Paul, when calculating the energy stored in the water, you forgot to multiply by the specific heat capacity; 1 ton of water raised in temperature by 20 degrees C has 84MJ (23.33 kWH) of stored energy.

@Free_Falastin2024

2 жыл бұрын

It doesn't change the fact that the water cannot be maintained at 20 degrees using a passive solar design. Honestly, I'm just glad I don't have to hear feet, pounds, and Fahrenheit on Paul's channel so I'll live with his calculation omissions.

"Doesn't work" and "isn't a complete climate control solution for all climates" are different things. Any thermal mass that can store heat during daylight and release it at night will have some benefit. It can help during the summer to diminish high heat days as well. Is it a perfect solution? Of course not. But if your climate isn't too far off, a little bump can add significantly to your usable grow season. As example, in the Pacific Northwest, modifying the temperatures even a couple degrees overnight can extend a 4month grow season to more than 6 months. Considering the minimal cost, I most assuredly consider that "working."

@davidfuller764

4 жыл бұрын

Christian Swensen the tub of water looks ok, but as stated in video, and as my father would say: it’s a “taker upper’r of space.” I am not you and I will never be you, but for me the maths and logistics caused me to not want tub

@ChristnThms

4 жыл бұрын

@@davidfuller764 as you say, every case is individual. Having grown up on a working dairy, with several other types of agriculture all around us, I will verify that to much of this country, space is cheap. If a "taker upp'r of space" offered any benefit at all, most farmers would gladly take 2 of them, just in case it does work. But perspective is everything, and in a more confined area, any space savings might be worth chasing.

@Ida-Adriana

2 жыл бұрын

@@ChristnThms Is it true that farmers are having a hard time making money from their land?

@ChristnThms

2 жыл бұрын

@@Ida-Adriana that's a more complicated question than you'd think... Modern aggriculture is heavily subsidized, which keeps the profit intact but at an extremely low percentage. The effect of this is that the only way to farm most crops is on a vast scale. This is where the investor-farmer (not an actual farmer at all) makes millions or even tens of millions, while the family farm right across the street goes bankrupt. A dairy with 100 cows will probably fail, but a dairy with 100,000 cows will succeed. The subsidies also create an interesting effect of encouraging over-production in specific subsidized products, while ignoring other products which leads to shortages. Let's just say that, as usual, once the goverment gets involved it becomes a shit show, and once subsidies are involved there is no market response left.

I'm happy you did this video for no other reason than it got me thinking. There's also a lot of useful information in the comments that took me even further. For someone new to going green this is great! :)

I've enjoyed your videos on geodesic domes! Thanks for all the knowledge you share. I'm not saying passive greenhoused work or don't work but I don't think you can answer this question with such a simplified model for the energy budget. First of all the energy stored in the water at 20°C represents the amount of energy required to heat the water from 0°C to 20°C so you won't be needing to "fill" this energy reservoir on a daily basis. Second, the water in the tank won't only be heated by the direct sunlight hitting it. The sunlight will also warm all other heatsinks (earth, greenhouse atmosphère, soil in pots, water in the soil, etc.). Heat may then also be exchanged between the atmosphere and the water tank. Lastly, and quite mainly, it all depends on the volume of air inside the greenhouse that needs to be heated or maintained at a given temperature and the heat losses with the outside atmosphere. A complicated question! One that cannot be answered with a too simplified model I'm afraid!

Paul, in a winter you have only few sunny days per month, depends on region of the greenhouse location. So only summer can provide enough energy for accumulation, you can store this energy in the ground and use it passively at winter

Some people are just smarter than others. Obviously all that a person needs to do then is to alter any given situation from this calculation so that it does work. More mass, more conductivity and more reflection would all add to the benefits of this equation. And thank you for your time spent effort on this. It is a base line.

Agree. It took me hours to figure because it's been years but I came to the same conclusion. Then I found the same problem on a thermodynamics exam from old college notes. Same conclusion and gets worse if you figure clouds in certain areas.

I totally agree, you need active heating systems even if using renewables they need mass in excess of the volume of the greenhouse. They can be done but not as passive

@jeweleratlarge

3 жыл бұрын

What about using a fresnel lens to heat a metal mass that can conduct heat into the water tank?

