Home-made Solar Panels - Part 2 - Operational Data, Costs & Economics

This is the promised second part of the Solar Panels post.  In this, we'll take a look at Operational Data, Costs & Economics.

Operational Data

The first panel was commissioned on 03 May and the fifth on 20 June.  Operational data was collected on a daily basis from the time the first panel was in place, and so at the time of writing we've exactly six months' worth of data. 

This summer has been very much a mixed bag in terms of weather - May wasn't too bad, June was very poor and the beginning of July only a little better, but since then it's been more typical of what we can generally expect around here.

Graph 1 below shows the total cumulative energy from the array since the time of hooking up the first panel.  The curve starts off rather shallowly and then gradually steepens as more panels become live, but the gradient is not as high as expected since the weather worsened through the commissioning period.  

Note that all of these graphs shown here represent net AC energy provided to the house grid, i.e. all the losses and inefficiencies in the grid-tie inverter during rectification and transformation from DC to 240V AC are already accounted for.  The light red line on the graph is a linear trend line.



Graph 1

(click on any of the figures for a larger image)

Going off-grid... Part 1 ... Musings on the possibilities....

Firstly, my apologies for what is quite a long post without any pictures to break up the text....one of the advantages of writing this blog is that, for potential major projects like this one, it focuses my ideas and also forms a written Design Basis & Facilities Description for me to refer to in the future, and is a basis for comparison after completion....

I think it would be very good for the soul if we could be totally independent of our electricity supplier and run the entire house off-grid.

How can this be achieved ?  Let's look at the possibilities....

Paper logs & briquettes – Solid fuel for free ?

Like most households, the amount of paper regularly pushed through our letterbox is astounding.   Every week, we receive reams of local advertising material within what are laughably called 'free newspapers', plus flyers for local take-away food services, insurances, garden clearance, roofing, TV aerials and just about anything else you can think of.

Even the postal service gets in on the act, routinely delivering one or two pieces of junk for every real letter which is actually addressed to us.

The addressed mail we receive, from bills to further targeted marketing guff, also eventually needs to be disposed of – anything that has our names or address on it gets shredded as a matter of course.   The remainder of the junk paper is all just dumped in our blue recycling bin and collected by the council every fortnight.

At least until recently.....

We have an open fire in our living room, fronted by an Edwardian cast-iron insert with a mahogany surround that we bought very cheaply on eBay when we were renovating the house.  We replaced the old cracked picture tiles with new picture sets of the wife's choosing, gave the iron frame a good wire brushing and a fresh coat of high-temperature paint, extended the depth of the fireback with some thick steel sideplates and then installed it.  The fireplace in the chimney breast had been blocked up years ago but we opened it up again, enlarged it and brought this great feature back to life.

the fireplace....

We're lucky enough to live in an area which is outside of the urban smoke control zones, and so we can burn wood and coal etc in an open fire.  If you're within a smoke control zone, then you can only burn these materials in an 'approved appliance', usually an enclosed wood burner or similar.

Anyway, back to the story.... 

We buy coal in 25 kg sacks (currently £5.80 each) from a local merchant and we've literally a shed-load of logs from an ash tree bough that broke in high winds last year, and also from the trunks and branches of our own hedge and tree removals.

Last month, I was searching on eBay for an old & cheap hydraulic press for the workshop, and one of the items on offer that struck me was a hydraulic paper-briquetting machine.  This started me thinking, and so I then searched specifically for those manual cross-handled presses I'd seen years ago.  Still plenty of companies selling them, but the cheapest on offer was around £13 delivered and I'd no idea what the build quality would be like – from the photos, they don't appear to very substantial and might damage easily.

Now, you might think £13 is not a lot of money, but in this context it's very significant.  I could buy 56 kg of coal for that money, and even burning all the paper logs we could realistically make in a year probably wouldn't produce the same heat output as that mass of coal.  Coal is a fabulous fuel with a high calorific value and it burns very hot – it's little wonder that Britain's prosperity was built on it.

Still, even low-grade fuel from waste paper is a tempting prospect if it's completely free – we don't even have to go out to collect the waste paper, it gets delivered to the door !    So we just needed to work around the requirement to buy a machine to compress it...

So, here's a couple of ways we came up with to make the logs, just using things we already had to hand :-

Mastic Gun – we've a few mastic guns and several old cartridges with contents that are well past their best and should have been thrown out ages ago.

I pumped out the remains of an old sealant cartridge and cut the end off it.   I also made a rough blanking plate from a scrap piece of thick plastic. The blanking cap shouldn't be a tight fit in the cartridge – it must let the water past –  and so it can be quite rough.

