Nearly there!

Since I last posted, I've made more progress on the solar panel project (which is just as well, as I'm not doing anything else!) One job that I had thought might be beyond me was fitting a new electric socket into the cupboard where the pump is. I've never tackled mains electricity before, and didn't really know where to start. However, browsing through the Readers Digest DIY manual (as you do), I found nice clear instructions for taking a spur from one socket to supply another. That's exactly what I needed - I could use the socket across the hall that we'd been plugging the extension lead into. Far better to have the wire running under the floor than over it. All I had to do was lift the floor...

In one way, that wasn't too bad as I'd laid that bit of floor myself, so knew where I was with it. On the other hand, the pipes set into the floor had been connected up since then. At least they were flexible plastic, so should cope with having the board gently eased up. I did just that and, after a slight setback when I discovered that the wires to the socket went up, not down (so no hole in the floor beneath them), the job went entirely to plan, and I now have a new double socket in the cupboard. I also tidied up the wiring in there and added a switch for the pump. First I had to find a switch, which came to light when I took the coats off the coat rack before soldering just above them. There was a thermostat on the wall, no longer in use (obviously). That must have a switch in it! I thought. I took it to pieces and discovered not only a switch that's normally on, push button for off, but also a wiring diagram. Perfect. This enables the pump to be switched off with the solenoid valve left open, which is necessary for draining the system. In addition to a switch, the pump now has a connected earth wire. Yes, I know.

Believe it or not, this is the after tidying photo.

I've connected up all the plumbing. This included a few solder joints, most of which were done twice, though in my defense, I was dodging hail showers at the time, and re-doing the leaky connector over the coat rack that I hadn't quite fixed last time I tried. I'd expected the compression joints to be relatively easy, but even they threw up a few challenges. One pipe running down the side of a radiator wouldn't go past the plug I'd put in the other corner, but luckily I had a flatter one in a different corner, so could swap them around. In spite of writing Make sure 1st and 2nd boxes are close enough together for flexi-hose on my list, they weren't, but I solved that by bending the solid pipe instead of cutting it to only just longer than the box. When I went to raid the old radiators for bleed valves, I found that most of them had the grub screws missing. I don't know how that happened - I don't remember taking them out. I used a cap in place of one bleed valve - it works almost as well. Finally, I nearly destroyed two nuts trying to tighten a joint that I'd failed to put an olive in. Luckily, I checked.

Having made all the connections, I needed to fill the system to check for leaks. That meant going up into the loft, which meant a ladder that I discovered, on first climbing it, wasn't very firm on the floor. That is, the floor is dusty and the ladder slipped. I caught it before it went too far, but came down quickly and resolved not to go up again without someone to hold the bottom. Ian being out at work, I called on a neighbour, who kindly came round and held the ladder for me, and was quite interested to see the rest of the system too. Much to my surprise, not to say delight, there were no leaks. Not one.

The next step was to replace the plain water in the system with an antifreeze* mix. I'd originally thought of mixing it up in a watering can then pouring it into the header tank in the loft. Unfortunately there wasn't enough headroom above the tank for that plan to work. When Ian got home from work I asked for his input on the problem. He thought a bit then said, I do have that 12 volt pump and hose that I used to use for biodiesel. Maybe we could pump it up there. I have a spare battery, too. While he went off to fetch those things, I continued to search for inspiration on the internet. Surely other people have solved this problem? Well yes, but most of them solved it at the design stage, incorporating charging valves into the system for this very purpose. Then I came across the following very useful advice:

you could try this "cheapskate" approach:

Make no connection whatsoever to the water main. Use a 5L house-plant sprayer (Hozelock). Remove spray head, fill container with antifreeze water mix, attach hose to system drain and pump. The pump will easily deliver up to 3 bar.

I wasn't sure whether our pump could deliver that kind of pressure, but filling through the drain would be a lot easier than getting the pump within reach of the header tank. It had to be worth a go.

Pump in a bucket of bright pink antifreeze, powered by car battery and battery booster

It worked, just about. We ran the system pump to help it, and there was lots of running out to open bleed valves, then close them again in case the antifreeze all escaped as well as opening and closing the drain to take liquid in, then not let it out again. This required a lot of coordination between the two of us. The pump didn't quite manage the last litre and a half, so Ian took that up to the loft in a jug, and I think we may need to top up with a bit more water, as there are distinct gurgling sounds when the pump's running. However, we now have all the panels connected up and full of antifreeze, ready to go. The controller is doing its thing, and reporting slightly more information than it was last time I wrote about it.

