Monday, October 22, 2012

Fuel from air or just hot air?

From a few sources, I’ve had a story about a UK company that claims they can make petrol out of air and water (actually hydrogen extracted from water and carbon dioxide extracted from air).

I perused their web site and one critical figure is missing: energy return on energy invested (EROEI: which has to less than unity because a hydrocarbon fuel made from hydrogen and CO2 is an energy store, not source; plants consume solar energy to do this trick). If you make a hydrocarbon fuel any other way, it costs energy, but I have my doubts that this can be better than e.g., using a feedstock like biomass because CO2 density in the atmosphere is so low, about 400ppmv (and biomass starts from chemicals closer to what you want, created with the aid of photosynthesis – so there’s some chance of over-unity EROEI).

Here are some numbers: petrol has an energy density of about 35MJ/litre which is about 10kW-h/litre. They claim they can produce:
1,200 litres of liquid hydrocarbon fuel per day using approx 3 MW (nominal installed capacity) of renewable electricity
Be generous and assume this is in only 8 hours, which means they are using 24000kW-h of electricity to produce a fuel with total capacity of 12000 kW-h so they their energy cost is double the energy out (EROEI = 0.5). If their plant actually takes all day to produce this amount of fuel, EROEI is much worse (0.17, or less than 20% of the energy put in). Add in the inefficiencies of internal combustion engines (as I recall, about 5% of energy produced gets on the road) and this is not terribly exciting.

The only way it can make any sense is if you use up waste energy, e.g., if you have a wind farm that’s producing electricity at a time when you don’t need it. If you are going to do that I would rather just make hydrogen. Hydrogen can be used to operate a fuel cell, and can also be burnt directly as a fuel. While the energy density of hydrogen is much lower (especially in terms of energy per unit volume) than a hydrocarbon fuel, a large vehicle like a bus can operate efficiently off a hydrogen fuel cell, and hydrogen could also be a useful fuel in stationary applications.

The most promising alternative to fossil liquid fuels currently is algal biofuels. Algae use photosynthesis efficiently to produce biomass; that makes a lot more sense to me than this proposal.

Sunday, September 23, 2012

Hypocrisy Exposed

You have to admire the chutzpah.

The fossil fuel industry has a track record of funding professional science deniers to undermine public confidence in climate science and global warming. Climate change, we were led to believe, was "junk science" (along with other science that predicts effects harmful to an industry, like the ozone hole, and harmful consequences of tobacco and asbestos). Now that a predicted effect, the rapid decline of Arctic sea ice, is happening on schedule, if not a little faster, fossil fuel companies are rushing to exploit the new opening of lower-cost exploitation of Arctic reserves.

Clearly, if fossil fuel execs do not believe that the climate is changing to a warmer phase, they cannot plan on Arctic waters being increasingly accessible through summer. Such improved access is critical to economic viability. While a large part of the Arctic will still ice over in winter, easy access during summer radically reduces costs of supplying operations and shipping out gas and oil over water.

Part of the rush to exploit these reserves can be explained by growing demand and depletion of other reserves. Even so, fossil fuel companies have to have increased confidence that costs will be lower than previously to find the prospect of tapping into Arctic reserves appealing. If what climate deniers claim is true, the current low in Arctic sea ice is a temporary blip, and we have summers ahead when ice will return to former levels.

I can think of only two explanations for the industry's confidence in the profitability of exploiting the Arctic: there is some natural phenomenon someone has modelled accurately that predicts a continuing decline in Arctic sea ice, or the industry accepts the mainstream climate models that predict human-caused climate change will continue to radically reduce Arctic summer sea ice. If the former applies, no one has published such a model and, given the huge interest fossil fuel companies have in deflecting action on climate change, it would be bizarre if they had such a model and didn't publish.

There is only one conclusion that fits the evidence:
fossil fuel companies accept the mainstream science and are using it to predict the future viability of Arctic fossil fuel extraction

If you previously believed climate change was a hoax, this is a good time to stop conning yourself. The fossil fuel industry clearly does not believe their own propaganda, so why should you?

