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Solar energy for winter

How to keep solar heat for winter
  [vote for,

I cant stop thinking how to keep solar heat in summer, for the cold days in winter. Here's an idea. Concentrate solar energy by parabolic mirror, you get high temperature in the focus, put the limestone CaCO3 in the focus, it needs 900 C to burn, it will turn to CaO, releasing CO2. Keep CaO in dry place for winter, like fuel, nylon bags, etc.etc. Than in winter, mixing with water, it will turn to Ca(OH)2 and release energy, 67KJ per grammol, and with some mixing with air, it will turn to CaCO3 again, absorbing the CO2. Full cycle. If it could be some powderred stuff, maybe it can work all arround. I estemated that one house would need about 47 tons of CaCO3, which is about 15 cubic meters of volume. I know that CaO is quite burning stuff, but if it has been made safe, and clean...it is not so dangerous.
lazarus, Jul 09 2012

How to store heat for winter using water http://www.motherea...ticle.aspx?id=68244
[scad mientist, Jul 09 2012]

This is how you do it http://m.extremetec...f354b672622b8230aef
Prototypes in the field, already. [4whom, Jul 09 2012]

Fischer-Tropsch OTEC Fischer-Tropsch_20OTEC
a use for the stored CO2 [Loris, Jul 09 2012]


       Alternately, you could use a heat sink - which does much the same thing, only without all those dangerous chemicals.
zen_tom, Jul 09 2012

       There are various "geothermal" schemes that basically pump heat from the ground in winter, and put it back in the summer. It is less efficient (in terms of the amount of mass needed, to hold the stored energy) than this Idea, but since there is lots and lots of underground mass available....
Vernon, Jul 09 2012

       In more northerly (and, I can only assume, more southerly) climes, additional passive solar energy for the winter months is provided directly by the sun, no interseasonal storage required. In the summer, the sun shining through our south-facing windows falls no further than about 1/3 of the way across the living room, whereas in the winter it hits the back wall. Nifty, eh?   

       (Pedants: yes, I know why)
Alterother, Jul 09 2012

       I like the concept: store the heat chemically using endo/exothermic reactions, but I think you need to come up with a better chemical cycle than this to be effective.   

       If you have to heat the CaCO3 to 900C, you'll be wasting huge amounts of energy unless you have some kind of heat exchanger to transfer the heat from the CaO and CO2 to preheat the CaCO3. I'm not familiar with solid to solid heat exchangers, so maybe there is an easy way to do it, but I'm not confident.   

       I'm including a link that you might find interesting if you haven't read about it already. Someone built a very simple system to provide 90% of the heat for a house. It uses an 8000 gallon water tank (30 cubic meters) to store heat through the winter, so assuming you could make your system work, and depending on assuptions, you may have better volumetric efficiency, but warm/hot water is so much easier to deal with...
scad mientist, Jul 09 2012

       google zeolites, be happy, ignore masses (troglodites) they don't give off near enough energy when you burn them...
4whom, Jul 09 2012

       Incidentally, this idea (zeolites) is now becoming accepted, so therefore bun Not Widely Known To Exist!
4whom, Jul 09 2012

       Hey, [lazarus]! Good to see you again—it's been a while!   

       (Thank you, thank you! I'll be here all week. Try the veal!)
ytk, Jul 09 2012

       I've been toying with similar ideas for a long time to.   

       With this chalk/ quicklime/ slaked-lime/ chalk cycle, I think the CO2 should be captured. Rooms with humans (or other animals) in have a significantly higher CO2 concentration than atmospheric standard, and this is then a nice way of concentrating it further. It could then be used as substrate for Madai's "Fischer-Tropsch OTEC" system (link), which would then be carbon neutral. There's a bit more spread out transport between houses, but this does replace mining the stuff.   

       For this to work in people's homes, there's a requirement for it to be relatively safe. I think there's a possibility if the calcium compound can be contained in discrete blocks. I imagine an array of ~1cm layers, separated by a 'breathing' mesh, and all wrapped in a second fine wrap to keep the powdery stuff in.   

