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.
Sunday, 30 November 2014
Saturday, 22 November 2014
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.
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.
Sunday, 9 November 2014
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.
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.
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:
Saturday, 1 November 2014
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.
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.
Saturday, 25 October 2014
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?
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?
Sunday, 19 October 2014
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
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
Tuesday, 7 October 2014
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.
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.
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