Jeremy Harris

There's a battery solution that is viable, lasts for decades, is extremely well proven and need very little maintenance, so batteries definitely aren't the key issue. The real problem is that you will always have uncertainty in terms of generation capability, unless you just install a big generator. PV will be all but useless for a third of the year, wind generation will vary massively from day to day. Neither will give you a reliable minimum daily generation capability, so, as above, you need to adjust your life to match the unpredictable pattern of generation. Pretty much everyone who live off-grid ends up with a generator, unless they have something like a reliable hydroelectric system. A friend in the next village was on-grid and went off-grid voluntarily around 15 years or so ago. He bought an Indian-made single cylinder Lister diesel, coupled it to a generator and installed it in a concrete block built outhouse, complete with an underground 45 gallon oil drum silencer. He uses the waste heat from both the water jacket and a home made exhaust heat exchanger to heat water that runs his central heating and hot water system, whilst the generator runs the big electrical loads. He runs a 12V DC lighting system from batteries, but that's all the batteries run, so he doesn't have a big battery bank, and has avoided a fair bit of cost and maintenance as a consequence. He drives an old Perkins engined diesel Land Rover pickup and does a twice weekly trip collecting waste cooking oil from two Chinese restaurants and a chip shop. He processes some of the waste vegetable oil into biodiesel once a week or so, but the bulk of it is just filtered, pre-heated and used as-is to run the Lister. He's just adjusted his life style around not having power 24 hours a day, but only for the few hours a day when he runs the generator. He does spend around 10 to 15 hours a week collecting and processing fuel, servicing the generator, etc, so it's very far from being a fit and forget system. Then again, all off-grid systems require a few hours a week to maintain and keep optimised, as there's no solution available that is maintenance free, and there isn't likely to be one for a couple of decades, at a guess.

Around 35 years ago, some bright spark decided that anyone involved in defence research at the sharp end should have a month attached to a front line unit, complete with a temporary commission into your equivalent service rank. This was not popular with front line units, who really didn't want to have to baby sit someone useless (from their perspective). I was attached to 826 Naval Air Squadron, RNAS Culdrose, as a newbie Sub Lieutenant, supposedly straight from Dartmouth. On my first day, I pitched up to the morning brief and there was an announcement that four junior officers were booked for Aircrew Escape, Survival, and Evasion training starting that day, and transport was awaiting to take us to Lympstone Barracks, where instructors from 42 Commando were to give us three days training followed by a two day escape and evasion exercise, where we were dropped in pairs, with nothing but an aircrew coverall, basic kit that would be in the pockets of your survival life jacket, plus a live rabbit, with orders not to kill it in the first 24 hours. We were blindfolded, dropped somewhere on Dartmoor, and told we had a four hour start on the "enemy" (members of 42 Commando) who were trying to catch us before we reached a declared safe objective. If we got caught before the 48 hours were up we were taken back to Lympstone. It was pouring with rain, our bivvy leaked, the bloody rabbits crapped everywhere, we were both soaked to the skin and actually relieved when we were captured at around 4 am, some 15 hours after being dropped off. The relief did not last long. We were chucked face down in the back of a 4 tonner, wrists and ankles cable tied. When we got to the barracks, we were put in individual white-tiled cells, with bright lights and very loud music, on constantly. We were made to strip and stand on the tips of our toes, with our fingertips on the wall, and hosed down with cold water. We were constantly questioned, and for the first few hours managed to just stick to name, rank and number. After around 10 to 12 hours or so of this, the four of us that had been captured were marched into a room, still naked, and ordered to attention. A WRAC officer walked in, swagger stick under her arm, peak of her cap pulled down over her eyes. She walked along in front of us, quietly giving us abuse. She got to me and poked my "meat and two veg" with the end of her stick, saying "call yourself a man with equipment like that?". At this point I lost it, yelling that I was a civvy, that I wasn't in the bloody RN and they could let me go right now. One of the blokes handed the WRAC officer a bit of paper. She shoved it under my nose, pointing out that I'd signed up, and that I was under military law, as Sub Lieutenant J S Harris RN, whether I liked it or not.......................

