Pragmatic 46: Out of Steam About Steam

20 November, 2014


We delve into energy conversion efficiencies of solar photovoltaics, fuel cells, the Hydrogen Economy, steam and hydro-turbines and ways you can conserve energy in your home.

Transcript available
Welcome to Pragmatic Pragmatic is a weekly discussion show contemplating the practical application of technology. Exploring the real-world trade-offs, we look at how great ideas are transformed into products and services that can change our lives. Nothing is as simple as it seems. This episode is sponsored by Igloo, a new sponsor. An intranet you'll actually like, built with easy to use apps like file sharing, blogs, calendars, task management and lots more. Visit to get started today. It's free to use for up to 10 people. This episode is also sponsored by is the easy and affordable way to learn where you can instantly stream thousands of courses created by experts in their fields of business, software, web development, graphic design, and lots more. Visit to get a free 7-day trial. If you've ever wanted to learn something new, what are you waiting for? We'll talk more about them during the show. I'm your host, Jon Chidjie, and I'm joined once again today by my co-host, Vic Hudson. How's it going, Vic? It is good, Jon. How's it going for you? is going very well. So just quickly, it's possible to see a list of topics I'll be covering on the show in coming weeks at and I've also started to release an equivalent to the After Dark at like /b-side/ you know doesn't fit into the show thing and I'm calling it Adenda. It's at Go check it out. Well tonight, sorry, I should say this episode because it may not be nighttime when you're actually listening to this episode. So, I apologize for the presumption that it's going to be nighttime when you're listening to it. It may not be nighttime when you're recording it. Indeed, if you're on your part of the little ball that we live on. So, yes, actually, it's not such a little ball. Anyway, this particular topic was suggested by Kaya. I know I've pronounced his name before and I've got it right, so the pressure is on me to remember how I pronounced it. Latinen, Kaya Latinen. Suggests on the 9th of October. So this is going back a few weeks now, and it was the highest voted topic in the list. So I'll read out the whole topic suggestion, and I'll tell you what we're going to cover and what we're not. Okay, so the full topic is "Efficiency of various energy production methodologies such as nuclear, gas, coal, solar, wind, etc. Finding ways to reduce energy usage and debating the path to cleaner energy." So the problem with this topic, and I mean, I say the problem with this topic, I don't mean that in a detrimental way, but the fact is that I've already talked about some of this stuff previously on episode two, the battery problem. And the thing about the battery problem is that it's kind of the fan favourite episode of Pragmatic, at least so far anyway. I mean, here we are at episode 46. It's the fan favourite insofar as it's had the most feedback of any episode that I've made. More than Coffee, although Coffee's had the most downloads. As I say, the battery problems had more feedback and more requests for more information. So, and that's reflected by the fact that it's already had four follow-up episodes. So, I did stop and think when I got this topic suggestion whether or not I would simply do part E to the follow-up for the battery problem, but I decided not to. I think we'll do this as a standalone episode. Got to draw a line at some point. So, Kai sort of, when he made the suggestion, I want to break this into two pieces and I guess I'm going to start by recommending if you haven't haven't listened to episode 2, go back and listen to it and all of the follow-up episodes there is a lot in them. So what I want to do is I want to focus specifically on efficiency so we'll talk specifically about efficiency of different generation technologies as in energy generation although technically I guess it's electricity generation and it's energy conversion so energy conversion being different from you know because you can't create energy. So the other piece I'm going to look into is I'm going to look into the environmentally friendly approaches that you can take the, you know, again, like the namesake of the show, the pragmatic approaches you can take to improve energy efficiency in your house. So those are the two paths I want to explore, and mainly because a lot of the other stuff in that in that topic has already been covered. What do you think? Sounds good. The other thing I'm going to do also in the next 10 or so is I'll be doing a few more topics like it that is sort of along those lines, but going into a lot more detail. But keep an eye on the site, you'll see what I mean as things come up. There's an excellent resource for information on this subject. It's called Electropedia. There's a link in the show notes. Highly recommend checking it out. it has a absolute ton of information about energy efficiency, different technologies, it really is a great resource. Okay, so let's talk about conversion of energy, not cost effectiveness. So this has got to be clear up front here. I don't want to talk about the cost effectiveness of it, I don't want to talk about reliability of supply, I don't want to talk about maintenance costs, we're just going to focus on efficiency. Now, the problem is... The efficiency of the conversion. Exactly. The problem is, if you were to look at the efficiency of the conversion of all the different technologies, you would see hydroelectricity at the top of the list. And you would see PV cells, photovoltaic cells, solar cells, you'd see them almost at the bottom. And you might start thinking, well if we just installed hydro everywhere and throw everything else away we'd be fine, right? Obviously, that's not the whole story. Hydro plants are enormous. You have to drown massive areas of the countryside to build efficient, decent sized hydroelectric plants. And the fact that you can put a solar panel on your roof, pretty much anywhere you like in the world, without impacting anything, well, you know, obviously that's a big difference, a big deal. You can't ignore that kind of flexibility. Oh yeah, and it's a heck of a lot cheaper So it's not the whole story But it's still definitely worth looking at the different efficiencies and the different trade-offs So I think it is interesting, yes, I think it is worth diving into, I mean after all we've picked this topic But ultimately the pragmatic solution to our energy problems is not just about efficiency It has to be balanced with cost, feasibility, environmental impacts, all that stuff All right, enough about that So I want to break it down into the three specific values that are often quoted The first and often quoted one is the theoretical limit So the theoretical efficiency limit Then I want to talk about the present laboratory best or the lab best So the best that they can do in a controlled environment And then finally, where we are currently with the mass produced efficiencies of these different technologies In other words, right now I can mass produce 100 generators They are the best one you're looking at a mass produced value of about this So that's the realistic right now with current technology This is what we can create So when I speak theoretical, I guess I'm talking about the materials and technologies that don't necessarily currently exist We assume someday that they could exist But and then maybe we'd be able to reach that theoretical limit But, you know, theoretical limit means theoretical as in right now not possible. So, let's be clear about that up front. And as far as laboratory goes, that ignores our physical capability to actually manufacture these things en masse, whether that's solar cells, whether it's fuel cells, whether or not it's a hydro plant, you know, there are limitations to how big we can make machines like internal combustion engines, which we'll get to, is there's a physical limitation that you start reaching when you try and mass produce these things. Not everything scales. And a good example of this is nuclear fission. You know, we can, we know that equals MC squared, we know you smash together deuterium and tritium and you will get helium and you'll get a heck of a lot of energy. Okay, we know that we can do that in a laboratory environment for a short period of time. Have we got any nuclear fission power stations that actually work in the world yet? And the answer is no. I didn't think so. No, I mean, they have them, but they don't produce more energy than they consume in order to start the reaction. Yeah. So they do exist. So it's kind of a watch. Yeah, exactly. They're theoretical reactors. Hang on. What? That's really the wrong word. They're experimental reactors. So they do exist, but they don't actually generate a positive, a net surplus of energy, at least not consistently. So they can for a short period of time, then they got shut down So really not that useful Okay So what is efficiency? What do you reckon Vic, what is it? I think it's a way to measure the return versus investment of something Yep, exactly. And to put it in just using the word energy, it's energy out divided by energy in. So energy can be in lots of different forms. Anything that burns, you know, typically has to do with chemical energy. The reaction of a compound, whatever it might be, with oxygen releasing heat as a byproduct, you know, and we use the heat usually to turn water into steam and then we use the steam to drive a bunch of fan blades in a turbine and that in turn turns a generator. So for example, with coal, you know, we burn it in a boiler. So