Reclaiming Wasted Watts - Thermoelectric Generators

Over two-thirds of the energy in the fuel you put into your car is wasted, most of it in the form of heat that exits along the exhaust pipe. The same is true of large-scale power...
12 February 2012
Presented by Chris Smith, Kat Arney


Over two-thirds of the energy in the fuel you put into your car is wasted, most of it in the form of heat that exits along the exhaust pipe. The same is true of large-scale power stations, which are only 50% efficient at best. But now researchers are bringing 200 year old physics to bear against the problem by developing thermoelectric generators (TEGs) that can turn waste heat into useful electricity and this week we find out how. Plus, news that disguising cancer cells as Salmonella could hold the key to producing effective anti-cancer vaccines, why the Y chromosome boosts heart attack risk, and a new drug that can knock Alzheimer's on the head...

In this episode

Peltier element (1 V, 1 A) cooling one side, heating the other one

01:20 - Thermo-Electric Generators

Incredible as it sounds, over 70% of the energy released when you burn the fuel in your car gets wasted as heat. Researchers are looking for ways to scavenge back some of that wasted...

Thermo-Electric Generators
with Dr Laurie Winkless, National Physical Laboratory

Chris -   Incredible as it sounds, over 70% of the energy released when you burn the fuel in your car gets wasted.  Most of it flows out of the exhaust pipe in the form of heat that we then throw away.  With average oil prices higher than they've ever been, researchers are looking for ways to scavenge back some of that wasted energy to make some efficiency savings.  The approach they're taking is to use Thermo-Electric Generators or TEGs that could turn heat into electricity and this is something that the UK's National Physical Laboratory, NPL, at Teddington is pioneering.  One of their scientists, Laurie Winkless works on this technology.  Hello, Laurie.  Welcome to the show.

Laurie -   Hi, Chris.  Thank you.

Chris -   So how do these devices work?

Laurie -   Basically, a Thermo-Electric Generator is based on a semi-conductor material.  It's sandwiched in between two pieces of ceramic with some electrical conductive material, maybe copper, in between.  They effectively work by having a temperature gradient applied to the device and the bigger the temperature gradient, the more of a push that the charges in these materials get.  So inside the semi-conductor, you have a positive charge and negative charge.  So you have an electron which is a negative charge, and you also have something called holes which act as a positive charge.  When you apply temperature gradients to one of these devices, you give energy to the charge carriers, so both the electrons and holes inside the material, it causes an electrical flow in the device.  And when you add up several of these couples together, you get a very nice, very reliable force of electricity.

TEG - thermoelectric generator - the principleChris -   This physics sounds very cutting edge, but it isn't new, is it?

Laurie -   Not at all.  Actually, the first Thermo-Electric effects were discovered and described beautifully in the 1800s.  So we've known about the theory for a long time.  They've been used in the space industry probably since the '50s or '60s, but now down on Earth, we're starting to look into using them in a much more realistic way in the last, probably 10 to 15 years.

Chris -   So what's the difference between what the physicists of yester year, in the 1800s would've done and what we're trying to do today?

Laurie -   Well back in the 1800s, there was no information on semi-conducting materials for example.  Everything was either an insulator or a conductor.  Semi-conductors are relatively recent phenomenon.  We take them for granted.  They're in every piece of electronics in our house, but the discovery of semi-conductors and the application of those equations from the 1800s have led to a new way of producing electricity from a temperature gradient from heat.

Chris -   So those early scientists were pretty clever and they worked out there would be an effect.  They worked out this was theoretically possible and would produce very tiny voltages for them, but with the application of modern materials and modern engineering, we're in a position to produce actually meaningful voltages that could do something.

Laurie -   Yes, indeed.  They described the effect for a metal for example.  So you get a very, very tiny voltage.  In semi-conductors you get exactly that, a much more useful voltage that we can do something with.

Chris -   So how are we actually trying to do that then?

Laurie -   Well, at the National Physical Laboratory, our focus is on trying to understand the measurement around these materials.  I always say to people, describing how these devices work is like trying to measure mass without knowing what the kilogram is.  So we need to have that kind of measurement standard in place.  There are actually a huge number of applications of these devices, the space industry being probably the one that's most established where they're used as a power source for deep space missions and beyond.  The power plant industries are starting to catch up and the car industry are the ones who are most recently investing quite a lot of money in looking into using these materials and devices.

Chris -   If I really am throwing away 70% of the energy in my fuel tank, that's a lot of money.  It stands to reason then that if I take all of the hot parts of the engine and especially the exhaust, I ought to be able to get that energy back using one of these devices and turn it into an electrical flow that I could do something useful with.  How much of a saving do you think I could make were I to implement this on my car today?

Laurie -   So, there are quite advanced prototypes, by Ford and BMW for example, which have quite high wattages, but I haven't seen enough evidence to quote them to you.  5 years ago, they put one of these TEGs in, actually based an entire TEG system around the exhaust, so capturing all of the heat that's in the exhaust, up to 500 degrees in this particular car.  They ran the car along the motorway, and they produced about 500 watts of power which equates to about 5% saving in fuel.

Chris -   Which could save quite a lot of money, couldn't it, in the long run?

Laurie -   In the long run, it's worth looking into at least.  The devices themselves aren't amazingly efficient yet.  We have a lot more work to do to make them incredibly efficient.  But already, you can see a saving and you can see the improvement and the efficiency of the system of the car.

Exhaust fumesChris -   These things would flank the exhaust pipe or whatever heat source there was.  So that's the hot side.  You're giving the particles, these electrons and the holes, energy on the hot side.  How do you then get them to move towards that cold side?  How do you make the cold side to create the current flow?

Laurie -   The dream would be that you just use the airflow of car moving down the motorway for example.  But the reality is that it's not a very reliable cold source.  So what the car industry particularly is trying to use is the cooling system that already exists in the car.  So it's generally something like ethylene glycol and they just reroute the cooling system to wrap around the TEGs and that produces the cold side.