There's a couple disagreements I have. first, it depends on what you define as "working". While it may not give you year round growing. At what point in the year does insolation drop to the point that it doesn't work? The design will still extend the growing season earlier in the spring and later in the fall. Secondly, the math was done using insolation on a level surface. Both the greenhouse surface and the water tank surface can be sloped to maximize insolation (ie. sloped such that the plane is perpendicular to the incoming light). While the sun in winter is traveling further through the atmosphere, it's insolation is still strong, just spread more over the land (just try turning you face toward the sun on a sunny winter day).

@Geo-Dome

7 жыл бұрын

I agree about an extended growing season but by my calculations there is about 30 times less energy in the winter sun than mid summer. There can be the illusion of plant growth very early in the year with seedling etc but they are using the energy in the seed to make there first growth (not the sun) so I would define "working" as receiving enough energy from the sun to photosynthesise the required sugars too grow and ripen fruit or to maintain a temperature above 20°C in our "passive" greenhouse. I just don't think either is possible in the Northern hemisphere in Dec, Jan or feb. I realise that everyones context is different but for me it absolutely will not work. If I can save someone from wasting there time and money trying to build a greenhouse that will not perform as they would expect then I would say this video has been a success. I do offer an alternative here: kzread.info/dash/bejne/poWemsqmf93Wo9o.html

Dear Paul Robinson, First of all, I thank you for your wonderful work with all this information about the dome, that's amazing. But when it comes to thermomass and patient warming, you've forgotten some important parts of the hot dynamics that will always go up. So in your building you will reach 1 meter high, you tec. Could measure 15 degrees, and at the top of the same greenhouse you get a damp air of at least 25 degrees in temp. Also in a cloudy day in January, in southern England. Like others in the mail it is extremely important to keep the temperature difference as low as possible in order not to heat the house, between idea / out and there approx. Half of the surface of your house will get drastic significance, for total heat loss. Therefore, you need a passive intelligent building, not just the actual heat storage you have to think about, but also the actual energy you can actually collect, low temperature heating in brick / sand on the floor will be most effective where your housing area in Square meters x with clogged stone / sand like floors etc. 0.3 meters will be the most efficient (even a small house of only 10 square meters, which provides an effective heat storage of 3 cubic meters). There you circulate the air from the top of the house, under the floor of the drain pipes. This solution also does not provide valuable space in the greenhouse, while it provides a better indoor climate for your plants. If you wish to further increase the accumulated effect, add a membrane / plastic underneath the floor to form storage space for your drip irrigation system. After a brief review, I found that the actual storage in your tank could achieve 9KW of practical input daily (23KW theoretically), but since there is no efficient temperature control over to the thought of daytime, the yield will be sparse and bad. As you say it will only take up valuable space because no effective management of the heat in the house has been provided to the tank. Have been working for alternative energy solutions for almost 30 years, and the past has been working with a big Arctic greenhouse project that could reach many thousands of households next year. In recent years, and the next 15 years, it is the project that links Arctic and desert together. See www.Water-For-Life.org

Hi Paul, love love love your work. I'm not sure if you have actually tried an experiment before saying passive doesn't work or if your basing only on calculations? But I have found it works great here in Canberra Australia over winter using 3500L litres in IBC containers in a twin wall poly 3m x 5.4m greenhouse. With many frosts we have here the minimum air temp recorded all winter was 13C. I think its very important to have the water storage off the ground as an IBC container achives otherwise the ground absorbs/sucks the heat out. Also double wall insulation makes a massive difference I feel. Maybe where you live you don't get enough winter sun?

@Geo-Dome

7 жыл бұрын

The way I design is to do calculations first and then test in the real world of the numbers look good. I've done lots experiments with solar panels and solar hot water both don't produce any usable energy in winter where I live. Minimum temp of 13° C is great, no way I can get that over winter here. Thanks for taking the time to comment.

@rebelquadronfpv1065

6 жыл бұрын

@r b, very keen hear more about your exact build if possible. 👍👍

@lil0lizify

5 жыл бұрын

word

Circulate the water from the tank through 1/2" black tubing. This is similar to a solar pool heater. I think you would find that the energy gain in the tank would be much greater. Augment with a rocket stove to heat water on cloudy days.

@Geo-Dome

6 жыл бұрын

Yes that could work but we need to do the math, What temperature do we need to achieve, how much energy is in the winter sun, what is the U value of the greenhouse? etc then it's a simple task of running the numbers, if you just want to stay above freezing it's too bad, but when you need 15° in the greenhouse when it's -5° outside, it's a lot tougher.

