End of the cam?

Valve actuatorI spotted an article recently about moving away from mechanical cam-driven valves on engines to computer controlled rapid acting “electro-hydraulic-pneumatic actuators” permitting far more precise control of valve movements without the “part open / part closed” stage of their mechanical counterparts. Why is this innovation important? Simple – it appears to offer a 16-17% improvement in fuel efficiency at a stroke – or to put it another way, a potential 16-17% reduction in CO2 emissions from transport (and any other engine-driven process) if it was adopted worldwide.

Steam engineWhich reminded me about “cams” and changing technology- especially as I have one on my desk as I write this! In my youth (well, for my Engineering Workshop Theory and Practice A-Level) I made a vertical D-slide double acting steam engine which uses a cam to control which side of the piston receives the steam, and which side is open to atmosphere. Because of this, the piston drives in both directions, rather than requiring the flywheel to drive the piston back to the top for older single-acting cylinders – at the time a major improvement in steam engine technology. And, in time, this very simple mechanical gizmo made its way into petrol & oil engines as a simple way to control valve movements, and now, for the first time in literally hundreds of years, we’re now seeing a step-change on the technology.

And made me wonder. Given that a move from a simple but commonly used mechanical system to a precise electronic system can radically alter the fuel consumption of the engines of potentially every car, lorry, bus, boat, ship … etc in use on the planet, where else could a bit of lateral thinking make big changes to our efficiencies, resource use, waste, and emissions whilst permitting us to continue to enjoy our tech-rich lifestyles?

UKCG Environmental Training Standard

The UKCG Environmental Training Standard  was published in July 2015, and recognises the leadership role that UK Contractors Group member companies play in driving best practice within the construction sector. It sets down the minimum training expected for individuals to undertake their roles on member’s sites to be able to demonstrate their competency through formal environmental training, including the CITB SEATS course.

This document sets down the standard of environmental training applicable to those who manage, supervise or undertake construction related activities as follows:

Site Managers (including those employed by supply chains):

  1. CITB SEATS+ Course (SEATS plus additional management modules); or
  2. A comparable external course approved by the UKCG Environmental Training Task Group; or
  3. An internally developed course that can demonstrate training outcomes comparable to 1 and 2 above.

The training must last a minimum of TWO DAYS, include a form of assessment, and a completion certificate. Refresher training must be carried out at intervals not exceeding five years.

Site Supervisors (including those employed by supply chains)

  1.  CITB SEATS Course; or
  2. A comparable external course approved by the UKCG Environmental Training Task Group; or
  3. An internally developed course that can demonstrate training outcomes comparable to 1 and 2 above.

The training must last a minimum of ONE DAY, include a form of assessment, and a completion certificate. Refresher training must be carried out at intervals not exceeding five years.

Site Operatives (including those employed by supply chains)

A relevant competency scheme card including the CITB Health Safety & Environment Test where required, and renewed as necessary.

Note – in July 2015, the UKCG and NSCC (National Specialist Contractor’s Council) merged to form Build UK. A list of the members of the new body can be found here

Energy Targets for Buildings

Derbys Eco-Centre 600With the UK Government’s decision to scrap Zero Carbon energy targets for new buildings comes the opportunity to consider better and more practical targets to minimise energy use in the near (25 years) future.

The problem with the Zero Carbon energy target was that it addressed only one form of building energy use (Operational) whilst ignoring Embodied energy – the energy used to manufacture the materials for the buildings that would use the operational energy. If this was relatively small, this really wouldn’t be a problem, but for a modern building constructed of conventional building materials (steel, concrete, masonry, timber), this can be the equivalent to 30 years or more of operational carbon – carbon emitted before the building is even occupied. And this is only the “Initial” embodied carbon – the carbon used to first construct the building; to this must be added the “Recurring” embodied carbon – the carbon required to maintain and refurbish the building over its lifecycle and maintain its’ fitness for purpose and use.

This “recurring” carbon can be relatively minor but frequent – cleaning, for example, or more significant but less frequent – replacement of carpets & finishes or redecoration. However, at some point of the building’s life, a major refurbishment may be take place, for example replacement of the building’s roof or walls – a significant future expenditure of carbon. Or repurposing to make the building suitable for a different use.