To disguise our borehole, which is a raised concrete section 600 x 450 inspection chamber, we've built a circular stone wall around it, about 1500mm in diameter (about the smallest diameter we could manage). This is built on a hefty concrete footing, that seals to the pre-cast concrete inspection chamber section. I've added another inspection chamber section, so the borehole casing, inside the stone ring is now about 30mm above it and I have capped it with a 900 x 600 sandstone. The stone ring is around 400mm high, and we're now left with an annular space around the borehole head chamber and are thinking of turning it into a water feature. There's no risk of contaminating the borehole, as the borehole itself has a sealed cap, plus there's a 100mm drain leading from the base of the head chamber to a soakaway. All the electrics in the head chamber are IP66 sealed. What I'm looking at is the best way to seal both the outside of the precast chamber sections, the concrete base and the inside face of the stone wall. My initial thoughts are to parge coat the inside of the masonry to get it smooth and fill any bigger voids in the mortar, add a strong mortar radius around the base of both the inner face of the outer wall and the base, and between the outer face of the chamber section and the base. Once I have the surfaces fairly smooth, I was then thinking of using something like G4 PU sealant to seal the whole of the inside. I'll build in an overflow pipe and also a fill pipe, and as there's power there we may well add a pump and some form of gentle water feature later. The "pond" will be planted, with raised platforms for things like water lilies, maybe some irises, but won't have fish in it. Does the above sound sensible? I'll try and take a photo tomorrow, to show how it looks at the moment.

Sorry, no experience with the blinds, but we have a local chap coming out tomorrow to stick a couple of samples on the outside of the gable glazing to see how it looks. Talking to him on the phone he clearly knew his stuff and wasn't at all phased by the triple glazing, saying that they would do a full heat build up analysis as a part of the design process, needed for the warranty, from the film manufacturer. What I have sort of pinned down is that there aren't many manufacturers, but there are a lot of trade names, so some detective work is needed to find out which film any particular supplier is using. We will choose between two or three different films from the samples, as we're looking for both privacy and the ability to reflect a lot of heat away, but without the glazing looking like a mirror. The chap I've got coming out tomorrow is from these people: http://www.gpwindowfilms.com/solar-window-film.html and they also do solar blinds, so I can ask about them when he's here if you like.

That's what I did. The wire also allows more flexibility with layout, in that you can avoid areas like toilets etc more easily than with the mats.

Batteries are one problem, the lack of winter output from PV is another. Batteries are very expensive and need replacing every 8 to 10 years (if looked after) and the capacity of the battery bank needs to be around 4 to 5 times the daily usage, so you're going to use pretty much all of that £13k on the first set of batteries for the two houses. Then you need to look at another generation system for when the PV output is low (essentially around 4 months of the year). As above, £13k doesn't seem OTT for two houses. We paid £3.5k just to move a cable and pole, plus another £400 odd for the connection, just for one house.

100 W/m2 seems exceptionally high to me. I'd have thought that for comfort floor warming you'd be looking at no more than about 20 W/m2. I appreciate that the floor sensor will kick in and cut the power to the floor pretty quickly, but IIRC the electric UFH we have in our current house (with minimal insulation between it and the slab and tiles on top) is around 50 W/m2 and even that is throttled back by the controller and floor sensor pretty quickly. We've found that having the bathroom tiles at around 24 deg C is fine for just making them feel comfortable to walk on when you step out of the shower.

The TV may well have a voltage range marked on it. My (limited) experience is that "12V" TV sets, that have an external power supply to allow them to run from mains, will work over a pretty wide range and are often designed to be used in boats and caravans where the battery voltage can vary a fair bit (although quite why on earth anyone would ever want one in either is beyond me!). As above, definitely a better bet to connect it to the charge controller output, as even the cheap ones often have some forum of voltage limiting. I have a cheap Ebay one here that was falsely labelled as an "MPPT" charge controller, (as many are) and when it arrived I took it apart, as it seemed suspiciously lightweight for a real MPPT controller. Sure enough, all it had inside was a voltage regulator, but it does regulate on the output side as well as the battery side, albeit with the output side limited to the battery float charge voltage of 13.2 V. If you get stuck, there are some very good and efficient boost/buck regulators on Ebay that can supply a constant 12V from around 7V to 30V input, but I'm pretty sure you should be OK with a direct connection to the charge controller output.

