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Energy general

In physics, energy is an indirectly observed quantity that is often understood as the ability of a physical system to do work on other physical systems. However, this must be understood as an overly simplified definition, as the laws of thermodynamics demonstrate that not all energy can perform work.

Depending on the boundaries of the physical system in question, energy as understood in the above definition may sometimes be better described by concepts such as exergy, emergy and thermodynamic free energy. Therefore, in the words of Richard Feynman, "It is important to realize that in physics today, we have no knowledge what energy is. We do not have a picture that energy comes in little blobs of a definite amount."However, it is clear that energy is always an indispensable prerequisite for performing work, and the concept has great importance in natural science.

Energy cannot be created or destroyed according to the law of conservation of energy. However thermodynamic free energy can be destroyed. When matter (ordinary material particles) is changed into energy (such as energy of motion, or into radiation), the mass of the system does not change through the transformation process.

Although the total energy of a system does not change with time, its value is measured with respect to its frame of reference. For example, a seated passenger in a moving airplane has zero kinetic energy relative to the airplane's frame of reference, but non-zero kinetic energy relative to the Earth's frame of reference because of the relative velocities.

Energy may be stored in systems without being present as matter, such as when a mass has been moved through a field it interacts with and the energy to accomplish this is stored as a new position in the field. This type of energy is referred to as potential energy. A simple example of an object increasing its potential energy is the work needed to lift it in a gravity field onto a support.

Any form of energy may be transformed into another form. For example, all types of potential energy are converted into kinetic energy when the objects are given freedom to move to different position as for example, when an object falls off a support under the influence of gravity. The new potential energy with respect to the gravitational field is lower; the difference being due to the kinetic energy transformed to heat energy when the object hit the ground. In all such energy transformation processes, the total energy remains the same, and a transfer of energy from one system to another results in a loss from one to compensate for any gain to another. This is the principle of the conservation of energy.

 

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Einstein's Theory of Relativity
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December, 1916
A. EINSTEIN

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Fuel Cell Handbook - ebook
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Fuel cells are electrochemical devices that convert the chemical energy of a reaction directly into electrical energy. The basic physical structure or building block of a fuel cell consists of an electrolyte layer in contact with a porous anode and cathode on either side.

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As many small-scale methods of electricity generation are available only intermittently, some form of electricity storage or battery is needed if people want to have electricity available at all times.

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Ground Source Heat Pumps - leaflet
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Energy Saving Trust on Ground Source Heat Pumps

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The Future of Energy Use
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An analysis of the use of different forms of energy and its environmental and social impacts. Giving an overview of the development of different forms of energy provision and patterns of supply and demand, this book shows how enduse applies to energy industries, how the environment and social costs of energy use have to be introduced into energy planning and accounting and the crucial role of efficiency. Case studies will include the transport and building sectors of industrial economies, the use of stoves and woodfuel and agroforestry planning in developing countries. It will then examine the different forms of energy - conventional, nuclear and renewable - concluding by setting out different energy futures and the policy requirements for sustainable futures.

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green electricity factsheet - ebook
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It is obtaining the electricity that you use from environmentally-friendly sources. The electricity you use in your home is probably from the National Grid. There are ways of being 'off-grid', for example using a generator, solar pv, wind, hydro, or micro-chp, together with batteries. But the vast majority of people in the UK are connected to the National Grid. And most of the electricity put into the National Grid is 'brown' - from power stations using fossil fuels (coal, gas, oil) or nuclear. But now some companies are feeding the National Grid using renewables, for example large wind turbines or hydro-electricity. This is 'green' electricity. Also included in the 'green' category is electricity from companies that use your money to research and build new renewable generation capacity, or to offset carbon by investing in projects to absorb or reduce carbon emissions in some other way.

Two more things that you need to know: Firstly, there are two types of companies involved in providing green electricity – suppliers and generators. Some companies have no electricity generating capacity, but supply the public with electricity that they have purchased from generating companies. Other companies (e.g. Ecotricity) are both suppliers and generators. Ecotricity operate around 25 Megawatts of wind turbine capacity, and also sell direct to the public. Secondly, if you switch to a green electricity supplier, you won't then be able to trace your electricity back to a wind turbine. It simply means that the more people switch, the greater the proportion of green electricity in the National Grid.

what are the benefits?

This is not about home-scale micro-generation from renewables. This is about your contribution to large-scale renewable energy developments, like wind farms, large hydro-electric power schemes, and also wave and tidal power.

