For some time now I have been worried about the present batch of “Alternative Energies”, their biggest problems are to do with efficiency and their ability to deliver energy when it is needed rather than just when it is available. Great savings can be made in energy efficiency in order to reduce our need for energy but fundamentally in order to achieve a low-carbon existence we need ways to make “Alternative Energies” work for us, and by “Alternative Energies” I mean taking advantage of natural sustainable sources of energy such as wind, wave and solar power. Making best use of these sources is even more important since the German Government decided to shut down all of it’s nuclear power generation earlier than planned, because now European fuel prices have to rise dramatically because Germany will now be vastly more dependent on Fossil Fuels until they can fill the gap with viable alternatives.

Currently the way we store energy if there is an excess in the grid is to convert the excess electricity into potential or kinetic energy until it is needed again later. There are many water storage facilities in the UK which pump water up-hill to large reservoirs in a technique called “Pumped Storage Hydroelectricity“. By pumping the water up-hill when you have excess energy you can then let it come back down again and recovery the energy with hydroelectric turbines. Each time you do something like this you waste some of the energy because of energy conversion inefficiencies.

Wind energy is interesting, when the wind blows we get a fair amount of energy returned by the gigantic wind turbine. The most you can ever capture from a wind turbine is 59% of the available wind energy passing through, this is a fact of physics proved by Albert Betz in 1919. However that is the upper limit, in reality there is conversion from kinetic energy (the motion of the wind) to electrical energy and such conversions always result in a loss of efficiency in gears, dynamos and power couplings. Because this energy is available “When The Wind Blows” and at no other time there have been issues where the National Grid has had to shut down turbines because they weren’t needed and this is a great waste of their potential.

Solar energy is another area of great interest to many people and I struggle to get excited about what should be a great source of energy because everyone gets excited about Photovoltaic (PV) energy which uses chemically doped materials to directly convert sunlight into electrical current. The reason I struggle to get excited is that PV isn’t very efficient, typically high quality solar panels are about 14-17% efficient and that really isn’t very much. Also solar PV cells need various exotic chemicals in their production of which only a portion is recycled and they aren’t exactly “low carbon” in their transport around the world. Solar energy is logically only available during the hours of sunlight and again, logically, is subject to the intensity of the sun in the location.

In an “Off Grid” environment, where a home owner has no access to mains electricity from the grid, it is quite common to store energy in batteries so that the peak energy availability can be disbursed over a longer period. Not everyone has access to a source of large quantities of water and a reservoir pond (or two) to store it in. Batteries are great for our mobile phones, they store energy in chemical form for good periods of time and release it on demand. Some batteries can release their energy quickly or some can release it slowly over long periods of time. But fundamentally batteries are flawed because they depend on harsh chemical processes which break down the components over time and can result in failure of the cell. Also you can only really discharge a deep cycle battery to 70-80% before you start causing premature damage to the battery cell, thus you need to be careful with your management of supply and demand.

Some time ago I started to wonder: why don’t we store more energy as directly coupled kinetic or potential mechanical energy? Wind farms, for example, I wondered if it wouldn’t be a good idea to install giant clock springs under them (or in their stems) so that we could regulate the release of all of that good mechanical energy. Now, giant clock springs sound silly at first, but actually many companies use kinetic energy storage as a power backup medium. In computer data centres, when you have a power failure it takes time to start the local on-site diesel generators and you need something to keep all the equipment going until the generator is up to speed. Some companies use giant banks of batteries which they carefully maintain and monitor, but I have seen a few UPS failures and they get rather messy and expensive. Plus batteries can release hydrogen gas which could cause harm to operatives working in the UPS battery room. The alternative that some companies really do use is to use a motor to spin a giant “fly-wheel” on a very efficient bearing, when the power fails that mass still has a great deal of momentum, and as the motor is no longer supplying force to keep it spinning it can be used as a generator to take that kinetic energy and turn it back into electricity. There can be enough energy in the momentum of a large enough mass to keep a data centre alive until the generator is ready to take the strain. This spinning mass technique however somewhat depends on the problem that you can’t store such kinetic energy for long periods, the friction of the bearings causes momentum to be lost over time and affects efficiency but it is great for short-term non-toxic energy storage. Some buses around the world are now using spinning masses as a means of kinetic energy recovery in breaking and they can then use that energy to help move the bus away from the stop before the engine takes over again, a nice and clean “Start-Stop” technique.

