Heat your house with a mechanical windmill (2019)(solar.lowtechmagazine.com)
solar.lowtechmagazine.com
Heat your house with a mechanical windmill (2019)
https://solar.lowtechmagazine.com/2019/02/heat-your-house-with-a-mechanical-windmill/
136 comments
> Combine a solar panel or a wind turbine with a heat pump
Two studies did that and mechanical heat pumps win. Here’s the links from the blog post:
https://elib.dlr.de/103317/1/20160224%20-%20Master%20Thesis_...
https://www.sciencedirect.com/science/article/pii/S096014811...
Two studies did that and mechanical heat pumps win. Here’s the links from the blog post:
https://elib.dlr.de/103317/1/20160224%20-%20Master%20Thesis_...
https://www.sciencedirect.com/science/article/pii/S096014811...
You're talking past each other.
He responded to a statement in the article comparing solar thermal collection with solar + heat pump.
The article mostly talks about mechanical heat pumps, and you leapt to that, talking past him.
(I think both the article and him are not strictly correct: solar thermal heating has a place but is not typically a efficiency win).
He responded to a statement in the article comparing solar thermal collection with solar + heat pump.
The article mostly talks about mechanical heat pumps, and you leapt to that, talking past him.
(I think both the article and him are not strictly correct: solar thermal heating has a place but is not typically a efficiency win).
The place for solar thermal is probably ease of maintenance. No moving parts means a lot less to go wrong, and a lot cheaper/easier to fix if something does go wrong.
That said, better house design gets you pretty much all the way there, and in places where you cannot design a house to get enough sun to heat it properly you also probably can't get enough for a solar collector to help much.
That said, better house design gets you pretty much all the way there, and in places where you cannot design a house to get enough sun to heat it properly you also probably can't get enough for a solar collector to help much.
> The place for solar thermal is probably ease of maintenance.
Can vouch for this. We've gone through three water heaters and a bunch of maintenance on those, and in the same time the solar collector has been replaced zero times and required no maintenance. It's honestly quite impressive.
Can vouch for this. We've gone through three water heaters and a bunch of maintenance on those, and in the same time the solar collector has been replaced zero times and required no maintenance. It's honestly quite impressive.
I could see it being useful in a remote living / off grid scenario as well, especially if you made it yourself out of recycled car parts and scrap.
Can you share the brand and tech ?
Tech: evacuated solar tubes
Brand: Apricus
I heavily vouch for them - the tech is so effective we cover them with a shadecloth in high Summer because the water gets too hot (Off-Grid property in Central West NSW, Australia).
Ours have lasted over 10 yrs without maintenance.
One downside is that they're not ubiquitous so some plumbers may not want to work with them.
They're so good I'm surprised I don't see them everywhere.
I heavily vouch for them - the tech is so effective we cover them with a shadecloth in high Summer because the water gets too hot (Off-Grid property in Central West NSW, Australia).
Ours have lasted over 10 yrs without maintenance.
One downside is that they're not ubiquitous so some plumbers may not want to work with them.
They're so good I'm surprised I don't see them everywhere.
Solar thermal is also great for e.g. heating pools.
For wind sure, but is that true for solar? Solar panels are max 20% efficient and head pumps typically have a COP of 2-3, so solar thermal only has to have an efficiency of around 50%. 1 second googling tells me it is 70%.
I think the real reason nobody does solar thermal is because it's just so much less practical to deal with pipes and pumps and heat reservoirs than wires and batteries. Also it is useless in the summer when you don't need heating.
Wind is always going to be niche for most people for obvious reasons.
I think the real reason nobody does solar thermal is because it's just so much less practical to deal with pipes and pumps and heat reservoirs than wires and batteries. Also it is useless in the summer when you don't need heating.
Wind is always going to be niche for most people for obvious reasons.
> I think the real reason nobody does solar thermal is because it's just so much less practical to deal with pipes and pumps and heat reservoirs than wires and batteries.
It very much depends where one is located. My parents' house, in a subtropical climate region, has had solar thermal for over 2 decades. Now they've also installed PV panels, but hot water is still mainly solar thermal with electrical heating as supplement.
New houses also have dual setups like theirs. Solar thermal collectors for hot water + PV for other electric usage and selling the excess to the grid.
> Also it is useless in the summer when you don't need heating.
You still do need some water heating in the summer.
It very much depends where one is located. My parents' house, in a subtropical climate region, has had solar thermal for over 2 decades. Now they've also installed PV panels, but hot water is still mainly solar thermal with electrical heating as supplement.
New houses also have dual setups like theirs. Solar thermal collectors for hot water + PV for other electric usage and selling the excess to the grid.
> Also it is useless in the summer when you don't need heating.
You still do need some water heating in the summer.
Growing up in the north east, my parents had a solar pool heater (they still do), Heating a pool via thermal collectors meant that we could reasonably use the pool through the end of September / early October some years, and it wouldn't be freezing cold on hot days in June before the water had a chance to warm up naturally.
It also had the side effect of keeping the heat off our roof and would actively pull heat out of the attic. PV panels would have worked with a heat pump but probably would have cost a ton more for the required capacity needed. Not to mention the extra heat on the roof from not having it watercooled.
It also had the side effect of keeping the heat off our roof and would actively pull heat out of the attic. PV panels would have worked with a heat pump but probably would have cost a ton more for the required capacity needed. Not to mention the extra heat on the roof from not having it watercooled.
Is that more or less efficient than a heat pump water heater driven by solar though? A quick search shows that the heat pump option can be upwards of 3x more efficient. Plus, you can use the extra electricity generated to power your fans or heat pump cooling system.
It's just coming out of winter here in Perth, Western Australia. I have 6.6kw solar power and also a 15 year old solar hot water system with thermostat controlled electric booster (so not ancient, but also not the most advanced tech). On cold and cloudy days the booster turns on and draws far more power than my panels are generating at that moment, but even on nice days it turns on over night when there is no solar power. I saw on one particularly bad day that it turned on 3 times in 24h - 2x when dark - and drew over 1.5kWh each time, and I only used the hot water once in the morning. So I turned the booster off a month or 2 ago (can't remember when exactly, but yes it meant some days I couldn't have a hot shower), and on my recent 2-month power bill I had used 215kWh less than last year! (I also replaced my plasma TV with an OLED in that time, so that might have been responsible for a portion.) So whilst I get free hot water for ~8 months of the year, the other 4 months it uses a ton of electricity.
My sister recently got a new hot water system and I showed her some data that showed heat pump ones were better, so that's what she got. The data showed that whilst they use electricity during the summer, they use less during winter, and they end up ahead. But actually we can see on her power bill that when it kicks in on bad days, it too can overwhelm her solar generation at that moment.
Ultimately I think we need smarter connected systems to get the best efficiency. The booster in my solar hot water is just a basic element like a kettle. Surely it could be "throttled" (supplied with less watts) or cycled during the day so that it only heats when there is solar power available? If I have to have a slightly-cooler-than-hot shower first thing in the morning because I didn't want it boosting at 4am, then so be it.