we crush up the a coal into a fine dust, burn it, and that, you know, in a boiler that heats up water going through pipes in a boiler that makes steam. Then we use the steam to drive the turbine. Solar thermal, all that infrared heat energy from the sunlight is concentrated in a molten salt and that makes steam. And then that steam drives turbine. Now, even with nuclear energy, you know, E=mc2 and all that, we split some uranium, some plutonium, It breaks apart, generates a whole bunch of heat, hopefully we leave enough control rods in there. So it doesn't do anything crazy. And that heat generates steam and steam drives turbine. Geothermal, same kind of thing, drill a hole in the ground down to a molten pocket, what do you do? Pump water down there, whoa, we're making steam, steam's driving a turbine. See a common theme here. Many people have said that the steam engine is the largest generator of electricity in the world because technically it really is because all the technologies we hang off the end of them whether or not it's nuclear fusion, whether or not it's coal fired, whether or not it's gas fired, all of these things they all essentially generate steam to drive a steam turbine pretty much. Yeah. However, there are, of course, different ways of driving the generator and you can actually directly mechanically drive the generator with, for example, an internal combustion engine. So we're taking chemical energy, we're physically forcing that to turn around, well, in an internal combustion engine that's reciprocating, I guess if it's a rotary engine, then it generates rotary action. but the point is that it physically spins a shaft and there's no steam involved. Then hydroelectricity falls into the same category. We have a massive propeller or set of propellers, you know, the water pressure forces of a turn that directly drives the generator. So I'll call them, you know, direct mechanically driven. But you know, once your energy is sort of rotational, then you get all the losses that come along with that. But it's pretty consistent across all the different technologies. Once you reach that shaft, all the efficiencies between 95 to 99%. It's pretty high, pretty high efficiency once you reach that point. So the only losses you really get are resistive losses in the windings, which is kind of obvious and and also obvious is the friction because, you know, this thing turns around, you got gravity acting on it. You know, therefore it's going to experience friction in the bearings and so on and so forth. So and that resist resistance to need maintain. Yeah, exactly. Moving parts, right. So that's all of the... Those are the energy, different kinds of energy conversion generation technologies we're going to touch on, except for two more specials. And these are ones that don't actually turn a single thing. So they're special. Solar, when I say solar, I mean photovoltaic solar and fuel cells. And they're unique in so far as they convert either photonic energy or electrochemical energy directly into electrical energy without turning anything mechanical. And that has all sorts of other benefits, not just from the efficiency point of view, because you may say, OK, well, they don't have that. You know, they don't have to worry about the 95 to 99 percent efficiency that you're losing in spinning up a generator to generate electricity through magnetic fields, rotating magnetic fields and all that stuff. No, no, you don't have to worry about that. So it's perfect. But that's actually not true because you still have to go through because those technologies will generate direct current. So so long as you've got devices that rely on AC or you've got transmission lines with transformers that require AC, you have to go through a DC to AC converter. You lose some in the conversion. So it's not perfect either. So what we're going to do is we're going to cut that out and we're going to ignore that. we're going to say that I'm only interested in the conversion efficiencies up to the point where I'm spinning my shaft. At that point in time, it's a level playing field. I mean, it's not exactly, but it's close enough because the efficiencies you're going to get out of your AC to DC, AC to AC, DC to DC, DC to AC, whatever converter combination you like, you are still going to get somewhere between 95, 99% efficiency out of that converter, just as you're going to get around about that kind of conversion efficiency out of your actual electrical generator. Fair enough. A few more things we're going to ignore. We're going to ignore transmission losses, we're going to ignore insulation requirements. And mainly because I don't think they're relevant to the discussion. And before we get stuck into the very first one, I just need to quickly touch on the basis of this. I've kind of mentioned it, but the law of conservation of energy states that the total energy in an isolated system cannot change. It can only be converted between different forms of energy. So there are no, what do they call them? Ain't no perpetual motion machine in this house. Doesn't exist. So anyone that thinks you can make a perpetual motion machine, just forget it. Alrighty, let's start with the internal combustion engine, shall we? What do you reckon? Sure. All right. So internal combustion engines, I just want to break that into two pieces, gasoline and diesel. And gasoline is typically modeled on something they call the Otto cycle. But in an ideal scenario, you can simplify that to the car no cycle. There's a bunch of formulas, there are links in the show notes, if you're interested in what all that stuff means, go right ahead. But to carry on with that, if you use ideal gases and you simplify it to a car no cycle, you get about 46% efficiency. And that's your theoretical limit. However, engine components have mass, movements, causes friction, inertia, et cetera, because it's reciprocating in the case of reciprocating piston engines. So I said that that's the theoretical limit. That's using ideal materials, a real world theoretical limit for gasoline engines around about 37 percent. As a result of all of the real world implications, this is a very well understood problem. because internal combustion engines have been around for 120 years or longer. It's been a while. All that lost energy, you're thinking to yourself, "Okay, I'm burning my gasoline, where's it going?" Well, it's going out as heat, because you don't want the engine to self-destruct and melt. Therefore, what do you do? You've got to extract the heat. How do you do that? You pump cooling water through the engine, and, well, in the case it's not air-cooled, but then most air-cooled engines tend to break down. It's well certainly in warmer climates like I live in. Anyway, so much fear of V-dubs in the 60s and the Beatles and so on. They just keep breaking in our climate. Anyway, so all that energy is lost as heat. And of course, some of that heat goes out in hot gas in the exhaust. So, there's heat, there's obviously vibration because these engines will vibrate a lot, they're on shock mounts to absorb the vibration but that vibration is vibrational energy. That's lost energy. And of course, noise. Vibration drives, you know, sound waves and those sound waves, that energy is also transmitted that way. So you lose energy in all those different ways. Now, there's a great link on the physics stack exchange that I've put in the show notes that goes into a fair bit of detail about the maths behind internal combustion engine efficiency for gasoline. Now diesel cycles different because of the way in which diesel is combusted without spark plug and high compression ratios and blah blah blah. It can achieve a higher efficiency about 56 percent and that's one of the reasons with high compression diesel that's one of the reasons it's becoming so popular. More than half of the cars sold in Europe are now diesel. You know it's becoming very popular So, the largest and most efficient for its sized engine, internal combustion engine in the world is a diesel engine. It gets about 50% efficiency and it's a marine engine. When I say marine engine, I mean it's meant for a boat. So, the largest diesel generator in the world is 80 megawatts. Yeah. and at that point they tend to stop. Now you may recall if you've listened to episode 2 then you'll recall that I worked at the Stanmore power station, just to recap it's a coal fired power station with 4 4 generator units, 4 turbo generator units and each one is 350MW, so that's 1.44GW so that's a reasonable sized plant and certainly run a couple of toothbrushes. 80MW is nothing compared to that. You know 80 megawatts is a fraction of a generator. Oh right. Yeah one of the one of the turbo generator turbine generators at Stanwell. Now this I this the reason for that is because you as you physically make the internal combustion engine bigger and bigger a lot of the physics it doesn't scale because the pistons simply get too big and they have too much inertia and I have too much loss it becomes inefficient. So internal combustion engines the whole idea of using them for power generation on a massive scale falls apart. They're great for backup generators, they're great for isolated grids that are not huge like well a boat or a remote rural town but that's it. Now before we start we're going to talk about hydroelectric power next but before we do that I'd like to talk about our first sponsor for the and that's Igloo software, new sponsor. In engineering I've worked in a lot of companies that use a mismatched collection of different tools to provide the basic functionality that you need to get your job done. 