Chris -   And what sorts of materials, because you said semi-conductors quite generically but what sort of semi-conductors?  What are the materials that we're using that had bearing fruit in this regard?

Laurie -   At what would consider as lower temperature levels, so around 200 degrees Celsius, you have the quite exotic sanding, bismuth telluride.  This is a semi-conductor device which, at that temperature, has a thermo-electric efficiency of maybe 5% or 7% - not a huge efficiency.  But as the temperature variation increases, so as you have much hotter side versus a cold side, when you have maybe up to 500 degrees plus, you have to start looking at different materials because bismuth telluride is not great with those temperatures.  You start to look at things like silicon, germanium based.  So, materials we're actually quite familiar with already as they use in the electronics industry.

Chris -   And critically, what about the cost of those materials?  Are they readily available and fairly cheap or are we looking at a major price hike to save 5 pence on each refuel?

Laurie -   Well bismuth telluride ones are actually extremely cheap, surprisingly cheap!  You can get bismuth telluride TEGs which will produce about 100 watts for about 90 pounds.  So about a pound of watt is generally quoted the higher...

Chris -   Cheaper than a catalytic converter, isn't it, which is ridiculously expensive.

Laurie -   Yeah, indeed.  But when you get to the higher temperatures, the materials get a little bit more exotic, so the price will increase accordingly.

Chris -   Now help me out with one frustration;  if you have something that conducts electricity very well, it conducts heat very well.  The electrons are jiggling around, and they then move through the material, making other things jiggle around, that's how heat transfers.  So how do you get this efficiency where you have something which will let the electricity flow, the electrons, but keep the heat back?  It sounds like a paradox.

Laurie -   Yeah, it is indeed a paradox and it's actually a measurement issue too.  If we want to know exactly how much electricity can flow through these materials, we need to know its electrical conductivity and we need to know it very accurately.  We also need to know its thermo-conductivity - how happy it is to allow heat to flow through.  So to measure one and not the other is actually extremely difficult.  They're coupled together quite strongly.  But one of the efforts on a research level, is to look at nanostructuring the material.  Changing the shape of the material on the nanoscale to increase the number of barriers or interfaces that the heat and the electrons have to flow through.  Electrons are pretty happy to bump their way through interfaces.  Heat takes a bit more of a beating, so it slows down the heat flow through the material.

Chris -   So you can't make a material which will allow electrons through but will frustrate the progression of heat through the material and therefore you can maintain a hot side and a cold side, and drive that current.

Laurie -   You can to a degree, of course we are subject to laws of thermodynamics like everything else unfortunately.  The idea is that you keep the temperature gradient for as long as you possibly can.  You will always get hot and cold giving you warm at some point and you start to lose the power output at that point.  But you can then cool the whole TEG down and restart the flow.

Chris -   Love the pun on "to a degree" too, Laurie.  Laurie Winkless from the National Physical Laboratory.

Big Bend Power Station

09:49 - How Heat Pumps Push Power Plant Efficiency

Traditional power stations are very inefficient, losing lots of energy to the environment. But Thermo-Electric heat pumps could now help to claim back some of that wasted heat, and make a...

How Heat Pumps Push Power Plant Efficiency
with Professor Andrew Knox, University of Glasgow

Kat - We've heard how a Thermo-Electric Generators or TEGs could be a useful way to turn waste heat energy back into useful electricity in small scale settings like cars or things like that, but there are also settings on a very big scale, for example a power station which throws away huge amounts of heat up its cooling tower.  So, could Thermo-Electric technology help here?  Now we're going to talk about it with Andrew Knox.  He's Professor of Power Electronics Renewable and Sustainable Energy at Glasgow University and he's looking at feasibility of using this kind of technology, but more or less in reverse.  So good evening, Andrew.

Andrew -   Good evening, Kat.

Kat -   So tell me a little bit about for a start, the kind of scale of heat loss we're talking about in a power station and why it would be attractive to try and use thermo-electric technology?

Andrew -   Much of the UK's power generation comes from what's called thermal power stations and that's where we burn fossil fuels; gas, coal, et cetera.  The generation of electricity from that process is subject to various thermo-dynamic restrictions.  It's the same basic problem that the thermoelectrics have got where you've got a hot and a cold side, and the maximum efficiency is a function of those as determined by the Carnot cycle.

In a conventional thermal power station, typically what happens as you burn the fuel, let's say coal for example, and that raises steam in a boiler.  That steam is then rooted through a turbine and the force of the steam going through the turbine turns an electrical alternator which is what generates electricity.  The steam goes through a series of different turbines, each at progressively lower pressures and at the end of that process, when you've extracted about as much of the useful work as you can out of the steam, what you have to do is recondense the steam back into water and that water is then returned to the boiler to be used again.

The water that's used as the working fluid for this power generation process is exceptionally pure and the reason for that is that any impurities that would be in normal tap water for example, would convert your turbines into Swiss cheese very quickly.  I mean, it would really attack the turbine blades.

So this process that's going on - boiling water, driving it through a turbine and then condensing it back to water, and reboiling it back in the boiler - that process is called the Rankine cycle and it's subject to limitations.

If you drive past a large thermal power station, let's take for example Ferry Bridge down the M1.  When it's working, you will see large quantities of steam being rejected from the cpower stationooling towers and the cooling towers are these big huge concrete structures.  That's basically dropping the energy out of the steam and back to the environment, so that's wasted heat.  And on the best modern thermal power stations, their efficiency is about 46 or 47%, so more than half of the energy that's used is being rejected to the environment.

Kat -   So in a power station we have a lot of things that are very hot and things that you're trying to cool down, so there does seem to be capacity to use thermo-electric technology, but you're proposing a slightly different way, not using the difference between heat and cold to generate electricity but something else.  How do you think we could introduce thermo-electric technology into a power station to make it more efficient.

