Earth Notes: From the Inbox (and Outbox) 2010

Emails and queries from readers.
Emails and queries from readers.

See also:

I receive a stready stream of emails about the site, some of which I expand into stand-alone articles (eg Going Green in Newcastle-Upon-Tyne and Solar PV in Diffuse (Cloudy) Daylight) and others of which I follow up privately. Also, I've sent unbidden an email or two to register an opinion...

Below you will find some other interesting brief interchanges (edited as necessary); I hope that you find them useful.

Going Solar in North-West UK

Jason Garner sent me an interesting email on going solar at home headed "Powering a 5W Deltech 12V LED Bulb Using Solar Power: Help!"

Read some of our exchange.

General Permitted Development Rights for Air-Source Heat Pump

Where I live (London) as of November 2009 it is still necessary to obtain planning permission to install an air-source heat-pump, which clearly adds red tape, uncertainty and cost to getting one. The main issues still at odds are the looks and noise of ASHP which could prove very contentious especially in densely-populated urban areas. As of 2009/11/17 the UK Government is consulting on streamlining the process.

I submitted the following query:

May I make one suggestion or get some clarification?

We would like to replace our band-D gas combi with an ASHP equivalent (probably Eco-Cute-style CO2 refrigerant) but we have a very small (end-of-terrace) house so unless mounted at the back, well away from where it is needed, an external unit could be visible from a road for someone sufficiently determined.

(The optimal mounting I suspect, would be on our side wall, but that could be glimpsed from a road with effort.)

We already have extensive PV (indeed we are net generators) and the local authority has been very supportive of renewables, but it would be important to me to have some more clarity in what counts as "Not permitted if visible from and sited on an elevation which fronts a highway." so that we and the local authority could be happy that we were within the law. Would insertion of "clearly" before "visible" be the right sort of change?

Laundry Detergents for Cold(er) Clothes Washes

Given that most of the energy consumption of a typical UK domestic wash cycle is in heating the water, but compared to North America cold-wash detergents are hardly available here, I wrote to P&G to ask about the low-temperature performance of the new Fairy non-bio gel and received a quick response on 2009/04/06:

We appreciate not all washing machines have a 15o wash cycle, however you will get brilliant cleaning performance at low temperatures when using a cold cotton wash cycle (NOT the delicate/hand wash cycle though because of the much lower level of agitation). Fairy Gel contains technologies that are active from very low temperatures (15o) however the performance is also excellent at higher temperatures such as 30o or 40o. We do recommend you to try Fairy Gel at a low temperature if you can, using a cotton cold wash cycle, as it should give outstanding cleaning results and extra consumer and environmental benefits such as: less product to dose, less energy per wash, less packaging waste, easier to carry, store and dispense at home, less CO2 emissions and reduced transportation costs hence, a lot of benefits for you as well as for the environment.

I asked for clarification if P&G would recommend Fairy non-bio gel for the cold wash and I received this reply:

We wouldn't recommend that it is used on a cold cycle, only on a specified 15 degree cycle, as we know the temperature can vary depending on the season.

Note that P&G have another range, US-targeted, with a much lower minimum wash temperature than the UK/EU brands ("P&G Tide" email response 2009/08/18):

Tide Coldwater is able to perform in temperatures as low as 40 degrees F (4 degrees C). If the water in your washing machine is below 40 degrees F (4 degrees C), add a bit of warm water to bring the temperature to that level before adding your clothing.

I would very much like to try this or the "Tide Coldwater HE" variant for "High Efficiency (HE)" front-loaders.

Unfortunately the official UK response to my request for where to buy or sample Tide Coldwater or equivalent in the UK (2009/08/25) is:

I am sorry to inform you that Tide is not currently available in the UK or Ireland.

The various P&G companies around the world each manufacture and market products designed specifically to meet the needs and preferences of consumers in their own regions. However, we do constantly review the range of products available in the UK and Ireland and do welcome your comments as a helpful addition to our consumer research.

I'm very sorry to disappoint you, but thank you again for getting in touch. Consumer feedback is really important to us so we've passed on the details of your message to the relevant department.

to which I responded:
Please let your marketing people know that (a) I am disappointed, clearly and (b) that I am forwarding this correspondence to Ed Miliband at DECC, as an example of market failure given that laundry water heating probably accounts for many percent of UK total energy consumption and that P&G will not make its existing energy-efficient brands available in the UK market.

On the back of P&G's unsatisfactory reply I sent the following to their main competitor, Unilever (2009/08/25):

I am trying to source a domestic laundry detergent that will work well in a cold wash year-round (ie down to ~9C in winter). P&G seems unable or unwilling to help as its primary UK Ariel Excel gel brand is only rated to 15C and they will not sell their US-brand Tide Coldwater (HE) product (good down to 4C) here.

Can you do better and point me to a UK brand that will work at 9C?

(As you are aware, ~90% of the energy in a typical UK domestic wash is heating the water. We are trying to reduce our carbon footprint but are only able to do about 20% of our washes cold right now due to inadequate detergents. Not selling such an energy-saving existing brand here seems very poor from an environmental and PR point of view and I already made my annoyance at this market failure clear to Ed Miliband today.)

And Unilever's response 2009/09/01 was far more satisfactory:

I wanted to let you know that any of our liquid detergents (NOT CAPSULES) will work at low temperatures, although it is worth noting that while they will work at low temperatures performance will not be as good because performance increases proportionately to an increase in temperature.

This is why we advise 30 degree washes-not because our products don't work at lower temperatures (they have been tested to work at temperatures as low as 10 degrees) but because performance is better from 30 degrees up.

We've been trying various detergents and wash temperatures in our new washer/dryer that will wash in cold water, and now maybe only 30% of our washes are at 40°C or higher (in summer) with about 50% at 30°C and the rest cold. Altogether this probably amounts to as much as a 50% energy saving.

AccordGuy's Off-Grid Solar in Crawley, UK

I received this from AccordGuy 2009/04/02 (AKA SolarBodge), who seems to have been having a lot of fun:

I've been following your pages for a year or so, and at the same time last autumn started to build my own off-grid system.

I started because my company chucked me out of my office and lots of us have to work from home now. I saw some cheap solar panels on sale at Maplins and had some bits and bobs like an old leisure battery and a 150W inverter kicking around the shed to build a simple system. I thought, how difficult can it be to power a 30W laptop from solar power if I'm going to have to work at home?

