Wooden skyscrapers

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Figure 1: Are tall wooden buildings, such as this Stave Church in Norway in Heddal (13th century), about to make a comeback?

Traditionally a limiting factor with wood has been the building height. Historical buildings made of wood were up to 50m high, in the case of some Norwegian Stave churches, but more recently wood structures have been limited to only a few stories tall. But expanding cities need much taller buildings. Hence why this limiting of wood to low lying buildings might be about to change, as there are several proposals for skyscrapers made of wood.

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Figure 2: The Hoho Project in Vienna (left) and a roof detail of CF Moller’s 34 story proposed apartment block in Stockholm (right) [Source: Rüdiger Lainer and Partner (2015) and Dezeen.com (2013)]

Vienna‘s proposed HoHo project will be 24 stories and 84 metre’s high. A 34 story structure is also proposed in Stockholm. In Chicago, the “Big Wood” concept is for a 30 stories high apartment complex. In Vancouver another 30 floor structure is proposed. This is based on research conducted by the Architect Michael Green (see his paper on wooden skyscrapers here (note this is a 31MB 240 page document)).

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Figure 3: The “Big Wood” proposal [Source: Inhabitat (2013) and Michael Charters]

And there are proposals for buildings even tall still. A concept unveiled for London talks of a 300m and 80 floor tower to form part of the Barbican complex. And in Japan, a 339m, 72 story building made largely of wood is proposed. Note that these buildings would involve a mix of wood, steel and concrete, although wood will make up the bulk of the structure.

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Figure 4: Internal floor structure of an ultra tall wooden building [Source: NYT & Owings and Merill LLP (2014)]

So, what are the advantages of wood? Well, assuming its sourced sustainably (not from an old growth rainforest!), its environment impact is significantly lower than concrete or steel. Indeed, potentially wood can have a negative carbon footprint (as it absorbs carbon when it grows and burning it as biomass when disposed of generates renewable energy). Many wooden buildings are these days made to order on an assembly line in flat pack form and there’s no reason why such policies couldn’t be extended to much taller buildings. Making the flat pack wooden skyscraper a realistic future vision.

Wood is also much lighter than steel or concrete, hence the value of its use in the two ultra tall structures mentioned above (while such ultra-tall buildings are beyond the structural strength of wood alone, making as much as possible from wood lowers the weight and thus mean the concrete/steel support pillars can be smaller).

Finally, wooden structures tend to be easier to insulate, as there’s often large voids in the wall (full height glassing is also easier to implement given the low weight of the structure). This is one of the reasons wooden buildings are so popular in Scandinavia, as they can be easily packed with large amounts of insulation (they are also easier to assemble in the short few months you have in summer to put up a building before the winter snows hit). This is important because historically it has been the heating and cooling of buildings that represents the bulk of a building’s lifetime environmental impact.

But what’s the downsides? Well for starters wood need to be protected from root. That means keeping the building water tight and well maintained. The use of preservers or varnish can help, but care must be taken as some of these can have a negative environmental impact when the material is disposed off (my dad once got a load of old railway sleepers and decided he’d use them for firewood….not a good idea given the preservers they’d been treated with!). Also varnish can make for tricky conditions if it gets wet (another anecdote, we varnished some decking and as a result it became an ice rink in wet weather. I once tried to take the dog out via said decking and he refused to go out that way, fearing he’d end up sliding on his bum again!).

Another issue is that of fire risk. Obviously wood is vulnerable to fire and any structure made of wood can be a bit of a tinderbox. Note that this already applies to a lot of historic buildings in Europe. The traditional Scottish tenement for example, while the walls are solid stone, often the floors and roof structure is all made of wood (this is why fire officers make a big deal about all the furniture in such buildings being flame retardant and having smoke detectors in multi occupancy dwellings, etc.). So this is a problem we know about already and with the proper building standards such issues can be dealt with.

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Figure 5: A wooden multi-story building under construction in Zurich [Source: Blumer Lehmann.via Arup (2013)]

That said, with these ultra tall buildings, there is the issue of what to do if a fire occurs on the upper floors, beyond the reach of a fireman’s ladder. This could not only prevent rescue of people, but risk the building collapsing. My guess is some sort of system of automatic fire detection and suppression would solve the problem. But naturally, this pushes up the costs. Although as the Twin Towers collapse show, the issue of fire and collapse is not a problem limited to wooden structures.