Andrew -   One of the things that Laurie touched on is the semi-conductor Thermo-Electric Generators.  One of the properties of these Thermo-Electric Generators is that as Laurie described it, if you apply a temperature difference then you will generate a voltage from them, but if you apply a voltage to the same material, the same device, you can actually use it to shift heat from one side to the other.  In the context of the power station, in the condenser of the power station, where the used steam is converted back into water, as that steam gives up its energy and condenses away from the heat of evaporation, by using some thermoelectrics, we can actually capture some of that energy and re-inject it back into the power plant rather than rejecting it to the atmosphere.

Kat -   So you're talking about actually taking the heat and putting the heat back into the system to generate a bit more electricity again.

Andrew -   Yes.  It's very low grade heat but it's conceptually thought about as the energy released as the steam gets converted back into water.

Kat -   So this would mean you get more bang for your buck.  So for the amount of coal that you're burning, you would end up getting more electricity out the other end.

Andrew -   Correct.  You would end up having to burn less coal for a given amount of electrical output from your generators.

Kat -   So this sounds brilliant, but how realistic is it?  What are some of the challenges that are there to try and implement this kind of technology?

Andrew -   There are two big challenges - the first one is the engineering of the condenser itself.  In other words, you need to get tens of thousands of these semi-conductor devices, properly arranged in the steam flow to maximize the heat transfer and the second thing is to optimise the electronics that would be used to drive this process.  The Peltier effect as it's called, which is the property of the semi-conductor material when it's in use like this, that has a co-efficient of performance.  That is determined by the difference in temperature between the hot and the cold side.  In general, as the temperature difference increases, the coefficient of performance decreases.  So this is not something you can use up to a temperature you like.  This is really to be used only at the low temperature and for a typical large scale power plant, the steam coming out of the last stage of the turbine is about 30-35 degrees C.

Kat -   So, do you think the kind of technologies you're talking about could actually be fitted into the power stations we have now or will it take a new breed of power station?

Andrew -   I think it's suitable for both new build and for retro fit.  The efficiency using today's devices with today's materials means that we are just about at the breakeven point.  There's two contributing factors which help us here, one is the power station efficiency itself as we go through supercritical, very high temperature, very high pressure steam, that helps us.  Also, as the materials in the semi-conductor devices improve, that also helps the overall efficiency of the heat pumping and therefore, the coefficient of performance of the heat pump.

Kat -   I know this is kind of "how long is a piece of string" question but if all the research goes well, when do you think this kind of technology might be able to be brought in?

Andrew -   I would think you're probably looking at 10 years.  To do a large scale power station or like Ferry bridge or Drax, that would be ambitious to say the least.  But if you were to go for a relatively modest, 1 megawatt or 5-megawatt power station and I would expect to see in 10 year's time, that would be available, with a modified Rankine cycle.

Kat - And using the benefits that could be gained in efficiency in saving money on coal would actually make it worth investing in this kind of technology.

Andrew - Yes, I do. Even if you're only talking about a couple of percent efficiency, increase in the overall coal to electricity conversion, that couple of percent represents a huge amount of power if you take all of the lifetime of the power station of maybe 25 years, coupled to the fact that energy prices are going to continue to increase in my view.

Kat - So that's definitely something worth investigating and investing in.  Thank you very much, Andrew.  That's Professor Andrew Knox from Glasgow University.

17:51 - Y Chromosome yields heart disease clues

Although deaths from heart disease are falling, it's still a major killer. And men are more likely to suffer coronary heart disease than women of the same age. Now, research published...

Y Chromosome yields heart disease clues

Although deaths from heart disease are falling, it's still a major killer. And men are more likely to suffer coronary heart disease than women of the same age. This has often been put down to chaps having unhealthier lifestyles, but an international team by scientists in Leicester has just published a paper in the Lancet showing that there may actually be a genetic component at work.

Although men and women share almost all the same genes, there's one important difference. Women have two X chromosomes, while men have an X and a Y.  There are only a handful of genes on the Y chromosome, making a grand total of around 27 proteins, and most of these are thought to be important for sexual development and making men manly.

X & Y ChromosomesBut in recent years, there have been some intriguing links made between this tiny genetic estate and diseases including HIV and autism. So the scientists decided to analyse the genetic makeup of the Y chromosome in more than 3000 British men involved in three different heart disease studies.

Because Y chromosomes are passed down almost whole from fathers to sons, with little genetic muddling from generation to generation, there are only a limited number of different 'flavours', or haplogroups of Y chromosomes. Because of this, the Y chromosome is often left out of most large-scale genetic studies looking for links between gene variations and diseases.

In this case, the researchers found that all the men fell into just 9 haplogroups, and 90 per cent of the Y chromosomes came from only two different haplogroups. And when they looked at their history of heart disease, they found that men with Y chromosomes from one particular haplogroup had a 50 per cent increased risk of developing coronary heart disease than men whose Y chromosome came from the other haplogroups.

After a bit more digging, the researchers confirmed that this association wasn't linked to other risk factors for heart disease, such as lifestyle factors like drinking and smoking or other known biological risk factors.  And when they looked closer at the activity patterns of genes in men from different haplogroups, they found clear differences between those from the high risk group and the other groups in the activity levels of certain genes involved in inflammation and autoimmune responses, both of which are thought to play an important role in heart disease.

At the moment this is still just an association - although it's the first study to robustly uncover an association between heart disease and the Y chromosome -  and a lot more work needs to be done to confirm this finding and figure out exactly how the genes on the Y chromosome are having these effects. But in the future it might help to lead to new ways to reduce the risk of heart disease in men, or even potentially treat the disease. And because the Y chromosome is passed down wholesale from father to son, it also tells us that in some cases, susceptibility to heart disease may be handed down the generations in this way.