This application in buses and the idea of the hydroelectric storage leads me to another angle. The disadvantage of water as an energy store is partly because it can’t be compressed, it takes up a great deal of space and the disadvantage of kinetic energy is that the spinning mass can’t spin forever. Well, what about storing energy in a static way, under compression which can be quickly released on demand. This leads us neatly to: Compressed Air Energy Storage. Now of course I don’t declare to be the first to propose such an idea, because it is already in industrial use around the world to a limited degree. But what I would like to do is highlight the concept because it deserves more attention and also because I think it might have some interesting applications as a battery replacement technology.

In an off-grid situation we could see a tank being placed in an out-building which has a store of highly compressed air, this is generated through wind, solar or other inconsistent energy supply. In addition I think that some kind of Sterling Engine arrangement could supply the mechanical work for solar energy without needing to waste energy on conversion to and from electricity just to achieve compression. What about automotive situations? Many companies are installing very expensive and potentially unreliable batteries in cars, what about compressed air tanks which could be used as a kind of compressed air transmission instead of a gearbox? Directly drive the gears with the compressed air perhaps? Just put a 600CC compressor in and regenerative breaking, should have a snappy little number!

This is a proposal I am working on with some people, I have put it here because it might protect me a little to have it published online:


Continue reading “Virtualised broadcast infrastructure”


The coming launch of ‘Freeview HD‘ will doubtless have implications for retailers as well as consumers and in this note I hope to help address some of the questions. There are several new features which are implemented in ‘Freeview HD‘ which might impact consumer and some less obvious features you might not know about.

New features:

  • DVB-T2

This is a new type of transmission technology which has evolved from the existing DTT standards and next generation communications theory.

  • H.264 HD video

Using the more recent developments from MPEG using the H.264 compression method the video can be transmitted in as little as 25% of the bandwidth that would be required for the same type of transmission in MPEG2. This allows HD which would consumer substantially more bandwidth to be transmitted efficiently.


MHEG is the standard for interactive services in the UK and is a very light weight system. It failed to impress some people in it’s original form but substantial progress has been made in the last few years to delivery a much more powerful user experience. The speed and graphics quality has been enhanced and the implementation on Freesat has already proven popular with consumers. As time passes the developers are able to demonstrate further enhancements in graphics performance and quality. The most significant step is in being able to render graphics to the screen with HD resolutions.

  • MHEG Interaction Channel

This allows MHEG applications to communicate back to the broadcasters over the consumers broadband package. This potentially gives consumers access to interactive voting, a wider range of content than can be broadcast and even streaming catch-up television. Broadcasters will decide what services they will implement but the connection is available to consumers on their product for those future services.

  • Audio Description

All products are now expected to be capable of audio description, this system allows people with visual impairments to have a description of the programme they are watching. TV is popular with a wide range of people and we are looking to include as many groups as possible. It will even work on HD channels, so the whole family can enjoy the latest releases. Some products may not support mixing multi-channel surround sound with AD tracks to produce surround out, but AD will still work with surround but produce a stereo output.

  • HD Subtitles

In addition to supporting existing Teletext format subtitles and standard DVB format subtitles the new boxes should now support HD format DVB subtitles which provides decent subtitles for HD video broadcasts.

Less obvious features:

  • HD Simulcast

The broadcaster can signal that a programme is also available in HD so that a viewer can get the best quality version even when watching the SD channel.

  • Content Management

Broadcasters have difficulties obtaining rights for some programmes to be broadcast in HD on free television. So in order to be licensed by ‘freeview’ the manufacturer must agree to record the broadcasts subject to rules that are transmitted by the broadcaster for each programme. It is possible for the broadcaster to signal that they will not permit the programme to be copied or that it may only be copied once. They may also indicate that the programme can be streamed or copied to DVD. The ability to archive and copy programme content is not a requirement but where it is implemented it must follow the broadcast rules.