Saturday, September 1, 2012

The Ice Thermometer

On 27 August 2012, the US National Snow and Ice Data Center announced that the Arctic sea ice extent had broken through the minimum set in 2007. Why is this significant? First, loss of sea ice is a directly measurable consequence of a warming planet. Second, the greater the sea area exposed to incoming solar radiation, the greater the warming effect because ice is highly reflective. Ice loss is one of the key amplifiers of any initial form of warming, whether orbital perturbations leading to the start or end of an ice age, or changes to the atmosphere such as is happening in the modern industrial era.

Minimum sea ice extent. Each grey line represents area of sea ice (areas with at least < 15% ice cover are added to the total) over a year; the red line the current year. Graph drawn using R software by Rasmus E. Benestad, posted at RealClimate, from data at the National Snow and Ice Data Center.

At time of writing, the area of sea ice was still trending down; we will only know the actual minimum when it starts to increase again. Why should the sea ice extent have hit a new minimum this year? Data so far for the year does not indicate it will be unusually warm by standards of the last few years. None of the short-term natural effects should have a significant impact on temperature averages this year. We have not had a big El Niño, and the solar cycle remains one of the lowest on record, though we are on the higher side of the cycle.

Sea ice volume anomaly
The key to understanding this is that the area of ice takes a long time to change, even if the volume of ice is changing fast, because the permanent ice over the Arctic is multi-season ice. If conditions warm sufficiently to melt multi-season ice, it does not melt in one season. Instead, it progressively becomes thinner.

If we look at the long-term trend of sea ice volume, it becomes clearer what’s going on. Total sea ice volume has been trending down steadily, with a sharp increase in the trend in recent years, breaking out of two standard deviations (the grey area) from the trend.

How can this be happening if temperatures are not increasingly sharply?

First, there’s my point about long-term ice being lost. Once it’s gone, it takes that much less energy to thin the ice further next summer. Also, about 90% of incident solar energy is absorbed by the ocean [Levitus et al. 2001], and ocean heat transport is a significant factor in governing the temperature of the planet. El Niño and La Niña events occur when some of that energy is either released to the atmosphere, or the oceans absorbed a little more than the average amount of energy in the system. Increasing the energy content of the oceans is the big sleeper in climate science: the thing the public doesn’t pay attention to because the numbers look small compared with temperature increases in the atmosphere. The relevance of all this is that a relatively small shift in where that extra energy ocean goes could have a big impact on sea ice.

Measuring ocean heat content is very complex because the effect of currents including thermal transport between depths has to be taken into account, and measurement is in a relatively harsh environment, meaning instruments have to be changed frequently, with potential for calibration error. You can’t just stick a thermometer into select parts of the ocean and measure for a few decades as you can on land. But guess what: Arctic ice is turning out to be a pretty damn good thermometer.

For more, go here for another interesting article.

September 2012 minimum


On 19 September, NSIDC announced that sea ice had appeared to bottom out at 3.42-million km2. I’ve redrawn the graph (22 September 2012 data); it appears to have taken another small dip to 3.37-million km2, 19% below the previous minimum of 4.17-million km2. The script reports the previous low as 4.16-million km2. Possibly NSIDC is rounding the numbers differently, or smoothing the data they report (they generally report numbers averaged over the last 5 days). Either way the difference is slight; the latest record represents nearly 20% below the previous record.

Contrast the current situation with a 2006 paper that was widely misrepresented as an alarmist prediction that sea ice would be all but gone by summer 2040 [Holland et al. 2006]. The focus of that paper in fact was demonstrating that a very rapid drop in sea ice is possible over a few years. In the scenario where the Arctic summer was almost ice-free in 2040, it would have taken until about 2030 for sea ice to drop as low as it has this year – and then only as a consequence of one of the abrupt drops the authors claim is possible.

