Letting go.....

Whilst messing with some energy management software, I thought it would be instructive to take a broad look at electricity supply.  In reality a diversion into the general and away from the specific is displacement activity.  I'm still getting my head around this stuff, so treat this post with caution.

Go back forty years to the 1970's and coal was the dominant fuel used for electricity generation, nuclear power stations were beginning to come on line and there was a small amount of oil and hydro capacity.  Many large power stations were sited close to the coal fields that supplied them.  Visits to power stations were mandatory for engineering students and I went on two of these and at each one the importance of matching supply and demand was pointed out and illustrated with the same example, that of the Miss World Contest, at the end of this event, several million households all rushed to the kitchen to boil water in electric kettles with which to make tea, creating a massive spike in the demand for energy which had to be met from the "spinning reserve", maybe this was just a good story to amuse visitors, but it sounds credible.  It probably would not amuse my wife and daughter, both of whom have feminist leanings and both of whom have travelled extensively to meet people, which seemed to by the principal aspiration of most Miss World contestants.  To summarise, demand management appeared to be based on the weather, seasons and the TV schedules.

Move on forty years and electricity generation has become much more diverse with gas, wind and solar entering the mix.  Wind is a discontinuous source, on a windy day, wind might account for 10 - 15%  or more of the demand for electricity, on a calm day this can get close to zero.  Looking at the supply of electricity, it appears that gas powered stations act as "back up" for the wind farms, this may not have been the role that investors in gas powered stations envisaged.  In short, the management and economics of electricity generation appear to have become complex.  Variations in strike price for different forms of generation and auctions to maintain capacity do not appear to contribute anything in the way of simplicity.

From the perspective of a naive observer it seems that we are doubling up on generating capacity because of the fickle wind and shifting sun, sustainable sources have to be backed up in some way.  The critical technologies would seem to be demand management and storage both of which could ease the integration of sustainable energy sources and reduce the amount of doubling up.

The peak demand for electricity is during the day and early evening.  The peak demand can either be met from bringing generating capacity on line, or reducing the demand.  The internet of things can make a contribution to managing demand, the frequently quoted example is turning of the fridge in the early evening during evening when many families are cooking meals and doing things with electrical appliances.  It's not beyond the imagination to imagine a system that prioritises the use of energy, turning some things off to free up resources and facilitating tasks that can't wait and then reconnecting them at a more convenient time for the electricity supplier.

There are many ways such a system could be configured.  At one end of the continuum the system boundaries could be drawn at the household or office level, In this case the maximum load on the grid is defined and decisions about its use made by the people inhabiting the unit.  At the other extreme, there could be centralised control.

My guess is that the technology is not the problem, instead it is making it acceptable to the energy consumers.  A key element would be the design of the tariff which would make it attractive for users to stay within the maximum load restriction.  Having discussed this with a few people, including one of my sons, the usual reaction is a lack of willingness to pass control of one's fridge to a third party. the "big ask" of this scheme is to forfeit autonomy for objectives which are remote from the average householder.  These include investing in technology other than generating capacity and improving the management grid management.  For this reason, I would suggest that politicians will be slow champion  this concept.

Exploring the Wind

When I first became interested in sustainable energy, my first thoughts were "haw much wind and solar energy is available.  A large chunk of my life has been spent poking around datasets, mainly those related to hydrocarbon exploration and production, so for me a logical starting point was to seek out sources of wind and cloud data.  This post is collection of personal observations, anyone wishing to acquire a wider knowledge is encouraged to seek out more authoritative material.  For the sake of brevity, nuances and detail have been omitted.

If I was starting again, the first task would be to read a couple of textbooks on global climate and air circulation in particular.  Whilst browsing books at a car boot sale I came across "Climate, Soils and Vegetation" by D.C. Money, this and Wikipedia provided a useful, if belated, context for the maths and stats.