There is some opposition to large renewable energy projects, notably wind farms, and we respect people's opinions about the effects of wind turbines on the landscape. We wouldn't want turbines on every hillside, but we think that ultimately, ecology (which after all, supports human life on this planet) is more important than the view. And anything that mitigates the problems below has to be explored. It's too important not to. If you switch to green electricity, you are helping develop large-scale renewable energy projects, which help counter the problems associated with the alternatives - which are:

climate change
There is no 'debate' any more. 99.9% of scientists recognise that climate change is happening, it's dangerous, and it's man-made. The media promote the idea of a debate to sell papers and put bums on seats. There is a direct link between CO2 in the atmosphere and average global temperatures, and CO2 has gone up by about a third since the industrial revolution (and is rising rapidly). You may think this means warmer summers and milder winters (good), but it also means more deserts, melting ice-caps and large-scale coastal flooding, more hurricanes, environmental destruction, famine, and the deaths of millions of people (very bad).

peak oil
Oil is a finite resource, and its use is increasing dramatically. This can only mean one thing – it's not going to be around for much longer. 'Peak' oil means the point of maximum production, after which prices increase and production tails off to (eventually) tiny amounts as we try and find the last drops from currently uneconomical fields. As most of our food (especially in the West) depends on oil for fertilizers, machinery and transport, unless we have alternative energy supplies, or you produce your own food (and manage to hang on to it), you're going to go very hungry.

nuclear power
There's not enough uranium left for nuclear power to take over from fossil fuels for more than a couple of decades. Fast breeder reactors could increase that, but they're not safe; and it's not at all sure that nuclear fusion (what happens inside the sun) can ever be harnessed, or at least in the near future. And there's the question of devastating accidents, and nuclear waste, which is highly dangerous for tens of thousands of years (and we're still discovering Roman ruins from a couple of thousand years ago!). And yet nuclear continues to receive billions in taxpayer subsidies while renewables receive next to nothing.

Who knows, there may be an invention around the corner that will solve these problems, but it's not looking likely, and it's too much of a risk to do nothing.

what can I do?

You can switch to a green electricity supplier – today. It is probably the easiest and quickest way to have a significant effect in helping to reduce the damage to the ecology of our planet.

The green electricity market is constantly changing as new players enter, new generating capacity is built, and prices change. Also, because suppliers are in direct competition with each other for your custom, there is a huge amount of marketing information out there, which can be daunting and confusing. Fortunately, there are websites to help you keep up with the changes, and to compare green electricity suppliers. As mentioned, there are different kinds of green electricity, so price isn't everything. Having said that, you can compare the tariffs of green electricity suppliers in your area by visiting Green Prices.

So, once you have checked out some of these websites and decided which supplier is the one for you, as regards their activities and the price of their electricity, simply go to their website and switch online, or give them a call. It can be done immediately, with no interruption to your supply.

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Living Off the Grid Guide - ebook
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Free Energy

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Biofuels, Solar and Wind as Renewable Energy
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With shortages of fossil energy, especially oil and natural gas, and heavy biomass energy use occurring in both developed and developing countries, a major focus has developed worldwide on renewable energy systems. Renewable energy systems include wind power, biomass, photovoltaics, hydropower, solar thermal, thermal ponds, and biogas. Currently, a heavy focus is on biofuels made from crops, such as corn, sugarcane, and soybeans, for use as renewable energy sources. Wood and crop residues also are being used as fuel. Though it may seem beneficial to use renewable plant materials for biofuel, the use of crop residues and other biomass for biofuels raises many concerns about major environmental problems, including food shortages and serious destruction of vital soil resources. All renewable energy systems need to be investigated because humankind has only about 40 years of oil and gas reserves remaining. There is a 50 to 100 year supply of coal resources in the ground, but coal will become increasingly difficult to extract and will greatly increase the global warming threat. Serious energy conservation and research on viable renewable energy technologies are needed. This book considers the effectiveness and economics of several renewable energy technologies of current interest, including biofuels, solar and wind

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Sustainable Energy — without the hot air
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About the author

David MacKay is a Professor in the Department of Physics at the University of Cambridge. He studied Natural Sciences at Cambridge and then obtained his PhD in Computation and Neural Systems at the California Institute of Technology. He returned to Cambridge as a Royal Society research fellow at Darwin College. He is internationally known for his research in machine learning, information theory, and communication systems, including the invention of Dasher, a software interface that enables efficient communication in any language with any muscle. He has taught Physics in Cambridge since 1995. Since 2005, he has devoted much of his time to public teaching about energy. He is a member of the World Economic Forum Global Agenda Council on Climate Change. He was elected a Fellow of the Royal Society on 14 May 2009.