Is there a better alternative? Yes, there is – to give all new buildings a “Carbon Budget” for the next 25 years based on total energy use: Initial Embodied (IE) + Operational (O) + Recurring Embodied (RE). For commercial buildings, this could be “functional” for example “Per square metre of internal floor area”, whilst for domestic this could be performance based “Per occupant” (based on say design bedroom occupancy). However it’s measured, the impact would be the same. It wouldn’t matter whether the design was simple (low IE) but with higher operational (O) emissions, or complex (high IE / RE) with low “O” – after 25 years, the total carbon emissions would be exactly the same.

And if you want to improve the performance of buildings year by year, simply reduce their Carbon Budget.

(I’ve written about this topic before – you can read my 2011 article on this here)

Minimising the carbon impact of concrete

We often villify “concrete” with the same high-carbon credential as “cement”, but concrete is a composite of a number of different materials, many of which are commonly used for other purposes in construction and of comparatively low embodied carbon. The way we put these materials together defines the carbon impact of the concrete we use. Useful guidance on the embodied carbon of the commoner concrete components can be found in the Mineral Products Association Factsheet 18, from which the following list is drawn:

  • Cement (OPC Cem I): 913 kgCO2e/tonne
  • Limestone fines: 75 kgCO2e/tonne
  • Ground granular blastfurnace slag (GGBS): 67 kgCO2e/tonne
  • Coarse natural aggregates: 5 kgCO2e/tonne
  • Fine natural aggregates: 5 kgCO2e/tonneConcrete carbon
  • Pulverised fuel ash (PFA) or flyash: 4 kgCO2e/tonne

Designing concrete mixes carefully to minimise the quantity of cement used by replacing part of it by other pozzalanic materials such as GGBS and PFA can have a significant effect on the overall embodied carbon of the mix, typically by 30% or more. This can be seen by reference to the MPA’s Sustainable Concrete Forum’s publication on the embodied CO2e of concretes used in building, from which the data in the table above right has been abstracted (Units: kgCO2e/m3 of concrete). Combined with careful structural design to optimise the volumes of concrete used, careful mix specification can have a dramatic effect on the overall embodied carbon whenever concrete is used.

Concrete wash-out

The washing out of ready-mix concrete lorries on construction sites after delivery of each load is a common occurrence, normally being carried out in a designated “wash-out” area, or, on more crowded sites, into a purpose-built wash-out unit. This unit separates the solid materials from the washout water, and treats the separated water to reduce its alkalinity before discharge to a foul sewer under a trade effluent discharge consent. Whilst many sites accept this as the norm, it is not the only solution, nor in many cases, the most environmentally-friendly one.

The Environment Agency offers guidance how washwaters should be managed on site in their Regulatory Position Statement (“Managing concrete wash waters on construction sites: good practice and temporary discharges to ground or to surface waters“). In Appendix 1 (good practice guidance) the Agency clearly advise that “As far as possible concrete mixing or delivery lorries should return for washout to the batching plant with only chutes being washed out on site.” This is repeated in the EA’s “PPG6: Working at construction and demolition sites” which again states that ready-mix lorries should return to the batching plant for washing out. (Section 7, p.41: Essential pollution prevention).

Clearly, there are benefits to this approach for the contractor, who doesn’t have to allocate space and manage a washout point on site or the waste arising from its use, nor is there standing time for vehicles using (or waiting to use) the wash-out point on site. And, as the majority of mix design codes around the world permit a percentage (typically 5%) of suitable recovered materials to be used in subsequent concrete mixes, returning the 1% – 4% of concrete that remains in the drum after discharge to the plant appears to make economic sense for the batching plant too.

Steelfields washout reclaimerA recent press release by Hanson UK (11 September 2012) refers to two new concrete production facilities in Glasgow noting: “In addition, a water reclaimer allows returned materials and wash-out from trucks to be separated. The solids – mainly sand and aggregate – go back into stock for reuse and the water is filtered and pumped into the supply tanks.” Clearly, batching plants are increasingly prepared for this approach, and are making use of the returned materials, with batching and mixing plant manufacturers such as Steelfields offering wash-out reclaimers as standard equipment.

