Whilst visiting Slough Police Station (not "visiting") last night, I spotted this:
"burning fossil fuels has consequences" .... sounds much more sinister when it comes from The Plod ...
Thursday, December 11, 2008
Tuesday, November 4, 2008
Slough Heat map - more details
The ever-excellent Environment department at Slough Borough Council have shed some light on their new Heat Map.
It is very similar to the Haringey Heat Loss Map and most of the information on their site applies to the Slough one.
Basically:
- a plane flies overhead about 2 hours after sunset on a cold February/March night. It's done then so it's cold enough for people's heating to be on, but after the effect of the sun heating the roofing surface has faded.
- the measure is of how hot the roof is at that time. It clearly cannot know how hot the house is in the first place, so you can't make any firm assessment of how good the insulation is, just how much heat is being emitted at the time of surveying.
This means that a very poorly insulated house will appear "cold" if the owners are away and the heating off, and a very well insulated house look really "hot" if you're having a massive party and is full of people. Or you're one of the infamous Slough ganja farmers ...
There's a little bit more to it than that, but that's basically it. It's a very useful guide, but not totally accurate energy survey. But wait, Slough Council have thought of that, and are offering free energy checks for local residents, with subsequent help with insulation, by ringing 0800 043 9569. It's a relief to know that whilst some of the decisions of the planning committee seem to befar adrift from reality, other departments are getting to grips with the real problems in an effective way ...
Wednesday, October 29, 2008
Notes on Cippenham planning committee
Here's my view on how the decision was taken to refuse planning permission for Cippenham wind-turbine, at the Slough Borough Council planning committee meeting on 22nd October, 2008.
As my notes show, some of the committee members discussed some of these points - there's no getting away from it, the proposed turbine was very big and very close to people's homes. Whether the problems it might have caused would have been as big as they suggested, I'm not sure, but they were right to err on the side of caution. Wanting to be re-elected might have something to do with it as well, but that's the game. Fair enough.
However, what is more worrying is what seems to be a general lack of understanding of exactly what it was they were deciding upon. Every councillor declared themselves in favour of renewable energy, but only Cllr Plimmer asked to know what the council's strategy actually is on renewable energy, and wanted to know why it was there is no strategy. Other committee members seem happy to repeat myths and misunderstanding about renewable energy, and ignore the fairly clear rules about what their duties are in this regard:
- many of the councillors focussed on the identity and motives of the applicant, rather than the merits of the application, in clear breach of the rules of the committee, and despite being warned by the committee officers
- Cllr Dale-Gough persisted in perpetuating myths about the efficiency of turbines, which even if were true, are outside the bounds of consideration of a planning committee, according to Planning Policy Statement 22
- A number of councillors expressed what appeared to be genuine outrage that the turbine would be connected to the National Grid, rather than directly to local homes. Cllr Swindlehurst went even further, comparing the turbine because of this unfavourably against the Slough Heat and Power power station, on the Trading Estate, even though that too is connected to the National Grid (as is every other power station in the country for the last 80 years, including houses with solar panel installations). I've tried to see the logic, but how can you prefer one installation to another, when the point on which you say makes the difference is exactly the same?
So, an expected, but still depressing outcome. Whilst this particular application probably isn't right for the intended site, it is clear that those responsible for making the decisions are not that well informed about what they are deciding upon. Will they use the same duff criteria when assessing future applications? Or will there be a strategy for renewable energy (which almost all the councillors claimed to be in favour of)?
Below is brief notes on what each councillor said, along with my comments in italics. The first speaker was the officers report, then the 3 councillors for the affected ward, then the committee members.
Officers Report
Core strategy supports renewable energy, outweighs impact on the landscape, but not local amenity.
Noise - likely input, information insufficient.
Shadow flicker - would be intermittent, and significant in Marcia Court.
Safety - access below blades, and most sites usually open land/industrial sites - turbine would be on a major route that local people could not avoid.