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Now, if you want more than that, they have an in-house team of web developers and graphic designers that will help you to customize the platform completely to fit your brand, your business and your requirements. Now the free trial experience that they provide, it comes preloaded with three templates. There's an app-based intranet, a corporate intranet and a customer community. And these all have elements of what's possible with Igloo. Once you're in there, it's surprisingly easy to start reorganizing it just the way you like it to fit your needs. Now, thanks to the built-in responsive design, it'll work on any device you could choose, like a laptop, tablet, phone, all the major browsers, Internet Explorer, 8 and up, Chrome, Firefox, Safari, and on iOS and Android's native browsers as well. They also have dedicated apps for iOS, Android, and Blackberry. To add a file, so I'll talk about a couple of the things that I've played with specifically. Add a file to Igloo. 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Their data center partner is SSAE 16 certified, they offer SSL encryption, end to end disaster recovery, single tenant and shared environments, integration with many authentication sync systems, including SAML services and LDAP. Now mid to late last year, that was 2013, I was working for a small startup company called Project Facilitation and based on my own experiences trialing Igloo myself privately, we used it for building our own intranet. It was really handy and saved us from having to develop and try and integrate the pieces that we needed ourselves. Adding and moving around the features we needed was really easy and what you see is what you get made it so much easier to tailor it the way we wanted without having to have any developer skills with a minimal learning curve, we whipped it up very fast. Now, you may have heard people talking about Igloo in the past, but take it from me, I've used it. It is worth your time to check it out. So how can you check it out? It's easy. Just visit igloosoftware, all one word, dot com slash pragmatic, specifically that URL and sign up for a trial. It's free for groups of up to 10 people. There's no credit card required, no obligation. Just sign up and have a play today. And I say have a play because it's so nice. It doesn't feel like work. Anyway, I'd like to thank Igloo for sponsoring Pragmatic. Hydroelectric power. Everyone loves hydro. Something in the water. Do you like hydro power, Vic? Sure. Just don't go swimming at the dam wall, OK? The dam wall. You don't want to go fishing there either, as witnessed by Bart Simpson. Indeed. Alright, so, for efficiency reasons, and because of the design of the different kinds of propellers which we'll actually talk about, you typically will drive the fan blades at a much lower speed than you would run a steam turbine at. So normally an electric motor would run at several thousand RPM, but a hydro generator is geared up from a very low physical RPM to a low running shaft speed. So the synchronous machine equation is, for all those people that would love to know, is NS = 120F/P, where NS is the synchronous speed of the machine, F is the frequency and P is the number of poles. And the scary thing is, I didn't have to look that up, but never mind that. By increasing the number of poles, you can reduce the speed the generator needs to spin at to produce the same output frequency. Less than 5MW sized plants can achieve between 80-85% efficiency. Larger hydro plants will top out about 95% conversion efficiency. The energy conversion is high, but in order to be economical, it needs to be at a larger scale and that's where hydro falls apart. Now, I'm not including tidal or wave-powered options. I discussed that in part A follow-up to episode 2. There's essentially two kinds of hydro power that I want to talk about. There's so-called run-of-river and of course, the obvious one we've already talked about, which is the dam. of rivers designed essentially to be either to be partially immersed propellers, they usually use something called a Pelton turbine. Think of a wheel with a bunch of scoops around it. They're very, yeah, it's kind of like a modern equivalent of a water wheel. And it's common for shallow, fast flowing rivers, and the idea is that the plant will run at the speed that the river runs, hence the name run of river. It's really not that imaginative, actually, come to think of it. Now, dams, on the other hand, and I guess some deeper and slower flowing rivers, they may use a like a Francis reaction or a propeller or Kaplan turbine. And there's links in the show notes if you want to know more about each of those individually and how they're different. But they all tend to rely on higher head pressures to turn them and they turn- And they use the dam to generate that pressure. Yeah, they use the water head pressure, which I'll talk about in a second. So they turn at much slower rotational rates than a Pelton does, but they produce much more torque and you can then gear that torque up to drive a generator. Even then, it still spins at a much slower shaft speed. Now, I mentioned head pressure. For those that don't know what head pressure is, head pressure is the pressure created by a volume of water acting at a given point in a closed system. So imagine you've got a hose, let's say it's 10 feet long. That's three meters long and it's perfectly vertical. Yeah, OK, I know I'm talking about hydraulics, I'm an electrical engineer, whatever. If I press my thumb over the bottom end of that hose, then I fill the hose to the top with water, there will be 10 feet or three meters of head pressure being applied to my thumb trying to seal off the bottom. Because the water isn't moving, that's referred to as a static head pressure. If the water begins to flow, it's affected by the diameter of the pipe, the tube. We start talking about Bernoulli equations, flow dynamics, and I drift off to sleep because I really don't care. But anyway, bottom line is that's what head pressure is. So you have a big dam, you've got 100 meters of head pressure behind it, which is why they like to have a big dam wall and a big dam wall. And no one ever makes that joke. Anyway, and the height of the top of the water down to the lowest part of the dam wall is usually where they will place the actual propeller that drives the generators. So that'll be at the bottom. Sometimes I'll even run them down the side of a hill, so they'll dam at the top of the hill and then they'll run a series of pipes right down to the bottom, as close to the bottom as possible before they actually go through and start generating flow through the propellers. And the reason they do that is where they want to maximize the head pressure. Yeah, more pressure, more efficient. Obviously, that's a problem, you know, if you've got, you know, a large area of land that's mostly flat and is bounded by a bunch of mountain ranges, you plug up the exits, that's well and good. But is that enough to make a hydroelectric power station? And the answer is usually no, you need the height, you need the head pressure. So it's not just as easy as building a dam. Anyway. So that's hydro. Hydro sounds awesome until you have to flood everything. Anyway, again, talked about a lot more about the other aspects of hydro in Episode 2. Go have a listen to that if you want to know a bit more about the other consequences of hydro. I don't want to cover that again. OK, so let's talk about steam engines and turbines. So steam engines have two basic types. There's the impulse type and the reaction type. Now, there's a link in the show notes to a site that has a very good discussion about steam engines and steam turbines. I am going to read from that, I've copied what they've got for the next two bits about the way that they work, but I've tweaked the wording slightly. It just said it better than I thought. I didn't see the reason to reinvent these two things. So this is... Visualize this as best you can based on the words, because I have no images to show you. Got it. The steam jets are directed... Sorry, this is a... Sorry, this is an impulse turbine. The steam jets are directed at the turbines bucket shaped rotor blades where the pressure exerted by the jets causes the rotor to rotate and the velocity of the steam to reduce as it imparts its kinetic energy to those blades. The blades in turn change the direction of flow of the steam, however, its pressure remains constant as it passes through the rotor blades, since the cross section of the chamber between the blades is constant. Impulse turbines are therefore also referred to as constant pressure turbines. The next series of fixed blades reverses the direction of the steam before it passes to the second row of moving blades. Impulse Turbine A reaction turbine is when the rotor blades of the reaction turbine are shaped more like aerofoils and are arranged such that the cross section of the chambers formed between the fixed blades diminishes from the inlet side towards the exhaust side of the blades. The chambers between the rotor blades essentially form nozzles so that as the steam progresses through the chambers its velocity increases while at the same time the pressure decreases, just as in the nozzles formed by fixed blades would do. Thus, pressure decreases in both the fixed and the moving blades. As the steam emerges in a jet from between the rotor blades it creates a reactive force on the blades which in turn creates a turning moment on the turbine rotor. So you can think of that as essentially it reacts to varying levels of pressure from the steam being forced over the blades as an aerofoil like an aircraft wing. So you'll get a high pressure on one side, low pressure on the other side of it and those