The smart heating controls experience

2018/19 was our first winter with smart heating controls.  This was a positive experience with the benefits coming in two forms.  First, we used less gas and our supplier has amended the direct debit to take less money from our account each month and secondly we used our heating system in a different way.


The reduction in gas consumption was around 20%.  The savings could have been greater.  We currently have a non-modulating boiler which is not fitted with a bypass valve, for this reason the kitchen radiator and bathroom towel rail retain their conventional valves which are always left on  to provide a thermal dump when all the motorised valves are closed.  This summer the boiler will be replaced and a bypass valve fitted, then two more radiator controls will be added, when this work is complete I expect to get some additional savings.  Our ageing dog has arthritis and for his benefit we put his bed in a room with a radiator controller set to 16 deg. C (the boiler also lives in this room so so its always a couple of degrees warmer than the temperature reported by the radiator controller.  Without the new controls either he would have been cold or we would have spent a lot of money on gas.

Whilst the financial savings are appreciated, we got better value for the gas we were buying.  Because the temperature in each room could be set individually we just heated the rooms in use, this meant we were much more comfortable to turn the heating on.  Previously turning the heating on meant heating ten radiators, now, depending on who is home only one to four radiators are on at any given time, which radiators are on depends on the time of day, in the morning it is the bedrooms, during the day it is my work room and the sitting room in the evening.  This has made our Edwardian semi, which in every other respect is a thermal disaster, comfortable to live in.

Three years ago our old central heating system had ceased to function, parts of it were thirty to forty years old, the pipes and radiators were clogged and in places blocked with a mess of rust and limescale.  Also, the system had grown by additions of pipework that was wrapped around old gas pipes, electrical conduits and some ancient ironwork.  Starting again seemed the be best option.  I did the work myself, the downside was that whilst I had some workshop training in the distant past, I’m not a qualified/experienced plumber, the upside was that I had the leisure to remove the obstructions which prevented clean pipe runs.  I attempted to mitigate my lack of experience by pressure testing the system after making each pipe joint.

Motorised valves were always part of the plan.  It seemed a good idea to mount the controllers on the top left of the radiator which placed them at waist height, thus adjustments can be made without having to kneel on the floor.  If controls are inaccessible, i.e. at floor level they will be ignored.  At any given time it is probable that some radiators will be off, in an attempt ensure adequate circulation, each radiator is served by 22mm flow and return pipes (the tails being 15mm) and the original constant speed pump was replaced with a smarter one.



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An overcast sky from above

This picture was taken just before sunrise on an early morning flight from London to Glasgow in October 2011.  Before departure, the weather on the ground was overcast,  damp, cold and windy and something you would not want to photograph, but at 30,000 feet, the view from the window might have inspired Turner.


Weather reports suggest that this was a layer of stratus a few thousand feet thick.  Stratus is a feature of the sky over England during the winter months, the diagram below shows how the nature of cloud changes during the year.


In winter, low, broken or overcast skies full of stratus are common, in summer these give way to scattered and broken cumulus and some clear skies.

The effect of a thick overcast sky on solar devices on the ground include:

  • Significant attenuation of solar radiation caused by a combination of reflection and absorption, often this is less than 20% of the level that would be expected from a clear, dry sky for the same value of air mass.
  • There is no direct sunlight (i.e. no shadows) and all the radiation is diffuse.
  • Often the density of the radiation is equal from across the sky.  Some experiments suggest that the yield of PV panels might be higher under an overcast sky if mounted horizontally, rather than sloping to face the sun.

These effects are exaggerated because thick overcast skies occur in winter when the Sun is low in the sky (air mass around 4.0 at solar noon).

Note: This is an edited version of a post which was originally posted on in 2015.


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Art and energy

In 2017 Brighton Museum is staged an exhibition of the work of John Constable which he produced whilst living in the town from 1824 to 1828.  I went because it’s a form and period of painting I’m attracted to.  The space was low key and did not shout “great art” making it possible to appreciate the pictures for what they are, sensitive and imaginative depictions of Brighton and the surrounding countryside at the start of it’s period of expansion.

What I did not expect was an insight into the energy economy of the town before the arrival of the railways.  There are several pictures of beached collier brigs.  After 1840 most Brighton and Hove’s coal supply was came from the harbour at Shoreham by rail, but before that a lot of it was landed on the beach and taken to buyers in the town by horse and cart.


The collier brigs were two masted vessels of 100 – 300 tons with a length of between 70 and 90 feet and a small crew, maybe 6 – 10 men.  They mostly worked out of the Tyne taking a cargo of coal outward and returning home in ballast.  Some vessels also carried passengers between the North and London, before the railways this might have been preferable to several days in a coach travelling along rutted roads, at least in fine weather.  Navigational equipment was probably the master’s experience and a compass.

