Solar PV - is it worth it?

cnocbui

Sir Liamalot wrote: »

Nope, the battery's internal resistance means the faster you discharge the less you get.
A 5kWh battery has 5kWh inside indeed.
Now is the manufacturer using over-zealous charge voltages like every portable device in production to get that figure reducing the overall battery life expectancy to one-sixth what it could be?

My phone has a li-ion cell rated 5.4Ah
It's end of charge voltage is 4.35V. This is detrimental to it's health.
At 80% charge it is 4.2V the standard end of charge voltage (and still 150mV too high).

So my phone has a 4.3Ah battery but the manufacturer plays with numbers and I have an over-clocked battery that has an operating envelope of 5.4Ah and a cycle life of 450 instead of 3000.

Back to the wall art quandry.
Beware Man Maths to follow.

Say you have a solar array with a 9 year payback. Say you only use a third on demand.
So 6 years of that payback depends on the battery system efficiency.
Let's accept the battery only pays for itself before it expires.

So of the 6 year storage payback
80% efficient Solar to Mains Bus to AC Couple
First conversion is free you were never going to get a 100% efficient inverter.

So you want to charge your battery with an 80% efficient charger. 7.5years payback.
But the battery is only 90% efficient. 8.3 year payback.
You want to use the energy in the battery? 80% efficient inverter. 10.4 year payback.

Plus original 3 year supply on demand time 13.4 year payback. Congratulations your battery added 50% expense to the lifetime of the system. But wait wasn't the system more expensive to install with the art complications.

So glad my taxes helped you. :rolleyes:

Datasheets are full of contrived optimised lab circumstances you'll never see in the real world. Look at your system power in versus power out then you'll understand.

My daughter just got a 1 in higher maths in the leaving cert. My wife has a Phd in electrical engineering and teaches the subject and I very much doubt you could match her in ability at maths.

niallers1

The great thing about it though is it's not always a pound shillings and pence decision. You displace alot of carbon over the lifetime and you get a satisfaction from producing your own electricity.

Water John

Agree, once the ROI isn't longer than the lifetime of the installation, it becomes a personal decision.

cnocbui

cnocbui wrote: »

My daughter just got a 1 in higher maths in the leaving cert. My wife has a Phd in electrical engineering and teaches the subject and I very much doubt you could match her in ability at maths.

Maybe they can help do your homework instead so.
My maths are based on empirical data.

cnocbui

Sir Liamalot wrote: »

Maybe they can help do your homework instead so.
My maths are based on empirical data.

Perhaps they could give you some pointers on raising your IQ to a level sufficient to identify the salient points in an issue.

I deliberately simplified it to make it accessible and understandable to Joe public.
That and why waste my time trying to convince people who have already decided what they want to believe.

Your daughter could easy tell the difference between power in and power out if you showed her a meter of the losses in the installation.

cnocbui

Sir Liamalot wrote: »

I deliberately simplified it to make it accessible and understandable to Joe public.
That and why waste my time trying to convince people who have already decided what they want to believe.

Your daughter could easy tell the difference between power in and power out if you showed her a meter of the losses in the installation.

I was commenting on your use of the sexist phrase 'man maths', not the accuracy of any maths performed.

cnocbui

cnocbui wrote: »

I was commenting on your use of the sexist phrase 'man maths', not the accuracy of any maths performed.

I am a man I made the maths.
They are rough.

Shefwedfan

cnocbui wrote: »

I was commenting on your use of the sexist phrase 'man maths', not the accuracy of any maths performed.

How is it sexist?????

denismc

cnocbui wrote: »

I was commenting on your use of the sexist phrase 'man maths', not the accuracy of any maths performed.

Seriously?

gunnerfitzy

Thanks to those who weighed in about my forthcoming decision.

My gut feeling at the moment is to go with the 2.5kwh battery right now and then make a decision perhaps in 12 months or so whether add another 2.5kwh pack. I will have a years worth of own usage and generation data to go on at that stage. Installation cost for another pack at a later date shouldn’t be significant but I will get that info when I discuss this with the installers.

JHet

cnocbui wrote: »

Perhaps they could give you some pointers on raising your IQ to a level sufficient to identify the salient points in an issue.

That's uncalled for.

gunnerfitzy

gunnerfitzy wrote: »

I will have a years worth of own usage and generation data to go on at that stage.

...please share with the class too!

rolion

Got my gas bill for the summer...well done Solar tubes and panels / diverter...

unkel

Your previous meter reading was an estimate, which was too high, so you're getting refunded on this bill

My last gas bill was also very low, even though we use lots and lots of hot water. Almost all of it during the summer is heated with solar tubes, occasionally topped up by gas.

Latro

I dunno, I'm not convinced at all.

From top of my head it looks like you invest 3-4k euro into installation to save 250-300 euro a year.

eire1987

Hi,

Myself and my wife are planning a new build. It is suppose to be a timber frame house - our aim is to be near passive as possible. We are looking into using solar panels, are solar pv the best for a new build?? has anyone any recommendations if they are or if they are not whats the best method... any advice will be helpful

Cheers

Carrickbeg

rolion wrote: »

Got my gas bill for the summer...well done Solar tubes and panels / diverter...

Has the standing charge increased?

