energy - Science-Education-Research

Batteries – what are they good for?

Okay, 'energy storage' – but what else are they good for?

Keith S. Taber

I was struck by an item on the BBC Radio 4 news headlines at 09.00 this morning (27th Feb. 2023):

"The collapsed battery maker Britishvolt which went into administration last month has been bought by an Australian company.
The new owners will focus initially on batteries for energy storage rather than electric vehicles."
BBC Radio 4 news item

Now on reflection, this was an ambiguous statement. I heard it as

"The new owners will focus initially on batteries for

energy storage, rather than

electric vehicles."

Which immediately provoked in my mind the question what batteries might be used for in electric vehicles – if not 'energy storage'?

It is possible to charge up an electric car because it includes a battery
(Image by Sabine Kroschel from Pixabay)

Conceptions of energy

Now, this whole area is, metaphorically, a bit of a linguistic minefield as when people say batteries they do not usually distinguish between an individual cell and a battery (of cells). Traditional electrochemical cells we are familiar with have a specific and usually modest e.m.f. – 1.5V or 1.2 V for example. The old 6V and 9V batteries that used to be commonly sold for many purposes (before the switch to most appliances having internal batteries) would be batteries of cells connected in series to work together to provide (1.5V + 1.5V + 1.5V + 1.5V = ) 6V (or whatever). Car batteries were traditionally batteries of lead-acid cells connected together. If each cell has an e.m.f. of 2V, then a dozen connected in series (i.e., the battery) offers 24V.

Moreover, energy is a highly abstract idea, such that even physics teachers do not always agree on how to describe it – the model of energy coming in a number of flavours, 'forms', and processes involving transformations in the form of the energy (e.g., a filament lamp converts electrical energy into heat energy) that many of us learnt (and some of us taught) has come to be seen as misleading and unhelpful by some (it not all) educators. Oh, and if you think I made a mistake there and forget that a lamp produces light energy – not at all. In the 'forms of energy' typology, heat is energy transferred due to a difference in temperature – so that covers all the radiation being emitted by the hot filament.

No wonder, that energy is a common topic for student alternative conceptions, as energy permeates (so to speak) all areas of science, but is a highly abstract notion.

Read about conceptions of energy

An alternative hearing?

Yet, I realised that the statement I had heard was ambiguous and could be parsed differently. It perhaps meant

"The new owners will focus initially on

batteries for energy storage

rather than

electric vehicles."

That is, I was putting my imaginary brackets in the wrong place and perhaps the company had previously intended to build complete electric cars and not just the batteries? If so, the news was not

The new owners will focus initially on batteries (for energy storage rather than electric vehicles).

but rather that

The new owners will focus initially on (batteries for energy storage) rather than (electric vehicles).

If this was the intention, it might have been better to have assumed listeners would know that batteries were used for 'energy storage', and to have simplified the statement to

"The new owners will focus initially on batteries rather than electric vehicles."

Batteries for under-performing sports cars?

That made more sense, as surely the BBC's news journalists do not think electric batteries in cars are used for something other than 'energy storage'. So, I checked on the BBC news website, where I found

"The company intends to start by focusing on batteries for energy storage and hopes to have those products available by the end of 2025.

It then intends to produce batteries for high-performance sports cars."
https://www.bbc.co.uk/news/business-64754879

So, I did not misinterpret the news item. According to the BBC (and to be fair, they are probably just reporting, albeit uncritically, what they have been told) under its new owners Britishvolt will

first work on batteries that can be used for energy storage, and
then shift attention to batteries for sports cars.

My best guess is that "batteries for energy storage" is shorthand for large scale devices for long term storage (that could, for example, be charged by wind generators when it is windy, and then later fed into the National Grid at times of high power demand). The characteristics of these devices would surely be different in detail from batteries used in electric vehicles.

However, I am pretty sure that "batteries for high-performance sports cars" also need to provide 'energy storage' or else those cars are not going to offer the kind of performance Britishvolt and the car manufacturers they will supply are looking for. After all, besides 'energy storage', what else are batteries actually good for?