However, the fire issue does hint at what’s the major stumbling block – a lack of standards. With existing buildings there are known building codes and standards which can be followed and designed too. However this isn’t really an option yet with wooden skyscrapers. Each one of these will have to be taken on a case by case basis, which will make for a slow (and expensive) planning process. Probably with lots of objections, some valid (which can be addressed through redesign), but also some objections consisting of the usual woolly eared anti-sustainable nonsense (which slows things down while the blindingly obvious is pointed out). The planning issues faced by the tiny house movement being a case in point. Insurance of the buildings might also be an issue until the insurance firms are confident that they can treat wooden buildings the same as any other type of building (i.e. quantify the risks).

But certainly it does show, as is so often the case when it comes to sustainable design, that there are solutions. Just because we’ve always built things this way doesn’t mean we can’t change.

Posted in Biomass, Passivhaus, sustainability, sustainable | 6 Comments

The Panama files

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The revelations from the Panama files of the law firmMossack Fonseca have been on the one hand shocking, yet on the other oh so predictable. It is a well known fact that a large chunk of the world’s capital exists in a sort of “dark matter” like state. We know its there, we can see its effects when the rich flaunt their wealth, but nobody can pin down where it is, so its widely assumed to be tied up in tax havens.

gfi - us assets in tax havensNote the data above based on a 2008 estimate, actual numbers may be much higher now.

Details are sketchy, but the estimate is that between $11.5 trillion and $20 trillion dollars is squirrelled away in tax havens, about 15% to 25% of the entire net worth of the global economy. That equals (or exceeds) the annual economic output of China. Its estimated that…

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The iron and steal business

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This week saw the Tories in trouble over the risk of a sudden collapse of the UK steel industry. UK steel companies have been under pressure for several years now. And with losses mounting it seems Tata plan to cut their losses and get out. Something which seems to have taken the government by surprise. Even though it was inevitable to anyone who had actually been paying attention.

Of course some tried to blame the EU. The trouble is, its since been revealed that the EU had a plan to save steelmakers in the EU from cheap steel imports, only it was the Tories who acted “as ringleader” in opposition to this plan, no doubt fearful of its impact on their buddies in Bejing. Indeed, its been pointed out that concerns about Brexit have probable worsened the situation surrounding the Port Talbot plant.

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Somewhat ironically…

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Weekend News Roundup

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A budget Enron would be proud of

Osborne has been accused of using accounting tricks to hide a £56 billion hole in his budget. Falling growth and the risk of Brexit over the referendum have all pushed down the economy and this will soon have a knock on effect on tax receipts. Yes, he brought in new taxes, but he’ll have to charge a heck of a lot for sugary drinks to fill a hole this big. Even the Office for Budget responsibility (which he set up) are sceptical, while the IFS has warned of a risk of wages falling and that Osborne is “running out of wriggle room” in terms of his ability to meet his own economic targets.

Cdvt28MWwAAoeDF As with previous budgets the poorest people in the UK are the worst affected

Furthermore, it is claimed that the numbers in this budget don’t add up and don’t…

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So much for value for money

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One has to despair sometimes at the ineptitude of politicians and their inability to listen to others. I was reading today the letters page of my Engineers journal and one of the contributors was telling about how back in 1987 he tried to explain to his MP the flaws in Tory plans to privatise the UK energy industry. That MP was none other than John Major, who could not grasp the concept that a private company will not invest in a new power station unless they have a strong financial incentive to do so, i.e. privatisation will lead to either higher bills or no new powers stations, or perhaps both. But of course John Major knew better didn’t he, why privatisation always leads to lower bills….doesn’t it!…oh wait no they’ve gone up massively!

And fast forward to our time. Amber Rudd/Osborne (depending on who you consider to be the UK’s energy minster) decide to cut the subsidy to renewables. They cited “value for money” but as I discussed in a recent post, its likely that creating an artificial shortage for Hinkley C (to please their Chinese masters) is a more likely explanation for these subsidy cuts. And again, critics like me came out and said that no, this won’t save money, renewable subsidies are a tiny fraction of the average bill anyway, in the long run it will push up prices.

And low and behold what’s happened? well we’re now being warned of possible future rises in bills due to the renewable subsidy cuts. The cuts have resulted in a chilling effect across the energy industry, interest rates for energy projects have risen and thus the capital costs for building new hardware, be it renewable or otherwise, has also risen.

Indeed somewhat ironically the UK has now been forced to start subsidising fossil fuel plants, given the drops in investment in power infrastructure recently. So it is very difficult to conclude these subsidy cuts ever have, nor were ever going to reduce bills.

