Haskell – the perfect programming language for children

I’ve started teaching my son programming on the Raspberry Pi.  The language?  Haskell.

As an experiment, I thought I’d avoid the mainstream imperative languages: BASIC, C, C++ – stuff like that.  Given he’s learning maths at school – counting, addition, subtraction, multiplication – all the fundamentals, I thought Haskell would be a good place to start: none of that imperative rubbish to cloud his learning – good, pure functions!

Here’s the lesson as it unfolds.

Step 1 – get the hang of the Haskell interpreter (hugs on the Raspberry Pi, as ghci isn’t yet available on the ARM architecture), and navigating around the keys

hugs > 2 + 2


hugs > 10+4


We did this for about an hour: I’d type a maths question in hugs – then before I pressed enter to evaluate the expression, he’d work out the answer and tell me.  He loved typing in very large numbers, trying huge addition sums, and was impressed the computer could perform such huge calculations!

Step 2 – now the simplest of programs: counting to a hundred.

hugs > [1..100]

And the interpreter duly obliged with 1, 2, 3, .. , 100.  Many variations on a theme here.

Step 3 – multiplication

hugs > 2* 2


And the next step is the one that caught my attention.  My son tried this:

hugs > [2*2..2*5]

A functional sub-expression!  Proper programming already.

Step 4 – Next theme: counting letters and words.

hugs > length “Twinkle twinkle little star”

hugs > length (words “Twinkle twinkle little star”)

I think functional languages are a superb fit for introductory programming.  Haskell Pi = Excellent!

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UK Rail Fares – Systemic Failure?

Recently I had to travel by train from Bath to London at peak times.  No choice – that was what I needed.  About one hundred miles each way, or an hour and a half.

The return rail fare?

One hundred and seventy four UK pounds.  £174.

Yes, that’s right – £174.  From First Great Western.

Many thoughts went through my head as  I handed over the money.  With that I could buy: a weekend break, a netbook, several decent meals, two weeks of food shopping …

I know that if I ask First Great Western why it’s so expensive, I’ll be told: “well, you don’t have to buy that ticket, book in advance, you can get cheaper tickets” etc.  So there’s little point asking; they’re not empowered to give a fair (no pun intended) answer.

So, why is rail travel so expensive?  200 miles at £174 is a mileage rate of 87p per mile.  Car travel is – all inclusive – typically 45p/mile, and only gets cheaper as you share.  For a driver and passenger, the mileage rate is just one quarter the combined rail fare!

I must conclude this is another case of systemic failure: but one that lies perhaps with the rail industry and its financing models?  The Victorians cleared the way (literally), building the track.  Why then, is it so expensive, to keep it running in the 21st century?

A systemic view would take all these costs into account; but then it would need to be answerable to a clear set of ‘quality of life’ criteria – something no organisation yet knows how to formulate for the benefit of its citizens.  Therein lies our challenge: to frame the problem so that it can be solved by the public.




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UK House Prices – Systemic Failure?

Since the mid 1990s the UK housing market has suffered rampant price inflation.   It is now at a stagnant high, the reduction in prices a lack of demand should trigger perfectly counterbalanced  by a chronic lack of supply.  The price correction that should have happened, hasn’t.  Instead, crazy policies like parents using their pension funds to guarantee their child’s mortgage borrowing are floated.  Business as usual is deeply disturbing.

So, what can we do to return house prices to sensible levels – the level any sane child would expect them to be at?

Step 1 – Ban second (and third, and fourth) homes

While there’s a shortage of first homes, why do we tolerate second home ownership?  Does anyone really need two homes?  Or three?  Until there are enough first homes to go round, ban further homes.  And of course, bring the empty homes back into use.

Step 2 – Redesign the UK housing system

The free market in housing clearly doesn’t work for everyone, or even the majority.  All markets are contrived, ostensibly for the benefit of the majority.  Where that isn’t the case, the system as it is currently designed has failed.  So re-design the system.  A sensible process would look at available supply, and demand, and assess both sides of the equation, and how they can be influenced.   Design and implement a multi-decade migration strategy to a new, fairer model, so that people who made earlier reasonable investment choices aren’t penalised, while meeting the needs of future generations.

Step 3 – Change the culture

Many European countries do not regard bricks and mortar as a ‘must have’ investment, and have systems that support long term stable rentals.  The UK should do the same, and move away from the ‘Assured Shorthold Tenancy’ as the dominant model for lettings.  Let tenants decorate their homes, have a say in renovations, and give them stability, both financial and physical.

Step 4 – Stop the Media selling rising prices as a ‘good thing’.



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Response to DTI Energy Consultation 2006

Response to DTI Energy Consultation

13 April 2006

The DTI Energy Consultation

DTI Energy Consultation 2006On 23 January 2006 the UK government launched an energy consultation entitled “Our Energy Challenge: securing clean, affordable energy for the long term” (www.dti.gov.uk/energy/review/). The government sought the views of the public and of industry on this vital topic.