We experimented first with material from the shredder bin.   This was also an excuse to get rid of all those eBay invoices, old bills and other papers that were piling up on the shelf, and so the process began with a shredding campaign. 

The shredder bin was tipped into a washing-up bowl filled with water, mixed and allowed to soak.  The mash was loaded into the cartridge with the blanking cap at the bottom, pushing the mash down with fingers several times and adding more until it was as full as possible.  The cartridge was then loaded into the mastic gun, and the gun pumped as firmly as possible....note that water escapes from both ends, since the gun driving washer is not a tight fit in the cartridge.

shredded paper in the mash...

We left it for several minutes under pressure to consolidate, gave the gun trigger a final few squeezes, and then removed the cartridge.  Using a piece of wood as a mandrel, we held the cartridge and pushed on the blanking plate and, hey presto, out popped a damp paper cylinder. 

very simple - cartridge, rough blanking plate
and a log made from it....

in the mastic gun under pressure....

We made a few more using the mastic gun press – they were a little fragile at the wet stage when removed, but we laid them out on an old cloth for a few days and then placed them directly on top of the central heating radiators in the workshop for a few weeks.  At this time of the year we use the heating sparingly and only ever in the evenings, and so the log drying time was prolonged. 

However, the end result was paper fuel logs which were dry, hard and of sufficient strength to be handled quite roughly without falling apart.

Home-made Screw Press – I had a piece of thick-wall aluminium tube lying around in the workshop, but although it's ideal as a log mould I didn't want to damage it because it's valuable and bound to come in useful for something more profitable.  Any design I could produce therefore required the aluminium tube to be a passive component, with no cutting or drilling.

So, I made a simple screw press from a length of 8 mm steel bar that I threaded at both ends, one end with quite a long thread length.  I made a threaded end plate and loose-fitting piston for the tube on the lathe, using some plastic barstock – I appreciate that most people don't have a lathe, but you could still make these items using just a hand saw and a few scraps of wood, they don't have to be precision engineered.   Threaded steel bar is also available from DIY stores and those hardware & tool traders we see at car boot sales, but obviously if it's more than a few pounds to buy then it defeats the object of making such a press yourself. 

So now we had a log mould of roughly twice the diameter and twice the height of the mastic cartridge, i.e. eight times the volume.  Exactly the same paper preparation process as before, but this time compressed by tightening a nut and washer against the piston within our aluminium tube.

screw press - twice the size of the cartridge...

Again, our first tests were with shredded paper.  When we pushed these longer formed logs out of the tube, they generally fell into two or three pieces but we just gave each piece a consolidating squeeze by hand.  The presence of the central screwed bar also made the wet log removal process a bit trickier, and contributed to the breakages. 

However, these breakages actually turn out to be an advantage, as they produce shorter log lengths that are more suitable for the size of our fireplace. 

first batch of logs for testing....

We also made some logs from newsprint, but for these we didn't bother shredding the paper.   We just pulled the newspaper into separate sheets, folded them and laid them in the bowl of water.   After experimenting a bit with them, it seems easier to soak them for quite a long time, maybe even overnight, and mix them around the bowl by hand until you've a wet and grey muddy pulp that's barely recognisable as paper.

In this form, although they're a bit messy to handle, they make dense logs that hold together – if the papers aren't wet enough, they tend to decompress a bit and open out slightly when removed from the press, although they still dry out and burn OK.

newsprint logs - the left one was not soaked enough and has
sprung open, the right one is from fully pulped paper

In conclusion....

We found the type of paper used had a big influence on the log making – I've since shredded several old confidential client reports that were produced on a thicker-quality paper, and these logs didn't hold together nearly as well as those made from newsprint or more run-of-the-mill printer paper.   I think the trick will be to mix the thicker stuff together with the thinner when doing a shredding run.

Those logs produced using the screw press were noticeably denser than the ones made with the mastic gun.  This is to be expected, because it's possible to apply much more compressive force on the mash in the tube using the screw.

All the logs we made eventually dried out very well to make usable fuel.  So, I think we've found a couple of ways to make some totally free fuel logs.   However, they're a little fiddly and time consuming to make with these types of home-made presses – if you intend to be serious about it, maybe come up with something that's easier to load and press, for a quicker turnaround time.  If I see one of those cross-handled manual formers on an eBay auction for a fiver or so, I might even buy one.

So how well do the paper logs burn ?  They're a bit like wooden logs in that they need to be added to an established fire, but they held together and burned well enough.  They didn't leave much residual ash in the fireplace, unlike burning loose pages of paper which produces flying ash and needs a lot of cleaning up afterwards..

three paper logs on the fire...