Holland et al fig 1(a) compared with 2012 minimum
In this graph (based on Holland et al fig. 1(a)), based on an ensemble representing seven models (grey bars are the range of values, the black line is representative of the ensemble, the light blue line is smoothed using a 5-year running mean, the red line is real measurements smoothed with a 5-year running mean), the 2012 level of ice has arrived 20 years early – and this is a paper that attracted controversy at the time as being “alarmist”. I compare reality with the smoothed data (light blue line); models like this are not intended to predict annual data accurately. Since the grey bars represent the range of values from different models, you could say that 2012 matches the lower edge of a prediction (one of the grey bars touches my 2012 line at about the right time), but that’s more accuracy than the models should claim. I’ve marked on the graph the 2012 minimum and the point where it intersects the model graph.

Note also that the ice level we see today would only have happened in the smoothed Holland et al. ensemble of models after an abrupt drop in ice extent (the grey area of the graph), something that hasn’t happened yet. If their models are correct, and there is a scenario when sea ice extent falls rapidly, the 2040 “prediction” might yet prove to be conservative.
There are some who take comfort for the fact that a model such as this is not 100% correct. I don’t see why. There is enormous pressure on scientists in a field where findings have major economic impact not to be “alarmist”, which has a dampening effect on publishing results that predict disaster. If disaster is likely, I’d rather know in advance and have the option to head it off.

Those attacking the science, on the basis that it’s not 100% accurate and that the margin of error in predictions includes the possibility that nothing “alarming” can happen, miss miss the rather obvious point that the margin of error includes the possibility that reality will turn out more alarming than predicted. Worse, as reality unfolds on the worse side of modelled outcomes, they continue to deny.

Sydney Levitus, John I. Antonov, Julian Wang, Thomas L. Delworth, Keith W. Dixon, and Anthony J. Broccoli. Anthropogenic Warming of Earth’s Climate System, Science 13 April 2001, 292 (5515): 267-270
Marika M. HollandCecilia M. BitzBruno TremblayFuture abrupt reductions in the summer Arctic sea ice. Geophysical Research Letters 2006, 33(23): 217. 25

Wednesday, May 30, 2012

Base Load and Clean Energy

A commonly stated claim by advocates of business as usual is that renewables cannot provide base-load power generation. In the industry, base load is the minimum that has to be continuously available. With large coal-fired plants, keeping them running at a constant rate of output is a lot cheaper than reducing or increasing output – provided you want all the power generated:it isn’t cheap to produce something if it’s wasted.

Power utilities attempt to balance demand around the clock to keep it reasonably constant. That’s why for example your electric hot water system has a ripple relay, a switch that can be turned on or off remotely by varying the usually regular AC sine wave. During times of low load, all the hot water systems on the system are turned on; when load starts to get high, they get turned off. This works because you are storing energy in the form of hot water.

For renewable energy systems to work so that you can flick a switch whenever you want power, they need to work even when the underlying energy source is not there, e.g. at night if you are using solar power, or on a windless day if you use wind turbines. The argument is that these systems cannot provide base-load power because they only supply power when their energy source is available.

We’ve already seen that a coal-powered system relies on energy storage of a sort to smooth out demand in the form of storing hot water. This is a remarkably inefficient way of storing energy. To start with, a coal-fired power station loses up to 70% of the energy it consumes as waste heat. Of the remaining 30%, about 10% is lost in transmission. Then when you heat hot water using electric resistance, that’s also a remarkably inefficient use of electricity – and you are turning it back into heat, which is what you started with. Finally, since the water tank has to store energy across periods when the ripple relay is turned off and even when that’s not the case, it has to store enough energy that taking a bath doesn’t make the water too cold for the next use, you need to heat – and keep hot – a lot more water than you actually use for any one purpose.

The massive losses inherent in a fossil-fueled power grid are to some extent masked by the fact that coal is relatively cheap. However, coal is a depleting resource and will become more expensive over time – even if we don’t count the environmental costs of mining and burning coal.

To work this all out properly, you need to work out the available energy and costing. What I offer here is an idea of how a clean energy system could work.