BAA - no objections.
New evidence from developer, does not provide any reason for changing recommendation.
New information on noise could be grounds for appeal.
Cllr Parmar
Renewable energy is a good idea, which he is not against in principle, but is opposed to siting the turbine in an urban area, which is the "wrong place".
Article 8 of the Human Rights Act - the right to a peaceful family life.
Turbine (including blade at highest point) would be higher than the London Eye and Big Ben.
Shadow flicker - telling residents to close curtains would be "ridiculous"
No evidence of any site selection process.
Noise from turbine would be "frightening" and "overbearing"
No bird/bat or vibration assessment.
No data on collapsing pattern. Green Park site is designed to collapse away from M4 into "safe" landing area - no such point on this site.
Effect on House prices.
Flicker - negative effect on health/sleeplessness
Effect on radar
Core strategy supports renewable energy, outweighs impact on the landscape, but not local amenity.
Noise - likely input, information insufficient.
Shadow flicker - would be intermittent, and significant in Marcia Court.
Safety - access below blades, and most sites usually open land/industrial sites - turbine would be on a major route that local people could not avoid.
BAA - no objections.
New evidence from developer, does not provide any reason for changing recommendation.
New information on noise could be grounds for appeal.
Cllr Parmar
Cippenham Meadows - Labour
Renewable energy is a good idea, which he is not against in principle, but is opposed to siting the turbine in an urban area, which is the "wrong place".
Article 8 of the Human Rights Act - the right to a peaceful family life.
Turbine (including blade at highest point) would be higher than the London Eye and Big Ben.
Shadow flicker - telling residents to close curtains would be "ridiculous"
No evidence of any site selection process.
Noise from turbine would be "frightening" and "overbearing"
No bird/bat or vibration assessment.
No data on collapsing pattern. Green Park site is designed to collapse away from M4 into "safe" landing area - no such point on this site.
Effect on House prices.
Flicker - negative effect on health/sleeplessness
Effect on radar
This was despite just hearing from the Officer's Report that BAA had no objections.
Large petition from local residents/wind rats
Recomended refusal
Cllr Chohan
Cippenham Meadows - Labour
Started off a bit cheeky, speculating on the effect of the potential vibration on the bedrooms of his constituents.
Concerned about an overbearing "huge wind turbine". Did not think it appropriate for a local resident area, and that comparable turbines, eg Green Park, Reading, are not as close to houses.
Cllr Davis
Cippenham Meadows - Labour
Barratt Homes had not done the required research, and not concerned about local people. Suggested that a turbine should be close to the home of "Mr Barratt." Expressed opinion that "Barratt think that because it is Slough, they think they can do anything".
Planning decisions are supposed to assessed on the quality of the application, not the identity of the applicant.
Cllr Dale-Gough
Langley St Mary's - Conservative
Declared that wind-turbines are renowned for their ineffectivenees, and that there is no wind for 30% of the time, and have to be turned off in gales.
Whilst crowd-pleasing, this is inapplicable to this decision for 2 reasons:
1) It makes no sense to base a decision on "efficiency" of a turbine, when the fuel is free - http://www.bwea.com/ref/faq.html#efficient. Conventional coal power-stations are highly inefficient, losing a third of their energy during the process of burning coal to heat steam then cool it down again. Perhaps the councillor is confused with the "load-factor" - the proportion of energy the plant can produce compared to it's theoretical maximum.
2) It is irrelevant to the decision, according to Planning Policy Statement 22 key principle 6 : "Small-scale projects can provide a limited but valuable contribution to overall outputs of renewable energy and to meeting energy needs both locally and nationally. Planning authorities should not therefore reject planning applications simply because the level of output is small."
He then went on to say that a better site would be in the sewage works across the M4.
Perhaps a councillor for Langley, he could be excused for not knowing the geography of the part of the town he was talking about and making a decision on, but as a map shows, there are still houses close to his proposed site.
