# Solar panels

#### Haris

Jun 23, 2011
19
Dear,

I need a help Iam building up a Solar system for home:

The daily usage is Appx: 2500Kw.

if anyone has an Idea about that kindly share and guide me.

Regards,

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
Firstly determine how much power you consume per day. 2500kW is NOT the figure. It is measured in kWh, and a number like 25, or 50 might be a reasonable one if you use lots of power.

Then determine if you want to be off-grid or have a grid connected system. Do some research here.

Then determine how much power you require from the solar panels (remembering that they may not be producing useful power for more than 8 hours per day).

#### poor mystic

Apr 8, 2011
1,074
To get the figures Steve recommends, you'll need to know what appliances you need switched on, and for how long, every day.

Say there is a 50 watt (50W) lightbulb that needs to be on for 8 hours. Then 50 x 8 = 400 watt-hours, or 0.4 kWh. Then you might need a stove for an hour that uses 1000W or 1 kW. This is 1kWh. You need to add up all the power requirements in that way, and so get your daily usage, which is usually reported in kilo-watt hours (kWh).

Having done the arithmetic to find out your usage, you can begin to assess what is required to generate that power. Solar power accessories are getting very good but there are plenty of traps for young players. For instance a solar panel might be rated at 1kW. This does not mean 1kW for 24 hours of the day - it is a maximum rating that describes how well the panel can perform in full sunlight when the panel is squarely facing the Sun. Obviously that can't be for more than a few of the 24 hours.

The next thing is to consider how the power will be stored for use when the panel is not generating. Many people choose lead-acid storage batteries. This is a whole new can of worms and all that can be said in a post on a BB is that serious attention needs to be paid to the battery part of the installation.

Finally the question arises of how you are going to use the power. If it is to be 12V working you'll need 12V appliances - not convenient except for small lamps and radios. If it is to be at mains voltage you'll need an inverter. Lots more worms.

The design and installation of solar power equipment is skilled work which should be done by competent tradespeople. It costs a lot of money to install solar power well. It doesn't cost much less to make a bad job.

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
Or even easier, check your electricity bill. It should summarise your usage.

#### Haris

Jun 23, 2011
19
Rep to all!!! about solar Power Discussion

Thanks to u all for sharing u r information.

Now I have calculated that:

What I have to run through Solar Power at my home is:

1) 2 X 14watt Savers= 28watts
2) 2 X 120watts ceiling fans= 240watts

So, total of, 268 watts.

Now amount of Time Appx. 8 Hours so 268 X 8 = 2144 watts of Power of Daily Usage.

Now Check my calculation and I welcome if any mistake!!

I Think Now Two Solar Panels for suppose of 100 watts will be sufficient????

And the Simple Inverter circuit will be sufficient but in the Inverter circuit I am not sure which ratings of transformer should I use??? Since I live in Pakistan here the Voltage Standard is 220V, 50Hz.

So plz suggest me which Ratings of Transformer should I use????????

Secondly single 12V battery is suitable or not?????

Kindly reply as early as possible??????????

And if anybody can send me the Inverter circuit diagram suitable to all my discussion???????????

Waiting!!!!!!!

Regards,

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
Now amount of Time Appx. 8 Hours so 268 X 8 = 2144 watts of Power of Daily Usage.

That's actually 2144Wh, or 2.144kWh

I Think Now Two Solar Panels for suppose of 100 watts will be sufficient????

That will give you (conservatively) 1.6kWh per day. If we assume you're charging lead acid batteries to provide power at night, then you'll get about 0.8kWh, or approximately 1/3 of your requirement.

And the Simple Inverter circuit will be sufficient but in the Inverter circuit I am not sure which ratings of transformer should I use??? Since I live in Pakistan here the Voltage Standard is 220V, 50Hz.

If you have an inverter, you will not require a transformer. Your inverter needs to be capable of supplying your peak load. something between 300W to 500W should be fine.

Secondly single 12V battery is suitable or not?????

One battery is almost certainly OK. However what capacity battery will you need?

If you want to ensure the battery is not more than 50% discharged, and hold 2 days of power (to allow for a cloudy day). Then you need something capable of storing something a little more than 8kWh. At a nominal 12volts, that's close to 700 Ah.

You also need a solar regulator, preferably a maximum power point tracking regulator.

And if anybody can send me the Inverter circuit diagram suitable to all my discussion???????????

For efficiency and lowest cost, I'd buy one.

Waiting!!!!!!!

Don't appear impatient. It doesn't impress people and doesn't speed up the response.

#### poor mystic

Apr 8, 2011
1,074
the figures might be correct but the units are not - your usage is measured in watt-hours. Just as you have found, Energy = Power x Time.
You now know that you must supply 2144 watt hours of energy every day, which is the same as 2.144 kWh (kilowatt hours).
Now in order to be sure you can supply that energy you need to consider your worst likely day and design for it. Perhaps you can place your panels in a position where they'll receive 4 hours of sunlight on the worst day you plan for. If so, you will need 500 watts of panels.
There is more expensive news unfortunately - you need to supply an overhead for losses. All systems are inefficient, and since you are going to store energy in your batteries the losses of the batteries must be supplied. At a guess you'd want at least an extra 20% of generating capacity.
So that's 2572.8 watt hours every day... ridiculous precision but I gave you the exact arithmetic so that you can be sure you appreciate the method. We never round such figures down... lets call that 2600Wh or 2.6kWh usage per day including losses at 20%.
I am not sure that I have made enough allowance for losses here, by the way. I very much fear that 40% may be more realistic by the time power conversion losses in your inverter are considered.

