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March 2011 Archives

Here I pose a question to all the talented students in technology and business who actually want to change something - how can the lungs saved of the myriads of people living along congested and dirty roads, urban and rural, breathing in diesel exhaust only slightly diluted by air?

Here is the story: Kolkata, 2nd largest city of India, is a lively, sometimes enjoyable, sometimes exhausting city full of people and experiences. Taking a ride in the direct hinterland of Kolkata, we could discover a full Thünen-like structure moving radially from the city center. First, vegetables were grown, further outward came a leather factory, then fish farming, and then subsidence fishing in the Sunderban swamp land - competing for scarce resources with man-hunting tigers (or so the local tourist board claims). People live directly along this road and populate the street with their petty markets and social exchanges. Cars come not in crowds, but fight their way through people, rickshaws and three-wheelers - loudly honking. A high proportion of these cars, unfortunately, is of old vintage and dirty technology, emitting corresponding amounts of toxic particles, like PMs, SO2, etc. The same is true for most motorized three-wheelers: Many are powered by cheap Chinese water diesel pumps - an equally ingenious and polluting solution. While in average negligible in rural areas, air polluting particles are emitted exactly where people breathe air - i.e. intake fraction is high. Reduced life quality, not to speak about life expectancy is a clear-cut consequence. Not to mention: air quality along squattered streets in urban Kolkata is worse. However, telling the story, I want to highlight that this is not only an urban problem.

Now the point is: this micro-local pollution is produced by a relatively small number of vehicles. Hence, having cleaner vehicles would improve livelihood of millions of people. Also, clean and gas-saving* vehicles may also be a good long-term investment if oil prices are high. Of course, the constraint is that monetary resources only allow for extremely short-term time horizons - meaning low possible investment with fast pay-back but low in magnitude. So the precise task is: Find a viable business model to deliver clean & low-carbon vehicle technologies! Average costs per person km (not vehicle km) should not exceed $0.02 at most, and the solution should comprise both technology and business model. What are your ideas? Please send in, and I will be happy to blog them with attribution on this side!

  • clean and gas-saving (low-carbon) are technically two different options for two different problems, local and global air pollution. However, why not tackle both issues simultaneously if there is the chance?

Fall-out from the Japan quake

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By Matin Durrani

radioactivity_chart.png The impact of the earthquake and subsequent tsunami that hit Japan earlier this month has been truly devastating, with the latest reports suggesting 9000 people have died and a further 13,000 currently unaccounted for.

But if you spend your days following media reports of the disaster, you’d be forgiven for thinking that the biggest catastrophe has been the damage to the Fukushima Daiichi nuclear plant.

I’ve sometimes felt as if the mainstream media almost want an epic nuclear disaster to take place so that they have something to get their teeth into and fill their rolling TV news bulletins.

I was therefore pleased to see a sober assessment of the true nuclear danger from the plant from a recent blog entry by Randall Munroe, a physics graduate best known for his comic-strip website xkcd.

The picture above, which you’ll need to click here to see in full, tries to quantify to the best of Munroe’s ability the real risks from the plant.

Sure, it would be great if the reactor had survived the earthquake and tsunami – and there’s no harm making sure other reactors around the world are as safe as they can be as many countries are doing – but this shouldn’t be the signal for the world to end the recent revival in nuclear power.

You only have to think about the damage caused by the BP oil spill in the Gulf of Mexico last year to see a true environmental disaster.

Of course, the Achilles heel of the nuclear industry is the fear of “radiation” and ionizing radiation in particular. You can’t see it or smell it, which makes it, to some at least, creepily scary.

But hopefully Munroe’s chart puts things in perspective a bit.

In the meantime, we’ll continue to follow how the quake is affecting Japan’s physics community. Things are looking not too bad and the odd bent beamline is far from catastrophic given what else has been taking place.


Fukushima tops nuclear bill in Dallas

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By Susan Curtis at the APS March Meeting in Dallas

Harold Macmillan, British Prime Minister from 1956 to 1963, once famously said that the biggest challenge facing politicians was "Events, dear boy, events". Little did the American Physical Society (APS) know that those same words would apply to session H5, entitled "Drowning in carbon: the imperative of nuclear power", when it was conceived some nine months ago.

Unsurprisingly, the events at the Fukushima Daiichi nuclear reactor in Japan reverberated through the entire session. Most telling was that Toshikazu Suzuki of Japan's National Institute of Radiological Sciences, who had been due to speak on the country's nuclear programme, was unable to attend because of his responsibilities in Japan.

