Under the floorboards

For sometime I've been renovating my house, mainly to avoid doing things I need to do, like finish software, write etc. etc., so I wave my neighbours off in the morning as they commute to the codeface with a cheery wave of my trowel.  I don't hold with the view that the past is a guide to the future, but I think that if you don't know where you are coming from, you don't know where you are going.  Poking around under floorboards to remove defective piping and demolishing some decaying brickwork has provided some insights into energy use and sustainability, and oddly, the smoking habits of workmen over the past 100 years.

The remains of a clay pipe from 1901 and an empty packet of "woodies" from the 1940s or 50s.

I've recovered a few fragments of clay pipes, including a couple of bowls, pictures of Victorian builders often have a couple of blokes posing with a pipe.  A couple of butts smoked so far down that the smoker probably burnt his fingers could date from the 1920s or 30s.  Around 1950, the then owner rewired the house (partly because the previous wiring had started a fire), the electricians smoked filter tipped "Woodies" (introduced in 1948) and some unidentifiable brands, possibly including Craven A.  There are a lot of butts, many people smoked in the 1940s and 1950s, many, like my mother, acquired the habit during World War Two when long term health issues came a long way second to short term survival.  The dark world world between the rafters was next visited during the 1980s when central heating was installed and the house rewired, a few filter tips may have been dropped during this time.

An egg cup salvaged from quater of a ton of town ash that was used to support an angled wall, the same filth also yielded the remains of a marmalade pot.

The original 1901 builders seem to have used "Town Ash" as a filler to support sloping brickwork during construction and possibly to make mortar in places, maybe, because they thought they could get away with it.  They did, its taken them a 100 years for them to be found out.  Town Ash is just the stuff raked out of open fires and cooking ranges.  Having just removed quarter of a ton of the stuff, I would suggest that a late Victorian breakfast consisted of a boiled egg, toast and marmalade followed by a pipe of tobacco.  I'm trying to decide if ten bags of damp, black stuff are history or rubbish that has waited a century to be disposed of.

Whilst I have not found any, I have heard stories of builders using slag from Roman Iron works in the Weald.  The Roman connection may be fanciful, but the Wealden Iron industry was producing waste for several hundred years until iron production moved north as coal displaced charcoal as fuel.

It was possible that this pipe was installed in 1949 and was decommissioned in the mid-1980's, so this blockage accumulated over a 30 year period..  A fragile and smelly fragment of the Daily Mirror with a section of the Jane cartoon strip dated December 1949 was found close to this section.

One of the hardest jobs has been the removal of some iron piping, my guess is that this was installed around 1950 because of man's deep seated desire for hot bath water.  Iron was probably used for lack of anything better, but its not an ideal material for domestic plumbing, where the pipe had to be cut  to remove it, the bore can been seen to be constricted by a mix of limescale and rust.

1920's wiring, see text for description.  It was possible that this cabling was used for lighting and lead sheathed cable for power sockets.  The wood channelling is unusual.

It is the three generations of electrical wiring that are relevant to this blog.  The house was built in 1901 without an electricity supply, my guess is that this was installed in the early 1920s.  Only the ground floor was served with lighting and power sockets.  The wires are tinned copper and sheathed in rubber over which there is a fabric outer layer.  The live and neutral wires are separated in wooden conduits.  In the 1930s the cabling was extended to upper floor where the wires are the same, but the conduit is black painted metal tubing with clamps for elbows and tees.  Around 1950, the electrical wiring caused a serious fire.  The damage was repaired and the house rewired.  This cable is like modern "twin and earth" (T&E?), but made of different materials, the outer insulation could be polythene (a guess) the conductors are sheathed in rubber.  This survived until the 1980's when it too was replaced, this time by PVC T&E.

Cross section of lead covered cable, thought to have been installed around 1930, the cross section of the conductors appears to be larger than modern T&E cabling and the earth smaller.

When the house was built, it could probably consume about 10 - 50 kwh/day mostly in the form of coal for cooking and heating and some gas and rape seed oil for lighting.  There is a natural limit to coal consumption which is imposed by the capacity to shovel it and dispose of the ash.  With the advent of electricity this, this able to add another 5 to 20 kwh/day from incandescent lighting and electric fires.  Central heating lifted the energy absorbing capacity to well over 100 kwh/day.  For most of the 20th century energy prices were falling, if only as a proportion of household income, as prices fell consumption increased.  In the 21st Century energy prices are rising, but the legacy systems where were created during the era of cheap energy remain, making it difficult to cut consumption without the risk of chilblains.

Cabling from the 1950.  The outer sheath appears to be polythene(?) and the insulators around the cable appear to be rubber.