Controller display, now fixed to the shelf

In addition to sensors in the panel and in the tank, I now have one on the pipe just before it goes into the tank. Ideally, this should be at about the same temperature as the panel when the pump's running, but as you can see, it's considerably lower. That means we've lost almost 20°C between the panel and the tank. Not good. Insulation is needed.

I started insulating the pipes around the panels, but I need to improve on this. I'll do more when the weather's better.

More shiny wrapping will be added

For the next stage of their journey the pipes cross the conservatory. I had an idea that since they're running under a transparent roof, maybe they could absorb some more sunlight on the way. It's probably a daft idea, but I persevered. Using an offcut of the roof itself, I made thee sides of a box.

Bent polycarbonate roofing

It is possible to bend polycarbonate cold, but only if you can take it a lot further than the angle you need, to allow for spring back. I couldn't do that, so had to apply heat. This meant waving a blowtorch at a piece of plastic I was holding in my hand. I managed not to burn myself, which is quite remarkable considering how often I burn myself on the oven. The other day I even managed to burn my finger on one of the solar panels. Yes, it did get that hot!

To go inside the box, I taped up some of the thin insulation for behind radiators and pleated a few layers between the pipes, and some more around them. Just the top was left open to the sunshine. When I say open, I mean covered by twin-wall polycarbonate roofing.

Boxed-in pipes

I'm not entirely convinced by this, but it has to be better than it was. If nothing else, it's a lot tidier.

Items remaining on my list are: Insulate pipes and touch up paint on window frames, both of which are waiting for better weather, screw down window on first box, which I'll do when I'm quite sure the system doesn't need bleeding any more, fix blinds to boxes, which can wait, as it's only needed if we go away in the summer, and possibly not even then, figure out clock for controller and program data logging, the first of which I spent quite a lot of time on today, and one I added yesterday, calibrate sensors. When I checked first thing, the display reported that the panel was at -2°C but there was no sign of frost, so it's evidently not accurate. I had meant to do this before I taped the sensor to the back of a solar panel, but I forgot.

As for figuring out a clock, this is so I can record temperatures and keep track of when they occur. People usually use an external, battery powered clock for this, but it is possible to make the Aruduino keep track of time and date after taking a time signal from a PC to start it off. I spent a long time looking up how to do this (it's here, if you're interested), then this afternoon our electricity kept flicking on and off, reminding me why the external clock's a good idea. I guess I'll be getting one of those then. That means more soldering. Hmph.

So there we are, nearly finished. The only remaining job that's going to make a difference to the effectiveness of the panels is adding insulation, and I'm well on the way with that. All I need now is some sunshine.

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* I spent far too long considering what kind of antifreeze to use. Our system has the unusual feature of two walls of copper between the solar loop and the drinking water. This means I'm not constrained to use non-toxic antifreeze (if you have only one wall of copper separating them, you should use propylene glycol, which is food safe, in case there's a leak. Otherwise you might end up poisoning your drinking water), so could consider other alternatives. Methanol has a low freezing point, low viscosity, and an even higher specific heat capacity than water. It would be absolutely ideal if it weren't for - and I found this fact very frustrating - its tendency to evaporate, filling the space with poisonous, explosive gas. I settled for car antifreeze in the end, which is pretty much where I started from.

The third panel

I'm still working on the solar panels. They're not finished yet, but I'm making progress. This post is a bit about the design of the system.

As soon as you add a second panel to the system, there's a decision to be made about whether to connect them up in series (water goes through each panel in turn) or in parallel (there's a junction to split the water so it goes through both/all at once, then another junction to bring it back together again). Guidelines that I consulted on how to connect up solar panels tended to describe a combination layout, e.g. four panels arranged in two parallel runs, without discussing the pros and cons of each option. I had to do some general reading, and some thinking for myself, and here's what I came up with.

Panels in series make a longer loop for the water to go round, which means a more powerful pump is required. Panels in parallel require balancing to make sure one of the panels doesn't end up dominating the system, which the water essentially bypassing the others. I think that plumbers tend to favour parallel systems for these reasons, as balancing systems is something they do all the time, so it's no big deal to them. As for the effectiveness of catching heat from the sun, given a certain amount of sunlight falling on a given surface area, it might seem that there's no way that varying the plumbing could affect how much heat is captured, but there are a few factors that are worth considering.