Other speakers and commentators focused on the partial meltdown at Fukushima, as well as the impact that such a serious incident will have on nuclear-power programmes in other parts of the world. Ray Orbach, former under-secretary for science at the US Department of Energy and now director of the Energy Institute at the University of Texas at Austin, had originally planned to talk about the disposal of spent nuclear fuel, but instead gave a detailed commentary on the damage sustained by the Fukushima reactor and lessons for similar reactors in other parts of the world.

According to Orbach, the reactor shut down safely immediately after the earthquake, but it was the subsequent tsunami that caused the emergency power generators to fail – and with them the water-based cooling system used to store spent nuclear fuel rods. But he questioned why it took more than two days for the reactor's operator, the Tokyo Electric Power Company (TEPCO), to start injecting seawater into the core to stop the fuel rods from overheating.

"Why did they wait so long?" he asked. "Well of course you ruin the reactor when you do it. It's also a question of the power company not wanting to admit that all else has failed."

TEPCO was also criticized for keeping a large inventory of spent fuel rods in cooling ponds on the reactor site. Fuel rods are normally water-cooled for a number of years before being transferred to dry concrete casks for off-site storage, but at Fukushima the number of spent fuel rods in the cooling ponds had accumulated because of delays in building an off-site reprocessing facility.

Despite these issues, Orbach offered some technical solutions to improve safety at similar reactors in other parts of the world. Top of the list is to introduce passive cooling for spent fuel storage ponds, which would be unaffected by any disruption to the power supply.

That theme was picked up by Robert Rosner of the University of Chicago, who was also director of the Argonne National Laboratory from 2005 to 2009. Rosner argued that the US has reached a pivotal time in its use of nuclear energy. There are currently 104 nuclear power plants operating in the US, but there have been no new starts since 1977 – largely because of public concern over safety.

"We need to choose whether to only focus on regulation – or even stop nuclear altogether – or to spend some money to identify and fix the safety problems," he told the meeting. With US funding for energy research falling, and an even more suspicious public in the wake of Fukushima, could it be that the balance is tipping away from nuclear – at least in the US?


Energy at 2050

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The International Energy Agency (IEA) recently produced a new edition of its 'Energy Technology Perspectives- Scenarios and Strategies to 2050'. It evaluates possible ways of reducing global carbon emissions while not curbing rapid economic growth in developing countries. It's main BLUE Map Scenario has carbon emissions levelling off by 2020 and then declining by 50% from today's level by 2050, to about 14 Gt of CO2 per year, with fuel saving/efficiency contributing 58% of this reduction. That is made up from increased efficiency in fuel and electricity end use, which saves 38%, end use fuel switching, which saves 15% and power generation improvement and fuel switching, which saves 5%. That leaves 42% of the overall reduction to come from more renewables, more nuclear, and by the wide-scale introduction of carbon capture and storage (CCS). Within that, nuclear accounts for only 6% of the CO2 saving, renewables for 17% and CCS 19%, by 2050.

The IEA did predict that global nuclear capacity would rise to 1200GWe by 2050 from 375GWe today, but some its problems seem to be recognised, and it is clearly not seen as the major player. By contrast the IEA still seems to be fossil fuel fixated, although it is now also keen on renewables. It says by 2050 renewables could provide almost 40% of primary energy supply and 48% of power generation; nuclear 24%; while fossil plants with CCS only 17%- the rest are unabated. And in its enhanced 'HI REN' scenario it has renewables supplying 75% of global electricity by 2050. IEA report:

100% Renewables

A much more radical view is taken by Prof Mark Jacobson from Stanford University and Mark Delucchi from the University of California Davies, who recently produced two papers for the journal Energy Policy, expanding upon their article '100% wind, water, and solar power for the world', published in Scientific American in November 2009.

As before, their scenario runs up to 2050, by which time they claim that all energy, globally, can come from renewables. They say 'A large- scale wind, water, and solar energy system can reliably supply all of the world's energy needs, with significant benefits to climate, air quality, water quality, ecological systems, and energy security, at reasonable cost. To accomplish this, we need about 4 million 5MW wind turbines, 90,000 300 MW solar PV plus CSP power plants, 1.9 billion 3 kW solar PV rooftop systems, and lesser amounts of geothermal, tidal, wave, and hydroelectric plants and devices'. But no nuclear, which is phased out from 2030.