Cross section of a human liver, taken at autopsy examination, showing multiple large pale tumour deposits. The tumour is an adenocarcinoma derived from a primary lesion in the body of the pancreas.

21:30 - Feed a cold, starve a cancer

A self-inflicted fast might double the effectiveness of anticancer treatments, new research has shown...

Feed a cold, starve a cancer

A self-inflicted fast might double the effectiveness of anticancer treatments, new research has shown.

Writing in the journal Science Translational Medicine, University of Southern California scientist Valter Longo and his colleagues have shown both using cells cultured in the dish and also in experimental mice that fasting sensitises cancers to chemotherapy drugs.

Secondary tumor deposits in the liver from a primary cancer of the pancreasInitially using yeast cells genetically programmed to carry a genetic mutation that causes cancer in humans, the team found that starving the cells by replacing their culture media for 48 hours with water devoid of any nutrients triggered severe stress and increased the rate of cell death.  Cells lacking the cancer-causing gene and subjected to the same treatment, however, were paradoxically much more resistant to the insult and were less sensitive to toxic chemicals like hydrogen peroxide.  The researchers then grew cancer cells in growth medium made from the blood plasma of mice that were either fasting or fed normally.

As expected, cells grown in the fasting mouse medium showed greater signs of stress, higher rates of death and were more susceptible to anti-cancer drugs than their normally-nourished counterparts.  To find out whether this effect would translate from the dish to a real case of cancer, the researchers then treated mice carrying a range of tumour types including melanomas, gliomas (brain tumours) and breast cancers.

Mice that were fasted before receiving chemotherapy, they found, had a 40% reduction in the rates of cancer spread and a 42% long-term survival rate compared with 100% mortality in the normally-fed animals.

The mechanism underlying this extraordinary observation, the team believe, is that the very same processes that make cancer cells grow uncontrollably also prevent the cells from shutting down their activity and protecting themselves in the face of stress, including stress induced by fasting.  And in this state the cells become much more vulnerable to chemotherapy drugs compared with healthy tissue. This, the researchers suggest, could be a way to boost anti-cancer effects in humans while simultaneously minimising side effects.

False colour SEM of Salmonella bacteria

23:47 - Disguising Cancer as Salmonella

Can we trick the immune system into attacking cancer cells by disguising them as bacteria? New research suggests that adding a bacterial flagellum gets results...

Disguising Cancer as Salmonella
with Professor Julie Magarian Blander, Mount Sinai Hospital

Chris -   Making cancer cells resemble the Salmonella bacterium might sound like an odd thing to, but oddly enough, it could hold the key to creating anti-cancer vaccines which trigger the immune system to actually attack cancers.  And to explain how, we're joined by Professor Julie Magarian Blander from the Mt. Sinai School of Medicine in New York.  Hello, Julie.

Julie -   Hello.

Chris -   So first of all, why doesn't the immune system attack cancer in the first place?

Julie -   The immune system recognises its own tissues by a process called pattern recognition.  So when it's searching for microbes, it's really searching for patterns that are associated with microorganisms and these patterns are absent from normal healthy tissues.  Therefore, because tumour cells and cancerous cells are derived from normal cells, they don't have those microbial patterns that the immune system likes to see and target.

Salmonella bacteriaChris -   So that's why they escape normal surveillance.  So what were you doing with Salmonella?

Julie -   With Salmonella there is this protein called flagellin which Salmonella and other bacteria actually use for locomotion and therefore, we took this protein - the sequence of this protein - it's easy to express in cells because it's a protein in nature.  We expressed it in tumour cells in order to make them look more microbial to the immune system.  By doing so, we could target the receptors that recognise these patterns or structures that are associated specifically with microbes.  In this way, you are tricking the immune system to think that tumour cells actually have a component that's derived from microbes and then they're targeted this way.

Chris -   So the cells are made to look more like a bacterium.  This gets the interest of the immune system via these special receptors it has to pick up pathogens.  The immune system then attacks the tumour cells.  That's all very well for the tumour cells that you have added the Salmonella-like gene to it, but what about the tumours elsewhere around the body?

Julie -   So, in animal models, in mice, the strategy is to take the tumour cell itself, introduce this flagellin protein in order to target the receptors of the immune system and then irradiate the tumour cell and use that as a whole cell cancer vaccine.  We have done two different sets of experiments where animals that do not have tumours have been vaccinated and then we tested their protection against subsequent challenge from a wild-type tumour that does not express the flagellin.  We've also done experiments where animals that bear tumour already were vaccinated and then we monitored the immune response.  In both cases, we were able to see that the immune system efficiently mounts a robust immune response - both the CD8 cytotoxic T-cell response and a helper response system important for making those CD8 T cells aggressive and capable of attacking the tumour cells.

Chris -   So the immune system, once it's been primed using the Salmonella resembling vaccine cells, which are actually killed and don't go anywhere else once you put them in, the system then begins to attack the rest of the tumour.  Presumably, there's some kind of crossover then.  The immune system learns to recognise the cancer cells, having had its interest peaked by the presence of the Salmonella flagellin gene.

Julie -   Yes, exactly.  What we were able to show is that we can boost the memory response.  The whole basis for vaccination for infectious diseases is, for example, you vaccinate with a particular component of a microbe and then the individual that's been vaccinated is protected, sometimes throughout their lifetime, against the infection itself.  Here, it's the same idea.   Because the microorganism has been seen the flagellin from the microbial components from Salmonella within tumour cells, the immune system can then make a response to that tumour and then subsequently that memory response is what protects against further development or growth of the tumour.

Chris -   And there's no danger that the immune system might be led to start attacking healthy tissue because it gets interested in the cells and reacts to the wrong thing on them and then starts attacking healthy tissue.