First, a solar thermal (or concentrating solar) system an provide base load, if a sufficiently large store of heat is included. The way these systems work is by heating a salt mix past melting point, and using that stored heat to produce steam for a turbine. Heat storage on these systems can potentially extend their use over more than a day of low sun. What if you need to extend use even longer, if there’s an extended period of low sun? A solar thermal plant has to have a way of heating the salt mix initially, usually using gas. An option is to use excess power generating at off-peak times to create hydrogen by electrolysis, then burn the hydrogen when the sun is not hot enough to maintain the temperature. A system like this combined with wind could work well. When there was sufficient wind available, the wind power could provide base load and top up the stored hydrogen if there was any excess. On less windy days, the solar thermal plant would provide more of the power.

Is it not wasteful having all these alternative power sources? A conventional grid does this anyway. The large base-load power stations are backed up by smaller generators that can be turned on and off quickly, but at a higher cost per unit of electricity. Making all this work will require some hard engineering, but describing clean base-load as impossible is wrong. Hard, not impossible. So why should we bother? Because coal will not last forever, and because coal is dirty. Coal mines are massively polluting, coal transport is energy-inefficient and coal emits many harmful substances including heavy metals when burnt.

All of these would be good reasons to look for alternatives even without climate change. Add that in, and we need to start working seriously on these options. In Australia, there’s a 100% renewables campaign and the Beyond Zero Emissions group has researched clean base load power extensively. If South Africa could beat Australia into the lead position on the Square Kilometre Array telescope project, what’s our excuse for being so backward on clean energy?

Thursday, May 17, 2012

Sceptics or deniers?

In Mail&Guardian, I had a letter published in response to a claim that it’s wrong to label people as AIDS deniers. Here it is:
Here we go again (“‘Denialist’ label just as deadly”, Sam Ditshego, letters 3 May). The pseudo debate about HIV and AIDS is not unique. Science denial occurs in many fields: the link between tobacco and health problems, the ozone hole, climate change and evolution. If Sam Ditshego doesn’t want his position to be considered denial then he shouldn’t argue like a denialist. There is nothing wrong with being a sceptic. All good scientists are sceptics, and check claims made by other scientists, and indeed their own work, for errors and inconsistencies. When this sort of attack on science occurs, practising scientists face a damned if you do, damned if you don’t dilemma. Take on the denial case and you give it additional publicity, with the serious problem that refuting it comprehensively requires airing science that cannot be explained in full to the non-expert. Ignore it, and it appears that it can’t be refuted.
Here are the key properties of a denial campaign that distinguish it from healthy scepticism:
  • Gish gallop – a debating technique invented by Duane Gish, an evolution denier, who evidently saw no contradiction in being a fundamentalist Christian and lying. The technique is to spew out apparent facts scatter-gun style. It takes only a few words to lie; it may take a lengthy, carefully constructed argument to refute the lie, giving the liar a huge advantage in any debate format with limited space (letters to the editor) or time (a public debate)
  • repeating discredited arguments – a denial campaign is not concerned with arriving at the truth (or the closest we can get to the truth in the face of uncertainty) and therefore recycles old arguments, no matter how the field has advanced; a sceptic would happily concede error if proved wrong
  • accepting contradictory positions – a true sceptic would not accept any argument to support a cause. If some were contradictory, a sceptic would be forced to thin down the range of positions to those that were mutually consistent
  • argument from authority – a whole slew of eminent people support the case therefore it has to be right. Never mind that some of them made their claims a decade or more ago, and may have died before their claim turned out to be false, or that they are not all experts in the field. A few genuine experts of course may put themselves out on left field but the fact that they are isolated fuels the conspiracy theory mindset. That doesn’t mean these people are right. Someone who’s at the top of their field who makes a mistake has a big investment in their position and may find it hard to back down – especially if their error cost hundreds of thousands of people their lives
  • reducing science to a matter of opinion – science, unlike politics or religion, is not a matter of opinion. It’s a matter of evidence. A scientific theory stands or falls by evidence. If after several decades of expressing doubt about a theory, “sceptics” are repeating the same claims that have been refuted many times, they are no longer practising science, but some sort of religion or political ideology, and rightfully deserve the “denier” label
  • accusing the other side of the very flaws in their own argument – a genuine sceptic should be able to make a case purely based on the evidence. There is no need to accuse others of politicising their science, turning science into a pseudo-religion based on belief rather than evidence or chasing research funding by predicting disaster. It is very hard to argue against this sort of tendency without appearing yourself to be attacking the messenger rather than the evidence, which is why I leave this point to last.
Let’s contrast this all with a genuine case of scientific scepticism that took on a mainstream view: the 1982 discovery by Barry Marshall and Robin Warren that stomach ulcers are caused by bacteria. They had a tough job convincing the scientific community that they were right against the conventional view that bacteria couldn’t survive in the highly acidic environment of the stomach; they produced the evidence to overturn the mainstream view and were rewarded with a Nobel prize.

