Energy Management - An Edwardian View

Technology often implies a system with sensors feeding some form of computer running highly developed software tuned to make make the best possible decision which is then relayed to a smartphone.  These things did not exist in 1901 when my house was built and I'm now in the process of renovating, in practice this means peeling back a century of things that seemed a good idea at the time.  Electric lights which  were installed around 1925 were an improvement on the gas lamps they replaced but the benefits of some of the plumbing from the 1970's and 1980s is not obvious.

It seems that there have been two distinct phases of energy management, the first from the time the house was built up to 1970 and from then to 2005.  Around 1970, natural gas, also known as North Sea Gas became available in the UK, as a domestic fuel it was both cheaper and less labour intensive than coal which it rapidly displaced.  Whilst coal was not cheap, consumption was in part limited by the availability of labour to burn it.  In much the same way as the speed of early coal-fired steam ships was determined by the rate at which stokers could shovel coal, the amount of coal a house could burn was limited by the labour available to carry  the stuff to the fireplace and dispose of ash the following day.  Our house had six open fires, a coal -fired range for cooking and hot water and a copper for the weekly wash bringing the number of places where coal could be burnt to a total of eight.  Within a relatively short period coal was displaced by gas central heating which warmed the whole house, the only control being an on/off switch,  those  people who found the operation of switch too demanding, delegated this task to an electrically driven timer.  The standard of insulation of houses built before 1970 (and maybe for the next two decades) was not high and coal fires needed a good supply of air to burn properly, so Victorian houses were drafty by design.  The installers of gas fired central heating systems handled this by simply putting in big boilers, often in the range 20 to 40 kw.

I've used the language of the 21st century to describe a household of 1901.  The first of these is "zoning", in modern day terms, this means controlling the heating in two or more parts of the house, often "upstairs" and "downstairs".  For the Edwardians, this meant only lighting a fire in a room which was in use, so in the case of our house, there would have always been a fire during the day in the kitchen range and a fire in the living room during the evening, maybe one in the dining room if friends were coming round for supper and you would probably have had to have man flu or some other ailment to get a warm bedroom.

For lack of a better description, the next difference was "integrated energy use".  When the house was built, cooking was done on a  coal- fired range, whilst these things were no great joy to clean, they were alight for from dawn to dusk which meant there was always one room which was warm.  An industrious cook could use the range to maintain a supply of meals, bread, cakes, tea and coffee.  Managing a range required some skill, a fast fire which would be ideal for frying eggs might make the oven too hot for bread which should be baked in a cooling oven.  Also, when money was in short supply, the fuel might be nutty slack or green wood which required some patience and not a little skill to produce a loaf of bread.  It was the warmth of a kitchen which drew people in from the rest the house.

The third concept was "waste heat recovery", this is a feature of modern boilers which attempt to recover the latent heat from the water vapour which results from burning methane in air.  This can be offset by kitchen extractor fans which take the nice warm air from the kitchen and use it to heat the garden.  The Victorians had some ingenious devices for recovering heat, one which to the best of my knowledge had no domestic application, consisted or a chain rotating at the base of a factory chimney.  The top of the chain was heated by the flu gases from the firebox of the boiler, the bottom of the chain was in the boiler's feed water.  This shows some enthusiasm for energy management.  Within a home, waste heat recovery could be a back boiler on the range or simply a heating coil placed in the flu as part of a simple "gravity feed" hot water system.

What is now part of the modern day kitchen was once a coal store filled from outside the house via shute sealed off with a manhole cover.  The capacity of the coal store was, maybe, two tons which was enough to keep the house functioning for several weeks. This "energy storage" did two things.  At the national level, it evened out the demand for coal, whilst the demand for coal peaked in winter, the capacity of mines and the transport system were probably close to the "average" for the year.  In contrast, whilst the modern gas distribution does have some storage capacity, like the old "gasometers" which used to rise and fall and the more modern method of pumping gas into depleted gas fields, the system is sized to cope with "peak" demand.

Having energy storage at the household level also ensured that there was an effective local energy market, most towns had at least two coal merchants and prices would be lower in summer than winter.  Whilst the modern day gas consumer can "swap" supplier which does provide a measure of competition, this is far removed from an exchange between the coalman and some hard nosed housewife.

