This is not a happy story but it needs mentioning.

As earlier posts have noted, Porter’s is equipped with two strings of 9 Solar PV panels, adding up to 3.96kWp. There were problems with one of the strings back in 2014 and by early 2015, and after a lot of hassle, I got it fixed. This string was still generating noticeably less than the other, but the difference was less marked.

Since then, there has been a gradual deterioration in the performance of that string (string1). More recently I found about about optimizers. At the risk of telling people what they already know, in the days when these PV panels were fitted it was normal to have one or two strings, just as I have. You could have a system with a separate inverter on each panel but this made an already expensive system even more costly, so it didn’t happen very often.

Since then, the concept of optimizers has appeared, of which a well known make is Solar Edge. (See their website, where there will be all the information that you need!) In brief, an optimiser is connected to each panel and matches its impedance, so enabling it to produce as much power as possible. Better still, the optimiser outputs are all brought back to a single, simpler inverter. Each panel works at its best and shading on one panel no longer affects the whole string, but just that panel. They (Solar Edge) claim that a performance improvement of nearly 25% is possible.

Attractive, what? If I had these fitted I would find out very rapidly which of my panels was below par (if they were and it was not poor contacts), I could get it/them replaced against the warranty (less than 10% degradation in 10 years) and the optimizers themselves would deal with the early morning shading which affects one string.

So a search gives me names of companies which fit these things. One (no names) wanted £150 just come to look at the system, which being in-roof and not on-roof is relatively unusual. And I also want assurance that if any extra holes really need to be made, I know exactly what and where – this is a Passivhaus after all, and maintaining its air-tightness is important.. I looked for another company. My view was, and is, that charging to look at a £3,000+ job is not a good attitude.

I found another company who had a much more positive and can-do attitude. I was quoted a sum to do the job. Scaffolding was put up and operatives arrived. I was told that there some problems and they went away. The boss was in touch fairly shortly afterwards and I was told that it was not possible to fit optimisers, because there was insufficient room behind the panels – between the panels and the roof. He was not interested in finding out whether any of the panels were defective. No charge was made and after a while the scaffolding company came and took it away.

Essentially I am stuck with a slightly defective system – well, one half of it is slightly defective. The company which made the panels (Romag) has been bought out by another company (Dellner) which, I have been told, is not interested in the solar panels part of the business – so that are no easy replacements available; and I cannot have optimisers fitted.


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Let’s look at Solar PV again

If you look back through the posts to 2011 and 2012 the solar PV system on the house was installed as the house was built. It is an “in-roof” system, rather than “on-roof”. Apart from anything else, it save tiles – or in this house’s case, slates. (I started to write this in August, btw.)

It has been a frustration for some time that, if there was a day time power cut, the solar PV turned off. The inverter could see the mains or lack of it, and shut down. Clearly, without some safety devices it has to, so that the linesmen repairing the fault don’t get electrocuted by the power that the system would continue to export to the grid. But I have considered that it should not be beyond the wit of an electrical engineer to create system that, in the event of mains failure, isolates the house from the mains and makes it impossible to re-connect until the power outage has been rectified. And, indeed you now can. Interesting video on the Fully Charged website showing the big “backup” box, which does just that – it switches over to the local battery instantaneously. And the solar PV continues to charge the battery/supply power to the house, provided that the sun is shining etc. But the key word here is battery.

To go back a bit. When the system was installed on this house, the Feed in Tariff (FiT) had just reduced from (very roughly) 40p/kWh generated to about 20p. Still worthwhile. Since then the FiT has been withdrawn – but the price of solar PV has much reduced. Whatever I write here will go out of date but, again very roughly, it’s now about £1 per watt peak installed. So a 4kWp system should cost roughly £4,000.

So where are we with batteries? When I last wrote about this, it was still far from being a sensible return on investment – I would not save enough (of the cost of) electricity to get my money back on the costs of a battery system – by a large margin. I don’t have that amount of spare cash to be able to indulge that level of “green altruism”! And, in my opinion, it still isn’t.

Step another bit forward – many of you will have seen articles about “V2G” which stands for Vehicle to Grid. If I had an electric vehicle (EV), then perhaps I could use its battery instead of buying one for the house separately – I’ve spent A Lot Of Money on an EV, why buy another far from inexpensive battery? Well, it’s coming, though not quite yet, I’m told.