Vote
Large petition from local residents/wind rats
Recomended refusal
Cllr Chohan
Cippenham Meadows - Labour
Started off a bit cheeky, speculating on the effect of the potential vibration on the bedrooms of his constituents.
Concerned about an overbearing "huge wind turbine". Did not think it appropriate for a local resident area, and that comparable turbines, eg Green Park, Reading, are not as close to houses.
Cllr Davis
Cippenham Meadows - Labour
Barratt Homes had not done the required research, and not concerned about local people. Suggested that a turbine should be close to the home of "Mr Barratt." Expressed opinion that "Barratt think that because it is Slough, they think they can do anything".
Planning decisions are supposed to assessed on the quality of the application, not the identity of the applicant.
Cllr Dale-Gough
Langley St Mary's - Conservative
Declared that wind-turbines are renowned for their ineffectivenees, and that there is no wind for 30% of the time, and have to be turned off in gales.
Whilst crowd-pleasing, this is inapplicable to this decision for 2 reasons:
1) It makes no sense to base a decision on "efficiency" of a turbine, when the fuel is free - http://www.bwea.com/ref/faq.html#efficient. Conventional coal power-stations are highly inefficient, losing a third of their energy during the process of burning coal to heat steam then cool it down again. Perhaps the councillor is confused with the "load-factor" - the proportion of energy the plant can produce compared to it's theoretical maximum.
2) It is irrelevant to the decision, according to Planning Policy Statement 22 key principle 6 : "Small-scale projects can provide a limited but valuable contribution to overall outputs of renewable energy and to meeting energy needs both locally and nationally. Planning authorities should not therefore reject planning applications simply because the level of output is small."
He then went on to say that a better site would be in the sewage works across the M4.
Perhaps a councillor for Langley, he could be excused for not knowing the geography of the part of the town he was talking about and making a decision on, but as a map shows, there are still houses close to his proposed site.
Wexham Lea - Independent / BILLD Group
All for "Green Energy", but not in housing estates
Central - Labour
Is a full supporter of Renewable Energy, but "have to sensible".
It should be somewhere it doesn't affect people, and this site would cause a lot of problems.
Have to balance the benefits with the effects.
This would cause hazards to M4 users
As noted by several other committee members, the Green Park turbine in Reading is right next to the M4, with no obvious ill-effects.
Cippenham Green - Labour
Has no problem in principle with a turbine, and was quite excited when he first heard of the proposal, both as a landmark and the contribution to renewable energy it would make.
Believes these plans poorly executed, this is not the right site.
Believes that Barratt with their close working relationship with Eton College (who sold them the land) could have come up with a better site.
Believes that Barratt are using this as a way of milking more money out of the sports-pitches which they were required to provide as Section 106 benefits, and the turbine would reduce the usage of the sports pitches
Applications are supposed to be decided upon their merits, not by speculation on the motives of the applicant
Is concerned about the structure collapsing.
Believes the idea has potential, but suffers from "shoddy execution"
Renewable energy is valid, but should be elsewhere.
Could be interesting, is a blight
Then spoke about the Slough Heat and Power power station, on the Trading Estate. Described it as using "good fuel", and expressed desire for it to supply more power. Declared that SHP currently supply power for 7-8,000 homes, and that this was the best route for renewable energy expansion in Slough.
Up to a point - SHP use both wood and FibreFuel, which according to the front page of their website is "Materials which are non-recyclable and would otherwise be sent to landfill are thus turned into a valuable resource", but according to their "Raw Material s" page is made up of "mixed papers, magazines & junk mail, coated papers, laminates, adhesive labels, photographic paper, hygiene product rejects and pre-consumer packaging (not an exhaustive list)." So it's an incinerator, which is burning recyclable materials. But it's also a Community Heat and Power (CHP) power station, which reuse the heat produced in electricity generation for heating local homes. So sort of "renewable", as it's not using fossil fuels, but perhaps not sustainable in the long-term as it depends upon a supply of a large amount of waste material, some of which could be recycled. Perhaps Cllr Swindlehurst was referring to the forthcoming Grundon Incinerator in Colnbrook, which was the focus of so much protest a few years ago.