I'm now up to about 600Wp with the purchase of a pair of Sharp ND170 poly panels plus about 260Wp of those cheap amorphous panels from Maplins. I run a 220Ah 24V battery bank and a 1kW pure sine inverter. In the recent sunny days I've been able to use about 1kWh of sunshine and battery power each day and expanded the system from just the laptop and some table lamps to powering my whole house lighting circuits with a change-over socket for those circuits. I can choose grid or solar power for those two lighting circuits but haven't had to use grid power now since about mid-February.

My in-laws in Japan are all solar mad as well! My sister-in-law installed a 3kW Sharp system while my father-in-law installed a 5kW Sanyo system.

Where I live in Crawley, I've just this week noticed a big array go up on one of the blocks of flats near by. Curiously, they didn't use the sloped roof to mount them but rather steeper angled frames built on the flat sections of the rooftop. Either they are trackers or it wasn't allowed to mount them on the tiled roof.

Anyway, keep the updates coming. It's interesting to watch your plans develop.

I've got some of those Maplin panels too: when they're on sale at ~£4/Wp they are difficult to resist. Can you say renewable retail therapy?

House Pressure-Testing

In connection with my item about pressure/leak testing my house with a view to heating energy efficiency, I was asked a few questions:

Where I live (no heating needed) if there is no outside air flowing in and out the natural way, the house feels unlivable and stuffy... Different perspective I guess.
What's your position on air vents? I understand that they are mandatory if there are gas appliances, but they seem to completely undermine some of the insulation changes. Our lounge has a gas point that has never been used, because of this we have an air brick that was incorporated when the house was built - it's papered over because we couldn't live with the draft.

You have to (by UK building regulations) have enough efficiency and insulation elsewhere that you can afford the loses that go with adequate ventilation...

Part of UK building regs (Part F, I believe) deals with ensuring that there is adequate ventilation in the building, eg to avoid condensation/mould, and more dramatically sufficient oxygen to avoid CO (carbon monoxide) poisoning in rooms with an open flame such as a gas cooker.

Or you can do it the German 'PassivHaus' way and have an air-tight house with mechanical heat-recovery ventilation (MHRV) that ensures that the air changes frequently (is exchanged with outside air) but keeps the heat in the house.

We simply won't get as air-tight as PassivHaus here but the closer we get the more I shall have to think about 'trickle vents' and single-room or whole-house MHRV. We may well try MHRV in the bathroom first as our mould is starting to demand its own parliament and land rights.

So you fill the house with air like a balloon and measure the rate of pressure drop?

The test has to be done with planned ventilation blocked and is looking for unplanned leaks, eg from a heavy-handed workman cracking an otherwise airtight panel.

We did both under- and over-pressure tests (the latter are avoided if the house has chimneys full of soot!) and flow rate is measured while a constant over/under pressure is maintained by a fan. Only about 0.05%, so the same as a strong wind blowing through an open door.

(Note that in the US the process of reducing unwanted heat loss/gain due to unplanned air leaks is often called "weatherization".)

And Chris Benson wrote to me again with related experience:

I've recently bought for each of our 8 (unused) chimneys and have 5/8 installed. (Buried in the ash, cement dust and bird droppings I found that several of the fireplaces would have had closable flaps originally, but these are long gone :-()

They've made a considerable difference: no more rain/hail/soot/ash/bird[droppings] landing in the fireplace and bouncing onto the carpet/rugs, (presumably that will land if/when I remove them). And of course much reduced wind and bird noise. Some wind noise is still there: though now it's more like the sound from blowing across the neck of a bottle.

The balloons should still allow some air to pass to allow ventilation of the room and the chimney.

I had been wondering about getting the house pressure tested once I had done something about the glaringly obvious leaks: So now I know what to look and ask for!

And later, discussing why it may be hard to get good 'green' work done:

I've been thinking lately about the skills gap in green-building:

  • there's some new knowledge to be learned (often replacing existing ways of doing things which is going to make learning harder)
  • there's some trial and error required to find the pros and cons of different materials and techniques
  • materials and techniques are changing relatively quickly
  • different situations will require a range of materials and techniques depending on internal/external, construction method and materials, budget, legal restrictions, ...

It seems to me that the chances of getting and maintaining enough experience in any one area is going to be hard for most builders when most customers will be asking for the cheapest cost and damn the insulation...

G83-Lite Suggestion to Ed Miliband of DECC

Email to the Minister of Energy and Climate Change, Ed Miliband, 2009/03/28, subject "Suggestion for DECC for G83-lite":

I'd like to suggest creating a new light-weight form of the current G83/1-1 microgeneration spec/rules to allow consumers to connect very cheap and simple (and safe) microgeneration devices to the grid partly to help allow more urban area to contribute to renewables, and partly to get mindshare for more householders, eg renting, tower-block inhabitants, and other currently-excluded groups, to enable them to "be part of the solution" in at least a small way.

I've written up a little more detail here:

True UK Grid CO2 Intensity (kgCO2/kWh)

Paul Street of the London Development Agency wrote 2008/11/21 to point out:

You reference 0.43kgCO2/kWh (from Defra). This is the governments aspirational long-term target for grid carbon factor. And has little basis behind it. It would be better to use the Defra 3 year rolling average figure (currently 0.52kgCO2/kWh) which is far more representative of the current grid factor. Of course we all hope the grid factor will go down to 0.43 and beyond one day.

I'm looking at varioations and the mean intensity in the UK grid too.

In June 2009 John Stott wrote to me:

I notice you refer to various official average grid intensities in your note on variations in grid intensity.

A year or so ago, Carbon Offsetters used 430g/kWhr which you describe as an aspirational marginal cost. I have also seen 430g/kWhr used in a DEFRA Act on CO2 document circa 2007 or 8. Now the offsetters and carbon trust say about 530g which you describe as the rolling average. The latter I understand but the meaning of aspirational marginal cost is not clear to me. Is there a simple explanation of this term and why should DEFRA/ Carbon trust and the offsetters suddenly change to the higher value? Perhaps I should ask if you can say why they used the lower value since using the rolling average seems reasonable to me.

And my rather weak response is:

The government apparently aspires to the 430g figure for a marginal increase/decrease in consumption based on projections done some time ago and based in part on extrapolating the effects of the "dash for gas" if I understand correctly. And the marginal cost may not be the mean if the time of deferral or extra use is consistently at some part of the day with an intensity above or below the mean...