Welcome, we were indeed wondering where you'd got to! Glad to see you have a project to get stuck in to, should be interesting.

The more complicated they can make it the more money they can charge and the greater the level of inconvenience they can cause. My experience of these people is that the have a mentality like some conservation officers, they start from a position that is totally and absolutely opposed to you doing anything, and they then try every way they can to make your life as damned difficult as possible, in the hope that you will give up and not do the work. One actually said as much to me a few years ago, saying that their basic premise was to oppose all forms of change or development because it inevitably had an adverse impact as far as they were concerned.

Oh, like the infamous Fanny Flambeaux doll, (which admittedly Big Clive made up as a spoof) :

We should have. Before the bloody EU made all this unbelievably complex regulations we had a perfectly good set of road traffic laws that ensured that vehicles on our roads were amongst the safest in the world (more than can be said for some EU states). Now we have such a minefield of beaurocracy that no one seems to be able to grasp all the implications, as as above there is a good chance that you could get pulled over evern if you're perfectly legal, just because no one, least of all the police, see to know what is legal and what isn't. I think a part of this is the massive cultural difference between law in the UK and law elsewhere in the EU. In the UK we have always adopted the principle that if something isn't specifically unlawful then it is, by definition, lawful. An example: When I was about 14 I and two friends bought an old stripped down BSA Bantam motorcycle, to ride around a local field (where we had permission from the farmer as long as we only rode around the edge). We were stopped by the police whilst pushing it along the lane to get to the field. The policeman pointed out that we weren't legally allowed to even push it on the road. He thought for a moment and then asked if we had any roller skates. One of us said yes and the policeman suggested we run back and get them, together with some cord, and lift the bike up on to them so we could push it along, rolling on the skates. Apparently we were then within the law (not sure a police officer would behave like this today, mind). Some other EU states have the opposite principle. Everything is potentially unlawful unless there is a specific law that makes it lawful. There's no way that these two, fundamentally different, approaches to lawmaking are ever going to be reconciled, and the UK will never get a useful say as we are one voice out of twenty eight.

Thanks Peter.

It's probably pot luck. There is very definitely far more dodgy stuff around than good stuff, and very few retailers have the ability to check whether the safety markings are fake or not. My experience is to assume that everything from China is fake and untested, unless you have strong evidence to the contrary. There are some reputable manufacturers out there, but they tend to be few and far apart, and even they may not be consistent. Around 10 to 12 years ago I was peripherally involved with a chap that was making custom bicycles. Most cycle parts in the world come from from China, or more specifically Taiwan, which is or is not China depending whether you're on the mainland or the island. Anyway, his bikes were fairly high-end and he wanted good quality components. He ended up flying out to meet some factory owners and discuss his requirement and particularly look at their quality procedures. He came back, having had a tough time finding a quality supplier and placed an order. The parts arrived and the first batch of bikes were made and were pretty good (I still have some parts from those on one of my bikes). After about a year he found that the quality of the parts had decreased markedly and he had words with his Taiwanese supplier. The supplier couldn't understand his problem, as he had dropped the price of the parts. It seems there is a culture of trying to cut the price of manufacture no matter what the consequences are to quality or safety. There's no easy way around this, and in the end my friend found an ex-pat Brit living out there who was working as a quality assurance advisor to several British companies. He was needed simply because there was no way you could stop the manufacturers from cutting corners to reduce the price, unless someone representing the customer stepped in and stopped them. It's an endemic problem, as big, or bigger, than faking approvals, and isn't looked upon as criminal, it's considered to be a sign of a good businessman if he can sell for the lowest possible price, and a source of personal pride.