Since 2005, energy prices have risen sharply.  There is no economic incentive to revert to coal as a domestic fuel because in terms of body warmth, gas and coal seem to cost about the same and the "clean air acts" control the use of solid.  These bits of legislation were created to bring to an end the plots of "who dunnits" in which heroes and villains could conceal their activities in thick London fog as did Raffles  in the "Ides of March".  However, history might offer some guidance for the future, even if the mobile phone has made it harder for writers of crime fiction.

A ventimeter, a kite and a bicycle

For some time I have been studying wind speed distributions from a variety of sources including airports, offshore buoys, weather balloons and backyards and whilst this has been instructive, it has told me little about the wind where I live. Weather reports from an airfield on open ground 10 km to the west, often don't describe what I see from my house on the west side of an urban valley.  About a year back, a personal weather station appeared on pole a few streets away and since then I have changed my dog walking route to so I can observe the anemometer and wind vane, hopefully without invading anyone's privacy.  Unlike many PWS, this one is clear of roof and tree tops.  It clearly responds long period gusts and the frequent changes of direction which seem to be a feature of urban wind, often the anemometer is gently turning with the vane fluttering in the direction of the prevailing all of which suggests a wind speed of less than 5 m/s.

 


I have attempted to gain some understanding of wind in the area I live in by cycling around with a hand held ventimeter type wind speed measuring device, these efforts have been described in a couple of previous posts (fortunately, my family only rarely read this blog).  This too was quite useful, but my arms only extend to 2 metres which is close to the ground for serious wind speed measurement.  Recently, I have started messing with a small kite, not only is this instructive and three dimensional, it is also fun.  The ventimeter attracted little attention, except from an alsatian dog called Trooper, but most people smile at the kite, especially old ladies.  Maybe there is some point to be made about making environmental science accessible, but life is too short.

The kite is difficult to fly in even light turbulence, sometimes on a gusty day, a random swirl of wind will take it into relatively smooth air where it fill fly contentedly as long at the air keeps moving, once the gust subsides, it returns to Earth..  Having spent a lot of my life crunching numbers, it has been a surprise, how much can be learnt without a single keystroke.  Whilst its short on numbers, the kite provides an indication of the change of turbulence with height.  In the sketch below, the layers and circles are very roughly at 10, 20 and 30m, the arrows are relatively smooth air and the circles represent turbulence.

Wind blowing off the sea is usually smooth, however, wind coming from the land can become turbulent if it passes over trees and buildings.  On a coastal plane, hedges can create local turbulence below relatively smooth air.  In urban areas, the wind is almost always turbulent, at least up to treetop height.  I would not recommend flying a kite in an urban area to investigate.  I have always been curious about the performance of three medium sized wind turbines in the vicinity of Dagenham which I have seen turning smoothly.  On ridges above the surrounding land, gusting is less than on the approaching slopes.  If the wind is flowing up the slope it can be relatively smooth, but if the slope is in the wind shadow of a ridge, it can be almost calm with only long period gusts.

These comments have the caveat that they are drawn from a small sample collected across a relatively small area using a kite.

Diffuse Irradiance (Part 3)

A project which has been going on for an embarrassingly long time requires the ability to take a weather forecast and turn it into a forecast of possible wind and solar energy.  The concept is that some software downloads a weather forecast (in this case a TAF) and estimates the amount of solar energy that a PV Panel might produce.  If overcast conditions are likely to prevail for the next 24 hours, it charges it's batteries using off-peak electricity.  This requires a simple cloud sky model which in turn requires a simple clear sky model.  The clear sky model base based on Sun-Earth geometry and gives an estimate of the solar irradiance from a sky with no clouds, the cloud sky model then reduces the clear sky irradiance according to the nature of the cloud cover.  At this stage, work on the cloud sky model  consists of grinding out the correlations.

