Sun power for eco-farm

At  Mur Crusto farm, we have completed the final part of the eco jigsaw: we have a photovoltaic system installed and up and running. After a glitch with the wiring, the very professional MGS got our system operational last week. Below are some photos of the installation. Click on them for full sized views:

 Above are the two arrays of nine Schuco panels on the roof. They are supported by a heavily-galvanised robust steel rail system and connected electrically in series so as to generate anything up to 600 volts DC on a good sunny day. The output power is connected to a massive box, the inverter (see below).

 The inverter and its associated safety switches mounted on the board below it, is really the 'brains' of the system, transforming a variable DC input into AC at the voltage and frequency required to feed it into the National Grid or to power appliances in the house. The small white box on the upper right of the board below the inverter records exactly how many kilowatt-hours of power are generated. Our electricity supply company Ecotricity needs to know the total in order to pay us for the power we have generated. With the new feed-in tariffs, this amounts to 41.3 pence per kilowatt-hour. The power is pumped into the Grid via an armoured underground cable which connects to the meter box of Gwyndy, our holiday cottage, which will now be rendered carbon-negative and so can be truly claimed (as we do!) to be an eco-cottage.

Above is one of the simple but rather clever displays on the inverter which tells us how much power is being generated. You can move backwards from Today to Yesterday to the Week or Month and see all the aggregated totals. These include the amount of money generated - always good to know! - and the number of kilograms of CO2 saved by this particular solar powered installation; the feel-good factor.

Are we now carbon-neutral? I don't know but we've

1. insulated everything we can in Gwyndy and Mur Crusto farmhouse
2. have one economical car
3. installed wood-burning stoves for both buildings with all wood sourced from the farm
4. built a solar heat collecting conservatory
5. installed an energy-saving air source heat pump
6. installed the PV system I've described in this post

I think that's about all we can do...


System details

• maximum power the system can generate under ideal conditions - 3.78kWpeak 
• expected generation per year - 2900kW
• saving in CO2 over 1 year - 1.6 tonnes
• system is based on 18  Schuco MPE 215 PS 05 polycrystalline, photovoltaic panels
  mounted on the south facing roof of the barn
• the solar panels are covered by a 25 year manufacturer’s performance guarantee
• total cost - 16,550 GB pounds
• return on invested capital - 8.7 percent in first year rising incrementally to 15 percent in 25 years. Unlike the stock market, this investment payback is guaranteed and in any case generates far more than money held in a bank savings account
• payback time about 10 years
• annual income from sale of power generated - about 1,500 GB pounds

Heat pump: it's all go

Our heat pump is installed, commissioned and running beautifully. Goodbye oil. Hello clean, non-polluting, efficient heat energy. Yes I know most electric power is generated by highly polluting coal power stations but we source our power from a 'green' electric supplier and, later this summer, we'll be starting the process of finding and installing a photovoltaic solar generating system to more than cover the power demands imposed by the air source heat pump.

The installation of all the new radiators and pipework, replacing an ancient and incomplete system, went as smoothly as it could do. The 'dynamic duo' of Paul Southworth and his partner Clare (Paul is a plumber and electrical engineer) made the whole installation as painless for us as it could be given the scale of the job. And Paul's neat pipework and wiring in of the new highly insulated 210 litre hot water tank is a work of art (see photo).

There was one problem after the initial commissioning: the system ran fine but wouldn't turn off. But Ice Energy were quick to send an excellent engineer who quickly realised the problem - a simple wiring error not picked up in the first commissioning - and had the system running perfectly within 15 minutes.


So we are the happy owners of an entirely new concept in home heating which has the added benefit of attracting payments from the Renewable Heat Incentive from April 2011. The pump is very quiet and  amply copes with all the demands put on it. For the first time in the ten years we've been here we can be properly warm in any room in the house. Coupled in with the passive solar heating we get from the conservatory we built 3 years ago, we now have a warm, energy-efficient house.

Warm at last!

Mission accomplished: The Mur Crusto passive solar gain project is largely complete and we’re reaping the benefits immediately. We should have done it years ago. There’s more to do, of course, but now if you want, you can see all the best pictures of the construction from beginning to end. Click here to take you to my photo album where you can choose either to see all the captioned pictures as a slideshow in sequence, or move around the album of thumbnails to click any you're interested to see full-size.

Wonderful to be warm! The most obvious immediate benefit is that the core of the house, previously like a cold store even in summer, is now permanently warm. The temperature outside last night dropped to 3 degrees Celsius but we were perfectly warm in our living room, needing no additional heating. Remarkably, even late in the evening, the conservatory still felt quite warm. So we really are reaping our passive solar gains.