Climate and Sustainability

The the oil and gas industry has, within very broad limits an idea of the resources available to it.  Whilst it is possible to drown in a sea of numbers, it can be summarised as there always being  enough to fuel the next generation, say 30 - 50 years of supply, albeit with an uneven geographic distribution.  When I first became interested in wind and solar energy I simply wanted to know something about the energy resources of my back yard in the south of England.  This can be summarised as no potential for wind technology because my house is located in an suburban valley and sheltered from the prevailing wind, solar could make a contribution during the summer months, but not much during the winter.  Storage would help deal with the short term uncertainty of the weather, but not with seasonal variation.  As a result, I tend to favour buying energy from large scale sustainable sources rather than attempting to generate it myself.  This started me wondering about a framework for evaluating wind and solar energy.  Treat this post with caution, it evolved over a few cups of coffee and time spent looking at weather reports at  randomly selected locations around the world.

One starting point was climate and terrain (defined in such a way to include offshore areas).  I like to see the world in numbers like average wind speed, solar irradiance, the attenuating effect of clouds and likewise measures, but the potential for wind and solar devices in a given location can be felt on the face.  This might be summarised as "If you can wear a hat without fear of loss, it might not be a good place to put a wind turbine" and "If you don't need sunscreen, you might not need solar panels".

Economics has to be part of the scheme.  The volume of oil and gas reserves is related to price, if the price is low reserves which are in geologically complex areas or in harsh environments will not be economically recoverable, when the price rises, such reserves can be included in the resources available.  The same logic applies to sustainable resources, for example average wind speeds are higher offshore due in part to lower surface friction, but the cost of working offshore is significantly higher than onshore.  I am intrigued by the concept of airborne wind turbines which operate in the smooth air above the planetary boundary layer, but I guess the technology and economics are a challenge.  A similar logic can be applied to solar devices, the effects of seasonality can be offset by installing more panels, however, the system cost will increase.

Expectations affect how wind and solar systems are perceived.  I guess these can be summarised with three scenarios.  The first is grid-tied systems where wind an solar power is fed into the grid when it is available causing fossil fuel sources to be run down, when the wind stops blowing and clouds cover the sky, these are bought back on stream.  Off-grid systems rely sustainable sources, probably with storage and some form of fossil fuel backup.  It might seem a pointless distinction, but I would add "starting over" solutions as separate category.  I suggest that starting an energy economy from scratch might evolve some interesting solutions, possibly related to conservation, storage and management.  Along with expectation, goes realism, few people want wind powered railways and schools, hospitals and similar infrastructure need a lot or reliable power, but that still leaves a lot which could be configured not to.

Climate is largely determined by latitude and recorded in weather reports.  The Koppen schema has five top level categories and more than 20 sub categories, however, the relationship between sustainable energy sources and climate can be illustrated by just two diverse classifications.

Hot deserts (Koppen group B), e.g. parts of Arizona, which are within 30 degrees of the equator have relatively minor seasonal variation in clear sky solar irradiance, when clouds appear they are often high in the atmosphere and where they cause less attenuation than water laden low cloud.  Average non-storm wind speeds are relatively low.  This type of climate makes it possible, in conjunction with some storage capacity (if only because the sun does not shine at night) to maintain a more or less constant load from solar sources, onshore wind is less attractive.

Poleward of the hot deserts are the temperate maritime areas (Koppen group C).  Beyond 40 degrees of latitude, sun-earth geometry ensures that solar irradiance will be season, for example, in the south of England, the clear sky solar irradiance is something like 1 - 2 kwh/m2/day in winter and around 6 - 8 kwh/m2/day.  The clear sky irradiance is attenuated by clouds, in summer these are often intermittent layers of cumulus, in winter they can be dense stratus. which can reduce the solar irradiance to less than 1 kwh/m2/day.  Except for small loads, e.g. some traffic signs, off-grid solar systems are not viable in this climate.  In part, due to the proximity to the coast, average wind speeds on exposed locations such as ridges and hilltops can exceed 5 m/s.  Wind too is subject to seasonality it is stronger in winter when the dominant weather is fronts from the Atlantic, but even then, there can be intervals when the prevailing weather is high pressure over Europe resulting in still, clear air.  In general, wind becomes more reliable as an energy source with increasing latitude.

Wind Power - A view from 1910

I learned about "Windmills and wind motors" by F.E. Powell from a list of publications in an old magazine, the book was originally published in the US in 1910.  A scanned version is available in the internet archive of the American Libraries, a not-for-profit organisation to whom I would like to say thank you.  Increasingly, my reading material is coming from either the internet or car boot sales, I appreciate that my reading choices  are not constrained by the need to search for bits of paper, although that is something I enjoy doing.  A link to the book can be found at the end of this post.