Specific to my system is the fact that radiators have a high volume of water relative to commercial flat panel solar collectors. This means that they aren't so responsive; they take longer to heat up, so if there's only a short period of sunshine, they may not get hot enough to trigger the pump and take the heat into the thermal store. Hot enough is an important point here: If my store is at 50°C already, the incoming water needs to be pretty hot before it's any use. This means I want to maximize temperature, if possible.

On the other hand, there's the question of panel efficiency. For all the insulation I've put in, they will radiate heat back into the air, especially through the glass. If heat can be taken away from the panel when it's only a little above air temperature, then very little heat will be lost to the air, so the panel will be operating at a higher efficiency than it would if it was a getting a lot hotter before the heat was taken away and stored. Now we have arguments in favour of both high and low temperatures.

Let's look at how serial and parallel systems vary in terms of temperature. In a parallel system, water in all of the panels heats up at the same time, starting cool then, if it gets hot enough, all being pumped into the store at once. In a serial system, water goes through each panel in turn, so the first panel might be considered a preheat panel, and the last a topping up panel. This means there are different temperatures at different points in the system, which could be a good thing, considering the conflicting requirements mentioned above. The first panel can operate at a lower temperature, and so be more efficient, and the second panel brings the water up to a temperature high enough to be useful, i.e. hotter than the water already in the store.

However, there is a slight weakness in the description I just gave you. Water goes through means that the water is already flowing round the system. This won't happen until the last panel gets hotter than the stored water which, radiators being slow to respond, could take quite some time first thing in the morning. This brings us to the third panel.

How about having a booster panel that will heat up quickly and get the water flowing round the system? There are many designs for DIY solar panels to be found on the internet, and most of them involve much smaller volumes of water than the radiator design. If I made a small one of these and added it after the bigger panels in the series, it would heat up more quickly when the sun hits the panels in the morning and so start the water circulating before the other panels had got up to temperature. After that, it should serve to boost the temperature as the preheated water flows through it, so giving the higher temperatures needed to be worth adding to the store, at the same time as allowing the other panels to operate at cooler, more efficient temperatures. That's the theory, anyway.

I had plenty of microbore (10mm dia) copper pipe salvaged from the old central heating, and a sheet of aluminium that was originally behind a gas fire, and has more recently been part of my heated propagator. These could be used to make a solar collector along the same lines as this one described on builditsolar.com. I went for serpentine design to save making a lot of connections - I don't need a high volume of water here, so it doesn't matter if the pipes are widely spaced.

Having bent my pipe, I then used a 10mm steel bar - I have no idea where that came from - and hit it repeatedly into the aluminium sheet to make grooves. If you're thinking of trying this, it really is worth making a jig to shape the grooves. I started by setting the workbench to the appropriate width, but it kept opening out, which absorbed much of the energy I was putting in with the hammer.

The grooves in this aluminium sheet are carefully aligned to the bent pipe (visible in the background), not accidentally wonky

Once I had the two parts made, they needed connecting together. Following advice from builditsolar, I used silicone gloop to fill the gap between aluminium sheet and copper pipe. I then drilled some holes and tied the pipes into place with cable ties.

Each cable tie is looped twice over the pipe and joined at the back. I had hoped to pull the aluminium more tightly around the pipes, but the cable ties weren't strong enough.

All this got me as far as selecting a radiator for the other panels. I then selected a suitable sized window and made a box in the same way as I had for the other panels (I didn't tell you about the second panel. It was very much like the first one, except that the best fitting windows were wood framed house windows, which took a lot more work to prepare, being old and somewhat rotten). At some point before putting the insulation in, I realised that it would be a good idea to solder the connections that needed it before the pipes were snuggled up next to plastic insulating stuff. I'm glad I realised at that point.

Here is my finished booster panel, out on the hillside. The diagonal lines are reflections of overhead cables.

As you see, the window wasn't a very good fit for the collector, but it does allow space for a bleed valve to one side. The vertical pipe disappears under the top layer of insulation, to exit the box at the bottom.

And here it is in context:

Three solar panels, all fixed to their brick bases.

So, I now have all three panels in position. Once I've connected them together I'll be able to fill them and start catching sunlight. That isn't quite the end of the project, though. Insulation is quite important, too, and it would be nice if the power supply didn't run across the hallway to reach the pump.

One solar panel (box) now in position

When I checked my brick bases yesterday morning, they were had indeed set firm and were still horizontal and vertical in the correct places. This was pleasing, if not very surprising. At this stage, I was able to make the final measurement of how steep the bank is, or more precisely, the slope between the two bases. Getting a panel set up at the desired angle to the sun isn't straightforward when you're standing it on such an irregular surface. However, having given it much thought, I had a plan, and measuring the slope was the first step.