reactions will cause it to move. is the kind of turbines that they use at a stand on power station for example. Okay, hopefully people are still with me there. Anyway, eventually the steam will reach such a low pressure when it's done that it can no longer perform any work. So it still has heat and it's not a liquid, it's still steam. is then you need to condense it back into water because you can't pump steam and then you got to pump that water back into the boiler or whatever heating device you're using to go for another cycle. Now the condensing of the steam also has the effect of creating a not a perfect but a partial vacuum and that partial vacuum creates a low pressure zone which draws steam through the turbine which of course therefore further drives the rotation of the turbine by creating an extra low pressure zone at the end. Got it. Okay. Now that particular cycle, they call that a Rankine cycle, and it's been around for quite a while. The biggest problem with a Rankine cycle, and frankly, you know, a lot of these steam engines is that the condensing function represents a significant loss of energy. So that's a problem. So steam engines, the problem that I've got is looking for figures on efficiencies of steam engines It's difficult to get accurate figures because I looked and I looked and I looked to get the exact figures and every time I found exact figures, I found contradicting figures I think there would be a lot of local variables standard into that equation anywhere you tried it Yeah, there are a lot of variables and it's a big simplification for you to simply say, yeah, it's about 30%, 50%? You know, it's like, oh, yeah, OK, that's up to a certain flow rate, a certain amount of pressure, you know, the design of the blades and everything. And it's like, oh, well, OK. And so I've gone through this list. What's the efficiency? Well, it varies from 30% to 60%. That's a horrible answer, but I'm sorry, that's all I could come up with because there's so much variability with steam engines, it's so hard to be sure. and it's so down to the manufacturing details and the specific conditions The problem also you got to consider is that that's just the efficiency of the actual steam turbine part of it And I've read some places say, oh yeah, it's 95% efficient And it's like, well, actually, no, it's not because you're not including the condenser in your efficiency You know, so if a true Rankine cycle would never achieve that You know, law of thermodynamics is going to stop you anyway, so, you know Dear me. So steam, when you consider steam plus the condensing, plus, you know, the boiling, all of that stuff like in a coal-fired power station, it's horrendously inefficient. End-to-end inefficiencies is somewhere between 30 to 40 percent overall. It's really terrible. But because it's so cheap, people don't care, except for the fact, of course, you're pumping tons of carbon dioxide in the atmosphere. Well, there is that. Yeah, bad. Naughty. All right, so I'm done talking about steam, reciprocating engines. I've already talked about nuclear power and how that works previously. Well, briefly, and there's really not much else to say about it. You're out of steam. I'm out of steam about steam. Good one. Oh, my God. Couldn't resist. Sorry. That's fine. So let's talk about solar because I love solar. I think solar is magical and awesome. Now I did cover this in detail in episode two, but there's some more I want to say about it. Essentially though, the way solar works is it's essentially it's doped silicon. And the doped silicon type of photovoltaic cell will have a peak conversion efficiency at a specific wavelength, but depending on how it's been doped with different chemicals. Now, by carefully manufacturing partly transparent layers and using different prisms and so on between layers, it's possible to actually have multiple layers and you can build up a wafer that has different doped layers of silicon. So instead of having a single wavelength cell, you can stack multiple layers to get two and even three different junctions. So each layer will convert a different wavelength. So sunlight that we get is actually consists multiple wavelengths of light and they all blend together to give us white light that our eyes see. Let me look at the sun. Well, hopefully you don't look directly at the sun, it's generally considered to be bad. It is bad for your retina, but anyway. Point is that all those different wavelengths, you can then push your efficiency. So when you are actually looking at the Shockley-Kuizler limit, that in 1961, they figured this out. They said, look, your maximum conversion you're gonna get from a PN junction is 33%. That's for a single junction, but that all assumes a single layer and a single predominant wavelength. Now, you start stacking these things, obviously, you can absorb more energy, you can capture more of the energy, I should say, rather than just being wasted. Now, that then leads to a theoretical limit of between 85 and 90 percent, but that, importantly, that assumes light concentration. And by light concentration, I'm referring to solar concentrators, you know, like parabolic dishes, mirrors, refractors, whatever, you're taking large amount of sunlight falling over a larger area, concentrating it down onto a solar cell in a much smaller area. In other words, you're cheating. Now that's okay, I guess. But if you want to put that on your roof, realistically, that's going to double, triple, quadruple the surface area on your roof you're required to actually have light concentration to go down to those solar cells. And then may well reach a point where they've got a home solar concentrator kit that they figure out some way of doing that nicely and neatly that's maintenance free and doesn't require cleaning and until then, let's just run with the non light concentrated maximum theoretical efficiency of 68% conversion. So that's assuming you can capture all three like three layers, which is roughly where your efficiency tradeoff drops off. Well, actually, I think 68% is assuming an infinite number, but you get very close to 68% with just three, theoretically. So anyway, let's compare and contrast that theoretical limit with the best laboratory result at the moment. And there's a link in the show notes that has a nice thing, a nice chart that shows you all the different lab results by EPEL. And there was a part linked to it in my presentation that I did when I was working at a previous company where I was giving a tech talk regarding solar electric design. And that was linked in episode 2, so go and have a look at that if you really want. It's also linked in the show notes to this one. And it shows you all the different laboratory results up until a few years ago. Best results so far at that point in time of that chart being generated was 41.6% and that was for a Trijunction II terminal monolithic. 41.6. So that's not too far away from 68%, I guess. It's more than halfway. That's something. Anyway, now we bring you back down to earth. How much is the efficiency of a mass produced current market solar cell? What's your best guess, Vic? Last I heard, I don't think they're very good, like maybe 10 or 15 percent, something like that. Boom, spot on 15 percent. So that's your average usual production cell efficiency. And I say usual, I mean, that's actually one of the better ones. I think the exact figure is 15.4 percent. But let's not quibble about the 0.4. So ultimately, that's terrible. Yeah. But because it's cheap to make, you can plaster them anywhere you've got a flat surface or an area that gets sunlight. That changes things, you know, unlike hydro, which requires huge amounts of land, it needs to be high up in order for it to be efficient. Okay. And of course, one of the other best parts of solar is that there's no further loss. Yeah, it's just directly converted to DC away you go. No mechanical conversion necessary. All right, next thing to talk about is fuel cells. Now, I think fuel cells are a very cool technology, but I have my doubts about a lot of aspects. So I want to just focus, there's all sorts of different fuel cells. I just want to focus on hydrogen fuel cells because they're the most commonly used discussed prevalent. Okay. So the concept works like this anode and cathode. It's a fuel cell, kind of like a battery cell, anode cathode, right? The anode reacts with hydrogen and strips the electron from the proton because hydrogen is, you know, one, one H, right? So one proton, one electron. So the anode reacts with that and strips off your electron. The proton is capable of passing through the membrane, but the electron isn't. So as the proton passes out the other side, the electron takes, as it were, the long way around to catch up as it passes out the other side. And that creates an electrical current. That is really simplified, but that's the gist of it. At the cathode, that hydrogen then recombines, it combines with oxygen and that creates water as a byproduct. Sounds super clean, right? Sounds like it. Doesn't it? I'm guessing you're going to tell me it's not. Well, the answer is it depends. And I'll get to why in a minute. So the electron, as it split goes around, it creates about 0.7 volts potential difference in a hydrogen fuel cell. So you stack a bunch of those in series, you get bigger voltages and away you go. Right. You got your DC, you go and happily enjoy your electricity, enjoy your electrons. OK, so key points, needs oxygen to work, but that's OK. Internal combustion engines do too. That's not so bad. Yeah. They generate heat. Guess what? So does an internal combustion engine. No problem. Fair enough. Now, for portable applications, they use a safer and lighter polymer membrane, but the problem of the polymer membranes not as efficient. 