This article reproduces my response to the questions posed in the consultation document, submitted online via www.dti.gov.uk/energy/en_consult.shtml.



Q1. What more could the government do on the demand or supply side for energy to ensure that the UK’s long-term goal of reducing carbon emissions is met? (MAXIMUM 750 WORDS)

The government should actively manage both demand, in order to reduce our need for energy, and supply, in order to provide clean, renewable energy.

On the demand side, we should:

  1. Embrace the principles of Contraction and Convergence (www.gci.org.uk), by introducing carbon rationing for all individuals and organisations, following the Tradable Energy Quota (TEQ) system (www.teqs.net), in which permits to pollute are issued, and progressively scaled back over the years to meet our obligation to reduce carbon dioxide emissions. TEQs would apply to all sectors of the economy, including home, industry and transport. This key measure would help the UK implement energy descent – the scaling back of demand to match available supply.
  2. Make people energy-aware, so they reduce their energy consumption (rising energy prices are already contributing to this awareness)
  3. Address the causes of excessive energy consumption. For example, few people can afford to live near their workplaces, since many jobs are based in towns and cities where house prices are extortionate. Consequently they are forced to commute large distances, typically by private motor car. To tackle this, we should fundamentally alter the UK housing market, so that people can afford to live near to where they work. This would reduce the time and energy wasted on travelling. Measures to achieve this could include house price control (limiting house price rises to inflation) and the abolition of stamp duty (a financial barrier to moving house). Unfortunately, current schemes such as key worker housing exacerbate the problem, as they continue to fuel excessive house price growth by supporting an unsustainable market.

On the supply side, we should:

  1. Eliminate all market-distorting subsidies given to nuclear, coal, oil and gas, and undertake a comprehensive switch to renewable energy, including wind, solar thermal, photovoltaic, tidal, biomass, ground source heat pumps and Combined Heat and Power (CHP). (Note, however, we should not regard incinerators as renewable sources, as they stimulate demand for waste to fuel them)
  2. Restructure the electricity market to favour local power generation over centralised power stations
  3. Charge for electricity at a rate proportional to the cost of production, not at a uniform wholesale price. This would encourage cheap renewable energy consumption at the times of day when available (e.g. run washing machine at night when the local wind farm is producing a surplus of electricity)
  4. Automatically grant planning permission for small scale domestic wind turbines and other renewable technologies

In conclusion, the government should place less reliance on “technology fixes”, and more emphasis on leading the UK population through the process of energy descent, putting in place the necessary behavioural and structural changes.

Q2. With the UK becoming a net energy importer and with big investments to be made over the next twenty years in generating capacity and networks, what further steps, if any, should the government take to develop our market framework for delivering reliable energy supplies? In particular, we invite views on the implications of increased dependence on gas imports. (MAXIMUM 750 WORDS)

Peak oil is a serious problem; we face a similar crisis with gas supplies. Rising oil and gas prices indicate that we face a growing worldwide shortage in fossil fuel supplies. There is a parallel danger, that of a mass switch back to coal, a heavily polluting source whose combustion will accelerate anthropogenic climate change. To address peak oil and climate change, we need a rapid widescale return to local renewable energy systems.

To achieve this, the government should:

  1. Remove VAT on all renewable energy products, technologies and services (regardless of whether installed privately or by professionals)
  2. Introduce a more flexible energy market, in which consumers pay the true cost of their electricity production – this will further stimulate the renewables market, as nuclear, oil and gas become prohibitively expensive. Technically, this could be achieved by transmitting price information along with electricity: for example, if a consumer chooses to run their energy-intensive tumble dryer on an overcast calm day when local wind and solar power stations aren’t producing much power, they will rightly have to pay more for their electricity at that point in time.
  3. Develop local energy supply networks, fed by small scale distributed power generation systems. This would be cheaper than the national grid, and less prone to failure.

Q3. The Energy White Paper left open the option of nuclear new build. Are there particular considerations that should apply to nuclear as the government re-examines the issues bearing on new build, including long-term liabilities and waste management? If so, what are these, and how should the government address them? (MAXIMUM 750 WORDS)

Nuclear fission power might be attractive, were it not for five key problems which have yet to be solved:

  1. Nuclear power is not carbon neutral
  2. There is no method for safely disposing of nuclear waste (Interestingly, waste disposal and clean up is currently funded by the taxpayer, rather than by users of the electricity generated through nuclear power. A true free market would give consumers a choice over where they bought their electricity from. Those who wished to purchase nuclear power could fund its waste liabilities by paying commensurately higher prices.)
  3. Mining, processing and delivering uranium fuel to the power station requires fossil fuel powered machinery. As the peak oil crisis deepens, these activities will become economically prohibitive
  4. Worldwide uranium supplies are already limited (industry is having to mine lower quality seams). A widescale switch to nuclear would deplete these seams very quickly
  5. The lead time for nuclear power stations is ten to twenty years, and therefore is not enough to plug a short-term energy gap

However, there is an alternative to fission power: nuclear fusion. Although not yet viable, nuclear fusion reactors, which harness similar reactions to those in the sun, could provide huge amounts of electrical power, without generating as much radioactive waste produced by fission reactors. I believe the government should increase its financial contributions to nuclear fusion research (but only after implementing renewable solutions). Although unlikely to pay off in the short term, the long term benefits could be enormous.