Foxborough - Liberal Democrats/BILLD Group
Asked if the council has any microgeneration strategy, as the officers haven't specified any details in the report?
strictly speaking, a 3MW turbine isn't really "micro", but it's a good question.
Officer Albertini replied that there is "broad support" for Renewable Energy, but there are no fixed standards
Cllr Plimmer considered that this kind of application is going to be coming up more often in the future, and that standards should be set now to avoid the committee having to make decisions on an undecided policy.
Officer Scourfield replied that there cannot be specific policies for everything, but the recommendation for refusal was based on general policies on amenity, safety etc. He suggested that policies may be formulated in more detail later.
Britwell - Independent Britwellian Residents / BILLD Group
Was amazed that the electricity produced will not go to Slough.
Whilst it would be nice to have an entirely local grid, this isn't how any power station in the UK works - they all link to the national grid, which then supplies homes through their own suppliers. I'm not really sure what difference it really makes, above the losses in transmission - it's not the same as buying local strawberries - "these electrons were made in Slough, see how the light burns brighter ...". That's not really how electricity works.
He then continued to talk about Barratts and their motivations for applying, to the point where Officer Wild had to intervene to remind him that applications are decided on their own merits, not the identity of the applicant.
Cllr Pantelic did not take the opportunity to speak, though as she was sat next to Cllr Swindlehurst, may have drawn breath in preparation before he spoke again
Cllr Swindlehurst reaffirmed his view that he wants local power for local people, and that it is better to use the Slough Heat and Power for local renewable energy needs.
As the SHP website makes clear, they have not built the infrastructure for a local electricity grid, but feed into the National Grid as "Electricity output is sold under a Non Fossil Fuel Obligation contract.". Exactly how the Barratt turbine would have. So Cllr Swindlehurst opposes the turbine on the way it redistributes its electricity output, in favour of another system that works in exactly the same way, but with less sustainable fuel and more emissions. That does seem a little odd.
Cippenham Meadows - Labour
Wanted to know how deep the foundations were going to be. Concerned about safety, the disabled day centre, playing fields and changing rooms.
Was pleased when she first heard at first that 1,500 homes were going to be built, which is approximately the amount of homes to be supplied by the turbine, so too was very surprised to find out the power was going to be fed into the National Grid.
Again, this is how all such systems work. No power station of any kind is able to maintain a constant supply of energy to meet the fluctuating demands of a single community, this is one of the design principles of the National Grid. By having a wide diversity of both sources and loads, the National Grid is able to "smooth out" any local fluctuations by a maintaining a much larger pool of electricity.
Wanted to know why solar panels couldn't be installed instead.
Good point, but no one solution is inherently better than another. Solar panels have a much lower output, are more expensive and so have a longer "payback" time. Of course, they do not work at night and are less effective in the winter when there is less sun available, and are not suitable for every house. There are very few, if any, installed in Slough apart from some very oddly positioned traffic ones. They're less intrusive, though this may not be the policy of the planning department - there does not appear to have ever been an application to install one in Slough. The long-term solution has to be a mix of solar, wind and other renewables, along with better insulation and energy efficiency in general.
The application was unanimously refused.
Monday, October 27, 2008
Slough Heat-loss map
SBC have published an excellent-looking "Heat Map" of Slough here.
Constructed from thermal imaging photos in March 2008, it claims to show the level of heat loss from all the houses in Slough. Potentially a great tool, but 2 questions come to mind ...
1) just when was the data gathered? To measure how much heat is being lost, the measurement has to be taken at a time when heat is being used within the house.