Flat plate heat exchanger into the water in the greenhouse via heat pipes. Plus have wrap around curtains on the dome with inside mylar layer clay aerogel sandwich and outside layer polyester etc. Passive and will work and it will work even on cloudy days.

What happens if the water temperature is raised by a heater of some sort? if you were able to keep the water at 60 degrees in the dead of winter, how much better would it work? What would the magic number be for water temperature to make sure it worked. 50? 60? Would you be willing to do a few more calculations and give us some ideas?

Hey Paul, I have a 16 foot diameter geodesic dome greenhouse similar to what you have pictured. I submerged my pond beneath the frost line And I maintain a steady 40° in that water no matter how cold it gets outside. I experimented with heating the pond, but could not keep the greenhouse above freezing at night even when I got the pond up to 80°. I have not insulated my north wall yet but heating the pond with a bucket heater is inexpensive and if I were going to grow through the winter it might be feasible to stay above freezing once I insulate that north wall. I am still experimenting. I am just more interested in finding passive sources of heat So I was hoping your video would conclude with recommendations.

@keralee

2 жыл бұрын

Have you insulated north wall yet? And if so, is it helping and in what ways?

Hey there Paul I have a solution for you. Lining the water container with Vanta black/black 2.0 and creating a lens to focus the lights onto the water to heat the water would also be a passive solution. I haven’t done the maths, I wonder if anyone else has given this thought.

The bulk of the light in winter is diffuse not direct , another reason why its not effective at heating the water tank ;) Insulating the north wall will affect light levels because diffuse light comes from all directions.

Happy to know that the last tomatoes I eat didn't even exists.

If you had mylar on the inside of the insulating panels, I wonder if they'd form a parabolic mirror?

Thats correct in winter, summer time. But if its summer time. Lets say , day time is 26C and in the night time(or correct to say morning) can fall to 10-14C. In that case(10C range difrent), flowers falls off. In some times it can happen, not often night, morning temperature falling so much. Ofcourse in 15m2, it can make 10-15, flowers to fall off. And system not worth money, or space. Another thing is humidity. Too big humidity will damage flowers. If its Opened water tank, is only making you another problem, more invesment. Waiting for second part.

Add a reflective surface to the back of dome insulation and you can use all the radiation hitting the back of the dome to heat the water ==> ~ 88 M^2. By the way, Solar radiation is 1100 KW HR /M^2 during winter also. Maybe you only get a fraction into the dome. I'd say 165 KW-HR gets into the dome each sunny day. Maybe 25% of that might get into the water. That would raise the temp ~3.6 deg C. I'd also assume you vent the dome if Temp gets above 27 deg C. Plus you have about 20000 KJ reserve held by the air in the Dome. What I can't help you with is the heat transfer during night time from the dome. But if the top of the dome was finished with an equivalent two way mirror reflecting radiation from plants back inside the dome, that may prevent frost bite. I think frost bite damages most plants more than just below freezing.

@donkihotay5748

5 жыл бұрын

I think the actual best solar wattage available is 1000w/M^2, not 1000KW/M^2. Error effect would 3 orders of magnitude. What do you think?

Solar panel with two wires going into the tub of water?

Can you build one to prove your math. I want to build a dome with a water mass heated using a fresnel lens to boost the btu's. If installed right it will boil water off sun light. Thanks again

There are several steps you could take to boost the heat retention you can paint the tank black you can make it surface area of the tank larger you could add mass in the form of rocks and Bricks wherever there wasn't plants growing this would help some I don't think it would still solve the complete heat problem you could also put a hot-water thermosiphon panel inside or outside the Dome to boost the water heat again I don't know if that would be enough to heat the building I live in Wisconsin USA our Winters are brutal you might be able to extend the season here but without some kind of supplemental heat source that is not going to work in my climate In fact when I was younger the idea of a year-round Greenhouse calculations proof that putting the greenhouse in my basement and artificially lighting it and using the heat that was already present would have been much more efficient

@keralee

2 жыл бұрын

OYR...One Yard Revolution chan in Chicago is growing cold-hardy greens over winter without water tanks using hoops inside of hoophouse. And I think the outer hoophouse is double walled plastic, to thats 3 layers. I am considering building something similar this summer in WI with a dome-in-dome system, tanks, and a rocket mass heater because...well its Wisconsin!