Q4. Are there particular considerations that should apply to carbon abatement and other low-carbon technologies? (MAXIMUM 750 WORDS)

Carbon sequestration (abatement) represents a poor alternative to a reduction in carbon emissions. Nature has already designed the world’s best carbon sequestration technology – trees. We should therefore maximise our woodland and forest cover worldwide by introducing policies mandating sustainable timber systems (such as woodland coppicing).

Furthermore, planning policy should be changed to require significant green spaces to be re-established in towns and cities, and to prevent the sprawl of housing estates over virgin countryside.

Q5. What further steps should be taken towards meeting the government’s goals for ensuring that every home is adequately and affordably heated? (MAXIMUM 750 WORDS)

There are many simple and effective steps we could take, including:

  1. Immediate removal of VAT on all energy-efficient insulation and heating products (alongside renewable technologies, goods and services in general)
  2. Consolidate the diverse range of home energy efficiency schemes that currently exist into a single national scheme, easily understood by everyone, and supported consistently over many decades with no funding gaps
  3. Continue ratcheting up the minimum insulation standards required of new-build in the Building Regulations; simultaneously expand the Building Regulations to mandate the incorporation of passive solar heating, along with off-grid energy and water supply systems; prohibit new housing developments from including car parking in order to minimise the carbon dioxide emissions generated by private transport
  4. Reward owners of low and zero carbon homes with financial incentives, such as reduced council tax

Comments are invited on the following issues as described in the text:

i. The long term potential of energy efficiency measures in the transport, residential, business and public sectors, and how best to achieve that potential (MAXIMUM 750 WORDS)

Energy efficiency measures could hugely reduce our requirements for energy in all sectors of the economy. However, the most difficult area to tackle will be our high demand for personal motor transport. The so-called ‘hydrogen economy’ does not offer a solution, as vast quantities of electricity will be needed to produce the hydrogen fuel.

The government must therefore reduce the need for private motor transport. One fundamental cause of excessive travel is the UK’s overpriced housing market, which forces many people to commute large distances between affordable accommodation and their workplaces.

ii. Implications in the medium and long term for the transmission and distribution networks of significant new build in gas and electricity generation infrastructure (MAXIMUM 750 WORDS)

As discussed above, we should not be building large scale centralised energy distribution networks. Our infrastructure development efforts should be focused at the local and regional level, supporting microgeneration projects.

iii. Opportunities for more joint working with other countries on our energy policy goals (MAXIMUM 750 WORDS)

Energy policy goals should remain within the state, simply because on the grounds of sustainability countries should source their energy supplies from within their own borders. By all means work with other countries where it advances our own goals. However, we do not need more joint research: we need implementation!

iv. Potential measures to help bring forward technologies to replace fossil fuels in transport and heat generation in the medium and long term (MAXIMUM 750 WORDS)

Again, a range of measures will enable the replacement of fossil fuels:

  1. A reduction in energy demand (see response to question 1) by implementing Tradable Energy Quotas (www.teqs.net)
  2. The provision of economic incentives to households to insulate and install their own generating capacity (e.g. removal of VAT on green products)
  3. Wide ranging cross-party support for renewable technologies, spanning successive governments

End of consultation questionnaire


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Solar Panels stolen from Brighton Earthship

An Alert: Solar Panels stolen from Brighton EarthshipSolar powered sound stage.

15 September 2006

The Brighton Earthship is a pioneering low carbon building project based in Stanmer Park, Brighton. It was built by the Low Carbon Network, and was the first to gain planning approval in the UK.

The Earthship demonstrates a low energy community-based approach to living, employing a wide range of green technologies, including passive solar, thermal mass, rainwater harvesting, and composting toilets. Powered by solar panels and a wind turbine, it can operate entirely off-grid. Unsurprisingly, its carbon footprint is very low.

Sadly, some thieves have recently stolen the Earthship’s solar photovoltaic panels. Read this alert issued by the Low Carbon Network Project Manager :

Unfortunately, a couple of nights ago some thieves stole 12 solar panels from the Earthship Brighton community centre.  The panels were Unisolar ES 62W, unbreakable solar electric panels and worth about £4K.  They are from the March 2005 batch and the serial numbers are listed at the end of this email.