Another late night writing copy in the newsroom?
(Image by mohamed_hassan from Pixabay)

Temperature is measuring the heat of something …

Keith S. Taber

Image by Peter Janssen from Pixabay

Bill was a participant in the Understanding Science Project. Bill, then in Y7, was telling me about work he had done in his science class on the states of matter, and what happened to the particles that made up objects during a change of state. He suggested that "when a solid goes to a liquid, the heat gives the particles energy to spread about, and then when its a liquid, it's got even more energy to spread out into a gas". Later in the interview I followed up to find out what Bill understood by heat:

Now you mentioned earlier, something about heat. When you were talking about the experiment you did.
Yeah.
Yeah. So tell me about the heat again, what's, how does the heat get involved in this solids, liquids and gases?
When I heat, when heat comes to a solid, it will have, erm, a point where it will go down to a liquid,
Okay,
A melting points of the, the object.
Do you know what heat is? If you had a younger brother or sister, and they said to you, 'you are good at science, what's heat?'
I'm not sure how I can explain it, 'cause it's, it can be measured at different temperature, it can be measured at temperature, erm, by degrees Celsius, degrees Fahrenheit, and – I'm not really sure how I could explain what it is, but, I know it can be measured and changed.
So is it the same thing as temperature, do you think, or is it something different?
Erm, I think temperature is measuring the heat of something.
So they're related, they're to do with each other?
Yeah.
But they are not exactly the same?
No.

Bill appreciated that heat and temperature were not the same, but was not entirely clear on the relationship. Distinguishing between heat and temperature is a recognised challenge in teaching and learning physics.

We commonly introduce temperature as a measure of how hot or cold something is – which relates to phenomena that all students have experienced (even if our actual perception of temperature is pretty crude). Heating is a process, and heat is sometimes considered to be energy being transferred due to a difference of temperature (although energy is a very abstract notion and there is much discussion in science teaching circles about the best language to be used in teaching about energy).

Put simply, it is reasonable to suggest a very hot object would have a high temperature, but not that it contained a lot of heat. So, it is strictly wrong to say that "temperature is measuring the heat of something" (and it would be more correct, if not very technical, to say instead "temperature is measuring the hotness of something – how hot something is"). Perhaps the idea Bill wanted to express was more about the heat that one can feel radiating form a hot object (but likely that is an interpretation suggested by the canonical science use of 'heat'?)

This is one of those situations where a student has an intuition or idea which is basically along the right lines, in the sense of knowing there is an association or link, but strictly not quite right – so, an alternative conception. In a teaching situation it might be useful to know if a student actually has a firm conception that temperature measures the amount of heat, or (as seems to be the case with Bill) this is more a matter of using everyday language – which tends to be less precise and rigid than technical language – to express a vague sense. If a student has a firm notion that hot objects contain heat, and this is not identified and responded to, then this could act as a grounded learning impediment as it will likely distort how teaching is understood.

The teacher is charged with shifting learners away from their current ways of thinking and talking, towards using the abstractions and technical language of the subject, such as the canonical relationship between heat and temperature – and this often means beginning by engaging with the learners' ideas and language. Arguably the use of the term 'heat capacity' (and 'specific heat capacity') which might suggest something about the amount of heat something can hold, is unhelpful here.

Sleep can give us energy

Sleep, like food, can give us a bit more energy

Keith S. Taber

Jim was a participant in the Understanding Science Project. When I was talking to students on that project I would ask them what they were studying in science, rather than ask them about my own agenda of topics. However, I was interested in the extent to which they integrated and linked their science knowledge, so I would from time to time ask if topics they told me about were linked with other topics they had discussed with me. The following extract is taken from the fourth of a sequence of interviews during Jim's first year in secondary school (Y7 in the English school system).

And earlier in the year, you were doing about dissolving sugar. Do you remember that?
Erm, yeah.
Do you think that's got anything to do with the human body?
Erm, we eat sugar.
Mm. True.
Gives us energy…It powers us.
Ah. And why do we need power do you think?
So we can move.

This seemed a reasonable response, but I was intrigued to know if Jim was yet aware of metabolism and how the tissues require a supply of sugar even when there is no obvious activity.

Ah what if you were a lazy person, say you were a very lazy rich person? And you were able to lie in bed all day, watch telly, whatever you like, didn't have to move, didn't have to budge an eyelid, … you're rich, your servants do everything for you? Would you till need energy?
Yes.
Why?
I dunno, 'cause being in bed's tired, tiring.
Is it?
When I'm ill, I stay off for a day, I just feel tired, and like at the end of the day, even more tired than I do when I come to school some times.