The actual starting point was a sample of Metar and similar weather reports and then attempting to reduce them to Weibull distributions.  One of the locations was an airfield which is approximately 10 km to the west of where I live.  The average wind speed there is around 5 m/s, the surrounding terrain is flat and having stood, with a simple anemometer, on the roof of a WW2 pillbox which overlooks the site, it appears that the air flow is smooth with little turbulence below 10 m/s. In contrast, where I live, the average speed is less than 3 m/s and very turbulent.  Weather data is collected to support human activity, frequently transport, where the objective is to provide pilots, sailors, road users with an indication of what forces of nature they will be exposed to.  This data may not be relevant to other nearby locations with different terrain and land cover.  It is a gross oversimplification, but the average wind speed for a selection of onshore locations  in Western Europe and North America was in the range 4 - 7 m/s with Weibull shape factors in the range 1.3 to 1.8.  The higher the shape factor, the greater the energy yield.  There is an inference that the lower shape factors are associated with complex terrains.  At some point I need to revisit the data and produce a better summary.

Next I looked at offshore data.  Onshore wind is fluid flow over a rough surface, the effects of which extend for a significant height.  In contrast, the fluid friction over water is much reduced.  In the areas between the tropical and polar circulations, the average wind speed might be in the range 6 - 10 m/s with wind speed increasing with poleward distance.  Often the Weibull shape factor is close to 2.0 allowing the use of the Rayleigh distribution (a special case of the Weibull distribution with the shape factor set to 2.0).  The greater energy yield offshore is offset by the higher cost of the installations necessary to capture it. Onshore wind turbines can be erected with general purpose equipment such cranes, diggers and lorries, offshore it is necessary to use specialist vessels for pile driving, lifting and cable laying which are both large and expensive. The nature of offshore structures is determined by the conditions in which they need to survive.  I had a brief career as a merchant seaman and have first hand experience of the violence of an ocean storm.

In addition to capturing temperature and dew point data, weather balloons also record wind speed and direction.  Unlike airports and buoys which usually report once an hour typically providing 8760 observations per year, an upper air sounding station might generate 200 - 300 observations per year for a given altitude.  At about 800m the flow of air is not influenced by the nature of the earth's surface and this known as the planetary boundary layer.  For North America and Europe, the average wind speed at 800m was often in excess of 10 m/s and the distribution similar to that for offshore locations.  I am intrigued by the concept of airborne wind turbines, machines which generate electricity can be summarised as being large chunks of metal, Doing this safely and economically is fascinating technical challenge.

Close to earth are personal weather stations.  For large scale installations turbines can be mounted on masts which gets them away from the turbulent zone close to the surface, but for small installations, once you get above a few metres from the ground, the cost of the mast becomes significant, not to mention the attitude of local residents.  Many PWS are located in urban or residential areas, they often suggest low average wind speeds, lots of turbulence and long periods of calm.

Whilst I'm sadly fond of software and databases, the hours spent with them were suggesting complexity.  I found two ways of exploring this.  The first was simply to cycle around the local coastal area with a wind speed meter.  Close to the coast the wind when blowing off the sea was smooth and similar to that reported by the local airfield.  In urban parts, it was weak and turbulent (however, destructive gusts can and do occur in such places).  On the surrounding ridges and hills, the wind speed had some relationship to that on the coast but was noticeably more turbulent.  Taking a kite on these expeditions made them more fun.  If you fly a kite people will smile at you and look happy whilst messing with an anemometer (or small model Savonius wind turbine)  is a solitary activity.

A variation on this theme is to observe the angle of trees.  In an area where the wind speeds are low, trees grow vertically, as the wind speed increases they take on a slant away from the direction of the prevailing wind, the countryside records the weather.

The second route was to look at the location of windmills.  During the 19th many windmills were constructed, mainly to grind corn but also for pumping, sawing timber and towards the end of the period a few were used for generating electricity.  The siting of a mill was critical to its economic success and therefore it is reasonable to assume that millwrights had a good knowledge of the interaction of wind and terrain.  I'm still working on this, but it is appears that ridge and plains were the favoured locations.   I'm still looking at this, but it appears that many early airfields were also build on shallow hills and ridge with the runways oriented along the direction of the prevailing wind, thus giving aircraft with low power/weight ratios compared to today's standards some assistance in getting aloft.

Wind is not constant and the energy available for conversion is proportional to the cube of its velocity, for example, wind blowing at 7.5 m/s represents approx 3.4 time more energy than at 5.0 m/s and at 10 m/s this increases to 8.0.  Wind energy arrives in "pulses" sometime separated by days or even weeks and subject to seasonal variation.