There have quite reasonably been other figures used concurrently, for example a higher value in Part L of the Building Regs I think for energy import deferred by microgeneration or somesuch.

And if, for example, you cared only about energy consumption in (say) winter for heat-pump based domestic space heating when grid CO2 intensity is higher then you'd maybe pick a higher value than the rolling mean I think.

One exercise I intend to attempt is a study of our month-by-month electricity CO2 emissions allowing for the hour of day of our typical consumption and microgeneration, intensity of the grid at that time...

But I think the short answer to your question is that I do not know for sure what goes on the in [the] minds of civil servants...

Generation at Existing Historic Tidal Mill Sites?

Tidal generation might be a very useful source of electricity for the UK, in part because it is predictable long in advance (unlike wind for example) even if still not (fully) 'demand callable' like fossil fuel generation. Having seen an item about Thorrington tide mill in Essex I wrote to Essex County Council 2008/11/09 asking if it had considered generating electricity and if that would indeed be possible without damage, etc.

Geoffrey Wood (Mills Support Officer) kindly wrote back as follows:

Your query referenc[ing] the possibility of generating electricity at the mill is one we are often asked. The short answer is that we have no plans to pursue the idea based on several factors.

  1. The mill pond is fresh water from Tenpenny Brook and is used for irrigation of crops.
  2. The tide gate is permanently closed to prevent saline water entering the pond and polluting the fresh water.
  3. Water is used from the mill pond to demonstrate the working of the waterwheel very sparingly; the majority of the mill pond is for irrigation.
  4. Models have demonstrated that the present existing machinery would have a very short life and would require constant hourly maintenance and repair.

The economics of producing electricity are just not practical using a 19th century machine with 21st century technology.

Thanks for asking the question though.

Letter to Mr Miliband at DECC

Ed Miliband has been made minister at the new UK Department for Energy and Climate Change, whose mere existence signals the connection between our energy use and what it is probably doing to the planet.

I sent him the following email 2008/10/13 entitled "Two Quick Green Actions":

Dear Mr Miliband,

Firstly, I wish you well with your new portfolio: it is a real opportunity to [do] good and you will need a will of iron to make progress in the face of brickbats and mad suggestions for perpetual-motion machines and punitive destruction of Big Oil, etc!

I have two of my own nutty suggestions for you, but I hope that these might be 'low-hanging fruit' that not involve money, only administrative fiat.

1) Ofgem seems rather to have lost the plot as to the benefit of real new build of renewables rather than shuffling certificates around, according to Dale Vince of Ecotricity:

I have no particular objections to shuffling of certificates as a secondary activity and have worked with energy traders fairly recently, but Ofgem surely is wrong-headed to regard Ecotricity's *50%* renewable generation for their own customers from their own plant as less green than their rivals' shuffled extant power which looks like a sop to the interests of the large providers and not in the customers' or planet's interests. Maybe you could persuade them to revisit their thinking? "You can get much farther with a kind word and a gun than you can with a kind word alone. Al Capone"

2) Instant CO2-emission savings from UK grid generation this (and each) winter without spending money.

The nub of my suggestion is that grid electricity is most likely at its most carbon-intense when the very maximum demand is being serviced in the weekday winter peak 4pm--9pm since probably almost everything that can run has to, however dirty, so use demand control (as was applied by the DNOs at the request of National Grid in May when Sizewell tripped off for example, primarily voltage reduction in distribution) during those peaks to help shift demand away from the peaks and to within the capacity of less-CO2-intense generation.

If this mechanism works it might be an indication that longer-term Dynamic Demand would be a useful CO2-reduction tool as well as its more usual 'grid balancing' and intermittent-generation-friendly behaviour, eg see:

I hope these are of some interest.

Wind Energy Planning

Vicky Portwain wrote 2008/10/21 to say:

I have just set up an independent web-site called

The web-site has the aim of creating a forum where people can gain some further information about renewable energy but also to share their thoughts, actions and experiences, for example - my next post is going to be an interview with a someone who bought his own 6kW turbine and can give details of costs, and payback. It will also provide specialist guides for securing planning permission for renewable energy projects (small to large scale) and talk about wider issues including global politics.

Grid Connect Microhydro in Yorkshire?

On 2008/09/21 D Britton wrote to me asking:

I wonder if you can help! I have an old school house on the side of [a river] in Yorkshire. I make bio fuels, and have a 6kW lister generator that runs on straight recycled veg oil. It also kicks out 12kW of waste heat via the cooling system, which I am going to connect to my central heating & U Floor heating. I am also interested in a water turbine on the river, it's tidal, & quite fast flowing. I have looked at the ampair uw turbine, but it only produces 100watts and is expensive. I had a deal with npowerjuice to buy back exported KWh, but after 2 years of waiting for an export meter, I gave up and changed to Good Energy, who will pay for everything I produce, but will rely on generation meter readings, although they pay 2/3s less. I am struggling to find info on synchronising the genny to the grid though, do you have any advice at all please? Also, I would eventually like to run some PV, and wind, maybe into a battery bank, so I don't need to run the genny over night, do you have any advice on suppliers for switch gear, to switch from 1 supply to the other?

(I have a small steel fabrication business, so knocking any framework together for anything is no problem.)

To which I responded:

You need a special 'grid-tie' [inverter which deals with synchronisation] to export to the grid, pref to the standard G83/1. If you have three-phase power that will help.

For more help on hydro stuff look at which is fantastic and full of people who do this stuff all the time. Also they have a great IRC channel at irc://

Solar Power Map of London?

I wrote 2008/09 to the (new) mayor of London, asking:

Can we do something like this for London, possibly including solar thermal (and other microgeneration) too, possibly even off-grid systems?

Ofgem has the data already of course, by power (Wp) and location (address).

and 2008/09/18 I received the (trimmed) response:

Thank you for your email to the Mayor and your idea of creating a solar power map for London. Your email has been passed to the Energy Team and I have been asked to respond on the Mayor's behalf.

The San Francisco solar power map looks like a great way of promoting solar power and possibly other renewable technologies. Thank you for pointing it out. Officers at the GLA have similarly felt a map of renewable energy techonolgies in London would be useful and have in the past sought central government funding to develop this, however due to the existing resource explained below, it was difficult to justify setting up another system. It should be noted that in London solar power makes up only a small percentage of the city's renewable energy potential.