  • Network Change Notification

The transmitter network can signal when changes are going to happen, this way when a re-tune is needed the receiving device can react more intelligently than they currently do.

  • Guidance Descriptor

A broadcaster can use new signaling on both programs and channels to indicate that their broadcasts contain content which may might not be appropriate for certain viewers. It is not intended just as an “Adult” genre but it is designed to show a wide range of sensitive issues, possibly including photosensitive epilepsy and violence.


  • What type of antenna does Freeview HD device need?

Freeview HD uses a traditional UHF antenna as used by existing terrestrial television.

  • Will I need a new antenna for DVB-T2?

No, not unless you don’t get a good signal level currently. The T2 transmissions are being designed to perform under equal conditions as the existing digital transmissions but with more bandwidth to put more information in.

  • What does DVB-T2 provide to broadcasters/consumers?

The development of DVB-T2 was not just about the steady march of time but has been done to provide more data in the available bandwidth. This means that the broadcasters can send more information per transmitter. DVB-T already allows many channels to exist in the same equivalent

  • I have a High Definition ready TV, will it support Freeview HD?

Freeview HD requires the product to support the DVB-T2 transmission standard, only products made on/after winter 2009 and which say they support “Freeview HD” will work with the new service. All current IDTVs will need an external set-top box device to be able to receive Freeview HD. The current definition of “HD TV Ready” does not cover the new UK standard for HDTV.

  • Can I upgrade my receiver to support T2?

It is not possible to software upgrade any existing products to support DVB-T2 due to the significant differences between the platforms. In theory certain IDTV displays from certain manufacturers may be upgraded by replacing certain parts of the hardware, but no manufacturer has yet stated their intention to do this.

  • When will broadcasts of HD services start?

No dates have yet been confirmed, but it is expected that in preparation for product being available broadcasts are expected to begin during Winter of 2009. This schedule may change in response to changes in conditions and consumers should not expect to have reception before 2010. The service will have limited coverage to begin with and only certain areas will have availability to begin with. Consumers should check their coverage to determine what services are available in their area. It may be that a product like the Foxsat-HD or Foxsat-HDR (using the Freesat service) is the best way to get access to free HD channels.

  • When will product be available for Freeview HD?

While the technology of HD has been available for some time the variations required for the Freeview HD, particularly DVB-T2, will require significant work. Because new silicon chips must be designed for this service there needs to be careful work on this investment.

  • How many HD channels will be available?

There will be an HD service from the BBC and other services are expected from ITV-HD and Channel4 HD. Eventually a fourth and perhaps fifth HD provider are expected to join the platform. The platform operators are aiming to upgrade the video encoders to improve their efficiency in order to maximise the volume of content available on the platform for the available capacity.

Further definition:

  • DVB-T2:

A working group of the European DVB organisation has evolved this new standard for transmission. This has allowed more data to be broadcast in the same terrestrial spectrum. This is achieved by using powerful error correction technology as well as learning quite a number of lessons from the work on DVB-T. It has been many years since Digital Terrestrial Television was first launched in the UK and in this time the engineers/scientists have studied the different parameters available to engineers then this time has highlighted areas for improvement. The change in error correction is based on some mathematics which was first used in DVB-S2 and has now been refined further for DVB-T2. Overall the system is exploiting the next generation of technology and the latest innovations in transmission/communications theory.

  • Multiplex:

A multiplex is the container which is used to broadcast digital services. The UHF radio frequency ‘channel’ in which a single analogue service was broadcast in can now be occupied by a multiplex which can contain many digital television services. There are currently six multiplexes in the UK which carry all of our digital television viewing. Each multiplex can carry services of differing quality averaging between eight and fourteen video services.

  • Bandwidth:

Bandwidth is the measure of size of the information carried, the term can be used in analogue or digital environments. In analogue it is the number of Hz and in digital it is the number of bits per second (the rate at which data is carried through a system).

  • High Definition (HD) video:

Currently used to define any superior resolution of video over 720×576 in pixels.