However, to make batching plant wash-out a workable solution, two conditions have to be met:

  1. The site has to be close enough to the batching plant to ensure that the lorry can return and wash-out (or reload with an identical mix) before the residual concrete starts to set. The rule of thumb to meet this condition is normally maximum 20 minutes return travel time between the plant and site. (But see also 7 March 2014 addendum at bottom!)

  2. The lorry has to be able to return to the batching plant without losing any of the concrete remaining in the drum or chute onto the public highway – hence the EA recommending that the chute is washed out on site.

The first of these is clearly dependent upon the relative location of the plant and site, and the traffic conditions between the two whilst deliveries are taking place. If the travel distance between the two is too long, there is nothing to be done – wagons must be washed out on site or the residue will begin to harden inside the drum.

Until recently, meeting the second condition has been more problematic, with returning lorries losing small but troublesome quantities of concrete onto the road, not only creating uneven road surfaces once set, but also the risk of cracked windscreens and damaged paintwork for other road users whilst still fresh – and consequent insurance claims for the ready-mix suppliers. To minimise this risk, the EA recommend washing out the chutes only before returning to the batching plant, but even this requires a wash-out point on site.

Concretesock montageToday, however, not even this is necessary, thanks to the development of  Concretesocks – simple inexpensive closures that fit over the end of the delivery chute before returning to the batching plant – sealing the end of the chute and completely eliminating the risk of loss of material on the roads. And, on fast turn-around sites, wash-out becomes unnecessary except at breaks as the vehicle can return and refill before the previous mix has begun to set – reducing waste and making more productive use of the delivery vehicle – and in doing so, reducing costs.

So, given that batching plants are increasingly able to reuse materials from washing out delivery mixers, and loss of materials on the roads no longer need be a concern, why are contractors still using (and paying for) concrete wash-out points, or even expensive washout plant, on construction sites close to batching plants?

7 March 2014: At the invitation of Karl Goff, the inventor of the Concretesock, I subsequently had an entertaining and enlightening chat with “Brian the Driver” who has been using this product every day for over 2 years now, and who happily “rolls for an hour” without washing out when returning the the batching plant, “feels naked” if he doesn’t have a sock on the chute when travelling on the roads – and typically gets an extra load a day in as he just reloads with the same mix without washing out at all … just once at the end of the day!

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Carbonated aggregates

Carbonated aggregates have recently featured in the news as a result of the negative carbon footprint of Lignacite’s “Carbon Buster” concrete block – the first concrete block to achieve this. Needless to say, the block uses “manufactured” aggregates – artificial aggregates who’s manufacture converts carbon dioxide gas into solid carbonate products, giving the material its carbon negative credential – sufficient to more than offset the carbon emissions of the cement used in block’s manufacture, with a net capture of 14kg of CO2 per tonne of manufactured block.

(Carbonation is a naturally occurring chemical process where atmospheric carbon dioxide slowly reacts with the hydrated Portland cement matrix of concrete, altering its chemical composition. In doing so, it reduces the alkalinity of the concrete from a pH of 12.5 to 8 or less and exposes any underlying steel reinforcement to the risk of corrosion.)

Patented by Carbon8 Aggregates, Accelerated Carbonation Technology speeds up this process and is capable to turning waste into a material the Environment Agency have confirmed is a “product” (i.e. the carbonation process is an agreed waste recovery process) suitable for virgin aggregate replacement saying “Concrete blocks made from Carbon8 Aggregate … show no worse detriment to the environment or human health than blocks made with virgin aggregate”. The process mixes APCr (Air Pollution Control residue) with carbon dioxide, sand, cement and water to make C8Agg®, an inert carbon-negative aggregate suitable for many applications.