Tools for measuring orientation

As previously mentioned, the compass proved less useful than anticipated (and wasn't needed for this stage of the job, in any case), and it turns out that a paperclip makes a poor plumb bob, but the spirit level and protractor, held against a floorboard resting across the brick bases, were quite effective. Once I'd measured the angle of the bank, and I knew (from calculations) the desired angle towards the sky, I could prop up the solar panel box indoors at the right attitude.

Solar panel box propped up on bits of firewood

It's not the most stable of arrangements, perhaps, but it did the job. With this in position, I took the spirit level and drew horizontal lines around all the legs. This part was more difficult than I expected, but I ended up with this:

One solar panel leg marked out for cutting

Do you see where I'm going with this yet? If I cut the legs to horizontal, and have brick bases that are also horizontal, the two should fit together to give me the right angle of the panel. Added to this, I need a vertical hole in each leg for the peg. That is, it will be vertical when it's all in position, but at time of drilling, it has to be perpendicular to the cut surface of the leg. These holes also need to be exactly the right distance apart, so I measured the pegs again, for the umpteenth time. I used a gimlet to make pilot holes as it's much easier with a hand tool to give it half a turn or two then check again with a set square to make sure it's still going in the right direction.

Having drilled the holes, I couldn't resist taking the box up to the bank to see whether it fitted. Halfway up the steps I thought, I'm not going to want to do this again. Luckily, it fitted!

Solar panel box, standing on front bases only

Not only did it fit perfectly, but it stood up on its own, too. That was better than I expected but I thought I'd better stick to the plan and add the back legs. After all, it will be carrying a lot more weight when it's finished. Having got the box in position, the next step was to find the positions for the back legs, which I did with a plumb line made by tying a brass nut to a piece of string and hanging it under the legs. I then mortared bricks and pegs into position, again aiming for horizontal bricks and vertical pegs, though it was slightly less critical this time.

Once the mortar had set (I left it over night, with the panel propped up for extra support, though it didn't really need it), it was time to fill in the gaps. There were some bits of wood up there that I'd taken up some time ago when first thinking about how to support solar panels. I think they were from the leylandii hedge. In any case, they looked quite suitable for making back legs from. I measured these against the gaps between panel feet and brick bases, cut them to length, drilled holes, somehow eased them into the gap, and finally added brackets to connect them up at the top.

First panel box fixed in position

After that, I applied copious quantities of creosote then brought the glass cover out to go on top, which I finished just as the first few drops of rain fell. Now I can turn my attention to the second panel.

Solar panel update

Since finishing the new terrace, the solar panel project has been top of my list of priorities. I've already had one panel connected up and working, complete with pipework, pump and automatic controller, and since then I've more-or-less made a second panel, and made a start on the third, so it felt like I was fairly near the end of the job. I hoped to get it finished by the end of February.

Unsurprisingly, that didn't happen. Feeling somewhat despondent, I sat down and wrote a list of all the tasks that needed doing before I could say the job was finished. The list ended up looking like this:

There seem to be quite a lot of jobs still to do. I managed to cross a few off by the time I took this photo.

That didn't improve my state of mind greatly; it was considerably daunting. Still, at least it was now obvious why I hadn't finished it all in the expected timescale. I started tackling items on the list and felt quite productive on some days, but on other days I got hardly anything done. I started to sense a reluctance in myself. This came into sharp focus when another, really quite unpleasant, job presented itself, and I jumped to do it. Hmm, this isn't just laziness... I'm clearly avoiding the solar panel project.

What's my problem, then? I think that as the day of reckoning comes into sight - not just a test to see if it works, but a Tada! Finished! moment - I'm getting anxious about messing it all up. This kind of thing is probably stating the bleeding obvious to many people, but I'm not very good at being in touch with my emotions, so I have to resort to detective work to figure out what's going on in my head.

I realised that I've also been making things more difficult than they need to be in the name of efficiency. It really doesn't matter if I have to clean creosote off the paint brush several times. It doesn't matter if I have to make up several batches of mortar, even if that means wasting a bit. This was compounded by the way I wrote the list, with a couple of sets of jobs marked x3, lumping them all together into one. If I take away the restriction of doing certain jobs for all three panels at once, then I can focus on one panel at a time, which is less overwhelming. It also means I can get the first one up on the bank, out of the way, so I have more space to work on the next one.