       If the stuff is being supplied to the home rather than generated onsite in summer then it can be done more energetically efficiantly (as scad mientist suggests). And it also means that it doesn't all have to be held in storage on the premises.
Loris, Jul 09 2012

       We designed our home to store heat in a 50,000 gallon underground water tank, to keep the temp to about 20deg C all year around. The temperature underground deviates very little all year, unless you're in a permafrost zone.   

       Architect we used thought it was a bloody marvellous idea, when I showed him what we had designed.
UnaBubba, Jul 10 2012

       That is interesting UnaBubba. According to my calculations, thats around 230 cubic metres, which would be a cube of about 6.15 metres to a side. I guess though that it's a prefabricated tank; probably a cylinder?   

       What sort of annual temperature cycle is there in your area?
Loris, Jul 10 2012

       What [Alterother] said. Doing nothing more than orienting the main living areas and the largest windows to the equator side of a house not only dramatically reduces energy use, but makes it a more pleasant place to be - bright and warm in winter, cool and shady in summer. The [Alterother] should also consider routing the warm exhaust air from any heat-producing indoor hobbies to where the human occupants will appreciate it, using a dehumidifier if necessary.   

       As [scad mientist] said, 900ºC is wasteful. Consider calcium chloride / water, which also has a large enthalpy, but only needs 165ºC or so.
spidermother, Jul 10 2012

       // routing the warm exhaust air from any heat-producing indoor hobbies to where the human occupants will appreciate it, using a dehumidifier if necessary. //   

       Done and done. We also run it through an activated charcoal filter. The warm air from this particular 'hobby' can be... aromatic... at times. But it does help heat the house in the winter.
Alterother, Jul 10 2012

       Hoorah! That made me so happy I literally had to get up and do a little dance. Most people just don't consider these things.   

       It's even possible to go full circle and give your hobby the benefit of your exhaled carbon dioxide.
spidermother, Jul 10 2012

       That's an idea. I sometimes haul a CO2 bottle up from my shop and set up a bleed system during the vegetative cycle, but I'll have to work on harnessing our exhaled breath. Maybe a modified SCUBA could collect it for later use.   

       Most of the heat that we recover actually comes from the light banks and, depending on the preferences of whatever variety I'm growing, a small electric radiator; originally, the idea was to pump the exhaust back into the house for the oxygen, which is quite nice, but it's so warm that we pipe it outdoors during the summer and swap the ducts around when it starts to get cold. So the oxygen and heat do go to waste for four or five months out of the year. We now grow the hothouse strains exclusively in the winter; it seems silly to run a space heater at 80 degrees F all summer.
Alterother, Jul 10 2012

       //Consider calcium chloride / water//   

       How about magnesium chloride [spidermother]? That is the one I have been considering for years, mostly because it has similar properties to CaCl2 and I have access to large quantities of it. I am assuming it is more enthalpatic than cal chlor as well.
AusCan531, Jul 10 2012

       It's 12m x 9m x 2m, [Loris].   

       Temp range is from about 0degC - 25degC winter and 16 - 40degC in summer.
UnaBubba, Jul 11 2012

       That sounds like a fine bit of domestic engineering, [UnaBubba]. I'm curious. Do you have some sort of access hatch? Do you ever need to change the water at all?
pertinax, Jul 11 2012

       It sounds great.   

       Did you get it made bespoke? Which way up is it- that is, which of those measurements is the vertical? If it's tall and thin, is that to improve efficiency; do you draw the coldest water from the bottom to warm, and the hottest water from the top for heating? Or is it 'flat' for structural reasons?
Did you come across any interesting gotchas during construction?

       Really great. Here, hardly anyone builds their own house any more. There's a program called "Grand Designs", where people do that, though. They always[1] come in massively over budget and delayed. Usually, they've spent years getting planning permission before filming starts.   

       [1] As far as I know with only one exception.
Loris, Jul 11 2012


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