Its entirely possible that if Hinkley C does finally sink, that EDF might even blame the subsidy cuts for making it harder for them to raise the necessary capital. That said, the resignation of two senior members of staff at EDF, including the chief financial officer, does in theory make it more likely that Hinkley C will go ahead, as both cited concerns over Hinkley as reasons for their resignation. Although it doesn’t exactly bode well for the project when the two people who would be responsible for its success decide to jump off the ship before the Titanic even leaves port.

I would note that low gas prices are currently depressing electricity prices. So for the time being, bills will likely continue to drop, but those drops are going to be limited in scale and limited in the time they apply. Inevitably once the higher CAPEX costs get factored into bills and gas prices start increasing again, we can expect bills to start to rise.

But like I said, we’ve played this game for years. Politicians are given clear advice by experts saying what they should do and how urgent it is to do it. This advice is ignored, because the providers of said advice are “biased” (in that they want to see the lights stay on and not see London disappear under the rising tides of sea level rise) in favour of some wing-nut baloney from a Daily Express journalist or back alley lobbyist for the shale gas industry, who apparently aren’t biased. And low and behold, what the politicians were warned would happen does happen, but somehow its not their fault.

On certain matters of critical infrastructure there needs to be disconnecting of politics from the important job of keeping things running.

Posted in climate change, economics, efficiency, energy, fossil fuels, nuclear, politics, power, renewables, Shale Gas, Shale oil, subsidy, technology | Tagged , , , , , , , , , , | 3 Comments

Debunking the Great Reagan myth

Something I put up on my personal blog regarding Reagan, which is perhaps topical given recent events in the US elections. Of interest as regards energy matters would be Myth #1 relating to the real reason behind the collapse of the soviet union (which had little to do with Reagan) and myth #9 which relates to the Reagan Adm. attitude towards climate change (while certainly no environmentalist he was certainly not a climate change denier or anti-science).

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A central founding myth of the Tea Party is the legacy of Ronald Reagan. It is one of the reasons cited for supporting Trump as they see him as another Reagan (although its worth noting that not even Reagan’s own son agrees with this one). Around Reagan, or Thatcher in the UK, cults of personality have grown that border on those of many a despot. Hence why I think it would be prudent and timely to de-construct this myth and expose the realities of the Reagan Presidency.

20110210 Figure 1: Reagan has developed something of a cult of personality that ignores the realities of his reign

Myth #1 – Reagan brought down the Soviet Union

Reality: Reagan wasn’t even in office when the Soviet Union collapsed and there is very little evidence that his policies helped push it over the edge. Economic miss-management and internal opposition offer more…

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Airborne wind turbines

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Figure 1: Airborne Wind turbines could be a major game changer…..if they work! [Credit: Magenn power, 2008]

I recall someone asking a while ago for a review of airborne wind turbines (often known by the acronym AWES as in Airborne Wind Energy Systems), which I never got around to doing. But no time like the present.

So, what is the point of AWES? After all wind energy is already the cheapest of renewables (perhaps according to some the cheapest overall means of electricity generation), so why re-invent the wheel? Well because the capacity factor of conventional wind turbines is around about 33%. Capacity factors can be higher for some wind turbines offshore, but it can also be lower for those further inland (and not all countries have coastlines!). By placing a wind turbine higher up we gain the benefits of more constant winds. Its suggested that capacity factors closer to 60% would be possible, perhaps even 80% in the jet streams. Also wind speeds tend to increase with altitude. Go up a mountain and the strong breeze at the bottom can be a howling gale you couldn’t walk against at 3,000 ft. So a higher wind speed means more power for a given turbine size.

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Figure 2: Wind Speeds with altitude

Also by putting turbines in the atmosphere we get to stack them in three dimensions. There is much discussion as to how much energy can be usefully derived from the Earth’s winds. Some estimates are relatively low, others much higher. AWES’s however change the game by allowing us to tap into much more atmosphere than simply the thin crust of the lower atmosphere.

Its worth pausing to define the capacity factor as the rated capacity of the turbine over time e.g. a powerplant that gets turned on at full power for 3 months each year (typical for a peaking load plant) would have a capacity factor of 25%. This does not mean the turbine generates nothing 70% of the time, actually it will usually be generating some power, just not working at its rated capacity. Also the grid will not be drawing on its full power load all of the time (hence why peaking and intermediate load plants have much lower capacity factors).