If you hear or see anybody selling Unisolar panels in the near future please let us know and feel free to pass this message onto anyone else.

Serial numbers, all prefixed by ES-62T are: 02299, 02298, 02256, 02257, 02258, 02259, 02301, 02300, 02254, 02255, 02313, 02314

Please contact the Low Carbon Network if you come across these panels, or notify the police.

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My Carbon Footprint – 2006

My Carbon Footprint – 2006

23 January 2007

This article describes my carbon footprint for the year 2006 – the amount of carbon dioxide my lifestyle produced in that year. A carbon footprint is a vital tool for helping reduce our greenhouse gas emissions, and is an essential step on the way to a low carbon economy.

My footprint is low, because I have taken many measures to reduce my carbon dioxide emissions. However, it is not low enough to satisfy the Contraction & Convergence principles necessary to prevent dangerous climate change. Clearly, I must continue to reduce my footprint, and this carbon audit is an essential step on the way.

What is a Carbon Footprint?

A carbon footprint is a simple concept – it is the total mass of carbon dioxide emitted as a consequence of a person’s activities over a year. The figure is commonly cited in kilogrammes per year, or tonnes per year, depending on how large the number is.

Because so many different activities contribute to an individual’s carbon footprint, it is important to understand what has been measured when a figure is quoted. Without this understanding, it is difficult to compare footprints. For this reason you should also give a breakdown, as I have done below.

There is one other complication – carbon dioxide is not the only greenhouse gas that contributes to global warming. Among others, methane is the most significant gas, and is produced by landfill and cattle farming, to name but two. This has been taken into account for food consumption and waste production.

How I calculated my Carbon Footprint for 2006

To work out my 2006 Carbon Footprint, I measured these aspects of my lifestyle:

  • Electricity, gas and water consumption
  • Distance commuted, including mode of transport
  • Leisure journeys, including flights
  • Where I buy my food from
  • The amount of waste I produce that cannot be recycled.

For gas and electricity these figures were calculated from actual meter readings. I’ve divided these by two, to account for my share between the two of us living at home.

For travel to and from work, I’ve estimated the number of journeys made and their distance, then scaled that up by the amount of CO2 emitted for that mode of transport. I’ve used a similar approach for calculating the impact of leisure journeys.

Some figures are difficult to calculate directly, as they represent embodied energy, and hence embodied CO2. For instance, when buying food from a supermarket you may not travel any further than your local shops, but the food is likely to have been freighted up and down the country (one-third of lorries on the motorways are carrying food for supermarkets!).

Electricity: 0.08 tonnes CO2

In 2006 we consumed 1981 kWHr of electricity. Of this, 356 kWHr was from a non-renewable supplier, and the remainder from Good Energy, a 100% renewable supplier.

Each kWHr of non-renewable electricity creates 0.45 kgCO2 [Electricity], so 356 kWHr created 160 kgCO2. My personal share was half this, just 80 kgCO2.

Gas: 1.69 tonnes CO2

In 2006 we burnt 17804 kWHr of natural gas heating our home, hot water, and cooking. Each kWHr of natural gas creates 0.19 kgCO2 [Gas], making a total of 3383 kgCO2. My personal share was half of this, equal to 1691 kgCO2.

Water: 0.03 tonnes CO2

Water consumption is a good example of embodied CO2 – there’s no apparent production of CO2 when you turn the tap, but it takes a considerable amounts of energy for your water supplier to collect water, purify it, pump it to your home, pump the resulting sewage away, treat it and dispose of it! Each tonne of water processed in this way requires 0.91 kWHr of energy, causing 0.41kgCO2 [Water].

In 2006 we didn’t have a water meter fitted to our home, so I couldn’t directly measure water consumption. However, from previous figures collected when we had a similar lifestyle, this was around 12 tonnes of water per month, or 144 tonnes per year. Given that each tonne liberates 0.41kgCO2, our water consumption for 2006 was responsible for 59kgCO2. My share of this was 30kgCO2.

Commuting: 0.43 tonnes CO2

We don’t own a car, and make most of our journeys by public transport. I commute to work by train, a round-trip distance of 40 miles. In 2006 I made 150 return journeys to work, a total distance of 6000 miles.

I travel on a Class 153/1 diesel commuter train which produces, for every mile travelled, around 2.2 kgCO2 [Commuter Train]. However, my commuter service is rammed full of passengers (thanks to First Great Western), and carries around 50 passengers in two carriages (making this an energy efficient mode of transport, despite the discomfort). This means that my journey causes 1/50th of 2.2 kgCO2 / kilometre, which is 0.044 kgCO2 / passenger kilometre.