2) what does the scale 1-7 actually mean? Insulation is measured in "U" units - a measure of the way heat travels through a specific area - http://en.wikipedia.org/wiki/U-value#U-value
The SBC environment team are pretty friendly, and deserve full credit for organising this, so I hope to get some context for the data, pretty though the colours are .... tools like this are going to be increasingly more important as we try to close the energy gap - it's not enough to find new ways of generating energy, we need to reduce the amount we use too.
Constructed from thermal imaging photos in March 2008, it claims to show the level of heat loss from all the houses in Slough. Potentially a great tool, but 2 questions come to mind ...
1) just when was the data gathered? To measure how much heat is being lost, the measurement has to be taken at a time when heat is being used within the house.
2) what does the scale 1-7 actually mean? Insulation is measured in "U" units - a measure of the way heat travels through a specific area - http://en.wikipedia.org/wiki/U-value#U-value
The SBC environment team are pretty friendly, and deserve full credit for organising this, so I hope to get some context for the data, pretty though the colours are .... tools like this are going to be increasingly more important as we try to close the energy gap - it's not enough to find new ways of generating energy, we need to reduce the amount we use too.
Thursday, October 23, 2008
Cippenham turbine refused
As expected, the Slough Borough Council planning committee unanimously refused planning permission for the Barratt/Cippenham wind turbine last night.
More details later, but I made a submission for an adjournment. The council officers report was quite thorough in detailing many of the local environmental impacts, but failed (in my opinion) to reflect that "wider environmental and economic benefits, whatever their scale, are material considerations and should be given significant weight." - from Planning Policy Statement 22: Renewable Energy
As far as I can see, the wider implications weren't considered at all.
Hopefully they will next time though ...
More details later, but I made a submission for an adjournment. The council officers report was quite thorough in detailing many of the local environmental impacts, but failed (in my opinion) to reflect that "wider environmental and economic benefits, whatever their scale, are material considerations and should be given significant weight." - from Planning Policy Statement 22: Renewable Energy
As far as I can see, the wider implications weren't considered at all.
Hopefully they will next time though ...
P/08770/066- Land adj to extension of Eltham Avenue, Cippenham, Slough
To the Planning Committee, Slough Borough Council
I propose that the hearing for this application be postponed, as the Officer's Report does not take sufficient account of the wider context that this application has been made in, and fails to meet the required considerations, as required by Government Planning Policy Statement 22 (Renewable Energy). I suggest that a new report be written, taking all the relevant factors into consideration.
In particular, the report states that "the development is considered to have an adverse affect on sustainability and the environment". However, in section 7.1, it correctly quotes Government Planning Policy Statement 22 (Renewable Energy) as saying that "wider environmental and economic benefits, whatever their scale, are material considerations and should be given significant weight.". Unfortunately, at no point in their report do they mention what these may be. I believe that the report is therefore flawed, and should not be admitted as valid guidance until they have been addressed.
It appears to me that the author of the report has concentrated solely on *local* environmental issues (such as shadow flicker and noise), but has failed to address the *wider* issues at stake. My personal assessment of what these issues are:
*) fossil fuel methods of producing electricity emit significant levels pollutants. These include CO2, which the most recent IPCC report states quite clearly is responsible for growing levels of climate change, and must be reduced. Other pollutants, such as sulphur dioxide, are also produced.
*) the UK is legally committed to producing 15 of all it's renewables by 2020. This means that wind-power must contribute 36% of all the energy in the UK by that point - http://www.guardian.co.uk/environment/2008/oct/19/renewable-energy-greenhouse-carbon-emissions
*) the UK now produces most of it's electricity using natural gas. The UK's indigenous supplies of gas have now been more or less exhausted, making us reliant on Russia for our supplies
*) 5.4 million people are now living in fuel poverty (10% or more of their income being spent on fuel bills - http://www.uswitch.com/news/energy/energy/54-million-households-in-fuel-poverty.cmsx Whilst this is a probably not much of a consideration for the kind of people who worry about house prices, a sizable proportion of Slough's population fall into this category, and a development of this nature will start to help them. This must be one of the core concerns of local government.