Isn't this awfully expensive? You bet it is. Are there ways to economise? Thankfully, yes. But not enough to make the job as cheap as you'd like.
Economies are achieved by using the power at the voltage it is supplied by the batteries, by using thick cable (bigger installation cost but saves generating capacity), and by using lower powered appliances.
These 2 x 14W "savers"' for instance. Are they lighting? Try replacing them with single led's which run straight off the 12V and are installed right where you want the light. Don't try and light the whole room. That will save heaps of pwer, and you'll be able to plan a smaller installation.

There's doubtless lots to say yet but this'll give you plenty to chew on for a day or 2, I guess.

#### Haris

Jun 23, 2011
19
Rep to all!!! about solar Power Discussion

Hi Steve as u have said that:

That will give you (conservatively) 1.6kWh per day. If we assume you're charging lead acid batteries to provide power at night, then you'll get about 0.8kWh, or approximately 1/3 of your requirement.

So what do u recommend that what ratings of Solar panels should I use???

The another thing u have said that:

If you have an inverter, you will not require a transformer. Your inverter needs to be capable of supplying your peak load. something between 300W to 500W should be fine.

Dear Transformer is the necessary thing as the voltage needs to be Step-up, I am not clear without using transformer How can we do that???

Regards,

#### poor mystic

Apr 8, 2011
1,074
1) Steve said that 2 panels will give 1/3 of your needs. Therefore he says you need 6 panels. That is 600W of panels.

2) An inverter is special equipment which makes mains voltage out of 12V. So no step-up transformer is needed.

I hope you understand. The less power, the less solar panels. Solar panels are expensive. So is a huge battery.

So use led lighting, because it is cheap.

#### Haris

Jun 23, 2011
19
Dear thanks for all those who have replied!!!

1) If we connect two solar panels their rated output voltages are multipled or added???

Ok thanks for the information but as far as I have senn on net the Inverter ckt diagrams the transformer is present everywhere!!!

But as u have said that no Transformer is required so I just have to build the simple circuit...!!!?????

#### poor mystic

Apr 8, 2011
1,074
If 2 solar panels are correctly connected their output voltages will not be added or multiplied... the voltage stays the same as for a single panel.

Inverters are complex electronic equipment. A transformer is included with other electronic parts inside the inverter.

A solar power installation is pretty serious engineering. Designing a suitable installation is not a small job, and actually installing the equipent cannot be easy, simple or cheap

.

#### davenn

Moderator
Sep 5, 2009
14,011
???

Ok thanks for the information but as far as I have senn on net the Inverter ckt diagrams the transformer is present everywhere!!!

yes they are, but as steve said you are after the most efficient system possible because of your power needs. You are much better off purchasing a decent inverter

But as u have said that no Transformer is required so I just have to build the simple circuit...!!!?????

An inverter isnt a simple circuit. That is why we are recommending that you purchase one

Dave

#### Haris

Jun 23, 2011
19
OK.

If I have to get the 2500watts of energy so what I require is as one of the group member said to use 6 panels of 100watts, is this will be the correct Idea????????

But the thing in which I am confusing and not finding the suitable answer is that:

For 2500watts I have to have the Solar panels array which generates 2500watts!!?? or the Inverter circuit gives the actual 2500watts?? Kindly reply!!

Regards,

#### Haris

Jun 23, 2011
19
The Simple circuits of Inverter which are available on the Internet are so easy to build. But as they are suggesting to purchase, Why ???

#### DaleFranklin

Jul 5, 2011
3
You can probably buy a inverter for close to what I might take you to build it from scratch - that is unless your labor is free and you really enjoy building it yourself.

Dale
http://www.activeenterprisesltd.com

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
For 2500watts I have to have the Solar panels array which generates 2500watts!!?? or the Inverter circuit gives the actual 2500watts?? Kindly reply!!

Go back and read my reply again. Note the difference between watts and watt-hours. Google these if you need to.

You need to understand the concepts first.

Think about the suggestion to use low voltage LED lighting. It will be vastly more efficient (if only because it avoids losses in your inverter).

And lastly, don't demand answers. It will make me LESS likely to respond.

#### Haris

Jun 23, 2011
19
Dear,

I am demanding to generate the power using Solar Panels. ???

#### Haris

Jun 23, 2011
19
I have read the difference. Now I am going to the conclusion that:

I should buy the Inverter and do not construct it because of its accuracy, First;
Secondly the 2 to 3 Solar panels of appx. 100watts.

#### poor mystic

Apr 8, 2011
1,074
Hi Haris
You've apparently scaled your power demand down about 50%, which is good.
I wonder, have you assessed your costs lately? I think you'll make further economies when you find out how much the battery installation will cost.
If you really have decided you can get by on half the original power, you'll need 350 Ampere-hours worth of "deep cycle" lead acid batteries. Ordinary motor car batteries won't give the economy you're after - they'll need early replacement.

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