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.