There is extensive analysis of grid balancing issues, with electricity storage in electric/hybrid vehicles (BEVs and HFCVs) being seen as part of the answer, along with better wind forecasting, and demand side management to reduce demand peaks. They add that this also 'requires an upgraded and expanded transmission grid and the smart integration of the grid with BEVs and HFCVs as decentralized electricity storage and generation components' and look in detail at the costs.

The resource implications are recognised e.g. it is suggested that some rare earth materials will have to be recycled or substitutes found, but overall they say there are no major technical or economic problems with getting to 100%, although there may be political and institutional obstacles.

So how about the UK? A new Earthscan book 'Energy 2050', edited by Jim Skea, Paul Ekins and Mark Winskel, outlines some of the results of the recent work within the UK Energy Research Centre, looking at a range of mixes of energy systems, some with large renewable or nuclear percentages, some with large energy savings in various sectors, and then at possible pathways up to 2050, using the MARKAL-MED model. However it is not prescriptive, since, they warn, 'we simply do not know and cannot know,' how the costs and other parameters will develop over the next four decades. And so their pathways study concludes that 'perhaps the most important priority of government policy at present is to ensure that, to the extent possible,the options for the full range of technologies are kept open, so that they all have an opportunity to be commercialised if their development in the meanwhile singles them out as one of the more competitive low carbon technologies of the future'.

That said, they do look at what happens if certain energy supply developments are accelerated, and more generally at the resiliance of the energy system to 'external' shocks and changes. 'Resiliance' has become a buzz-word in this field. A recent conference blurb defined it, in perhaps typically academic style, as follows 'The property or process of social resilience is said to be contingent upon the manner in which the system it describes can successfully achieve a socio-technical and political shift in its internal organisation in response to a change in external circumstances'.

As can be seen, the discussion is moving away from whether heat pumps or micro wind work and on to the social process of transition to a low carbon economy. So while the intro chapters, which review the technical options, are useful and reasonably up to date (although for example not covering EST's damning survey of heat pump performance), possibly the most interesting chapter in this book is the one on 'the way we live from now on', which looks at lifestyle change and how that might help reduce carbon emissions. It suggests that saving of 30% overall might be possible, and 50% in the domestic sector, from changed consumer behaviour. However, much of the emphasis seems to be on transport (admittedly one of the largest culprits) and housing policy (with also a good chapter on micro-gen options and uptake patterns), and OPT won't be happy that there is no discussion of population levels as an issue.

Overall the book provides a good snapshot of the state of play of scholarly study in the UK in the energy field. The basic message is that a transition to a low carbon future is possible, and it explores some of the scenarios that might get us there- but, unlike the US study mentioned above, it does not back any one.

Neither does the new updated version of DECCs 2050 Pathways study, revised after extensive feedback. But it does adjust some estimates of possible future UK renewable energy developments, most notably, increasing the potential contribution from offshore wind under the maximum Level 4 scenario, from 430 TWh/yr to 929 TWh/yr of electricity at 2050, assuming a 45% load factor. /content/cms/consultations/2050pathways/2050pathways.aspx

DECC has also produces a user-friendly web application designed to help the public have a go at making the choices we face when it comes to moving to a secure, low carbon economy, and to let DECC know what they want 2050 to look like. You can try out various mixes of supply and various demand assumptions. Simple but fun. Pity though it's not costed.

All Japan's wind farms evidently survived the recent disastrous quake and tsunami – even a semi-offshore one. With nuclear power's reputation besmirched, following the spectacular failures at Fukushima, is that the way ahead for Japan?

Japan's heavy reliance on nuclear (29% of electricity, compared with the global 14%) is the result of the fact that it has few indigenous fossil fuel resources and has to import most of its energy. As a small heavily populated series of islands, the potential for wind and other land-using renewable-energy technologies has sometimes been seen as limited. But Japan at one time did lead the world in solar PV development and production, and was also a pioneer, albeit on a smaller scale, in wave energy. And it played a major role in the early stages of the global negotiations on greenhouse gas reduction, hosting the UNFCC gathering at Kyoto in 1997, which gave its name to the first global climate change protocol. However banking crises and recession pressures have weakened its economy and it has retrenched on its earlier quite strong commitment to renewable energy, and in 2009 it even opposed a replacement for the Kyoto protocol, backing the weaker non-binding Copenhagen Accord.