The real question we should ask ourselves is why certain areas of science attract this sort of dogged faux controversy. There are many other areas of science where there are conflicts between scientific integrity and economic or political interest, and these conflicts are generally resolved in the scientific literature – but these conflicts do not generally imply major society-wide changes in human behaviour if the science is correct. HIV is an outlier because there is no obvious commercial interest in traducing the mainstream. Climate change, tobacco and the ozone hole are all areas where the science threatened commercial interests (denying evolution in a sense supports a commercial interest, because there is big money in organised religion).

What is clear though is that it’s very hard for members of the public without a scientific education to see through this sort of thing, which puts a huge onus on journalists to spot and deflate this sort of campaign. Remember the old adage: fool me once, shame on you. Fool me twice, shame on me.
Why do I quote this here? Climate change and many other environmental causes like the ozone hole are also subject to this sort of fake “scepticism”. The pattern of argument is always the same. Many people argue that it’s the fault of scientists that they cannot win against this sort of fake attack on science. I argue that it’s really a failure of journalism. The mainstream news media do not follow the markets report with a Trotskyist rebuttal. We do not follow the weather report with a witch doctor throwing the bones and giving a different answer. Why do some stories require “balance” and not others? The pattern of this sort of anti-science campaign is so depressingly familiar that I immediately saw the similarity between the anti-climate science campaign and the pro-tobacco campaign; I’ve since discovered there is just such a link.

If the mainstream science in any of these area is truly flawed, a scientist who works with the evidence will unearth this fact. That most of the argument against a particular area of science is couched in emotional terms, attacks the personal motives of scientists and uses bogus debating tactics has to tell you something.

If climate change is really not going to happen, that would be a huge relief, so I’ve studied the contrarian literature extensively. Sadly, none of it fits the evidence nearly as well as the mainstream. I say “sadly” because, as the tobacco industry revealed, this sort of attack on science can delay effective policy change by decades. And as many studies have shown, the longer we delay, the higher the cost.

Sunday, April 22, 2012

Solar hot water or heat pump?


With the growing price of electricity and increased awareness of climate change, increasing numbers of people are turning to solar hot water or heat pumps.

The way solar heating works is obvious: you have an energy collector on the roof that picks up energy from the sun, and heats your water. A few details may be less obvious, like why you still get hot water after dark with minimal electricity use, and how it can work on a cloudy day.

A good solar system can heat the water in the tank to up to 95°C, and reduces the temperature at the tap by using a tempering valve, which mixes in cold water to keep your hot tap water down to a safer level. You store energy in effect by heating the water more than you need to when the sun is out. What then about when the sun’s obscured by cloud? Some energy obviously still gets through because cloudy days are mostly warmer than cloudy nights. A good modern solar hot water system can at least maintain temperatures on all but the cloudiest days, and even increase the temperature if it falls as a result of using hot water. Wikipedia has a detailed discussion of different types of heat collectors, and their advantages and disadvantages.

What of heat pumps then?