I am in the throes of joining a trial called Powerloop, an experiment set up by Nissan, Octopus Energy, Octopus Electric Vehicles, UK Power Networks and two academic partners (can’t find their names at the moment). Essentially, provided I am in UKPN’s area, am prepared to lease a Nissan Leaf from Octopus EV, move to Octopus Energy (single tariff), am willing to connect the car 12 times a month to the special charger/discharger (Wallbox) between 6pm and 5am I will get paid £30/month. The Wallbox charger is supplied and fitted free and becomes mine at the end of the trial. See the Powerloop website, rather than my writing all the details here and possibly getting them wrong. You could join too. At the time of writing (October 2020) Octopus/Powerloop told me that there were still vacancies to join the trial. Oh yes, you have to own your own home and have off-road parking.

Checked out the car at a local dealer. Thought it might be a bit noddy. No! It’s rather larger than the Peugeot 2008 we have at the moment, really very well equipped and finished and with serious poke under the pedal. We both liked it so we’re prepared to go ahead. Currently going through the G99 process – which checks to see if UKPN happy to have this house connected to their local grid. Well, I would hope so, as we already have Solar PV which I am – obviously – hoping will charge the car’s battery at least some of the time.

Watch this space.

I’ve also looked in to Solar PV optimisers – but that’s a separate post.

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It’s time to bring this up to date. I see that it has been a full two years since I wrote something about this house and our living in it. The frequency fell away because, well, the house went on doing its thing and we went on doing ours.

We went through last winter and, unlike the previous one when I had to start raiding the shed containing the next winter’s wood, we got through well. A less harsh/cloudy winter – and better wood. I say “got through”. That gives the impression that it was a struggle and a worry. It wasn’t. There was plenty.

That old shed – which was built of the old pallets and lumber left over from building this house itself – itself became firewood. Burning this was fine – except that I was riddling the ash to extract the nails. The ash – not much ash on a daily basis – gets put in a metal bucket. Metal, in case of accidents. See later! But I don’t want a lot of nails in the compost heap, which is where the ash goes. Relatively recently I read that it was better to put ash in the compost heap than directly on the soil in the garden, especially in winter, as the rain has washed away the goodness by the time the plants start growing, so there’s no benefit. Put it in the compost and it will still be there when the compost is spread on the soil later.

Moving on as this is not a gardening column – there’s not much ash because dry wood, burnt properly, doesn’t leave much ash. The chimney gets swept every year (of course) in the summer and the sweep is always very complimentary about how clean the chimney is. #smug

So the built-out-of-old-bits-of-wood-with-a-tarpaulin-over-it shed became firewood. Most of the wood which had been in this shed/store, moved – well, I moved it – to the ready-use store for the next winter. But of course the rest of it, and the deconstructed shed itself had to have somewhere to go. I had to be able to keep it dry and where was any other wood to go? And for the following years(s)? So we build a purpose made wood shed. Yes, with opposed slats outside and inside the studs, alternating with gaps! This is the sort of thing I am told you find in Scandinavia. It keeps the rain out but lets the wind blow through. I’m really quite proud of it, even if it doesn’t look terribly log-cabin-ey.

Purpose made woodshed

And it works! The wood dries. And as the photo shows, there’s a lot of wood there for winter 2021-22 already. With most of my other occupations cancelled by coronavirus, there’s been plenty – too much – time to cut/split/stack wood.

Oh yes, the accident. One day, some few years ago now, there must have been unseen (obv) charcoal embers in the ash. And it was shovelled into a (plastic) bucket and put back again in the back lobby (what our architect was pleased to call the boot room – it’s the “airlock” for the back door). Not that long later, the lobby was full of smoke, the plastic bucket was melting and flames were beginning to appear. There are smoke sensors throughout the house – but not in the lobby. It was all put out very quickly and easily with a quick jug of water, fortunately. The smoke alarm went off very shortly after the door to the lobby was opened of course, the noise of which makes it difficult to remain calm (get the jug of water before you open the door) and is quite bad for the blood pressure! But a salutary lesson. It could have turned into a bigger fire before the smoke got to the sensors. We now have a metal bucket – so if the worst happens and the embers have a new lease of life there will be smoke but no fire.

Next post will be revisiting the Solar PV. Things have moved on in the electric world and it’s time to revisit this.

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The Last Barrow

Been heavy on wood, this winter – lots of grey days – so this morning I brought in the last barrow-full of wood from what had been a 6 deep stack that I’d built last summer.  To be fair, it was a very full barrow-full.  Here’s a picture of that last little pile.

Also to be fair, some of the wood wasn’t that good.