The old order changeth, yielding way to new

I was recently looking for a second hand PC power supply for a project which is so late I'm too embarrassed to talk about it.  Whilst walking the dog, I came across a box next to a wheelie bin, I knew it was not a PC, but it was probable that it would contain some sort of power supply, whilst it was not ideal it could save a ride into town.  When I got it home it revealed itself as a CD drive with SCSI connectors conveniently marked as having been acquired in 1993.  Against my better judgement, I powered it up with an energy meter in the line after which it drew a steady 10 watts.  From my experience, this type of device would mainly be used for installing software and performing system backups, when in use it might draw 20 - 30 watts, but only for as long as it takes to write a CD (which in 1993 could be quite a long time).  Back in the 90's a lot of computing was based on servers and local area networks (LANs), there were file servers, print servers, mail servers, database servers etc. etc. spread over one to many grey boxes depending on the size of the enterprise.  At that time I did not take much interest in energy consumption, however for a brief period, three of us worked in my house with a server and some PCs, suffice to say, the central heating was redundant.  Later we moved to offices with a server room which we also used for drying wet clothing.  To summarize, there was a lot of waste heat.

Raspberry Pi - consumption 3 - 5 watts

I'm currently messing with some energy management software which runs on a Raspberry Pi, this device has exceeded expectations, not least because of its energy consumption, I have not done any serious measurements, but I guess it takes something like 3 - 5 watts and nothing is warm to the touch.  The Pi uses a web server to output to my mobile phone.  Like the Pi, the phone is also good with energy.  An aging laptop and an LCD monitor complete my working environment and these are profligate in comparison with the phone and the Pi but even they don't compete with the central heating.

A computing peripheral from the past - Consumption 10 watts at idle.

Another element in computer energy us is the growth of the clouds.  Data centres use a lot of energy but they make it possible to share resources which have been optimised to minimize their energy consumption.  Servers in small offices used to be sized to meet the peak demand, but most of the time (including overnight and weekends) were just a convenient place to keep a mug of coffee warm.  For a few GB of data, cloud storage probably offers a better energy result than operating a dedicated in-house server

Whilst energy costs and footprint have been a factor in the increasing the efficiency of computing devices, equally important is that many applications, most notably the mobile phone won't work unless they are good at energy.

The doctrine of unforeseen circumstances now kicks in, I occasionally heat my work room with a coal fire, sometime augmented with wood I've picked up whilst walking the dog.

Generation and Conservation

The generation elements of a sustainable economy attract more attention than the things that use energy.  A couple of acquaintances have installed rooftop PV and this has been the subject of discussion amongst the neighbours with questions like "how much electricity to the generate", "how much money do you make" etc.  In contrast, my four LED light bulbs and newly acquired Raspberry Pi attract little or no interest.  I am old enough to realise that "do you want to see my LED" is not the best way to start a conversation.  In a more general sense, wind farms and solar parks get more column inches in the media than boiler controls and politicians are careful in the choice of language they use to talk about energy consumption.

With a little creativity its possible to determine the perception of any project.  My view is that wind and solar sources are complimentary.  Wind produces most energy during the winter and solar can be a cheap source of electricity in summer, but both are discontinuous sources and without low cost storage, require an equivalent fossil fuel backup, which means wind and solar capacity has to be matched with a flexible and responsive technology such as gas turbines.

This is an attempt to make the case for focusing on conservation.  There are many ways of looking at the numbers, hopefully this one is simple, albeit with some gross over simplifications.  Let's start with the assumption that one house in a hundred as rooftop PV and that the installation costs £5,000 and produces 2,500 kwh/year.  The owner of the PV panels recovers his/her/its costs from a feed-in tariff.  The panels produce most of their output a few hours either side of solar noon during the summer months, not much during the winter and none at night.

Peak demand for electricity is in early evening during the winter months and this can't be met directly by solar generation, at a guess, the peaks are largely met by gas fueled generators.

