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Timoja
Member
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# Posted: 26 Feb 2018 01:07pm
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I'm currently working on a project which would allow storage of excess energy as heat in a thermal battery. Using a reversible chemical reaction of calcium chloride with water, the system will have a much higher energy density than water tanks. One possibility would be the storage of the the surplus photovoltaic energy in summer and use the energy for heating in winter. Other usage scenarios could be cooking or hot water generation.
Anyway the system will need large quantities of chemicals (order of tons) to store a meaningful amount of energy.
Does anyone in this forum have a PV system that produces large surpluses in summer and a need for heating in winter? Could you give me an idea how much energy you have as surplus and how much energy you need for heating? Do you think such a system might be interesting for some settings?
Small example
I already did some very rough calculation for a PV system with 1kW, assuming an 80% surplus during spring and summer. This would translate in roughly 1000 kWh stored for winter, which means you could have the heat of a 1kW heater running for 40 days continuously. The price tag of the chemicals for such a system would be 340$ for the 4 tons necessary. (Prices and energy density taken from here http://publications.tno.nl/publication/34607613/2MLhh3/trausel-2014-review.pdf)
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DaveBell
Moderator
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# Posted: 26 Feb 2018 02:35pm
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1. Can you post a link that shows the cost of the thermal battery you are using?
2. Why are you posting "basic research" of undeveloped systems questions to a cabin web site?
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rockies
Member
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# Posted: 26 Feb 2018 06:25pm
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If I have extra energy I'd rather store it as hot water for domestic use. Why complicate things?
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Just
Member
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# Posted: 26 Feb 2018 07:26pm
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They are probably talking about the old phenomenon of adding water to plaster of paris and it releases heat then heat it up and dry it and it-stores heat .not new
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Timoja
Member
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# Posted: 27 Feb 2018 12:09pm
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@DaveBell: As the system is still in research I could just give you the list of components that I will use. The link shows how much the chemicals cost.
I posted here to see if cabin owners might be interested in such a system and to get feedback what they would expect from it. I'm planning to do the research anyway, just wondered if I should "open source " the idea. This is just curiosity if this could help someone, I don't want to waste anyones time.
@Rockies: Just heating a water tank is probably the easiest and cheapest solution.
However, I guess the heat will be lost after one week of cloudy weather whereas the "thermal battery" solution can provide the heat even after months and allows to use heat from summer in winter. Another possible use case is a occasional inhabitated cabin that stores heat as soon as the sun shines, but only heats up when somebody is actually there.
@Just: True, this is a quite old idea, however I've never seen it used to store solar surplus energy.
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DaveBell
Moderator
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# Posted: 27 Feb 2018 03:43pm
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Thanks for the link to the three year old basic research paper on chemical engineering for solar applications. We are aware of salt heat collectors used in the desert solar farms that power a large town.
Quoting: Timoja I'm currently working on a project which would allow storage of excess energy as heat in a thermal battery.
Quoting: Timoja The link shows how much the chemicals cost.
So from the chemical costs I can assume the thermal battery will cost $50,000 and and store energy for a 24 story building with a break even point of 20 years.
Quoting: Timoja I'm planning to do the research anyway, just wondered if I should "open source " the idea.
To people living in tiny cabins in the woods who might have a PhD in Chemical Engineering. Are you absolutely positive this venue will help your laboratory work?
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rockies
Member
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# Posted: 27 Feb 2018 06:37pm
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Part of the allure of being in a cabin is the opportunity to live simply. If you were out in the wilderness 30 or 40 years ago just having enough energy for a few lights seemed like a godsend but as technology has evolved and manufacturers continue to improve their products you can now have a "city" house out in the country.
That said, simplicity still rules the day. This heat storage technology seems to be far too involved for the average person setting off into the woods. Why don't you try the Green Building Advisor site to get feedback for something like this?
http://www.greenbuildingadvisor.com/
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NorthRick
Member
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# Posted: 27 Feb 2018 07:25pm
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A couple in Fairbanks, Alaska built a house that gets most off it's heat from the sun. For those that don't know, Fairbanks is in the interior of Alaska and can get quite warm in the summer 80's and 90's and quite cold in the winter -50 F. There is also lots of sun in the summer and lots of dark in the winter.
The house is super insulated with insulated shutters that cover the windows at night in the winter. They use several large (like 20,000 gallon large) tanks that are buried and insulated to store heated water. The water is heated by thermal panels in the sun in the summer and then the heat is transferred to the house in winter.
It wasn't cheap and it doesn't quite get them all the way through winter so they still need another source of heat. I think it was mostly a "it's possible to do it" type project rather than a practical one.
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rockies
Member
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# Posted: 28 Feb 2018 06:30pm
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I don't know why they don't use a geothermal heating system and just let the earth heat the water. Much less digging than burying huge tanks and keeping the water heated for months.
This geothermal pump system installs in your existing well.
https://wellconnectgeo.com/
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NorthRick
Member
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# Posted: 1 Mar 2018 02:01pm
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Quoting: rockies I don't know why they don't use a geothermal heating system and just let the earth heat the water. Much less digging than burying huge tanks and keeping the water heated for months.
Permafrost. The ground is quite cold in Fairbanks and geothermal pump systems aren't all that efficient.
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