Advice request - solar energy invertor

[lightblue]

hi
hope someone will know..

i wanted to buy a portable (fold up) solar panel last weekend..the guy selling them said i would also need a solar invertor (12v) - which weighed a tone, so i couldn't carry it there and then..i tried looking it up on the net and i don't find whether i could do without it or not..dies anyone know?.

than i looked at roof panels (4 of them at 60watt altogether) ...is that good/sufficient power once accumulated?

thanks l

[Operator]

You need an inverter to generate e.g. 110 Volt AC (or maybe even 220 Volt AC) from 12 Volt DC (I think that's your case).

Modern day solid state devices can easily handle 1500 Watts, are not bigger than half a shoe-box and can be lifted with one hand. I have two of them.
You may need to consider charging car batteries with the solar panel and generate your electricity from the batteries (this way you can accumulate
energy during the day and have electricity at night).

How much power you need is dependent on your consumption ... Where I live I get a monthly bill with exactly the consumption in KwH (KiloWatt Hours).
If you don't have something like that you need to inspect the consumption meter yourself each month on a specific date.

Kilo stands for thousand ... so multiply the number with thousand and divide by 30 (days) and again divide by 24 (hours) ... this will give a number
(it represents power) that you need continuously (on average) to charge the batteries to keep up with consumption.

Example in my case: 130 KwH ==> 130.000/30 = 4333,3333 ==> 4333,3333/24 = 180,5 or in other words I need to charge continuously (24/7) with
approx. 180 Watts to keep up with my daily consumption.

The example is theoretical however ... I think it's close to true when the power from the panels is used directly to feed the inverter.
When you charge a battery for later consumption the efficiency will be much less than 50%. And it will be a combination of those
circumstances.

Now I can further tell you that 130KwH is probably a low consumption profile and that alone leads to 180 Watts or more of
continuous feeding power so the 60 Watt panels will contribute to- but not cover your consumption.

Small windmills on average generate more power (300 Watt is achievable) with the possibility to be operated whole day long.

I hope this helps you gaining more insight on your situation

[Ross]

Posted by lightblue (here)
hi
hope someone will know..

i wanted to buy a portable (fold up) solar panel last weekend..the guy selling them said i would also need a solar invertor (12v) - which weighed a tone, so i couldn't carry it there and then..i tried looking it up on the net and i don't find whether i could do without it or not..dies anyone know?.

than i looked at roof panels (4 of them at 60watt altogether) ...is that good/sufficient power once accumulated?

thanks l

Can you please say what you wish to use this system for? your expectations of amount of power you want and what you want to run?
Sounds to me like the guy is suggesting you invert to run a 12volt system? example, appliances that run on 12 volts? not 220 volt?

If you are inverting 12 volts to 220 volts you will require more than 4 x 60 watt panels = 240watts. Solar panels only produce their rated wattage if they stay 25 celcius or below, if they are on a roof in the hot sun you can get up and beyond 60 celcius heat in which case the solar panel wattage will drop to around 45 watts per panel reducing your overall collected wattage.

Most solar systems designed to run a house are 24 volt systems inverted to 220/240 volts so you can run normal 220/240 volt appliances. caravan/mobile homes are often 12 volt systems so all lights and appliances are 12 volt.

I run a 24 volt system at my house. 10 x 160 watt panels, 240 volt inverter, run all normal household appliances. the key is about storage, your batteries, i have 4x6 volt batteries, rural power supply batteries. each battery stores 670 amp hours but I should have 1040 amp hr batteries to have more headroom but i manage on the 670's.

The weak link in all solar is your batteries. they must have enough amp hours. batteries are lead acid and as they draw power at night they drop voltage. the lower you drop the voltage the harder the batteries have to work thus reducing their life. so its all about battery compacity and keeping voltage within its range, i.e, 12 volt batts, do not draw below 12 volts, 24 volt, same applies, dont go below 24 volts. I work on my appliances and what amperage they draw, from this i know exactly what amps are being pulled from the batts thus knowing where my headroom stands (above 24 volts)

also you will need a regulator, this determins when your batteries are full and stops the flow of current to not 'over charge' batts, this is vital. my regulator also has a digi readout telling what amps/volts are being produced and used. again I say the batts are the key to a good system. this may sound confusing but you can PM me or post any questions you have.

Ross

[Ammit]

The charger style you talk of produces normally, 4 watts at 12v.
Not a lot of punch for ya buck...

[Anchor]

With invertors it is important also to consider the output waveform. Some are pure sinewave, and these are the expensive, heavy kind that play nicely with all forms of electronics and typically have higher efficiency ratings (85%-90%). Then there are the cheaper modified sine wave invertors, much lighter in weight, that have much lower efficiency ratings (anywhere from 60%-80%) and do not play nicely with some form of electronics, for example they are not good with audio systems or fluorescent lighting - but are good for loads like kettles, heaters etc.

Before buying anything you need to consider what you are trying to achieve.

If you are camping and want to run a fridge, get a fridge that runs on 12v or 24v dc and you wont need an inverter, and if it is sunny - 2 x 60W panels should be enough.

If you want to run a house its a lot more involved.

For solar - the design of the system is all about what you will use it for.

Solar power is a lot more expensive and complex than most people give credit for. I am currenly going through the process of taking my farm off grid and have, shall we say, learned from some errors

[Ammit]

I am still in the process of making a turbine generator that requires no wind or rain, only a small unit to produce 600watts per hr. Solar is so exspensive for the gains and I believe, not worth it...