As the result of some policy as yet undefined, instead of one household investing £5,000, one hundred households each invest £50 in conservation technologies, in some respects this is more of a challenge than installing rooftop PV,  For my household selectively replacing four 20 watt CFl's with 5 watt LED has resulted in reducing consumption by about 50 kwh/year .  Extrapolating this to 100 households results in savings of 5,000 kwh.  More to the point, these savings take place at the time of peak demand, thus reducing the need for fossil fuel capacity.

The more overall demand is reduced, the easier it is to integrate sustainable sources into the energy economy.

Energy - A short family history

I've dipped into history for several posts and after some random research, a pattern seemed to be emerging.  I take the view that technology evolves and allows you to break with the past, however, the past delivered you to the present and you need to learn from it. I'm not advocating returning to coal fired ranges for cooking and horses for transport, but I do think that energy management which was once an integral part of daily life could be as effective in achieving sustainability as technology.  This very brief history is based on half remembered comments and Sunday mornings spent at car boot sales.

In the context of our family, the history of energy can be summarised in three periods, from approximately 1850 to end of the Great War, the interwar period and the Second World War, then the post war period to the end of the 20th century.

My mothers grandparents or great grandparents "left the land", making some assumptions about age, this must have taken place between 1850 and 1870.  It is possible that they worked on the land with horses and heated their homes and cooked their food with wood fires.  Apart from the railways, most transport involved a horse in some way or another.  You provide a modern vehicle with some form of ID, then press a button and drive off but a horse requires daily maintenance and preparation for a journey.  Unlike a car some of the emissions from a horse can be recycled.  The wood for fires had to be collected, cut up and dried.  Wood is only a good fuel if it is dry, thus if you want a warm winter you need to gather fuel in summer.  At the start of the 20th century, my mother's family were settled in a Yorkshire town, still working with horses, but now delivering timber to building sites.  The homes were now heated by coal fires and lit with oil lamps and gas mantles.  The provision of heating and lighting involved a lot of cleaning for the women of the household, tasks such as black leading the range, cleaning sooty oil lamps and laying fires made them effective saleswomen for the gas and electricity companies in the interwar years.  Money and time had to be planned, fires were only lit when someone was in a room, meals had to be planned around the range.  The warmth of the range made the kitchen the family centre in many homes.  When the war came, the men and horses went and those that returned were not in good shape and that was the end of the family's involvement with horses.

The interwar period was one of change.  Coal was still the dominant fuel for industry and transportation.  My wife's family were mining engineers and many of mine worked on the railways.  My mother;s cousin drove steam trains for the L.N.E.R.  He had started as a "boy", then become a fireman, shovelling the coal into the engine's firebox and finally a mainline driver.  I only knew him late in life, he felt he had had a good life, but made it clear that it had been a hard one.  A fireman's day started well before an engine left the sheds, the first job was to rake out the ashes from the firebox, shovel coal from the tender/coal box and then raise steam, all this is hard physical work which often started at 04:00 or earlier.  In addition to maintaining the timetable there were often restrictions on the amount of coal available, it was not unknown to scavenge wood when the opportunity presented itself.  Towards the end of his career, electric trains were being introduced and these were popular with many drivers.  I had a brief experience of steam winches in 1970 and quickly became aware that it was necessary to have a working knowledge of engineering to maintain and operate them, in contrast electric machines were relatively simple to use.

Whilst gas had been used for cooking and many homes used electricity, either from a power station or from lead acid accumulators before the outbreak of war in 1914, it was in the 1920s that these things started to become accessible to a large part of the population.  These changed the nature of the household energy economy and improved the life of women.  Coal remained the dominant fuel for heating, but cooking an lighting now involved flicking a switch rather than shovelling and cleaning.  Initially, electricity was just used for lighting, but new uses were soon found, in our family vacuum cleaners were popular, followed closely by electric irons.

Increasing numbers of young men bought motor cycles, some realising that a woman wearing a skirt would not ride pillion attached a side car and a few raffish fellows acquired three wheeled cars driven by a vee twin mounted on the front.  As the second world war approached, some of the better off members of the family had acquired a small car.  Even amongst the non-technical members of that generation there was basic familiarity with the petrol engine acquired out of necessity, most knew the mantra of compression, spark and petrol.  Cars at that time were equipped with starting handles which provided an opportunity for showing off and frequent humiliation.  This maybe an urban myth, but it was widely held that a woman's stocking could be used as a temporary fix for a broken fan belt, this was not a good chat up line, not least because stockings were expensive.  The efficiency of petrol engines was not high, my perception is that the cost of production (and thus selling price) was more important than efficiency, 30 miles per gallon seemed to be the expectation.  Many engines of that period had side valves and were made of cast iron.