At coastal towns like Brighton and Hove which did not have port facilities, the brig was run on to the beach and the cargo unloaded into horse drawn carts using local labour.  When the vessel was empty she was re-floated on the rising tide.  The price realised for the cargo would have depended on the season, the weather and before 1815 the trade could be disrupted by French privateers, this threat may have been used to hike the price.

Coal landed on the beach within the Brighton parish boundaries was subject to tax.  This explains the location of the Brighton Gas works (1819) just beyond the eastern parish boundary at Black Rock.  Hove did not levy coal duties and their Gas works (1825) was at the extreme west of the town, possibly because nobody thought that fashionable housing would ever extend that far.   Brighton’s coal tax was abolished in 1887 before then it had been levied at 2s 6d/ton.  Coal merchants quoted two prices one for delivery in Brighton and a lower one for Hove.  From 1820 to 1880 gas was used for street lighting and in  the posher town houses.  After the establishment of electric light companies in Brighton and Hove, gas lighting was displaced, initially by arc lamps, then by incandescent bulbs.

At the turn of the century the demand for coal in Brighton and Hove had greatly expanded.  In 1928 there were four railway goods yards, each of which acted as a base for coal merchants, some of these operated nationally, others were local family businesses.  Going west to east, the goods yards were located at Sackville Road/New Town Road (Hove), Holland Road (Hove), Cheapside (Brighton) and Kemp Town (Brighton) and Lewes Road.  With the exception of Cheapside which is close to the main Brighton station, these yards are now industrial estates doing amongst other things, serving the local building trade.

By the 1880s, the railway’s coal distribution network was evolving at the same time as the market for coal for electricity generation emerging.  Brighton’s first power stations were close to North Road and supplied from the Cheapside yard.  Hove’s was at Holland road where it had it’s own siding for coal deliveries.  At the end of the 19th century, the demand for electricity was growing and city centre locations for industrial plant was neither desirable or practical.    Brighton built a new power station at Shoreham harbour, close to the gas works which had already relocated, both the gas and electricity works were now supplied directly from the sea by steam colliers.

Industry attracts fewer artists and poets than traditional landscapes, seascapes and portraits, but there is one reference in John Masefield’s “Cargoes” which is relevant.  I suspect generations of English teachers have hoped to inspire a love of words and rhythm with this, the last verse is:

Dirty British coaster with a salt-caked smoke stack,
Butting through the Channel in the mad March days,
With a cargo of Tyne coal,
Road-rails, pig-lead,
Firewood, iron-ware, and cheap tin trays.

I’ve always been troubled by the “salt caked smoke stack”, maybe I’m too literal, but the verse does invoke the rhythm of a reciprocating steam engine.

In 2015 construction of the offshore Rampion wind farm commenced, the turbines are visible from the seafront, it will be interesting to see if they become a subject for artists.

Note: This is an edited an corrected version of a post which first appeared on in April 2017.

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The life cycle of fuels

Fuels have life cycles.  The stages of the classic life cycle are growth, maturity and decline.  For some fuels like wood, the length of the cycle is measured in millennia, that of coal looks like it might be centuries and calcium carbide as a lamp fuel probably decades.

My understanding of carbide lamps is that they were developed for cars and motorbikes at the very end of the 19th century.  Whilst electric incandescent lamps which could be powered by a lead-acid accumulator were available, they were not bright enough to allow safe driving.  The attraction of acetylene is that it burns at a high temperature and produces a bright light.  The gas was generated by the action of water on calcium carbide, the lamps were so constructed that a reservoir of water dripped on calcium carbide which was then burnt in a lamp with a reflector.  The brightness of the lamp was controlled by adjusting the water flow, as the gas was generated, the carbide turned to slaked lime.  “Carbide” was sold in garages along with petrol and oil during the 1920’s, but as automotive electrics improved and effective headlamps which could be controlled by a switch became a standard fitting, carbide lamps were largely displaced by the 1930s.  In Brighton in 1912 more than 20 garages were licensed to sell calcium carbide and the stock levels permitted by these licenses was 500 pounds, thus there was a lot of this stuff being used. Gas Bicycle Lamp_0.jpg

Kerosene (a.k.a. paraffin) as a domestic fuel had a somewhat longer life cycle, it was used for lighting and cooking in late 19th century.  In the era of solid fuel ranges. it facilitated cooking without first having to light a coal fire, although many found the smell unattractive.  Paraffin heaters were widely used well into 1970s and many people remember the Esso’s adaption of “the smoke gets in your eyes” for their TV adverts.  Paraffin heaters were generally displaced by low cost gas central heating in the 1970s.