Travelling 6000 miles, or 9654 kilometres, my CO2 emissions were 0.044 kgCO2 / passenger kilometre * 9654 kilometres = 425kgCO2.

Leisure journeys: 0.40 tonnes CO2

I made no flights last year, having given up flying because of its environmental impact.

However, we occasionally hire a car to visit family or go on holiday, for which we travelled about 2000 miles in 2006. This car emits around 0.2kgCO2 / kilometre [Small car], or 0.3kgCO2 / mile, making a total of 667 kgCO2. For a journey made by two, my share is half this, or 334 kgCO2.

We also travel by InterCity train to visit friends and family, and covered around 1000 miles (1609km). An InterCity train emits 12.17 kgCO2 / kilometre [InterCity Train]. Assuming 8 passenger cars, each carrying 40 passengers on average, each train carries around 320 passengers. Each passenger is therefore responsible for 1/320th of 12.17 kgCO2 / kilometre, equivalent to 0.038kgCO2 / passenger kilometre.

Covering 1609 km in an InterCity 125, my CO2 emissions were 1609 * 0.038kgCO2 / passenger kilometre = 61 kgCO2.

  • Total leisure activity emissions = 334 + 61 kgCO2 = 395kgCO2.

Food and drink: 0.7 tonnes CO2

We buy most of our food from a local organic market stall, or from Riverford Organics‘ home box delivery scheme. We totally avoid airfreighted food, and minimise our consumption of exotic fruits (bananas are one thing we cannot give up, yet.). Our emphasis is on local food to minimise embodied energy.

The Independent newspaper [Food] reports that a typical UK resident produces 1.39 tonnes CO2 from food production and transport, both national and international. I estimate that local food production and consumption halves this figure, and on that basis, estimate my food and drink in 2006 caused 0.7 tonnes CO2 to be emitted.

Waste: 0.3 tonnes CO2

We compost all food waste. Over 2006 this rotted down to 15 large bags of top quality compost, used to mulch our raised vegetable bed. Glass, paper, tin foil, plastics etc. are recycled via the council’s recycling collection.

We are members of a local ‘freecycle’ email list, where members can swop unwanted items without charge. We recently gave away a filing cabinet we no longer needed – it found a new home in an office, instead of ending up as scrap, or worse still, landfill.

We also take care to buy good quality products that will last, even if they cost more in the first place. This minimises the energy cost of disposing or recycling an appliance or item.

I estimate my share of waste production at 0.3 tonnes CO2 for 2006.

Overall Footprint for 2006: 3.64 tonnes CO2

My 2006 carbon footprint was, in tonnes of CO2:

  • Electricity – 0.08
  • Gas – 1.7
  • Water – 0.03
  • Commuting – 0.43
  • Leisure journeys – 0.40
  • Food and drink – 0.7
  • Waste – 0.3

making for a grand total of 3.64 tonnes CO2. This is very low compared to the average UK citizen’s carbon footprint of around 11 tonnes CO2 per year [Independent Newspaper]!

Next Steps

Having selected a renewable energy supplier, given up flying, and using public transport, there are two key areas left for me to focus on:

  1. Minimising my gas consumption; and
  2. Growing more of my own food.

I intend to minimise gas consumption by taking the following steps (in this order):

  1. Fitting an energy-efficient gas condensing boiler;
  2. Installing a wood burning stove, and using biomass to heat the home (biomass is almost carbon-neutral);
  3. Fitting solar hot water panels.

In the longer run more radical steps will be needed, and will require support through favourable government policies. For example, at present I have to commute 6000 miles a year (or more) because I cannot afford to live where I work (in a major city). Clearly, the UK’s absurd overpriced housing market directly contributes to climate change, because it forces people to commute greater distances.

The solutions are simple, but require fundamental changes, such as a) regulating house prices (in much the same way that energy prices are regulated), and b) reforming UK planning law to allow ecological development (ie without cars, and in proximity to local jobs, food supply and services) across the country. However, neither of those measures are palatable at the moment, but doubtless climate change will alter this perception in time!


Appendix – Data Sources

Useful conversions

Kilometres to miles = 1.609


Source: Mayer Hillman, How we can save the Planet.


Source: Mayer Hillman, How we can save the Planet.


Correspondence with David Wilks, inventor of the Interflush water saving device (www.interflush.co.uk). He cited figures obtained by Sheffield University researchers 1998-9.

Commuter train

Data available from Final Report, Rail Emission Model, November 2001, produced for the Strategic Rail Authority by AEA Technology as follows:

  • Class 153/0 is one power car, emitting 1.415kgCO2/km
  • Class 156 is 2 power cars, emitting 2.234 kgCO2/km

My regular comuter train is a class 153/1 with two power cars (and no trailer cars), so I have assumed 2.2 kgCO2/km.