Shefwedfan

eire1987 wrote: »

Hi,

Myself and my wife are planning a new build. It is suppose to be a timber frame house - our aim is to be near passive as possible. We are looking into using solar panels, are solar pv the best for a new build?? has anyone any recommendations if they are or if they are not whats the best method... any advice will be helpful

Cheers

If a new build it will be cheaper to install so I would do both....thermal and PV.....

Latro

eire1987 wrote: »

Hi,

Myself and my wife are planning a new build. It is suppose to be a timber frame house - our aim is to be near passive as possible. We are looking into using solar panels, are solar pv the best for a new build?? has anyone any recommendations if they are or if they are not whats the best method... any advice will be helpful

Cheers

What will be your main source of heat?

unkel

Latro wrote: »

I dunno, I'm not convinced at all.

From top of my head it looks like you invest 3-4k euro into installation to save 250-300 euro a year.

Yep your figures are about ballpark. 12-14 years payback. Before the subsidy and the very recent price drops of panels it was more like 20 years payback

DIY (without any subsidies) you can do it for well under 10 years payback

(this is not taking account of opportunity costs of money, interest but also not of possible electricity / fuel price increases. Also it is quite likely overproduction can be monetised at some point in future)

Obviously after payback time, you have a yearly saving that will last for as long as you live in the house. It's a long time decision and also it is not 100% about money

py

Anyone compared figures on DIY vs contractor install and willing to share?

eire1987

Latro wrote: »

What will be your main source of heat?

Our site is in a very sunny spot. So obviously solar we be our main source. Well we think... we are also looking at the hone system. However not sure about thst. Although we were offered to stay overnight by the company to check their system... So they may be genuine

Shefwedfan

eire1987 wrote: »

Our site is in a very sunny spot. So obviously solar we be our main source. Well we think... we are also looking at the hone system. However not sure about thst. Although we were offered to stay overnight by the company to check their system... So they may be genuine

Really if new build if putting in heating you should be using geothermal heating.



Also if you include in the plans and get as part of the build then it should work out a lot cheaper than what you are saying....sure the electrician will wire it in with the rest of the house


The plumber can run the pipes when doing house.....a hell of a lot cheaper than a retro fit

Latro

eire1987 wrote: »

Our site is in a very sunny spot. So obviously solar we be our main source. Well we think... we are also looking at the hone system. However not sure about thst. Although we were offered to stay overnight by the company to check their system... So they may be genuine

I'm very skeptical about using any form of light to heat any house, even the best insulated one. In the winter the more heat you need the less light you get.

It is like having solar torch. It would work great in the sun when you don't need the light. Same with solar heating, maybe it would work in the summer but you dont't need the heat then.

Oh well, I don't have any experience with the system you mentioned so I can't give any valuable advice about it but it seems to be a bit tweaked evacuated solar tubes. As I said earlier, I'm skeptical.
If you decide to go with them please report back in the future.

rolion

py wrote: »

Anyone compared figures on DIY vs contractor install and willing to share?

DIY is fun ,challenging and tricky.Cheaper,yes.
In order to get the grant,you will need to be signed off by an approved SEAI installer.

I'll say differences in price can be around 23-50% overall.
Ive been quoted €1,700 ex VAT to install panels on the roof.
Done with neighbour,cash and few "thanks" with a black foamy fresh liquid.

Quality of the finished installation,i can say is at the same level if not better, as i chose the products that i felt are premium and not the ones that supplier made more margins or not stocking them.

rolion

eire1987 wrote: »

Our site is in a very sunny spot. So obviously solar we be our main source. Well we think... we are also looking at the hone system. However not sure about thst. Although we were offered to stay overnight by the company to check their system... So they may be genuine

I'll go with the best insulation available on the market today.
Insulate with a 100-200 mm and make it sound proof / water tight / airtight up to being a "passive maniac".

Once you have a closed container / framework,get a heat recovery ventilation.

Then,heating it and retaing that heat it will be your last problem...the smaller heat pump or boiler or radiator/underfloor heating systems combination with a nice multizoned automated controls ... will have to work very small / low energy transformation to get a temperature boost from a nice constant 15ish to 20ish.

Next,subject to budget,i will go with few solar tubes for hot water and PVs for electricity.IF budget tight,go for PVs and diverter.

Any decision,enjoy the adventure of self build...i envy you !

Gumbo

I’ve only used 12 units since April myself.

unkel

rolion wrote: »

DIY is fun ,challenging and tricky.

+1

I am far from a handyman, far from a natural DIY guy. But I got it done.

rolion wrote: »

Done with neighbour,cash and few "thanks" with a black foamy fresh liquid.

Same here. Did my first DIY PV install on my wooden garden shed together with handy neighbour who is in the trade and if I'm honest he did most of the work - gave him a few bottles of his very favourite wine. That was a DIY install that looks DIY

My next DIY PV install was on my kitchen extension roof. It was done to at least professional standards with high quality materials, all by myself with zero help from anyone. The sense of achievement / pride I got from that is worth more to me than the money I saved by doing it myself

niallers1

unkel wrote: »

+1


My next DIY PV install was on my kitchen extension roof. It was done to at least professional standards with high quality materials, all by myself with zero help from anyone.

How did it get hooked up to work with your house?