My sister recently got a new hot water system and I showed her some data that showed heat pump ones were better, so that's what she got. The data showed that whilst they use electricity during the summer, they use less during winter, and they end up ahead. But actually we can see on her power bill that when it kicks in on bad days, it too can overwhelm her solar generation at that moment.
Ultimately I think we need smarter connected systems to get the best efficiency. The booster in my solar hot water is just a basic element like a kettle. Surely it could be "throttled" (supplied with less watts) or cycled during the day so that it only heats when there is solar power available? If I have to have a slightly-cooler-than-hot shower first thing in the morning because I didn't want it boosting at 4am, then so be it.
I worked on solar thermal for a while. It was even mandatory to install in new buildings in my country for a while (before all solar was forbidden for personal use until recently, don't ask, I hated it too. Forced me to become a sysadmin though, which was a good move).
You can get pretty good efficiency with solar thermal panels and indeed they are more near the 70% mark. Just a "black paint" panel can get "decent" results and it's relatively cheap. I remember back in the training days, our teacher just held a metal pane, painted black, into the sun for a demonstration. And got to 80ºC in a few minutes. In January.
They are not so useless in summer depending on where you live. In my region, despite being tropical-tier hot, water comes out really cold from the urban lines, so you always need to use some gas for a heater (butane or city gas). Having a solar thermal setup completely nullifies that (admittedly not large, but existing) expense during summer and reduces it during winter. Since many buildings here already have it as a feature, it's a little expense reduction which is always welcomed.
I miss working on that field.
You can get pretty good efficiency with solar thermal panels and indeed they are more near the 70% mark. Just a "black paint" panel can get "decent" results and it's relatively cheap. I remember back in the training days, our teacher just held a metal pane, painted black, into the sun for a demonstration. And got to 80ºC in a few minutes. In January.
They are not so useless in summer depending on where you live. In my region, despite being tropical-tier hot, water comes out really cold from the urban lines, so you always need to use some gas for a heater (butane or city gas). Having a solar thermal setup completely nullifies that (admittedly not large, but existing) expense during summer and reduces it during winter. Since many buildings here already have it as a feature, it's a little expense reduction which is always welcomed.
I miss working on that field.
> I remember back in the training days, our teacher just held a metal pane, painted black, into the sun for a demonstration. And got to 80ºC in a few minutes. In January.
A bit off topic and slightly different tech, but I have a solar kettle which uses reflected sunlight and boils a liter of water in a bit over an hour.
The sun has energy to spare, and I always like learning new was to utilize it.
A bit off topic and slightly different tech, but I have a solar kettle which uses reflected sunlight and boils a liter of water in a bit over an hour.
The sun has energy to spare, and I always like learning new was to utilize it.
Isn't there some way to generate electricity from temperature differential? It seems like solar thermal and ground source water could be an avenue for that.
My undergrad thesis was about modeling a home-sized solar-thermal to electricity setup. The answer was (1) you could barely eek out something of value if you really tried (2) it would be beaten by solar panels hands down.
The problem is that electricity production is dependent on the difference in temperature between your hot liquid and the environment. And the 70C-30C with water you will get in the summer is simply not enough to produce much. Realistically, you need ten times this difference to do anything useful.
The other option is to heat oil, with lower heat capacity. That you could heat to a bit higher temperatures, but then you are going to continuously lose oil that has to be topped up.
Unfortunately, despite my dreams, such systems seem economically unrealistic.
The problem is that electricity production is dependent on the difference in temperature between your hot liquid and the environment. And the 70C-30C with water you will get in the summer is simply not enough to produce much. Realistically, you need ten times this difference to do anything useful.
The other option is to heat oil, with lower heat capacity. That you could heat to a bit higher temperatures, but then you are going to continuously lose oil that has to be topped up.
Unfortunately, despite my dreams, such systems seem economically unrealistic.
Which country banned solar for personal use?
Spain?
https://www.pv-magazine.com/2015/10/09/spains-government-app...
The tax was repealed in 2019, but still.
https://www.pv-magazine.com/2015/10/09/spains-government-app...
The tax was repealed in 2019, but still.
I have seen these turbines within city limits (in NZ): https://www.powerhousewind.co.nz/thinair-wind-turbine/ apparently they make a lot less noise. I'm sure some intelligent people will keep iterating on these technologies.
They do an awesome solar+wind deal too: https://www.powerhousewind.co.nz/powercrate/
They do an awesome solar+wind deal too: https://www.powerhousewind.co.nz/powercrate/
Having a black water tank on the roof for solar heated warm water is not uncommon in southern Europe.
Most camping showers work by the same principle. If you need warm water and you have enough sunlight to warm it when you need it, this is not a bad idea
Most camping showers work by the same principle. If you need warm water and you have enough sunlight to warm it when you need it, this is not a bad idea
I misread that as "(black water) tank" and got worried.
> I think the real reason nobody does solar thermal is because it's just so much less practical to deal with pipes and pumps and heat reservoirs than wires and batteries. Also it is useless in the summer when you don't need heating.
I am not sure this is true for all use cases and locations. In Spain it is mandatory since 2006 to install solar thermal panels in new buildings [1], it simply preheats water, in this case this seems way simpler than any electrical installation and you already have an energy gain. Hot water is used all year round and Spain has a good amount of sunny days.
[1] https://www.nbcnews.com/id/wbna15698812
I am not sure this is true for all use cases and locations. In Spain it is mandatory since 2006 to install solar thermal panels in new buildings [1], it simply preheats water, in this case this seems way simpler than any electrical installation and you already have an energy gain. Hot water is used all year round and Spain has a good amount of sunny days.
[1] https://www.nbcnews.com/id/wbna15698812
A friend is thinking of remodel and add solar thermal to heat basement, garage in-floor heat, and another loop for driveway snow melt. The place is well above a mile high. At first thought, it seems very practical during remodeling.
A long 1" black pipe on the roof can provide plenty of hot water in summer for showers.
By the way, pipes are one of those things that are both metric and imperial in metric countries. We have two different series of pipes here in Italy, one with 1/2, 5/8, 1, 1 1/4 inches and one in millimeters. Gardening leans toward inches and those sturdy black plastic pipes are at least 1".
By the way, pipes are one of those things that are both metric and imperial in metric countries. We have two different series of pipes here in Italy, one with 1/2, 5/8, 1, 1 1/4 inches and one in millimeters. Gardening leans toward inches and those sturdy black plastic pipes are at least 1".
The UK does this a lot: items sold with the size marked in metric, as required, but rounded to an _imperial_ size. So you get 6.3mm drill bits and 454g bags of flour.
> I think the real reason nobody does solar thermal is...
