Help - does anything make financial sense?

donalh087

Looking for some advice. I'm a noobie so be gentle.

I am about to start building a 2500sq ft single storey house. It is facing South with lots of triple glazed glass. I am looking at all ‘alternative’ energy options to reduce my environmental impact and to be as ‘off grid’ as possible.

I am looking at all the usual suspects, air to water, heat pumps, solar, geothermal etc. . My problem is that none of them seem to make financial sense on a ‘life cycle’ basis. Am I right? Or am I missing something?

I understand the social benefits but is there anything that makes independent financial sense?

rolion

Best advice: insulation at the best plus airtightness gives you very little to warm up no matter what "heating source" you will use.
Once you insulate,you will need HRV.

Then,PVs or solar tubes panels for water and/or electricity.

None of them makes financial sense today but gives you a god feeling when you see the two digits only ... bills !

PV does make financial sense but unfortunately for some the return on investment depends entirely on what you invest in the first place.

donalh087

Sir Liamalot wrote: »

PV does make financial sense but unfortunately for some the return on investment depends entirely on what you invest in the first place.

I don't understand. Should I have specified I am in Ireland?

rolion

Yes and No.

A quick reply,around a cup of tea...

In Ireland there is no payment for extra energy supplied in the grid,when your panels are making in excess.
More than your household appliances can consume at a specific moment in time.
So,to be effective and increase the return of the initial investment,you need around 5Kw in solar PVs to have
a good day with zero electricity "borrowed" off the grid.

For the solar tubes,better,much better efficiency in relation to hot water only but kind of difficult to install it as DIY.


BOTH above systems are subject to God Sun's behaviour,with the winter 4 months minimum returns.

For more infos,lots of information on this topic read on the section.

Ether way...enjoy it.

PS
I have enough solar tubes so that i can switch off the heat for the DHW from April until November.
I have 5Kw in PV panels to consume only 5kwh per day from the grid,around 60c per day.
Both,on good sunny days.
And both very expensive initial purchases,less expensive as install was DIY.
BUT best investment..external and internal insulation !!!

The less PV you have the less chance you have of giving power away for free. East West makes more sense for self-consumption for most lifestyles than South.
Trying to use every last electron you produce gets expensive.

5kWp PV should be giving you ~15kWh a day.

ted1

Have you looked into building a passiv house? ( an actual certified one)

_Brian

I think others here have hit the nail on the head.

You should focus on the best passive build you can and the more you move in this direction the less you rely on energy consuming heat sources.

donalh087

When I started this project I was imagining a Tesla battery powered house charged by wind and sun and night rate electricity. The house would be triple glazed with hot water from solar panels and underfloor heating from geothermal.

It all technically exists but at a huge price. And if it doesn't make financial sense then it is just social decoration. I may as well buy pieces of art to admire.

As far as I can see the 'no-brainer' rules are 1. Orientate the house to the south 2. Insulate the hell out of it 3. Lots of South facing triple glazing. 4. Airtight with a ventilation system.

After that - is there anything else to do?

donalh087

@Ted1 Yes, considering the quotes at the moment. I think the 4 no-brainers bring it close to passiv (not certified). A heat exchanger would complete it but it is quite expensive.

ted1

donalh087 wrote: »

@Ted1 Yes, considering the quotes at the moment. I think the 4 no-brainers bring it close to passiv (not certified). A heat exchanger would complete it but it is quite expensive.

There's an energy show next week, some of the electricity providers may announce incentives for such.

https://esb.ie/blog/sustainable-innovations/customer-innovations/2017/03/16/putting-energy-in-our-homes

dathi

[QUOTE=donalh087;103075154

As far as I can see the 'no-brainer' rules are 1. Orientate the house to the south 2. Insulate the hell out of it 3. Lots of South facing triple glazing. 4. Airtight with a ventilation system.

After that - is there anything else to do?[/QUOTE]

yes comply with part L of the building regulations with regards to the provision of renewables.

quentingargan

Depends on your view of financial sense. Solar PV can stack, but payback is not the 5 years that some snake oil merchants claim.

Hardware for a 2.2kw system (8 x 275W all-black panels) would cost about €2400 plus VAT including a decent immersion diverter to send surplus electricity into the hot water cylinder. Installation during the build will cost about €400 more. On a south facing roof, that would produce about 2,000 KwHrs per year.

If you use 1/3rd of this (and that would be very modest) to displace daytime power at 18c, and the other 2/3rds to heat water (saving night rate 9c or oil/gas 9c) your average electricity saving is 12c. So you have payback of €240 per year on a system that cost you €2800, giving about 8.5% return.

HOWEVER – you’re going to have to do something for part L. Sticking in the usual “Part L” 3 panel system is going to cost you more than half the price of an 8 panel system, and will do very little for you.

donalh087

@Quentin That is starting to make more sense. I will investigate further.

air

Sir Liamalot wrote: »

5kWp PV should be giving you ~15kWh a day.

Not in Ireland it shouldn't.

rolion

air wrote: »

Not in Ireland it shouldn't.