Domestic energy consumption steadily increased during the interwar period, probably the rate of increase was slowed by the depression of the late 20s and early 30s.  Unit prices also started to fall.  The graph below shows the electricity consumption of one family from 1926 to 1948.

Typical consumption was between 500 and 700 kwh/year, today, the average consumption of a modern household is around 3,500 kwh.  The austerity imposed by the second world war is clearly visible in the graph which shows annual consumption falling to less than 400 kwh.

The first decade of the post war period was a continuation trends established in the pre war era, there was full employment and a demand for consumer goods and the electricity to power them, some pundits were advocating the merits of an all-electric home with none of the mess of coal fires.

The term "dash-for-gas" gets regular outings, but it is a good description of the energy sector towards the end of the 60s and early 70's when the discovery of large gas reserves in the Southern North Sea and the subsequent displacement of "town gas" which was manufactured from coal.  For the most part this change of fuel required only minor modifications to appliances, however somebody made a pledge that all appliances would be adapted and every so often the papers would feature a story about an unlikely object being fueled by North Sea Gas, fridges and radios attracted a lot of attention.  For most households, the advent of gas central heating heralded a new age.  The coal and ash buckets were replaced by an electrical/mechanical timer which ensured that the house was warm when the family woke up and there was bath water in the evening and it was cheap.  By the end of the 70's gas had displaced coal as a fuel for domestic heating.  This was not a bad thing, but the next generation grew up when energy management was delegated to a time switch and at a time when for many people (but not all) the percentage of household income spent on gas and electricity was falling as wages generally increased.

At the start of this century, energy prices have risen and there are concerns about the environmental impact of fossil fuel consumption.  It's an exaggeration to say that many households have found this difficult to cope with because of timer switches and thermostats located in drafty halls, but its a reasonable hypothesis that these contribute to high energy bills.  There are some signs of change, predictably, the smart phone is part of this and there are some systems which allow heating systems to be controlled remotely and portable  thermostats.  The benefits of these systems may be that they encourage energy management.

Soil and Satellites

Recently I've started exploring satellite data, mainly to learn about the distribution of clouds.  The NASA Earth Observation site (NEO) is a great resource learning about the atmosphere, solar insolation, land cover and much else (there is a link at the bottom of the page).  The site has a large number of thematic world maps with various time and space resolutions.  In addition, the data behind the maps can be downloaded making it possible to extract data for a specified tile containing data for an area of interest.

For a couple of years I have been collecting soil temperatures in my back yard, I thought it would be interesting to compare surface temperatures as measured by the Terra and Aqua satellites with my observations for 2013.  The results are shown in the graph below.

Whilst there is reasonable agreement between the two datasets, it is not a like-for-like comparison.  The most obvious difference is that the NEO data comes from a sophisticated spacecraft with massive scientific backup.  My data is derived from a hole in the ground which is protected by an empty dog food tin.  The satellite data is an "average" for a 0.1 by 0.1 degree tile (very approx. 10 by 10 km), the one which contains my back yard contains a wide range of surfaces including urban, agriculture and woodland.  The satellite builds up a picture of the Earth's surface from a series of scans rather than constant monitoring and only collects some types of data on clear days.

My hole in the ground was located to avoid the mains water supply and be accessible when when crops a growing, this could be described as a random suburban setting.  The temperature readings are usually collected around sunset on Sundays.  Soil temperature varies considerably during the day and night, the extremes take place when the sky is clear.  In summer the noon temperature can reach 30 deg. C, and in winter under a clear night sky, it can fall well below zero.  The graph below shows the variation during a spring day.  The thermal turbulence is greatest at the surface (measurements taken at 0.1m).  The temperature at 1.0m approximates to the average at 0.1m.