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Figure 3: Various types of AWES designs have been proposed [Credit: Gizmag,2013]

Various different types of AWES have been proposed, a recent review of the technology is available from Cherubini et al (2015). These generally break down into two general categories, Fly-Gen systems (where the generator is carried aloft) and Ground-Gen (the generator stays on the ground). Fly-Gen systems can involve large balloons with the turbine either mounted inside (to create a funnel effect) or on the outside (larger diameter, hence larger swept area). Others operate more like a giant kite, with an attached turbine. Ground-Gen systems typically involve the use of kites (rigid or otherwise) flying at altitude while connected by a tether to the ground, which creates a rotational torque creating power. A variation on this idea is to use such kites as a means of propulsion for ships (so called Sky sails).

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Figure 4: The operation of a Fly-Gen type AWES

There are several factors which determine the power output of a wind turbine. The wind velocity (to the cube, so a doubling of wind speed will increase 8 fold the power output), the swept area (more area, means a larger mass of air is capture, hence more power output) and the air density. The denser the air, the more power can be extracted by it. Unfortunately as you go up in the atmosphere the density of air falls. At 1,000 metres the air pressure is 90% that at sea level (so a 3 MW turbine at this height will only generate 2.7 MW’s) and at 5,000 metres its about 50% sea level pressure (so our 3MW turbine now only generates 1.5 MW’s). Also any tether will be creating drag and the higher the operating altitude the greater the drag.

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Figure 5: Increasing wind speed leads to higher energy yields…..[Credit: Kitves (ND)]

So there’s a trade off in terms of how high a turbine is positioned and falling air pressure. This is why most current designs plan on operating in the hundred’s of metres or perhaps just over 1,000 metres. Of course this goes back to the argument about maximum wind energy extraction, as it means that we can only tap a small portion of the atmosphere’s wind energy. Certainly an order of magnitude larger volume would likely be possible than with conventional turbines, but not quite as large a reservoir as previously suggested. Even so even the most conservative estimates (Marvel et al 2012) significantly exceed current global power demand.

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Figure 6: …..But higher altitude means lower air pressure [Credit: Engineer’s toolbox (ND)]

Average wind speeds more or less double between sea level and 1,000 metres (so the density of power output from the turbine increases almost 8 fold, as discussed). It should be noted however this doesn’t mean that the rated speed of a turbine for a given diameter falls (this factor is determined by physics), its just the same size turbine will be exposed to a higher average wind speed and generate much more power and hence should have a higher capacity factor than if we left it on the ground.

But what about down time? All of these AWES include a tether mechanism. That will need regular maintenance, which might well mean landing the turbine. And as Cherubini et al (2015) discuss, there may be issues with landing and take off procedures, particularly in incremental weather.

Also one has to question whether the tether will be designed to withstand stormy conditions, e.g. hurricane strength winds. Normal turbines simply feather themselves out of the wind, if the wind speed is too high, then restart once it drops to a safe level (and its worth remembering that this is generally only needed for the period of peak wind speed, during the bulk of the storm they can keep generating). AWES would have to land and stay down until winds dropped to a safe launch speed. Also how would they ride out the storm on the ground? Many strike me as not being very sturdy. Likely they’d need to be hangared on the ground (normal for airships and kite like aircraft), which adds an additional cost.

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Figure 7: Wind speeds worldwide [Credit: Kitves (ND)]

One solution to the above is to only mount these turbines in regions of the world where we don’t see such severe storms on a regular basis. These tend to be around the coasts of the major continents. Moving them inland would thus reduce down time due to storms, as we’d see less severe weather in terms of damaging high wind speeds (perhaps negating the need for hangars). However, overland in the middle of continents tends to mean lower average wind speeds. While we’ll get higher wind speeds at altitude (and again doubling speeds at altitude means an eight fold increase in power output), but it won’t be quite as great a pay off as we get on the coasts. And again if we only mount them in such locations, we greatly reduce the effective area where such turbines can operate, so on a global scale we are reducing the total amount of power we can extract from them.

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Figure 8: AWES may be transported by truck…until they reach a low bridge!

Another factor is that of average wind speeds. Increasing it certainly does mean higher power output (for a given altitude) however this also means the turbine needs to be designed to withstand these more intensive operating conditions. Modern wind turbines are largely overdesigned (one of the reasons for recent price drops being engineers finding ways of reducing the level of overdesign, yet still retaining a reasonable level of reliability) but they don’t have to fly! Designing anything to fly often means paring down the mass to the bone, which in simple terms, will generally push up the costs for the same size of turbine.