*) The UK is committing itself to reducing CO2 emissions to 80% of 1990 levels by 2050. Projects such as this are essential to this happening.
In short, the political climate is changing faster than the environmental one, and whether we like it or not, projects such as these are going to be not only more common, but in all likelihood *compulsory* in the future. Subject to the developers meeting the relevant concerns raised, and making commitments to improve energy efficiency in the local area, I personally believe this project should be approved.
However, since the report fails in its duty to provide a proper assessment of the "wider environmental and economic benefits" of the project, it seems only right that this hearing be put back until a period in which a valid report can be produced.
many thanks
Toby Evans
Friday, October 17, 2008
Refusal recommended for Cippenham windfarm
The Cippenham wind turbine has been recommended for refusal of planning permission, at the forthcoming planning committee meeting on Oct 22nd:
The residential amenity of nearby existing homes will be adversely
affected by the size of the turbine and its proximity to those homes in
terms of visual amenity and sense of it being overbearing.
Consequently the proposal is not in accordance with The Adopted
Local Plan for Slough 2004 Policy EN1 (Design) and Policy 9 (Built
Environment) of the Local Development Framework Core Strategy
(Submission) November 2007 (confirmed sound August 2008).
16.0 PART D: LIST OF REFUSAL REASON(S)Reason(s)1. Visual Amenity
The residential amenity of nearby existing homes will be adversely
affected by the size of the turbine and its proximity to those homes in
terms of visual amenity and sense of it being overbearing.
Consequently the proposal is not in accordance with The Adopted
Local Plan for Slough 2004 Policy EN1 (Design) and Policy 9 (Built
Environment) of the Local Development Framework Core Strategy
(Submission) November 2007 (confirmed sound August 2008).
2. Noise
The noise assessment is inadequate to judge the impact of noise on
residential property. Consequently it is unclear if Planning Policy
Guidance 24 (Noise) and policy 8 (Sustainability and the
Environment) of the Local Development Framework Core Strategy
(Submission) November 2007 (confirmed sound August 2008) can be
complied with.
3. Shadow Flicker
The assessed shadow flicker will have an adverse affect on residential
amenity such that the proposal does not comply with policy 8
(Sustainability and the Environment) of the Local Development
Framework Core Strategy (Submission) November 2007 (confirmed
sound August 2008) in terms of quality of design.
4. Safety
The rotor blades oversailling of a public highway, proposed public
building/car park and public recreation area is considered to be a
potential safety hazard or perceived hazard which is poor design and
will hinder use of these public recreation and transport facilities.
Consequently the proposal does not comply with The Adopted Local
Plan for Slough 2004 Policy EN 1 (Design) nor Policy 8
(Sustainability and the Environment) of the Local Development
Framework Core Strategy (Submission) November 2007 (confirmed
sound August 2008) in terms of quality of design.
It's a difficult one - it's a big turbine, and the proposed site is pretty close to the nearest houses- but there's an energy crisis looming, and we need to maximise all our opportunities for alternatives to dwindling and polluting fossil fuels. Turbines are still new and relatively unknown, it'll be interesting to see if and how public opinion changes.
5. TV reception
The need for mitigation measures to ensure television reception for
homes west of the site is not affected has not been fully agreed nor
secured such that the proposal is unacceptable. Consequently the
proposal does not comply with Planning Policy Statement 22
Renewable Energy companion guide.
The recommendation seems mainly on grounds of "amenity", but that does seem to miss the bigger picture - increasing numbers of people in fuel poverty, and the potential catastrophic effects of climate change, both of which would be allieviated by projects such of this. They don't seem to have been considered at all. Where is the 80% cut in carbon dioxide emissions going to come from if we don't start making some hard decisions?