Intercity Train

According to the Final Report, Rail Emission Model, November 2001, produced for the Strategic Rail Authority by AEA Technology :

  • InterCity 125 produces 12.17kgCO2/km

Small car

Source data: manufacturers’ figures published below car adverts. These range from 120gCO2/km to 200gCO2/km. I have used the pessimistic end of the scale.


Independent Newspaper Saturday 9 December 2006 – cover page article ‘Your carbon footprint revealed’.

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Low Carbon Building Programme Funding Crisis

Low Carbon Building Programme Funding Crisis – Sign our E-Petition

12 March 2007

The UK government is slowly moving ahead with support for microgeneration, supported by the Low Carbon Building Programme, the successor to the Clear Skies programme.

The Low Carbon Building Programme aims to increase uptake of small scale distributed power generation systems, by providing up to 50% of the installation cost. The scheme has been very successful, and many householders have installed photovoltaics, wind turbines, biomass heating, ground source heat pumps, and so on.

Each month a tranche of grant applications are given the go-ahead. Unfortunately, despite the popularity of the scheme, and the government’s professed interest in averting climate change, this month’s funding allocation ran out in little more than a hour! This is causing chaos in the UK’s growing alternative energy supply market, and directly impacts the UK’s ability to lower its carbon emissions.

An E-petition has been launched:

We the undersigned petition the Prime Minister to properly support small scale renewable energy in the UK by ending the funding crisis of the Low Carbon Buildings Program Phase 1.

To help keep the UK government on track to meet its climate change obligations, sign this E-petition now!

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Carbon Savings in a Somerset Market Town

Carbon Savings in a Somerset Market Town (Frome)

13 July 2007


As the impacts of climate change on our daily lives become ever more apparent, and oil prices continue to rise, the case for energy descent becomes stronger.

While individuals can minimise their carbon footprint, and thus reduce their dependency on fossil fuels, the savings to be made become much more significant when carried out across a town.

This article highlights some carbon dioxide savings that the people of Frome – a Somerset market town – could make collectively.


Q1. If every Frome household who left their TV on standby, switched it off instead, how much CO2 and money would Frome save?

According to the 2001 census, the population of Frome = 24510

Assuming 3.5 people per household = 7000 households.

Assume 50% of these households have a TV that they leave on standby (the others switch them off, or don’t use a TV)

=> 3,500 households with a TV left on standby

Assume each TV is left on standby for 20 hours, and only used for 4, and that when in standby, each TV consumes 5W power.

=> Daily energy loss in Frome

= 3,500 households * 20 hours * 5W

= 350000 Whr

= 350 kWHr/day

Assume electricity costs £0.12/kWHr

=> Daily money wasted in Frome from TVs left on standby

= 350 kWHr * £0.12/kWHr

= £42/day

=> Annual money wasted in Frome from TVs left on standby

= £42/day * 365 days/year

= £15,330/year

Assume this electricity is generated from non-renewable sources, emitting 0.45kgCO2/kWHr

=> Daily CO2 produced in Frome from TVs left on standby

= 350 kWHr/day * 0.45 kgCO2/kWHr

= 157.5 kgCO2/day

=> Annual CO2 produced in Frome from TVs left on standby

= 157.5 kgCO2/day * 365 days/year

= 57487.5 kgCO2/year

= 57.5 tonnes CO2/year


Q2. If every Frome household avoided driving to the supermarket for their weekly shop, and went to the local shops on foot or public transport, how much CO2 and money would Frome save?

According to the 2001 census, the population of Frome = 24510

Assuming 3.5 people per household = 7000 households.

Assume 80% of these households shop once a week

=> Number of trips supermarket/week

= 80% of 7000 households

= 5600 trips/week

Assume each trip is a total distance of 2km (ie a fairly near by out-of-town, supermarket eg Sainsburys or Asda)

=> Weekly distance travelled by Frome households to supermarket and back by car

= 5600 trips/week * 2km/trip

= 11200 km/week

Assume the average car is reasonably efficient, and produces 180gCO2/km

=> Weekly transport CO2

= 11200 km/week * 180gCO2/km

= 2016 kgCO2/week

= 2 tonnes CO2/week

=> Annual transport CO2

= 2016 kgCO2/week * 52 weeks/year

= 104832 kgCO2/year

= 105 tonnes CO2/year

Assume car costs 20p/km to run (including fuel, insurance, tax, repairs, depreciation etc.)

=> Weekly transport cost

= 11200 km/week * 20p/km

= £2,240 / week

=> Annual transport cost

= £2,240 / week * 52 weeks/year

= £116,480

This figure is extraordinary. It shows the importance to the Treasury of tax on fuel – if the government extracts 50% of this revenue in tax (a not unrealistic figure), Frome residents are paying the Treasury over £50,000 a year, just to get to their ‘local’ supermarket!