The Department for Business, Enterprise & Regulatory Reform (BERR) currently have a national system of collecting data on renewable energy technologies. This is presented on a map. However small scale renewables fall below the criteria for collection, which means that the renewables in London are not well reflected. Various organisations have in the past tried to persuade BERR to change the way they collect their data to rectify this. Please see the BERR website for more information: You may wish to convey your thoughts to officials at BERR.


I receive a stready stream of emails about the site, some of which I expand into stand-alone articles (eg Going Green in Newcastle-Upon-Tyne and Solar PV in Diffuse (Cloudy) Daylight) and others of which I follow up privately. Also, I've sent unbidden an email or two to register an opinion...

Below you will find some other interesting brief interchanges (edited as necessary); I hope that you find them useful.

Rechargeable Off-grid Nightlight

Following on from my notes about building a non-mains-powered LED nightlight to run from rechargable batteries Steve C wrote to me:

In your LED lighting section on your EarthNotes website, you mention creating something for navigating your house safely at night, an alternative to putting on the main light. I too wanted something similar for my family, particularly for my wife when she had to get up to feed my sons at night. The best solution I found without resorting to DIY (!) is the Philips SpotOn LED light. We've got 3 of them at floor level and they work very well, particularly with the motion sensing mechanism meaning they only switch on when they detect your presence and then switch off 30 seconds later. They're available from Amazon at £5.25 each and they use 3 AAA batteries so are off-grid and can therefore be placed anywhere, I found them too cheap to want to build something myself.

I didn't know about those and they sound like a good idea! Thanks!

Musing on More PV vs Storage

I was talking to myself over on FieldLines over what additional kit would be needed to get us off the grid...

As a thought experiment I like to consider what would be necessary for us to never import from the grid from time to time. In sunny suburban London this is wishful thinking and we have reliable supplies, though we are about zero-carbon and seemingly one of the most efficient UK households for energy.

Which grid? Just electricity for now. Note that this isn't an effort to save money: the grid is *cheap* compared to anything we could do.

We generate about twice what we use year-round, circa 3.6MWh/y vs 1.8MWh/y.

For all but 4 months of the year we generate more than we consume each day on average.

So a small amount of storage, eg a day or two or three, would mean that we could not import anything from March to October inclusive. That might cost us at £500--£1000/kWh in 90%+ efficient low-self-discharge Li batteries maybe £10k.

How to ride out Nov--Feb? At worst our PV should produce about half what we use each day on average, so extra storage for the balance of maybe 180kWh might cost ~£100k and then we need never import again. (All to save about £20-worth of imported energy!)

Alternatively we could in principle put up about another 2.5kWp of south-facing 60-degree-tilted panels if we turned over our small garden entirely to the cause to boost mid-winter generation by the short-fall. That would be £10k.

So maybe we could come off-grid (except to export for income) for £10k of storage and £10k of extra panels.

But what if we wanted to come off the gas grid too, for heating (water and space). Gas consumption last year was a little over 6MWh. Assuming for the moment that we could get a CoP on a heat-pump of 3 year-round, 2 in winter, we'd need 2MWh, amounting to an extra 20kWh/d of electricity mid-winter for heating, implying £1m in storage of £100k of south-facing panels (though only by taking over about 10 neighbouring gardens), or a heck of a lot more insulation!

So, coming off the gas grid in this house looks implausible so far due to the laws of physics and my bank account...

"Climate Change for Football Fans" James Atkins: Quick Book Review

The publisher of "Sustainable Energy - without the hot air" sent me out of the blue a few books to look at, including Climate Change for Football Fans.

Now I'm not a footie fan (other than a brief dalliance with Liverpool), but I do like this book. I dipped into it and worked back and forth (no, no offside trap) and the numbered 'chapters' and summary at the back "Off the terraces" worked for me.

The book's premise is a bet in a pub between a Burnley-obsessed footie fan and a climate-change-obsessed elderly prof, where each attempts to get up to speed on the other's subject better, for £1000.

It's not a massively sophisticated book, there's no formulae or graphs, but it does explain quite well the difficulties of becoming low carbon if and when we decide to do so, how long infrastructure and society takes to change from wanting to, etc, etc.

Burnley survives: the prof doesn't...

East vs West for Solar PV

Jo S wrote to me 2010/09/23:

As a fellow eco-warrior I loved reading a lot of your pages. I fell upon them when trying to search for the best angle for PV panels that I am having installed. I have a three-angled roof, being equally 1/3 south, 1/3 east and 1/3 west facing. The obvious solution is to fill all the south facing roof, then place the remaining panels on either of the other two. My question was which is best east or west. I have had two quotes and each says different! Any ideas?

My next comment to you would be "convert your toilet to run on rainwater!" Or install a full, filtered rainwater system, which can even be used to run dishwashers and washing machines. There are several companies out there offering this. Our water consumption (metered) halved after installing a home-made rainwater toilet cistern.

Not sure that I have earned the 'eco-warrior' badge...

Anyhow I suggested that east and west are basically identical both in theory and practice: see PVGIS and set parameters for your roof. (They could be different if you get consistently sunnier/cloudy mornings, and I'm assuming that there is no shading on one side...)

Note that PV panels pointing in different directions should be on separate "strings", possibly handled by separate inverters, to extract the maximum energy.

As for the ... ahem ... butt-to-butt idea, yes, slowly in progress in fact, though the evidence so far is that the carbon footprint remains lower to use potable mains water for us for now.

GB Carbon Intensity, Heat Pumps and Heat Storage

John B wrote to me 2010/09/03:

Like you, I have been working for a few years to reduce my carbon footprint - see - although I have not updated this for a while.

I am now struggling to find new ways to reduce my emissions. I am down by about 50% but really want to get down by 80% at some point.

I have a condensing gas boiler (as well as wood stove) for heating and am thinking of supplementing this with an air-to-air heat pump (COP about 5.25).

What I am trying to work out is the marginal carbon cost of using this heat pump in the winter. From a grid point of view it might be a good idea to use it overnight but this would reduce the COP and also heat the house when it is not really needed. I am therefore looking at the affect during the day time. The data on your site is very useful and gives the average carbon cost of grid electricity at different times of the day but I am not sure how much it reflects the marginal cost of adding further load. Of course it is impossible to say what effect one heat pump will have but perhaps I can think in terms of a few thousand people doing the same.

