Earth Notes: From the Inbox (and Outbox) 2011

Updated 2022-09-19.
Read emails and queries from, and discussions with, readers of Earth Notes (2011).
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...

YouGen Energy-Saving Shortlist

Our energy-saving story at home was shortlisted by YouGen.

My original text sent to YouGen was:

Around the time our second one was on his way and my office at home needed to get converted back to a bedroom for his sister, I was struck by how much energy I was wasting.

The single biggest improvement in energy efficiency that I made at home was to replace several old servers for my home office first with a single laptop and then with a tiny SheevaPlug, going from something close to £1000 per year on electricity to running from solar panels in my small garden. And I moved the result into one corner of a desk in the master bedroom, with no fans and no air-con needed in summer to stop things melting. Maybe not everyone could do that, but leaving 'media servers' and big games consoles and TVs running all the time can waste similar energy.

More domestically, we replaced our fridge-freezer with a bigger one that has more space for supermarket best-before bargains but using half the electricity. And as they became unrepairable, we replaced our dishwasher and washer/dryer with the most efficient ones we could find from familiar brands (and without paying lots extra). Just washing almost everything on cold or 30C with a suitable detergent probably halves the electricity consumption for our laundry for example. In fact we almost never run the dryer: we we drying on the washing line last week!

We're also all CFL or LED lighting now (except, bizarrely, in the fridge), and our total gross electricity consumption is 1500kWh (1,500 'units') per year, less than half the UK average for a home like ours, and down from much nearer 10,000kWh/year in the bad old days of 2007.

By adding lots more loft insulation, blocking draughts, upgrading our single-glazed door to modern efficient double-glazing, installing thermostatic radiator valves, and dry-lining (insulating internally the external walls of) our living room first and then part of the children's bedrooms, our gas consumption has come down to less than 1/3rd of the UK average even as the winters have been getting harsher.

Oh, and we've plonked solar PV on the roof which gets us roughly carbon-neutral.

We've done it bit by bit and the most stressful part was paying for solar PV while thinking my job was going to be canned in Sept 2008!

Usually we've combined efficiency improvements with other work that needed doing, such as our our toilet that leaked into our electrics last week being fixed up with a dual-flush mechanism while we're at it, so not every improvement is significant extra disruption.

DECC Red Tape Challenge

Given the government's Red Tape Challenge I made two separate submissions, one about the unreasonableness of not allowing FiTs to start being counted towards payment until the MCS certificate is received by the FiT handler, penalising the consumer/purchaser for delays outside their control, and also suggesting again "G83-Lite" to encourage very cheap consumer commodity 'nanogeneration' to soak up light from sunny windows and balconies without requiring any paperwork and though not generating FiTs still providing some 'free' electricity and helping to save the planet...

MCS-cert timing and FiT Payments:

... I think that it is outrageous that someone does not become eligible for FiT payments to start until the MCS certificate is *received* by the electricity supplier.

There are several problems with this, which are no fault of the purchaser of the system, and therefore are effectively arbitrary/sharp practice that a private company would not get away with.

Such problems beyond the purchaser's reasonable control are:

  • Delays in issuing certificates. My first MCS cert took weeks to emerge from the system because it wasn't working properly.
  • Delays in transmission of cert from issuing system to installer, installer to customer and customer to supplier, which are no fault of the customer, and which don't in any way impact on the generation or audit trail of the system. For example, what about purchasers without email?
  • If the purchaser of the system is kind enough to allow someone to be accredited on their system pro bono, at obvious risk to the purchaser, then why should they lose revenue due to the inevitable delays between switch on and commissioning? Where's the Big Society in hurting those who do their bit to get new small businesses into the system?

So, FiT eligibility should basically be from MCS-cert *issue* date or possibly in the last slightly-unusual case, back-dated to go-live date if the MCS-cert issuer is happy that nothing is amiss.

I've lost significant money and enthusiasm though being bitten by these 'sharp' rules, and I'm not putting solar PV up to make money. Indeed, I'm trying to give systems away to schools and so on pro bono at this moment, but the FiT-change storm is making everything very difficult. Please could this rule be made a little more just?


May I urge you to create a light-weight version of G83 to allow householders to plug small amounts of generation ('nanogeneration') direct to the grid without paperwork, turning it into a low-cost commodity consumer good. No FiTs required (though a little bit of 'free' electricity for the household of course).