Jim's argument failed to allow for the difference in initial conditions

Staying in bed all day and avoiding exercise could indeed make one feel tired, but there seemed something of a confound here (being ill) and I wondered if the reason he stayed in bed on these days might be a factor in feeling even more tired than usual.

So maybe when you are ill, you should come to school, and then you would feel better?
No.
No, it doesn't work like that?
No.
Okay, so why do you think we get tired, when we are just lying, doing absolutely nothing?
Because, it's using a lot of our energy, doing something.
Hm, so even when we are lying at home ill, not doing anything, somehow we are using energy doing something, are we?
Yes.
What might that be, what might we use energy for?
Thinking.

I thought this was a good response, as I was not sure all students of his age would realise that thinking involved energy – although my own conceptualisation was in terms of cellular metabolism, and how thinking depend on transmitting electrical signals along axons and across synapses. I suspected Jim might not have been thinking in such terms.

Do you think it uses energy to think?
(Pause, c.3s)
Probably.
Why do you think that?
Well cause, like, when you haven't got any energy, you can't think, like the same as TV, when it hasn't got any energy, it can't work. So it's a bit like our brains, when we have not got enough energy we feel really tired, and we just want to go to sleep, which can give us more energy, a bit like food.

So Jim here offered an argument about cause and effect- when you haven't got any energy, you can't think. This would certainly be literally true (without any source of energy, no biological functioning would continue, including thinking) although of course Jim had clearly never experienced that absolute situation (as he was still alive to be interviewed), and was presumably referring to experiences of feeling mentally tired and not being able to concentrate.

He offered an analogy, that we are like televisions, in that we do not work without energy. The TV needs to be connected to an electrical supply, and the body needs food (such as sugar, as Jim had suggested) and oxygen. But Jim also used a simile – that sleep was like food. Sleep, like food, according to Jim could give us energy.

So sleeping can give us energy?
Yeah.
How does that work?
Er, it's like putting a battery onto charge, probably, you go to sleep, and then you don't have to do anything, for a little while, and you, then you wake up and you feel – less tired.
Okay so, you think you might need energy to think, because if you have not got any energy, you are very tired, you can't think very well, but somehow if you have a sleep, that might somehow bring the energy back?
Yeah.
So where does that energy come from?
(Pause c.2s)
Erm – dunno.

So here Jim used another analogy, sleeping was like charging a battery. When putting a battery on change, we connect it to a charger, but Jim did not suggest how sleep recharged us, except in that we could rest. When sleeping "you don't have to do anything, for a little while", which might explain a pause in depletion of energy supplies, but would not explain how energy levels were built up again.

[A potentially useful comparison here might have been a television, or a lap top used to watch programmes, with an internal battery, where the there is a buffer between the external supply, and the immediate source for functioning.]

This was an interesting response. At one level it was a deficient answer, as energy is conserved, and Jim's suggestion seemed to require energy to be created or to appear from some unspecified source.

Jim's responses here offered a number of interesting comparisons:

sleep is a bit like food in providing energy
not having energy and not being able to think is like a TV which cannot work without energy
sleeping is like putting a battery on charge

Both science, and science teaching/communication draw a good deal on similes, metaphors and analogies, but they tend to function as interim tools (sources of creative ideas that scientists can then further explore; or means to help someone get a {metaphorical!} foothold on an idea that needs to later be more formally understood).

The idea that sleeping works like recharging a battery could act as an associative learning impediment as there is a flaw in the analogy: putting a battery on charge connects it to an external power source; sleep is incredibility important for various (energy requiring) processes that maintain physical and mental health, and helps us feel rested, but does not in itself source energy. Someone who thought that sleeping works like recharging a battery will not need to wonder how the body accesses energy during sleep as they they seem to have an explanation. (They have access to a pseudo-explanation: sleep restores our energy levels because it is like recharging a battery.)

Jim's discourse reflects what has been called 'the natural attitude' or the 'lifeworld', the way we understand common experiences and talk about them in everyday life. It is common folk knowledge that resting gives you energy (indeed, both exercise and rest are commonly said to give people energy!)

In 'the lifeworld', we run out of energy, we recharge our batteries by resting, and sleep gives us energy. Probably even many science teachers use such expressions when off duty. Each of these notions is strictly incorrect from the scientific perspective. A belief that sleep gives you energy would be an alternative conception, and one that could act as a grounded learning impediment, getting in the way of learning the scientific account.