[Ross]

Posted by John (here)
With invertors it is important also to consider the output waveform. Some are pure sinewave, and these are the expensive, heavy kind that play nicely with all forms of electronics and typically have higher efficiency ratings (85%-90%). Then there are the cheaper modified sine wave invertors, much lighter in weight, that have much lower efficiency ratings (anywhere from 60%-80%) and do not play nicely with some form of electronics, for example they are not good with audio systems or fluorescent lighting - but are good for loads like kettles, heaters etc.

Before buying anything you need to consider what you are trying to achieve.

Solar power is a lot more expensive and complex than most people give credit for. I am currenly going through the process of taking my farm off grid and have, shall we say, learned from some errors

Pure sinewave are the only option, mine is worth 4000k and is excellent, John is correct in all he says above. It is a costly exercise fitting out a good system and a good solar provider is most important, there are many cowboys who will sell you anything only to later discover its crap!

Ross

[Operator]

Posted by Ross (here)
Solar panels only produce their rated wattage if they stay 25 celcius or below, if they are on a roof in the hot sun you can get up and beyond 60 celcius heat in which case the solar panel wattage will drop to around 45 watts per panel reducing your overall collected wattage.

Hi Ross,

Maybe you can turn a problem into an opportunity !
If you would cool the panels with water ... the water will be heated for free as well ...

Cheers, Op.

[Ross]

Posted by Operator (here)
Hi Ross,

Maybe you can turn a problem into an opportunity !
If you would cool the panels with water ... the water will be heated for free as well ...

Cheers, Op.

Yes I understand but solar hotwater panels and cylinder provide excellent hot water.

[Anchor]

If your objective is to save money, then you should always go for a solar hot water system first. This has very little to do with electricity.

I have seen no hybrid hot water and photo voltaic panels on the market. They are each good at what they are designed to do within the limits of publically available technology.

[lightblue]

Pure sinewave are the only option, mine is worth 4000k and is excellent, John is correct in all he says above. It is a costly exercise fitting out a good system and a good solar provider is most important, there are many cowboys who will sell you anything only to later discover its crap!

Ross

If your objective is to save money, then you should always go for a solar hot water system first. This has very little to do with electricity.

I have seen no hybrid hot water and photo voltaic panels on the market. They are each good at what they are designed to do within the limits of publically available technology.

thank you john and ross and everyone..

i would ask you to please recommend some useful informative links i can study before i know how to articulate further questions...i've no idea what sinewave is, for example...don't know what hot water system is as opposed to others either...
are there any differences between the makes?

i live in EU and this is supposed to comply with the standards here - in case there are differences..

i stumbled upon this sellar by chance and have an opportunity to buy - his shop closed down last year and is now selling out at knock down prices what remained in his storage depot - i undestand it's very important to know what i am getting before i do... thanks again l

[Operator]

Posted by lightblue (here)
i would ask you to please recommend some useful informative links i can study before i know how to articulate further questions...i've no idea what sinewave is, for example...don't know what hot water system is as opposed to others either...
are there any differences between the makes?

There is no need to study on what sine waves are for this purpose ... simply keep in mind that alternating current (AC) is the continuous changing of polarity between the electrodes (the 2 poles from your power outlet).
This picture shows a little what you basically need to know:



The perfect sine wave is shown in the line 'first approximation'. The more the sine wave is distorted by an imperfect generator the more harmonics (higher frequencies) will be components of the generated power as well.
Some appliances can't handle the higher frequencies very well. You would need an oscilloscope however to check the output and it should be tested under several circumstances like: "does it still generate perfect sine waves under heavy load ?"



So although it is important to pay attention to it ... it may be more difficult to check in practice.

Sorry for the hot water distraction ... I was just teasing by suggesting how to improve the efficiency of the solar panels and get hot water for free in one stroke.

John and Ross mentioned that to get hot water there are better systems (I know).
This is a complete other type of system though ... your current interest is generate electrical power not generate free hot water (maybe later).

I hope this clarified the info a little ?

P.S.: 60 Watts 'all together' by 4 panels isn't a lot ... maybe you should surf on the internet to get more familiar with similar products

[john.d]

With Inverters , you really get what you pay for . Ive tried the cheap modified inverters but they just give you dirty power . Its worth paying a bit more for a good sine wave inverter . Keep an eye on ebay for deals , i just got myself a second hand outback 12v 2.6kw inverter for £800 which are £2250 new . If i had a choice i would go for a 48v system though , this keeps the current down and cables dont have to be as big .
Here's a good link for solar water heating :
http://www.builditsolar.com/Projects...er_heating.htm

John

[Anchor]

Well I am in Australia now so I would point you at www.energymatters.com.au and www.rpc.com.au

I started buying my gear from England when I was there - I went for people who were more used to kitting out boats - like mastervolt and victron - but my application is off-grid. I am now in Australia so things are a little different here and the rules and regulations are just as tight - if not tighter!

If you want I can have a chat with you over skype and get you straight on the basics.

You do not have to study anything in order to answer my question: what are you trying to acheive?

• Do you want to go camping?
• Power your house?
• Backup power for your house?
• Power just some critical items in your house - or the whole thing?
• Sell energy to the grid?

Basically what do you want to do?

If you want to "study" there are some excellent books you can get. One is called "Solar power that really works" http://www.energymatters.com.au/sola...rks-p-850.html