Julie -   Yes.  This has been a caveat for whole cell cancer vaccines and many investigators do not prefer that, but there are also powerful mechanisms of tolerance that are inherent to the immune system.  We have not addressed this in our study, but those mechanisms are so powerful that we think that we might be favouring the presentation of specific cancer derived molecules and those are the ones that are preferentially going to be targeted.  So, cancer cells can share normal proteins with healthy cells, but they also have their own set of proteins that they express and there's a lot of efforts in identifying what those proteins are.  Our hope is that by introducing flagellin, we can bypass the process of systematically identifying the individual proteins that cancer cells might have unique to them and not expressed on normal cells.  In this way, we could, without knowing what those specific proteins are, we could prime the immune system to a whole slew of things that are going to be new to the immune system.  And therefore, those normal proteins may not be targeted but it is something that we need to test in animals.

Chris -   And just to finish off, talking of animals, the mice that you tested in your study, how did they do?  What sort of improvement or clinical outcome did you get with those animals that were treated with this vaccine?

Julie -   We had several models where we had transplantable lymphoma cells and also melanoma cells that are metastatic.  With the melanoma cells, it was really dramatic.  These melanoma cells are injected intravenously into mice and they metastasise to the lung.  Those mice that were vaccinated with the flagellin containing melanoma whole cell vaccine did not have any metastasis.  Their lungs were completely free of metastasis compared to the control animals that were not vaccinated.  And similarly, the subcutaneous growth of those tumours, lymphoma cells that we have transplanted subcutaneously into the immunised mice, all the mice rejected the tumour and were capable of mounting a robust memory response to that tumour compared to the wild type unimmunised controls.

Chris -   Super!  We'll leave it there but thank you for bringing this up to speed.  That's Julie Magarian Blander from the Mt. Sinai School of Medicine in New York.

Cartoon of nerve cells (neurones) affected by Alzheimer's Disease with beta-amyloid plaques and neurofibrillary tangles

30:36 - Drug knocks Alzheimer's on the head

A drug licensed for lymphoma and used to treat several forms of cancer may also be an effective anti-Alzheimer's agent, new research has revealed...

Drug knocks Alzheimer's on the head

A drug licensed for lymphoma and used to treat several forms of cancer may also be an effective anti-Alzheimer's agent, new research has revealed...

Bexarotene, marketed as Targretin, is licensed for the treatment of a disease called cutaneous T cell lymphoma, although it has also been used subsequently to suppress the growth of a number of other cancers including breast and lung malignancies.  But owing to the way the agent works, by activating a signalling molecule called a retinoid X receptor (RXR), which is present on DNA and controls gene expression, animal experiments have now demonstrated that it can also dissolve the amyloid plaques that cause Alzheimer's and reverse some of the cognitive deficits associated with the disease.

Writing in Science, Case Western Reserve University researcher Gary Landreth and his team administered the agent to mice genetically programmed to develop the rodent equivalent of Alzheimer's.  Treated juvenile animals showed a near immediate 25% drop in the levels of dissolved beta-amyloid proteins in the fluid bathing their brain cells.  After 14 days of therapy, the number of amyloid deposits was down by 75% compared with controls.  In older animals a 50% reduction in plaque number was achieved.

These structural changes were mirrored by functional improvements too, with treated mice recovering memory and cognitive abilities including being able to recall fearful stimuli, find their way around better and respond appropriately to smells.

The team think that bexarotene works by increasing the level of a substance called ApoE in the brain.  This can dismantle the amyloid aggregates that are the neurological hallmark of the disease.  Previous experiments in human subjects have shown that reducing the burden of these deposits can reduce the disease symptoms, suggesting that the agent might be able to achieve similar impacts in human subjects.

33:00 - Olympic Effort to get Children into Biology

A new project launched in London this week ahead of the 2012 Olympics to get school children across the country thinking about their bodies and how they work (if they needed any help with...

Olympic Effort to get Children into Biology
with Sir Steve Redgrave, British Rowing Team, Prof Mark Walport, The Wellcome Trust

A new project launched in London this week ahead of the 2012 Olympics to get school children across the country thinking about their bodies and how they work (if they needed any help with that) using sports exercise and a range of scientific experiments. Meera Senthilingam went along to the launch.

Meera -   The pupils of St. Paul's Trust School in East London were treated this week to a range of experimental kits, helping them to explore their inner workings of their bodies during exercise.  The kits will be delivered to schools across the UK as part of an initiative inspired by the 2012 Olympics and brought in by the Wellcome Trust to help pupils get active and in the zone as Mark Walport, Director of the Wellcome Trust, explains.

Mark -   The Wellcome Trust has launched a series of kits for schools called In the Zone, teaching the next generation about their bodies and fitness which is designed for all stages of school, so it'll go out to more than 23,000 primary schools, to more than 6,000 secondary schools.  And each of the boxes contains a series of experiments.

Wellcome TrustMeera -   So it's really focusing in on physiological traits that would benefit people perhaps during exercise.

Mark -   Yes, that's part of it and it's also partly about teaching people how their body responds to exercise.  So, if you think about the brain,  reaction time is important, so there is an experiment that can measure reaction time.  Your muscles are obviously hugely important in exercise and so, for primary children, there are simple experiments like, can you jump further if you have longer limbs?  For secondary schools, we've got experiments that teach people about lung capacity.  Obviously, if you have big lungs you're much fitter, potentially.  Your heart rate is a very good measure of your fitness and how your heart rate changes in exercise and so, we've got pulse oximeters.  It's a whole series of experiments which are, on the one hand, linked to the curriculum so they're relevant to science.  On the other hand, they're specifically about health and exercising.

Meera -   Have you had a go, Mark, on the equipment yourself?

Mark -   Yes, I've had a go on some of it but I'm not sure I'd like to tell you the results!