The last barrow 28-March-18

Some couple of years ago, a friendly farmer let me cut down what was left of a dead tree.  It was pretty rotten in places then, and after I’d cut it up and split it and left to it to dry for a couple of years – well the woodworms had had a fine old time.  So although there was quite a lot of it, it didn’t last long in the stove.  There was a period this winter when a barrow-full would barely last one fire of an evening.

So the stacks beside the stove are full but if we need more – and I’m pretty certain we will need more – then it’s going to have to come out of what I’ve earmarked as next year’s wood.

The future?  I’ve written about this a while ago.  I can see a time coming when I shan’t want to cut, split and stack any more wood.  Been there, done that, got the callouses (no t-shirt available!).  I’ve already got wood for 2 more winters without chatting up farmers or buying in logs.  Much of it is already cut and split and then there is the second of the original woodsheds – well, shelters – built of pallets and off cuts from building the house and that itself will be a goodly part of the final stacks.  We burnt a fair amount of the first original wood shelter this winter – pallets and the like, and there’s been a good crop of ironmongery.  This gets sieved out with the charcoal and, as I don’t want the nails to end up in the compost heap, there’s a second sieving of the ash to get the nails missed on the first sieving – all picked out by hand – and, you’ll be pleased to hear, recycled.  And what then?

We went to Ecobuild earlier this month, hoping to be able to talk to pellet burner manufacturers and suppliers. Only found one and he was a supplier of large boiler-house equipment.  This differed from when we last went, about 3 years ago, when there seemed to be several.  Ecobuild had a completely different flavour/topic set this year.  We got one contact name which we’ll follow up in due course but I’d hoped to have more conversations and perhaps get some reference sites.  When we were specifying equipment for this house, it was not possible to get a pellet burner that you would want to have in your sitting/dining room which put its heat into water, only into space.  Those that heated water clearly belonged outside in a boiler house.  But time has moved on and it is now possible to get a good looking stove/boiler.  But rather than just look at them on the internet, I wanted to talk to people about them and see them for real.  Maybe next year.  My worry is that they may be noisy.

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Will the wood last out?

Been a grey winter.  Lots of fires, lots of wood burnt!

We started the winter with six stacks. Admittedly, four of them were almost entirely of weeping willow – and that’s very light and burns quickly.  We could get through a whole barrow-load in an evening, so it is not surprising that we used a lot of wood, in volume terms.

Here’s picture of the wood store on March 2nd.  You can see the slatted back – there’s no more after this.  But – and it’s a big but – all the wood left is really good wood so it lasts well and we get 3 or 4 fires out of a barrow-load.  But we still have to get through to April.

There is other wood, of course – but it’s earmarked for next winter and may not all be as dry as I’d like it to be.  Burning damp wood is considered bad news.  You don’t get as much heat out of it – perhaps obviously as the water has to be boiled out of it before it will burn – but almost worse is that you clag up the flue with tarry deposits.  Up to now the sweep has been very pleased with us – all he gets out is a small quantity of dust. (Curious to be pleased to be praised by one’s sweep!)  And so we know that the wood we’ve been burning is dry.  The wood store is the gap between two sheds, about 1.5m wide with a light corrugated plastic roof and a slatted back so that the wind can blow through but not the rain.  It seems to work OK.  The ground is gravel (plus the inevitable leaves which blow in) so even the bottom layer doesn’t get too wet from the ground.  We find the remnants of the odd mouse or bird nest as the winter progresses – empty, fortunately!

As described elsewhere in this occasional blog, the house has tiled floors – so we just wheel the barrow into the house.  What?  Take a wheel barrow into the house!? Well, why not? There may be a slightly muddy wheel track but not much because the route from wood shed to fire is all gravel or paving.  Just make sure you don’t hit the walls or doorways.

Later – quite a lot later, sorry – well, it did last out – we took just one more barrowload out of this and I’ve now filled it up again


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Three year logburner record

In these posts I’ve argued for some time that the Solar PV is a “nice to have” but is not really part of the performance of the house – that is due to the air tightness and insulation. So whether one has solar PV or not affects the energy bills, but not how the house behaves.

When the visitors come on the International Passive House Open Days – see https://passivehouse-international.org/index.php?page_id=262  – it will be interesting to hear what they say about Solar PV.  See the slightly earlier post – we are ID5042 and seem to be the only Passive House in Essex (indeed, most of East Anglia) which is open this year.

Anyway, the Feed-in-Tariff isn’t anything like as attractive as it used to be, even though the cost of the panels has fallen considerably, so the sort of payback that we’ve been getting is no longer obtainable.