An added benefit with these home-made paper logs and briquettes is that they're clean to handle when dry – after all, they were made from clean paper – and therefore you can store them in any indoor cupboard, unlike either coal or timber logs...

Inside the Wind Turbine....

In 2009, after we returned from a spell of working overseas, I started designing and building an experimental wind turbine.

However, what with work, moving home and other commitments etc, it actually took well over two years to complete and erect the 'finished' operational unit, and during that time the basic design had also evolved significantly.

the turbine as currently configured...

  

The turbine has been up and running in its present location for most of this year, and so I thought we'd give you a brief description of the machine.....

Thermal Solar Experiment – Solar Air Heater (Solar Furnace)

With the experimental photovoltaic (PV) solar panels in place and operating, I started to wonder about the feasibility of getting useful benefits from thermal solar panels.

PV solar is not particularly efficient, converting only around 12-14% of the 'insolation' into electricity for polycrystalline cells, and maybe up to 18% for monocrystalline cells. 

Insolation is just a word abbreviated from 'incident solar radiation', i.e. the amount of energy from the sun received at a particular location, and is usually expressed in terms of watts per square metre.  As a rough guide the insolation is generally around 1,000 W/m2 at the earth's surface, although it does vary by location.   The 1,000 W/m2 value is also the basis on which the rated Watt-peak outputs of commercial PV solar panels are determined.

Thermal solar panels can be much more efficient, when the intention is to convert the sun's energy to heat and not directly to electricity.

I watched a few YouTube videos on making solar air heaters (or solar furnaces, as they're called across the pond), and reasonable results seemed achievable from home-made versions mostly using aluminium drinks cans.

However, the techniques used all seemed a little fiddly and time-consuming, in that the cans required cutting of both their ends and then sticking together to form a stack, although undoubtedly it's a cheap way to try it.

The local wildlife...

As I've mentioned before, we live in a semi-rural location adjacent to farmland and a local woodland nature reserve, and we're lucky enough to see some of the local wildlife. 

So I thought I'd share some of our photos from the past year...

Hedgehogs
We've a family of hedgehogs nearby, that we used to think might live in a pile of old tree-cuttings just the other side of our hedge, but when we cleared the land (very carefully !) they were nowhere to be found.  They can be seen out and about quite often at dusk and beyond, and one night in August we were fortunate to see a pair of them together in our garden.

Maybe it's some strange mating ritual but, although I know nothing about hedgehogs, it seemed rather late in the year for them to be breeding.   They didn't seem to mind our presence or the flash photography at all, although we were very close.  

# ..... ISA ISA baby.....#

In praise of the ISA.....(that's the 'Individual Savings Account' in the UK, which allows you shield capital growth and distributions from capital gains and income tax respectively).

I've been fully ISA'd-up for the last two years (£10,200 limit in 2010-2011, and £10,680 in 2011-2012), and I've also retained holdings in an earlier ISA from contributions I made around four and five years ago. 

I haven't yet added to my ISA pot in the current tax year, but I definitely expect to again be invested to the current annual limit (£11,280) before 5 April 2013, and also every subsequent year in the future assuming I can find the funds. 

I also recently closed my regular trading account with TD Direct and so the ISA account and my SIPP are the only trading vehicles I currently possess.

Considering that I run my own company, and have very limited personal pension provisions, I stumbled upon the benefits of ISAs very late in life – too late, many might say.

Home-made Solar Panels – Part 1 – Construction ...

Earlier this year, we decided to have a go at making our own solar panels.   It's very much a small and experimental array to check out the construction techniques, the costs and the economics of solar generation at our particular location. 

We have a shallow low-level south-facing roof over the kitchen and garage, with an open aspect to the west, so this seemed an ideal location.

We bought a 1kW kit of 6"x3" polycrystalline cells which came complete with rolls of tabbing and busbar wires and also with the flux-pens needed for soldering of the tabs.

I also spotted a job-lot of ex static-caravan windows on eBay and bought 12 for £10 each.  These were single-glazed windows removed from old caravans during refurbishment.  It was a couple of hundred miles round-trip to collect them, but well worth it for ready-glazed aluminium frames.  The sizes I bought were all around 42"x32".

Five cleaned frames trial-fitted into our roof mounting structure

When you're working out how many cells can fit into your frame, bear in mind that the cells are not exactly 6"x3" – in fact, they're usually 150 x 80 mm and 80 mm is almost 4 mm larger than 3", so we know from experience that this can screw up your layouts if you're drawing up the panels when waiting for the cells to be delivered !  Our frames each allowed a maximum of 60 cells, laid in 5 rows of 12.