Note that the US government estimates soft costs such as paperwork to be a substantial fraction of solar install costs, and needing a Part-P electrician to install the smallest thing doesn't help either.


Low Energy Lighting Flicker?

Howard O emailed me 2011-11-29 to say:

Your web about domestic lighting is, well, illuminating! Extraordinarily detailed. As you mention peripheral vision headaches, and you are evidently au fait with electronics, I wonder if some time you might explore the issue of flicker? Apart from the ghoulish spectrum, I suspect that strip lights and cfls cause strain because of the 100 Hz refresh. The old crt monitors around 75 Hz certainly did.

We might not directly perceive it, but I did learn somewhere that 100 Hz can be picked up by an ecg when we look at an AC lamp. The optic nerve has surprises! Probably LEDS follow the waveform even more abruptly - or can they be obtained in HF/DC drive configuration as can strip lights?

I suspect that most good CFLs operate much faster than 100Hz, ie not simply off full-wave rectified output.

And LEDs can stick a cap in and operate on DC internally: I suspect that my latest acquisitions do that because they take a second or so to come on and stay glowing for a similar period afterwards.

Howard tells me that he "just might plug a photodiode into a little audio amp so I can check such things."

Transition Beer Naming

Ooooh, I won something involving words and beer!

So the 'think of a name for a Transition beer' competition produced the usual outpouring of inventiveness, some great ideas from some of you, while there are definitely a few of you I'm a bit worried about. The winner, who wins a copy of David Fleming's seminal 'Lean Logic', I'm delighted to announce is Russell Bradshaw. His suggestion, cunningly simple, yet sufficiently humorous to keep me giggling all weekend, was 'Peak Ale'. This was also suggested by Damon Hart-Davis, but of the two, Russell was first out of the hat. Congratulations. Here are the 10 runners up, ...

Damon Hart-Davis suggested "SteadyState, SteadyStateAle, PeakAle, PeakSobriety, TheAleDrum, RenewAle, and also 'RecycAle (with visions of what happens to the processing of the consumers' pee [after] treatment...), and thus ... IPAle".


Shoe Box Homes?

Re: RIBA's 2011-09-14 press release "Shameful shoe box homes: new research reveals how thousands of brand new houses are failing to provide the space families need":

Surely one point overlooked in your press release is that smaller homes can take less energy to heat and less embodied energy in 'stuff' to furnish them, which is good given the energy reductions per capita needed over the coming years.

My own house of 76m^3 (council-built, to high standards, in the 60s, now three bedrooms) happily accommodates my family of four.

I reject the hyperbolic and pugilistic term "shoe box" and note that we use about 1/2 to 1/3 of the average UK household primary energy (gas and electricity) without any great effort and with the PV on our roof have a zero carbon footprint in that aspect at least.

New Scientist Engineering Greats

At the start of 2011 New Scientist magazine had a competition asking "which engineering project would have the greatest impact on human life in the next 30 years".

My submission, not shortlisted, was:

Energy storage on the vast scales need to prop up power grids for days may be the make-or-break technology that allows us to escape the twin troughs of peak fuels (eg oil, gas, coal, Uranium) and frog-boiling climate change.

Gas grids and stores are on the scale we need for now we only have finite fossils to fill them.

Batteries, flywheels, gravel stores and hydro are all here but on scales orders of magnitude too small or too expensive.

Done right and wind, sun, tide, and many other diffuse and intermittent energy flows will come fully within our grasp.

The Economy of Carbon Footprints

Dear Editor,


I sympathise with WILSON BUTT's worry about "paying for something intangible"; I'm not in the business of buying vague heart-warming absolutions either...

I've done what I can in my own home and business on site to conserve energy (we're now about neutral on money and carbon for electricity and natural gas) and where I can't directly deal with the issue on my own plot I try to invest capital and/or reserves in tangible projects such as wind and hydro and solar which should give good secure financial returns as well as significant avoided carbon emissions.


Damon Hart-Davis
London, UK

Smart Metering

In response to confusion over "smart meters" I tried to summarise my understanding of the term (2011-02-13).