About the "free book" license

This is a free book. I didn't write this book to make money. I wrote it because sustainable energy is important. If you would like to have the book for free for your own use, please help yourself to any of the electronic versions on this website. There's pdf and html versions (thanks to William Sigmund!); we are working on other formats.

This is a free book in a second sense: you are free to use all the material in this book, except for the cartoons and the photos with a named photographer, under the Creative Commons Attribution-Non-Commercial-Share-Alike 2.0 UK: England & Wales Licence. (The cartoons and photos are excepted because the authors have generally given me permission only to include their work, not to share it under a Creative Commons license.) You are especially welcome to use my materials for educational purposes. This website includes links to separate high-quality files for each of the figures in the book.

In response to generous readers...
If you enjoy the free electronic copy of the book and would like to make a financial donation, without buying the paper book for yourself, please may I suggest that you find a library or a school that would like a copy of the book, and buy a paper copy for them? Thank you!

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Handbook of Homemade Power - Mother Earth News
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Bantam 1974 374 p. Includes: illustrations, diagrams, index. 4-1/4" x 7". Alternative energy information, collected and published during the energy crisis of the 1970s. Sections on heating and powering your home with wood, water, wind, solar, and methane.

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Energy Revolution 2012 - Greenpeace International
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The world’s energy system has bestowed great benefits on society, but it has also come with high price tag: climate change, which is occurring due to a build of carbon dioxide and other greenhouse gases in the atmosphere caused by human activity; military and economic conflict due to uneven distribution of fossil resources; and millions of premature deaths and illness due to the air and water pollution inherent in fossil fuel production and consumption.
 

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Renewable Electricity and the Grid
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In all national electricity supply systems, the power demand varies over the course of a day; there is a rise and fall every 24 hours, with usually a night- time minimum and a daily maximum. In order to assess the contribution that renewable or other sources of energy can make to electricity supply, the distinction between energy and power has to be kept clearly in mind. Whereas the commercial operation of each generation plant is measured against total energy delivered, in the UK the central grid control operated by the National Grid Electricity Transmission plc (National Grid), acting in its role as Great Britain System Operator (GBSO), has to ensure that the power generated (the rate of delivery of energy) balances the power demand at all times, otherwise the system fails.
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Key World Energy Statistics 2013
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The IEA produced its first handy, pocket-sized summary of key energy data in 1997 and every year since then it has been more and more successful.

Key World Energy Statistics contains timely, clearly-presented data on supply, transformation and consumption of all major energy sources.

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The Complete Book of Self-Sufficiency - ebook, By John Seymour
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The Complete Book of Self-Sufficiency is a book for all seasons. Whether you live in town or country, on a farm or in a cottage, in a house with a garden or a flat with a window-box, this book has something for you. If you want to bake your own bread, brew your own beer, make your own cheese, pickle your own onions, this book will show you how. If you want to make hay, milk a cow, smoke a ham, design a dairy, convert to solar energy, this book will show you how. If you just want to grow your own vegetables, bottle your own fruit, dry your own herbs, this book will demonstrate exactly what to do.

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Heat Pumps - Energy Efficiency and Traditional Buildings
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The installation of a renewable technology implies in most cases the fixing of equipment to the historic fabric of a building. English Heritage seeks to ensure that any works to a historic building do not unnecessarily disturb or destroy historic fabric.

In deciding how best to incorporate a low-carbon or renewable technology, the principle of minimum intervention and reversibility should be adopted whenever and wherever possible.

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Key World Energy Statistics 2014
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The IEA produced its first handy, pocket-sized summary of key energy data in 1997 and every year since then it has been more and more successful.

Key World Energy Statistics contains timely, clearly-presented data on supply, transformation and consumption of all major energy sources.

The interested businessman, journalist or student will have at his or her fingertips the annual Australian production of coal, the electricity consumption in Japan, the price of diesel oil in Spain and thousands of other useful energy facts.

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The Complete Book of Self-Sufficiency, By John Seymour (Paperback)
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The Complete Book of Self-Sufficiency is a book for all seasons. Whether you live in town or country, on a farm or in a cottage, in a house with a garden or a flat with a window-box, this book has something for you. If you want to bake your own bread, brew your own beer, make your own cheese, pickle your own onions, this book will show you how. If you want to make hay, milk a cow, smoke a ham, design a dairy, convert to solar energy, this book will show you how. If you just want to grow your own vegetables, bottle your own fruit, dry your own herbs, this book will demonstrate exactly what to do.

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Diesel Engine Repair and Maintenace
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