If the TV with the separate power supply really runs on 12V DC from that power supply, then it's far better to run it direct from the battery. Using the inverter to boost 12V DC to 240 VAC will waste around 10 to 15% and then using the power supply unit that comes with the TV to convert 240 VAC back to 12 V DC will waste another 10 to 15%, so you could be wasting 20 to 30% of you battery energy by using the 240 V inverter. Before running the TV from 12 V, best check that the power supply does put out 12 V DC. Some seem to run on laptop supplies, and they are often around 18 to 19 V DC.

I used to write code for a range of microcontrollers in either machine code or assembly language, as they were the only real options at the time. Programming then was blowing code directly into UV erasable EPROMs, with no way of doing any debugging prior to test, other than a static code walk through, which is still what we do today for a lot of safety critical firmware created using the majority of compilers of uncertain parentage (and that's most of them, unfortunately). When I need something to execute very quickly I still tend to write it in assembly language, as it'll always be far more efficient, reliable and take up much less memory than writing it in something like C and compiling it (and I accept that C is worse than most languages for this task, as it just isn't efficient at generating microcontroller-type code). Over the past few years I've switched to "cheating" and using the Picaxe option. It's slow, because the interpreter is coded into the PIC when you buy it, but for 99% of hobby-type projects it is plenty fast enough. The massive advantage is that it's dead easy to programme the chips in-circuit, the chips are barely any more expensive than bare PICs, the programming environment is free and the programming port is a simple serial port. The whole Picaxe project was designed for education, so there is a bit of a bias towards education related features, but that doesn't stop more complex projects using them at all. The data loggers I have that measure stuff and record it to either SD card or uSD cards use them. The "energy bucket" excess PV diverter I built uses their smallest device, an 8 pin, 2048 byte programme memory chip that costs just £1.80 including VAT. The wireless treatment plant alarm uses a slightly bigger 14 pin version of the same chip, with the same programme memory but more I/O pins and costs £2.16 inc VAT. It really is dead easy to build reasonably complex projects around these chips, with the peripherals almost always costing more than the chips. As an example, here's the write up I did on the combined CO2, temperature, humidity and real time data logger I built a while ago, and which has been loaned out to a few members here: http://www.picaxeforum.co.uk/showthread.php?23893-Air-quality-monitor-and-logger The Picaxe system is very simple and works exceptionally well, but gets a lot of flack from the Arduino crowd, for a few reasons, the only valid one being that it's not open source, the small surcharge on the price of each cheap (just a few pence over the bare PIC price) pays for the interpreter pre-loaded to the chip. The big advantage, apart from the ease of use and ease of programming and programme development and debugging is that there is no SOUP (Software Of Unknown Provenance) in the code. As the Arduino has grown in popularity so has the spread of tens of thousands of libraries, very, very few of which are 100% reliable or even properly documented. The Picaxe may be slow, but the standard of documentation and the fact that it has no reliance on completely unknown provenance code libraries to work, makes it a winner for me. Add in that the chips are dirt cheap (a fraction of the cost of the Arduino), the programming environment is free and easier to use and understand than the Arduino IDE, (and includes properly indexed manuals), and for simple projects where control is the main objective and there's no need for floating point math you can get things up and running very quickly, and for me it's a no brainer as to what to use for this sort of project. On the other hand, when I was building a unit that needed to very quickly calculate position from the double integration of three accelerometers with axes determination from a three axes rate gyro, I used an Arduino, because there the over-riding need was for fast floating point math, not the control of peripherals. It's horses for courses, really. If all I want to do is measure some data and store it, display it or transmit it via a wireless link, then the Picaxe wins hands down, on price, speed of development and ease of use. If I want to perform fast floating point computation, the the Arduino wins hands down, as the significant additional cost is worth it to get the job done. If you want to have a play without breaking the bank, then I suggest getting a starter pack like this: http://www.picaxestore.com/index.php/en_gb/picaxe/picaxe-starter-packs/axe004u.html and some LEDs, switches etc to have a play around. You can use the board to programme either the 14 pin Picaxe or the 8 pin one (just shove the 8 pin one towards one end of the socket). I tend to build a simple onboard programming connector into any project board where it might be useful (for example, the outdoor end of the treatment plant alarm has no programming connector, as the code is brain-dead simple and wont need to be changed, the indoor end has a three pin programming connector because I envisaged the need to change display messages, alarm thresholds etc).