The relationship between surface and air temperature is complex, I have yet to investigate this but it seems that the average soil temp approximates to the average air temperature, however the variations in surface soil temperature are greater than those of the air above.

Reference:

NEO Site

Soil Temperature - A Day in the Life Of

Soil Temperature

My daughter and the energy monster

You wait a lifetime for a reference to draft excluders then two come along in a single week.  To be strictly correct, my daughters use of a discarded pair of tights is a temporary fix for a broken roof window.

The second was in an ad for an energy company, in which two cute children make an energy monster out of old tights and newspaper and save the family lots of money and blocking up gaps under doors.  I am not wholly convinced by this scheme, its a nice thing to do, but I doubt that it will be visible on the energy bills of a home with central heating.  However, it does make a connection between energy management and  home economics.

When houses were heated with coal fires drafts were a problem, in order to burn, a coal fire sucks in cold air from between gaps under doors, badly fitting window and from under the floor and some place that no one ever managed to find.  In this situation draft excluders did make a difference.  They turn up a car boot sales where they often resemble the discarded limb of a diseased pantomime horse.  they may be stuffed with vintage stockings, historic newspaper or just something old and disgusting.

I should be writing a paper, working on software, but I am renovating my house.  Whilst its easy to lounge around thinking great thoughts, its also good to contemplate why one's feet are cold.  On a winter's evening we draw the curtains, and turn the central heating on for an hour or so and then light a fire in the living room for warmth during the evening.  The previous owner installed the radiators in such a way that curtains masked them off from the room.  As 100 years of interior decorating is scraped off the walls, one task is to replace and relocate the radiators such that they approximately four inches from the wall.  Thus when the curtains are drawn, they form a barrier between the radiator and the window rather than a union.

I won't know how effective this has been until the coming winter departs.  As part of a major overhaul, its not difficult to add this task to the list, it might not be so attractive as an isolated project.  The more I mess with domestic energy, sustainability, the more convince I am becoming that a lot of small things add up to something worthwhile, so maybe I was wrong to dismiss the energy monster.

Town Ash

Once I knew little about town ash, then four weeks ago I found that I was the proud owner of quarter of ton of the stuff.  I mentioned this discovery to several people, only to find that ash is deeply rooted in folk memory and I became ashamed of my ignorance.

Back in the 19th century and early 20th, the energy economy was for all practical purposes, coal.  Unlike today where coal is burnt in a relatively small number of locations, most of which are power stations, coal was burnt in small quantities in millions of urban locations.  Just look to the skyline in most English cities and you will see a chimney of some sort.  Most homes had one or more open fires and a range for cooking, all of which were producing ash.  Sometimes ash was separated from other household rubbish and collected separately, sometimes the dustin was the last resting place of all of a household's filth.  Ash as domestic waste lives on, in 2004 the council supplied me with a plastic wheelie bin which is embossed with the slogan "No Hot Ashes".

Finding a use for this stuff was making a virtue of necessity.  My ten sacks of ash had been used to provide support during the construction of  brick wall, one of the faces of which was sloping.  After a century, the ash had become soil and plant life had caused the structure to degrade requiring a rebuild.  Ash had also been used in the mortar and this made it easy to reclaim the bricks, however, they were of poor quality and I opted to use new ones.  The originals were FreeCycled and may now be part of a garden path.  The man who collected them told me that ash was frequently used in Victorian civil engineering as a fill for canal and railway embankments.

What was once Victorian rubbish can now be collectable history and ancient tips are sought out by bottle and pot lid collectors.  On learning this decided to sieve my ash before disposing of it.  Whilst there were no great discoveries other than an almost complete egg cup, several bits of broken clay pipe and fragments of jars as few of which had writing.  The pile of fine ash from this exercise can be used as a soil improver, as there were many many species of plant established in the wall, there may be some truth in this.

A few fragments have various combinations of letters which suggest they are from local companies suggesting that the ash was also local.

As was also used in brick making, having seen a lot of broken bricks recently, I would suggest that bricks with a high ash content are of low quality, but that might just be the result of a small sample.  Ash is also known as "breeze", this has been used in conjunction with cement to to produce a large building block known as a Breeze Block.