You have a weird definition of nobody. They are not as popular these days but do exist and are very useful. Don't even that much sun to produce warm water
You have a weird definition of nobody. They are not as popular these days but do exist and are very useful. Don't even that much sun to produce warm water
> 1 second googling tells me it is 70%.
... at full sun visibility, that is. However, in winter where it's cloudy, raining or, worse, there's snowpack on the panel? Now it's at 0%, right when you actually need it the most.
So you have to have the solar heating system and a fallback for winter/night, and the headaches of all that extra pipework just don't make it worth the effort because all you're going to get from it is a few hot showers during summer.
... at full sun visibility, that is. However, in winter where it's cloudy, raining or, worse, there's snowpack on the panel? Now it's at 0%, right when you actually need it the most.
So you have to have the solar heating system and a fallback for winter/night, and the headaches of all that extra pipework just don't make it worth the effort because all you're going to get from it is a few hot showers during summer.
Solar thermal still works with clouds and under light snow, you might be thinking of concentrated solar but that’s a different story.
Also, storing a few hundred kWh of heat in a hot water tank is vastly cheaper than batteries. The real advantage of solar thermal is it can scale so well, thus allowing the benefit of a heated pool and later driveway without extreme expense. An expanded mindset around heat being so cheap means you can do things like warm an exterior patio for chilly fall days etc etc.
Also, storing a few hundred kWh of heat in a hot water tank is vastly cheaper than batteries. The real advantage of solar thermal is it can scale so well, thus allowing the benefit of a heated pool and later driveway without extreme expense. An expanded mindset around heat being so cheap means you can do things like warm an exterior patio for chilly fall days etc etc.
> and later driveway
Just mix in nuclear waste with the concrete. It'll keep the driveway free of ice, and illuminated after dark.
Just mix in nuclear waste with the concrete. It'll keep the driveway free of ice, and illuminated after dark.
Florida is trying... though not enough to heat. https://www.npr.org/2023/05/09/1174789570/florida-roads-radi...
And if it's enough to keep the snow away... I want to stay way away from it.
The Radiological Incident in Lia, Georgia https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1660web-81... . I will warn that reading Section 5 is NSFL if you know what you're reading. Section 6 is NSFL with pictures that will make clear what section 5 was about.
> On a cold day of 2 December 2001, three inhabitants of Lia (later designated as Patients 1-DN, 2-MG and 3-MB) drove their truck approximately 45–50 km east of Lia to collect firewood. At around 18:00, they found two containers — metallic, cylindrical objects — lying on a forest path. Around them, the snow had curiously thawed within a radius of approximately 1 m, and the wet soil was steaming. All three individuals stated that the two, rather heavy, cylindrical objects (8–10 kg, 10 cm × 15 cm) were found by chance while carrying out their usual task of collecting firewood.
> One of the three men (Patient 3-MB) picked up one of the cylindrical objects and, finding that it was hot, dropped it immediately. They planned to place the gathered wood in their truck the next morning, and because it was getting dark, they decided to spend the night in the forest, using the hot objects they had discovered as personal heaters.
> ...
> The three individuals warmed themselves during the night using the open fire on one side, sitting and lying around it, and not far from the hot cylindrical objects, which they placed at a distance of up to 1 m behind their backs.
And if it's enough to keep the snow away... I want to stay way away from it.
The Radiological Incident in Lia, Georgia https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1660web-81... . I will warn that reading Section 5 is NSFL if you know what you're reading. Section 6 is NSFL with pictures that will make clear what section 5 was about.
> On a cold day of 2 December 2001, three inhabitants of Lia (later designated as Patients 1-DN, 2-MG and 3-MB) drove their truck approximately 45–50 km east of Lia to collect firewood. At around 18:00, they found two containers — metallic, cylindrical objects — lying on a forest path. Around them, the snow had curiously thawed within a radius of approximately 1 m, and the wet soil was steaming. All three individuals stated that the two, rather heavy, cylindrical objects (8–10 kg, 10 cm × 15 cm) were found by chance while carrying out their usual task of collecting firewood.
> One of the three men (Patient 3-MB) picked up one of the cylindrical objects and, finding that it was hot, dropped it immediately. They planned to place the gathered wood in their truck the next morning, and because it was getting dark, they decided to spend the night in the forest, using the hot objects they had discovered as personal heaters.
> ...
> The three individuals warmed themselves during the night using the open fire on one side, sitting and lying around it, and not far from the hot cylindrical objects, which they placed at a distance of up to 1 m behind their backs.
For a long time I have had this idea of finding a radioactive decay chain that produces mostly alpha particles, then encapsulating it fully in an inert pill. My thought is that you could swallow these pills when climbing Everest, and these pills would just provide a little bit of heat continually, reducing calorie requirements on the mountain, and reducing a little of the strain on your body from having to produce that heat.
I don't know if this is feasible at all, but the idea keeps coming back to me.
I don't know if this is feasible at all, but the idea keeps coming back to me.
No... Alpha would be especially bad.
Radiation and the Cookie Test - https://letstalkaboutscience.wordpress.com/2013/03/15/radiat...
> So if we are concerned about radiation safety, how do we treat different sources of ionizing radiation? The cleverest way I’ve heard it summed up is by the ‘cookie test’: imagine that you have four cookies. One is an alpha emitter, one is a beta emitter, one is a gamma emitter, and one is a neutron emitter. You can throw one cookie away, but you have to put one in your pocket, hold one in your hand, and eat one. How do you pick which cookies to do what with?
And for a real world case: https://en.wikipedia.org/wiki/Poisoning_of_Alexander_Litvine...
> Unlike most common radiation sources, polonium-210 emits very little gamma radiation (the low-intensity gamma ray at an energy of 803 keV is the most prominent), but large amounts of alpha particles which do not penetrate even a sheet of paper or the epidermis of human skin, and is therefore relatively invisible to common radiation detectors such as Geiger counters. This explained why tests conducted by doctors and Scotland Yard at the hospital with Geiger counters were negative. Both gamma rays and alpha particles are classified as ionizing radiation, which can cause radiation damage. An alpha-emitting substance can cause significant damage only if ingested or inhaled, acting on living cells like a short-range weapon. Hours before his death, Litvinenko was tested for alpha-emitters using special equipment.
Radiation and the Cookie Test - https://letstalkaboutscience.wordpress.com/2013/03/15/radiat...
> So if we are concerned about radiation safety, how do we treat different sources of ionizing radiation? The cleverest way I’ve heard it summed up is by the ‘cookie test’: imagine that you have four cookies. One is an alpha emitter, one is a beta emitter, one is a gamma emitter, and one is a neutron emitter. You can throw one cookie away, but you have to put one in your pocket, hold one in your hand, and eat one. How do you pick which cookies to do what with?
And for a real world case: https://en.wikipedia.org/wiki/Poisoning_of_Alexander_Litvine...