Mr. Powell is an enthusiast for his subject, but unlike many enthusiasts for the technology, he understands that wind is a non-continuous form of energy which requires storage (banks of accumulators) in order to meet a continuous demand.  He is also quite restrained in his reference wind speed which is 16 miles per hour which is approximately 7 metres/second.  This amount of wind occurs frequently in many locations, this is in contrast to many modern wind turbines which are rated at 15 metres/second, a speed which occurs less frequently.  Chapter 6 is entitled "The production of electricity by wind power" and is a good discussion of the problems which need to be solved.  As the book was written well before the electronic age, control functions are implemented using mechanical or electro-mechanical devices which makes you appreciate the capability and availability of devices like mosfets, comparators and even computers.

The book appears to be intended for model or amateur engineers and as chapter 5 describes the construction of a machine with a rotor diameter of 10 feet (approx. 3 metres), fairly serious ones.  I admit to reading the descriptions of constructions fairly quickly, but I liked the method rotor hub construction in chapter 4 which consists almost entirely of wood and which could be made using only hand tools:

Many of the components do require access to a reasonably equipped workshop and an ability to use lathes and engage in pattern making.  This book was written at a time of rapid development of engineering and production processes and the artisan type skills needed would have been more widespread than they are today.  Model engineering magazines and related material turn up frequently at car boot sales.

I was originally drawn to this book in the search for technological history.  Wind power was a mainstream technology in the 19th century, although it was being challenged and displaced by steam towards the end.  wind was used for pumping water both for irrigation and drainage, grinding corn and working saw mills and sailing ships so there must have been a considerable knowledge of both the machinery and of wind as an energy source.  Wind powered electricity generation is clearly not a new idea and one which has been evolving for more than a century and that the Danish government was supporting research into the potential right at the start of the 20th century.

Link to scanned version of complete book:

Internet Archive

Seven Windmills

Last weekend I purchased a small booklet entitled "Windmills of Sussex" at a car boot sale.  This work was an expanded version of "Seven Sussex Windmills" which was probably published sometime in the 1970's.  If you like second hand books, car boot sales can represent the high and low points of book hunting.  There are two rules, first, the probability of finding something interesting is inversely proportional to the distance travelled and secondly, If you like a book, buy it then and there because it won't be there next week.

Windmills are interesting because they are sited at locations for which there is no obvious source of wind speed data other than the mill itself, so how did millwrights and owners decide where to build.  In the 19th century there was a substantial number of millwrights equivalent to the wind turbine industry of today and part of their expertise must have been a knowledge of wind and terrain.  Whilst there are descriptions of wooden post mills being dragged from one location to another by teams of oxen which suggests that if a location proved to be unsuitable, there was a chance of moving on.  However, the this was not possible with the large brick built structures that appeared on the latter half of the century, therefore getting it right first time was important.

When I first became interested in wind energy, it became clear that the variation in wind speed over a small area can be very large.  In the coastal town where I live the wind coming of the sea can be a smooth 10 m/s on  the seafront, my backyard can be calm and the foothills gusty.  The variation is due to terrain and surface texture.

The SRTM dataset collected by the Space Shuttle in 2000 is a good tool for displaying terrain.  I wrote a very basic programme to draw custom contour maps centered on a given location.  These can also be used as overlays with Google Earth which provides some additional context.  One, trivial exercise consisted of walking across the South Downs from the seaward side, over the crest and down the landward side with a wind speed meter and relating the results to reports from an airfield a few km to the west (This is described in a previous post).

The plots below are for the "Seven Sussex Windmills", the location of each being obtained from Wikipedia:

Argos Hill

Clayton

Nutley

Polegate

Shipley

Punnett's Town

West Blatchington

With the possible exception of the Polegate mill, all are located on hills, ridges or open ground.  A similar exercise with wind farms produced similar results.  What I would like to know more about is seasonality of milling with wind.  At a guess, its seasonal peaking around August and September after the harvest has been gathered in.  If it is seasonal, the location of the mill would be influenced by the prevailing wind after the harvest.

References

Windmills of Sussex, Brian Austen, Sabre Publishing 1978

SRTM - Wikipedia

Windmills in East Sussex (Wikipedia)
Windmills in West Sussex

The wind, mobile phone and the Space Shuttle

How to make this stuff exciting.....

