How to Solar Power Your Home / House #3 - How to size your solar power system

[MJLorton]

Link to the video tutorial here: https://www.youtube.com/watch?v=_ZN9gOlkOtI

In this video I talk about sizing your solar power system and in particular taking losses into account:

Grid Tie or Off Grid...some more handy info on losses and batteries:
http://www.aprs.org/off-grid-maybe.html

Getting an idea of solar radiation / insolation in your area:
http://www.matthewb.id.au/media/world_insolation_map.gif
http://www.nrel.gov/gis/solar.html

Solar Power calculator:
http://www.matthewb.id.au/media/Solar_Power_Calculator.html
http://www.dako.co.za/solar_system_calculator.html

Need Solar power measurement kit? ;-)
http://www.tester.co.uk/catalogsearch/result/?q=solar+pv+kit&cmid=QmhzQjcxYjVlc1E9&afid=bFcwbzliNzVDc289&ats=Nkk5bU53Uk5sSEE9

[Chaser]

Love all your vids especially the solar stuff.
Something to note. If you trying to work out a 40% loss, you technically can't just add it. ie 8200+40%= 11480 but 11480-40%=6888
I know it's just averages so it might be close enough...
Wish I could tell you the exact way to calculate it but I myself don't know and can't seem to be able to look it up, maybe someone else knows?
Thanks again for the great work you do!

P.s maybe i am missing something

[MJLorton]

Love all your vids especially the solar stuff.
Something to note. If you trying to work out a 40% loss, you technically can't just add it. ie 8200+40%= 11480 but 11480-40%=6888
I know it's just averages so it might be close enough...
Wish I could tell you the exact way to calculate it but I myself don't know and can't seem to be able to look it up, maybe someone else knows?
Thanks again for the great work you do!

P.s maybe i am missing something

Hello Chaser,

Thanks very much for the feedback...and a big thanks for picking up that maths fluff!

It should be (where x is the required watt hours) x-0.4x=8200 therefore x=8200/0.6 = 13666 watt hours!

Will annotate now.

Cheers,
Martin.

[Xan]

Hi Martin,

I have been enjoying your videos and especially the recent ones on the Solar Power.

Just curious on one aspect ov your own setup.

You have a hybrid system ov both grid tie & off grid inverters. Do you run both from the same array? (From I got from watching is that you have a grid tie inverter and then for the batteries you have an inverter charger which I presume is then A.C. coupled into the GTI?)

[Chris]

Hi Martin

Great work with the videos much impressed.

Regarding the losses involved math I understand the need to subtract your 40% losses from the 100% value you actually need demand wise ie x-0.4x=8200

I just can not work out how you get to x=8200/.6

I am sure its straight forward however it just will not click.

Hope you can help.

[MJLorton]

Hello Chris,

Thanks for your post.

What I really need to do is re-work and post a spreadsheet I have to assist with sizing and calculating losses.

The complication is that the losses can only be properly calculated once you have the sizing correct...a little chicken and egg...

If I don't have it here in a week or so please post again and nag me...

Cheers,
Martin.

[Chris]

Hi Martin

Yes it is a chicken egg story!

I have been putting a spreadsheet together and this is why, regarding the losses, needed an equation to formulate an answer and got stuck on the maths.

I have spent a few days brushing up on my algebra and worked out the math of the equation. It was actually very simple I had just forgotten some of the rules on combining like terms!

Thanks for getting back to me and I look forward to checking out your spreadsheet.

[MJLorton]

Hi Folks...

Here at last is the solar power system sizing spreadsheet...it is still a work in progress as there is one more formula I need to get working (variable battery SOC level).
If there are any obvious errors or bits that should be added ...let me know.

Cheers,
Martin.

[zeden.nz]

An awesome tool!!  Thanks so much Martin.

[MJLorton]

Thanks, my pleasure...just remember it's still a work in progress...

[mariense]

Great video on properly sizing your solar system.
Very informative and surprising.
Did not realize the amount of loss due to heat.
Maybe having an automatic water system to cool the panels could fix that problem , just an idea.

By the way, regarding:

>> I just can not work out how you get to x=8200/.6

You know 8200 is the kwh with a 40% loss, so 8200 is 60% of your 100%, so:

8200 kwh ------ 60%
X kwh ---------- 100%

8200 x 100 = X x 60
X = (8200 x 100) / 60

8200 times 100, divided by 60, equals X

[MJLorton]

Hello Mariense,

Thanks for the feedback.

There are folks that now produce a hybrid "solar panel" that produces both electricity and heats water. They send cool / cold water through pipes behind a PV to make it more efficient and end up with warm / hot water as a by-product to go into a hot water cylinder.

There are a few versions now:

http://www.earthtechling.com/2012/04/hybrid-solar-panels-yield-electricity-hot-water/
http://inhabitat.com/new-solar-thermal-flat-panels-are-eight-times-more-efficient-than-existing-technology/
http://www.alternative-energy-action-now.com/hybrid-solar-panels.html

Thanks for the better explanation of the equation too.

Cheers,
Martin.

[KTBrown]

To help those having trouble calculating required watt hours:

x = required watt hours (to achieve 8200wh after 40% losses)

x-x(0.4)=8200
x(1-0.4)=8200
x(0.6)=8200
x=8200/0.6=13.67 kwh

[jimbommx1]

Hi MJLortan,
I have this assignment on space applications of solar arrays and battery banks. I have been assigned to calculate the size of the battery bank which is needed based on 508,000Wh per day will you be able to direct me in the correct path, do you have any ideas which could help me thanks and love the youtube videos very clear information
Thanks

[Offgrid]

Thanks for all the effort and really useful information on solar power.
I am currently busy with an off grid project, and would like to include a small 220v emergency petrol generator to the system.
My question is , would I need to use a grid tie inverter to hook  up the generator  or is there a cheaper way of doing this?