> Unlike most common radiation sources, polonium-210 emits very little gamma radiation (the low-intensity gamma ray at an energy of 803 keV is the most prominent), but large amounts of alpha particles which do not penetrate even a sheet of paper or the epidermis of human skin, and is therefore relatively invisible to common radiation detectors such as Geiger counters. This explained why tests conducted by doctors and Scotland Yard at the hospital with Geiger counters were negative. Both gamma rays and alpha particles are classified as ionizing radiation, which can cause radiation damage. An alpha-emitting substance can cause significant damage only if ingested or inhaled, acting on living cells like a short-range weapon. Hours before his death, Litvinenko was tested for alpha-emitters using special equipment.
The whole point is that if it's securely contained the alphas wouldn't penetrate the shielding around it. As long as that shielding is intact you're not getting any radiation dose.
A cookie would be bad because you're actually digesting it.
Beta or gammas are harder to shield.
A cookie would be bad because you're actually digesting it.
Beta or gammas are harder to shield.
Horrible.
(Un)fortunately we don't make enough of such waste to be able to do it at scale (even a city scale).
Being from a ridiculously rainy region and having worked on solar thermal, I can warrant you that while it's not as functional when in bad conditions, it still works.
Consider it's usually set as a setup combined with a standard heating system (gas, electric...), and while there are situations where it can't handle the full load (absolutely horrible darker than night days) it'll always reduce or nullify costs. And since installation and maintenance are relatively cheap, it's always going to save you some money on the long run.
Also consider some areas can be really hot, but have very cold water lines. I need to heat my water in summer despite being above 40ºC outside. Having solar negates that cost entirely, giving you like 9 months where you spend nothing in water heating. Considering how expensive gas/electric has become in this country, it's quite the relief for a wallet.
Consider it's usually set as a setup combined with a standard heating system (gas, electric...), and while there are situations where it can't handle the full load (absolutely horrible darker than night days) it'll always reduce or nullify costs. And since installation and maintenance are relatively cheap, it's always going to save you some money on the long run.
Also consider some areas can be really hot, but have very cold water lines. I need to heat my water in summer despite being above 40ºC outside. Having solar negates that cost entirely, giving you like 9 months where you spend nothing in water heating. Considering how expensive gas/electric has become in this country, it's quite the relief for a wallet.
> However, in winter where it's cloudy, raining or, worse, there's snowpack on the panel? Now it's at 0%, right when you actually need it the most
If there's snowpacks on the panel during most of winter, then solar isn't for you, no matter what kind of solar we're talking about…
If there's snowpacks on the panel during most of winter, then solar isn't for you, no matter what kind of solar we're talking about…
Heat pumps are somewhat limited in the heat they can provide. For example, it would be difficult for a heat pump to produce several hundred degrees C temperatures for an industrial process.
For applications in their wheelhouse, though, they are absolutely amazing.
For applications in their wheelhouse, though, they are absolutely amazing.
There are a couple physical principles that work together to limit solar thermal collectors: heat flows from hot to cold, and mirrors and lenses work both ways. Together, they imply that a solar collector can't heat up anything hotter than the surface of the sun because if the target was hotter than the sun, it would heat the sun up and not the other way around. The surface of the sun is 5.7 thousand Kelvin. This is enough to melt, but not boil tungsten, which I must imagine is a major issue for the tungsten gas industry.
This is probably irrelevant, but due to the finite speed of light the target would be radiating to the place the sun was, rather than the place it will be.
But if you compress the energy collected on a large surface onto a small surface, getting higher heat should be possible, not?
No. [0]
Counter-intuitive for most people, but it cannot be done. The explanation is a mixture of heat flowing both ways, and a law called "conservation of étendue" (you cant focus light beams down as much as you'd think). The link explains the details much better than I could.
[0] https://what-if.xkcd.com/145/
Counter-intuitive for most people, but it cannot be done. The explanation is a mixture of heat flowing both ways, and a law called "conservation of étendue" (you cant focus light beams down as much as you'd think). The link explains the details much better than I could.
[0] https://what-if.xkcd.com/145/
That only talks about lenses and optics.
I'm still convinced the electrical energy collected on a few acres of solar panels fields, could be used to heat a small piece of metal hotter than the surface of the sun. Or am I understanding this problem entirely wrong?
I mean, I do understand why a large array of mirrors and/or lenses won't heat a surface up more than the source. But if we convert and then "upgrade" it (probably with a lot of efficiency loss) i'd think it possible.
And if we collect over time and store that (e.g. as hydrogen, or in batteries) I'm pretty sure we can get it even hotter.
I'm still convinced the electrical energy collected on a few acres of solar panels fields, could be used to heat a small piece of metal hotter than the surface of the sun. Or am I understanding this problem entirely wrong?
I mean, I do understand why a large array of mirrors and/or lenses won't heat a surface up more than the source. But if we convert and then "upgrade" it (probably with a lot of efficiency loss) i'd think it possible.
And if we collect over time and store that (e.g. as hydrogen, or in batteries) I'm pretty sure we can get it even hotter.
Oh, for sure. Using photovoltaic panels and electric heating, none of this applies.
But the comment you replied to initially talks about the limit of solar thermal collectors.
But the comment you replied to initially talks about the limit of solar thermal collectors.
[deleted]
The article brings this up towards the end,
"These [eddy current heaters/induction heaters] are comprised of a magnet mounted on a rotating shaft, and can reach temperatures of up to 600 degrees Celsius. Using eddy current heaters, windmills could provide direct heat at higher temperatures, making their potential use in industry even larger."
"These [eddy current heaters/induction heaters] are comprised of a magnet mounted on a rotating shaft, and can reach temperatures of up to 600 degrees Celsius. Using eddy current heaters, windmills could provide direct heat at higher temperatures, making their potential use in industry even larger."
There's plenty of research going into very high-temperature heat pumps. It's likely that eventually that will absolutely be 'in their wheelhouse'. Sure, the COP might only ever be something like 2-3 instead of lower temperature heat pumps (under 80 or so °C) that can be > 4 COP but still should be more than 1...
> but good luck getting a permit for windmills in anywhere else
Just because silly bureaucracy exists doesn't mean something is a bad idea.
Just because silly bureaucracy exists doesn't mean something is a bad idea.
OTOH, I can probably whip up a small windmill using the scrap wood I have laying around under my carport. I'll need to buy some parts for mechanisms / power transmission though...
> there's a reason these got virtually phased out!
Citation needed. In my country they sell very well nowadays so they don't look as they've been phased out at all. And for good reason IMHO: they are much more rustic than heat pumps and are likely going to live for much longer than the later with cheaper maintenance.
Also, as heat can be stored pretty efficiently (and cheaply) compared to electricity, the day/night intermittency isn't so big of a deal.
Citation needed. In my country they sell very well nowadays so they don't look as they've been phased out at all. And for good reason IMHO: they are much more rustic than heat pumps and are likely going to live for much longer than the later with cheaper maintenance.
Also, as heat can be stored pretty efficiently (and cheaply) compared to electricity, the day/night intermittency isn't so big of a deal.