50 to 60% conversion efficiency. Respectable, admittedly, but you know, not as good as hydro. Nothing's as good as hydro. Anyway, larger scale plants, however, ones that typically don't move, they'll use molten carbonate or solid oxide membranes. And they can also then harness the heat that's generated by the fuel cell. And that then creates what they refer to as a combined cycle. So you're using the electrical energy plus the heat, the waste heat to generate independently through more traditional means. And essentially, you get a combined cycle efficiency of about 85%. And that sounds really good. However, they are expensive to manufacture. And most importantly, you need hydrogen as the fuel. So how do you mass produce your hydrogen? Okay. Hydrogen is one of the most plentiful elements in the universe. Plenty of hydrogen. Okay, that's great. But mass producing hydrogen on Earth at the moment, it's actually done from something called steam reforming, and that steam reforming is from natural gas. Natural gas is, of course, a hydrocarbon that you get out of the ground, like oil, like coal So you can't discount the natural gas that you're using when you generate your hydrogen That's right, because you're creating greenhouse gases as a byproduct of, you know, reforming this doing steam reforming the natural gas, you're creating greenhouse gases as a byproduct Well, that's not really environmentally friendly, is it? But that's how the majority of hydrogen is mass produced right now today Now, that doesn't mean that that's the way it has to be That's just the way it is at the moment That process takes a lot of energy And I guess the other thing is they say, okay, well, let's do the clean way And we're going to use electrolysis Now, electrolysis is simple enough You pass an electrical current into an anode and a cathode into water And you will get hydrogen collecting around one And you'll get oxygen collecting around the other You're splitting it by through electrolysis But there's a problem with electrolysis, it requires electricity Which you got to get from somewhere else Exactly, and it has a conversion efficiency that is not perfect So what you're essentially doing is you're taking electricity generated from some through some means to split hydrogen and oxygen Once you've split it, that's not enough That hydrogen has to be carried around Now, you're not going to carry it around in a balloon and talk funny when you breathe Maybe, maybe you are, but you know, you can't put that in a car and go any distance. It needs to be compressed into either a highly compressed form of the gas or it needs to be compressed ideally down into a liquid, liquid hydrogen. Yeah. Just like we do with LNG, liquid natural gas, LNG. It's kind of volatile in that state. It's volatile in any state, but hydrogen is nowhere near as reactive as people like to think I mean, everyone thinks Hindenburg, it's actually not as dangerous as you might think But even so, there has that stigma, that doesn't help its cause LNG is just as reactive anyway In fact, in some respects, LNG is more reactive So anyway, the point is that you have to now compress your hydrogen And then you got to ship it around that all of those processes take energy. Where's the energy coming from? Before you even get to generating electricity out of the fuel cell, and remember, energy can't be created, it can only be converted. So in every step of the conversion, you lose energy, you lose energy in some form or another. So what's happening is hydrogen is not a method of generating, of creating energy from something that already exists. Like, you know, if you're burning a hydrocarbon, that energy was absorbed by the sun, by plants and the earth, you know, cooking away at it for thousands and thousands of years, that energy, that's bottled up and you're burning it and that releases the energy that you then use to create work. You know, sunlight is energy from the sun right now and you're converting that into electrical energy. But all a fuel cell is doing is taking hydrogen that you've collected and if you're collecting it through a clean means like electrolysis, all you're doing really is you're not actually releasing energy at all, all you're doing is you're returning the hydrogen that you split from the water back to water again and you're converting it back again and that conversion, you're able to extract electricity from it So, in essence, the hydrogen is storing the energy, it's like a battery So... Hence the term fuel cell Exactly So it's not like any of the other technologies, you know, it's just not. So it's kind of I find this whole thing about everyone says, "Oh, the hydrogen economy, you know, and we're going to have hydrogen fuel cell vehicles and they're great." Well, you know, here's the thing, you've got to make the hydrogen somehow. So what's the ideal plan? Maybe the ideal plan is you put hydropower every place you possibly can. You put solar panels in everywhere else and you do pumped hydro storage for storing your peak energy so you can use it during the night. Hydropower runs 24/7 and everyone's all happy. That's your electricity and then you use that to create hydrogen, use the energy from that to compress it and then you transport it by truck to service stations where people can and then fuel up their cars with hydrogen and then fuel cells in the vehicle, turn the hydrogen into electricity, which then drives the electric motors, which then drives the vehicle. Or you could just put a bunch of batteries in your car and charge them up like a Tesla does and cut hydrogen out of the equation. Yeah. Which is simpler. So the thing is, I find the whole hydrogen economy idea to be somewhat flawed. I don't see it as being any better or any worse than using batteries. And in many ways, it's worse because electrons that are carried over power lines, but those Tesla recharges supercharger stations, right? They take solar power and they buffer it against the grid. You drive your Tesla up, your electric vehicle up, blow a bunch of charge into the batteries, drive your car away again. All of that power has been either taken from the sunlight directly, which has no wires or has come from wires that are already existing, going to power stations that already exist or hydro plants that may exist. It's using existing infrastructure, but with hydrogen, there is no existing infrastructure. Some people, you don't have to build anything. Yeah. You've got to, you've got to have hydro, the, the, the technical safety requirements of liquid hydrogen storage are more strict than for LNG. You can't just use an LNG tank completely as it is. You have to modify it. In some cases, depending upon the standard, you may have to replace it completely to support liquid hydrogen. You know, so and there's still plenty of petrol stations out there that don't have LNG. I mean, I know I can think of several off the top of my head and LNG has been around for 25 years, at least for cars locally where I live anyway. So where does that leave you? It leaves you with the fuel cell is cool. Yes, it is tick. It's efficient. Well, yeah, mostly the portable version, perhaps not as much as people would like, you know, which is where it's going to be most likely used because let's face it, if you're going to have it as a baseload station, why would you use fuel cells? It doesn't make sense from a conversion efficiency point of view. I know, I know that Horace has talked about this on a SIM car and maybe I should get him one day to talk about and have it out with him, but for the moment at least, let's leave it there. So that's hydrogen, that's fuel cells. Don't have anything else to really say about that. So I'd like to just take a moment now to talk about our second sponsor for this episode, and that's is an easy and affordable way to learn. 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So if my house for example that I live in is a slab on ground brick veneer with a corrugated iron roof. Now that's going to be very different to a lot of North American listeners and a lot of European listeners and they're going to have most likely tiled roofs. They may live in houses with a basement and an attic. may live in houses that are single story, split level, above ground, you know, it's very unlikely that they're, we're all in all different kinds of houses and some of the things that I'm going to talk about will apply and some of them won't. So if it doesn't apply to you, just bear with me, it applies to somebody. And if it does apply to you, well, I guess, you know, see what you think. So I just want to focus predominantly on heating and cooling. bit about lighting, but let's just do with heating and cooling, because heating and cooling is a lot of the energy that we use on a day to day basis. OK. Heating in the winter, cooling in the summer, if that was not obvious. So, the value of U, as in the letter U, is often quoted. It's actually a measure of the amount of heat transferred through one square meter of material with a temperature difference of one degree Celsius. Sorry to go metric on you, but that's what it is. So you'll see me mentioning the UW of a particular material. Essentially, that's the thermal transmissibility, thermal conductivity measure that we're going to use. So insulation, let's talk about insulation in the ceiling. Now, if you have a tiled roof, it's a little bit more like a brick wall insulation, right? And the math is very similar to that. But if it's corrugated iron like mine, then it's absolutely vital that you have insulation in the ceiling. If you got tiled roof, it's not quite so critical, still useful to have. Because the thing