Having given myself a good talking to this morning (with help from a sympathetic husband), I tackled one of the scarier jobs. I'd decided to make brick bases to stand the panels on, which required a bit of bricklaying. The only bricklaying I'd done before was the arch over the fireplace (not actually mortared in at the time I wrote that post - I did it more recently), which I wasn't very pleased with, so I doubted my ability to do the job successfully. The bases I had planned were pretty small, just four bricks each, two on two, but I think that might be even more difficult than a good long stretch in which each brick supports the ones on either side.

There were several other factors that added to the difficulty. I wanted a peg to stick up out of the centre of each base so that I could drill a hole in each leg of the panels and fit them on. (One job that I've crossed off the list was investigate tent pegs. I did, and found some old bent pegs that I'd failed to throw out, and they seem suitable.) To fit nicely, the peg would need to be vertical, the bricks would have to be horizontal, and the distance between the pegs needed to be fairly precise. It's no wonder I was wary of this job.

I'd done some measuring out, and cleared some turf to make space for the bases on the bank, so I had my bricks placed in position:

The floorboards were for measuring the slope of the bank. Fixing down the conservatory roof properly is below solar panels on the to-do list.

Having dithered about over whether to get ready mixed mortar or sand, cement and lime separately, I'd bought the latter after bumping into a friend in town who said he could use the rest of it (it's much cheaper to buy the components separately, but isn't available in small quantities). I double checked the measurements again, lined up various tools (spirit level, set square, tape measure), and mixed some mortar. I added far too much lime by mistake, so added some more of the other two, then found I had too much stuff to mix in my little bucket, so turned some of it out onto a school bus sign that was sitting around, before adding water and mixing. I was finally ready to start fixing my bricks in place.

It certainly wasn't easy, especially as I needed to be so precise with the positioning, but I think I did a reasonable job.

One brick base mortared in, complete with tent peg.

Two of the bases went onto the concrete wall-top at the edge of the conservatory. I'd deliberately shortened the conservatory roof to allow for this and I'm glad I did, as it's a bit tight for space here. However, most of the tent pegs were a bit long for use here. Where the bricks were on the ground I could bury one end of the peg into the earth (if I moved the stones out of the way) but not here. Luckily, I had two shorter pegs that I could use, so I did.

Commenting on the tight space there reminds me that I haven't told you about determining the position of the panels, which was a job in itself. I won't go into great detail, but I used the equation from this web page entered into a spreadsheet with solar radiation data from the same source, plus some zeros for times of day when the panels would be in shade. I then tweaked the figures for north-south orientation (or more relevantly, south vs. east) and tilt of panel until I found the maximum radiation captured. The results were 15° east of south and 53° from horizontal, which is our latitude. It was quite nice to see that come out of the calculations; it gave me some confidence that they were correct.

It's all very well knowing what tilt I'm aiming for, but implementing that on a sloping bank is another question entirely. I've mentioned a couple of features of my plan to meet this challenge - horizontal brick bases and floorboard measurement of the slope of the bank - but I'll come back to the rest of that in another post. Orienting the panels 15° east of south should have been fairly straightforward. All I needed was a compass, or so I thought. It turned out that some feature of this bit of hillside interfered with the compass. I could get a plausible reading for north-south at about four feet above ground level, but as I lowered the compass, the needle turned round until it was pointing more than 90° in a different direction. I dread to think what's buried there. (Actually, I was more than tempted to dig... but resisted.) Eventually, I decided that the fence was running pretty much north-south, so worked from that.

So far, I have three and a half brick bases mortared in place. I finished my batch of mortar after fixing the first layer of bricks of the fourth base. That's OK, though, because I'm concentrating on one panel at the moment, and setting the front two feet in place first before propping it up to determine where the back two bases need to go. Hopefully, when I check again tomorrow, the bases will be firm, still horizontal, and the pegs will still be vertical and the correct distance apart.

Signs of spring

All over the blogosphere, there are signs of spring. From snowdrops and crocuses, little white dots and fluffy cuteness, to wetter snow and daylight saving time. I guess you take what you can get if you live in Denver! Here, I have beer:

Clear signs of fermentation going on there

To be precise, I don't even have beer yet, I have fermenting wort, but it will be beer before too long. You may be wondering why this counts as a sign of spring. It's not even my first beer of the year. That may be true, but it's the first batch of heather ale of the year, made with the early flowers and new growth of the heather in my garden.

Flowering heather

I'm experimenting with a different yeast this time, so I'm not sure whether it will end up the same as last year's or not. Of course, I hope it'll be better but it might be worse - I'll just have to wait and see. In the meantime, I'm enjoying the increased daylight, flowers, and occasional sunshine.