Current breakthroughs in electricity generation and distribution go under the spotlight in this week's sizzling edition of the Naked Scientists. We talk to the team with the electrical equivalent of cold-storage that can put power "on ice" until it's needed, and we hear how bright sparks in the UK are leading the charge to roll out "energy kiosks" to empower rural communities in Africa. We also check out a new form of small-scale turbine to extract power from rivers whilst minimising the environmental impact. In the news, why young people are more likely to fall victim to the flu, how a dose of worms controlled a man's inflammatory bowel disease and why the discovery of arsenic-loving bacteria is forcing us to rethink the chemistry of life. Plus, in Question of the Week, Diana gets to the bottom of whether it's possible to drink through your rectum...
In this episode
01:55 - Why pandemic flu kills the (apparently) least vulnerable
Why pandemic flu kills the (apparently) least vulnerable
Researchers in Buenos Aires and Nashville have come one step closer to finding out why it is that those members of a population who should be the fittest (i.e. young and middle-aged adults) are the most likely to die during a pandemic flu outbreak.
The most recent bout of flu to receive media attention was in 2009 with H1N1 or swine flu. It killed 17,000 people worldwide during its peak. Fernando Polack and colleagues found that the elderly were spared the worst of this outbreak and that the very young suffered a much milder form of the disease than the adults. They suggest that the killer of these young and middle-aged adults was their own immune system.
Publishing in Nature Letters, the researchers took sections of the lungs of victims of the 2009 pandemic and found that their lung tissues were inflamed, heavily damaged, had traces of H1N1 but had huge amounts of the biomarker C4d. C4d is a by-product of the body's immune response, so it's a good indicator of how vigorously your body is fighting an infection.
The researchers also looked through some lung sections from victims of a previous H1N1 pandemic in 1957. From these aged samples they again found evidence of a strong immune response. What they think is happening is that the immune system in these individuals mounts a response based upon its knowledge of bog-standard seasonal flu. This immune response is ineffective against H1N1 but it is vigorous and so it ends up killing the patient.
The researchers hypothesise that the elderly escape because they were exposed to the previous pandemic, in 1957. And they think that the young escape because their immune systems haven't been trained by 'ordinary', seasonal flu. So the next step is to find out who has the immune system which is most likely to overreact to pandemic flu and the authors think genetic testing will be key.
04:40 - How worms can treat bowel diseases
How worms can treat bowel diseases
For many years scientists have known that carrying intestinal parasites seems to reduce the risks of inflammatory diseases and allergies. But now a patient treating himself with a dose of worms to combat inflammatory bowel disease has given doctors a unique insight into how such a benefit might arise.
Writing in Science Translational Medicine, University of California, San Francisco scientist Mara Broadhurst and her colleagues present the case of a 35 year old man with a history of ulcerative colitis, an inflammatory condition of the large intestine that causes pain, bleeding and diarrhoea and carries a risk of colonic cancer.
But rather than undergo a colectomy to remove a severely diseased segment of his bowel, the patient instead elected to infect himself with 1500 eggs of the human roundworm, Trichuris trichiura, which establishes a long-term colonisation of the human large intestine. Shortly after the patient ingested the worm eggs his symptoms resolved and telescope camera studies of the bowel showed that the previously inflammed tissue was now apparently normal. The patient experienced a few mild flare ups of his symptoms but otherwise remained well for 3 years.
When his symptoms began to return the researchers noticed that the number of worm eggs present in the man's faeces had dropped, suggesting that the worm burden in his bowel had also decreased, thus explaining the return of the symptoms. This was confirmed with further colonoscopies that showed that areas of the bowel where the worm count was low now had signs of the disease returning. At this point the patient re-dosed himself with a further 2000 worm eggs and again his symptoms remitted.
As they had been following his progress throughout, the medical team had been able to take samples from the bowel during the course of the investigation, which they analysed biochemically, anatomically and genetically.
The results show clearly that in disease-affected areas of the gut there is intense inflammation and the presence of large amounts of an inflammatory hormone called IL17. But in the worm-treated intestinal samples the inflammation was absent and there were also large numbers of cells secreting an additional immune signal called IL22. This factor appears to stimulate the growth of epithelial cells that line the intestine, promoting healing, and also increase the secretion of protective mucus, helping to shield the gut wall from inflammatory stimuli. This reaction is intended to rid the bowel of the worms, but appears to have the effect of promoting healing.