The same pattern of growth, maturity and decline is apparent in the UK coal consumption.  A spokesman for OPEC once commented that the UK did not run out of coal, they just stopped using it.  In the latter part of the 19th century coal consumption grew as industry, railways, gas production and other applications expanded.  It remained constant for approximately half a century until the 1970’s.  During this time the economy was growing, but technology was evolving which allowed coal to be used more efficiently.  In 1890, electrical power generation had a thermal efficiency well below 5%, by 1970, this was approaching 40%.  The boilers used in the early power stations operated around 150 psi, by 1945 some were operating at 675 psi, the rising temperatures and pressures resulted in higher operating efficiencies which in turn acted to stem the growth of coal.

In the 1960, natural gas (methane) from the North Started to displace coal in the UK as a domestic and industrial fuel.


The displacement of coal by natural gas is apparent in the graph below.  Starting around 1830, many towns acquired a gas works which was either privately or municipally owned, in the early years the principal use was for lighting, but cooking, heating and industrial use increased.  Between 1900 and 1930, electricity, also generated from coal, displaced gas for lighting.    The availability of North Sea gas bought about the extinction of the coal gas works in less than a decade.


Gas turbine power stations, have steadily displaced coal fired steam technology, a process which accelerated in the 21st century as concerns over the environmental effects of coal grew.

The energy mix is constantly changes, the driving force is technology, over two centuries it has included coal, wind, solar and nuclear (after 50 years is this an old technology) and there have been many evolutions within each.  There is a lot of evolving technology, offshore wind and electrical storage maybe the key elements.  Several cities are talking about petrol or diesel vehicles and only allowing electrical ones, so more change can be expected.


The advert for calcium carbide was downloaded from from website of the Smithsonian Institute.


This post is an edited version of one which first appeared on in January 2017.

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Exploring the wind

When I first became interested in sustainable energy, my first thoughts were “how much wind and solar energy is available.  A large chunk of my life has been spent poking around data sets 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.


The starting point was a sample of Metar and similar weather reports which were reduced to histograms which in turn were used to estimate the parameters of a Weibull distribution.  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 lower.  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 construction 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 chunks of iron, Doing this safely and economically is fascinating technical challenge.

Closer 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 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 built 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.



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Clear Sky Fraction

I live in a temperate maritime climate (i.e. the south coast of England) where clouds in various forms are frequently present in the sky.  Some simple experiments using a very small solar panel suggested that clouds have a significant effect on the performance of solar devices.  On a clear summer day, the global horizontal irradiance (GHI) at solar noon can be close to 1000 watts/m2, a few days later when the sky is overcast this can fall to less than 200 watts/m2.  In winter, the higher frequency of occurrence of clouds further increases the overall attenuating effect.  Also, the nature of the irradiance changes, under a clear sky the diffuse fraction might be around 15% with, under an overcast cloud sky, the diffuse fraction rises to 100% and there is no direct beam irradiance.  I wanted to attempt to quantify the attenuating effect of clouds one possibility is a statistic called the clear sky fraction (CSF).

Slot 0 / Standard

CSF is defined as the ratio of observed GHI under a cloud sky, to the estimated GHI under a clear sky (i.e.if the clouds were not present in the sky).


Unlike wind whose velocity can be more-or-less constant over several hours, solar irradiance is constantly changing, it is close to zero at sunrise and sunset and at a maximum around solar noon.  This makes it desirable to use a ratio which is independent of Sun-Earth geometry. The principal input for models of solar irradiance is air mass (AM) which is a ratio describing the amount of atmosphere the Sun’s rays most pass before reaching the Earth’s surface.  At solar noon close to the equator, the value of air mass is close to 1, whilst it is approximately 15 around sunrise and sunset in the temperate latitudes during the summer.  Based on observations in the south east of England, the author suggests that the “economic” range of air mass values is in the range 1 to 6.  At an air mass values of 6, the zenith angle is approx. 75 degrees (corresponding to an altitude of 15 degrees).  Depending on the terrain, when the sun is low in the sky, the shadow of hills, trees, buildings etc. effect the irradiance up a flat surface.  Experience suggests that within the range 1 to 6, CSF is more of less independent of air mass.

Horizontal irradiance was chosen because of the importance of diffuse irradiance under a cloud sky. Under a thick overcast sky there is no direct beam element to the irradiance which is all diffuse and is evenly distributed around the hemisphere of the sky.  Whilst it would be more convenient to consider a sloping surface (which is the normal way of mounding most solar devices), this would not account  for all the diffuse irradiance.  Also, GHI is the most commonly collected form of solar irradiance data.