A heat pump is based on a law of physics: the ideal gas law, which says that temperature is a direct function of pressure, if nothing else changes. One effect of this is that if you increase the pressure of a gas it gets hotter; another is if you drop its pressure it gets cooler. The picture on the right illustrates the principle of a heat pump. If you have a fixed amount of gas and pump it in a fixed-sized container from one side to the other, with a valve that can be closed to allow the pressure to be high on one side but not the other, you make the high-pressure side hot. If you then vent some of the gas to the low pressure side, while keeping the pressure lower than on the other side, it cools. You can use this principle to make a fridge or air conditioner, by routing the high-pressure side of the container through a radiator on the outside of the space you need to cool, and let it cool a bit, before releasing it at lower pressure to the cold (low pressure) side of the system.

A heat pump (or for that matter, a reverse-cycle air-conditioner working as a heater) reverses the role of the two sides. You use the hot side and radiate out the cool side to the outside world.

The key to understanding the whole thing is that the side you don’t want (the hot side of a fridge or aircon, the cold side of a hot water system or heater) has to be able to get rid of its unwanted temperature differential to the outside environment. A fridge or aircon does this simply by radiating away heat; a heat pump may need to be more aggressive in getting rid of unwanted cold with a fan.

A heat pump is a far more efficient process for heating than using electrical resistance to create heat.


How much more efficient?

When I used to live in Australia, I had the benefit of a dual electricity meter, with a separate one for water heating because we had the option to pay a lower off-peak rate for electricity. I was able to observe the benefit of changing to a heat pump directly (picture at  left, note the fan to expel cold air; some models are split in two parts, with the heat pump machinery separate from the tank): a drop of 80% in electricity usage for hot water.

That sounds dramatic, but remember it’s 80% of only one component of electricity usage, and this was in a two-person household with relatively light water use. The benefits you see may vary depending not only on your usage pattern but the efficiency of the system (for example, if the heat exchanger is not well sited, you will get a lesser saving). Solar systems with electric backup reportedly save 90% of hot water electricity usage.

Which type?

So, the bottom line: should you get solar hot water or a heat pump?

It depends. A heat pump, while slower than a traditional resistance heater to fully reheat a large water tank, can top up lost heat overnight even when there is no sunshine. A good design can take heat out of the air at a temperature as low as -10°C. If you use a lot of water overnight, you may find this better overall than a solar system – though a solar system with a bigger tank may still come out ahead. The best case for a heat pump is when you don’t have a roof on which to install the solar collector (e.g., if you are in a ground floor flat). In Brisbane, I installed a heat pump because I wanted my roof space for solar power – we could feed our solar power into the grid and earn a premium price of almost 3 times the retail price for excess electricity, not yet an option here.

For my house here, I decided to go for a solar collector because I have plenty of roof space – and because it works even if the electricity is out. So far, it’s been pretty good. It took a few days (including some that weren’t too sunny) to build up to full heat but since then the water has been pretty hot even on cool cloudy days. The only problem I’ve had with mine is that the installer promised that a fibreglass resin odour in the water would dissipate quickly, but it lingered for months. It’s hard to compare before and after electricity bills because I wasn’t in the house long enough before installing it, and other electricity use may have changed, so I am not going to make any specific claims.

Thinking long term

As the price of electricity goes up, solar hot water or a heat pump should become standard in new dwellings and when replacing existing systems. It’s great that solar hot water is being installed free of charge in poorer communities (even if the target of 3,000 houses in Makana looks low). Many of these households would never have been able to afford hot water otherwise: even if they could scrape together the money for a system, they would battle to find the cost of the extra electricity. And if we are serious about climate change, we need to make it easy for those who already have a low carbon footprint to stay that way without being disadvantaged.

Monday, February 13, 2012

Making your own bread

In Grahamstown, we have our very own artisanal baker, who shows up at markets and whose bread is available at a couple of places around town, including Lungi’s farm stall in the Peppergrove mall.

But what if you miss out, or it’s one of those bad days when baking doesn’t go to plan?

Making your own bread is really easy if you use a good flour and the right technique. Sourdough is much harder; you can get good results using commercial dry yeast.