On the other hand the Solar Thermal panels and the Logburner, both working with (into?) the Thermal Store are key to the thermal management of the house – not forgetting the big, south-facing windows.

So it may be of interest to publish the graphs for the last 3 years showing the number of times we had to light the logburner and how many barrows of wood we used.  I regret that we didn’t make a notes for the first winter we were here but it would not have been representative anyway as it was the end of October (just over 4 years ago now) when we finally moved in – into a cold, damp house.  I remember that we burnt quite a lot of wood at the beginning getting the house up to temperature and to begin to dry it out.

So here are the three graphs




I’m sorry that they are not clearer – this seems to be the best I can manage within my limited understanding of WordPress.

In table form

Year Fires Barrows
2013-14 96 35
2014-15 89 33
2015-16 103 39

And I note, with mild interest, that in every year we had to light the log burner in Week 42. And we’ve just done so again this year.  Wasn’t 42 the answer to life, the universe and everything?

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Now – Porter’s is a certified Passiv Haus!

Hurrah!  We’ve just received formal agreement that Porter’s meets the Passiv Haus – Passive House – standard.

So now we’re passive house ID5042.  And the PH organisation across the country is holding Open Days, on Friday 11th to Sunday 13th November.  So you can go to see Passive Houses near you.  And we’re opening Porter’s on all three afternoons. Go to https://passivehouse-international.org/index.php?page_id=474 , click “Come and have a look!” which will open the list of buildings – several hundred. More detail on each if you click it. And there are flyers to download (small and large).

Dr Roderick Williams has been working on our behalf with WARM, which is one of the few UK based Passivhaus Certifiers working on behalf of the Passivhaus Institut, Germany, to achieve this certification.  It would have been easier and almost certainly quicker to have done this as the house was being built.  But we were under considerable financial pressure at the time and the additional expenditure did not seem a good idea then.

BUT – we’re not a zero-carbon house – not quite, so we’ll have to relinquish this claim. While it’s certainly true that we get all our heat and hot water from sunlight and wood, when you look at the electricity power balance from the records of the last three years, it isn’t really possible to say that we generate more electricity than we use. And if the electricity we use from the mains isn’t all from a carbon free source, then we’re not zero-carbon.

Could we become so? Ignoring, for the moment, the argument about taking our electricity from an all-renewable source supplier, such as Ecotricity, or from a nuclear source supplier such as EDF, then the answer is, almost certainly, no.  The PV panels, limited to 4kWp without special permission, simply don’t generate enough electricity over the course of a year to achieve this.

The figures show that although we generate more electricity in a year than we draw from the mains supply, it isn’t possible to show that we generate more than we use.  So we’re not self sufficient in electricity.  We’d probably need a PV system twice the size to achieve this.

With the present PV system, to achieve a balance, I think we’d need to use less than 4,000kWh/a. And as the Klargester package sewage system uses about 1kWh a day, as does the MVHR, that’s over 700kWh/a used already.  It wouldn’t be comfortable – not enough cooking- too many cold meals!






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Now 2016 and just over 3 years

Yes, over 3 years now and still going strong.  Now starting to burn some of the -relatively little – left-overs from building the house which I cut down to size and stacked last spring. The off-cuts from the cladding – rebated Thermowood weatherboard – is particularly good kindling, so it’s just as well that the DWD – the external airtight cladding – does not support flame.

Well, we haven’t had the rain that the northwest – and now the north-east – has been getting but it has been very grey. And, even if mild, this means having to light the log burner to give us hot water.  Not necessarily every day because, when it’s mild, the house loses even less heat than it would normally do at this time of year.  But no sun, no hot water.


So here is the graph so far.  The wood so far has been very good quality (only just started using the lumber mentioned above) so not many barrow loads and relatively short-lived fires – just to generate a little heat and the hot water.  It’s a funny old winter so far.  Anybody still not believing climate change?

Posted in Cladding, Log burner, Solar thermal | 2 Comments

Will we make it to . .

. . the end of August?

It’s been pretty grey these last few days and today, 31st August, the forecast is for rain all day.  We had a fair bit of sunshine the day before yesterday and the thermal store temperatures got up to 70 at the top and not too bad below, so we have had hot water for yesterday and today – but will there be enough for a decent shower tomorrow morning?  We’ve got our younger son staying and so there’s more hot water needed!

Which prompted me to extract the data from the diaries for the last six months of last year and the first six months of this. So here’s the graph showing the number of times we lit the log burner and the number of barrows of wood we brought into the house.