Meera -   Wellcome Trust Director, Mark Walport.  Although Mark wasn't keen to share his results, many students were, as they publicly performed some of the experiments out on display, including one measuring lung capacity...

Cusomo -   Hi.  I'm Cusomo Baker.  I'm 13 and I'm in year nine.

Meera -   So Cusomo, you've got one of the experiments from the kits here which is a long plastic bag with lots of numbers down it...

Cusomo -   Basically, it's got litres on the bag.  You have to blow in it and that will show you how much you can breathe into it from your lungs.

Meera -   So this looks at your lung capacity.

Cusomo -   Yes, lung capacity.  It's to do with your height, whether if you're longer, you will blow higher or if you're shorter, you will blow lower.  So that depends on that.

Meera -   Okay, so how tall are you?Olympic Rings

Cusomo -   I'm 5 foot 3.

Meera -   Okay, let's see how much air you can let out.

Cusomo -   Okay, I'll try it then.

Meera - breathed out a litre and a half!

Cusomo -   Yeah.

Meera -   One man able to fill the entire 6 litres of the bag and more was 5-time Olympic gold medallist Steve Redgrave, though he is 6 foot 4, and the kits help you learn that height can greatly benefit this particular physiological attribute.

Steve -   Hi.  I'm Steve Redgrave and here with the Wellcome Trust today, having a lot of fun doing some experiments.

Meera -   What would you say are the main physiological traits that people need to succeed at rowing?

Steve -   The physical side is the length of levers.  You don't really get very small people competing at the highest level.  You can get short people to a reasonable level, but when it actually comes down to athlete size, they're all very tall.  It's all about long levers in some ways.

Meera -   Being tall is good.  You've got those levers to get you through the water quite quickly, but what about your internal organs & phisiology?

Steve -   Rowing is an endurance based sport.  So you've got the physical side, you've got the right specimens leverage wise.  They also have got to be trained to be be very efficient.  If you don't have the lung capacity, the VO2 uptake transferring oxygen into energy that goes into red blood cells to feed the muscles, from that point of view, you're not going to be very efficient.  So the science behind it becomes immense - training, preparation, monitoring, trying to improve levels all the time.

When I started back in the '70s, there was none of this.  I remember one of the chief coaches wanting to do a muscle biopsy on me.  I'd worked for a number of years building up my muscle and they wanted to stick a little needle in and pull a bit out just to find out if I was more fast twitch or slow twitch fibres!  Endurance sport tends to need slower twitch, faster speed tends to be more fast twitch.  I was a reasonable sprinter so I must have a reasonable amount of fast twitch fibres within my makeup but endurance wise, you can train it.  So having that ability of natural speed and then trained for endurance, so the best of both worlds in some ways.

Meera -   Did you learn a lot about how your body actually works through all this training and through the scientific methodology and did that help you then to get better?

Steve -  I think it does.  In sport, everyone seems to get faster all the time.  They may not get faster every time they go out or within a year or even an Olympiad, the 4-year cycle.  But over a period of time, times get quicker, athletes go quicker.  You've got to use every aspect so diet, training, the science behind it - it all plays a part to being a better and faster athlete than we were before.

River Wandle, Strathville Rd, SW18. From a road bridge, with some new flats built over the river.

38:54 - Revitalising Urban Rivers - Planet Earth Online

Rivers in cities and towns have had a rough time over the years – often diverted, hidden or lined with concrete. Some even end up as sewers! But now, around the world, urban rivers are...

Revitalising Urban Rivers - Planet Earth Online
with Bella Davies, Wandle Trust and Angela Gurnell, Queen Mary University of London

Rivers in cities and towns have had a rough time over the years - often diverted, hidden or lined with concrete.  Some even end up as sewers!

But now, around the world, urban rivers are undergoing a revival, many becoming havens for wildlife.  Planet Earth Podcast presenter, Richard Hollingham, has been to visit a project in South London where conservation science is helping to turn a long-neglected river into an urban asset...

Richard H. -   I'm in Carshalton near Croydon in south west London.  200 years ago, this was a rural village, now it's part of the vast suburbs encircling London.  The river at its centre, the Wandle, once flowed through fields of crops, now it's surrounded by roads, railways, houses and businesses.  And rivers in places like this often end up neglected, polluted and unloved.

Bella -   A couple of hundred years ago, this area was much more rural.

River Wandle, Strathville Rd, SW18Richard H. -   Bella Davies from the Wandle Trust.

Bella -   And the river had already been impounded by lots of mills.  It's actually known as one of the hardest worked rivers in the world for its size.  Moving forward from then, we had the industrial revolution and an awful lot of pollution went in, there was general disregard for rivers across the country.  By the 1960s, it was an open sewer and, more or less, biologically dead.  Through the '70s, it got very canalised and made very straight to help with flood defence issues.  Rolling forward to now, we're trying to restore many of the natural processes and natural habitats that would have been there.

Richard -   The Trust has used the expertise of Angela Gurnell from Queen Mary University of London.  Her research has found that even rivers lined by concrete, covered with bridges or interrupted by weirs are still worth saving.

Angela -   The surprising finding we had was that actually certain types of engineering are compatible with quite a varied and aesthetically pleasing river, and if the water quality is good, quite strong ecological functioning of these rivers.

Richard H. -   So really, all is not lost even if it is surrounded by concrete and in an urban area.

Angela -   Increasingly there's opportunities in situations like this where we're standing where the rivers can be bound on one side by a road, on the other side by housing and above us by a railway bridge.  You can still do quite a lot to improve that section by just gently pushing away at the engineering and removing the bits that you actually don't need and allowing the river to recover in a patchy way.

Bella -   And what we did The Louisiana Wetlandswas to knock out part of the weir and to channel the water through that, so the same volume of water is going through a smaller space, so it's going much faster as it would more naturally.  We've introduced about 60 tonnes of gravel through this area and we've sculpted that so it has a range of different habitats and within that different morphologies to it.  We've narrowed the river upstream and put in place new banks and taken out some of the silt that was held behind the weir.  Over the top we've put in over a thousand native plants.