This study therefore offers unique insights into how worm-therapies might work to combat inflammatory and allergic conditions. However, the team do point out that worm infestations can cause malnutrition, bowel inflammation and other complications, especially in children. Studies like this might therefore lead to the creation of an artificial "pseudoworm" that could have the therapeutic benefits but without the risks...
09:14 - Thriving on Arsenic - Rethinking the Chemistry of Life
Thriving on Arsenic - Rethinking the Chemistry of Life
with Professor Paul Davies, Arizona State University
Chris - This week, a team from Arizona State University have announced the discovery of bacteria that can thrive in an environment laced with arsenic. This is a chemical that's normally very toxic, but not only can this bacteria tolerate it, they can even use arsenic instead of phosphorus which is normally a critical element in DNA. Professor Paul Davis from Arizona State University is one of the authors on that paper which announces the discovery this week in Science, and he is with us now. Hello, Paul...
Paul - Hello. Welcome from Arizona.
Chris - Thank you. First of all, what actually is the bacterium that you've been studying and how did you come to isolate it?
Paul - It's a common garden bacteria - it's not a weirdo. It didn't stand out as being anything odd. And if it wasn't for the brilliant insights of my colleague Felisa Wolfe-Simon, who incidentally is now working at the US Geological Survey in Menlo Park, then we would never have known that there was any amazing arsenic capabilities, but she had a hunch some years ago which we then developed here at ASU into a full hypothesis. There could be organisms that can replace phosphorus with arsenic, these would be, as it were, arsenic life, and she went to look for them in Mono Lake in California which is heavily contaminated with arsenic. So, it was a shrewd place to look but we would never have known if she hadn't fed them on diets with huge amounts of arsenic and zero phosphorus.
Chris - So what happened was she initially got the samples of bacteria from the lake which are tolerating a degree of arsenic in the environment and then by forcing them to live in an environment that's very arsenic-rich with no phosphorus, they were able to substitute arsenic into their actual behaviour, biochemically, in terms of DNA, lipids, and everything else that keeps their cells going, and use arsenic in place of phosphorus.
Paul - Absolutely right. They took the arsenic into their vital innards - this was an important point. Of course ideally, we wanted to go somewhere where there was much more arsenic and much less phosphorus, and there are places on Earth, like deep ocean volcanic vents but they're expensive to get to, Mono Lake is convenient. Also, there has been work down there by Ron Omland at the US Geological Survey studying organisms that flirt with arsenic, but nobody other than Felisa and a handful of us had really expected to find anything that did more than that flirtation, that would actually take the arsenic into their innards and use it to substitute the phosphorus. And so, this is the first because all along, biologists have assumed that all life is built out of the basic toolkit of six elements: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulphur. And here, we have an organism that departs from that basic tool kit.
Chris - Chemically, why is it possible for this bacterium to substitute arsenic for this - what we previously thought of as absolutely critical element - phosphorus.
Paul - Well, arsenic is a poison precisely because it looks chemically like phosphorus and so, that's the reason that led us to think that this might happen, but we don't understand the mechanism. We don't know who's shifting the gears inside these little bugs, what actually is going on. All we could tell is the phosphorus is getting replaced by the arsenic. Ideally of course, we'd like to find an organism that right from the outset is arsenic through and through, and for which phosphorus is a poison. This is not it. This has dual capability. It likes phosphorus. It likes arsenic. It can deal with both and so, it can sort of mix and match, but the Holy Grail would be to find one that was an arsenic organism by obligation, not by choice.
Chris - But I think the point is, and the point that you make very well in your paper, is that this shows that if we complacently think that all life has to be based around these six building blocks that you've mentioned, one of them being phosphorus - actually, this is not true and we have an example here on Earth of how an organism can substitute a completely different element into its life. And therefore, this suggests that the opportunities for life to exist in an entirely different way than the way we understand here on Earth could well exist in outer space.
Paul - That's right. Well not perhaps outer space, but on a planet or moon that was rich in arsenic, but I think it proves an even more exciting point and that is, that you could have radically alternative forms of life, hiding in plain sight, right under our noses, just looking like any common or garden microbes. You can't tell by looking with microbes - what they're made of, what makes them tick. This study is part of the broader context to look for what we call a 'shadow biosphere,' or the search to see whether Earth hosts more than one fundamentally different form of life. Is there just one Tree of Life with lots of interesting branches, or might there be more than one tree? Now this particular organism is clearly on the same Tree of Life as you and me, but it does show because you can't tell by looking, that there may be even bigger surprises in store and if we follow the arsenic, see where that goes, we might find that we have an organism which simply can't even be fitted on the same Tree of Life as you and me, and that would show that life on Earth has started more than once and the implications of that are literally cosmic.