Carbon emissions of cement and concrete

Whilst the production of Portland cement is very energy-intensive and gives off virtually as much CO2e as the weight of product it produces (approximately 910 kg CO2e per tonne of cement), it is only one component of concretes and mortars. In addition, OPC is normally blended with cement replacement materials such as ground granulated blastfurnace slag (ggbs – 67 kg CO2e per tonne) and fly ash (pfa – 4 kg CO2e per tonne). As a result, the weighted average for all cements and blends sold in the UK is approximately 850 kg CO2e per tonne. (Cradle to factory gate)

Reference to the Sustainable Concrete website indicates that in 2012, the average carbon intensity of UK concrete was 79.4 kg of CO2 per tonne of concrete produced, a 23% reduction from the 1990 baseline, with a target reduction to 72.2 kg CO2 per tonne by 2020. Reinforcing bar typically adds a further 10 kg of CO2 per tonne of concrete used.

Carbonation & secondary concrete aggregates

Production of the cement used in concrete is recognised as one of the largest single contributors to greenhouse gas emissions, making up 5% of global CO2 emissions. However, once cast, concrete begins to carbonate, reabsorbing some of the carbon dioxide given off in its manufacture, the rate of carbonation being dependent primarily on the porosity of the concrete matrix, and to a lesser extent, its aggregates

Recent research in Japan has shown that CO2 uptake by the cement hydrate increases significantly when particle sizes are small and are subjected to alternate wetting and drying. Examination of concrete from crushing plants has indicated a typical carbonation uptake of 11kg of CO2 per tonne of crushed concrete aggregate – about 14% of the average UK production carbon dioxide emissions per tonne.

Belin has taken this further and looked at the benefits that enhancing carbonation of recycled concrete aggregates may have on its performance as a material. Recognising that porous weak cement matrices in old concrete leads to poor durability, the researchers found that by accelerating carbonation in crushed concrete aggregates, porosity was dramatically reduced, making the treated aggregates comparable to natural sands and stones commonly used in concrete manufacture.

Which seems like a win-win opportunity for the construction industry. By accelerating the carbonation of selected post-demolition crushed concrete, not only is the end product more durable and suitable for use in concrete rather than being relegated to fill, but in doing so it also absorbs a proportion of the carbon dioxide given out during its initial manufacture. It will be interesting to see if carbon sequestration through accelerated carbonation treatments of crushed concrete becomes more common over the next few years in projects looking to reduce their carbon footprint.

(This is an extract from a longer fully referenced article on this topic available from BPS Eco Ltd)

60W lightbulb alternatives

The promise of a new LED equivalent to the now-phased-out 60W tungsten filament bulb prompted me to do a quick energy & cost comparison of the original tungsten lamps and the available alternatives. Here’s what I found.

60W tungsten filament lamps lasted approximately 1000 hours, over which time they used 60 kWh of electricity, for which I pay roughly 14p/kWh, or £8.40 over the life of the bulb.

The current alternative, a 13W CFL bulb, varies hugely in cost depending upon where you buy it, but you should be able to get a decent quality one for around £5.00. Over the same 1000 hours as a tungsten lamp, it will use 13 kWh of electricity at a cost of £1.82 – a total cost of £6.82 for the first 1000 hours.

CONCLUSION 1 – Even if you have a stock of unused tungsten filaments bulbs, don’t bother “using them up” – throw them away now and replace them with 13W CFL bulbs – you will save money very quickly.

As a decent CFL can be expected to last around 10 000 hours, the savings get even better, and over its life the total cost of a CFL would be around £23.20, This is equivalent to ten 60W filament bulbs used one after the other (if you had them) which would cost you £84.00 in electricity alone.

Not everyone likes CFLs though, so it’s good to see that the UK Technology Strategy Board held a competition for proposals to develop a low energy equivalent to the “standard” 60W bulb that would fit into the same “envelope”. The contract was won by Zeta LED Technology, and they have recently announced that the lamp should be available in 2012. As might be expected, the lamp is LED-based, has an 8W energy use, gives off 650 lumens at a “warm white” colour temperature of 2800 – almost identical to tungsten lamps – and has a life expectancy of 36 500 hours. The manufacturers anticipate an initial cost of £20/unit, dropping to £10/unit once into volume production.

So, over the 10 000 hour life of the CFL lamp, the new LED lamp will use 80 kWh of electricity at a cost of £11.20 – £31.20 in total at £20 / unit – but only £21.20 in total once the new lamp is in volume production, less than the lifetime cost of the equivalent CFL (£23.20).