Richard H. -   And that has meant the Wandle not only looks much more natural, but it's seen the return of fish and the birds that feed on them like the kingfisher. 

But further upstream, the rivers disappeared completely.  In a park near the centre of Croydon, I met up with Tom Sweeney from Croydon Council.

Tom -   In 1967 the council culverted the river; it was buried underground.  But in a few weeks time, we will have the signs of the River Wandle re-emerging in the park.

Richard H. -   So where is it?

Tom -   We're standing on top of it at the moment!

Richard H. -   We're on a slightly muddy area of the field here.

Tom -   We have some red lines over here which denote where we're going to put the new headwall structure for the river and it then stretches back towards the centre of Croydon, through the middle of that open field there, to the other end of the park.

Richard H. -   So you're essentially turning a pipe back into a river?

Tom -   Yes.

Richard H. -   And as we watched, the digger began scraping away at the earth to reveal the top of the culvert and the long forgotten waterway.  Angela Gurnell...

Angela -   By opening up these culverted sections, we connect the sections of river back together again and that's fantastic from an ecological point of view because it allows the species to move up and down the system.

Richard H. -   Waterways in towns and cities may never return to their former glory, free to meander through the landscape, untouched by civilisation but a few changes backed by scientific expertise are transforming them back into corridors for wildlife.

An artist's concept portrays a NASA Mars Exploration Rover on the surface of Mars. Two rovers have been built for 2003 launches and January 2004 arrival at two sites on Mars. Each rover has the mobility and toolkit to function as a robotic geologist.

44:10 - Powering Spacecraft with TEGs

Powering space craft is a challenge. Traditional chemical batteries go flat and for deeper space explorations where the Sun don't shine, solar power is out of the question. Instead,...

Powering Spacecraft with TEGs
with Dr Richard Ambrosi, Space Research Centre at the University of Leicester

Chris -   Powering space craft is a challenge.  Traditional chemical batteries go flat and for deeper space explorations where the Sun don't shine, solar power is out of the question.  Instead, the European Space Agency is working on units that rely on radioactivity to provide the heat needed to run a Thermo-Electric Generator.  Dr. Richard Ambrosi is from the Space Research Centre at the University of Leicester where he does the work that helps to power our missions to Mars.  Hello, Richard.

Richard -   Hi, Chris.

Chris -   I've made passing mention of a couple of them but what are the main problems associated with powering probes in space?

Richard -   Well, the primary problem is when you don't have access to the Sun.  So, if you want to explore the more distant cold, dark, inhospitable environments, then you need an alternative power source and nuclear power is one of those alternative power sources.  It turns out that even if you want to operate very close to the Sun, you have a problem where solar panels generate a lot of heat so they become less efficient and therefore, nuclear power can make a big difference.  Other examples include surviving the lunar night or exploring dark, cold lunar craters and certainly, if you want to operate continuously day and night on Mars, travel large distances and function for a very long period of time, you need to develop alternative power sources.

The Spirit RoverChris -   When space scientists who were working on things like the Apollo missions and those early probes were looking at those very problems, what sorts of things did they come up with as a solution?  Did they jump literally on this 200-year-old bit of physics and say, Thermo-Electric Generators is the way to go?

Richard -   Well, they did essentially that.  The use of radio isotope Thermo-Electric Generators in space goes back to the '60s.  The US has been very successful in launching a number of these systems in exploring the moon and exploring deep space.  And Russia has been very successful in using Thermo-Electric Generators to convert heat generated from reactors in space into electricity.  Russia has launched more than 30 reactors into space.

Chris -   So in essence, you have a radioactive source, a piece of plutonium or strontium, or something that radioactively decays vigorously and produces heat and that gives you the hot side of your Thermo-Electric semi-conductor like we were discussing.  I would guess that space being cold as it is, 3 degrees above absolute zero, that's quite a good cold side.

Richard -   It is but it's actually quite challenging, developing a system that provides you with the constant heat source, constant delta T, and allows you to radiate any of the unconverted heat into your environment without impinging on the overall mass of your radiator structure or your thermal management system that has to dissipate the excess heat.  So it's actually quite challenging, developing an efficient, a mass efficient system where you get a lot of power for the mass involved.

Chris -   How radioactive are these sources and how big are they?  So if I have a 1-tonne satellite or something or probe which I'm going to send off into deep space, what mass will be the generator, the Thermo-Electric Generator and how much radioactivity or radioactive material is in there?

Richard -   Well, if we look at the US systems, we're talking about 100 to 250-watt units.  The mass efficiency ranges from about 3 watts per kilogram to 7 watts per kilogram depending on the flavour.

Chris -   But isn't that quite a lot of radioactive material?

Richard -   Well it's not the radioactive material that's the bulk of the mass.  It's the whole system, so you have to take into account that the radioactive material is encapsulated in a containment system.  It's surrounded by an aeroshell to allow it to survive worse case re-entry into the atmosphere scenarios.  You then have a radiator structure in all of the thermal management system that goes with it.  If we're talking about a system for a European design that will have a mass efficiency of about 2 watts electric per kilo and we're talking about 100 watts electric then the whole system should weigh about 50 kilograms to 100 kilograms at most.

Chris -   So when you're designing the systems that you are working on to send things like probes to Mars to explore the surface of other planets and so on, what do you have to do in terms of engineering in the safety?  We've had one Russian mission that failed to leave Earth and has come back into the atmosphere fairly recently, Phobos-Grunt so, what do you have to do to make sure that the radioactivity in there isn't going to pose a threat?