Could its approach now be reversed? That would require a major policy shift. A 2008 US Embassy Cable recently released by Wikileaks reported outspoken criticisms of the existing approach from Lower House Diet Member Taro Kono, with the Japanese bureaucracy and power companies seen as 'continuing an outdated nuclear energy strategy, suppressing development of alternative energy, and keeping information from Diet members and the public'.

In particular Kono claimed that the Ministry of Economy, Trade, and Industry (METI) was committed to advocating nuclear energy development, despite the problems he attributed to it, and although METI claimed to support alternative energy, in actuality it provided little. He claimed that METI in the past had 'orchestrated the defeat of legislation that supported alternatives energy development, and instead secured the passage of the Renewables Portfolio Standard (RPS) act,' which simply required power companies to purchase a very small amount of their electricity from alternative sources. He also said that 'the subsidies were of such short duration that the projects have difficulty finding investors because of the risk and uncertainty involved'.

He provided a specific example of how renewables were sidelined, noting that 'there was abundant wind power available in Hokkaido that went undeveloped because the electricity company claimed it did not have sufficient grid capacity'. But in fact 'an unused connection between the Hokkaido grid and the Honshu grid that the companies keep in reserve for unspecified emergencies'.

New policies could obviously help. But how much energy could Japan get from wind and the other renewables? While space is a major constraint, that's also true of the UK and Denmark, and both to varying degrees have significant renewable energy programmes, with on-land wind dominating so far. Japan could certainly do more. On-land wind installation reached 2.3 Gigawatts (GW) there in 2010, compared to 4GW in the UK and 3.5GW in Denmark, and both the latter have since pushed ahead with more, increasingly offshore.

Offshore wind is an obvious choice for Japan. One early study suggested that up to 12 GW of offshore wind capacity could be installed around Japan by 2010, generating around 39 TWh pa, about the same as was expected from then planned 17 nuclear reactor expansion programme. But that's small compared to what is now talked of for offshore wind in the UK, with up to 32 GW off the UK coast by around 2020, and eventually perhaps 150 GW in the North Sea as whole.

The UK is also now pushing ahead with offshore wave and tidal power, aiming for perhaps 2 GW by 2020, and that is something Japan could also do. Japan pioneered wave energy in the 1970/80s, with a floating 'Mighty Whale' Oscillating Water Column system and some harbour wall/breakwater OWCs, but did not follow it up, in part due to its economic crisis. But research now indicates the Sea of Japan is suitable for the use of wave-power technology, while marine current technology would be better suited for power generation plants in the Pacific Ocean or the Inland Sea. It's been estimated that ocean energy plants in coastal areas could provide generation capacity of 30–50 GW.

There are some interesting new projects emerging. For example, Nova Energy Company is setting up a tidal power project near Seto Inland Sea, using tuna fish shaped turbines as conceived by Suzuki. METI is also supporting a joint venture with the industrial and academic sectors of a combined offshore wave power and marine current powered-generation plant, with commercialization scheduled for 2016.

Although China has taken over as leader, Japan is still well placed for PV solar, with a large PV manufacturing base. In terms of deployment domestically, it started off with a '70,000 roofs' programme in 1994, and it is now aiming to have 28GW installed by 2020, 10 times the 2005 level, and then boosting it to 40 times the 2005 level by 2030. Good progress has also been made on the heating side, the use of rooftop-mounted solar heat collectors is widespread in Japan, as is the use of natural geothermal heat that's one advantage of being a geologically compromised area.

As a 'High Tech' player, Japan has also developed some large fuel cells, and the 'hydrogen economy' options are seen as increasingly important strategic industrial developments at various scales. One intriguing large-scale hydrogen economy idea is an ambitious proposal for a gas pipeline across NE Asia, to be fed with hydrogen gas (plus some methane) produced by power from wind and geothermal energy sources, and in particular the large wind energy potential that exists along the Aleutian Islands and Kamchatka Peninsula. A renewable energy-managing base would be built on one of the Kuril Islands between Japan and Russia, which would distribute the energy to eastern Russia and Japan.

That is obviously some way off, as are proposals for High Voltage Direct Current Supergrid connections around the Pacific rim, linking up a wider range renewable sources, and enabling more effective grid balancing. If renewable are to expand significantly in Japan and neighboring areas, then, to help deal with the variability of the sources, something like that will have to be developed, as is now planned in Europe.