TODAY's PV report:





Energy over 3 months period:





iBoost diverter works,today:




Estimated RoI on a day like today:

That was a conservative figure.

AC coupling losses are a major factor.

air

Not sure what either of you are saying, your own PVGIS figures show a daily average of 11kWh Liam.
Your slope is sub optimal but the orientation is due South (which isn't always feasible) and that model makes no allowances for shading.
I have a 4kW array for about 3 years, currently undergoing an upgrade in size.

air

April: 16.5kWh
Installation losses: 14%

air wrote: »

Your slope is sub optimal

Is it? I prefer a little all day than a peak at midday.

air wrote: »

that model makes no allowances for shading.

Should it? Would it not be sensible to not put panels where they suffer from that?

air wrote: »

I have a 4kW array for about 3 years, currently undergoing an upgrade in size.

Of the last 7 years I've spent 4 living off grid, and the last three I've been mostly month on month off.

I've only 3.5 commissioned systems between my house and motor I've been upgrading them all since their install.

air

What you said implied that one could expect an average of 15kWh per day from a 5kW system. This isn't possible in Ireland.
Yes, 15 degrees is not a good angle for optimising total production. The general rule of thumb is to match your tilt to your longitude. 15 is in fact the generally accepted minimum slope that is acceptable without requiring cleaning in this part of the world.
It's unrealistic to expect zero shading in a suburban environment (where the majority live). A nearby house might only clip the sunlight near dusk but it will still be enough to affect total production.

Off grid experience is well and good but unless you have a fixed multi kW system in Ireland you're not really in much position to comment on expected production from one.
You also reference AC coupling which refers to hybrid grid tie battery systems which are irrelevant to the majority of users. A standard grid tied system only has small DC losses and inverter losses which together will total a lot less than 14%.
You've a propensity to pontificate about things which you have no direct experience of and sketchy knowledge. This has lead you to post incorrect information on this thread and another where you tried to speak about lithium batteries despite having no direct experience of them or knowledge of their charge profile.

air

air wrote: »

What you said implied that one could expect an average of 15kWh per day from a 5kW system. This isn't possible in Ireland.

Sorry for the misunderstanding air. I was not my intention to imply that PV harvest is constant year round. It was the end of March when I posted and I'd been enjoying the last few weeks of my systems performing to design hence I said 5kW ought to produce 15kW day. Much as I didn't say from here to October I didn't say year round either.
PV during the months it is useful March to October will on average conservatively produce 3x rated in Wh.
You can hang PV on the roof until you run outtov space and you'll still harvest a multiple of not very much from November to February.

air wrote: »

Yes, 15 degrees is not a good angle for optimising total production. The general rule of thumb is to match your tilt to your longitude. 15 is in fact the generally accepted minimum slope that is acceptable without requiring cleaning in this part of the world.

Last time I looked at the numbers 15° S was second only to 40° S, leading East & West orientations. It does take more of a hit in the Winter accepted.

Useful power all day long is more valuable to me than a peak I donate to my neighbours when I am out. On batteries it has more chance to go direct to load than chemical inefficiencies. It's not about the numbers on paper it's about the practical usefulness.
If my battery systems are idle then they enjoy a longer float too.

air wrote: »

Off grid experience is well and good but unless you have a fixed multi kW system in Ireland you're not really in much position to comment on expected production from one.

Are these systems not upscalable? How different is 15kW from 10X 1.5kW.
One of my installations has a 0.5W base load. Are you suggesting this can't be applied to a grid tied installation?..perhaps that's a tangent, I think it's relevant.

air wrote: »

You also reference AC coupling which refers to hybrid grid tie battery systems which are irrelevant to the majority of users.

AC coupling is putting an extraneous AC or DC source on an AC line. eg Direct Current PV on an Alternating Current installation. My meaning was what the panel produces and what the inverter outputs are different figures.

air wrote: »

A standard grid tied system only has small DC losses and inverter losses which together will total a lot less than 14%.

Say 3% on wiring losses because that's the max allowed.. cost of cable and all that...
Can you post a graph of the efficiency curve on a standard inverter at a standard string voltage from 0 to 100% load, 30mins continuous duty @ 25°C ambient for each data point to establish a norm weighted efficiency?

Let's just pretend system efficiency 95%. 40° South, no shade. Annual daily average 14kWh..pretty close

air wrote: »

... and another where you tried to speak about lithium batteries despite having no direct experience of them or knowledge of their charge profile.

...as you bring that up again...and I believe the original point of the matter was which algorithm was more complex...
How does a lithium battery behave if you are using Constant Voltage with no cell monitoring and there are dead & shorted cells (of which there can be hundreds to choose from) in a string?

I know we have our disagreements air, I hope you don't take my comments as antagonising, you have inspired me to investigate many issues in our perhaps heated engagements, as far as I'm concerned every day is a school day and I appreciate your input.

air

PVGIS gives 13.8kWh per day assuming 95% efficiency as far as I can see. The fact remains that this assumes a perfectly due South unshaded installation.
The rest of your post is a wander into off topic irrelevance as usual.

