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've had a number of people come here who's architects have told them "nah you don't want to do that, its like living in a plastic bag"

This is shocking, there should be a mandatory FUD course to send architect and builders on. I had a very good estate agent around and saying if you refurb it must have underfloor heating as the market expects it. I was hoping it would never need to be heated as the preferred option :)

Yup, me to. Go away in depth of winter, turn everything off, houses loses 1C per day.

So Jealous:
Screen Shot 2019-10-03 at 10.17.47.png


This is the last 24 hours, a three degree drop doesn't look too bad (no heating on) but it certainly feels very chilly.
 
Great thread. I've had solar for 5 years, 2 EVs and the need for a new charger.

Probably getting a powerwall - as others have said, it's not only about the money. Currently trying to coerce Tesla into joining up car, powerwall and charger so that they incorporate the logic discussed previously.

The local rep is excited about the possibility, but dubious about process, so may have to pull the trigger and hope!
 
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Does the efficiency and sensitivity of the current range of solar panels come into the equation at all?

First up, some info to both qualify my interest and to justify the newbie mistakes I’m no doubt about to make!

I have neither an EV or solar yet but my model 3 is incoming (I hope) and I have accepted a quote on a solar PV for the house. However, I’m not a total newbie to solar. I Fitted a solar setup to my American RV last year and use it at locations without power throughout the year. That system has two 320w panels, a Veetus 1500w marine inverter and 4 x 110Ah batteries. Different to a house I know but it helps you learn the ups and downs (literally) of generation and storage. I use the motorhome regularly at motorsport and festivals (former employ of the event staging industry) so it’s enough to give me a taste of solar reliance and understand the cycles of charge vs battery use to a degree.

the one thing that has impressed me a lot is how little sun is needed to start generating energy. Way more than I’ve experienced on older systems. They seem to fire up and give a degree of generation on even the grimmest days. That’s one of the factors that has given me more confidence that even Lancs greyness might give me some incoming on darker days.

the whole feeding the grid vs self consumption element is the trickiest bit. But I’m deploying a self-protection approach for a worst case scenario. With FiT now long gone, VAT back to 20% as of two days ago and the uncertainty of the economy, I’m gambling that ringfencing oneself from the greed and disorganisation of the government(s) has some weight to it. Considering both the UK and US organisations are great at throwing renewables into speeches, neither are appearing to do either in any way that suggests it’s more than sound bites. I get that allowing the power companies the ability to create their own in and out tariffs opens up the market to those understanding the changing needs of, in particular, electricity consumption, I’m not convinced that the changes we're about to see in the economy aren’t going to force the hand of suppliers into higher prices. I may end up with a Powerwall I lean on whilst proclaiming the freedom it gave me in choosing my own billing model or I may end up with a big useless box which saves me nothing. But, whichever way you voted (this isn’t the place for such things so no need to discuss), we’re heading into some days of change. With ‘taking back control’ being such a buzzphrase over the last few years, I’m taking back control of my energy needs. It could backfire terribly but that’s the horse I’ve put my money on.

I’m still in the cooling off period for the Solar and the Powerwall so I read all of your comments with interest and I’m trying to learn.

I’m a big boy now with broad shoulders so anyone wishing to educate me if I’m being naive will be accepted rationally.

FWIW, I’m currently part of a household where two of us work mainly from home so daytime charging and daytime power consumption is worth factoring in. Let’s see how I get on eh? ;)
 
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Probably getting a powerwall

I know a local installer of powerwalls - he said Tesla have been bundling in a free TWC with power walls on some of the recent jobs he has done, may be worth asking :)

Does the efficiency and sensitivity of the current range of solar panels come into the equation at all?

My panels are 5 years old, new panels appear to be 50% more efficient.. The inverter magic and MPPT sort it all out. I'd happily put more panels up but consider it a bit wasteful to ditch panels for new ones.