Yet they each also offer a potential entry point to understanding the scientific accounts. In one respect, Jim has useful 'resources' that can be built on to learn about metabolism, as long as the habitual use of technically incorrect, but common everyday, ways of talking do not act as learning impediments by making it difficult to appreciate how the science teacher is using similar language to express a somewhat different set of ideas.

Plants mainly respire at night

Plants mainly respire at night because they are photosynthesising during the day

Keith S. Taber

Mandy was a participant in the Understanding Science Project. When I spoke to her in Y10 (i.e. when she was c.14 year old) she told me that photosynthesis was one of the topics she was studying in science. So I asked her about photosynthesis. She suggested that "respiration produces energy, but photosynthesis produces glucose which produces energy". (See 'How plants get their food to grow and make energy'). She told me that she respired to get energy.

How do you get your energy then?
We respire.
Is that different then [from photosynthesis]?
Yeah.
So what's respire then, what do you do when you respire?
We use oxygen to, and glucose to release energy.
Do plants respire?
Yes.
So when do you respire, when you are going to go for a run or something, is that when you respire, when you need the energy?
No, you are respiring all the time.
… What about plants? Do they respire all the time?
They mainly do it at night.
Why's that?
'cause they're photosynthesising during the day, cause they need the light.

I was not clear why Mandy thought that plants should respire less when they were photosynthesising.

So why do you need to respire all the time?
'cause you're making energy and you need energy to do everything.
So are you respiring at the same rate all the time, do you think?
No.
So sometimes more than others?
Yeah.
So when might you need to respire more?
When you are doing exercise. Running around a lot.
So are there time when you do not need to respire as much?
Yeah.
So when might you not need to respire very much?
When you 're sleeping or just sitting watching tele [television].
…Do you have to respire at all during the night – you are not doing anything are you?
You need a little bit of energy.
What for?
Erm, I don't [indistinct], well I suppose it's just to keep everything, cause if you did not have energy then your heart would not beat, and you need it to keep breathing, and your heart pumping.

Mandy recognised the need for people to respire continuously, although she associated this with functioning at the organism level (breathing, blood circulation) and did not seem to be thinking about cellular level metabolism.

Why do plants need to respire? What do they use it, the energy for?
Erm, to grow, and to fix cells that are – broken.
Oh right, like repair damage?
Yeah.
So, do you think they are like us then, that they sort of sleep sometimes and don't need to respire as much, or?
Not as much, I don't know. I don't know.
Do you think a plant sleeps, a tree has a good sleep?
No.
So when do you think plants need to respire the most, or do you think they respire the same all the time?
They respire more at night, because – they do it then instead of in the day because they do photosynthesis during the day, but they still respire a little bit.
So is it difficult to try and do both at the same time?
Probably.
Or just maybe they are too busy photosynthesising to do much respiration?
Yeah, erm, I don't know.
Not sure?
No.

Mandy was not offering any specific reason why a plant should need to respire less at night (and did not seem to have previously thought about this), but simply seemed to assume that when the plant was photosynthesising a lot it would only respire "a little bit". This seemed to be an intuition rather than a considered proposition. It was almost as if she implicitly assumed that the plant would be fully occupied photosynthesising, and so would put respiration 'on the back burner'.

It seemed Mandy's understanding of the roles of photosynthesis and respiration at that point in her learning was limited by not fully seeing how energy was involved in the two processes (i.e., respiration produces energy, but photosynthesis produces glucose which produces energy), and because she was not considering the need for respiration to support ongoing basic cell functions.

How plants get their food to grow and make energy

Respiration produces energy, but photosynthesis produces glucose which produces energy

Keith S. Taber

So, photosynthesis. If I knew nothing at all about photosynthesis, how would you explain that to me?
It's how plants get their food to grow and – stuff, and make energy
So how do they make their energy, then?
Well, they make glucose, which has energy in it.
How does the energy get in the glucose?
Erm, I don't know.
It's just there is it?
Yeah, it's just stored energy

I was particularly interested to see if Mandy understood about the role of photosynthesis in plant nutrition and energy metabolism.