Camping in Europe...holiday on the cheap ?

It was time for a holiday, the first real one we'd had since a package to Turkey in 2008, although admittedly we did spend around a week very early this year driving to a few cities in Northern Europe.  

Although I get  to travel around the world occasionally with work assignments, and even take my wife on some of them, they don't usually allow too much time for sightseeing and just general chilling-out.

It's many years since I'd been to the warmer parts of Europe, and my wife had never been at all.  A timely lull in foreseeable work commitments coincided with the end of the mad August rush on the French Riviera, and so two or three weeks away in September was the plan. 

The initial intention was to just drive around and stop wherever we fancied, generally in the cheaper hotels and B&Bs, but if the weather was fine then we'd fit in a bit of camping instead. 

Effective tax avoidance – start the homemade Christmas wine now...

Making your own wine is a great pastime on many levels....

Firstly, it's very cheap and the taxman doesn't get to surreptitiously steal a huge chunk of your hard-earned readies.   How big is the chunk ?  Read on...

Just think of the 'Three for £10' wine offer at ASDA that's been running for years; that's a bottle of wine for £3.33.  Now this wine has been made in Chile, California, Australia, South Africa or wherever.  Grapes have been planted, lovingly tended, harvested and pressed, the liquid collected, filtered and then fermented, cleared, put in a glass bottle, sealed, labelled and despatched half-way round the world and it's still only £3.33. 

However, consider that sum even further.  The UK excise duty payable on any standard 75cl bottle of wine of that strength is £1.90*  – yes, a staggering amount on any bottle of wine but a very high proportion of £3.33.  To add insult to injury, the £3.33 selling price also includes UK VAT (sales tax) at 20%, on the whole amount including the £1.90 duty, i.e. there's a tax upon a tax, and therefore the exchequer has just grabbed a further £0.56. 

So of the £10 you handed over at the ASDA checkout for your three bottles, £7.38 has immediately been snaffled by the government.

(* UK Duty rates from 26 March 2012 on still wine of 5.5% to 15% ABV = £253.39 per 100 litres)

The bottle of wine has therefore gone through all the stages described above, plus being distributed to the supermarkets, for only 87p.  In the supply chain everyone, the makers, shippers, distributors and the supermarkets has made a profit from just that 87p. 

Home heating – living with what we have...

Our home is fitted with a ten-year old Worcester 15/19 oil-fired combination boiler which provides the heating and hot water.  Where we live, the other three houses also use domestic heating oil as a fuel source.

Unfortunately, domestic heating oil (kerosene 28) prices tend to fluctuate wildly in line with the world oil price.  There was also a step change in kerosene prices just a few years back, with the costs jumping by 50% from around 40p to 60p per litre in just a few weeks during a particularly cold winter period, even peaking at around 75p in some locations for a short time, and nationwide they've never fallen too far below the 60p level since.   Oil prices also suffer much more from 'downward price rigidity' than any other domestic fuel source, i.e. prices are quick to jump upwards on an oil price rise and very, very slow to fall when global oil prices fall.

Added to the facts that the UK domestic heating oil market is totally unregulated (sorry, I said no politics here...) and that most of the country's supply and distribution is in very few hands so that effective competition is non-existent, then those of us with oil-fired heating must simply endure huge annual costs, typically at least a third more than those with equivalent homes using natural gas. 

So what are the options ?  Let's base the comparisons on our annual heating and hot water costs of £1,500, which is an accurate reflection of the costs of last year's oil tank fills.

By way of an Introduction...

I can hear you yawning already – not another self-righteous blog by some rich git about how it's possible to live cheaply by boiling the snails you find in the garden, making fuel briquettes from animal dung, eating roadkill and generally reverting to a standard of living which was tough enough in the seventeenth century.....hopefully you'll find a bit more than that to engage with in this blog.

I'm a Chartered Engineer, but I'm also a time-served Fitter from an apprenticeship in heavy engineering (honestly, such industries did exist in the UK in those days), having gone on to university much later in life than most, after I'd already been working for around 10 years or so.

After a series of staff jobs (i.e. as an employee), I formed my own consultancy company initially as a tax-efficient way of continuing to do long-term contract work for the same sort of companies as I'd worked for in the past.  IR35 wasn't even a glint in Dawn Portillo's eye at that time (for the unenlightened, under the current IR35 legislation in the UK, those working full-time as a contractor for a single employer are subject to complex rules which effectively compels them to account for their own company's earnings in a specific way and to pay basically the same total amount of taxes as they would if they were a direct-hire employee).