There are lots and lots of different things covered by the newspaper catch-all "smart meters" phrase, at least:

  1. A gadget to show the householder their (electricity) consumption in real-time on an easily visible display. This could be done immediately with little effort. This sort of meter is shown to reduce consumption by about 10%. But the simple clip-on ones are confused by some loads and by microgeneration.
  2. A meter that reports to the grid and up to the supplier consumption in semi-real time allowing doing away with most manual meter reads and allowing for variable time-of-day tariffs. This requires everyone to have agreed on a data format and network and there to be a way of getting data remotely from the the meters (though that can involve people driving round in vans collecting the data wirelessly at the least timely). The data flow need only be one way, ie from consumer back to grid/supplier.
  3. A meter that is is constant two-way communication with the grid/supplier and not only takes reading in real-time allowing for variable tariffs, but can also vary/select the tariff in real-time depending on grid conditions, so for example, if the wind dies down during Corrie and then a nuke trips off-line, people will be dumped up to the top tariff and a flashing red light will come on in the corridor. Best avoid making that pot of tea during the break.

The last of these may even be able to turn loads on or off remotely, such as electric car charging or part of the heating element in your washer. This can save the end-user money, and help manage grid stability and carbon intensity.

DIY Domestic Hot Water with Solar PV?

Richard A emailed 2011-01-24 to ask:

I read your article on Solar PV for your lighting at home with interest, since I am also investigating something similar.

My idea was to connect a PV panel direct to a water heater element To provide anything from hot drinking water such as a kettle to a more Ambitious immersion heater for washing/drying clothes etc.

My reasoning was keep everything simple and not use a battery or Charger etc, but to use a hot water storage heater as my energy storage Device. However when measuring the internal resistance of the PV cell I realised it was around 1000 ohms. This seemed to me to Make connecting it to a low impedance load like a element for a kettle (10 to 40 ohms) futile since most of the power from the PV panel is Used up in its own internal resistance. Operating a low voltage fan would Also be a problem since that has a similar impedance. Can you Comment on this as I expected a PV cell to act as a reasonable voltage Source with a low internal resistance. I also noted that the open circuit Voltage of my PV cell varied from 5v to 10v on a very dull day to 15v to 24v on a bright to sunny day. Max current 60mA. A hot water heating element Is nothing more than a type of thermal resistor, so any voltage across it Should yield some heat no matter how small.

I responded:

It takes a great deal of energy to heat water. If that is what you want then solar thermal is a much better bet. If you really wanted to use PV to heat water then you'd use a heat-pump to get circa 3 times more heat for a given electrical input then with direct resistive heating, and that would just about get you back to where solar thermal would be!

A PV cell is a reasonably constant *current* source when lit.

Note that Ohm's Law and friends indicate also that energy dissipated in a fixed resistance such as a heating element goes up with the square of the voltage, so attempting to (say) use a mains (240V) heating element with a typical 'consumer' (12V) solar panel will yield 400x (20x20) less heat/power than you expect. There are low-voltage heating elements, etc, but the currents are huge and the heat might not end up where you want it. And you'd need a huge area of PV; about 8m^2 per kW even in bright sunshine and 10x or 100x higher when overcast.

May I refer you to one of my favourite sites such as or where such things are discussed at huge length with worked examples?


Someone asked me (2011-01-14) if I'd considered CHP for home, ie Combined Heat and Power such as a gas combi with Sterling engine.

I have indeed, a couple of times:

The plus point would be that it would almost always be generating electricity when our PV is not, especially if we plumbed in a small amount of solar thermal to eliminate any need to run the gas boiler around/in summer.

Grid Storage vs Demand Management

FT's energy blog posed questions from readers to [archive] Chris Huhne, the UK energy secretary. Here was mine and his answer (published just as I was taking delivery of 2kWh of off-grid battery storage):

Which will be of greater importance for the UK grid over the next 10 years: storage or demand management? What will the government do to encourage either at all levels in the system from retail upwards?

We need to manage supply and demand in smarter ways to decarbonise electricity, and that means using all the technologies in our tool box. It's certainly not all about quantity of supply — it's as much about using demand management, storage and interconnection to balance our system, in particular at peak times of the day.

I'm not going to try and play god with technologies, but in the near term I can see a particular potential for demand response — so called "negawatts" — as a cost effective way of maintaining security of supply. Battery storage costs are falling sharply and I hope can play a role in the longer term. Electric vehicles can act as mini-batteries when plugged in, or building batteries alongside wind turbines can turn intermittent into flexible demand — like they are trialing in Japan.

This is why we've structured the proposal for a capacity payment, one of the four pillars of our market reform package, in a technology neutral way, so we can incentivise much greater market participation and investment in these balancing technologies.