But the meeting still hasn't happened, so lets see ...
Monday, August 25, 2008
Cippenham Wind-farm
There's a proposal for a new wind-farm just down the road, in Cippenham, about here.
A letter in the local paper last week (Slough Observer 22/8/08), pretty much the first comment there's been on the proposal, used figures from the local opposition group WindRats to say both that the developer would be making nearly £3m a year from the proposal (assuming full capacity) and that the wind speed is so low in the local area that it wasn't worth bothering with. Which is it?!
As usual, the truth lies somewhere these points (though in normal debate, different sides, not the same, tend to make the contradictory statements). Here's my letter and the workings behind it:
OK, the maths.
This is based on the formula given in the Beurskins and Jensen article "Economics of wind-energy, Prospects and Directions" in the July/Aug 2001 edition of "Renewable Energy World". It looks to give an estimate of the energy available from a particular wind-turbine site. It's only an estimate, and you need to do a proper site survey and then match that to the exact specifications of the turbine you intend to fit. But it gives you an idea.
The turbine is sited at grid reference SU946797 (SU9479), which from the UK Wind Energy Database gives an average wind speed at 45m above ground level (agl). However, the actual turbine will be higher than that, so the developers suggest a speed of 6.4 m/s
The basic formula is :
Annual energy production (kWh) = K Vm3 At T
Nice. What this actually means is:
K = 3.2 = a factor based upon the relationship between standard turbine efficiency and wind-speed distribution.
V - is the cube of the average wind-speed for the site. This is the key, wind-energy is all based on the fact that the energy you get is all based on the cube of the wind-speed. This means you don't get much to start with, but it starts to rise rapidly as the wind-speed increases. For our basic speed of 5.8 m/s this is 195, 262 for the higher estimate.
A - the swept area of the blade. It's expected to be 90m diameter, so that's 45 m radius, which is (PIr2) 6352m2
T is the number of turbines, which in this case is one.
So, multiplying those together, we have either:
3.2 * 195 * 6352 * 1 = 3,972, 512 kWh (3,972 MWh / 3.972 GWh) per year, or
3.2 * 262 * 6352 * 1 = 5,337, 294 kWh (5,337 MWh / 5.337 GWh) per year
To put this in some sort of context, the average household uses 4478kWh p/year of electricity, so dividing the total amount of energy expected to be produced by this household average tells us how many houses could be powered by the turbine, between 887 and 1192.
Measuring CO2 emissions and what might be saved is a bit of dark art, depending mainly on which energy source you say you're replacing (measuring against coal makes you look good, hydro less so, the most recent energy mix is the fairest, but it's still a guess), but the latest figure I've a respectable source for is 0.527kg for each kilowatt hour of energy generated.
So, to calculate the theoretical amount of CO2 saved, multiply the expected energy generation from the turbine by this figure of 0.527kg, giving a figure of between 2,093,513.58kg (2094 tonnes) and 2,812,753.82kg (2,812 tonnes).
This is pretty much in line with what the developer estimates (section 3.12, page 9) for a Vestax 3MW turbine.
And it's both a lot smaller and cleaner than the Slough Estates CHP/incinerator and the now-legendary Colnbrook incinerator ...
A letter in the local paper last week (Slough Observer 22/8/08), pretty much the first comment there's been on the proposal, used figures from the local opposition group WindRats to say both that the developer would be making nearly £3m a year from the proposal (assuming full capacity) and that the wind speed is so low in the local area that it wasn't worth bothering with. Which is it?!
As usual, the truth lies somewhere these points (though in normal debate, different sides, not the same, tend to make the contradictory statements). Here's my letter and the workings behind it:
Tom Williams (Letters last week) states that his opposition to the proposed Cippenham wind turbine is based upon available sourced data, so perhaps his opposition could be turned into support. He rightly states that the average annual wind speed for the proposed site is just under 6m/s, a speed which would, from the manufacturers own statistics, produce about 0.25MW. This is only about one twelfth of it's maximum power (though Mr Williams and the Windrats.com website seem to assume 100% production when coming up with their £2.7 million figure), but this is only part of the story.