My initial thoughts were that CCGT would be maxed out in the winter and additional demand would be met by Coal. However, I compared typical winter demand with peak winter demand from the graphs on this page on the assumption that more demand (from heat pumps) would push the mix from the typical graph towards the peak graph. The graphs show that both CCGT and Coal are higher throughout peak days compared to typical days and that Coal is increased further for the evening peak. On that basis, perhaps your data does reasonably reflect marginal carbon cost (although the evening peak seems more complex). It seems that CCGT is varied over a period of days and Coal is varied over a period of hours. Interestingly, nuclear is higher on the peak graph; perhaps a semi-retired station was used.

I was more than a bit slow getting back to him so he followed up with:

Having done some more research on this, I've decided to be bold and question you model for carbon dioxide saving by deferring load to lower carbon grid intensity....

I think that when deferring a load we need to look at the marginal carbon intensity (i.e. of 1kW load added or taken away) and target the lowest marginal intensity.

To find marginal intensity we need to find which generation type is following the load (preferably hour by hour). From what I have been able to find, this appears to normally be coal in the summer and either gas or coal in the winter, depending on the price ratio of the two fuels.

I would note therefore that if load following at night is by coal, there can be no carbon reduction by deferring load to this time!

There are two parts to tackle here.

Firstly, is my model correct?

A key element to look at in GB grid is storage, I think. It is used most of the day at an effective loss of ~20%, but not at night. Therefore deferring loads to night where they can come direct rather than via storage by helping flatten the demand curve is to my mind enough to justify the model. Storage is a scarce and costly beast. And storage is about the most demand-callable following/balancing load that there is.

Note that a flatter demand curve would be a lower-intensity one on the whole, for fuel and infrastructure reasons.

And we'll need to keep more storage for balancing intermittent sources in future.

But David MacKay would be more inclined to agree with you than me I think!

Secondly, is it likely to be more efficient overall to store heat at home, compared to somewhere out on the grid for example?

(Here I mean heating a store overnight, letting heat out on demand during the day, rather than just heating the house directly overnight. If you had a thermally-massive house with wall or floor heating then these might be one and the same.)

I suggest that if your storage losses from heat are less than those of the pumped storage on the grid, then a local store may be a good idea.

(It's just about possible electrically with decent Lithium-based batteries, maybe getting 10% round-trip losses vs the grid's 20%+ from pumped storage.)

My inclination would be to go for storage only in the winter and only/mainly to support space heating and have such a store (a tonne or two of water maybe, for at least one day's heat demand) within the body of the house, eg under the stairs, so that any 'losses' are actually still keeping the house warm.

I'd be inclined to always to try to do DHW 'instant' so that, for example in summer, there are no storage losses keeping up the overall CoP, though assistance during the winter from the space-heating store might be a good idea.

Laundry Stains: Zap 'Em Quick

Judith G wrote to me 2010/09/10 on the back of our on-going Method review:

I noticed the recent review of Method. [It] seems to be a bit of a failure overall, especially in the cleaning power.

One thing you might mention is an overall approach to doing laundry. My mum always had a bucket of presoak (I think it was biotex) on the go for particularly grubby items, such as the baby's bib you mention. We were always exhorted to deal with stains when they happen (getting told off for allowing a stain to 'set'), and my mum had a host of knowledge about what products for what stain (e.g. oil stains need a detergent, blood needs cold water, &c). Then it all got Dazed or Bolded at higher temperatures than I would use now and came out great. That way of dealing with stains was something that I didn't bother with on leaving home - I was lazy, expected my sci-fi laundry products to do all the work (they never did), and clothes can be bought so cheaply they are practically disposbable. But since I 'grew up' (in my late-20s) I've gone back to my mum's way of doing things, but at lower temperatures and with phosphate-free products. I deal with stains when they happen, give my children a telling off for not letting me know something is stained by who-knows-what and letting it moulder on the bedroom floor, usually have a bucket of presoak on the go, and wash at 30 degress or less with whatever phosphate-free laundry product is available in bulk and at lower price. The only 60 degree wash I do is hospital uniform. Unfortunately I've not been issued enough items to be able to take advantage of the hospital laundry, which has the advantage of economies of scale (as well as someone else taking care of it!). But if I didn't have to do it, I don't know if I would bother with a "maintenance" wash at higher temperatures. Before I had the uniform, I used to only wash at 40 degrees and never noticed any problem with my laundry or my washing machine.

My ecological concerns are not just with greenhouse gases, but extend to water quality (hence phosphate-free) and my own skin (hence non-bio - although I know this is better for protein stains), so I'm willing to pay a slightly higher price for a phosphate-free products, given that my laundry water is going down the drain (i.e. water supply) and not in my soil (which would probably enjoy the phosphates).

I responded:

I'm wavering on the Method and probably wouldn't go as far as calling it a 'failure' though it is not a notable success so far. [Its] ability to do cold washes in the winter will crystallise my views I think.

All your points about getting to a stain quickly are as valid as they ever were (have you noticed the elemental forces that drag tomato and berry juices towards light-coloured business shirts or similar for example, possibly through brick walls and up hill, especially early in the day?), and that is a lesson worth re-learning, not that I do most of the laundry in our house these days.

We also try to use lower-phosphate dishwasher detergent, though for the very toughest loads we use the 'ordinary' phosphate one sometimes avoiding the need to use a higher-temperature cycle to get adequate results. We accept cloudier glassware the rest of the time: I'm sure it's all as clean as I could get it by hand anyway.

Yes, it would be good to avoid throwing away the phosphates (and the heat) in the waste water.

Energy Saving Trust Site Makeover

On this Carbon Challenge item on "increased awareness [and] better buying decisions when it comes to energy efficiency" I rather took the EST's CEO Philip Sellwood to task:

While I would dearly like to use your device energy ratings you fail me each time I buy a new appliance and I have to go elsewhere.

I was told that you don't rate washer-dryers "because they are inherently inefficient" though you do/did the washers and the driers separately and many of us don't have space for two appliances especially for a drier that would only be used a few days a year when line drying outside or in is impossible.

We couldn't use your ratings for selecting a fridge/freezer or dishwasher.

We now come to upgrade our ancient CRT TV to a lower-power LED LCD model and again your site is impossible to use: bad search, no/few in-use consumption figures, and no search by such figures.