Many thanks Mr. Robinson for keeping it real and doing the homework, so our heads are filled with facts and figures instead of info that just won't work. Liked and Subscribed. I clicked the little bell icon to the right of the Subscribe button for all updates.

A lot passive greenhouse designs have too much glazing, which causes problems in winter with heating and in summer with cooling.

black tubing a little pump might heat it way more :) ... need a bit of electricity.

Energy from the sun has to be multiplied by the exposed surface in square meters. Internal absorption, emission and recflection of radiant heat must be considered. Power from the sun can be trasformed in electricity (15%) AND heat (80%). An electric powered heat pump can then generate heat with a 400% factor. So at the end you can have (4x0.15 + 0.8) × 1000 W = 1400 W thermal power per fully exposed square meter of pv. With a correctly designed air convection loop (double layered glas + air gap behind the pv + heat pump + thermal storage mass (insulated from external surfaces)... ...you'll get it!

So it doesn’t work for heating water but it works for plant greenhouse?

1 ton of water only takes up 0,757 cubic meters which would seem a small tank for this purpose. Since the energy of the sun is equal everywhere the surface area becomes the energy multiplier. You want a tank that maximizes surface area to volume.

@lhpl

3 жыл бұрын

I guess it's a metric ton = 1000 kg = 1000 l = 1000 dm³ = 1 m³.

Respectfully, you are using faulty reasoning here. You measure sun heating water as per metre. However, the ambient temperature which the dome produces also heats the water. A better way is to do direct observational experiment using thermometers.

That is incorrect. They do work. In COLORADO!

Compost pile heat exchange

What about cloudy days? How the water is gonna be heated?

What is the CAD software that you use ?I like some of its features. AutoCAD ?

@Geo-Dome

7 жыл бұрын

I use sketch up pro, I did pay for it as I use it professionally but there is a free version, it only lacks export to dxf function so worth a serious look. I have tutorial videos and will be doing more soon.

@davecrysdale3647

7 жыл бұрын

Thanks Paul, I've heard of SketchPro. Now I like what I see. I will continue to follow your releases. Hopefully not so many windy days for you during video recordings ! thanks again, Dave C.

I agree that the passive solar heated water and north facing wall dome is a flawed concept. As soon as I saw the idea pitched I immediately had a bad taste from it. I learned in chemistry that you need a lot of energy to change the temperature of water. so is it really worth it? I mean, it takes up a lot of space, requires a fair amount of maintenance, and you won't get that much from it passively. although it would hold it's heat exceptionally well so if you could connect it to a heater then it might be useful. the north facing cover also seems awkward and unnecessary. you build a Geodesic Dome greenhouse to maximize sunlight, and then you build a wall? sure it may not see much light in the winter, but what about the other 3 seasons? what about light bouncing off the environment? it also kind of ruins the symmetrical design of the dome. I do however believe there are good passive designs for Geodesic Domes, including windows that passively open due to vent openers activated by a piston filled with beeswax that expands and contracts perfectly with ambient temperature. I also think geothermal, solar, hydro, wind can potentially be utilized for a passive greenhouse system. this is my life dream. thanks for posting the video!

@Geo-Dome

7 жыл бұрын

You may be interested in the next video Trevor, passively heating a greenhouse with composting kitchen waste. uploading tonight.

@keralee

2 жыл бұрын

@@Geo-Dome I would add some chickens too, they are toasty creatures!

Your doing a lot of figuring but there are many people on you tube that have greenhouses that do work. It's like a bumblebee doesn't have enough wing area to fly! Oh, one just flew by!

@snowyg357

3 жыл бұрын

It may be the thermal heat stored in the earth helping to keep those greenhouses warm.

@elliottwhitticar2383

3 жыл бұрын

Yes. Interesting analysis, but I would think the tank would warm up during the day through all the usual methods of heat transfer - radiation, conduction and convection. Calculating one out of three seems incomplete. It's very much like ignoring the vortices on bumblebees' wings!

What software is that ? I really like the ‘ shadow ‘ feature.

@Geo-Dome

4 жыл бұрын

It's called sketchup, I think they have a free online version.