After some experimenting, it was decided to use a correlation found in "Applied Solar Energy" by A.P. and M.P. Meinel which was published by Addison Wesley in 1976.  Despite being based on observations made in the Mojave Desert in the late 60s this formula provides reasonable estimates of Direct Normal Irradiance (DNI)  for several climate types.  It is a simple model, requiring only input being Air Mass.  What I could not find was an equivalent for formula for clear sky Direct Horizontal Irradiance (DHI).  I had gained a little experience of making solar irradiance measurements whilst cloud watching in the back yard.  This formed the basis for a crude prototype shaded radiometer, but having collected data for just over a year, it is still in its crude form, this is partly due to laziness, but mainly the risk of introducing inconsistencies into the results.

Observations are made on clear days, there is more data for moorings than afternoons.  Even though an English day might start with a clear sky, clouds start to form mid-morning.  I still need to collect some more readings when the air mass is in the range 1.5 to 3.0.  The graph below shows the results to date of spending several sunny mornings in the park or on the beach:

An important part of the observing routine is making notes on the state of the sky.  Diffuse irradiance increases significantly when conditions are hazy or cumulus cloud is forming/dispersing, observations made under these conditions were discarded from the correlation, they are the green series on the graph.  Excel's Solver was used to produce this correlation:

This formula should be treated with caution, if only because it has not been reviewed by anyone other than the author.  Also, the calibration of the radiometer needs to be reviewed.  In addition, the Sun-Earth geometry code has been revised an recently ported to Python and is still being tested.  Thus some form of revision is likely.

This the shaded radiometer in use:

I would have liked to made some observations whilst the dust from the Saharan Desert was airborne over the UK around April-03, at a guess this would have resulted in above average levels of diffuse irradiance.

Conservation - It helps if you get payback!

Two questions which arise about a sustainable energy economy are "why" and "how".  Most people accept the desirability of minimizing our dependence on fossil/nuclear sources, but it's perceived as a long term aspiration with few, if any, short term benefits.  Politicians like to talk about "investment" in energy saving technology, effectively moving the problem into the future, they are less comfortable with promoting energy saving behaviour.  Back in the winter, some journalists attempted to get a minister to say the people should wear jumpers if they were cold, this is maybe appropriate advice, but a statement open to misrepresentation.  My guess is that most people having problems with rising energy bills were already wearing at least two pullovers.  One thing which does encourage conservation is things which payback in a reasonable time, i.e. in months, not decades.

Over the past year, I've spent about £60 on LED lights, the first two did not win hearts and minds and they have been relegated to my workspace, but two 3 watt 360 degree bulbs have replaced some passage lights which are most frequently turned on, so 12 watts of LED's have replaced 80 watts of CFL's.  This drop in consumption has, in part, caused my electricity provider to repatriate £60 to our bank account.  I now have an incentive to go and install some more LEDs.  The current crop of LEDs are not a good fit for every place we've got a CFL, but I'm certain I can work a few into the sitting room.

No one noticed the change from a 20 watt CFL to a 3 watt LED in this hall light.

I've had this conversation a couple of times and read accounts of similar ones in the papers.  When people install rooftop PV, almost the first thing they do is attempt to balance generation and consumption.  If they were taking 3,500 kwh from the grid each year, they try and get this down to the amount generated by the panels, say, 2,500 kwh.  A 1,000 kwh/year saving comes quite easily although it may cause tensions within the family if someone becomes too obsessive.  Do you have to spend more than £5,000 before you go and find out how much energy your daughter's hair straighteners use.  The domestic upset caused a daughter with manky hair, is in my opinion, too high a price, even to save the planet.  A better target is the laundry, especially, if there is a tumble dryer involved.   If your lifestyle permits it and you have the space, invest in a washing line or whirligig.  I suggest that a washing line is a solar thermal device and eligible for the government's Renewable Heat Incentive (RHI).  Some not too sophisticated sums suggest that that hanging out the washing, can save several hundred kwh/year relative to a tumble dryer.  I live in fear of my ragged underpants becoming a permanent feature of Google Earth but  it is a small price to pay for saving the planet.

The picture shows a solar thermal device in action.  The drying frame cost about £20 and dries washing with a combination of wind and solar energy, maybe it generates a few hundred kwh/year, contrast this with a rooftop solar water heater which in England's climate also generates the same amount.