Chris - I was going to say that the life we see on Earth today is life which is adapted to the planet as it is now. If we were to wind the clock back 4 ½ billion years to the very early Earth, it was a very different place. It's possible that there were organisms like this abounding, and they were replaced by the ones that suit the planet as it is today.
Paul - Yes. The more conservative interpretation of this is that this is a sort of latter day adaptation to tolerate high arsenic conditions. But the more exciting possibility as you mentioned is that maybe life started out going down the arsenic route, for the simple reason that the favourite place among astrobiologists for life to begin are the deep ocean volcanic trenches where there's a sort of chemical brew being stirred around by the heat of the volcano. If that's the case, well, it's laced with arsenic down there, it's a very arsenic-rich environment and so it makes sense to think that maybe life started out with arsenic and only when it spread, then it started making use of phosphorus. So these things could be like living fossils, a hangover from those ancient days. It's too soon to say yet because we need other examples. If we have a whole collection of arsenic microbes, we could begin to do a phylogenetic tree, we can begin to see how ancient they are, how ancient the genes are, but it's early days yet.
Chris - And just to finish this off Paul, you've done this for arsenic, but what about the other elements that we know are critical for life? Is it possible that other neighbours in the periodic table of elements that are again chemically similar in the same way that arsenic is to phosphorus could be substituted in life, and therefore, we have other organisms that are using entirely different chemicals instead of those carbon, hydrogen, nitrogen, oxygen, sulphur, and phosphorus?
Paul - Well it's rash to rule anything out in this game of course, but the favourite is carbon being replaced by silicon, and that's so popular, it even made it to an episode of Star Trek. So, we have to take it seriously. But my chemist friends tell me that that's a pretty tough one and I think carbon would be the last to go, but we do have to take a look say, at sulphur, and also the possibility of the fact that possibly, phosphorus could be replaced with something other than arsenic. So, I think this is going to open the eyes of microbiologists and encourage people to look in a much wider range of locations, a much wider suite of chemistry than we have dealt with either two.
Chris - Should always take Star Trek seriously. Paul, thank you very much. That's Paul Davis from Arizona State University.
17:17 - Summer babies have more regular body clocks
Summer babies have more regular body clocks
Researchers in Nashville have found that the season in which mice are born can dramatically affect how their body clocks work in later life. Mice born in the summertime were better at adapting their body clocks to night/day changes than those born in the winter.
Publishing this week in Nature Neuroscience, Douglas McMahon and colleagues reared mice in artificially-engineered seasons. Some were raised with more 'daylight', emulating summer and some were exposed to more night time as they grew up.
Another sub-section of the mice were then exposed to a different 'season' during adolescence and finally, once they reached adulthood, all of the mice were put into darkness so that the researchers could observe how they scheduled their activities.
The winter mice in this environment slowed all their activities whereas the summer mice maintained a regular day-night cycle. So the researchers think that the circadian rhythm is actually imprinted on the brain during a key period in the mouse's development.
They also say that a "strikingly similar response" is present in people who suffer from SAD - seasonal affective disorder. The next step will be to find out exactly when this seasonal imprinting occurs.
19:10 - Drug that can wipe away pain memories
Drug that can wipe away pain memories
Scientists have discovered that they can switch off chronic pain by wiping out the brain's memory for the event that caused the discomfort. Chronic pain is a significant health problem for sufferers and also places a considerable economic and treatment burden on healthcare providers. But now, in a paper published this week in the journal Science, researchers have shown that certain kinds of pain sensation are very much "in the mind" and can be erased with a drug.
University of Toronto scientist Xiang-Yao Li made the discovery by working with mice genetically engineered to express a glowing green gene in neurones that had been affected by nerve injuries. When the common peroneal nerve, which supplies the hind limb was ligated in a group of mice, cells in the front part of the brain called the anterior cingulate cortex, lit up green. At the same time these animals showed signs of developing allodynia - or neuropathic pain - a condition of enhanced sensation in which normally innocuous stimuli - such as light brushing of a patch of affected skin - are experienced as extremely painful.