For a winning combination, you can use combined thermal/solar panels and then drive a heat pump with the electricity on the pre-warmed water. But that adds complexity. The primary reason we use electricity as intermediary is that it’s comparatively easy to transport even for longer distances and can be used to drive almost any that needs energy - produce heat, cold, mechanical work, computers, …
I wonder how difficult it would be to engineer a direct wind powered heat pump. Theoretically, you could just mechanically drive the compressor and fans, and skip electricity generation.
(To be clear, I'm sure this would not make sense economically, but it would be really cool.)
(To be clear, I'm sure this would not make sense economically, but it would be really cool.)
Actually you don’t even need a mechanical compressor. If you know how a propane fridge works, they boil an Ammonia mixture until it becomes a gas, it‘s condensed back into a liquid, and voila, refrigeration.
With the right materials you could use thermal solar panels to build a silent air conditioner just as easily as a heater with no moving parts, in theory. Here's an old video on the principles behind it (https://www.youtube.com/watch?v=KDPgGDCdAo4).
With the right materials you could use thermal solar panels to build a silent air conditioner just as easily as a heater with no moving parts, in theory. Here's an old video on the principles behind it (https://www.youtube.com/watch?v=KDPgGDCdAo4).
Since I've heard about propane fridges I don't understand why we don't use such a thermal-solar AC everywhere. Like using the sun itself to cool you off without even needing moving parts sounds like the holy grail of AC, surely there must be engineering difficulties but what are those?
If you have really steady winds, sure. Otherwise you're probably going to need to smooth out the RPM with an intermediate stage like a flywheel.
> Combine a solar panel or a wind turbine with a heat pump and despite generation losses it will outperform any thermal collectors - there's a reason these got virtually phased out!
Please expand on this. I have no idea how these two compare in efficiency (but apparently you do).
Please expand on this. I have no idea how these two compare in efficiency (but apparently you do).
Thermal collectors, at best, can capture about 90% of the sun's energy. Practically speaking a bit less.
Solar panels, at their best, can capture about 25% of the sun's energy as electricity. There exist heat pumps with a coefficient of performance (COP) such that the system as a whole captures more heat i.e. COP >4
I'm not sure the claim is absolutely true universally, especially in challenging environments, but in a broad sense it is true that turning sunlight into electricity and then using that electricity to power a heat pump has a bunch of advantages over direct solar thermal, not least of which is air conditioning.
Solar panels, at their best, can capture about 25% of the sun's energy as electricity. There exist heat pumps with a coefficient of performance (COP) such that the system as a whole captures more heat i.e. COP >4
I'm not sure the claim is absolutely true universally, especially in challenging environments, but in a broad sense it is true that turning sunlight into electricity and then using that electricity to power a heat pump has a bunch of advantages over direct solar thermal, not least of which is air conditioning.
> Solar panels, at their best, can capture about 25% of the sun's energy as electricity. There exist heat pumps with a coefficient of performance (COP) such that the system as a whole captures more heat i.e. COP >4
Am I understanding it correct that the efficiency is, in this case (25%; COP >4), greater than 100%?
Am I understanding it correct that the efficiency is, in this case (25%; COP >4), greater than 100%?
Yes, because it is moving scavenged heat to where it is useful. So 1/4 of the energy comes from the electricity, the other 3/4 from ambient atmosphere.
Can't comment on a thermal collector, but if we look at efficiency of solar PV and heat pumps:
Solar PV panel: the best ones are up to about 22% efficiency. Heat pumps: again, top of the line approaches 400%
You can't just multiply those numbers, however, there's also losses when you invert DC to AC, but it might be a good starting point.
Solar PV panel: the best ones are up to about 22% efficiency. Heat pumps: again, top of the line approaches 400%
You can't just multiply those numbers, however, there's also losses when you invert DC to AC, but it might be a good starting point.
My key takeaway: GP is right, going PV+HP is a safe default; at least around here(!!).
Unless you don't get money for selling excess power to the grid (batteries have become massively cheaper though) AND you have a gigantic roof. Even then, it's probably worthwhile investing more into the PV instead of getting solar thermal.
Of course this also depends on latitude.
Anecdata 1: Thermal solar installation between 49 to 50deg latitutide, central europe. My uncle's SFH.
Anecdata 2: We're currently adding PV+HP with cooling capacity to our own SFH and I would have loved thermal solar to be great, so I looked into this. (same rough geographic location).
During summer his thermal solar has great efficiency, but the heat tanks are already charged after 1 to 2h (that's what he said when we talked about it last summer). So the installation has at most 2h of say 80% efficiency (during low solar radiation in the morning!) and then another 8h of 0% since the heat can go nowhere. This also wastes the huge energy peak after noon. This means: The ratio between a days "total energy harvested" vs "total energy which reached the collectors" is even less than the arithmetic average of 16% efficiency. Of course they use hot water over day, but that only increases the efficiency a little bit. Especially considering the physically huge tanks they have installed (probably 1000l ballpark, and I think there are two of these?!). Contrary in winter, the temperature differential between collector and fluid is so low that no heat/energy can be harvested at all. (At least for their installation and the winter temperatures around here).
Compare that to PV+HP: Any solar radiation is transformed to electricity with 22% efficiency. In summer the COP [see sibling comments] is very high, so you can still quickly charge that hot water tank and then use the remaining energy harvested for your home or car, or sell it to the grid. Plus the hot water tank can be smaller (less losses!) since you don't need to "store" all the excess energy. E.g. we have 200l hot water and 200l buffer for heating (or actually: Defrosting the HP). During winter the PV still produces some power that the HP can convert to heat (not too much and especially for less hours per day, but >0).
Maybe there are some sweet spots during spring and fall when solar thermal outperforms the PV+HP because it takes the whole day to charge the tanks. But then again when I installed my PV this spring, it produced >110% on a cool (16degC/60degF?), sunny day. So even during those seasons PV+HP are a tough competition.
Nice bonus for the PV+HP (that's what we're doing): If it's too hot in the summer, you can use the excess electricity to drive the HP in reverse mode for 7degC/44degF water temp in the "heating" system for active cooling. Due to condensation this requires dampproof insulation for the pipes, and convector units (sometimes also called "fan coils"?) to move enough air through the heat exchanger (car-like radiator) instead of traditional radiators or floor heating. But every convector can sink 1500W (5100 BTU?); for a room in a well-insulated house this can be enough.
Mind that our roof (south east + north west) has merely 60sqm per half, minus windows and other installations, so there is not too much space to add thermal solar. We get 0.07€ per kWh sold to the grid, so the excess PV mostly pays for itself. Battery is 11kWh usable, based on budget not "what we need" (data wasn't sufficient because we did all the renovations at once); this improves how much we can consume ourself; was more worthwhile than adding hot water tanks (we just can't consume that much hot water every day). We're also adding massive insulation to the 70y old house to slash heating requirements from >40MWh/y to something more sensible.