Why do you think it is called photosynthesis, because that's a kind of complicated name?
Isn't photo, something to do with light, and they use light to – get the energy.
So how do they do that then?
In the plant they've got chlorophyll which absorbs the light, hm, that sort of thing.
What does it do once it absorbs the light?
Erm.
Does that mean it shines brightly?
No, I , erm – I don't know

Mandy explained that the chlorophyll was in the cells, especially in the plant's leaves. But I was not very clear on whether she had a good understanding of photosynthesis in terms of energy.

Do you make your food?
Not the way plants do.
…
So where does the energy come from in your food then?
It's stored energy.
How did it get in to the food? How was it stored there?
Erm.
[c. 2s pause]
I don't know.

At this point it seemed Mandy was not connecting the energy 'in' food either directly or indirectly with photosynthesis.

Okay. What kind of thing do you like to eat?
Erm, pasta.
Do you think there is any energy value in pasta? Any energy stored in the pasta?
Has lots of carbohydrates, which is energy.
…
So do you think there is energy within the carbohydrate then?
Yeah.
Stored energy.
Yeah.
So how do you think that got there, who stored it?
(laughs) I don't know.

Again, the impression was that Mandy was not linking the energy value of food with photosynthesis. The reference to carbohydrates being energy seemed (given the wider context of the interview) to be imprecise use of language, rather than a genuine alternative conception.

So do you go to like the Co-op and buy a packet of pasta. Or mum does I expect?
Yeah.
Yeah. So do you think, sort of, the Co-op are sort of putting energy in the other end, before they send it down to the shop?
No, it comes from 'cause pasta's made from like flour, and that comes from wheat, and then that uses photosynthesis.

Now it seemed that it was quite clear to Mandy that photosynthesis was responsible for the energy stored in the pasta. It was not clear why she had not suggested this before, but it seemed she could make the connection between the food people eat and photosynthesis. Perhaps (it seems quite likely) she had previously been aware of this and it initially did not 'come to mind', and then at some point during this sequences of questions there was a 'bringing to mind' of the link. Alternatively, it may have been a new insight reached when challenged to respond to the interview questions.

So you don't need to photosynthesise to get energy?
No.
No, how do you get your energy then?
We respire.
Is that different then?
Yeah.
So what's respire then, what do you do when you respire?
We use oxygen to, and glucose to release energy.
Do plants respire?
Yes.
So when do you respire, when you are going to go for a run or something, is that when you respire, when you need the energy?
No, you are respiring all the time.

Mandy suggested that plants mainly respire at night because they are photosynthesising during the day. (Read 'Plants mainly respire at night'.)

So is there any relationship do you think between photosynthesis and respiration?
Erm respiration uses oxygen – and glucose and it produces er carbon dioxide and water, whereas photosynthesis uses carbon dioxide and water, and produces oxygen and glucose.
So it's quite a, quite a strong relationship then?
Yeah.
Yeah, and did you say that energy was involved in that somewhere?
Yeah, in respiration, they produce energy.
What about in photosynthesis, does that produce energy?
That produces glucose, which produces the energy.
I see, so there is no energy involved in the photosynthesis equation, but there is in the glucose?
Yeah.

Respiration does not 'produce' energy of course, but if it had the question about whether photosynthesis also produced energy might have been expected to elicit a response about photosynthesis 'using' energy or something similar, to give the kind of symmetry that would be consistent with conservation of energy (a process and its reverse can not both 'produce' energy). 'Produce' energy might have meant 'release' energy in which case it might be expected the reverse process should 'capture' or 'store' it.

Mandy appreciated the relationship between photosynthetic and respiration in terms of substances, but had an asymmetric notion of how energy was involved.

Mandy appeared to be having difficult appreciating the symmetrical arrangement between photosynthesis and respiration because she was not clear how energy was transformed in photosynthesis and respiration. Although she seemed to have the components of the scientific narrative, she did not seem to fully appreciate how the absorption of light was in effect 'capturing' energy that could be 'stored' in glucose till needed. At this stage in her learning she seemed to have grasped quite a lot of the relevant ideas, but not quite integrated them all coherently.

Energy cannot be made or destroyed (except in biology)

Keith S. Taber

Energy can be made, but only in biology: Amy had learnt that respiration was converting glucose and oxygen into energy – but had learnt in physics that energy cannot be made

Amy was a participant in the Understanding Science Project. Amy was a Y10 (14-15 year old) student who had separate lessons in biology, chemistry and physics. When I spoke to her (see here), she had told me that respiration was "converting glucose into energy and either carbon dioxide and lactic acid, or just carbon dioxide". When I spoke to her again, some weeks later, Amy repeated that respiration was "converting oxygen and glucose into energy and carbon dioxide…it produces energy" ; that trees "need to produce energy and when they photosynthesise they produce like energy"and that food is "broken down and converted into energy".