But when the team injected a chemical called ZIP (which stands for zeta-pseudosubstrate inhibitory peptide) into the anterior cingulate cortex, the allodynia symptoms vanished. ZIP inhibits an enzyme called phosphokinase M zeta (PKM-zeta).
This appears to play a critical role in controlling the strength of the synaptic connections between nerve cells. So when something is learned, PKM-zeta increases its activity in the synapse and sensitises the target nerve cells to nerve transmitter chemicals. PKM-zeta also promotes its own activity, helping to sustain nerve connections in their learned state.
But if ZIP is injected, this inhibits the enzyme, weakening the nerve connection and also preventing further PKM-zeta activity. Effectively it wipes away learning, and when injected into the anterior cingulate cortex the fact that it was able to make symptoms of allodynia disappear in awake animals indicates that some chronic pain states are "learned" by the brain and that it might be possible to use approaches like this to wipe the neurological slate clean and reset pain thresholds in patients.
23:17 - Planet Earth Online - Antisocial Ants
Planet Earth Online - Antisocial Ants
with Bill Hughes, University of Leeds
Planet Earth Podcast Presenter, Richard Hollingham, visited a small, hot, humid room at the University of Leeds. Inside this controlled environment he met Bill Hughes - who studies ants' social, and antisocial, behaviour - as well as some unexpectedly large insects...
Bill - These are dinosaur ants from Brazil. They're one of the largest species of ants in the world. They are about 3 ½ centimetres long. They have a pretty powerful sting on them, as you'd guess from looking at them, considerably more painful than a bee sting. They're interesting because unlike most ants which have a queen and worker class - as you would probably know - these are what we called primitively eusocial. They have an alpha female-beta female dominance hierarchy, so they're actually very, very similar to our vertebrate societies, wolf packs, meerkat packs, things like that.
Richard - So you could compare these to a much higher animal, like a wolf for example.
Bill - Absolutely. In terms of the social interactions within the societies, they're very, very similar. The beauty of them, from research, of course is that we can have multiple colonies of these ants here in this relatively small room whereas if you're trying to do the same kind of experiments with a wolf pack, you obviously couldn't.
Richard - They do look almost prehistoric, don't they? With a long pointed abdomen, almost like a wasp, a head with these pincers at the top, and these long legs out of the side, and these long antenna as well which are moving around.
Bill - Ants evolved from wasps and so you tend to find that the most primitive species of ants are very wasp-like in behaviour and also in morphology.
Richard - Now these are known as social insects, but what you're looking is the fact that they're not always that social - they can be anti-social.
Bill - Yeah, that's right. When we look at a social insect colony - in fact, just as when we look at a human society, it's obviously the cooperation that's the most obvious characteristic. It seems that the society is very egalitarian. As we've started looking in more detail at social insect societies though, we find out that there's actually an awful lot of conflicts within them because individuals aren't clones of one another. They're not reproductively identical. And so, their interests different to a greater or lesser extent.
For example, in these dinosaur ants, we have an alpha female, a beta female, and so on, a dominance hierarchy - but because they are morphologically the same, there's a lot of potential for subordinate females to try and reproduce, and they do do that. They'll lay eggs. The alpha female will normally detect the egg and will police it by cannibalising it. In fact, the alpha female's particularly clever because rather than just using physical aggression to exert her dominance like in a wolf pack, she actually uses chemical cues to do it. So if she detects that a subordinate female is challenging her, she will smear than individual with the venom from her sting - she doesn't sting the subordinate - she smears it with venom and that acts as a signal which causes the other individuals in the colony to act aggressively towards that challenger, and to spreadeagle the challenger. So she's really quite clever rather than enforcing her dominance herself, she uses the other individuals in the colonies to do it.
Richard - Okay so, you've got these dinosaur ants which have been around for about 100 million years or so, but you got more recent ants in here - leafcutter ants.
Bill - Yes. So these leaf cutting ants show a much more advanced form of sociality than we see in the dinosaur ants. You can see they've got tiny, tiny workers, much larger workers, and then the queen is huge. So a larva, when it's developing, they may develop into a worker or they may develop into a queen, and theoretically, they're all meant to have an equal chance. It turned out though when we've used genetic methods to look at the kind of dynamics within them, that it is not actually equal and that individuals which are the offspring of some fathers have more chance of becoming a queen than others. So they're essentially cheating their nest mates out of the fair chance of becoming royalty and one of the obvious explanations might be that there's some form of nepotism going on because these maggot-like larvae are being reared by adult workers, maybe if the adult workers are able to recognise the larvae that they're more related to, they could preferentially care for them. Theoretically, that shouldn't occur. We've just been looking at these recognition cues which these ants have on their cuticles, and we found that actually, there is the information there to allow individuals to recognise their kin. So it's one of those examples where we had a very strong prediction from theory, but when we've actually been able to use very advanced chemical and genetic techniques in combination, it turns out that actually the information is there. So, it may be that they don't use that information - we still have to find that out - or it maybe they do and possibly that explains this form of royal cheating that we see going on in this colony.