Let us know how you get on & good luck ;)
 
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I know a local installer of powerwalls - he said Tesla have been bundling in a free TWC with power walls on some of the recent jobs he has done, may be worth asking :)



My panels are 5 years old, new panels appear to be 50% more efficient.. The inverter magic and MPPT sort it all out. I'd happily put more panels up but consider it a bit wasteful to ditch panels for new ones.

Let us know how you get on & good luck ;)

Thanks Fullerene. I’ll no doubt be sharing any findings.

on reading back my post, it looks a tad like money is my only driving factor. The environmental element is very much key here too. I have to confess I’m a bit of a bandwagon jumper here when I discovered how much fun a lifestyle change to greener living is. Regarding the house, I f we broke even with little to no coal being burnt I’d be happy. But savings are still very desirable.

The RV is our current bone of contention. Whilst it promotes a great lifestyle and a learning curve for being less relevant on a plug, it certainly isn’t very green. A 5.9ltr Cummins diesel isn’t doing anything for the planet. However, this summer, 6 people went to Spain with enough room for all, we flew zero miles and we lived pretty much off the sun when it wasn’t 40deg C and we needed to air con the thing to just be able to breath. At the moment, with our involvement in stuff that requires us being in fields a lot of weekends, I’m struggling to find a better alternative unless we return to ‘camping’ which doesn’t sit well with lots of camera equipment and the need to charge devices. I’m excited about the possibilities for a platform like the Tesla Semi and what it will open up as alternatives in recreational vehicles for the freedom of the road. With the battle between engine and batteries in a large RV, the idea of something where the drivetrain, the habitation side and the services all work together to cover all bases is exciting but that’s definitely one for another thread methinks.
 
new panels appear to be 50% more efficient

How are you measuring that? Are you perhaps comparing cheap panels of 5 years ago against the most expensive ones of today, or panels of a different size.

I've looked up the quote for a system we had installed 10 years ago, and those were 210W in a size of 1570x798.

Looking now for high output panels, I find some Panasonic ones that claim to be industry-leading efficiency: 330W (50% more!), but they are 1590x1053 (33% bigger). So some improvement in efficiency but nothing like 50%, and over 10 years. Those 10-year old panels probably weren't the best available at the time either.


There are some interesting trade-offs to be considered though.

Many people are/were constrained by FIT limits or DNO limits to a certain maximum power output. If you've got plenty of roof, is it better to go for the cheapest option that gives you what you need, or go for higher efficiency panels that leave you roof space for future expansion?

Given such a limit, is it worth over-fitting the panels to give closer to your nominal output on days with lower sunlight, knowing that you will throw away energy on the peak summer days, or just match panels to inverter?

All solar PV and heat your water electrically, or some solar thermal as well? (I've come down on the PV side of the argument, but it's not completely clear-cut).

One thing I'd love to know more about is what variations there are between panels at different levels of illumination.

Issues of shading and the relative efficiency of mitigation techniques are also not obvious.
 
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Efficiency only affects scenarios where you don't have enough space to fit the desired number of panels. I have high efficiency Panasonic panels. Even though I had the roof space, the reason why I went for the Panasonics is that I could achieve a more aesthetically pleasing array on my roof - they are smaller panels but generated almost as much power as larger (more standard sized) ones. They are apparently more efficient as panels start to warm up, but I don't think over a season it amounts to anything more than a few extra kWh over the course of the year. That is more important than anything is shading and how that is tackled. Without any planning for it, even the smallest bit of shade can cause massive power reduction - think of Solar like a hose pipe - you put a slight kink in the hose, the whole flow suffers. Except with PV, it may not be a slight kink and a leaf, dormer, adjacent property or even telephone cable can bring down the whole array if not planned for at the outset. I run Solar Edge optimisers as my array gets a big shadow passing over it at end of the day, or between Oct and Feb as sun passes between some trees. But there are other ways to deal with any problems. I personally chose Solar Edge as I fully understood my shading issue, but in recent times, they have been up sold to deal with problems that can be fixed in simpler ways such as dual MPPT tracking and/or SMA Optitrac global peak.