A problem in calculating CSF is the choice of method for estimating the clear sky irradiance.  There are two options.  The simplest is to use some form of model, many of these use atmospheric data such as water column and aerosol optical density and if this data is available, are capable of producing good estimates of direct and diffuse irradiance, the downside of these models is that detailed atmospheric data may not be available for the location where the observations are being made.  An alternative is to use observations of clear sky irradiance at the chosen location and the correlate this with air mass.  Either approach has a degree of uncertainty associated with it, not least of which is that whilst the reflection and absorption of clouds will be the dominant atmospheric effect, others such as moisture content will also have an impact.

In the past I have messed with various types of model in an attempt to produce a cloud sky model, whilst this process has been instructive, it can only be described as work in progress.

Note: This is an edited version of a post which was first published on in September 2015.

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Off-grid in 1911

This is a letter to the editor of “The Model Engineer and Electrician” which appeared on 29-Jun-1911.  It is in two parts, the first gives a description of the use of engines in farming and the second is a discussion of the use of lead-acid accumulators to provide domestic lighting.  I’ve edited the text slightly and illustrated it with adverts taken from the same magazine.

The prices in the adverts are in “old money” i.e. pound, shillings and pence.  One pound in 1911 is very roughly the equivalent of £95 today.  The output of bulbs described in the adverts is given in candle power, this is not directly comparable with the lumen ratings  used today, but a very rough comparison might be that 1 candle power is equivalent to 10 lumens (this is a guess).

The business of up-to-date farming needs, in addition to much other knowledge, a good general knowledge of engineering and mechanics. Labour saving machinery is continually being introduced on the farm, and the success or failure of this machinery is largely dependent on the way it is looked after. To illustrate the usefulness of model engineering, I may say, as a practical farmer, that the number of times that serious loss of time has occurred through the breakdown of machinery would have been a very small one had I practised model engineering as a hobby in my younger days.  Such simple things may hinder a gang of men at harvest time, such as the thread worn from a pin, the breaking of a spring; and this when delay may mean the loss of a crop.


Years ago farmers used to do all their chaff-cutting, root-pulping, etc., by hand and used to send their corn to the local mill to be ground. Now, all up-to-date farmers have an oil engine, motor engine or steam engine to do the work and the latest idea is to have an engine which will do all the pulping, grinding, etc., threshing, and haul the implements on the land. Trials were held last year by the R. A.S.E. to test such motors, and to the surprise of many, a steam engine won. The ordinary oil engine is generally used on farms; but the petrol motor engine being largely offered the market.  In my own case, I use a motor engine, one that starts on petrol and works on paraffin, and I think this is the type that will be the greater favourite, because duty-free petrol at 11d (approx. £1.00/litre). is much dearer than paraffin at 4d (approx. £0.35/litre).   I am afraid, however, that as long as motor engines are electrically ignited, they will never be so popular with the farmer as the ordinary oil engines, which have not accumulators to run down, plugs to soot up, contact-makers to get worn, and the other little troubles with which the busy farmer would perhaps soon get out of patience.


Personally, however, I would not exchange my little motor engine of  3 to 4 bhp for the best ordinary oil engine. It is so easily started, and can be used if only a bushel of corn or a bag of chaff is wanted. It is on wheels, we keep it in the barn in the winter and in a sort of workshop close to the house in the summer time, where we saw wood for fires, also for making any rough articles which may be required. Whilst the engine is doing this work, from a second pulley a small dynamo is driven which charges several 4-volt accumulators which are used for lighting parts of the house and buildings.


These lights are very handy indeed, in fact, I have been so impressed with this 4-volt lighting that I am thinking of putting it all over the house. In the stables it is particularly useful.  as we find a small 2 or 4 c.-p. lamp is ample for a 3-stall stable; in fact, it gives a much better light than a lantern with a smoked globe.  About the house, too, In the pantry, cellar, dairy, bathroom, back-kitchen, etc., a 2 or 4 c.-p. gives ample light for the purpose for which it is required. In small bedrooms, too, it is ample for a man; but, needless to say, a lady would require an additional light at the looking-glass.


What I like about 4-volt lighting is that I can do the wiring myself, and feel pretty safe a fire won’t be caused, though I am aware a short circuit close to an accumulator would possibly cause a fire if no fuse was in circuit.  Another thing is that it is easy to get 4-volt portable accumulators.   Then, if I went in for 25-volt lighting, It would all have to be done from one stationary battery, and it would be a big business laying the wires under roadways, etc. and cost a good deal. As It I have one accumulator for bedrooms, etc. another for pantry, etc. another for stables, and another for cow houses etc. It hinders, rather, connecting up for charging and redistributing the accumulators again; but It is very little trouble when done regularly.

Note – This is an edited version of a post which was published on in April 2016.

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