Battle against the weather: This summer has been lousy. A lot of it was dry but cold, but there have been long periods of 'unsettled' weather; Met Office parlance for rain and wind. Whilst there was no glazing, the concreted floor (see photos) repeatedly flooded and had to be pumped out. I developed a sort of 'cut and run' strategy for working, keeping all my tools in a wheelbarrow and coming out when the rain stopped. I'd work until the next rain and then trundle everything away into shelter. This is no way to work but I had no choice. Latterly, we did have a few weeks of dry weather which was perfectly timed for me to get on with glazing the roof and then the windows. Glazing the roof was what one might term 'a non-trivial operation'. (It said in the assembly instructions something like, "Now glaze the roof"!) Doing the lead flashings before that was also quite difficult, lead being heavy and difficult to fit in the continuous slot I'd cut in the wall of the house. But the roof glazing took the biscuit for difficulty: the glass units are heavy and locating them tricky. The seals for waterproofing are fiddly and messy (silicone all over the place). But I managed in about 2 weeks of struggling.

Last minute: The last pieces of glazing went in the east gable end a matter of 2 hours before the rain started again, just in time to stop the loss of warm air from inside the structure. From that time on, it's been a different world inside. Lots of light, warm space and the wonderful feeling of warmth flowing into the old, formerly cold, stone building -- all for free and without burning any fuel. There are a few small leaks which I have to sort out when the rain stops but otherwise, it's really great. Everyone should do this if they can. It really makes a difference!

The next stage: To gain the full advantage of this structure, I have to complete various things. One is the floor which I shall insulate. Another is the internal wall plastering and painting with a tinted paint ('sandstone' is the name of the tint). White houses are a serious mistake; very pretty but cold. It's just like the (vanishing) Arctic sea ice. Being white, both reflect almost all heat away. A dark wall or ice-free sea surface absorb most of the solar radiation and so heat up: good for warm housing; bad for warming oceans and accelerating ice melt. It's the albedo effect and it applies to houses just as it does to the Arctic Ocean. Ideally, I'd paint the internal wall black to absorb as much heat as possible and act as a massive heat store. But one has to compromise. A black house is not acceptable! So it's going to be that sandstone tint. Even so mild a colour makes a difference too. On a sunny day, place your hand on the white paint and it's cold. Place it on the sandstone paint and it's nice and warm.

Controlling the warmth: I also need to investigate simple control systems to duct heat actively into the house, using a fan, but only whilst there is heat to duct. In other words, I need to devise a simple system which switches on whilst it's hot in the conservatory and off when it's not. It would ideally recirculate the cooler air from the house into the conservatory for re-heating. What I don't want to do is dump heat into the atmosphere if it's needed in the house. If you, reader, have any ideas about how best to do this, please leave a comment below this post. I'm sure there are systems available so I don't have to re-invent the wheel.

Details of the building: For those interested, the U-value of the low-e double glazed units is 1.3 (Planitherm). The conservatory was manufactured by Portland Direct, the DIY branch of Amdega, all made from treated and painted softwood from (they claim) sustainably managed Scandinavian forests. This large structure cost around £10,000 delivered, with telephone back-up support available and very good. It's guaranteed for 15 years. The other bits and pieces (like blocks, cement, lead and so on) have probably cost another £1500 or so.

Then there's the small matter of my labour. I started excavations in January and completed the glazing in mid-September. I have probably spent one third of my available time working on this during that period, saving 4 weeks away in Scotland. Val has helped when needed, particularly with laying concrete and holding things in position and I have employed Simon, a carpenter friend and one of our organic veg customers, for 4 days in total. That's about it. Hard work, definitely a 'non-trivial operation' but rewarding. Most reasonably fit (I'm aged 60) and reasonably competent people could do similar. Building is, in part, a question of thinking things through slowly and carefully before doing them and using ingenuity where possible to save time and trouble. So... go for it!

Going down; going up!

Passive solar project continues...

Going down: At last, the digging out and barrowing on tons of boulders, stones and earth are over. The deepest part of all was the foundation for the 'dwarf' wall which will support the conservatory structure. Here (right), Val is checking the base level of the foundation trench with the water level (see previous post). Fortunately, because the ground is so hard and stony - thanks to glaciers 14,000 years ago - foundations can be minimal.


Going up: From this point on, it's up! First the foundations, then the base part of the dwarf wall which I've arranged so that the top of the blocks is exactly the same height as the finished floor level inside the structure. At least I hope I have. Val and I have treble checked levels, measurements and angles, all of which are made more complex by the front wall of the old farmhouse (to which the conservatory will attach) along which nothing is true; neither vertical nor plane.



Attention to insulation: The picture (above left) shows me, on a hot day wearing my sombrero, setting out the first double line of blocks. I'm using a sheet of Ecotherm insulation to ensure that the wall cavity is wide enough to hold these sheets when I build the rest of it. I intend to have 50mm of this high-quality insulation within the wall cavity and another 50mm attached to the inside and covered finally with plasterboard. I've found from my experience of building our holiday eco-cottage that insulation pays massive dividends. I shall also be insulating the floor. On the right (above), I'm pouring what seemed to be the thousandth barrowload of concrete - it's hard work! - to form the floor slab, 100mm thick. Underneath it is the black polythene damp proof membrane which we've lapped up the wall of the old house (which has neither foundations nor damp proof course) and over the first block of the dwarf wall. The damp course must always be above final outside ground level, of course.