And don't believe any BS you may be told that some panels were made for UK weather. Looking at you Ikea with your super inefficient TFT panels. Close call that one.
 
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How are you measuring that? Are you perhaps comparing cheap panels of 5 years ago against the most expensive ones of today, or panels of a different size.

According to data sheets as purchased my CIGS panels were something like 12% efficiency, I seem to recall modern mono crystalline panels being ~ 18% so hence the 50% more efficiency gain.

Efficiency only affects scenarios where you don't have enough space to fit the desired number of panels. I have high efficiency Panasonic panels.

Much to my annoyance my roof as it stands couldn't fit another panel on it :( I know somebody who was arable farming in Australia - he said he didn't care about crop yield as the land was so cheap, you want more crops you use more land, don't mess around with expensive soil improvement. Meanwhile in the uk.. :)

Unfortunately my family and local planners would likely not appreciate me turning the garden into a solar farm, it might be great for a wildflower meadow between and under the panels.. ironically I imagine nobody has to apply for permission to astroturf their lawn as is the recent trend. Watching the opening sequence of The Lorax, Life Imitates Suess :confused:
 
According to data sheets as purchased my CIGS panels were something like 12% efficiency, I seem to recall modern mono crystalline panels being ~ 18% so hence the 50% more efficiency gain.

Ikea/Hannagin (?) by any chance?

Those panels were awful efficiency wise, but did look nice. I had the Ikea 'survey' (don't get me started on that) and they reduced the capacity as their in store planning was not accurate enough to cater for the restrictions they placed on them. In the end, I went elsewhere, and got nearly double the kWp for similar amount of roof space and iirc less money than the pre 'cant fit them portrait or that close to eaves' slashing of array size (iirc 3.6kWp to 2.4kWp, ended up with 4kWp). So yes, increase in efficiency, but 12% for TFT was a poor starting point when everyone else was already around 18% and Sharp/Panasonic were pushing 21%.
 
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yeah - don't get me started (new thread required), I did my own CAD drawing for the installers as the ikea survey had my panels over the roof windows... They do look lovely - it looks like my roof is covered with the Metallica black album.

Given such a limit, is it worth over-fitting the panels to give closer to your nominal output on days with lower sunlight, knowing that you will throw away energy on the peak summer days, or just match panels to inverter?

You can overtilt panels, to improve solar collection in winter... I did the maths on this on a spreadsheet I can't locate, I think it was all a bit marginal.

All solar PV and heat your water electrically, or some solar thermal as well? (I've come down on the PV side of the argument, but it's not completely clear-cut).

I went down the immersun route - I've saved over 1K GBP of water heating and I don't need to use gas boiler for a decent chunk of the year. The alternative was more plumbing and expense for the much more efficient solar thermal. so less roof space but more cost. Arguments to be had on all sides on pros and cons. I could fit an East & West facing solar thermal collector but it's PITA territory, plus I don't have a solar coil in the tank. however I did see this:

Solarcoil.co.uk Manufactures of solar retrofit coil heat exchangers

I believe made in UK, was looking at this when I was thinking of the solar thermal route..
 
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The house we moved into 2 years ago has a Worcester Bosch Solar thermal inbuilt into the roof. It works really well even though its 8 years old. Had a 4.4 KW PV system installed at the begiining of March along with a Sonnen 5KWh battery. The system is DC coupled which improves efficiency but poses some problems when using the zappi as it doesn't know when power is coming from the PV or battery. There are work arounds but its not seamless and the zappi app has no idea what the PV is producing just what is being exported
 
This is the last 24 hours, a three degree drop doesn't look too bad (no heating on) but it certainly feels very chilly.

