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Sunday, 28 September 2014

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.



Friday, 12 September 2014

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.












Friday, 5 September 2014

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:

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