Building a Simple Electrical Heater - Part 2

Recent additions - electrical heater box and growlight panel, both on test

I've put this on a separate post to my original, because the whole design has now become a little more complex !

After building the two identical electrical resistance heating elements, I spotted a 6" (150 mm) 24 VDC fan at our local car boot sale a couple of weeks ago.  This was snapped up for £2.  

the fan....

With this addition, I thought I could maybe improve on my original free-convection idea and wire up this fan in parallel to our two heating elements, to push the air over the heaters.

Building a Simple Electrical Heater

This is following on from my recent post on the greenhouse solar installation.

To use any excess panel energy available during the cooler months, I've built electrical heating elements to connect directly to the 'dump load' circuit from the charge controller.  There are no proprietary heating elements available for the power and voltage I require, and even if there were then they'd likely be prohibitively expensive.

The first job was to source some suitable resistance wire.  Lots of types available on eBay but not too many which are insulated, so I opted for enamelled 0.7 mm diameter Isotan wire (aka Konstantan) available from a seller in Norway.

The reason for buying insulated wire was that it could be formed either in or around metal pipe or ducting.   In the end, I opted for inserting it in small-bore copper tubing, a coil of which I had lying around the workshop.  

However, this wasn't the only choice for the design - I'd originally envisaged simply wrapping the insulated wire around the outside of a 22 mm diameter copper pipe, but I didn't have any to hand and B&Q wanted £17 for a 2 metre length....

I unrolled the small-bore copper tubing coil and measured its length at 7.2 m.   A few basic calculations were carried out to establish the heating power available from the lengths of tube and wire I had.   

Standalone Solar Installation....

We decided it would be good to have some electrical power in the greenhouse, primarily for growlights and at least one of our electric propagators during the winter months.

Taking power via a spur from the house mains is not so easy - there's nowhere to run a cable underground without cutting slots across at least one concrete pathway.  The best alternative solution would be overhead, from the house wall via a cable supported by a catenary wire.

However, the amount of power we're looking to draw is not huge, and so we've simply relocated three of the solar panels from our experimental array onto the greenhouse roof.

Solar Panel Performance - two years on

It's that time again...  

As of this evening, we now have exactly two full years' worth of data from our experimental 540 Wp solar array.  So, here are the graphs of the same parameters as previously reported - clicking on them shows larger images, and they can be compared with last year's figures here :-

Total AC energy production this year was 243 kWhr, i.e. just 2 more than last year !  At least the numbers are consistent.

Monitoring Electrical Energy Use / Consumption in the Home....

With electricity prices becoming increasingly expensive, and likely to continue to rise way above inflation, we recently concluded a seven-week long experiment to monitor the energy consumption of most of the electrical appliances in our home.    

The plan was to identify those energy consumers for which there may be scope for a saving, by either changing their pattern of usage or replacing older appliances with more modern and efficient units.  

However, replacing any items would only make economic sense if their total capital costs could be recouped from the predicted savings in their currently-measured operating costs within a period of say five years maximum, or if they should become faulty or breakdown in the future.  We don't intend to discard otherwise serviceable appliances simply because they may not be quite as efficient as the very latest designs on the market.

The five years is actually slightly longer than the period in which I'd normally expect a payback against any such renewal purchase - three years would be nearer the mark.  However, with energy price inflation over the past five years running at around say 8% compared to more 'general' inflation at around 4%, i.e. twice the rate (and no signs of this trend ever coming to an end - see my previous post), then every £1 worth of electricity energy today will actually cost £1.48 in five years time, whereas that unit £1 cost of appliances today will be just £1.22 at the end of the same period.  

To put it another way, cash in the bank in today's money to be spent on future appliances would have been devalued by 18% but cash kept aside for future energy bills will devalue by a whopping 32% after five years.   Therefore, it may make economic sense to bring forward certain renewal purchases because the time they will spend consuming less energy in the future will produce exponentially greater annual savings.

Anyway, back to the testing.  We already had a couple of simple plug-in energy monitors that we'd bought for our micro-generation experiments, and we first established there would be three categories of consumer in the house to be monitored during the experiment :-

Paper logs & briquettes - Part 2

We finally bit the bullet and ordered one of those cross-handled briquette machines from the internet.  Despite my whinge last year about the upfront cost and relatively poor returns compared to coal (see my previous post) it seemed a much quicker and simpler way of making free paper bricks than the rather tiresome process of using our home-made versions.

Incidentally, this year we paid £6.30 for each 25 kg bag of run-of-the mill house coal, 50p (and 8%) more expensive than last year...