Richard -   Well you have to make sure that the radioactive material is completely encased in a system that will prevent the dispersal of the material, irrespective of the re-entry situation; So whether it lands in the ocean or lands on the ground.  You have to also design in safety features that allow it to withstand launch pad explosions.  These are all requirements that feed into a launch safety framework and the US and Russia have launch safety frameworks for launching radioactive material into space and Europe will have the challenge of developing its own launch safety framework.

Chris -   You mentioned that these units are a couple of hundred watts.  That's not very much,  when you think that my computer, just the computer is 300W.  So, for running really quite high end systems, that's not very much.  Do they basically use the generator to charge up a battery or a big capacitor so you have something to give you surges of current to run energy intense bits of equipment for short times?  Is that how they work?

Richard -   Well, you can use multiple units.  So for example, in a mission requiring 600 watts if your unit generates 100 watts, you would use 6 units.  You wouldn't necessarily need to use batteries.  You could use them in combination with batteries.  But space instruments and space systems are designed to use, to minimise on the amount of power that they need to operate.

Chris -   So what are the big challenges that you are now trying to overcome because we've been working on these things for 40 or 50 years, haven't we and successfully too?  So what are the big challenges that still remain to be overcome?

Richard -   Well for Europe, the challenge is to develop its own capability in building both radioisotope Thermo-Electric Generators and radioisotope heater units.  Europe will be using an alternative isotope to what's being used in the past so the challenge will also be to be able to produce the isotope in significant quantities.

Chris -   And why do we need our own capacity?  Why can't we just go to NASA and say, "We'll borrow one of yours."?

Richard -   Well there is a general shortage of plutonium production and Europe has access to americium-241 which is in the separated plutonium in sellafield in the UK.  So it would be more cost effective for Europe to use a material that is available.

Chris -   Super!  Richard, thank you very much.  That's Richard Ambrosi.  He's from the University of Leicester. 

Could we harness energy from vertical pipes in the sea?

Laurie - With some of the really efficient generators, even a temperature gradient that small can produce power. The difficulty in this case is that you tend to want to apply the temperature gradient across a device an awful lot smaller than a pipe put into the ocean. So the difficulty is getting the gradient across the right bit of the device. But yes, even with those temperature gradients, you can get some power output.

Chris - And then you'd have the energy embodied in making and deploying a system like that. Often people don't think about that aspect of the equation. They may think "I can make a 5% saving over here" but then don't necessarily think about where the materials to make that solar cell come from, or how much it costs to buy those, and the carbon footprint of shipping them half around the world.

Laurie - I think the cost of life is a big issue. You have to produce the materials, they have to be uniform enough, they have to be of a good enough quality and then they need to be implemented. It's always a difficulty with that aspect.

Could we use our body heat to generate electricity?

Andrew - Yes, that is quite possible. Humans are 30-35 degrees C versus the ambient temperature of maybe 20-25 degrees C. A small temperature difference is sufficient to generate a small amount of power and electronics are getting more and more efficient; we are now down at microwatt level for various things. So yes, you could quite feasibly have human powered electronics using TEGs as the mechanisms for that power.

Could we generate electricity from domestic heaters?

Andrew - Domestic gas boilers, I suspect, would probably not be a particularly good use for thermoelectrics because thermoelectrics are inherently very inefficient at the moment, maybe 5%.

However, if you take something like a wood burning stove, the primary purpose of that is to produce heat in the room and if you covered the surface of the stove with thermo electric material, you could generate a certain amount of electrical energy from the heat transfer through the thermoelectrics. In other words, the primary purpose of the stove is to heat the room and the heat going through the thermoelectrics does that but you can convert a percentage of that into electricity.

What is a safe isotope for TEGs?

Richard - Traditionally, it's been plutonium-238 which has been used for powering radioisotope Thermo-Electric Generators. Thorium is not used for such systems.

Could you generate useful electricity from the flames of oil refineries?

Laurie - Possibly, but you're going to have big engineering issues. If you put something into a flame, you might have some mechanical issues, you might burn off the electrical connections and that would defeat the purpose of putting it there.

Chris - Is it really that much energy? It's big and visual but it's probably a trivial amount in a grand scheme of things, isn't it?

Laurie - Yes, it probably is pretty trivial.

When does using TEGs in a power plant become worthwhile?

Andrew - I would say that's an open question at the moment. If I was to really go out on a limb I would say that a megawatt would be the point at which you would get a cost-effective system.

There are many different sorts of beer

55:57 - Can you brew beer in zero gravity?

Could we set up a brewery in orbit, to keep the astronauts refreshed? Is there any reason we couldn't brew beer in zero gravity?

Can you brew beer in zero gravity?

We put this question to Professor Charlie Boone, from Toronto University...

Charlie - I have, in fact, sent yeast into space. Our group collaborated with NASA and we sent yeast up in the last shuttle mission. I can guarantee that they grow perfectly well in space.

We never tried to make beer in space, but I would wager that you could make beautiful beer in space. If you take yeast and you mix it up in a broth with glucose, they're going to love eating that glucose, and they're going to turn it into ethanol, just like they would down here on Earth.

There would be a little bit of an issue where they wouldn't settle out of the beer. The gas would be mixing around and you would have to vent off the gas as the yeast grew, and in the end, you'd have a very cloudy beer. That's what I would wager!

We also put this to Dr Barbara Dunn, from Stanford University...

Barbara - As a yeast researcher, and also as an amateur beer maker, I would say that if everything was done at the correct temperature, the yeast would grow fine and in zero gravity, produce a beer. They would make the usual alcohol content and most of the usual flavours.

If you're making a really big batch of beer, you'd actually have to worry about all the carbon dioxide that the yeast make during fermentation and make sure that it doesn't asphyxiate the astronauts.

Finally, after the fermentation is over, I think it would be nearly impossible to bottle the beer. I think everything would go everywhere. So overall, I'd say that it probably wouldn't be the best tasting beer or the best looking beer, but it would be out of this world beer.


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