Recently I was chatting to a neighbour discussing the usual things that people who live in the same street do, the vagaries of the council, chainsaws etc..  He is a journalist who sometimes does features involving large industrial plants, and I was envious when he showed me some photos of himself and others wearing hard hats and dayglow jackets and almost jealous when he flashed up a photo of an offshore jack-up construction vessel involved in high voltage electric cable installation.  This is an outburst like that of a comedian which went something like this "...I want to be a real actor... and wear tights".

A screenshot......

This exchange did highlight one of the problems with software and by implication things like energy management.  Much as I love software, it is difficult to make it exciting.  As a project manager, I was often faced with the problem of making the product and the people who produce it interesting.  Often a software development team is just a load of men and women sitting around an office, occasionally, drama erupts as a QA/QC person challenges challenges a programmer on a feature which then becomes an exchange of comments on dress sense, harmony is restored when it is agreed that the client/management was clueless and did not know what they wanted.  Hint - don't listen to the vocal minority of users but seek out the silent minority as more often than not, they will tell you what you need to know to stay in business.  No wonder that the most common expression of software is a screenshot.  Someone sitting in an office in a hard hat just invites comments on the level of building maintenance.

My experience is in decision support systems, but I have been intrigued by the way that cars have become software products, although I have yet to hear two owners discuss which version of software their car is running.  Like many engineers I was drawn to cars and motorbikes as a young man.  In the 1970s a petrol engine was a collection of more or less independent mechanical systems.  For example, the timing of the spark which ignited the air/fuel mixture in the cylinders was determined by something known as the advance and retard mechanism.  One form of this was a centrifugal governor whose origin dates back to the steam engine, as the engine speed increased, the relative position of the distributor shaft was adjusted so that the spark plug fired earlier in the compression stroke.  Similarly, the carburettor was a venturi which sucked more fuel into the airstream as the engine speed increased, often greater control over the air/fuel mixture was given by a needle valve mounted on a damped and spring cylinder which retreated further into a housing as the vacuum in the manifold increased as the driver's foot opened a butterfly valve.  A modern petrol engine is a system of sensors and actuators coordinated by a computer.

Device for measuring the voltage produced by an ignition coil

This approach resulted in significant gains in fuel efficiency. During my later student days I was the proud owner of a 997cc BMC Mini (as designed by Sir Alec Issigonis) this had a kerb weight of around 650 kg.  Three or four students could move a Mini around a car park by picking up the rear wheels, this was great fun if it was not your Mini.  Despite careful driving and regular maintenance I remember fuel consumption as being around 40 mpg.  The modern BMW version of the Mini has a kerb weight of around 1,100 kg and fuel consumption in excess of 60 mpg.  I guess that the engine management system is produced by men and women sitting around an office.

How to make things attractive is a theme that runs through energy management. An example is LED lighting which with careful design and installation can lead to a significant reduction in domestic electricity consumption, since we have been replacing CFLs with LEDs our consumption is drifting down to around 5 kwh/day or about half of what we were using 5 years ago.  If every household could cut its consumption, the pressure to build new fossil/nuclear generating capacity is reduced.  The automotive industry has demonstrated its ability to develop technology, is something similar possible with domestic energy consumption?  An interesting line of enquiry is the application of the storage systems being developed to electric vehicles for home and office use.  For example, adding  5- 10 kwh of storage to a house enhances its ability to use off peak resources and use the grid to obtain electricity generated from sustainable sources.

How do you pose with an LED light and look as purposeful as a man in a hard hat and dayglow jacket who is operating a large crane?

Soil, temperature and moisture

I started collecting soil temperatures in a randomly selected part of the back yard in August 2012 in an attempt to understand why beetroot was reluctant to germinate in April and May, but was quite reliable during July and August.  For no better reason than it was a convenient time to sit in the garden, the temperatures were measured around sunset on a Sunday afternoon.  Whilst this was convenient and consistent with regard to forming a time series, it was poor experimental design, by sunset the soil was usually warm, so on an April afternoon it was probably 10 deg. C, warm enough for some native english species to germinate.

One day in April, I had occasion to make frequent visits to the garden from early morning to late evening to make use of the time I decided to measure the soil temperatures over the course of the day.  The graph from this day's activity was quite instructive:

This shows that the variations in soil temperature during the day are much greater than that of the air above it. A crude extrapolation suggests that the temperature of the topsoil (0.1m) might have been from 2 - 16 deg. C, and for the two centimetres where seeds are sown could have been much greater.  During the day, the soil is warmed by the sun, during a clear night it experiences radiative cooling.