Anecdata 1: Thermal solar installation between 49 to 50deg latitutide, central europe. My uncle's SFH.
Anecdata 2: We're currently adding PV+HP with cooling capacity to our own SFH and I would have loved thermal solar to be great, so I looked into this. (same rough geographic location).
During summer his thermal solar has great efficiency, but the heat tanks are already charged after 1 to 2h (that's what he said when we talked about it last summer). So the installation has at most 2h of say 80% efficiency (during low solar radiation in the morning!) and then another 8h of 0% since the heat can go nowhere. This also wastes the huge energy peak after noon. This means: The ratio between a days "total energy harvested" vs "total energy which reached the collectors" is even less than the arithmetic average of 16% efficiency. Of course they use hot water over day, but that only increases the efficiency a little bit. Especially considering the physically huge tanks they have installed (probably 1000l ballpark, and I think there are two of these?!). Contrary in winter, the temperature differential between collector and fluid is so low that no heat/energy can be harvested at all. (At least for their installation and the winter temperatures around here).
Compare that to PV+HP: Any solar radiation is transformed to electricity with 22% efficiency. In summer the COP [see sibling comments] is very high, so you can still quickly charge that hot water tank and then use the remaining energy harvested for your home or car, or sell it to the grid. Plus the hot water tank can be smaller (less losses!) since you don't need to "store" all the excess energy. E.g. we have 200l hot water and 200l buffer for heating (or actually: Defrosting the HP). During winter the PV still produces some power that the HP can convert to heat (not too much and especially for less hours per day, but >0).
Maybe there are some sweet spots during spring and fall when solar thermal outperforms the PV+HP because it takes the whole day to charge the tanks. But then again when I installed my PV this spring, it produced >110% on a cool (16degC/60degF?), sunny day. So even during those seasons PV+HP are a tough competition.
Nice bonus for the PV+HP (that's what we're doing): If it's too hot in the summer, you can use the excess electricity to drive the HP in reverse mode for 7degC/44degF water temp in the "heating" system for active cooling. Due to condensation this requires dampproof insulation for the pipes, and convector units (sometimes also called "fan coils"?) to move enough air through the heat exchanger (car-like radiator) instead of traditional radiators or floor heating. But every convector can sink 1500W (5100 BTU?); for a room in a well-insulated house this can be enough.
Mind that our roof (south east + north west) has merely 60sqm per half, minus windows and other installations, so there is not too much space to add thermal solar. We get 0.07€ per kWh sold to the grid, so the excess PV mostly pays for itself. Battery is 11kWh usable, based on budget not "what we need" (data wasn't sufficient because we did all the renovations at once); this improves how much we can consume ourself; was more worthwhile than adding hot water tanks (we just can't consume that much hot water every day). We're also adding massive insulation to the 70y old house to slash heating requirements from >40MWh/y to something more sensible.
but thermal collectors are a lot cheaper than heat pumps, thats also important to consider
> windmill can not only provide mechanical energy, but also thermal energy. The problem is that almost nobody knows this.
It can also provide A/C to cool a house then. The problem is that almost nobody knows this, except Einstein of course https://en.m.wikipedia.org/wiki/Einstein_refrigerator
It can also provide A/C to cool a house then. The problem is that almost nobody knows this, except Einstein of course https://en.m.wikipedia.org/wiki/Einstein_refrigerator
Boiling water through friction requires seals [1] , and rubber seals are pretty hard (not impossible) to make low tech.
The lowest tech solution IMHO is a squirrel cage generator and ohmic resistors. No magnets or fancy electronics are needed. Just remnant magnetization of soft iron and some copper wire/tube.
[1] a demo doesn't need seals, but a heating solution that will work for ten years will.
The lowest tech solution IMHO is a squirrel cage generator and ohmic resistors. No magnets or fancy electronics are needed. Just remnant magnetization of soft iron and some copper wire/tube.
[1] a demo doesn't need seals, but a heating solution that will work for ten years will.
> seals
Are they also required bellow boiling temp ? You probably don’t need much more than 55C at home. Increase the temp to store more energy and use a thermal expending socket to stop heat production before boiling temp.
> ohmic resistors
Isn’t it similar to the eddy current generator he talk about ? http://www.bulipi-eee.tuiasi.ro/archive/2013/fasc.4/p12_f4_2...
Are they also required bellow boiling temp ? You probably don’t need much more than 55C at home. Increase the temp to store more energy and use a thermal expending socket to stop heat production before boiling temp.
> ohmic resistors
Isn’t it similar to the eddy current generator he talk about ? http://www.bulipi-eee.tuiasi.ro/archive/2013/fasc.4/p12_f4_2...
If the water is not boiling you're going to need a very large system (for natural convection) or a pump.
Do the size of the system need to be that much larger for 95C compare to 100C ? In my understanding the post talk about methods that do not involve pressure. On top of that if you want more heat you may simply use a liquid switch higher boiling temp.
Yes because at 100C you can use phase change to transport water, which means you've built a primitive heat pipe.
At 95C H transport is slow so heat will accumulate until it reaches 100. But then you have boiling and, w/out good seals water loss.
At 95C H transport is slow so heat will accumulate until it reaches 100. But then you have boiling and, w/out good seals water loss.
We should be able to design the mixer fins and chamber such that it generates some pressure differential between the input and output ports.
> "A mechanical heat pump is simply a heat pump without the electric motor – instead, the wind rotor is directly connected to the compressor(s) of the heat pump. This involves one less energy conversion, which makes the combination at least 10% more energy efficient than an electric heat pump driven by a wind turbine."
Running a heat pump directly from a turbine is a really interesting idea, but they overlook the main benefit that heat pumps achieve well over 100% efficiency, if you're just measuring how many watts of energy it takes to produce some number of watts of heat.
A reasonable setup might be to have a heat pump with an input shaft and a differential; one end goes to an electric motor, and the other end goes to a windmill. (Or a water wheel, or some other convenient source of rotational energy.) You could run the heat pump off the windmill, or if you don't need any more heat, the windmill can run into the motor as a generator. If you need heat and the wind isn't blowing, you can run the heat pump off the motor.
That's probably a less practical setup than just using an electric generator windmill and an electric heat pump, but one could argue that's in some sense simpler or more elegant.
Running a heat pump directly from a turbine is a really interesting idea, but they overlook the main benefit that heat pumps achieve well over 100% efficiency, if you're just measuring how many watts of energy it takes to produce some number of watts of heat.
A reasonable setup might be to have a heat pump with an input shaft and a differential; one end goes to an electric motor, and the other end goes to a windmill. (Or a water wheel, or some other convenient source of rotational energy.) You could run the heat pump off the windmill, or if you don't need any more heat, the windmill can run into the motor as a generator. If you need heat and the wind isn't blowing, you can run the heat pump off the motor.
That's probably a less practical setup than just using an electric generator windmill and an electric heat pump, but one could argue that's in some sense simpler or more elegant.