While the breakdown of these calculations are interesting - Passively heated greenhouses do work - there are many living examples -including in the UK and several excellent books on the subject available - The issue with this example is that a well designed passive greenhouse depends upon many factors other than introducing one tonne of water into a 15 m2 dome greenhouse which insulated to the North side. Other factors to consider are- the quantity of water in relation to the glazing surface area is important, between 75 and 190 l /M2 is recommended if you are only relying on water as your thermal mass. 0ne ton of water in a 30m2 ‘surface area’ greenhouse would be well short of this recommendation , also to consider is whether the water is in small or large containers - what colour the containers are painted, where they are placed - an important issue also is the fact that water gives of large amounts of heat when it freezes - therefore this can give significant protection in short spells of cold weather. Also the thermal mass of the water not only reducing the cold in the winter but also can help to prevent overheating in the summer - a considerable problem in many greenhouses. Consider too the r values of the glazing materials, a passively heated greenhouse can also rely on storing a large amount of heat in the soil as well as in water, insulating the base of the greenhouse, burying the greenhouse into the ground somewhat can be helpful. I suspect the shape of a dome greenhouse is not well suited to a passively heated greenhouse as the shape of a dome does not lend it self to storing sufficiently large qualities of water on its Northern side, a shape more akin to an earth-ship is a better suited design if you want lots of thermal mass. I Suggest anyone interested in passively heated greenhouses, not be put of by this video - and research some of the excellent books on the subject from people who have successfully made them.

@dorkatomankova5132

6 жыл бұрын

Thank you for your great comment. Can you suggest some good reading please?

@lil0lizify

5 жыл бұрын

word

@chenh02

5 жыл бұрын

this is the right way to solve problems, step by step, every little helps.

Can you post the link to your sketch up file?

@lil0lizify

5 жыл бұрын

hook it up pauly!!

Rather than having a cubic meter of water in a large tank and hope for the best, circulate it though a car radiator (with forced airflow) or put the water in 1000 PET juice bottles to give increased surface area.

Pot belly stove and some copper tubes,

Full of arbitrary numbers pulled from thin air, continuous mixing up of unit types, … I appreciate what you were trying to evaluate in a more quantitative fashion but when your math is this screwed up the numbers don't mean anything and you may as well have just looked at it and made a guess. You also did not include the energy that could have been absorbed by the water through conduction with the air (which is much warmer in the sunny day obviously, I am not sure what % of the energy the water will absorb is likely to be from that). One obvious variable to play with would be surface area to water volume ratio. Another is total water stored. Even a small wall of rocks piled up outdoor (not enclosed in a greenhouse) can be enough thermal banking to extend a growing season a bit. Another note on this is the option of having additional radiation collection area placed outside and circulating to the inside, like an evacuated tube solar water heater or the simple homemade versions. The insulated rear wall could be lined with reflective material focused toward the water, increasing square centimeters of radiation collected. The building heat loss could be reduced with simple insulation strategies like a double or even triple wall with air gap to reduce the amount of energy needed. One final thing to mention is that this barrel is not the only thermal mass storing heat, it is just more optimized for doing so than most of the other things in the building (so there is more energy available than only what you find in the water).

@Geo-Dome

5 жыл бұрын

I get your point, I've done a back of envelope calculation, but you haven't provided any numbers at all in your criticism. I'll probably do a more detailed video at some point, though I had thought that there was enough facts in this video. I've done enough math to prove that in the UK adding a water tank with 1 ton of water will not increase the average temperature in a greenhouse by much at all (less than 1°C) If you disagree you should provide at least rough back of the envelope calculations and give some numbers. There is a definitive answer! "One ton of water will boost the average temperature by X°C in a greenhouse" - My calculations say less than 1°C What do you say? I'm happy to debate this even with approximate numbers...