Some costs savings are possible ,on the lack of a tower for example, a more constant wind speed would allow for some savings in terms of the gearbox and generator design, but none of this is going to produce a huge saving. An airborne turbine with a given rated power output is, I suspect, going to inevitably have a higher installation cost than a comparable ground based wind turbine. Maintenance costs are also likely to be higher. Although in both these cases, its difficult to be specific as the designs are not sufficiently advanced to give a firm idea of what the costs will be. As regards the overall levelised energy cost, that should work out lower for an airborne wind turbine given the higher capacity factor.

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Figure 9: The cost breakdown of a conventional wind turbine [Credit: GTMS, 2013]

Exactly how much lower however is difficult to assess. This brings us back to the debate regarding wind energy and its low capacity factor. The critics (often nuclear energy supporters) of wind energy will tend to pile on masses of costs, often insisting on building an entire fossil fuel plant and all its associated costs to compensate for the intermittency of output. However, such simplistic analysis often ignores the fact that all energy sources require some level of backup.

Furthermore the load they are supplying isn’t necessarily drawing on power all of the time, so in any fossil fuel free grid there will be a need to funnel some significant quantity of energy away and store it, regardless of what energy sources we rely on (be in nuclear, CSP, geothermal or intermittent sources such as wind and PV). Certainly a grid which is heavily dependant on intermittent wind or PV will have a larger storage requirement, although exactly how much more is a matter of some debate, as I’ve discussed before.

Certainly, with regard to AWES, one has to comment that research is mostly still at a non-commercial stage so it is very difficult to speculate as to the exact costs, but of course that means they could go either way. Even if airborne wind turbines work out as somewhat more expensive than conventional wind, the advantages they bring of being able to tap into a much larger wind resource and a more even power output with greater capacity factors will mean they offer some benefits. But, like I said, I would argue that the balance of probability is that airborne wind turbines will have higher install costs, but a lower life cycle cost (although like I said, that’s unproven), although how much lower (assuming they do have a lower LOCE) will depend on how much they reduce the need for energy storage.

As with any technology there will be some level of overshoot with AWES. One topic that often comes up is the idea of placing them within the jet streams. Here they would benefit from a very high wind regime and a capacity factor that is higher still, perhaps as high as 90%. However this would mean operating AWES at a significantly higher attitude 9-12 km’s height in fact (thus a much lower air density, i.e. less power output for a given wind speed) but a higher wind speed (+40 m/s v’s the normal rated speed of 14 m/s for a ground based turbine). Needless to say, operating turbines in this regime would be even more of a challenge than simply a few hundred metres off the ground. Such a turbine would represent a significant engineering challenge to design, although certainly not impossible (aircraft do this all the time remember).

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Figure 10: The jet streams [Credits: NASA & NOAA (2013)]

Also the jet streams only cover a relatively narrow corridor of air. If we apply the conditions above (i.e. only tapping into them over land in central continental areas) this greatly reduces the locations where such turbines could be mounted. So only a handful of countries, most notably the US, Canada, China and several central countries, would be able to benefit from them. Even so its worth noting that the theoretical power densities of the jet streams are in the order of 3,000 – 4,000 W/m2 well above anything achievable for conventional wind or even proposed AWES. So you won’t need to cover a very large area with them to extract a lot of power. Although its also worth noting that the jet streams do move, so the turbines would need to do so also (yes I’m saying wind turbines will need to be migratory….so no African swallows then). I would argue that such projects are somewhat speculative at the moment, as its simply too early to say whether it would be possible. Certainly I don’t see anyone such projects (on a commercial scale) within the next decade or two.

All in all I think that we can conclude that AWES might be able to provide a source of wind energy that is more regular and less intermittent. However they are likely to come with a number of strings attached (if you’ll pardon the pun). They may not be suitable in all locations, hence they will likely compliment rather than replace existing wind energy technology. The install costs will probably be higher than with existing wind energy, although the levelised cost of energy might well prove to be lower (but that remains to be proven). However the technology isn’t sufficiently mature for us to assess that at present. They may well reduce the levels of energy storage needed, but as noted, a substantial level of energy storage will be needed in any future low carbon grid, regardless of what options we take.

In terms of the overall energy picture AWES will increase the amount of renewable energy that can be extracted from the winds, although exactly how much is difficult to access at present, as this the main constraint on the extraction rate of renewable energy is likely to be economics.

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