is that the material itself acts as a thermal... Thermal buffer of sorts, it's the thermal mass, Okay. It starts out cool in the morning, sun comes up, it gradually warms it up. And then when the sun goes down, it takes time, hours even, to dissipate that heat back into the environment. So, you'll find that in the early hours of the day, brick house with a tiled roof is actually quite cool, even though if you were to step outside, it's usually, you know, 5, 10 degrees warmer outside than it is inside the house. But once you get to about nine or 10 in the morning, you know, in summer, that's all gone. And it's now quite hot. And then of an evening, the sun goes down. It'll be a few hours, two or three hours after sunset before that heat dissipates again. So it retains heat, but it also provides a bit of buffer. So it adds hysteresis is technically the right way of saying it. Anyway, so there's a great site called Superhomes UK, and it gives a good list of the different materials and their respective U-values for insulation. So I'm going to pluck out the ones for an example here. So a metal roof with no insulation has a UW of 0.9, whereas a one inch, the same roof but with one inch thick which is 25 millimetre fiberglass insulation drops that back considerably to 0.26. To get down to 0.05 however you need to go to 6 inches, which is 150mm of fiberglass insulation. That's really quite thick. Now, if I, you know, being a little bit, OK, I'm in Australia, so I pluck some Australian numbers, but the average floor area of a house in Australia is 220 square meters. So I'm going to use that roughly as my roof area. It's close enough, you know, for government work or even non-government work, because it's not government work. Anyway, with a 15 degree temperature difference between the inside of the house and the outside of the house, with no insulation, we're looking at a three kilowatt heat loss. With one inch of fiberglass insulation, we'd drop down to under a kilowatt, it's only 850 watts of loss. With six inches of insulation, it's down to 165 watts of heat loss. So that's That's huge. Absolutely enormous. And of course, that goes both ways. So if you're trying to cool the house, the heat is coming in, you want to stop them coming in. So that just gives you an idea of the impact that it has. The problem I've got, though, I say that's fiberglass insulation, right? Well, fiberglass is just one kind. There are so many different types and brands. It is not funny. Here's a list of five funnily named ones. Single-sided polyweave foil, single-sided polyweave foil with R1.5 glass wool bats, single-sided polyweave foil with 30mm anti-glare reflective EPS board, bubble foam foil, double-sided anti-glare foil. And of course, actually, I might just stop there. There's a lot, okay. And obviously, different insulation will have a different transmissibility. So let's just, you know, we'll just run with those figures to say basic fiberglass, nothing fancy. Just to give you an idea anyway. All right. So insulation in the walls. Obviously, two kinds of walls, internal and external walls. So people think that brick, you know, and concrete and rock block. Do you know what I mean when I say rock block? I think so, yeah. So, rock block, for those that aren't sure what it means is that they will take a mould and they will cast it in concrete. Usually it's in the shape of a large rectangle and it's got two holes in it, two large square holes in it. And they will stack these interlocked usually with bricks and mortar, and then they will fill them, they'll put reinforcing bar, or sometimes referred to as reo bar, in through the middle and they'll pour in concrete. Rebar. Yeah, rebar. That's also called rebar. We call them cinder block. there you go, cinder block, there you go, fantastic. And then you fill that up with concrete and it makes a really super strong thick wall as opposed to brick, which is not stabilized with concrete through the middle typically, it's solid brick. - Yeah. - Okay, so you think that those are going to be the best for your thermal insulation, but it's the same problem with the roof tiles that I talked about just before. So they act as a thermal mass, they add hysteresis to the heating and cooling cycle. So you still want to have insulation on that because you want to decouple that thermal cycling of those bricks or the tiles or the roofing from the interior temperature of the house. So it's still worth installing insulation between the brick and the internal wall cavity. Same kinds of numbers, but the gains will be different of course because the sunlight is not on, the sunlight's on the roof all day long from when it comes up to when it goes down pretty much. But with the walls it depends on if they're north and southern, eastern facing and the time of year and the height of the house. So two-story versus single-story. There's many, many variables. The roof is the easy one to do the maths on. That's what I've done. If you want to do your mileage will vary. Not YMMV, it's YMWV. Yes, because it will vary. It may vary. Anyway. Another part of walls are windows. and not ones by Microsoft. These ones, it's important... That was a bad joke. Anyway, which is all I do. Maybe one day I'll come up with a good joke. Anyway, so double glazed windows. Everyone gets... Well, hang on, I was going to say everyone gets. In Australia, it's uncommon to have double glazed windows in residential houses, especially in Queensland, New South Wales, Western Australia. you go to the southern states like Victoria or down Tasmania, it's more common. But even then, central heating is not a given. Many of the houses down south do not have central heating. And double glazing is the sort of thing that people will put into a house that has central heating because it saves so much on heating costs. So here's why. Let's just do some rough math for an average house, 70 square metres, which is 750 square feet of glass area in the house. Now, that may sound like a lot, but think about it. You've got some houses will have almost floor to ceiling windows broken up into two or four pieces. You'll have doors that have got glass inserts, you'll have sliding glass doors that are in all glass, you know, there's actually quite a lot of glass in houses. And why? Because we don't want to look at the inside of a wall. We want to see the pretty, well, we presume pretty view outside. You know, if you're in a if you're in a location where you've got lots of grass and trees and, you know, the dog running around outside, tearing your air conditioning pipes to pieces or your bike seats or your whatever, football, soccer ball, anyway, you know, dogs. Anyhow, or if you're unlucky enough to live in a place where, you know, you've just got the view of an alleyway, well, maybe the alleyway is pretty too. Maybe it's got some nice pretty graffiti on it that you want to look at. Whatever, the point is that you got a bunch of glass and you want to look out there. You don't just look at a concrete wall. If anyone's seen an episode of the goodies where they come with a perfect building that was solid concrete. Yeah, not like that. So we don't want that. We want glass. but the downside is glass is terrible, absolutely terrible as an insulator. So if we look at standard untinted three millimeter, which is an eighth of an inch thick glass with an aluminum frame or aluminum frame, if you prefer to use the brand name, it has a UW value of 6.9. Now remember the roof without insulation was 0.9. This is 6.9. That's terrible. Okay. Now with a 15 degrees, So we'll stick with that number of 15 degrees temperature difference and that's degrees Celsius, which is a difference in Fahrenheit of 27 degrees Fahrenheit. Then that temperature difference, you know, let's say it's overnight, then you're losing is 7.2 kilowatts of heat just through the windows. Now, if you're trying to maintain a temperature inside that house, you need to top that up with heating. So that is heat energy lost, continuous loss. Really not good, huh? So, the best kind of windows in terms of reducing heat loss do not have a metal frame. They have either a UPVC or, believe it or not, good old timber. Yeah. Double glazing. Same kind of glass is fine, 3mm thick which is 1/8" of an inch but you want to have a nice decent air gap between the two layers. 