OK, your name's on the last one! I'll post all the details, schematic, PCB layout, parts list, firmware etc as open source, for anyone to use, anyway, as it'd be nice to see someone come up with something like this as a product, as I'm convinced there's a need for remote monitoring of treatment plant aeration systems. The existing alarms are either intended for Koi carp aeration systems or are almost one-off type systems like the one that came with our BioPure. Technically I can't supply a totally finished unit, as it wouldn't have the required EU approvals (and getting it approved to the EMC Directive and LV Directive would cost thousands). The way around this is for me to supply units partially dissembled. What I'll do is leave the fitting of the parts into the cases as a DIY job, with no soldering etc needed, and then it can legitimately be called a kit, and so get around the requirement for approval.

For around 7 years I kept an old Diahatsu FourTrak just for towing (then it was my big aeroplane trailer much of the time). I paid £1000 for it and only ever had to do one repair, a new set of seals and pistons for the front brakes, about £30 IIRC. Even when I got rid of it the tyres it came with still had masses of tread left. It never failed to start, even when left for months on end and I rarely did more than 1000 miles a year in it, with the exception of one year when I towed the aeroplane down to the Loire for a couple of weeks flying and a holiday there, where I needed more luggage (and wine-carrying capacity for the return trip) than would fit in the aeroplane. It never once let me down and was a surprisingly good 4 x 4, with no sign of any rust on it at all when I eventually got rid of it, when it was 19 years old. I regret having got rid of it, especially over the past three years where it would have been very useful for the new build, but I was buying a new Prius in 2010 (before we'd even seen our plot of land), had stopped flying so didn't need a big tow car and the government were offering £2000 scrappage. So, after 7 years use I "sold" it for a profit about £970..................... I've been seriously tempted to get an older tax-exempt car as a general runabout. A bizarre idea I've had for a few years now is to buy a basket case Austin 7 or similar ("sit up and beg" style, like the Ruby) and convert it to an electric car as a local runabout and shopping car, keeping the decent car for longer journeys. I stripped and rebuilt (from the chassis up) a 1937 Morris 8 open tourer years ago, and cars of that era are a delight to work on mechanically, as it's easy enough to fabricate just about any non-engine or gearbox part you need. Hence the idea to get something similarly small and easy to work on and just fit a decent electric drive train, which would make such a car far more driveable and virtually do away with most of the servicing (except the couple of dozen chassis grease points!).

I dare say I can add an extra one Jason, not really an issue as I'll now have bits for 5 units, rather than 4.

They are all identical, float alarm or no float alarm even down to the code being the same, the only cost difference would be that I could leave out the terminal block for the alarm connections and save a bit under 10p. If you don't need the float then just don't fit a float switch and the unit will just assume there's no float alarm. If you need any other sort of alarm, then you can wire any normally open switch to the float terminals if you want, and when the switch closes it will sound the alarm inside the house. If you want to do this, then let me know and I can change the code to display a message other than "HI LEVEL" on the alarm unit display. You could wire this to pretty much anything, like an anti-tamper switch, a switch on the door of a chicken shed to remind you that the hens are abed (did one of these for a friend years ago, so she could check to see whether she'd remembered to shut them in at night without needing to go outside with a torch to double check). Anything you can run a bit of two core cable to with a normally open switch could be used to trigger it.

The bigger backlit version is my preference, too, as I think it will be easier to read where I'm going to put it (on the utility room wall, where the thermostat receivers, ASHP command unit etc are located) and I like the idea of hard-wiring it to the supply, just for neatness. Price is an odd thing for things like this, as when you're knocking stuff together you sort of get used to things being much cheaper than an equivalent commercial device, even if you can buy a commercial device that will do the job. I think I added up the cost of the excess PV power diverter I made and it came to around £25, that's for a unit where the power sensing is done outside, at the incomer, with a radio link to both the power switch for the Sunamp PV and to a plug-in power display that receives the data and has a display showing whether the house in importing or exporting, and what the instantaneous power is. I tend to think that spending more than £30 on any little gadget like this is getting to be too much!