I've had to resort to each time since they actually have the information and search facilities needed to select the most efficient device meeting several criteria.

I fear that your appliances selection is a shambles.

We are a family of four, use well under half the average household energy, have someone with an advanced degree and the enthusiasm to get this stuff right, and EST doesn't help.

To which he replied (the same day, 2010/09/02):

The whole site is currently undergoing a much-needed renovation, and the 'Energy Saving Trust Recommended' team is working to make improvements to both the structure and the content of its product information. We want our website to be a simple place for people to find their energy saving products. It should be complete very soon.

Green Eggs and Ham Hydro

Just up the Thames from us, at Ham, a group of householders on either side of Teddington Weir wanted to create a hydro scheme and was told by the Environment Agency early August 2010 that they had been selected as developer. This was covered in the local press with pics of the local MPs supporting it, and after a direct email enquiry from me confirmed that:

The scheme we propose will have an output of 532kW: that amounts to an annual total of 1.9GWh of electricity generated.

Wow! Good stuff! That would cover a thousand households like us, and is dependable steady 'baseload' power.

The Writer Writ: Hot-fill Washing Machines

This one is a bit in reverse! I wrote in response to the interesting Sarah Lonsdale Telegraph item Green property: hot-fill washing machines and said:

  • Most newer machines use little enough water and [are] far enough from the source of hot water that nothing hot will actually get to them before they've filled, at which point they have to heat the water electrically anyway. It would certainly be the case for us for example. For once, electrical resistance heating of water right at the point of use probably makes sense for almost all UK domestic situations almost all the time in money and carbon terms, even if counterintuitive.
  • Actually the better solution is to do cold (or at least cool) washes as often as possible, and we had a huge job getting a sensible cold-fill machine though we did manage and have been pleased with it:
  • Method along with (say) P&G for "Small&mighty" or Unilever for Ariel Excel seem to think "cold" is 15C and specify their detergents to work down to that, but even in sunny London I can tell you that about half the year it's colder than that from our cold mains inlet. So getting formulations sold that work well at 10C or less would be a huge leap forward in energy-saving terms in conjunction with cold washes (we do 20%-ish of our washes completely cold and about 50% at 30C).
  • Method's detergent disappoints us: it generally seems to to less well than (say) Small&mighty at twice the price per wash, so you'd have to be completely compelled by their eco claims to use it I think:

And received an interesting response:

Thanks for your message; I must say, I've decided after all that research to wash clothes cold. I've had about twenty readers send me emails saying they have washed cold for years, their clothes are fine, and actually last longer so I am going to take yours, and everyone else's advice!

"How to live a Low Carbon Life" Chris Goodall: Quick Book Review

Not an email, but my partner borrowed this book for me from the library, unbidden, so it has still made its way to my in-pile!

This book, with a supporting site at is, first of all, free of the science solecisms and stumbles of many well-meaning books in this area, such as important and disabling confusions about power (eg kW) and energy (kWh) which devalue and distract.

Secondly, while not quite as vibrant and dry (and waspish) as Without the Hot Air of Prof MacKay, has many of the same merits: real numbers, clear examples, and sound advice.

What this book really lacks, especially compared to WHA, is decent graphics: not necessarily the graphs and formulae which may frighten non-scientists, but simply more of the sort of simple table on the front cover of the edition I have (2007, 3rd reprint, ISBN 978-1-84407-426-6, Earthscan) which shows tonnes of CO2 by a plane, an oven, and cow, etc.

This book covers why we each should contribute rather than waiting for someone else (or 'government') to, and works its way through the core sources of emissions that we can control, including home heating, water heating and cooking, lighting, appliances. travel (car, public transport and air) and food, as well as microgeneration and green power, offsetting, etc.

In each case there are some fairly detailed worked examples with numbers, and not just on energy: water conservation too for example.

In several places the effective cost of a tonne of CO2 has been computed from the electricity savings vs purchase price of a more-efficient appliance, often ~£200/t. From that the implication is that if the electricity price were raised by that, thus very roughly £200 for 2MWh, or an extra 10p per unit, given 2010 UK carbon-intensity of generation of ~0.5t/MW, ie (again very roughly) doubling UK 2010 domestic prices, the efficiency measures would more than pay back during appliance lifetime...

Anyway, I largely agree with the book's content, though not word for word. And even if you might not, like WHA, it's worth a read.

(As a bonus, my copy had a business card from HM Treasury as a bookmark!)

Another Power-efficient Server

In July 2010 Sebastian A wrote to me describing his own efficiency journey:

I have read with interest the pages on your website - specially the ones on running a laptop on as little energy as possible, the one about creating what is in effect a micro-server out of the SheevaPlug device and about micro wind power.

I thought I would share with you some of my attempts on the subject of running a power efficient server.

About two years ago I started looking for ways to have a 24/7 server at home running on as little energy. My goals were not exactly identical to yours - although I am interested in power generation - I am entirely on-grid - so the provision of electricity is not exactly an issue. However, I was bothered by the idea of having a powerful machine sucking out power in a corner in exchange for doing a lot of time, well, very little. I also became quite pre-occupied about integrating the various peripherals and functions. The idea of having to run a file server, a media server, a wifi access point, possibly a separate firewall and so on - didn't appeal to me. Too many separate devices, too many electricity consumers.

I first started by toying with the idea of one of the wireless routers with a suitable replacement firmware - but found them difficult to get hold of. Then I bought two Linksys NSLU2's. I think they are amazing devices, and the community support is great. However, after few months of configuring them in several different ways - I started to get a bit tired. All this flashing of firmware, and troubleshooting 'in the dark' when something went wrong, without a direct keyboard or screen, started to get to me :-) . Don't get me wrong - great things can be done with these embedded platforms - but I just missed having a real keyboard and screen like on a server, and the fact that I was so used to the x86 architecture and its foibles. Also - the NSLU2 would have needed an external hard-drive for storage, a usb wifi dongle and a usb sound card to do everything that I want it to do - all of them adding to the 5W supposed power consumption.

I tried several old desktops I had lying about around the house - and the lowest I could get in terms of power consumption when idle was about 35W - I really was aiming in my head towards 10W if possible.