@SporadicUploads1

5 жыл бұрын

@@Geo-Dome What numbers to use depend on what equipment you are willing to set up with it, what your greenhouse is, etc. In my greenhouse I do not have any water barrels and I do have a compost berm around the outside so I am in agreement with you about your basic premise and I am not having a conflict with you. (I do have ~2 tons of water in my greenhouse though since it is an aquaponics system, the water temp is much more stable than the air and that is what all the plant roots are feeling). But I would disagree with a statement: "passive solar heating and heat storage can't work." I don't even really need to do any calculations because it is obvious that if you wanted to dig a large insulated in-ground storage pit of water and use one of the many designs of solar thermal heat collectors you could simply scale-up your energy collection and storage to have like 2k gallons of 80°c water to heat your structure (radiator), so there is a point that this will work brilliantly if you want to put enough in to it. It would be an initial investment for long-term set and forget. Here are some rough almost meaningless calculations: Say we want to provide average of 1 kilowatt of heating to the greenhouse 24 hours a day (winter) so net output must exceed 24 kWh per day. Say we can get (in winter) an average of 5 hours of direct sunlight per day worth 0.15 Watts/cm^2. That would be 0.75 Watt hours per cm^2 per day of raw input from nature. 24000 / 0.75 = 32000 cm^2 needed to equal that, I will multiply by 4 to cover the rest of the energy that will be wasted, so we need 128000 cm^2 or 12.8 square meters of sunlight collection to have 4x abundance of input energy to force it to work (built as for example two parabolic troughs with a copper water pipe in the middle and glass enclosing the trough as a solar oven. Two troughs, each one is 1 meter wide and 6.5 meters long). So for the insulated water vat, lets say we want the water at 70°c with variability no more than ±15°c. That means we have 30°c of temperature swing to play with for releasing energy into the greenhouse. Water stores 4.2 kJ/kg°C, 1 kJ = 1 kilowatt second, 1 kg = 1 liter. We have 30°c so each 1 liter stores 126 kWs = .035 kWh. To find how many liters store enough energy, divide 24 kWh / .035 kWh = ~686 liters of water is all you need actually, I thought it would be more.

@SporadicUploads1

5 жыл бұрын

​@@Geo-Dome Or maybe what I described in the previous comment with the math was a little too complicated of a system to be considered "passive solar." So I guess you could replace that with black painted pipes of water covering the inside of the entire insulated north wall. For my small greenhouse of 200 square feet / 18.5 square meters, there is a back/north wall surface area of about 24 square meters (footprint is 8 feet by 24 feet, with a 10 foot high 24 foot long north wall, so north wall is around 3 meters by 8 meters). So that is more than enough solar collection area to supply the average 1kW described in my previous comment with the math. Size the tubes so total storage would equal 800 or so liters (no point of calculating tube diameter here lol) and put pressure release valves at the top just in case. To control the release rate it may be necessary to have a certain portion of the tubes glazed over and blocked from conducting heat with surrounding air, so there is limited surface area that is heating the greenhouse and it happens more slowly.

@Geo-Dome

5 жыл бұрын

Thanks for taking the time to provide calculations, ok this is my take. Greenhouse surface area for a 15m2 area is about 40m2 U Value for polythene about 4 W per sqm per degree. So the greenhouse will loose 160W per degree. (not allowing any lose to the ground) So if you have 1kwh source of heat it would hold the temperature about 6°C above outside temperature. 10 kWh of energy will rise the temp in a 1000kg tank by 10°C for solar energy 150w per sqm x 15 = 2.2 kwh x 5 hours = 11kwh. Now this is my issue, there would be enough energy on a sunny day to raise the temperature in the tank by 6°C the tank would not transfer any heat to the greenhouse until the greenhouse temp was below 6° when the greenhouse drops to 5° there’s 0.11 kwh of available energy but the greenhouse is loosing 1.6kw per hour if the temp outside is 10°C lower than inside the greenhouse. Now your figures state that we can get 24kwh of energy from 12.8m floor area, about double my estimates, even at that it’s a 12°C rise in temp in the tank, outside temp -10°C, 0°C in the greenhouse =10kwh of potential energy let’s say 14 dark hours with no energy from the sun makes energy loss totalling 22.4 kwh. Our numbers are not far apart but we seem to come to completely different conclusions, if we can keep greenhouse temp 6°C above outside then on a -10°C night the greenhouse would drop to -4°C. Finally to germinate seeds you need a constant 10°C - 15°C Variables. cover U Value greenhouse surface area potential Solar gain Temp differential required

@SporadicUploads1

5 жыл бұрын

@@Geo-Dome The 24 kWh per day is a very conservative estimate of power available from one fourth of the 12.8 square meters, based on only 5 hours sunlight per day at 0.15 Watts/cm^2 (normally people would calculate with 0.4 watts / cm^2 and probably account for more hours of light). The continuous 1 kW average across day and night is arbitrary (and I could re-calculate for other output requirements) but with any attempt at insulating (double clear wall, polycarbonate hard panels) I think it would be enough for a small greenhouse. Also I clearly described that the water would be kept in an insulated tank at 70°c ±15°c, so with a good sized metal radiator you could transfer heat to cold greenhouse air quickly (I said that because you are describing the water as being stored at only 6°). I think getting bogged down in how many square cm of radiator you would need to transfer x-number of watts with a 55°c temp difference is irrelevant to the point, which is that solar thermal collection can for 100% certain be used to collect and store enough heat to regulate the temperature of a greenhouse to whatever temperature you would want. You just have to do some experiments to calculate how many watts per square cm you can collect on average in the coldest time of year, and how many watts you need to heat your greenhouse, and use that data to size your solar thermal collectors and your water vat to match your needs. Position the collectors next to the greenhouse and work out some simple automation to operate valves or pumps to send the water through the right tubes. It's not going to be the most practical solution for everyone's situation but there is no reason solar thermal could not work.