28:19 - Energy Kiosks - Providing Power to Rural Africa
Energy Kiosks - Providing Power to Rural Africa
with Daniel Choudhury & Christopher Hopper, E.quinox
Diana - Across the developed world, we tend to take it for granted that we can simply plug in a kettle or a computer, and there's electricity on the tap. But in many parts of the world, this simply isn't an option. Much of rural Africa is off grid. And as electricity grids are expensive to build and maintain in places where they do exist, the electricity can be prohibitively expensive. But Meera Senthilingam has been to find out about a new and surprisingly simple solution which is being pioneered here in the UK, to take affordable power to those that need it.
Meera - Rural electrification is one of the biggest challenges facing the developing world with billions of people worldwide living without access to electricity. Countries such as Rwanda have tried to tackle the problem by increasing access to the grid. But due to expense, maintenance, and infrastructural challenges, the problem still remains. As Rwandan local, Simon Bataringaya explains.
Simon - Electricity is a big problem in Rwanda. Lighting around is a big problem. Security problems comes up with it. Hours of working are limited due to that short period of time of lighting. According to our figures, the census that was made towards the end of 2009, 7 per cent of the population of Rwanda have access to electricity. More than 90 per cent of the population of Rwanda lives in rural areas. For those, only 0.1 per cent have access to electricity and to be quite clear, the total number of the population is more than 10 million. So electricity is ever still a problem to Rwanda which limits their development.
Meera - Simon Bataringaya in Rwanda. Currently, residents of Rwanda overcome these limitations by burning kerosene and candles to provide light as well as paying to use generators at markets. But now, a team of engineering students from Imperial College London have developed the project E.quinox. Solar powered energy kiosks located in rural areas that charge and provide battery packs to locals. The first kiosk was located in the district of Manazi, with another updated design opening in the district of Bugesera. Vice Chairman of E.quinox, Daniel Choudhury explains more.
Daniel - The energy kiosk concept is a centralised charging station. The latest solar kiosk has 10 solar panels on the roof. Simply put, the solar panels will charge these battery boxes. People will take them away and once they've used it for various applications, whether it's lighting, charging their mobile phones or radios, they'll bring them back and the energy kiosk will charge it back. Solar panels are wired through charged controllers then they reach a large storage battery. What this allows is that if you have rainy days or foggy days, and you don't have enough sunshine, it provides a source of backup power.
Meera - You have examples of battery boxes in front of us, starting with the original box and also, the current box that's being used. The main difference I see between them is the size. Tell me a bit more about the actual battery boxes.
Daniel - So the original battery box is 12 ampere-hours in size and the new one is about half that size, 5 ampere-hours. The old one provides 12 volts of DC supply and the new one provides 230 volts through an inverter which is included inside the box. What this means is that the new box is basically a portable plug, so you can plug-in just about anything that's generally low-powered. So whether it's your mobile phone charger or simply the lamps we provide, it'll be able to power it.
Meera - So the setup in Bugesera as you mentioned, how many battery boxes are provided there and how much power is generated as a whole?
Daniel - The Bugesera Solar Kiosk has 10 solar panels which have 65-watt peak each and we serve 120 households using our battery boxes.
Meera - It all is largely kept going by the fact that you charge a fee to users. So what is this fee and how was that actually set?
Daniel - People will pay an initial deposit of about £10 and a 2 monthly recurring fee to charge the battery boxes. The money generated is used to pay for the shop keeper and for maintenance costs within the kiosk. We based this price on kerosene and people's kerosene usage so that it doesn't add up on their cost, but replaces the cost of buying kerosene for their energy needs. So while kerosene can be used for lighting, our battery boxes provide an additional service of say, charging your phones. Everyone has two mobile phones and the network is sufficient there, but they just need a point to charge their phones.
Meera - Daniel Choudhury, Vice Chairman of E.quinox Energy Kiosks. The technology Daniel mentioned however isn't limited to solar power, as the team have recently adapted their design to tap into other renewable energy resources, as well as tap into the grid. Chairman Christopher Hopper told me more.