Q3. If every household in Frome switched to a renewable electricity supplier, how much CO2 would be saved?

According to the 2001 census, the population of Frome = 24510

Assuming 3.5 people per household = 7000 households.

Assuming that the proportion who already use renewable electricity is less than 1% (ie negligible)

Assume that each household is reasonably frugal in electricity, and gets through 2 Megawatt hours/year, ie 2000 kWHr/year

=> Annual energy consumption

= 7000 households * 2 MWHr/household/year

= 14,000 MWHr/year

Assume this electricity is currently generated from non-renewable sources, emitting 0.45kgCO2/kWHr, or 450kgCO2/MWHr

=> Annual CO2 emissions from electricity consumption

= 14,000 MWHr/year * 450 kgCO2/MWHr

= 6,300,000 kgCO2/year

= 6,300 tonnes CO2/year

Frome would save approximately 6,300 tonnes CO2/year if all households switched to a renewable electricity supplier such as Good Energy.

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Small Scale PV System

A Small Scale Solar Photovoltaic SystemUnisolar US42 and US21 panels mounted on a simple aluminium angle frame, facing south angled for maximum winter power production.  Peak power output is around 60 watts.

4 August 2007

This article describes our solar photovoltaic (PV) system, designed to provide us with a degree of independence from the national electricity grid. This system will not reduce our carbon dioxide emissions, since we already buy our electricity from Good Energy, a 100% renewable supplier. However, by reducing our load on the grid, it will help the UK share out its existing renewable energy capacity among more customers, thus increasing the proportion of the UK’s electricity needs that can be met by renewable energy.

A standalone PV system also provides us with security of energy supply, and helps insulate us from rising energy prices.

Choice of PV system

Conventional solar PV systems are grid-intertie. They generate AC (alternating current) electricity that feeds into the house mains electricity supply. If you generate more power than you consume, the meter spins backward, as that surplus electricity flows back into the grid for someone else to use. By returning surplus electricity to the grid, no battery is needed.

However, there’s a major drawback of grid intertie systems: when the grid fails, then to ensure safety the PV system is automatically disconnected. This means that your house will no longer be able to use the electricity generated by your PV array while the grid is down. Thus, contrary to expectations, you have no independence from the grid.

A lesser – but nonetheless significant – drawback of grid-intertie systems is their requirement for costly power inverters. The more complex system components and wiring needed increases maintenance costs and the likelihood of failure.

The system I chose to install is entirely independent from the grid-supplied mains electricity, and is purely DC (direct current), operating at 12 volts. It feeds into a battery, which ensures electricity is available at nighttime when the PV array is no longer generating power. It is very simple, and should therefore be very reliable.

System Requirements

I’ve chosen to start off with a low power system, but designed it with expansion in mind. By measuring the system performance I can then decide whether to add more PV panels to generate more power. In order to do this, I need to be able to monitor the energy the array puts into the battery.

My initial system will consist of a custom 12V lighting circuit run throughout the house, powering 5 low-energy lightbulbs, each consuming around 11 watts. I anticipate running these lights for up to 4 hours each evening.

System Sizing

Assuming that all the light bulbs are switched on at the same time (which is rather wasteful), the maximum power for 5 bulbs, each consuming 11 watts, is 55 watts.

In the worst case, should I leave all these lights blazing for 4 hours, they will consume 4 hours * 55 watts = 220 watt hours each evening. At 12 volts, this energy is equivalent to 220 volt.amp.hours/12volts = 18.3 AmpHours.

This power will come from a lead-acid battery. The model I have is an Elecsol Carbon Fibre 110 AHr battery which, when fully charged, can supply 110 Amp Hours over a long period (likely to be 100 hours, a standard rating since lead acid batteries give out their charge most efficiently at low currents). Unfortunately I don’t have the data to calculate this battery’s capacity when supplying 18.3 amp hours over 4 hours; but it is likely to be more than enough.

The battery is charged by 2 Unisolar triple junction panels. These amorphous panels have a good overall efficiency in the overcast and cloudy conditions we experience in the UK. The panel power ratings are 21 and 42 watts, making for a total of 63 watts.

At our latitude in the UK, the average sunshine hours in the summer is around 4 hours – ie, each day we get a total amount of sunlight that is equivalent to 4 hours of midday maximum intensity sun. Over those 4 hours, the panels will generate a total of 252 watt hours; this is just sufficient to recharge the battery for the worst case scenario.

During the winter there will be considerably less sunlight, and I expect not to be able to run all the lights all the time.

Of course these numbers are just guidelines. The real life system performance is what counts – hence the need to collect data, before deciding whether to uprate the capacity.

System Design

A pair of solar panels feeds into a charge controller, which then regulates the battery charging. When the battery is fully charged, the charge controller disconnects the solar panels to prevent the battery from becoming overcharged.