CONCLUSION 2 – Unless you feel very strongly against CFL’s, on the basis of cost alone you should stick with them for a few years until volume production brings down the price of LED lamps. 

In the same way as CFLs last far longer than filament lamps, LEDs are expected to last far longer than CFLs. Over its 36 500 hours life, the LED lamp will use £40.88 in electricity, whereas 3.65 CFLs will have used £66.43 in electricity. You will also have had to buy four CFL lamps rather than just one LED lamp, so there are long term economies there too. (Note that 36 500 hours is 25 years at 4 hours per day!)

CONCLUSION 3 – In the long run, LED lamps offer the best value, especially once the unit price has dropped, or even straight away if you run them a long time every day.

(CONCLUSION 4 – If you buy the new LED lamps for your own home, take them with you when you move!)

More information on the new LED lamps can be found here:

(Note that the cost comparison ignores any increase in the cost of electricity over the period being considered. Increases in energy cost will always favour lower energy alternatives.)

Halogen vs LED GU10s

How does an expensive LED “spotlight” compare to a cheaper halogen one when their running costs are taken into account?

Just about everywhere you look these days, your eyes get seared by cheap-and-cheerful halogen spotlights – shops, restaurants, pubs, hotels – perhaps even in your own home. But how many of us realize just what carbon-greedy wallet-draining little critters they are?

This is the typical halogen spotlight – a GU10 base with a 50 Watt rating giving off about 250 lumens of light for about 1500 hours before it fails. But as it’s cheap, (and 1500 hours is a whole year at around 4 hours a day) it doesn’t really matter does it? Well, let’s start to crunch numbers. 50 Watts over 1500 hours is 75kWh of electricity, which if you pay the same sort of price as me (about 14p / kWh) is £10.50. So, over the 1500 hr life of the spotlight, it’s going to cost you about £11.85 all up, including initial purchase. And now you need to buy another, and start all over again.

Here’s the modern dimmable LED alternative – 10x the cost on the face of it, but notice the power rating – 3W rather than 50W. OK, it’s a slightly lower light output – 170 lumens (for 50,000 hours!), but I have used a “dimmable” comparison as this gives the LED version the highest initial cost to illustrate the point. So over the same 1500 hours to the halogen spot failing, it will use 4.5 kWh of electricity, which costs about £0.63, so the total for the first 1500 hours is £13.13.

But the LED bulb is still good for another 48,500 hours (roughly!), and while the next 1500 hours with your replacement halogen bulb will cost you another £11.85, the LED will continue doing its job for further 1500 hours using all of 63p in electricity. And the same will happen for the next 1500 hours after that, and the one after that. So, unless you’re planning to use the bulb for less than 1500 hours, the LED version is quickly cheaper overall even though it costs 10x as much as the halogen bulb to buy.

(And I’ve not factored in the hassle or cost of getting to the fittings to change the bulbs when they fail, or ordering / maintaining replacement stock, etc – someone has to do it, and it all has a cost. Or running an air-conditioning system to keep the places where you use halogen bulbs cool as they convert a lot of that 50W into heat …)

That’s my “wallet-draining” comment sorted, so what about the “carbon-greedy” bit? UK grid electricity gives off about 500g of CO2e for every kWh of electricity in the grid, so over its lifetime, a single halogen bulb is responsible for about 37.5 kg of CO2e emissions from its power use alone (equivalent to driving about 170 miles in an average car), while the LED alternative is responsible for a mere 2.25kg (10 miles) – a 94% reduction.

It’s a bit of a no-brainer really, isn’t it? So bite the bullet – next time you need to replace a halogen spot, pop in an LED one instead and not only save yourself money (and buffer yourself against future electricity price hikes …), but reduce your carbon emissions too.

I often provide cost/carbon comparisons like this on selected existing fittings and my alternatives as part of my services when reviewing the energy consumption of premises.

(Prices quoted & lamp images are taken from http://tinyurl.com/3vv63pa on date of posting and include VAT but exclude delivery)

Zero carbon – a step too far?