Clinker, which is the lumpier bits of ash was often used as a base for concrete used in step, pathways and standing areas:

An allotment holder told me that ash was often dug in allotments where the soil contained a lot of clay, this made it lighter and prevented it from becoming waterlogged.   One use attracts mixed feelings, sometime back a local resident disposed of his ash by spreading it on a rough, steep track that ran by his house, this made walking a lot easier, but, for regular users it required additional shoe cleaning.  As I work from home, my dress code does not require me to have clean shoes, so I was grateful for his efforts.

Finding uses for ash was a form of recycling, in many towns it is normal to separate items that be recycled, e.g. bottle, tins, paper, plastic etc. from material which can only be disposed of in landfill or incinerators.

Postscript - 03-Jan-2015

Recently I was walking around the northern part of Brighton where many roads are build on sloping ground and where retaining walls are common.  One such wall was dark grey with fragments of pottery visible on the surface (I have a bucket full of similar stuff).  I'm guessing that this wall was in part a mixture of town ash and cement:

Why is broken pottery such a common feature of the ground surrounding Victorian and Edwardian buildings?

Storage - A personal survey

Having made frequent references to storage in this blog, I thought it would be good to read around the subject, this post is more or less a list of links to Wikipedia articles.  The list is neither complete or comprehensive.  Whilst randomly clicking around, I was intrigued by the number of references to submarines and electric fork lift trucks.  Whilst these appear to be diverse applications, both make use of stored energy and both have well developed infrastructures to support their operations.  Maybe the starting point of a sustainable energy economy is a submarine, maybe this was the origin the line in the Beatles song which goes "We all live in a yellow submarine".  Storage is the key technology in a sustainable energy economy, generation is the most visible element and attracts most of the attention, but it is storage that bridges the gap between the regular pattern of daily life and the shifting sun and fickle wind.

Traditionally, system efficiency has been principal method used by engineers to assess performance.  Whilst it is not unimportant in storage systems, in the authors opinion it is the unit cost of energy as perceived by the end consumer which is the most important measure.

Batteries

Batteries are the most familiar form of storage.  A gross over simplification would be to divide them into two categories defined by weight, the heavy lead acid form which has been in use for a century of more and the lightweight varieties such as NiMH (Nickel Metal Hydride), Ni Cd (Nickel Cadmium), LI (Lithium Ion).  Lead Acid accumulators have a long history of use in domestic energy storage providing the energy for lighting, door bells and valve radios.  If operated conservatively they have a long life and can provide a few kwh for domestic use and more than 1,000 kwh for submarines.  If used in vehicles, the result is the milk float, the high energy density of LI batteries makes it possible to design sleek and elegant high performance vehicles such as the Tesla Model S which has LI batteries with capacities of 60 - 85 kwh.  The life of a battery is a function of the way that it is used, high charge and discharge rates will shorten the life of most types of battery, the depth of discharge is also a factor.

Compressed Air

Compressed air motors have long been used to provide power where any form of combustion is undesirable, for example in mines or where atmospheric oxygen is not available.  Compressed air powered many torpedoes in both the First and Second World Wars.  Storage schemes using compressed air range from small pneumatic accumulators to utility scale projects based on underground caverns. Large marine diesel engines often use compressed air for starting.  At the time of writing, it seems that most of the utility scale projects are still at the proposed or planning stage.  Compressed air storage based on underground caverns maybe less visible than the major civil engineering works required for pumped water systems.

Pumped Water Storage

Pumped water storage is a utility scale technology, often based on worked out quarries and large dams.  The system consists two reservoirs, an upper one and a lower one.  The energy to be stored is used to pump water from the lower reservoir to the upper reservoir.  That energy is reclaimed by letting the water flow back to the lower reservoir through turbines which power generators.  Often the machinery is in the form of units which can  work as either motor/pump sets or turbine/generators. Pumped water is currently the most common utility scale storage technology.

Thermal Storage

Thermal storage includes several diverse range of technologies.  At the domestic level it includes night storage heaters, these use off-peak electricity to heat up a mass of bricks or water, as these cool during the day they provide space heating.  Domestic hot water systems often incorporate an insulated tank, this can be heated using off-peak electricity or solar thermal devices in a suitable climate so that hot water is available for an early evening bath.  At the utility scale, heat from large solar concentrators has been used to create a reservoir of molten salt (or similar substance).  The heat stored in this material can then be used to create steam for use in a conventional steam turbine generator.  The Wikipedia article has a link to an article describing a solar basede Seasonal Thermal Storage System in Canada.