As any driver knows, wind-resistance increases significantly more the faster you get, requiring more petrol to accelerate from say 70-80 mph than from 20-30mph. This explains the difference in design between the Volvo and the Porsche. Happily, this effect also works in reverse - the faster the wind blows, then proportionally more energy a turbine can extract from the wind. In practice, what this means is that you cannot get an accurate estimate of the potential output of a turbine from the base average wind speed alone, but would need to survey the actual speeds on site over a period of months. I have no idea if this research has been done, but by using an estimation method used by the wind-energy industry, I calculate that this site and turbine would produce over 5000MW hours of electricity per year, enough for about 1200 houses and saving nearly 3000 tonnes of carbon dioxide emissions in the process (the exact workings available at 2cheap2meter.blogspot.com ).
As these figures approximately match the developer's figures, I hope that Mr Williams will now join me in giving support to this proposal on economic grounds. Wind-power is going to become more common as we struggle to meet our rising energy demands from dwindling and polluting resources such as gas and coal, and to me are far preferable to the "energy-from-waste" incinerators currently operating on the Trading Estate and soon in Colnbrook.
OK, the maths.
This is based on the formula given in the Beurskins and Jensen article "Economics of wind-energy, Prospects and Directions" in the July/Aug 2001 edition of "Renewable Energy World". It looks to give an estimate of the energy available from a particular wind-turbine site. It's only an estimate, and you need to do a proper site survey and then match that to the exact specifications of the turbine you intend to fit. But it gives you an idea.
The turbine is sited at grid reference SU946797 (SU9479), which from the UK Wind Energy Database gives an average wind speed at 45m above ground level (agl). However, the actual turbine will be higher than that, so the developers suggest a speed of 6.4 m/s
The basic formula is :
Annual energy production (kWh) = K Vm3 At T
Nice. What this actually means is:
K = 3.2 = a factor based upon the relationship between standard turbine efficiency and wind-speed distribution.
V - is the cube of the average wind-speed for the site. This is the key, wind-energy is all based on the fact that the energy you get is all based on the cube of the wind-speed. This means you don't get much to start with, but it starts to rise rapidly as the wind-speed increases. For our basic speed of 5.8 m/s this is 195, 262 for the higher estimate.
A - the swept area of the blade. It's expected to be 90m diameter, so that's 45 m radius, which is (PIr2) 6352m2
T is the number of turbines, which in this case is one.
So, multiplying those together, we have either:
3.2 * 195 * 6352 * 1 = 3,972, 512 kWh (3,972 MWh / 3.972 GWh) per year, or
3.2 * 262 * 6352 * 1 = 5,337, 294 kWh (5,337 MWh / 5.337 GWh) per year
To put this in some sort of context, the average household uses 4478kWh p/year of electricity, so dividing the total amount of energy expected to be produced by this household average tells us how many houses could be powered by the turbine, between 887 and 1192.
Measuring CO2 emissions and what might be saved is a bit of dark art, depending mainly on which energy source you say you're replacing (measuring against coal makes you look good, hydro less so, the most recent energy mix is the fairest, but it's still a guess), but the latest figure I've a respectable source for is 0.527kg for each kilowatt hour of energy generated.
So, to calculate the theoretical amount of CO2 saved, multiply the expected energy generation from the turbine by this figure of 0.527kg, giving a figure of between 2,093,513.58kg (2094 tonnes) and 2,812,753.82kg (2,812 tonnes).
This is pretty much in line with what the developer estimates (section 3.12, page 9) for a Vestax 3MW turbine.
And it's both a lot smaller and cleaner than the Slough Estates CHP/incinerator and the now-legendary Colnbrook incinerator ...
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