Earth Notes: From the Inbox (and Outbox) 2010

Updated 2024-06-15.
Read emails and queries from, and discussions with, readers of Earth Notes (2010).
Some interesting brief email interchanges (edited as necessary). I hope that you find them useful.

I receive a steady 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 have sent unbidden an email or two to register an opinion...

Rechargeable Off-grid Nightlight

Following on from my notes about building a non-mains-powered LED nightlight to run from rechargeable batteries Steve C wrote to me 2010-11-13:

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 did not 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 is not a massively sophisticated book, there are no formulae nor 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 does not...

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:

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.

2021: sadly the whole project was wound up and abandoned, having been sabotaged by NIMBY action by a party that has now left the area.

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 is 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 is 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 is a "no brainer" I think.