Hydrogen

Whilst hydrogen is not a dedicated storage technology as such, it can be produced by sustainable sources, for example by electrolysis from wind generated electricity.  It is a versatile fuel and can be used to generate electricity directly in fuel cells and as fuel for reciprocating engines which are adaptions of those used in automotive applications.  The German Type 212 submarine uses a form of hydrogen fuel cell to achieve better performance and endurance than a conventional diesel electric vessel.  Earlier this year Toyota announced the launch of fuel cell based car.

Flywheels

Flywheels have long been used for storing energy for very short periods of time, for example smoothing out the torque produced by reciprocating internal combustion engines.  It maybe an urban myth, but success of the Citroen 2CV (the famous "tin snail") has been said to be due to a large flywheel which made it well suited to undulating roads of rural France.   Flywheels form the basis for for some recuperative braking systems, these capture a vehicle's kinetic energy as it brakes and then restore it to the drive train on the next acceleration.  This type of system has been used in F1 racing cars.  The flywheel is an attractive energy storage device, it may have a longer life expectancy than chemical based systems.  Despite its apparent simplicity, large systems are heavy, high rotational speed systems which present some design challenges, however, it seems that these are been overcome.

Links

Batteries
Milk Float
Tesla
Compressed Air Storage
Pumped Water Storage
Thermal
Type 212 Submarine
Hydrogen Storage
Hydrogen Fuelled Vehicles
Flywheel Energy Storage
Regenerative Braking

Cars don't do very much

The street I live in is for all practical purposes, the car park of the local railway station.   During the day, the street is home to a flock of thirty to forty cars, at weekends they may roam the parking lots of the town or journey to the outlying supermarkets and once a year they take flight to Cornwall or the Lake District.  Most of the time they do nothing.

I  have often gazed at these vehicles and wondered if things could be different.  The following will not survive any form of analysis or review, but it passed the time.

There are no electric vehicles parked in the street, but there are two or three hybrids.  I'm not convinced by hybrids, my understanding is that they attain a high level of fuel efficiency by using an electric motor and battery to optimise the usage of a petrol engine.  This is achieved at the expense of weight and complexity, if I were to consider buying a new car I would opt for something small and light with a simple but efficient drive train or something electric if it cost the same.  Hybrids and electric vehicles have batteries and that's what makes them interesting.

A short walk to the north takes you to a couple of oddly sited charging points for electric vehicles.  If these were located closer to the station an owner of an electric vehicle could leave it to charge during the day.

A short stroll to east takes you to a park which on a clear day gives you a distant view of the location of a planned offshore wind farm.  I am an enthusiast for wind and solar energy, but I perceive them as weather dependent sources which stall with clouds and calm which require some form of buffer storage to even out the gaps between supply and demand.

In many homes, the commuter is away all day at work and children are at school so apart from an over enthusiastic robotic vacuum cleaners, domestic electricity consumption is relatively low during the day. It is in the evening that the home wakes up, lights go on, meals are cooked and hair is straightened.

In an integrated world, the car has found something to do when otherwise it would be idle, during the day it has been harvesting electricity from an offshore wind farm, in the evening when it arrives home some of that energy is used to meet its owner's domestic needs.  The technology used to get solar panels to feed into the grid, is the same as that needed to use energy stored in the car's battery.  In this scenario one battery is contributing to the domestic energy economy and transport.

Its not difficult to pick holes in this scheme and one bit which does need some innovation is the tariff under which this would operate.  Ideally this should take account of the sustainable energy use and offer an incentive maximise its use.  There is potential conflict with HMRC, petrol and diesel are heavily taxed, whilst electricity for automotive use is not.

Footnote

This post was originally published in 2014, since then the Rampion wind farm has been completed and the use of the two charging points referred to above has increased.  When they were first installed, they were rarely used, I've passed by them a few times recently and more often then not at least one vehicle is connected.

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?