Does the UK’s low-carbon energy future make the push for zero carbon buildings a step too far? Are we in danger of emitting more carbon overall by making buildings more complex to reduce future energy use?

A few years ago (2007 to be exact), I took part in a piece of research into the embodied carbon of buildings constructed to the then-current building regulations. The surprising upshot was that the embodied carbon was equal to about 25 years of operational carbon emissions from the “ambient” building – heated / cooled to working temperatures, and lit appropriate to the internal activities, i.e. maintaining the internal conditions the structure was designed to achieve.

So, for a new building …

This article was written for the Kingspan “FutureBuild” website. You can read the full article here:

http://futurebuild.wordpress.com/2011/08/01/zero-carbon-%e2%80%93-a-step-too-far/

Transport emissions “Magic Numbers”

A few years ago, I bought a new car that told me the average mpg I was achieving on the current tank of petrol and I started to wonder about what gCO2/km this meant I was achieving at any fuel economy. A little bit of empirical research revealed a fairly linear relationship between mpg and gCO2/km that was true for almost any car for a given fuel type, and a bit more thinking made me realise that complete combustion of a fixed quantity of any given fuel would give off the same quantity of CO2 irrespective of the engine it was burnt in.

Which led me to develop a “magic number” for my car which, divided by the mpg I was achieving gave me a good idea of its emissions – “6600” for “petrol”. (“Petrol” is a blend of compounds rather than a single compound, but I’ve generally found it works well for any 95 octane petrol engine within a percent or two). So, if I achieved 40mpg, my emissions were roughly 165 gCO2/km, 50mpg gave 132 gCO2/km and 60mpg gave 110 gCO2/km. And I did exactly the same exercise for diesel & LPG.

However, in the future fuels will be blended with biofuels, particularly bioethanol in the case of petrol (“E10” and “E85” for 10% and 85% bioethanol contents respectively), and the CO2 calculation for this is much more straightforward as it is a single chemical compound and you can use the combustion reaction to calculate the carbon:

C2H5OH + 3O2 = 2CO2 + 3H2O

Which in terms of molecular weights looks like :

46.068 (ethanol) + 95.996 (oxygen) = 88.019 (carbon dioxide) + 54.046 (water)

So, 1 kg of ethanol will produce 1 x (88.019 / 46.068) = 1.911 kg of carbon dioxide on complete combustion. Given that the density of ethanol is 789 g/l, one litre of ethanol will give off 1508 g of CO2 when it burns, and a gallon (4.546 litres) will give off 6854 g of CO2. But as we commonly measure transport emissions in terms of “gCO2/km”, but think in terms of fuel economy in “mpg”, this needs to be divided by 1.6093 (ie 1.6093 km = 1 mile) to give my bioethanol “magic number”: 4259, rounded to 4250. So, for pure Bioethanol, CO2 emissions in g/km = 4250 / mpg.

Which surprised me, as it is so much less than the figure for “petrol” at 6600 and more akin to LPG at 3250, suggesting that fuel economy should drop off markedly as bioethanol is blended in, but I also found an interesting snippet on the web that went: “By blending ethanol with gasoline we can also oxygenate the fuel mixture so it burns more completely and reduces polluting emissions.” (1)  And if it enables the petrol to burn more completely, perhaps it liberates more power from the mix, giving improved performance that offsets its lower carbon content?

By knowing the number for pure bioethanol, and that for petrol, simple maths gives the numbers for the E10 and E85 blends, and my current list of Magic numbers for different fuels looks like:

  • Diesel — CO2 emissions in g/km = 7575 / mpg
  • Petrol — CO2 emissions in g/km = 6600 / mpg
  • E10 Bioethanol — CO2 emissions in g/km = 6365 / mpg
  • E85 Bioethanol — CO2 emissions in g/km = 4600 / mpg
  • LPG — CO2 emissions in g/km = 3250 / mpg

I’ll update this list if I ever find any info on biodiesel! (Although I suspect it will be very much like “fossil” diesel.)

(1) http://www.esru.strath.ac.uk/EandE/Web_sites/02-03/biofuels/what_bioethanol.htm