That's very good news indeed, it's nice to know that there are some genuinely approved and marked power supplies out there. At a guess, I'd say well over half the LED supplies sold as being compliant with EU safety and EMC regs have fake markings, may be as high as 75% or more. It's annoying, as no one seems to care enough to do anything about all this electrical junk. The best we seem to be able to do is rely on people like bigclive.com to highlight all the lethal or just a bit dodgy stuff that seems to be flooding the market. A couple of years ago I even caught dodgy and non-compliant junk LEDs being sold in one of the big DIY sheds. To their credit they did take them off the shelves, but said that they had no way of knowing whether certification marks were genuine or forged, and had to rely on their supply chain, which is just a bit worrying.

I've found some small wall-mount boxes that come with a display cut-out for a good price, so have ordered a few to see what they are like (they aren't expensive). I'm hoping that I can fit a small power supply inside (the same as the small 1 W, 5 V supply in the outside unit, the orange block at the lower left in the photo). If so, then it increases the price by a couple of pounds, but makes for a neater arrangement, as I can fit a fuse to the unit and then it could be either hard wired to the house supply or run from a 13 A plug. One thing about the case I've found is that it takes a bigger (but cheaper) display, so I can display more information, rather than just the pressure. It means I could display the high level text warning and still display the air pump pressure, for example. It also means I can backlight the display, as the existing display wasn't available with a backlight, and I think it would be useful to have a not-too-bright backlight to make the display more readable. If anyone has any preferences one way or the other, then let me know, as I have parts (except the cases that are on order) to make either version. The air pressure sense pipe on the outdoor unit will be a 4mm diameter barbed fitting, threaded into the lower part of the case, next to the power cable and the cable inlet for the float switch (if needed). Hopefully this will be OK for whatever pressure sense pipe you may already have, but if not I can get hold of tee fittings from the aquatics place over the road, they seem to do one with a 19mm (3/4") straight through and a 4mm side fitting, that looks very like the fitting that is already on our air pump. I've done a quick estimate of the parts cost and it's a little more than I'd hoped, at around £36. I had hoped to be able to make them for under £30, but the cost of all the little bits seems to add up. Please say if this is a bit too pricey!

I can't see that it will make any difference at all, apart from, perhaps, the way the control systems work/interact. Whether you need the control systems to work together depends very much on the layout, for example do you need both units to boost at the same time in response to a boost switch/button/sensor? Also, if you can have a common control for both in terms of setting fan speeds, summer bypass etc it can be useful, as it would save having two have duplicate controls, but again, some of the simpler units use much the same control interface so it should be possible to get two of any make to work OK together. In terms of commissioning it makes no difference at all. even with two of the same type you'd still have to cope with the pressure interactions that make it a bit of an iterative process.

Towing seems to be the sticking point, as so many low emission vehicles are made now with no Type Approval to allow the fitting of a tow bar. This is an EU thing, as the same vehicles are available in the USA with a tow bar option. I tow a small boat trailer from time to time, and have had to resort to importing a US made "receiver hitch" and taking the tow ball off when I'm not towing. It's dodgy, as my car insurance reverts to 3rd party only whilst I'm using the trailer, but the insurers are fine with just the "receiver hitch" fitted (and declared) as it can also act as a bike rack mount. I know people in the US that have towed pretty hefty loads with a Prius, and never had a problem. They've been doing this for years, too (and so have I, I bought my first Prius in 2005). Toyota themselves have no problem technically with fitting a hitch, in fact they provide all the load details needed for the built-in hitch attachments on the frame, but for whatever reason they won't declare a hitch as being allowable under EU Type Approval. The odd thing is that the police don't have a problem with the receiver hitch fitted to my car. I had one written off with the receiver fitted (and a bike rack fitted to it) and the police did check the hitch approval sticker and declared that they were happy with the US DOT certification. It's a nuisance, as there are a lot of potentially viable low emission (and hence low tax) towing vehicles around that just can't legally be used for the purpose.