6mm is good, that's a quarter inch air gap. Glass with those sorts of frames, that drops it to less than half, it drops it down to 3.03, you know. So you only lose about 3kW through all the windows. Now that is a heck of a lot better. I mean it's still terrible but it's a heck of a lot better. Now, you know, a lot of places that's actually quite expensive so a lot of places will stick with the steel frame, you know, they've got, they won't have a 6mm gap in them, they'll be less than that, all sorts of reasons, structural reasons, cost reasons, blah blah blah blah blah. Point is though that that's the best you can get and of course single glazed is the worst you can get. Well actually, I suppose the worst you can get is no glass at all just an open hole in the wall. In which case I wonder what the transmissibility is of open air. Never mind that. Okay. That also was a joke that was even less funny. Anyway, if you really, so if you really, really, really don't want to lose heat out of the windows, I've got a great idea. Why don't you block them up with foam insulation? Just block them up, you know, when you're not using them. There you go. Why not? The view won't be so great, but think of it this way, you're saving energy. Anyway, you know, something that's a little bit funny, I think about that, it's actually not so ridiculous. At nighttime, if there's no one in the room and you don't care, you know, if you had a control system on it, you could move an insulator into place of an evening and lock the place down for an evening and that would save power on your heating. Pop to it Vic. I got some some thick drapes that we close in the evening. That probably helps a little bit. And their packaging said that it would. The packaging is the source of all truth. I will leave it at that. Well, the other option I thought of is maybe one day super ultra extra efficient houses will have perfect walls that are perfectly insulated that are perfectly solid. And instead of having a hole in the wall, you have a video screen with a camera looking outside because, you know, the way that energy consumption is reducing, you know, maybe that'll work out to be more energy efficient. Till you lose power, and then, you know, you can't see outside. You don't get any of that pesky sunlight during the day. Yeah, exactly. I don't know. Okay, so angle of the house. Now I know I said it's kind of hard to shift your house once it's built. But then I thought about it. If your house is on stilts, it's actually possible for you to lift it and to move it if you wanted to. Mind you, that's statistically not very common to have houses on stilts anymore. Even in Australia, it's not very common. It's too expensive. expensive. But the idea anyway is if you are building a house and you are in a position to do this, you know, if you've got a house on stilts and lots of money, I guess, you know, you want to keep the sunlight shining on the sides of the house with eaves or with, you know, less windows on them during the summer months and allow the sunlight into windows more readily during the winter time. Anyway, I guess the other idea is, with angling the house, is to angle windows and doors such that you get a natural breeze based on the locale that you live in, it's natural breeze patterns, prevailing wind directions. Which I just realized is the name of a previous episode, but anyway, in a completely different context, and that'll allow air to flow naturally through the house. Yeah. Now, it's all nice and well and good and lovely, but you just I mean, let's be honest, you can't retrofit that. But I have to mention it for the sake of completeness. Now, here's another interesting one, choice of flooring. Now, I originally dismissed this, but it turns out, turns out it's only really a big concern or improvement, rather, if you have an elevated floor. Or a cavity beneath the floor, like, you know, maybe a basement or maybe we're talking about a crawl space. Yeah, crawl space. Exactly. Or maybe we're talking about a multi-story building, you know, where, you know, where we're only heating or cooling one floor on that building and not the hence getting a temperature differential because the temperature differential is the issue that we're fighting against. If you're cooling everything equally and there's a dividing wall, dividing floor, it doesn't matter. If everything's all being cooled equally, there'll be no temperature difference so it doesn't matter if it's insulated or not. You're only trying to insulate it from parts of the house that you are not air conditioning. You're not air conditioning the outside world, therefore there's a temperature differential between the inside and the outside. to control the inside, the outside is too hot, too cold, you're trying to control the inside hence the insulation stops that. If you've got one room in a house, you're trying to keep that one room cool, then the interior wall is fine, insulate the interior walls, you want to trap that energy, that cool energy or if you're heating one room and not the others, like you may not heat the garage, that's quite common in colder climates and you would insulate everything around the garage but you wouldn't bother heating the garage. So it's all about temperature differential. Now my house is a concrete slab on ground, which is quick, cheap and simple, but it's also prone to things like, well, termite intrusion, which isn't good, stress cracking in the slab, blah, blah, blah, who cares, it's a civil engineering problem and I don't care. Anyway, the differences between lino, timber veneer, hardwood, they're really not that great in terms of their thermal conductivity. The ceramic tiles aren't really that good, they're actually a bit worse than that. It turns out that backed carpet, as in rubber backed carpet, is the best. But no matter how you slice it, you need to lay a thermal insulation that allows some air flow so that it stops any wood rotting. That's if you've got wood on either side, which you're probably going to. But it doesn't let drafts in from the outside because obviously that kills it. That kills the effect. Anyway, the problem is it's generally not the biggest bang for the buck. The walls, the ceiling, the windows, much easier to retrofit. So most people in houses don't bother. But if you're in high density living, for example, maybe let's say you're in London with terraced housing, it's actually very common, but for reasons beyond just the thermal side of things, also for sound insulation, because your unit might be on the third floor of a terrace and you might have people living beneath you or the other way around. And the people beneath you, I don't want to hear the people upstairs wandering around playing loud music or doing whatever they may or may not be doing that's not suitable for children. The corkboard and mineral wool bats are the most common materials used for insulating the floor. The payback periods that I saw quoted on one site I looked at, it is linked in the show notes, the 3 to 5-year payback period they say for insulating a suspended floor but only about 8 to 10 years which is not as good for a solid floor. Now, honestly, okay, so it makes sense to me that a suspended floor would be better because it's going to be more effective because you've got more of an air gap and so on and so forth. But the problem with this, I have with this website is that there's a lot of conflicting information out there and they didn't show they're working. I would have loved to have gone through and confirm that honestly I just decided not to do the math on that one and move on but it's the last thing I'd try anyway because it's just the most you know difficult. Okay now there's another one I want to throw in here before we wrap up on things you can do to the house in terms of insulation and it's kind of I guess it's robbing Peter to pay Paul a little bit it's skylights. Now you know I mean when I say skylight? Big glass window on the roof. Damn right. Sometimes there's other versions of them called solar tubes. Same kind of thing, generally a little bit smaller. So the idea is that let's say you've got a part of the house that you ordinarily would have lights on because it's just too dark during the middle of the day or during fringe hours of the day, far more likely like early morning, late evening. Well, sorry, late afternoon, not quite evening. So usually in the middle part of the house, I would think you would have this problem. So what you can do to let more light in is install a skylight and that'll save you on running light bulbs in that period on the electricity. Yeah. But there's two problems I have. First one is that a lot of people get a huge skylight and you can't shut it. So what if it's too bright in the middle of the day and you want to shut it? Well, a lot of people get skylights, you can't reach them to shut or they just aren't designed with a shutting mechanism and then it gets too damn hot. Yeah, it's a big it brings a lot of heat in during the summer and it's a big heat leak in the winter. That's right. And that's exactly what I want to explore. So skylights also admit heat and they lose heat just like a window. So it's a trade off. And I love those. I love talking about them. So does the electricity cost saving of adding more light to that room outweigh the additional heating or cooling costs? So I let's run some numbers. 14 inch solar tube that I found a website has a UW of 0.43 with a cross sectional area of 154 square inches, which is point one of a square meter. So, you know, not huge, but still a reasonable size for a solar tube. And that same temperature differential of 15 degrees only results in 0.7 of a watt because it's so small. Yeah. OK. But it produces 6,500 lumens. That's at maximum, but what we're going to do is we're going to say, OK, that's We're not in the middle of the day. We're gonna assume about half that 'cause we're gonna be operating this. Our test case is the fringe times of day when there's less sunlight, which is when it's going to be most useful because otherwise, it's on, that's great. But we would have otherwise been using the light not during the daytime, but only on the fringe hours. So we'll have that number to about 3000 lumens. Now that works out to, if we're talking about an incandescent light bulb, about 250 watts worth of electricity. Now, no one uses incandescents anymore because incandescents suck. So we switch to an LED just like a good boy. And it's only consuming 25 watts from a good LED for that amount of light intensity, which mind you as LED bulbs goes is actually quite bright. You know, for example, my LIFX bulb, it's 18 watts and that's super bright at maximum. now 25 watts is even more. Anyway, so all of these numbers that I'm just running now, all that assumes that there's no thermal loss in the tubing, there's no, the roof cavity is, has been well insulated from the solar tube itself such that you don't get any heat losses there, but even if we do assume we lose say 10 watts of heat into the roof space, we are still well ahead of that 25 watts for lighting that room. Way ahead. 