Then I tried a laptop. I have been running now a laptop as my main server for more then 18 months. It is a Compaq V2120EA laptop - with a Celeron M 1.4GHz processor. Indeed - I haven't reached (yet) my goal of 10W. Instead - it idles around 20W. But, on the other hand - I have a machine with a screen, a keyboard and an optical drive - which is 10 times easier to install, setup and troubleshoot when something goes wrong. The majority of time is idling along - so the idle power consumption is what I'm interested in most. Aside from having a keyboard and a screen - it also allowed me to integrate the other functions in one single unit:

  1. Fortunately it has one of the Broadcom wifi chipsets which can work in master mode - so I turned it into my wifi access point - using hostapd. That's another device (the wifi router) out - saving probably about 5W-7W.
  2. Then it has an internal hard-disk - so it can serve as file server.
  3. I've also connected to it a Sangoma U100 usb fxo adapter - which allows me to plug this server into the phone line - and thus feed all my phone calls to the Asterisk PBX server running on it. This would have been pretty much impossible to get going on one of the ARM based platforms because of drivers availability.
  4. It has an integrated sound card - which means I use it in conjunction with PulseAudio to play all media/music/film sound from my regular laptop, through wireless to the amplified speakers attached to the server.
  5. At the moment, I am on cable/DSL, but if I ever move to ADSL - I can attach one of the usb ADSL modems to the server and do away with a separate power consuming device (and ADSL router).
  6. It also runs my openvpn server (this wouldn't have been a problem on an embedded device).
  7. It also could be my print server if I will need it - again, this would be a problem because of drivers availability on the ARM platform.

All of the above tasks require fairly low processing power - so I would have been happy with the 266MHz of the NSLU2 - or any similar ARM device. But the fact that various peripherals are a lot more difficult to integrate than on x86 really tilted the whole thing for me.

I have done some measurements on my other laptop - with an Intel U2500 and 1.2GHz processor - and with the lid closed - it clocks about 15W. I have also done some measurements on a Wind U130 netbook - with the new Atom N450 processor - and that showed results towards 11W-12W - again in idle and with the lid closed. So my next step will be to replace the current laptop when it dies - with one of the Atom N450 netbooks (or maybe a newer and more efficient Atom - if one will be out by then). I will just need to make sure it has a Broadcom or one of the compatible Atheros wifi chipsets - to be able to run it again as my wifi access point.

I know the whole setup is not quite as power efficient as one of the embedded platforms - but I do believe that 10W-12W (by the time it will be running on one of the Atom's) is a reasonable sacrifice considering I get all the extra integration of components, ease of configuration and deployment - and the fact that I get to use my favourite Linux distro - Slackware :-). I have to admit that I haven't done any software tweaking on the server yet with regards to power saving. One of the things I would like to possibly try next time would be to run the storage on a usb memory stick, or some internal flash-based memory instead of the spinning hard-drive. There should be some scope for further power savings there.

Thank you again for putting up all the useful information on your website and please let me know if you have any further suggestions on my setup.

I replied to thank him for his fascinating email and to note:

Your journey seems very similar to mine. My current x86 MacBook idles at about 10W, and I believe that several laptops/notebooks running Windows can manage about the same, so I think your 10W target for a single consolidated server is perfectly do-able. I might not have leapt to ARM for my server so soon if I'd managed 10W with a laptop first time around! The difficulty is knowing what idle power will be until you've acquired the machine and spent hours setting it up and tuning it, and by that stage it's too late to take back, though I think that some specs now include the idle power...

Solid-state storage and/or reducing write traffic in particular (so a hard disc can spin down most of the time) will save you a few Watts, and most systems can be tweaked to indulge in far less disc activity than straight out of the box. Watch out for system logging in particular.

I haven't been able to dump the separate ADSL router yet, though it is an aim. The new GuruPlug step up from the SheevaPlug does include a AP-capable WiFi chipset, but I'd still need to find a USB-powered Annex-M (ie >1Mbps up) capable ADSL modem... Any info in that area would be gratefully received!

He was straight back with:

... Yes, the part about Annex M and usb adsl modems is an interesting one. Didn't think about the ADSL2+ requirement until now. If all else fails, you still have the option of a 3G usb dongle with a large data package - at least they seem to have amazingly high upstream speeds (by ADSL standards) - they seem to be almost synchronous. Of course, they also have amazingly high latencies compared to ADSL :-)

It's the first time I hear about the GuruPlug. One of the things that bugged me with embedded platforms was bootloaders. All this business of pressing a button, putting the device in a special mode, telnetting over the network to load the image - not to mention using JTAG's and other interfaces which I have to confess that I am not familiar with at all.

However, on casual search, I discovered the page below - which seems to suggest that there might be some serious overheating issues with these devices (or at least the one tested by the author).

Another thing that I liked about my server laptop is that even after months of non-stop running - it is still fairly cool all around. I do run it though up-side down (with the lead underneath) - in order to keep all the cooling vents completely free. That's another thing I liked about the Wind U130 - how cool it stays. Also, the nice thing about netbooks is that it is possible to find out how hot they get from various reviews - which helps before buying. I was quite preoccupied initially with temperature levels - as the server runs all the time unattended - even when I'm not home - so there shouldn't be any fire risk - even a remote one.

Sebastian seems to be right about potentially poor design, especially thermal, of the GuruPlug. I have a friend in the US testing one for me, and I am sticking with my SheevaPlug (plus spare) for now!

Another Low-Energy Cooking Technique

Joanna M wrote to me July 2010 with an interesting tip that we may test:

I found your great page googling for an estimate of the carbon footprint of mains water. Thanks for doing it! I think I shall write to South West Water and see what they have to say for themselves in comparison.

Reading about your slow cooker I thought you might be interested in another low energy cooking technique: I start my stew/casserole/whatever in the normal way, frying and boiling everything up - if I'm using beans boiling for at least ten minutes of course but otherwise only up to a good rolling boil (with the lid on). Then I turn off the gas and swathe the lidded pan in a towel while it stays on the warm hob. An hour later I'll give it another blast up to boiling (with the towel off) and then insulate again and let the heat do some more slow cooking without the gas, etc. I also use this technique with my pressure cooker which reduces the amount of time to have the gas on even further.

Once upon a time I had a cookpot cosy - which was an insulating outer pot plus cushion lid all made of thick fabric with polystyrene beanbag balls inside which you can pop a boiling pan of stew and head off to work, coming home to find something which can be reheated to boiling again for a couple of minutes and then be ready to eat. It worked very well too, but I'm not sure how long you'd have to use it to get back the footprint of the polystyrene, and the thing with towels could give you warm towels if you time it right...