Rocks embedded far enough into the ground to be mostly insulated from the cold air might store heat better than a tank of water. Can't say I've tried it though.

@MiscellaneousMcC

7 жыл бұрын

Water has a much higher capacity to store thermal energy than stone, sand, concrete, earth, etc.

@seroweassociatesllc

2 жыл бұрын

@@MiscellaneousMcC How long before the water starts to radiate heat? Say you have a solar water heater going through the water in the greenhouse, heating it up. Will it be warm enough to radiate before evening thus making the greenhouse to hot...?

@MiscellaneousMcC

2 жыл бұрын

@@seroweassociatesllc As soon as the temperature of the water is higher than the ambient temperature around it. Then it will begin to radiate heat. If the temperature around it is higher than the water then it will absorb the heat, and radiate it out as the temperature falls around it.

Your math is riddled with mistakes. Even if you got the math correct there are lots of incorrect assumptions. I have a passive solar greenhouse in Ireland and it works great.

@Free_Falastin2024

2 жыл бұрын

Hi, John. What's your minimum winter temperature and in which climate zone are you located?

Fix a magnifying glass that tracks the sun and focuses even more sunlight into the water pool. How bout daaa

@lil0lizify

5 жыл бұрын

yeah how about dat?

Passive greenhouse works, if anyone is interested can do some research about Eden Project in the UK. It can reach 40C degree with roof open. And all the rainforest plants grows 3x faster.

Your math doesn't really account for how thermal masses work. Even if it's negligible, the fact of the matter is that water stores heat and retains heat better than air does. The prolonged warmth of the water, will heat the air around it, keeping it warmer for longer. Again even if where you live, it's only a 0.5 degree difference in temperature, it still works. Broken math + no real world testing/experience, does not equate to a definitive answer. A better title, and thesis, would be "My passive greenhouse doesn't work as well as I want it to, due to engineering and design flaws in my methodology, as well as poor wintertime sun exposure"

What??? the sun doesn't worm the water??? yes it does work IF its designed right- domes are NOT the correct shape- a rectangle is much better- long side facing south- and this must be in the appropriate climate (high desert is best- cold/cool sunny climate) with good sun in winter- water containment must have a conducting surface and the more collecting surface- that sees the sun- per gallon of water the better- thus smaller containers. you also need high transmissive glazing- cheap plastic films don't last or let much sunline in. single layer glass is better and double pain is a bit better for most climates- triple pain not as good since transmissivity is diminished. and you also need moveable window/glass insulation systems- shutters/curtains, etc. for nighttime insulation! also a mass floor will help. and basically the rear of the structure and north end of the sides as well as the north end of the roof, needs to be well insulated also. the simple math isn't enough to simulate the conditions.

sad sad math, look around it works. plenty of functional examples in northern climates, even up in the rocky mountains growing year round... make all the equations you want, the real world speaks volumes.

@jonathanforlin1854

6 жыл бұрын

this is like trying to disprove earth ships with math, while people live in functioning examples worldwide. pencil pushing stiff necks!

What a load of crap. All the math was faulty. Not even close!

@lil0lizify

5 жыл бұрын

wheres your geodesic dome video bra?

I love your dome videos - and I can't say that enough. But this is complete rubbish as countless people here have pointed out. Why not remove this video?

I'm not sure your math proves anything. It's not like the water goes back to freezing every day, & you didn't factor in initial water temps, or nighttime temp drops. If mathematicians were in charge of The World, nothing would be possible😏✌

Sorry, you lost me when you wrote a formula using a mix of variables and units, and then again talking about kW per hour.

MATH NOT MATH(S)!!!!!!!!!!!!!!!!!!!!

You nead to work on your math. But it’s true, it doesn’t work.

This maths is crap mate sorry 🤨