The battery runs a set of 12 volt lights. For simplicity, and to keep system losses down, no inverter or voltage converters are used.

Solar panel mountUnisolar US42 and US21 panels mounted on a simple aluminium angle frame, facing south angled for maximum winter power production.  Peak power output is around 60 watts.

There are a variety of ways of mounting solar panels, including roof mount, pole mount and ground mount. To keep costs down, this system uses a ground mount. I’ve built an aluminum rack using 25mm L-shaped struts available from DIY stores. This holds the two panels together, and is secured to a strong wood/concrete fence post.

The panel is oriented south, and tilted to maximise winter gain, when there’s the least solar power available.


Morningstar Tristar 60 charge controller

A charge controller is a key system component. The model I’ve selected is the Tristar 60, made by Morningstar. It can handle up to 60 amps at 12, 24 or 48 volts.

The Tristar has an RS232 computer interface, through which the controller can be programmed, and the firmware updated. Later this year Morningstar plan to update the MSView software (available from their website) to include a data-logging facility.

The Tristar is solidly built, and has a five year warranty. Installation is fairly straightforward.


Fuses, circuit breakers and fuse box

I decided to use standard electrical components for the circuit breakers, fuses and fuse box, purchased from Newey and Eyre, a UK-wide trade supplier of electrical parts.

The fuse box contains a ‘DIN’ rail – a metal strip whose cross-section resembles a top-hat, onto which fuses and switches snap on and off, making installation straightforward 10amp French industrial type fuses are held in Ferraz-Shawmut fuse holders (see Newey and Eyre’s catalogue for details).

10amp fuses are used to protect the battery, PV charge controller and load circuits individually.



Elecsol 110AH batteryI selected an Elecsol 110AmpHour carbon fibre wet lead acid battery. This can supply 110AmpHours if discharged over 20 hours (ie C20 rating) or just under 5 amps continuously for a day.

The manufacturer claims this battery will give over 1000 deep discharge cycles, and that the carbon fibre matrix prevents sulphation when the battery is left discharged for a long period, or overcharged. The matrix also prevents the battery plates from buckling under high discharge currents, so this battery could be used for very high current applications – perhaps useful in future if I were to fit a large inverter and run a 2kW electric kettle.


WiringTristar 60 charge controller, with fusebox below

Wiring is a surprisingly complex area of solar PV installations, mainly because the type of cable needed is not easily available, except through specialist PV suppliers.

Most cable is designed for mains applications, which, because of its higher voltage, carries much lower current. In general, PV systems should use large diameter cables – eg at least 2.5 square millimetres, sized to the maximum current that may be carried, allowing for a safety factor (eg 25%). In general cables should be able to handle more current than the fuses are rated for, so that if an overload short-circuit occurs, the fuses blow before the cables overheat and melt.



Steca Solsum 11 watt energy saving lampA set of 12 volt Steca Solsum ESL 11 watt lamps are used to provide lighting. I also run a 12V fast battery charger, for keeping torches, digital camera etc. charged.




System Performance

Results so far over the summer months are good; the charge controller does a good job keeping the battery topped up, and there’s plenty of power available to keep the lights running. However, during the winter I expect there will be less surplus capacity as the daylight hours reduce, and the demand for electric lighting increases. Watch this space for an update.

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Raspberry Pi is here!

Like many up and down the country, I’ve been waiting for my Raspberry Pi since I ordered early March – and now it has arrived!

Spent Saturday getting it working.  Main challenges were finding a suitable USB power supply (there are at least six different types of USB plug – so much for standardisation!), preparing a Debian “Squeeze” distro onto a 2GB SD memory card (a 4GB class 4 Sandisk card didn’t work, but an older generic class 2 2GB card did), and finally, getting a working keyboard (for some reason an old but perfectly functional Mac USB keyboard exhibited ‘stuck key syndrome’).

Powered on.. usual Linux bootup text scrolled up.. typed ‘startx’, and off we go – a full 1920 * 1080 LXDE desktop, running on a 700MHz ARM PC with ‘only’ 256MB Ram.  And power consumption is around 5 to 7 watts I gather – absolute peanuts.

Great to see the pure days of ARM return; it’s an excellent instruction set, and yields nippy computers.  Now we need to cut the bloatware of modern computers, and return to something much leaner.

Something else about the Pi really strikes you – it feels different.  Watching a credit-card sized circuit board with two tiny chips and a bunch of connectors drive a full OS is a little uncanny.

Finally, my son loves the Raspberry Pi – he is very excited about using the GPIO pins to interface (via a buffer/IO board of some kind) with lego motors; a vindication of the educational goals of the Raspberry Pi foundation.

I think this piece of kit is going to be a game-changer.  Now embedded hardware is powerful and accessible, with wide support.  Will be really interesting to see where this goes!

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