I had an attempt at taking soil temp measurements during the day on 25 July when the weather had been warm and dry for several days.  This exercise came to an abrupt end around 14:00 when a lone shower of heavy rain arrived.  The temperatures that were collected at a depth of 0.1 are shown in the graph below:

The maximum air temperature was around 25 deg. C when the soil was noticeably warmer than the air above it, it looks unlikely that the soil temperature fell to less than 10 degrees overnight.  When the surface temperature is high, it is clear that the top .01m of soil starts to loose moisture rapidly.

Do the low night time temperatures during April halt germination?

I'm new to gardening and a little lazy, so my method of sowing is to rake the soil and remove the building rubbish that abounds in the garden and then plant the seeds in a two centimetre groove formed with my index finger.  Over a few weeks it became clear that there were significant variations in moisture content.  The human body is a good measuring device for all sorts of things, e.g. solar irradiance, wind speed, humidity, air quality and soil moisture content to name but a few, the downside is that it does not produce graphs.

Over a few days I collected three soil samples from a bit of the garden that escapes watering, each sample was about 200gm (a half dog food tin), these were left to dry in the sun.  The moisture content being estimated from weight of soil at the time it was collected and its weight after drying, the resulting numbers were then turned into a graph:

The sample collected after a hot day may have been inadvertently watered, so it could be an over estimate.  So as for temperature, there are considerable fluctuations in soil water content over a short time interval.  And the lesson from this, make sure newly sown seeds are frequently watered until the plants are robust enough to withstand the turbulent environment that is the topsoil.  I think I was taught that at school.

A very short history DC in the home

Except for the washing machine and the vacuum cleaner which live in the kitchen, the native voltage of electrical things in other rooms is or could be low voltage dc.  We're slowly migrating to LED lighting which seems to have a native voltage of around 3 volts, so each lamp has circuitry which drops the voltage from 240 volts AC to a low DC one.  The efficiency of this conversion process has increased in recent years as transformers and bridge rectifiers have given way to more sophisticated circuits.  However, there is still a small loss and cost of LED bulbs and similar devices includes the necessary circuitry.  This has caused me to wonder if there are any advantages associated with a low voltage domestic distribution system, it makes sense to deliver electricity to the home as high voltage AC, but most of it gets used as low voltage DC.  Most electrical storage devices are DC, if you start adding 5 - 10 kwh of storage to a household system, is it easier to do this with DC distribution, otherwise there needs to be an inverter on the output end of the storage which incurs further losses and costs.

This is not wholly relevant to a modern household, but in the process of renovating my Edwardian semi I have unearthed the remains of a DC electrical system.  The house was built in 1901 and was lit by a mixture of gas mantels and oil lamps.  The remains of the pipes that distributed gas around the house can be found under the floorboards.  The location of the burners is often marked by a blanking plug, sadly the piping is too small to be used as the conduits for electrical cable.  I'm guessing, but mains electricity was probably installed sometime between 1920 and 1930 and there have been three, possibly four generations of wiring since then.  The first wiring consisted of fabric insulated wires kept apart by channels in a wooden conduit, at some point these were replaced by what appears to be lead cased cables, fortunately these have been replaced by modern PVC insulated cables.

Oddly, when the house was built it had a DC system of sorts.  This had two functions, one of which is still in use today.  The two main downstairs room each had a button which agitated an indicator system in the kitchen to alert the live-in cook/housekeeper of someone's need of something or that the front door needed answering.  This is neither a large or grand house and I regularly walk to the kitchen to make tea without suffering excessive fatigue.  When the indicator board was removed, possibly because of the lack of a servant to respond, it was replaced by a make-and-break electric bell operating off a 6 volt battery.  Yet again, this is a guess, the indicator board might have been powered by a lead acid accumulator.

There are some vague family memories of accumulators, mainly related to pre-war radios.  Early valve radios had two batteries, one known as the high tension battery which provided the potential for the anode with a voltage of between 40 and 120 volts, the current drain was low so they lasted a long time, but they were expensive.  The second battery known the low tension supply provided between 3 and 6 volts to heat the cathode which drew a much higher current, often accumulators provided this supply.  The younger members of the family had to carry these things to a local shop where they were charged up for a few coppers before being dragged back.

Accumulators must have been mainstream technology before WW2 as even my non-technical family seemed to have working knowledge of the things (as a boy, I was told not to stand on electric cables as the current could not flow, there is little to suggest this was a joke played on a child).  I have no idea how this conversation started, but I was chatting to a lady, maybe a little older than myself who in her youth had helped her father who was a motor mechanic refurbish batteries.  She described scraping out the old sealant so the plates could be removed, these where held together by bolts so they could be separated, cleaned an refilled after which the battery was resealed. The non resealable accumulators required regular checks for both the level of fluid and its specific gravity.

Its stretching a point, but there is some historical basis for the concept of a low voltage home.