Christopher - At first, it might seem counter-intuitive: Why do people by the grid need battery boxes? They have the grid! But the fact is that quite a lot of people don't have access to the grid even though they live close. In fact, some people live under grid line and they live in the dark after 6 o'clock. There's two main reasons for that. Number one, often people can't afford the grid connection, number two, some people could afford it, but they live too far away from the grid. Close but not close enough to be connected. So we think that by putting grid-connected battery charging stations along the grid, you can kind of extend the reach of the grid.
Meera - But as well as this main source of energy, you're also now exploring the potential of hydropower in the future.
Christopher - We want to develop a flexible solution. We know that energy kiosk is a flexible solution for electrification. So particularly, Rwanda has a lot of hydropower potential. It's a very hilly country. In fact, it's called 'Land of a thousand hills'. Quite a lot of rain as well, so there's many little rivers that we can make use of. When I talk about hydropower, I don't talk about huge dams, big power plants, but rather really, really small scale hydro generation - picohydro. So a couple of hundred watts of continuous power would be enough to power a small community. What's particularly attractive is that hydro gives you around-the-clock power. So if you combine that with a buffer battery for example, you can really charge a lot of small battery boxes to cater to local demand. So basically, if you compare it to a solar powered kiosk, for example in Bugesera we have 650 watts solar power, so 100 watts of continuous hydropower would be the equivalent to power a smaller sized community.
Meera - And providing this portable power by manipulating different methods of energy generation could pave the way for the future of all rural electrification.
Christopher - The classical way of grid electrification doesn't really work. Just like people in Africa, a big part of the continent has skipped the whole landline connection for telephones. We think this battery box concept can be the equivalent of mobile phones in power distribution because it's a much more flexible solution than hard wiring every single house. Studies from the World Bank that say that even if every household was connected to the grid, more than 50% couldn't even afford it to pay for it. So, you really have to rethink the way you approach the problem. In the end, we hope to really scale it up because it's not just about Rwanda, but rather you want to develop a versatile solution that can be replicated on a large scale to really achieve impact and to change people's lives.
44:24 - Isentropic - Storing Energy In Gravel
Isentropic - Storing Energy In Gravel
with Jonathan Howes, Isentropic
Chris - Now one of the outstanding problems in energy provision is how to store it in such a way that the energy can be accessed rapidly and efficiently on demand - in other words, when you want it. But now a Cambridge based company called 'Isentropic' has developed a cutting edge solution using gravel pits as enormous batteries where they store energy thermally. To explain how it works, Technical Director Jonathan Howes is with us. Hello, Jonathan.
Jonathan - Hello, Chris.
Chris - So first of all Jonathan, tell us what actually is the problem that you're grappling with here?
Jonathan - This came about as a result of some thinking I was doing in the mid to late 1990s when, like many engineers, I was quite keen on clean power generation methods. The more I looked at it though, the more I realised that we were actually trying to solve the wrong problem because there were plenty of people working on clean tech ways of making power. But the big problem with all of these is that they're either very inflexible, like for example nuclear, or very extremely erratic such as wind or solar. Tidal is less erratic, but it still comes and goes with the tides inevitably. So, the more important problem to solve was to buffer energy so that the intermittency problem or the inflexibility of nuclear would then go away. This would actually enable the widespread adoption of these other technologies. The real concern for me was always sustainability rather than clean tech because the opposite of sustainability is unsustainability which is self-evidently a silly way to go. So, this struck me as being the bigger problem. In solving the issues of making sustainability achievable, you inevitably end up cleaning power supply anyway because sustainable almost by definition means clean.
Chris - To put this into perspective and to give an everyday context to it, one of the big problems that power supply companies grapple with is Eastenders finishes or some other hot television program finishes, everyone gets up, whips on the kettle, turns the boiler and the lights on, and so on, and there's a big surge. You've got to have capacity there to cope with that and that means you've got to run stations beyond demand in order to have the spare capacity in the system to meet that demand.
Jonathan - Yes. This is the load levelling problem which is the definition of the short term storage issue. There are two primary storage problems. One is long term or seasonal storage. Perhaps storing energy during the summer when it's plentiful for use in the winter. The other one is the short term load levelling as you've just described for the local peaks and troughs in demand.
Chris - So tell us about Isentropic's solution then. What are you doing and how does it work?
