Heat your house with a mechanical windmill (2019)
solar.lowtechmagazine.com
solar.lowtechmagazine.com
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.
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.
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
... 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.
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.
Just mix in nuclear waste with the concrete. It'll keep the driveway free of ice, and illuminated after dark.
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.
I don't know if this is feasible at all, but the idea keeps coming back to me.
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.
A cookie would be bad because you're actually digesting it.
Beta or gammas are harder to shield.
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.
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…
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.
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.
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.
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 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.
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.
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.
https://www.pv-magazine.com/2015/10/09/spains-government-app...
The tax was repealed in 2019, but still.
They do an awesome solar+wind deal too: https://www.powerhousewind.co.nz/powercrate/
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.
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".
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...
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).
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.
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 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.
Just because silly bureaucracy exists doesn't mean something is a bad idea.
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 applications in their wheelhouse, though, they are absolutely amazing.
"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."
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.
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.
But the comment you replied to initially talks about the limit of solar thermal collectors.
(To be clear, I'm sure this would not make sense economically, but it would be really cool.)
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).
Please expand on this. I have no idea how these two compare in efficiency (but apparently you do).
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.
Am I understanding it correct that the efficiency is, in this case (25%; COP >4), greater than 100%?
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.
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.
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
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.
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...
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.
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'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.
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.
Someone working in the field told that anything below mast height of 30m is going to a toy at best.
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.
I can imagine some post-apocalyptic scavenger rigging up an air-conditioning using using a windmill and car parts.
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.
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.
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.
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.
Mechanical gearboxes also generate heat, so you'd need to capture that too.
In rural and unincorporated areas in the US, folks would likely be OK.
I am ordering one right now.
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.
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.
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.
More consistent energy output paired with easy storage.
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.
Electricity is a far more useful energy type.
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.
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.