And my point is.  I'm not going to comment on the merit of schemes like Feed-in Tariffs, RHI and subsidies for electric vehicles, mainly because I have not studied them in sufficient depth to have an informed opinion other than to say that they create an impression that sustainability can only be achieved through major "investment".  These schemes have wider implications than sustainability, they also impact job creation, stimulate new industries.  New, low cost technologies and small behaviour changes also have a roll to play.  This poses the question, if installing rooftop PV causes a drop in consumption,  how can you achieve the same saving without the up front payment.  Will the prime minister's underwear ever be found on Google Earth?

Storage - A Bonus Technology

My first encounter with storage was whilst working as a paint sprayer and shot blaster in a factory using batch production.  The shot blasting part of the job involved hanging on to a hose gushing compressed air and ground up cast iron whilst wearing a rubber suit in a steel booth.  The compressor was too small to power the blaster alone, so it charged up a pneumatic accumulator which took an hour or more to fill and provided enough air for ten to fifteen minutes blasting, which is about as long as you want to wear a rubber suit.  This fitted in well with the other production tasks because it generally took an hour to organise the work, engage in an exchange abuse with the welding station upstream and drink milk.  The Factory Act required that the blaster/painter was to be supplied with one/two pints of milk per day, this was a form of discrimination against vegans.  A critical part of the job was managing the accumulator because blasting and painting were at the end of the production process a lack of planning could put the weekly bonus in danger.  This was the dirtiest job I've ever had, but it paid well and gave me the funds to go to college, so I'm deeply grateful for it.

The next encounter was more analytical and was related to offshore oil production.  It was an attempt to derive a relationship between crude oil storage volume and loss of offshore production due to bad weather.  Small offshore oilfields which are remote from a pipeline are often developed using a drilling/production platform which exports its oil to a tanker moored to a nearby buoy.  In calm waters, production is more or less continuous, there is a brief shutdown whilst the full tanker is disconnected from the buoy and and an empty one takes its place.  However, in harsh environments where the wave height can be too high  to allow safe operation, the tanker has to disconnect in rough seas and stand off until the weather improves.  Introducing an element of storage into the system allows the platform to continue production when it would otherwise have had to shut down.  The sketch shows the main elements of the system.

By combining wave height data collected from offshore buoys in the region with the operating limits of the mooring buoy it is possible to suggest a relationship between the storage volume and production lost due to bad weather.  This in turn can be combined with estimates of the incremental cost of storage to keep an economist off the streets  for a considerable time.

Storage is a key element in sustainable energy system, wind and solar are non-continuous resources and it is desirable to be able to store energy when it is available but not necessarily wanted.  The classic example is using a battery to store the yield from solar panels for use in lighting the house after sunset.  In the UK the peak demand for electricity occurs early evening in winter, this drops off after midnight, even a relatively small volume of storage, say, less than 5 kwh/household would smooth out demand and ease the integration of wind and solar resources.  At present, the government is providing a subsidy of £5,000 to the buyers of electric cars (storage on wheels), I'm reluctant to criticise anything that might have an environmental benefit, but it would be an interesting exercise to consider what the benefits would be to providing support for storage in commercial and domestic buildings (storage without wheels).  If done carefully, this to, could act to stimulate industry.

I'm maybe stretching a point with this analogy, but the concept of domestic energy storage is not new.  Many Victorian and Edwardian houses had some form of coal storage, traces of which can be still be seen, especially on the streets of London where manhole covers like this are still visible.

The designs can be elaborate with the maker's name worked into the artwork, sometimes with a patent number.  Now the space below the manhole is most likely to be used as a kitchen or utility room, but at the time the house was built it might have looked like this:

Depending on the size of the house, the coal store might have held between one and five tons of fuel.  This form of heating required the householder to be aware of the seasons, coal would be cheaper during the summer, but in winter when all the open fires were in use, the price would rise, so the prudent housewife would want to start the winter with a good stock.

Alongside the coal store in a cool part of the house, there might also be food store or larder.  Not every pre-war housewife dedicated August and September to jam making, bottling and preserving the harvest from the garden, but these seasonal activities were lurking somewhere in the culture.