0.7 watts, hard to beat that. So ultimately, yes, it does make sense, which is one of the reasons why you should consider them. But of course, there's other little downsides. You're going to make sure they're well sealed on both sides to prevent them leaking, because that's not fun. You've voluntarily punched a hole in your otherwise not leaking roof. Well, I mean, I say not leaking roof, I presume your roof is not already leaking when you install the solar tube or skylight. But anyway. All right. So there you go. Hopefully that's answered that question for anyone that had it. Now, a lot of this talk about heat loss and, you know, and so on with insulation, it can all be rendered useless if you leave every single window and door open, then the air flowing through the house will predominantly set the temperature. So it's more about in the winter time when things are cold and everything's all shut up and you're heating the house or in the summertime when it's so hot you're trying to keep the heat out, you got all the windows closed and you're trying to keep the air conditioning in. You know, anyway. But ultimately, you're far better stopping the energy loss at the point of use rather than trying to add more heating or cooling capacity at the input. So let's just say I have no insulation in my roof, none on my walls. I've got, you know, no, none anywhere. And my entire the entire room is covered in skylights. It's one big skylight. You know, so you got this huge heat loss. Well, you know, you can cool that down. It's going to take a 10 kilowatt inverter air conditioner. But that's not very efficient. So what you want to do is you want to add insulation, add double glazing, you know, add your suspended floor with insulation in it if you do all those things you might be able to get away with a 5kW or 4kW or 3kW cooling unit and that's where you're saving your energy so you're far better off doing the insulation because that will cost you less and that will save you money in the long term and if I had to prioritize them in terms of cost and ease I would start with sealing insulation first as your biggest bang for buck then double glazing on the windows or insulated frames or both, hopefully. Wall insulation, I would suggest would be next. And then floor insulation would be last. Irrespective of how you slice it, and I've said that before, I'll say it again, is that it depends on the house that you've got. Some houses will have some, you know, like for example, my house, we have no insulation in our wall cavities, but we do in the roof. You know, and that was a conscious decision that we made. be made, but then we have one wall-mounted air conditioner in the whole house. We don't have central air conditioner, we don't have central heating. So, you know, in many respects, it doesn't matter as much. Yeah. Anyway. All right. Last little bit, I'm just going to sprinkle on and then we're going to wrap it up, and that is I want to talk a little bit about appliances. So this is all about energy efficiency. This is all about thinking about being greener and things that you can do to save energy. Well, here's the thing. There's a bunch of little real silly things and I'm just going to rattle them off one by one. Here we go. When you buy an appliance, think about the following things. If it's going to be running continuously or for long periods of time or regularly enough, you know that it's on regularly, then pick an appliance whose power is as small as possible for the task you need it to do. Don't get hung up on other features, just get one that doesn't consume a lot of power. And a lot of these things have got ENERGY STAR ratings or EPA ratings and these ratings are designed to help you understand and some of them even have the actual kilowatt hour rating written on the front of them. If you're getting a TV, do you really need a ridiculously huge TV set? You probably don't. You know, do you really need it because that's going to cost you a lot of electricity to run a big TV. few inches of that TV that you get that's bigger, it's more and more electricity, it's going to cost the driver. Do you really need it? Do you really need ducted air conditioning? You know, if you've got 10 kilowatts of cooling load, you know, you can forget ever disconnecting from the power grid, you know, no solar, you know, you're going to have an enormous solar array and battery packs if you want to go off the grid at some point and be, even be energy neutral, you know, good luck with that. So, do you really need ducted air conditioning or fans good enough. Speaking of fans, fans are far more efficient than air conditioning anyway, and they take advantage of evaporative cooling that our body uses, you know, through forced air evaporative cooling. And it works fine. Well, it works relatively well, until you get stupidly hot or it's ridiculously high humidity. That's the problem here, where there's humidity. Exactly. Get a frost free freezer. And I say that not because I hate defrosting them and the ice builds up on the coils, no. When ice builds up on the coils, it kills the efficiency. It makes it work harder because ice as it forms becomes an insulator which then means that the cooling action of the gas inside the freezer is actually reduced because all all it's doing is it's keeping the ice cold rather than the contents of the freezer cold. Yeah, so you've got to de-ice those things regularly, otherwise, you know, you will have a much reduced efficiency. Next one, and if you get frost free, you never have to worry about it. I guess you can get a freezer that's not frost free so long as you defrost it regularly. Which, of course, no one does. They're like, oh, does the door shut? No, the ice is in the way. Right, time to defrost it. By which time it's been running inefficiently for months. All right, when you're getting a light bulb, get the longest lasting LED light bulbs you can get and think about the lighting level you actually need for the whatever the minimum activity is in that room. You don't need an 80 watts worth of incandescent light in your room. You just don't. If you're working in a study, different story. And besides which, even if you are, get an LED desk lamp. you know, lower power, focused, you can focus in on the keyboard, if you're writing on a book, whatever. You know, far more efficient than getting a high powered LED bulb in the ceiling. So be realistic about how much you actually need. Don't leave the fridge or freezer door open for too long. OK, that's an obvious one. And if you're going to heat or air condition, you know, a room at a time, close the door. Don't leave it open. Is that obvious? I think it's obvious, isn't it? Surely To most people, I guess Because I mean, I've walked into these houses, you know how open plan was a thing there for a while? It's like, hey, open plan, you're not confined, it's awesome Or something. I don't know what the-- I don't get the attraction of open plan houses, but anyway So, and then I'll have an air conditioner up on one wall, this enormous area And you're looking at the air conditioner and I'm doing the math in my head As you do, you walk into a building and the first thing I think is, I don't know who BTUs there are That's British thermal units. Anyway, all right, good, lovely. Did you have any you wanted to add to that list? Because that's my list. No, I think you covered everything I would have thought of. Oh, OK. So we're doing that again. Sorry. Yeah, well, you should. I don't know. You're thorough, John, what can I say? Yeah, I guess so. That's one potential explanation, I guess. Okay, so I might wrap it up there now. So, if you want to talk more about this, you can reach me on Twitter @john2g and check out my writing at If you'd like to get in touch with Vic, he can be reached on Twitter @vichudson1. If you'd like to send any feedback, please use the feedback form on the website. That's where you'll also find the show notes of this episode on the podcasts Pragmatic. If there are topics you would like me to cover, you can suggest and vote on them at Once you sign up for free account at You can follow Pragmatic Show on Twitter to see show announcements and other related stuff like when we're broadcasting live if you want to join in and we hope you do. A final thank you to our sponsors for this episode. Firstly, Igloo, an intranet you'll actually like built with easy to use apps like file sharing, blogs, calendars, task management and more. Make sure you visit the URL to get started. It's free to use for up to 10 people, no credit card required. Just sign up and start playing today. And also, for sponsoring Pragmatic. If there's anything you'd like to learn about and you're looking for an easy and affordable way to learn, then can help you out. 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Vic Hudson

Vic Hudson

Vic is the host of the App Story Podcast and is the developer behind Money Pilot for iOS.

John Chidgey

John Chidgey

John is an Electrical, Instrumentation and Control Systems Engineer, software developer, podcaster, vocal actor and runs TechDistortion and the Engineered Network. John is a Chartered Professional Engineer in both Electrical Engineering and Information, Telecommunications and Electronics Engineering (ITEE) and a semi-regular conference speaker.

John has produced and appeared on many podcasts including Pragmatic and Causality and is available for hire for Vocal Acting or advertising. He has experience and interest in HMI Design, Alarm Management, Cyber-security and Root Cause Analysis.

Described as the David Attenborough of disasters, and a Dreamy Narrator with Great Pipes by the Podfather Adam Curry.

You can find him on the Fediverse and on Twitter.