Not surprised it feels chilly, its getting down to 18C, you need to do something about that :p :cool: :D :cool:

Temperature.jpg


This is going back as far as possible with lowest magnification - last 30 days history. Yellow line is the room temperature, lumpy green line is outside temperature, and other green line is the thermostat set point. Looks like it is at the point where heating would cut in, except boiler is turned off. Basically in all that time, even though external temperature has gone down to 5C-ish on a few nights, the room temperature hasn't changed. On days when the sun has been strong there will have been some solar gain, which building will have absorbed and hung onto for cooler days (thermal mass of internal walls is deliberately high).

I'm not doing anything clever here, this is exactly what the building is intended and designed to do :)

Basically in the middle of the last 30 days the temperature climbed 1C, and now it has fallen back again (lousy weather recently), and throughout it has oscillated 1C most days.

the whole feeding the grid vs self consumption element is the trickiest bit.

Most people must be out-to-work Mon-Fri and unable to take advantage of the PV, exporting it, and getting "presumed 50% export" payment. I too have the presumed 50% export payment FIT, but I don't think I have ever actually exported a single kWh ...

If you've got plenty of roof

I would hazard that:

South first, West second because it peaks later, overlapping when folk come home from work / cook evening meal (for those may even be better than South) and East last (generates early, most probably when even at-home people are using very little power).

North = better have good FIT kickback!

I have high efficiency Panasonic panels

I bought Panasonic panels (more than 5 years ago) because a) all-black looked better, and b) they are warranted to lose what seems like only a tiny amount of generating ability over 20 years.
 
East last (generates early, most probably when even at-home people are using very little power).

I'm thinking of having some east-facing on our project, where the hot water will be electric. Depending on the time of year, it will heat the water for my morning shower, or re-heat the tank afterwards.

This being part of my plan to have lots of PV for flexibility rather than separate solar thermal.
 
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This being part of my to have lots of PV for flexibility

My sympathy ... very difficult to get the prediction / mix right. Could have Battery/PowerWall? ... of just buy from Green Grid and let them worry about building-out the right mix?

The last seems defeatist to me, but might actually be the greenest solution - #1 Daughter tells me that embedded carbon in PV panels is not affordable at this time (i.e. need to produce as little CO2 as possible, until we have figured out how to fix the problem) and over lifetime of PV panels getting some from grid now, and later all of it from North Sea Wind, will be less CO2 overall. Feels wrong to do nothing ... but maybe all my mucky mates, who are doing nothing :(, will be proven to be right. That would Totally T me off!
 
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very difficult to get the prediction / mix right. Could have Battery/PowerWall?

My thinking here is to get lots of panels now (since we are replacing the roof) - batteries and other changes in how we use it can be added later quite easily, while changing the panels will be expensive - always is anyhow (scaffolding etc), but particularly so here where we may go roof-integrated with the panels and so save on other roofing materials; also have odd shaped roof so although there's plenty of space if you just pick the prime location for the initial panels then fitting others around them later is tricky.

It's certainly a win in money terms, but maybe less so in CO2. I will do more research.
 
Whilst roof integrated look great, often nigh on invisible, they do suffer from lack of cooling on the rear which can impact efficiency. However, adding more panels can offset this.

What cannot be offset though is potentially increased fire risk. I know there were some issues with integrated panels in another country where they were more common (Neverlands?), but I cannot remember the exact circumstances. May just have been a faulty set of panels but because they were integrated, it made more visible headlines.
 
we may go roof-integrated with the panels and so save on other roofing materials

My original PV panels were installed on a newly built part. We just put wriggly-tin on the roof, and PV panels on top. I never checked the sums, compared to a Slate roof (with no PV), but probably worked out quite well.

Panels-over-roof will, I think ?, keep the actual roof cooler in Summer, and thus the attic below the roof.
 
This being part of my plan to have lots of PV for flexibility rather than separate solar thermal.

I think this is sensible - there's a limit to how much solar thermal anyone will use - though there was grand designs a while back that someone had many massive solar thermals units on a property.