Jonathan - Okay. What we are doing - this is a thermodynamic approach. If you consider a heat engine, as you'll find under the bonnet of a car, it produces a temperature difference, usually by burning a fuel. They don't have to do it by burning a fuel, you can use solar energy to create the temperature difference. That temperature difference then passes through a device and produces mechanical power.
Now there's an opposite of this called a 'heat pump' which is again, well-known but I think perhaps it's not quite so widely appreciated that heat pumps are in fact exact inverse of an engine. And a heat pump takes mechanical power through the shaft and converts it into a temperature difference by pumping heat from one place to another. If you can make a heat pump sufficiently reversible, thermodynamically reversible, you have the possibility of using it to pump heat from one volume of thermal mass to another volume of thermal mass, and then allowing it to discharge back through a similar or the same device, back to its original state, and then releasing the power that was used to create the temperature difference.
Chris - So, to explain practically how this might work, I would consume electricity from the grid. I would use this to do some work, moving something from one place to another place where there'll be a temperature difference which I can store. And then when I want the energy back, I can move the thing from the place where it's at one temperature to the other temperature, getting the energy that I used in the process back out - at some degree of loss obviously, there's no such thing as 100% efficiency yet - and that means that then you've stored the energy somewhere, until such time that you'll need it, but you can recover it from that thermal difference.
Jonathan - That's exactly correct. It's exactly analogous to pumped hydro where water is pumped from one level and one lake to another lake, and then it's consuming energy, and then allow it to flow back down again through a turbine to release the energy again. Where they pump water up and down a hill, so altitude represents temperature, we pump heat up a thermal hill to a high temperature reservoir.
Chris - And what are you heating up? What are you cooling down to make your thermal difference?
Jonathan - We have an engine circuit which runs an inert gas, namely argon, through a compression and expansion process. If argon is compressed, or any gas is compressed, the temperature rises. Having raised the temperature of the gas, it's then passed through a particulate store, a mineral particulate store which in its simplest form could be regarded as gravel. Although of course, you could use a ceramic or something more sophisticated, there's every reason not to for reasons of cost. It leaves the heat behind in the particulate and that cools back down to its original temperature, but remains at the higher pressure. If you then expand it back to its original pressure, then the temperature now falls to significantly below ambient, and it's passed through another store, leaving the cold behind in that store. If the heat exchange takes place efficiently and slowly, it can be highly reversible. If the compression and expansion take place in very, very well designed insulated spaces at high speed, that can also be highly reversible. So what we do is string four highly reversible processes together so we can now run it backwards as an engine, allowing the heat to run back through the machine, releasing a mechanical power to drive a generator to get the electricity back again.
Chris - What sort of efficiency can you manage?
Jonathan - Okay. Round-trip efficiencies, based on our earliest testing, we estimated with fairly cautious assumptions that we could achieve about 72 per cent. With more realistic assumptions, we're in the range of about 75-80 per cent.
Chris - And in terms of space, how would this compare with the example you gave earlier which is pumping water from a low-lying lake to higher-lying lake so that you can then recover that energy by running the water back down to turbines later? How much energy can they make and how much space do they take up compared with you?
Jonathan - They are typically fairly sizeable plants because if you've got a suitable mountain range or a range of hills and an appropriate valley to use, it tends to get used to the limit. So, they tend to be quite large capacity plants. Bath County in Virginia in the USA for example has a 30-gigawatt storage capacity. If we did our equipments with the same 30-gigawatt capacity, it would consume approximately 1/300th of the land area. Another way of looking at it, we scoped out a prototype utility scale machine of 2 megawatts power capacity and 16 megawatts hours storage capability. That consumes a footprint of about 8 metres x 16 metres x 7 metres high.
Chris - So very, very small and efficient. You've got the prototypes running, but when can we see this plugging into the grid, and giving us a surge capacity and long term storage that we need for the future?
Jonathan - We are initiating the design of the utility storage demonstrated prototype which is going to take around about 2 to 2 ½ years.
52:43 - Could you dangle a tether down from space or dig deep into the Earth and generate electricity from that?
Could you dangle a tether down from space or dig deep into the Earth and generate electricity from that?