Later in the same interview I asked her about her physics lessons, where she had been told that "there's like different types of energy" and that it "cannot be made or destroyed, only converted". Amy did not seen to have recognised any conflict between how she understood the role of energy in biology, and what she was taught in physics.

However, on further questioning, she seemed able to recast her biology knowledge to fit what she had been taught in physics:

So in physics, they tell you (that) you cannot make or destroy energy.
Yeah.
And in biology, they tell you that you can make energy from oxygen and glucose?
(No response – Pause of c.2 seconds)
But only in biology, not in physics?
Oh, erm, I suppose the energy, erm well in respiration, erm the energy must be converted from stored energy in food.

So in an interview context, once the linkage was explicitly pointed out, Amy seemed to recognise that the principle learnt in physics should be applied in biology. However, she did not spontaneously make this link, without which the nature of respiration was misunderstood (in terms of energy being created from matter). This would appear to be an example of a fragmentation learning impediment, as although Amy had learnt about the conservation of energy she did not immediately how this related to what she had studied in biology, about respiration.

Converting glucose and oxygen into energy

Keith S. Taber

Amy was a participant in the Understanding Science Project. Amy was a Y10 (14-15 year old) student who had separate lessons in biology, chemistry and physics. When I spoke to her, she told me that in biology she was studying respiration which she suggested was "converting glucose and oxygen into energy…through anaerobic respiration and aerobic respiration". This involved "converting glucose into energy, glucose and oxygen into energy and either carbon dioxide and lactic acid, or just carbon dioxide. Something like that".

In physics lessons she had been studying the topic of electricity, and she recognised that energy was an idea which appeared in both topics:

The work in physics on electricity and the work in biology on respiration, is there any connection there?
Well, in respiration energy is produced, and in physics energy is stored in a battery or a power supply and that then travels round – the circuit.

When I spoke to her again, some weeks later, Amy repeated that respiration was "converting oxygen and glucose into energy and carbon dioxide". She told me that this was important "because it produces energy which like in humans your body needs, well in anything, your body needs and to grow and move and things like that". She also told me that trees were "living and they need to produce energy and when they photosynthesise they produce like energy anyway" but that she obtained energy "through food which is then broken down and converted into energy".

It is a basic principle in science, that energy cannot be created or destroyed. (Since Einstein, is has become clear that strictly matter can be considered as if a form of energy, and interconversion can take place, for example in nuclear processes, but this effect is negligible in normal chemical systems.) What Amy took away from her biology classes, though, was that energy could be produced in respiration and photosynthesis, and that indeed glucose and energy were converted into energy in respiration (i.e., an alternative conception). Amy did not seem to be applying the principle of energy conservation here – although it transpired (see here) that she had recently studied this in her physics lessons.

Plants store sunlight

Keith S. Taber

Bill was a Y7 student participating in the Understanding Science project. He used the idea of energy in talking about some aspects of his science. So when considering melting "the particles in (a solid), would have the energy, to move about more, and then it would melt down, because of its melting point, and go into a liquid". Although he could not explain what energy was, he knew "it gives something – the energy to move, it will make something else move or something". He remembered having done some work "where we had to make elastic band powered, 'cause the elastic band stored the energy to make it move", so energy could be stored.

Bill also told me about how in his previous school "we did a lot about plants, and – inside them, how they produce their own food". He explained that "inside, it has leaves, inside it, there is chlorophyll, which stores sunlight, and then it goes, then it uses that sunlight to produce its food. It also uses water from the roots, and the soil, and oxygen in the air. So it needs sunlight, oxygen and water to make its food and live."

However, Bill did not relate this process to the notion of energy, and see that the 'storing sunlight' might have been like the energy stored in an elastic band:

Interviewer: We were talking about energy just now.
Bill: Yeah
I: Do you think that's got anything to do with energy? That process you just talked about?
B: Hm, erm, (pause, c.3 seconds) I'm not sure

So Bill did not make the connection between storing energy, and what he interpreted from his science lesson as 'storing sunlight'. This appears to be an example of a fragmentation learning impediment.