The basic point I'm making is that it's unrealistic to expect 15kWh a day average from a 5kW system in Ireland.
Firstly from PVGIS 13.8kWh is the max you can theoretically achieve.
Secondly you need a perfectly due South facing roof with at least 40m2 free area, zero obstructions or shade.
I would guess fewer than 2% of homes would have such a roof.
Even if some have space for a ground mount it's even less likely to be totally unshaded due to being lower.
As a consequence most people installing will end up with a mixed orientation, less than perfect installation - much like my own.
I'll shortly connect up my first East facing 1kW array which will bring my total install (on a house with better than average orientation and shadowing) to 5kW peak.
My total annual production will at that point still be below 4000kWh or 11kWh per day.

I appreciate you have plenty of experience but this is a simple non technical thread where people want simple answers.
Right now, I'm giving people advice that unless they have a truly exceptional amount of space available, they can expect about 30% less energy from a domestic 5kW system than you originally claimed.
That is all.

air

air wrote: »

it's unrealistic to expect 15kWh a day average from a 5kW system in Ireland.

Agreed, I never said average.

listermint

I find people often disregard the comfort and convience factor when they talk about renewables .

Not everything comes down to figures you have to account for that too.

quentingargan

listermint wrote: »

Not everything comes down to figures you have to account for that too.

There is a certain satisfaction in having a bath, knowing the the hot water came from the light, and not from the dark of a well full of oil that would be best left in the ground... :cool:

Calahonda52

donalh087 wrote: »

Looking for some advice. I'm a noobie so be gentle.

I am about to start building a 2500sq ft single storey house. It is facing South with lots of triple glazed glass. I am looking at all ‘alternative’ energy options to reduce my environmental impact and to be as ‘off grid’ as possible.

I am looking at all the usual suspects, air to water, heat pumps, solar, geothermal etc. . My problem is that none of them seem to make financial sense on a ‘life cycle’ basis. Am I right? Or am I missing something?

I understand the social benefits but is there anything that makes independent financial sense?

Is all the house facing South?
In what way don't they make financial sense on a LCCA basis?
Whats the basis for lots of TG?

IMO, the social benefits argument is a fagazie, once you do the full LCCA and include the math on Carbon.

rolion wrote: »

Best advice: insulation at the best plus airtightness gives you very little to warm up no matter what "heating source" you will use.
Once you insulate,you will need HRV.

Then,PVs or solar tubes panels for water and/or electricity.

None of them makes financial sense today but gives you a god feeling when you see the two digits only ... bills !

Over a cup of tea, I suspect you meant once you airtight you need mech ventilation, as opposed to insulate.:)

donalh087

Calahonda52 wrote: »

Is all the house facing South?
In what way don't they make financial sense on a LCCA basis?
Whats the basis for lots of TG?

Is all the house facing South? Well it is in the middle of a flat field so technically it faces all directions. We have one long unobstructed roof facing almost directly south though - if that is what you mean.

In what way don't they make financial sense on a LCCA basis? In that the upfront cost is never recouped. It is the kernel of this thread. Quentin says the annual return of €240 on an investment of €2800. So it would be 12 years before you see any margin. It starts to make a bit more sense if you need to spend on Part L. It depends then on the monetary value you, personally, want to attach to the nice warm feeling you get in a 'free hot bath'.

Whats the basis for lots of TG? Triple glazing benefits, for me, are twofold. Increased energy efficiency and preventing overheating in the summer.

hytrogen

donalh087 wrote:

Whats the basis for lots of TG? Triple glazing benefits, for me, are twofold. Increased energy efficiency and preventing overheating in the summer.

Perhaps but you'll notice your north facing rooms will be darker, tripple glazing is (cost) better for noise reduction than heat retention based on their fixed return values according to some BER software I got to play around with one day before I upgraded my home. I ended up selecting double glazed in the back downstairs as it is a north facing back garden and I'm glad I did. The neighbours adjacent got double glazed throughout, we've similar floor spaced houses and their bills are relatively similar in terms of heating (both on gas) but my bedrooms are far quieter than theirs and we live on a very busy road.

BryanF

hytrogen wrote: »

Perhaps but
1. you'll notice your north facing rooms will be darker,
2. tripple glazing is (cost)
better for noise reduction than heat retention based on their fixed return values
3. according to some BER software I got to play around with one day before I upgraded my home.
4. I ended up selecting double glazed in the back downstairs as it is a north facing back garden and I'm glad I did. The neighbours adjacent got double glazed throughout, we've similar floor spaced houses and their bills are relatively similar in terms of heating (both on gas) but my bedrooms are far quieter than theirs and we live on a very busy road.

1. No you won't - solar factor can be as little as 10%
2. Great for noise reduction - don't understand your point (comparison to heat retention?) heat retention of 3G will be noticeable better assuming u-value,AIr-tightness etc
3. According to the worst piece of software ever
4. Comparing two houses on bills alone is pointless

Also Renovating is very different to a new build.