Panels-over-roof will, I think ?, keep the actual roof cooler in Summer, and thus the attic below the roof.

I thought this - however in practice it made no measurable difference.

I'm not doing anything clever here, this is exactly what the building is intended and designed to do

Awesome - this is what every building should be required to do. Though may I ask do you have another half that likes it a little bit warmer? What happens?

(I know this is a Tesla Forum but I really appreciate the insight I get from this thread, so thanks for everything!)
 
Though may I ask do you have another half that likes it a little bit warmer? What happens?

Change other halves?!

I think, in practice, that is a non issue. The temperature is every even, with no draughts, so I suspect it is "different" and that hot/cold-person issue becomes less of a concern.

The Passive House book I read said something like "Internal window surfaces must be no more than 4C colder than room, that is the point that colder air will "fall". So basically the lack of temperature difference means you don't get convection currents, and I think it is that air-movement which makes you feel a cold draught, and the "warm blooded" reach for the thermostat and turn it up to compensate - which of course then exacerbates the problem. So without the draught both the Cold/Hot bodied folk are comfortable. Maybe?

Bigger problem is when you have a dozen mates round in mid winter. Have to open the windows because the mechanical ventilation is not designed to shift that much excess heat! Particularly Cold winter? Get some mates round for a beer :)

there's a limit to how much solar thermal anyone will use

I'm not a fan. We have Solar Thermal on the main house (evacuated tubes), for Domestic Hot Water, and also for the pool (flat panels). Both need a visit from the Solar Guy to bleed air, or fiddle with something, nearly once a year on average. That said, I know people who have had Solar Thermal installed for 10 years and it has never missed a beat. I reckon (subjective analysis of forum posts) its 50:50.

if I was doing it again I would install PV instead and use a heat pump to heat the water. Bit difficult for DHW - heat Pump not great for lifting temperature to "hot", perhaps use immersion instead of heat pump? - but for pool it would mean that the heat pump could be run off grid at start/end of season for a boost, and in mid Summer instead of heating the pool to "Lobster" the excess power, if PV rather than Solar Thermal, could be put into House or BEV. More options with PV than Solar Thermal, and less maintenance
 
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I'm not doing anything clever here, this is exactly what the building is intended and designed to do

Actually, thinking about it, this may benefit from some explanation.

There is a fair amount of heat generated inside the building. Lighting (not much these days, since Incandescent became LED), Cooking, Electronic stuff. Because the building is well insulated that heat is trapped in and, together with body heat, contributes to the heating

Passive House design has a peak heating allowance (i.e. in addition to waste heat from cooking) of no more than 10 W/m2. A 3 bedroom house (first number from Google) is 1,200-1,300 square feet (including all lived in-space, even hallways) . So 3 bedroom house has a peak heat requirement of a 1-bar fire. For the whole house.

Air leakage is stipulated at 0.6 air changes per hour with the house pressurised to 50 Pa (they put a blower in the front door and pressurise the house, and then wander round with a smoking Joss stick - you can immediately see any air escaping as the smoke finds the gap; we had a seal missing in a window, the effect on the Joss stick was dramatic :) ). For a Passive House the requirement is usually easily met (typical real-world Passive House builds usually achieve half that at 0.3). By contrast I think the Building Regs requirement for new build is 10 air changes per hour (at 50 Pa) and if you are lucky you will get down to 5. That is typically achieved by applying loads of mastic at the leaks - e.g. under skirting boards, which the carpet fitters then cut out so they can fit the carpets under the skirting boards :(. And so on.

For anyone interested I recommend The Passivhaus Handbook: A practical guide to constructing and retrofitting buildings for ultra-low energy performance. It has plenty of technical break-out panels, for those wanting the numeric theory, but for the rest its an easy read of the things that need to be achieved, how to oversea the Trades to guarantee the outcome, and so on. (Lots of diagrams etc. personally I find that sort of thing hopeless on Kindle, so for this I prefer a paper book).
 
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