We actually bought a top-of-the-range briquetting press, for £20 delivered, although there were lighter-duty versions available on eBay for around a tenner.  This one seems to be of more robust construction and even has round plastic handles - I wouldn't want to be putting my full body weight on the thin steel sections of the cheaper versions, at least without very thick gloves to protect my hands..

After a full day-long shredding and tearing campaign, we let the mash soak for around three days in a big plastic container.  A whole year's worth of eBay invoices and other old bills, plus a couple of months of free newspapers.  There were even a few thick glossy catalogues in the mix, from Tesco and Argos et al, around half-an-hour each to tear them up by hand into usable paper strips.

the briquette press and the container with the mash....

Removal of the Wind Turbine....

A couple of months ago, I noticed the wind turbine had stopped producing electrical energy and so I took it down and had a good look at it.

It turned out to be a relatively simple fix, just to replace a drive key that had sheared on the gearing, but in the end I decided not to repair and re-erect it. 

So now it's languishing in pieces in the shed and workshop, the reason being it's simply not cost-effective for it to continue to operate - see my previous post.

I haven't totally given up on domestic wind energy though - I'd still like to design and construct another and larger experimental version of perhaps a combined Savonius / Darius vertical axis machine.

Watch this space for future developments....

When less means more....why electricity prices will rise and rise....

Electricity prices are going up – that much you already know from your bills.  You'd think the only option is to use less of the stuff....

Well, get used to the idea - they're going to continue to go up, and the less electricity everyone uses then the higher the prices are going to be.

Why is this ? 

Some commentators blame energy price rises on the lack of new oil and gas reserves, the expense of their extraction, or political instability in the major producing regions.

However, the real reason is much simpler.  Do you really think that the shareholders of these energy companies are going to suffer simply because you use less of their product, particularly when they feel they're forced to operate in a grossly distorted market ?

In a way, of course, they have a valid point... 

Electricity cannot effectively be stored in large quantities and therefore energy on demand is provided by standby and swing capacity units, namely thermal power stations - those things that burn fossil fuels to keep the lights on come what may.

Forget the wind farms, when the wind doesn't blow the standby stations have to kick into action and make up the entire shortfall between demand and supply. 

The trouble is, of course, that all of the fixed costs associated with maintaining and operating a 'big block' asset must still be met even if it's producing nothing at all for periods.

There's debt to be serviced, sustaining capital to keep the asset up to scratch, spare parts for equipment, maintenance costs and plant operators sitting around doing nothing at all but making themselves available 24 hours per day for when the big block needs to kick into action.   

And all this against a backdrop of increasingly stringent and costly environmental, employment and health & safety legislation with which it's necessary for them to comply.

Converting a 2.3 kW Generator Alternator to Belt Drive.....

As part of my mini CHP project - more on that in a future post when it's a little further advanced - I bought an old petrol-driven generator set on eBay for £51.

It was only the alternator and panel etc I really wanted, but the old genset had a few other things I could use, such as the frame and fuel tank.  Everything seemed to be working fine before I started taking it apart.

However, when I stripped the generator off the engine, I discovered that there's no front bearing assembly within the generator.  In its original configuration, it plugged directly onto the engine shaft and therefore simply used the crank main bearings for its front support.



the re-assembled 4.5 hp petrol engine after stripping off the genny - the
engine's going up for sale on eBay shortly

the generator....

Solar Panel Performance - one year on

We now have one full year's worth of operational data from our five-panel experimental array, rated at 540 Watt-peak (Wp) in total.

So, without further ado, here's the cumulative AC energy graph for the array from 04-May-12 to 03-May-13.  Click on the figures to make them larger and easier to read ...

and here's the output on a month-by month basis.

and on a 'unitised' basis, i.e. per installed Watt-peak of capacity.

Our forecast in my post from 04-Nov-12, on the economics of the array, predicted an annual output of 254 kWhr of usable AC electrical energy, but we actually only achieved 241 kWhr in the period. 

Domestic Solar versus Domestic Wind ? Solar wins, every time....

I still see people on eBay bidding hundreds of pounds for 300W domestic wind turbines.  Some of the sales sites use terms such as '..free energy...' and '...save money...'. but these claims simply don't stack up....

Given that you can buy 170W solar panels on eBay for around £80 or so each, let's do a very simple comparison based on real data from my own experimental installations of both solar and wind (see my previous posts for more details on each).

Since 300W is a common-enough domestic turbine rating (based on a 1.4 m blade sweep), we'll do the numbers based on 300W. 

Let's assume that whatever installation materials / batteries / controllers / inverters / instrumentation / cabling etc you'd need for one system would cost exactly the same as for the other.

Let's also assume that you've bought your 300W turbine on eBay for £160, the same price as two 170W panels.  To make it even simpler, we'll also de-rate these solar panels to a combined 300W watt-peak output.

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...

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.

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.