I always enjoy the articles on this site.
I'd enjoy them a bit more if they didn't continually insinuate stuff about modern renewables that they clearly know not to be true due to the way they phrase it.
If people leave your article with misconceptions about modern renewables then that is a bad thing.
I'd enjoy them a bit more if they didn't continually insinuate stuff about modern renewables that they clearly know not to be true due to the way they phrase it.
If people leave your article with misconceptions about modern renewables then that is a bad thing.
> The Calorius type 37 – which had a rotor diameter of 5 meters and a height of 9 meters – produced 3.5 kilowatt of heat at a wind speed of 11 m/s (a strong breeze, Beaufort 6). This is comparable to the heat output of the smallest electric boilers for space heating
Well, there you have it of why it's a relatively unknown tech (that I also didn't know about). The heat produced is very small for a house yet the blade still needs to be very high, making it impractical on most houses. On top of that hot water transport on long distances is a recent thing due to advancement of pipe tech which made communal version of those impossible at the time.
Well, there you have it of why it's a relatively unknown tech (that I also didn't know about). The heat produced is very small for a house yet the blade still needs to be very high, making it impractical on most houses. On top of that hot water transport on long distances is a recent thing due to advancement of pipe tech which made communal version of those impossible at the time.
Wind is just not good at all scaling down, no clever trick on the every use side or I the side of blade geometry will ever change that.
Exactly this. In my local home energy generation group there are a lot of people thinking they are smart by getting wind generators from alibaba and then selling them because it’s really hard to get anything usable out of them.
Someone working in the field told that anything below mast height of 30m is going to a toy at best.
Someone working in the field told that anything below mast height of 30m is going to a toy at best.
How (im)practical would it be to directly drive the compressor of a heatpump by a source of mechanical energy?
For some reason I am almost expecting jacquesm to show up with some first-hand knowledge ;)
Edit: there is a section on this the end of the article.
For some reason I am almost expecting jacquesm to show up with some first-hand knowledge ;)
Edit: there is a section on this the end of the article.
You'd need a system with an open-drive compressor (like automotive A/C or very early fridges), and a rather high gear increasion, but it's certainly possible. Imagine something like this with the motor replaced by the windmill:
https://www.youtube.com/watch?v=ViO3Xky3nYE
https://www.youtube.com/watch?v=ViO3Xky3nYE
Aren’t the air conditioning units in cars usually belt driven?
I can imagine some post-apocalyptic scavenger rigging up an air-conditioning using using a windmill and car parts.
I can imagine some post-apocalyptic scavenger rigging up an air-conditioning using using a windmill and car parts.
If you prefer to go even lower tech, check out compost heating:
https://www.happysprout.com/outdoor-living/compost-heating-g...
Unless you have pigs fed with swill, you'll easily produce enough compost to survive the winter in warmth.
https://www.happysprout.com/outdoor-living/compost-heating-g...
Unless you have pigs fed with swill, you'll easily produce enough compost to survive the winter in warmth.
So many neat articles on that site - the obsolete section is particularly great.
https://solar.lowtechmagazine.com/obsolete-technology/
https://solar.lowtechmagazine.com/obsolete-technology/
That's pretty fascinating. I was looking at off grid setups in Canada, but the issue there is that peak energy usage is during winter, which is also the time of the year with the lowest illumination and snow on solar panels. Having the ability to generate heat that way would keep the more scarce electricity for other uses that cannot use heat or mechanical energy as inputs.
Or generate electricity to run a heat pump for 2 to 3 times more heat generated than what you get from frictional heating form a windmill.
This method has the drawback to loose energy (with heat!) to convert motion (windmill) to electricity, and then electricity back to motion (heat pump stator). This post talks about the idea of mechanical heat pumps to avoid those losses and cite two papers that back his claims.
We shall not be blind on the many avantages of electricity but on a pure efficiency scale converting motion to heat is a better idea than motion to (electricity and heat) to (motion and heat) to heat.
We shall not be blind on the many avantages of electricity but on a pure efficiency scale converting motion to heat is a better idea than motion to (electricity and heat) to (motion and heat) to heat.
Essentially, it's more efficient to generate heat directly from a windmill, than first turning it into electricity.
That being said, porque no los dose. Efficient heat is great, but you don't always need it. If you only use the electric generator a few months a year, it may still be worth it, given you're investing in a windmill.
That being said, porque no los dose. Efficient heat is great, but you don't always need it. If you only use the electric generator a few months a year, it may still be worth it, given you're investing in a windmill.
Given that a heat pump can be a lot more than 100% efficient, it's likely more efficient to generate electricity and then use a heat pump to heat the house.
The article has a long section on using the windmill to directly drive the compressor of a heat pump using a gearbox. This is likely to be more efficient than converting to electricity and then using that to run an electric compressor.
Air source heat pumps (in heating mode) use the heat generated by the electric compressor so the conversion loses there are negligible.
Mechanical gearboxes also generate heat, so you'd need to capture that too.
Mechanical gearboxes also generate heat, so you'd need to capture that too.
There's no reason you couldn't run the compressor of a heat pump mechanically. Then the question becomes is it more efficient to generate electricity to run a motor (or a linear compressor, I suppose), or use a gearbox to change the rotation speed. Plus or minus if you need mechanical air movement in the conditioned space.
Mechanical heat pumps are covered in the article. And for the child response to yours, mechanisms for sourcing heat for longer periods are also covered (e.g. 10k, 20k liter tanks of warm water, hydraulic oil vs water as primary heat transfer fluid)
The reason you don't want to do that is you need to store the energy for times when the wind isn't blowing.
Energy storage doesn't require going through electricity either; in fact, highest capacity storage systems are mechanical - flywheels, lifting heavy objects high, or pumping water up the hill.
True, but safety is a concern. Batteries are easiest for consumers to maintain safely. The failure modes of flywheels, lifting objects, or pumping water - when not properly maintained - are disastrous in ways that we mostly are not able to handle. Batteries start on fire, but we have fire codes and fire departments so your survival chances are reasonable. Batteries are also something that are available to consumers in a well engineered (well hopefully) package, while the others are a bit of a DIY hack. Electric implies you can connect to the grid and thus offload the whole concern to someone else for a small cost (this applies to the vast majority of us).
In the end you need to consider all the trades offs. Once you do though, electric starts to look good just because of how flexible it is, even if others beat it in any one area.
In the end you need to consider all the trades offs. Once you do though, electric starts to look good just because of how flexible it is, even if others beat it in any one area.
For periods of up to half a day or so, you could store that energy in the temperature of the building.
If one has a solar install already creating a diverse sources of heat makes sense in the northern climates.
[deleted]
The spelling that a Spaniard would consider correct is "¿por qué no los dos?" and it would still be acceptable as "por qué no los dos?"
People posting porque on English forums are not trying to communicate with Spaniards.