Sub-floor complete! I finished pouring the final load of concrete just the day before it started to rain, the first rain for about 5 weeks. I'd worked 5 days previously, about 3-4 hours each day, making concrete, barrowing it and pouring it into 'cells' formed by pieces of timber. The top of each timber Val and I had carefully levelled (water level again) to ensure that the top of the levelled and tamped concrete would be about 100mm below the finished floor level. This leaves room for the underfloor insulation. As I write now, the concrete slab is flooded with water from all the lovely rain.


The next step: The conservatory frame arrives on a lorry in 3 days, complete with all the double glazed low-e glass ready to be installed when the frame is up. When the rain stops, I'll get on with building the rest of the dwarf wall at which point the excitement starts: will the frame fit? are my measurements correct? how long will it take? Already, the pressure's on... we've got our table and chairs on the new concrete floor (photo 3 behind) and look forward to having the finished structure which, we hope, will solve many of our old house's heating and insulation problems. We are, in short, fed up of living in a permanently frigid house. (It's frigid because there's no proper insulation and we refuse to run oil-fired heating except for an hour or so in the early morning.) The conservatory will help immensely because I intend to arrange for surplus heat to be ducted into the old house, effectively using the walls as a heat store. How effective this will be we can't be sure but it certainly will be better than the way things are now!

The Grand Conservatory Project: space heating from the sun

Completed clawdd (Welsh word meaning earth-cored) wall end in the garden and the start of the excavation

Construction - mostly destruction at this stage - is underway. I've been nipping out for a few hours most days when the gales and heavy rain stop to remove a rockery and completely rebuild a clawdd wall. This is to make space for The Conservatory which, we hope, will result in a much warmer house, partly because of its insulating properties on the solid stone wall of the exposed front of the house and partly because I intend to duct heat captured inside the conservatory into the usually-cold inside of this traditional farmhouse. I hope the walls will act as a heat store. That's the idea anyway. Any ideas for simple control devices and fans welcome! (Please add a Comment.)

Now that the rockery and wall are 'rearranged', there's a lot of heavy work ahead shifting barrowloads of soil and rocks. I've tried to arrange things so that I don't have to move stuff twice. So the biggest boulders - some of which I could only just manage to slide or roll - will form the basis of a new rockery in the middle of the garden, burying the existing ugly concrete path which with dozens of barrowloads of soil. So most of the excavated materials aren't 'waste'; they're useful in a new and more attractive context: a rockery in the middle of a single lawn no longer bisected by the ugly path to the gate which was never used anyway.

The indespensible water level, one end attached to the building, the other being free to check excavation depth

Now that I have the detailed drawings of this conservatory from its manufacturer, Val and I set up a datum level which is based on the distance between the base of the upstairs windowsill and the top of the conservatory 'wall plate': the highest timber of the frame which is bolted to the building. I have to leave space below the sill for flashing to go in or it will leak. That done, we checked with a water level that both sills were the same height (they weren't) and measured down to a point which is 1 metre above the finished floor level, marking this with a line. I then attached one end of water level to the wall. This means I can attach the other end of the level to a measuring post whose length below the level is at precisely the depth below the finished floor level that I need to excavate. That is 1.2 metres for the path which I will make along the front of the new structure, allowing for a dampproof course to be made at floor level in the dwarf wall which I will build to support the conservatory frame and glass. The glazing, by the way, will be low-e glass, double glazed, with a U value of about 1.3. Pretty good.

Excavating is the way it's going to be for a few more days if the long-awaited colder, drier weather persists. Then the fun starts! I have to break up the existing concrete 'patio' where the conservatory structure is to be built. This is a hodge-podge of patches of different concrete and different levels and so, unfortunately, has to go. Will I do the breaking by hand (sledge hammer) or hire a hydraulic breaker? I think the latter! But do watch this space...

Good news and bad news

First the good news: we got planning permission for the large conservatory that we wanted to build onto the front of the house. The intention was and is for passive solar heat capture. So now I'm starting the major excavations needed to prepare for the foundations and insulated floor. We're aiming for low U values throughout the structure so the floor and support wall will be well insulated. I try to do a couple of hours of levering and excavating of huge stones each day.

Now the bad news: Despite trying hard to get everything right so far as building regulations are concerned when constructing the eco-cottage, we've failed on several things in the final check. We are both quite angry and upset about this because we feel strongly that we just didn't get the support we needed, as self-builders, during construction. Let's hope matters are resolved satisfactorily when we meet up with the Building Control Manager in early January. Elsewhere in Europe, self build is common but in the UK, very few people have the courage and commitment to do it themselves. Part of the reason, I'm sure, is because 'the authorities' don't much like them and the system simply doesn't allow for non-professionals to receive kindly guidance so that they get the regulations bit right first time. In our case, you'd think that our cottage would be a shining beacon of effective renovation and proper construction for the low carbon build which we should all be aiming for. But nobody seems interested in our massive insulation and SAP rating of 107 (the maximum possible is 120). Shame!