How much might be expected from renewables in total? A 2003 report commissioned by Greenpeace – 'Energy Rich Japan – Full renewable energy supply of Japan' – claimed that Japan could make a full 'transition to clean, renewable energy without any sacrifice in living standards or industrial capacity'. The report used 1999 energy data, and showed that demand could be reduced by 50% with energy efficient technologies that were already available, saving nearly 40% in the industrial sector, more than 50% in the residential and commercial sectors and about 70% in the transport sector. The report then showed how renewable energy could be used to meet that new level of demand, reducing and ultimately eliminating the need for imports. Six scenarios of how this might happen were outlined, moving up to 100% renewable energy for Japan.

Starting from a basic model (Scenario One) providing more than 50% of total energy needs from domestic renewable sources, each subsequent scenario provides variations or expansions on Scenario One, gradually reducing the reliance on imported energy, factoring in different population projections and expected improvements in renewable generation capacity and energy efficiencies, until by Scenarios Five and Six, no energy imports are required. And of course, no nuclear either.

Some of Japans nuclear capacity has, in effect, phased itself out- very painfully. It will be interesting to see if a new direction is now taken in Japan, and indeed elsewhere.

For more information, visit

The death, injuries and extensive damage cased by the major 8.9 Richter scale earthquake in Japan are bad enough, but they are also having to contend with a nuclear crisis, on-going as I write.

Three of Fukushima Daiichi's six Boiling Water reactors, and the four reactors nearby at Daini 200 miles or so north of Tokyo, were evidently in operation when the quake hit, at which point, WNN reported, they shut down automatically and commenced removal of residual heat with the help of emergency diesel generators. A small fire in an outbuilding at Daini was eventually extinguished

However, at Daiichi the emergency cooling pumps suddenly stopped about an hour after they were started, due it seems tsunami flooding. Portable power modules were then called in to replace the diesels and enable continued cooling, vital to avoid fuel meltdown. But pressure inside the core containment vessel, due possibly to leaking coolant, had evidently built up to a point where emergency venting was being considered "which will be filtered to retain radiation within containment." As a precaution though evacuation plans were triggered and were later extended to 12 miles.

Then (early on 12 March UK time) there was a major explosion on the site, which some unconfirmed reports claim led to the partial destruction of an outer containment building. There had been earlier reports that internal radiation levels were at 1000 times normal, and unconfirmed reports that exposure rates outside the plant were at about 620 millirems per hour, about the same as the annual permitted exposure. But that may have been before the explosion, which some reports talking of a partial fuel meltdown.

Hard, verifiable, information is scarce, not least since it seems that key radiation monitors outside were disabled by the earthquake/tsunami. Although radiation leakage has been reported, the reactor core containment is said still to be intact, But if the cooling operation is not successful then there is a risk that, aside from the (hopefully low) possibility of a explosion as at Chernobyl, or a hydrogen explosion (as was feared at one time at Three Mile Island in the USA), melting fuel could burn through the core and the floor of the reactor building and enter the soil, a risk that would be heightened if the floor structure was cracked by the earthquake.

That's all speculation at present, and hopefully the situation will be brought under control. But to make matters worse, there were warnings of possible secondary shocks and tsunamis.

Japan is prone to major earthquakes and buildings and other structures are designed accordingly, as was well demonstrated, they had done very well in this regard with few major building collapses. But the tsunami adds an extra dimension for structures on the coast, which is where the nuclear plants are located.

The major 7 reactor 8.2 GW Kashiwazaki-Kariwa complex in central Japan, was hit by a Richter scale 6.8 earthquake in July 2007, which fortunately only led to a relatively small (1200 litre, 90 k becquerel) radioactive leak into the sea. 400 drums of low-level waste were also dislodged in a store, with the lids of around 40 becoming open to the air, with it seems some radioactive gases being ventilated. A transformer unit also caught fire, and there were reports of 50 other problems, including broken pipes and radioactive water leaks. But all were said to be well below safety thresholds.

However, all seven reactors were closed and were off-line until recently.

A review of others around the country was initiated- most of Japans 55 reactors are only designed to withstand quakes of 6.5 – and of course, it's not a linear scale, every unit increase in the Richter scale is ten times more in energy effect terms. An earlier proposal to raise the standard above magnitude 7.1 was shelved because of the high costs. That may now change.

After the 2007 episode, Japans Citizen's Nuclear Information Center commented. "Japan is simply too quake bound to operate nuclear plants," and there were calls for the closure of the reactors at Hamaoka- directly above a geologically active fault 60 miles West of Tokyo.