Here are a few hints:
  • slow is good: don’t believe claims that you should hasten the activation of the yeast
  • thorough mixing is the key; kneading is less essential than you’ve been lead to believe (it can’t hurt, but it’s a pain when you are making a sticky dough as in brown or ciabatta loaf)
  • good fresh ingredients make a big difference
  • brown or whole wheat needs  a wetter mix than white
So here’s how I make a good loaf out of stone-ground brown bread flour.
  • 500g flour
  • 5g dry yeast (half a sachet)
  • 400ml water

Mix the yeast into the flour thoroughly, add the water and stir vigorously until the ingredients form a smooth dough.

Leave the dough in a cool place until the dough has at least doubled in bulk. On a coolish summer day, I leave it most of the day (about 8 hours). Stir vigorously again, knocking out all the gas. Now grease a bread pan (I use butter; a fraction of a gram per slice will not kill you and it works well), and add in the dough. Leave it in a cool place to rise until it’s about doubled in bulk (3-4 hours, but the time will vary depending on the temperature). Bread made this way is not going to rise much in the oven, so don’t bake until it’s close to its final size.

Bake at 180°C for 30 minutes. Test the bread by tapping on it: if it sounds hollow, it’s done. You can also do a skewer test: the skewer can be a little sticky but not very sticky when you pull it out. When done, wrap the bread in a slightly damp towel if you don’t like a hard crust, otherwise let it cool on a wire rack.

Here’s the end result. Did I hear someone say a gas oven is no good?
You may have noticed I cook without salt. Salt is over-used in cooking and most people are de-sensitised to excessive salt. Get used to less salt and your sense of taste develops a new range. And you are less likely to develop high blood pressure.

If you choose to add salt, add it well separated from the yeast before mixing the dry ingredients. Salt kills yeast.

Sunday, February 12, 2012

Cooking with gas

With all the protests against fracking, it's easy to get the idea that cooking with gas is bad. First, most household gas in South Africa is liquefied petroleum gas (LPG), which is not produced using fracking. Second, in the long term, we should be looking at biogas as an option for cooking. Why? Because electrical ways of producing heat are wasteful. For heating water or heating the air in winter, you can use a heat pump, but for concentrated heat for cooking, a heat pump is way too slow.

Back to fracking: it’s idiotic to scrape the bottom of the barrel for the last drop of fossil fuels. They will run out anyway, and climate science indicates a need to look at alternatives. So why try to extract gas from environmentally sensitive water-poor land with technology that carries serious risks?

Some people are  pushing induction cookers as an alternative, citing numbers that show them to be by far the most efficient form of cooking. These numbers are a bit misleading because they don’t take into account the extremely low efficiency of coal power generation, by far the most common source of electricity in South Africa. A typical coal power station has an efficiency of around 30%, and you lose about 10% more in power transmission, so you have to start counting the energy efficiency at your stove at about 27% (not taking into account the energy cost of mining and transporting the coal, but gas also has a production and transport cost we are not taking into account).

LPG is a very efficient fuel if we must burn something to make heat. However, if you buy an LPG stove, take care to get one that can be rejetted for natural gas, since biogas is closer to natural gas. LPG sold in South Africa is a mix of propane and butane, and has a very high energy density, higher than natural gas, which is mostly methane. Natural gas and LPG are fossil fuels, and switching to a more efficient one is only a step: we should ultimately aim to stop burning all fossil fuels. In the meantime, though, LPG is a better alternative than a wasteful electric stove.

If you are buying a gas stove, what should you look for?

First, quality materials. Look for cast-iron pot stands. The kind that look like plastic-coated wire don't last long. A stainless steel outer case is good, though no substitute for quality working parts. Ask a person who repairs appliances (ideally someone who doesn’t sell new ones) which brands have best after-sales service, parts availability and general reliability.

Now the critical question: how well does a gas stove work? Many people will tell you that they are great for stove-top burners, with their near-instant heat adjustment, but a gas oven is no good. I’ve previously had a gas stove nearly 100 years old with a very good oven, so it really depends on how well the stove is designed. My shiny new stove has a gas oven, and I’ll report results here shortly (see a hint in the picture).

Watch this space.