Anyway, thanks again for your great site, I look forward to reading the rest of it and learning even more.

Power Meter Tips and Tricks

"EMA-1" wrote to me 2010/06/29 with the following:

About your power meters page, and the N67HH:


"It also seems difficult/impossible to reset the cumulative kWh record without completely resetting the unit"

You can reset the Kwh counter alone by using FUNC to display the accumulated kwh hours counter, and then holding the FUNC button for five seconds or until the counter is reset.

A few months ago I began creating instructions for this type of meter after searching the web for instructions (for myself) and finding that many people had difficulty operating the meter and getting the most from it.

I created updated instructions, minimum instructions, and quick instructions to offer a few different ways of getting the job done.

It turns out there are many similar meters and therefore many which use these instructions.

Thanks for that! (I still reset everything, but that won't suit everyone.)

Re condensation management

Garreth T wrote to me mid-March 2010 in response to my note to say:

In actual fact, you should open your windows with the radiators on to reduce moisture.

I'm studying Building services engineering and we have been looking at condensation --- that word of advice is from my lecturer!

He said people always say that's crazy, but it's true, it better forces the air to circulate and dry.

I'm prepared to believe that it's true, though my experiments suggest that any improvement is very limited, more serving to raise my blood pressure and the global temperature with all that heat being forced out the window!

50GW of UK Biomass Generation?

In a discussion started on LinkedIn about how much UK energy/electricity could be generated from biomass (eg as 'dispatchable' generation and acting as low-carbon energy storage for the grid), I asked Stephen B 2010/02/06:

I saw a day or saw ago that DECC was expecting there to be 5GW of firm biomass/waste/etc generation, so dispatchable and storable energy to some degree. I assume that figure included the DRAX co-firing an the new wood-chip plants.

If the figure were 50GW then we largely wouldn't have a problem any more. Could we get it that high?

To which he responded:

It depends how much fuel you can grow!! I must admit when I've been trudging round the countryside recently I've noticed a lot of fields doing nothing!! ...

So, with 50GW of biofossil plant what would we need?? I assume we are burning it in conventional boilers so still at 39% thermal efficiency (full load).

The fuel price will determine the plant's position in the merit order, compared to other marginal coal and gas fired machine. Fuel scarcity can also be included in the system-fuel modelling to adjust the merit order position.

At 50% load factor, in a year 50GW of plant will generate 219TWh; a big proportion of the 350TWh annual demand. The boilers will require @2TJ of heat. At 25 GJ/tonne that is @81MTonnes of Coal (CV 25GJ/Tonne).

With Biomass CV at 9GJ/tonne, assuming 25% Biomass 75% Coal firing mix You would need 60.6MT of Coal and 56.2MT of Biomass. I dont know what Biomass yield is per acre in a year or what the transport impact would be??

Note UK government estimates circa 2010 of 1 million hectares of land currently unsuitable for food crops, implying 8Mt (27TWh) biomass potential. Plus ~5Mt waste wood and ~12Mt suitable 'municipal solid waste' per year which is getting on for half the above biomass number, though some biomass tonnes are more equal than others in terms of energy. So maybe we could get 20GW or very roughly 1/3 of current peak winter demand from local biomass in the UK which would be a very significant partner to wind in keeping the lights on and the heat-pumps running when really needed.

Planning (Low-Energy) Lighting for a New Home

In February 2010 I was asked:

I read your article on LED lighting - do you think it's mature enough to use through an entire house? Am currently planning the lighting in my new house - I guess my main concern is canb I use the same fitting as a conventional low energy bulb, if the LED bulb is not good enough?

I'd say 2010 is the year of the Linux desktop ... erhmmm ... domestic LED lighting. Ordinary retailers are beginning to stock it, and in common fittings such as bayonet and ES14/ES27, lm/W is comparable to CFL and still improving, light quality is OK and still improving, etc, etc, though for anything tricky a specialist supplier is still probably a good bet.

The thing to look out for is the maximum power/lumens rating of the bulb. Difficult to get an efficient LED bulb over (say) 7W in any domestic fitting at the moment, which is roughly equivalent to a 7W CFL or ~40W--60W incandescent. Plus the light cone is typically still much narrower than for an incandescent unless you are very careful in what you choose.

I think the EQ60 is very good and in cool white should be a close match for a 60W incandescent though with a light cone of ~120 degrees rather than the ~300 degrees of a conventional bulb. An EQ80 is on its way, but we'll really have hit pay dirt when we get to the EQ100, matching the brightest ~20W CFLs currently easily available.

So in your case I'd plan for a mixture of current fittings, but possibly slightly more of them than you might otherwise, so that you can use more lower-power devices, possibly also with smaller lighting cones, though both problems are waning.

Remember that unlike an incandescent or even a CFL, when you buy an LED lamp it is probably for life, not just for (one) Christmas...

(2010/08/08: I believe that from next month all domestic lamps/bulbs sold in the UK may be required by law to be labelled with lumens (lm) output, which should help with direct comparisons.)

Saving ~1kWh/day with a Home PC

A project with a sub-1-year ROI (return on investment) is enough to make an accountant weep with joy. Note that many people who are otherwise anti-AGW are nonetheless happy to DoTheRightThing(TM) if it coincides with saving them money; carbon taxes (etc) are about aligning those world views in part...

Gareth H tells me:

Before: 57 watts from the computer and peripherals when the computer was asleep. The majority was going into a huge surround sound system which came bundled with the PC.

Now that I use the Intellipanel from oneclick (Maplin £29.99) this has been reduced to 14 watts. This is composed of Netgear router [that] consumes 9 watts, the sleeping PC 4 watts and the Intellipanel 0.6 watts. The printer, screen, speakers, steering wheel have their power cut to zero.

The computer going in and out of sleep mode triggers the Intellipanel to power everything else off (but the PC).

Keeping the PC in sleep mode and the router connected through ADSL means the PC can always be used at 5 seconds notice. Hence there is no disincentive to putting the PC to sleep. The PC will put itself to sleep after 10 minutes.

Note that some applications such as iTunes have to be tweaked to allow the PC to go to sleep...

Given that the saved electricity should be ~£40/year (and 100--150kgCO2/year emissions from electricity generation), it's a "no brainer" I think.


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