Hamaoka 4 and 5 were running at the time of the current earthquake but apparently were unaffected and are evidently still running at present, as are Kashiwazaki-Kariwa 1, 5, 6, 7, and Tomari 1, 2 and 3, but Onagawa 1, 2 and 3 automatically shut down as did the plant at Tokai, while WNN noted that the reprocessing plant at Rokkasho is being supplied by emergency diesel power generators.

It's hard to say what will happen next in terms of nuclear power in Japan – it all depends on the unfolding events at Fukushima.

The Zero Carbon Hub (ZCH) was set up in 2008 to support the delivery of 'zero carbon' new build homes from 2016, as a public/private partnership drawing support from both Government and the industry.

Following pressure from the construction industry, an earlier ruling had redefined 'zero carbon' as a 70% cut- to provide some flexibility and avoid what was seen as potentially excessive costs. However, that's now been reduced further, with new lower ZCH recommendations emerging. That led to a jibe from Friends of the Earth, who said 'Let's stop calling these houses zero carbon.'

The Zero Carbon Hub reports' basic approach is a combination of:

• Ensuring an energy efficient approach to building design

• Reducing CO2 emissions on-site through low and zero carbon technologies and connected heat networks.

These first two steps are together referred to as Carbon Compliance (CC).

In addition, there is a third step:

• Mitigating the remaining CO2 emissions through Allowable Solutions (AS), which secure carbon savings away from the site. That in effect means importing green power via the grid e.g. from (remote) wind farms, but there imports, and any other imports (e.g. during winter) are meant to be balanced, over the year, with power exported when there is excess.

However, houses can still have net emissions: the ZCH report outlines recommendations for the actual 'built' performance of the houses, within 2016 Building Regs, as follows :

10 kg CO2(eq)/m2/year for detached houses 11 kg CO2(eq) /m2/year for attached houses 14 kg CO2(eq)/m2/yr for low rise apartment blocks (up to 4 storeys)

These recommendations apply to the actual built performance, and so cannot be directly compared with current design standards. However, on top of any potential carbon savings from moving from designed to built performance, the improvements on the 2006 standard would they say be:

• 60% for detached houses • 56% for attached houses • 44% for low rise apartment blocks

In terms of low carbon supply options, the report says 'Various technologies are available to provide low and zero carbon (LZC) heat. However, as the Carbon Compliance limit is tightened it becomes increasingly difficult to achieve simply through LZC heat generation. LZC electricity generation may also be needed, for which there is a smaller range of options. In practice, the mainstream technology currently usable for a wide variety of individual dwelling types and locations is photovoltaic (PV) panels, which are usually installed on the roof and convert light to electricity. Other options, such as wind turbines and CHP, are only appropriate in some situations and their use should not therefore be the basis for setting a national regulatory limit'.

It was therefore agreed that feasibility should be assessed by reference to the amount of PV required, taking this as a proxy for all LZC electricity generation technologies and assumed that an area equivalent to 40% of ground floor area was the appropriate reference point for feasibility. For heating, the electric option used is the air source heat pump as 'it is a more efficient use of electricity than instantaneous electric and more widely deployable than ground source heat pump', and gas options used are gas condensing boiler for houses and gas condensing combi boiler for apartments. Biomass options might be taken up later. Solar water heating in included in all cases.

On this basis it was concluded that the earlier proposed 70% improvement in Carbon Compliance from 2016, over 2006 levels, was 'not deliverable as a national minimum standard for all dwellings'. Which means that more 'allowable solutions' will have to be used. The study tries to assess the cost of both carbon compliance and allowable solutions, and suggests that that, for a typical detached house, they might be £5,400 (CC) and £6,900 (AS) above the cost of meeting the 2010 regulations, in 2016 prices. It also suggests that these cost are comparable, at around £250k per acre in total, with the cost of meeting the other existing regulatory requirements (~ £400k per acre), although this depends on location, and, crucially, it says, on the price of AS. It chose £75 per tonne CO2 as a reasonable figure . But it says 'There is a risk that it is hard to be sure that off-site measures are truly additional to what would have occurred anyway. Addressing this risk should be an important feature of how Allowable Solutions are defined'.

That sounds a little odd. Why do Allowable Solution sources have to be additional? What are commercial wind farms etc for if not to supply demands like this (and of course others) - and, one would think, at lower cost than PV? But the idea seems to be that, to avoid developers ducking out and simply buying in green power, the remote power has to be dedicated to and created by the house demand. Clearly, as ZCH say, we need more guidance on allowable solutions!

We await the governments response.