For a lot of folks in the Northern hemisphere, heating is the largest share of domestic electricity consumption. Same for offices. I would say there is great potential for this to reduce electricity consumption, plus the hot water can be stored without the loss at conversion that electricity has.
Readers in the UK might like to know you will almost certainly need planning permission to put one of those in your garden, and your neighbours will probably never speak to you again. The latter could be seen as a benefit for some.
Most incorporated places in the US (city, town, village, etc) will require permission from the local government to put up a windmill/ wind turbine; even when it's not required, local governments find ways to punish legal behavior they don't like.
In rural and unincorporated areas in the US, folks would likely be OK.
In rural and unincorporated areas in the US, folks would likely be OK.
[deleted]
> your neighbours will probably never speak to you again
I am ordering one right now.
I am ordering one right now.
I get the appeal but there’s a reason commercial wind turbines are really big and located in optimal wind resources.
In short, the capacity factor of small wind turbines in the places most people will choose to live is terrible.
It may not be as satisfying but some combination of solar panels, batteries, and heat pumps (with the proviso that people in really cold climate either need to go ground based or have a backup) is going to work a hell of a lot better for anyone not living in the furious fifties.
In short, the capacity factor of small wind turbines in the places most people will choose to live is terrible.
It may not be as satisfying but some combination of solar panels, batteries, and heat pumps (with the proviso that people in really cold climate either need to go ground based or have a backup) is going to work a hell of a lot better for anyone not living in the furious fifties.
Coincidentally I listened today to a podcast about direct water purification using wind turbines, the turbine is directly driving a water pump instead of going electricity->pump.
For water the benefits are not so much about efficiency, direct mechanical systems are the same or less efficient, but about simplicity and cost- those systems can be deployed and maintained in remote and poor areas without a need for costly technicians and parts.
For water the benefits are not so much about efficiency, direct mechanical systems are the same or less efficient, but about simplicity and cost- those systems can be deployed and maintained in remote and poor areas without a need for costly technicians and parts.
Where I live, there isn't a lot of wind on cold winter nights. The air tends to be very still in fact. I would not want to rely on wind for my heat.
A large tank, like the huge ones for heating oil in some old houses, would probably go a long way.
It baffles me that (here in the US) we don’t take full advantage of the sun in newly built homes. Use the sun to heat water, generate electricity, etc.
I rarely see newly constructed homes include solar panels, much less anything else.
It seems like “every new home needs solar power” should be a thing.
I rarely see newly constructed homes include solar panels, much less anything else.
It seems like “every new home needs solar power” should be a thing.
Driving a heat pump mechanically with a microhydro system would be interesting.
More consistent energy output paired with easy storage.
More consistent energy output paired with easy storage.
There's a practically infinite amount of sun and wind available.
The relevant metric for efficiency is not "heating done" over "sun or wind collected" but "heating possible" over "investment required".
A simple solution can outperform a more complex one.
The relevant metric for efficiency is not "heating done" over "sun or wind collected" but "heating possible" over "investment required".
A simple solution can outperform a more complex one.
I wonder if a torque converter from an automobile transmission would make a good "off the shelf" joule machine. It would certainly work for producing heat from rotational motion but I wonder how it compares to using a water-based impeller.
Very cool. I wonder if there's an even simpler geometry that chokes the flow of the air and uses the heat at the construction. May need to be very large, but it could be an architectural thing.
Seams more useful to generate electricity and use the waste heat that comes out of the inefficiency of the electricity generation.
Electricity is a far more useful energy type.
Electricity is a far more useful energy type.
For one this article is wonderfully out of season <wipes sweat>.
If you generated electricity you'd be able to also use it for cooling.
For two... how much land do you need to have for a 8 meter windmill and a reservoir with 20 tons of water? Looks out of the question even with detached house suburbs.
If you generated electricity you'd be able to also use it for cooling.
For two... how much land do you need to have for a 8 meter windmill and a reservoir with 20 tons of water? Looks out of the question even with detached house suburbs.
Especially when combined with a heatpump that can move a multiple of the input energy as heat.
No idea how I can see the contents of this article. I see the title and a big yellowish area below for comments and signing up. Maybe because I use Firefox?
Low Tech Magazine is a really inspiring page that I love to read, even if I am not particularly interested in windmills. Thanks a lot!
well while we are on the topic of heating i am still surprised 'data furnaces' have not been adopted more.
https://en.wikipedia.org/wiki/Data_furnace
https://en.wikipedia.org/wiki/Data_furnace
Lovely, but heat pumps can easily top 300% efficiency. If your electrical generation and transport is ~50% (which seems shockingly bad), you get a lot more heating from a heat pump than from direct mechanical heating.
The article has a long section on using the windmill to directly drive the compressor of a heat pump using a gearbox. This is likely to be more efficient than converting to electricity and then using that to run an electric compressor.
I know, I saw that. The article is lovely, and I love the design (dithered images like that hits all the right nostalgia notes), but it's lacking in a meaningful technical analysis.
Directly driving the heat pump has the potential to be more efficient still, but it's 1) very hard to design and 2) a custom (and therefore quite expensive) design.
Hooking your turbine to a generator, which can probably do something like 80% efficient transformation of the mechanical energy to electric energy (incorporating losses). Wire that generator to an electric heat pump.
240-320% > 100%
You can lose another half of your electrical energy in transport and storage and still come out ahead. Thermodynamics is weird.
Directly driving the heat pump has the potential to be more efficient still, but it's 1) very hard to design and 2) a custom (and therefore quite expensive) design.
Hooking your turbine to a generator, which can probably do something like 80% efficient transformation of the mechanical energy to electric energy (incorporating losses). Wire that generator to an electric heat pump.
240-320% > 100%
You can lose another half of your electrical energy in transport and storage and still come out ahead. Thermodynamics is weird.
Energy means nothing without knowing it's entropy!
Electricity from solar panels on your roof is in the range of 16-23% efficient, but there are no distribution losses. Electricity from a coal plant or single-cycle natural gas plant is ~30-40% efficient, and a combined-cycle natural gas plant can reach up to 60% efficiency under ideal conditions, with an additional 5% of produced electricity lost in distribution.
Yes, and wind turbines are 20% to 40% efficient at converting wind into energy
Wouldn't 50% be outlandishly good for solar? I think even 25% would be exceptional.
Yes, but this isn't solar. And to be a like-for-like comparison, we'd have to incorporate the lost/missed energy in the windmill's vanes.
Ooof. What? The first paragraph and it's just utter bollocks. Combine a solar panel or a wind turbine with a heat pump and despite generation losses it will outperform any thermal collectors - there's a reason these got virtually phased out!
And on top of that: local windmills, that may work out on farms in backwater rural towns with no grid worth calling it that, but good luck getting a permit for windmills in anywhere else, and when there's no wind you're straight out of luck whereas an electric heat pump can always be powered from the grid, or in the case of a massive power outage, from an on-site backup generator.