality products, with a very wide range of pumping products for industry. One of the select companies whose products are approved in Fire fighting installations.

With their vast depth of knowledge of pumping solutions they approached the solar pool pump solution differently.

ONE single pump option, with a 1,1kW 220V electric pump. This pump gets fitted with a control box that becomes part of the pump. This box can take input from PV panels ranging from 300W to 900W. Thus you buy one pump and alter the number of solar panels to suit your pumping requirements.

Worth noting that the solar side is designed to work with an input voltage between 110V to 415V, thus 36,8V PV panels are used and arranged to ensure the correct voltage. This system actually becomes more affordable the bigger the pool, as it only costs more by the cost of the extra panels :)

[ChrisF]

Pay back period

THIS is certainly thee decider.

It is also not an easy calculation, at least not if you want to account for all the variables.

The basis of a pool pump size and running time starts with the industry norm that the total volume of water should be recirculated at least twice per day. The first knee jerk reaction is to use a larger pump to reduce the run-time, thereby saving a bit of electricity.

However, this kick starts a cycle of troubles. The salt chlorinator is NOT designed to work for short periods. Instead it works best with about 8 hours of run time per day. Reduce the run time and you need to spike the pool with chemicals ….

Thus the break even calculations will be done based upon a correct pump size and 8 hours run time.


Example 1 – Small 12m3 pool, with heating tubes on the roof.
220V – 450W pump runs for 8 hours per day equates to 3,5kW.h used per day. Working with an electrical cost of R1,75 per kW.h the electrical cost is R 189 per month, or R 2 300 per year.


The Grundfos system for this pool costs R 17 000. This would typically mean a 7,4 year payback period.

HOEWEVER, if you did this when installing a pool the “extra costs” are roughly R 15 000, or a payback period of 6,5 years. Now allow for the increase in costs of electricity and the payback period probably about 4 years. :)




Example 2 – Medium sized 50m3 pool, with heating tubes on the roof.
220V – 1100W pump runs for 8 hours per day equates to 8,8kW.h used per day. Working with an electrical cost of R1,75 per kW.h the electrical cost is R 462 per month, or R 5 621 per year !

Suddenly the payback period is just over 3 years. Or just more than 2 years when you allow for escalation in electrical tariffs !!


These systems are an absolute no-brainer for those with larger pools !!!!

[pietpetoors]

So if one look at DC Pool pumps, what voltage? 72 Volt? 48 Volt?

[ChrisF]

So if one look at DC Pool pumps, what voltage? 72 Volt? 48 Volt?

Pieter these are sold as "units" with the suppliers keeping their designs under wraps ...


their "control boxes" takes the power from the solar panels and then magic happens



With the Grundfos pump we know the motor is a 220V AC unit, and the controller works around this principle.

With the other two I am not sure what magic happens inside .... (as it comes as a unit I have not seriously looked into the inner workings)

[pietpetoors]

So do they run the pumps directly from the panels?
Almost like the EV element for the geyser? When there is sun, the pump runs, no sun, no pump?