Logburnerusage 2014-15

If you look back to “Another article – and wood usage update” (published in June 2014) which gives a rather different graph – the weather was clearly not the same, though, interestingly, both have a sort of gap in March – a spell of sunny weather which means that you don’t have to light the burner.  Then April needs more heat.  Ah yes – Flanders and Swann (for those of a certain age) April brings the sweet Spring showers/on and on for hours and hours.  Which explains it all, of course!

In 2013-14 we used 35 barrow-loads of wood and lit the fire 96 times – vs. the figures above of 33 and 89.  Of course if we go away for  a few days . . .

But the point I’m hoping to make is that we only lit the fire 96 or 89 times.  Out of the 365 days of the year.  All the other days – three quarters of the year – we didn’t need to. All the heat came from the sun.  Even if we were using gas – even oil(!) we would not be using much and not often.  And that’s the point of building to Passivhaus standards.

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Update for Summer 2015 – and the PV story

A few words to report what has been happening since the beginning of this year.  I suspect that visitors to the site are now as few and as intermittent as my posts on to it.  But the house is built and we’re living in it, so the excitement when everything was new and slightly experimental has, er, abated.

We finally got the Solar PV more or less sorted.  As described earlier, there are two “strings” of 9 panels side by side on the same roof.  So you would expect the output from each string as shown on the inverter display to be the same to within quite tight limits when the system is new – which they were – and to change only gradually as the panels age. It was noted that, within a year, the output from the east string was 10% below the west string.  This was reported to the contractor that installed the PV system.  The measurements were confirmed but nothing was done to rectify the matter.

By the following spring the east string had deteriorated to the point that it was 17% below the west string.  I pointed out that this was well outside the guaranteed performance – no more than 10% degradation after 10 years, no more than 20% degradation after 20 years. More measurements of the open-circuit voltages and short-circuit currents from each string were made and, after I pointed out that I would have to consider my legal position, there was even a visit from the panel manufacturers, Romag.  Romag had hoped that using a thermal camera would identify any suspicious temperature differences in the panels but this didn’t seem to work.  In the discussions it was put to me that the energy that the system had collected over the previous year was still significantly greater than the SAP performance.  I was unimpressed by this, pointing out that the SAP figure must be one which even the worst system in a year of really bad weather would be able to exceed, otherwise the industry would be receiving continuous complaints; they had to admit that this was the case.  In other words the SAP performance is a worst case figure!

But this was a red herring – the outputs were substantially different so the east string must be defective.

It was confirmed that the manufacturer will replace any defective panel(s) free of charge. Just that. Their warranty does not extend to the cost of removing and replacing the defective panels – this the installer has to bear.   It would be expected that a contractor in this business would hold insurance for just this eventuality – there are bound to be occasional problems as with any installation.  Some figures (inflated in my view) of the cost of scaffolding and getting the slates removed were mentioned together with a litany of the difficulties.  Time had passed and at the end of last summer the east string was now 19% down – I was asking if the string had fail completely before the installer would accept that it was defective and do something about it!  Eventually I was forced to go to another installer – essentially as an independent assessor – to confirm that the system was defective.  The original installer, after some trouble, finally obtained some replacement panels from Romag and delivered them here.  By this time it was winter and the weather was such that, on at least two of the agreed days when the independent contractor planned to change the panel(s), it was too windy to be safe.  Interestingly, on the morning that the scaffolding was put up, there was a frost which covered the whole roof with hoarfrost – except for one patch.  This picture was taken at 8.55 am on 9th December 2014.  There was light in the sky but no sunshine anywhere on the roof

Spot the hot spot!

Spot the hot spot!

Eventually coordinating some roofers and the independent contractor was achieved and the defective panel was replaced.  There was a period of panic when it was found that the first panel on the stack of replacement panels was found to be a slightly different size and wouldn’t fit.  Fortunately the next panel was the right size!

With the benefit of hindsight I should have insisted that all the panels were checked and had all those that were “down” replaced.  While I’m certain that the panel with the hot spot was the main culprit – there were some scorch marks and evidence of some delamination nevertheless the east string is still 9% below the west string.  After a further struggle, the original installer reimbursed me for the independent contractor’s invoice.

There’s further comment to all this: had I not had two strings – and so was able to compare the outputs – but only one, I would have had no idea that the performance had deteriorated.  The normal householder, like me, does not have a light meter and other equipment to check how well the panels that have been supplied are performing. Worth a thought!

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