Sunday, January 8, 2012

You can’t do that with electricity

Much debate about energy centres on replacing coal power stations with something cleaner, yet that is not really the hardest energy problem. We already know how to do renewable electricity generation. Reducing cost and finding more efficient ways of storing energy to work around intermittency are engineering problems that can be solved in time.

Once you solve those problems, short-range transport can easily be fixed, as can long-haul overland transport. Get as many people as possible into electric trains, trams and trolley buses, and convert cars over to electricity wherever practical. In South Africa we have some big practical problems such as persuading business that rail freight is reliable, and re-architecting cities for public transport, but these are problems that can be solved with the political will to do so.

Ships can potentially convert over to wind: sailing ships were pretty fast by the time they were replaced with steam and with modern materials and weather prediction, we should be able to do better. We can eliminate some of the larger cargo requirements (oil: we won’t ship that around as a fuel in a clean energy world; ores: better processed closer to source if you care about energy). There is in the meantime a variety of technologies that can be used at least as partial (hybrid) solutions to reduce the carbon footprint of shipping; once these develop further, we could see a return to real sailing ships, but without the huge crews required for 19th-century technology.

The much harder problem is where air travel is the only option. Air travel requires energy storage of high density both in volume and weight. Hydrogen has great energy density in terms of weight, but not volume. Electric aircraft are impractical because batteries or fuel cells have too low an energy density, which cannot be offset by the much higher efficiency of converting stored electrical energy to motion, as compared with converting heat to motion.

We aren’t likely therefore to see electric intercontinental planes built the same ways as jet aircraft. That doesn’t mean however that there aren’t other form factors that could work. For example, several experimental electric helicopter projects are active. Current prototypes are only good for short flights (up to 6 minutes in one case) but the key to these designs is minimal weight, making longer flight times viable with bigger batteries. This seems to me a more promising approach than that of helicopter giant Sikorsky, who have replaced the engine of an existing design with an electric motor in a design that’s yet to fly. It’s unlikely that we will see an electric helicopter capable of flights of an hour or more any time soon, but it’s interesting nonetheless that it’s possible to do this with something bigger than a toy.

Yet another possibility is to power airships with hydrogen. You can store the hydrogen in the gas bag (possibly along with helium to reduce the fire risk) and, as you burn it, drop ballast to keep the weight constant (in a form that will not cause damage as it falls, e.g., some of the water created from burning the hydrogen). I haven’t done the arithmetic on the volumes needed and how long a trip this would work for but I’m not the only one to have thought of the idea.

There are many exciting possibilities for new energy technologies out there. Let us not limit our imagination by thinking that burning stuff we can’t replace has brought us to the pinnacle of civilization, and it’s all downhill from here on.

Sunday, January 1, 2012

The Oil Journey

Here’s a thoughtful video relating economic progress, social progress, and environmental progress – and growth in energy use since fossil fuels began to be used on a large scale. Worth watching if you have half an hour or so. The main point: even without considering climate change, the decline in high quality energy sources implies a major change in the energy economy.

Skeptical of the Skeptics

One thing I constantly run into when talking about climate science is self-styled skeptics, who, we are given to believe, are the true custodians of science because they are “skeptical” whereas actual scientists are, we are led to believe, naïve simpletons who believe everything they’re told and follow the herd without question.

One example of this phenomenon is the “rogue scientist” who apparently possesses a unique wisdom, inaccessible to others in the field. A prime example of this is Steven Levitt’s pair of books, Freakonomics and SuperFreakonomics, that purport to overturn conventional wisdom in a large number of fields (OK, he’s an economist not a scientist, but he still presents as a “rogue”). This stuff is entertaining reading, but it is it really such a challenge to convention?

American Scientist has a thoughtful article on some of the errors of these two books; I recommend that anyone enamoured of the rogue scientist meme read this article. It’s also well worth reading Raymond Pierrehumbert’s (aka Raypierre) rather thorough debunk of one point in SuperFreakonomics.

Sadly, it’s a lot easier to spew out a long stream of pseudo-facts and incorrect science than to debunk that sort of thing. One final piece of holiday reading: understand what a Gish Gallop bogus debating tactic is.