Chris - Well let me do the first bit first and then Jonathan maybe can talk about the temperature bit because that's more his bag. You could dangle a wire from space if you had a satellite on a very long cable. You would have a wire which was passing, if the satellite is orbiting, through a changing magnetic field and if you do that, it will induce a current in the cable, and therefore, you'll separate charges in the cable and you'll have a plus end and a minus end, that's true. But how do you get the energy out? Because you have then got to pass another wire from the plus end to the minus end to get a circuit which means you have another wire passing through exactly the same magnetic field, and it's going to get exactly the same charge separation, so there'll be no net gain. Nice idea, probably very difficult in practice. Jonathan, what do you think about the geothermal part of the question?
Jonathan - Of course, geothermal energy is very, very widely used, particularly in countries which are geothermally active like New Zealand. I think the question though is referring to digging very deep indeed into the Earth's core. This would be incredibly expensive. Deep drilling, going down maybe 1,000 feet is achievable but it's not cheap, and not particularly easy to steer. So, geothermal tends to be restricted to areas where suitable geothermal conditions occur, where heat comes close to surface and can be tapped.
Is it safe to beam power down from orbit?
Chris - I looked up which company that was. It's Solaren Space who are a Californian based company. Sounds intriguing. They've got permission to develop this system. They want to have a satellite array out in space at about 22,000 miles out and this would have very big photo electric cells that would harness solar energy turn that into electricity which they then convert into a microwave beam. They then beam that microwave energy down to the Earth to a very big collecting dish. Their argument is that the collecting dish would be about a 2 square mile across array, so very, very big. So the energy density of the microwave beam coming in from space would be quite low. Actually, they say if an aeroplane were to fly into that, actually the amount of heating effect the aeroplane would feel from the microwaves would be less than the heating effect of an airplane just coming out from under a cloud, and being hit by sunlight. So they say that this is not a threat to birds, planes, cars, people, or anything. And the idea there is they then sum all of their energy collected by the dish back together and this could generate - as I say, energy at the rate of 200 megawatts which is not small, but it's also not huge either but this is just early days. The Japanese aerospace exploration industry said they're also planning something similar.
Diana - Well it's a shame. It could at least guarantee that your in-flight meal would be warm...
Chris - I don't think we can quite stretch to that!
55:51 - Would a sea water enema help hydration?
Would a sea water enema help hydration?
We put this to Miles Parks, Gastroenterologist, and Ari Ercole, Intensivist, both from Addenbrookes Hospital... Miles - Using the rectum as a means of administering fluid replacement in dehydrated individuals is an interesting idea. The colon or large bowel functions primarily to absorb fluid, normally doing so of course as material enters to the cecum from the small intestine, the material which has not been digested, fibrous products and so on, together with a substantial amount of fluid and solute enters into the colon, and the fluid is then sucked out as the material goes around the 4 feet or so of the colon to form up the stool. And so, you can see the colon is well designed for absorbing liquid but it really needs to do so in the context also of transport of solute, that's to say of sodium and chloride ions, and so on. It's the absorption of these, of the solute itself which then creates the osmotic gradient which sucks fluid across the lining of the bowel, and into the bloodstream. So, bearing these things in mind, I do think that water enemas on their own or water on its own is perhaps unlikely to be absorbed in a clinically significant quantities, and of course, it's just likely to come out of the rectum again whereas, I think administering saline or something of that type would potentially lead to quite a significant absorption of fluid.
Diana - Water on its own probably wouldn't do very much, but a saline solution could give one a better chance of a drink. But what if you're stuck for saline drips and all you've got is a much saltier seawater?
Ari - Unfortunately, giving yourself a seawater enema for hydration if you've had the misfortune to be stranded at sea is a complete thermodynamic nonstarter. The problem is that the salt in seawater is much more concentrated than the concentration of all the various solutes found in body tissues. Since, to a first approximation at least, the gut can be thought of as a sort of semipermeable membrane, this will lead to water molecules tending to move from the body through the gut wall, and into the seawater to reduce the concentration difference. This process where water moves along its own concentration gradient across a semipermeable membrane is called osmosis, and it's very important in biology. In this case it will actually result in you becoming increasingly dehydrated. The situation is reversed with freshwater which would be successfully absorbed. Having said that, neither procedure would be very safe especially if the water was dirty. So, giving yourself a seawater enema if you're trapped at sea is likely to make you lose water. Of course, giving yourself a seawater enema if you're trapped at a cocktail party is likely to make you lose friends as well.
Is it less windy behind wind farms?
Chris - The answer is yes because the wind farm has extracted energy from the prevailing wind in order to turn it into electricity. So by definition, it must've taken some momentum out of the air and therefore, it's less windy.