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#1 2019-11-23 10:19:14

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,222

Thermal heat storage

Most of us know about the use of stored heat in many forms. From the making of steam to hot water the range of temperatures as a means to do meaningful work. We know that solar heat can be save for later use and that we can concentrate that heat to higher temperature levels as well as to make use of the low temperature savings as well.

When you think about it its just another form of a flow battery only it does not put out a direct voltage as it needs to be comverted back from its saved source to electrical by pellitiers or turbines.

hybrid device captures heat from the sun and stores it as thermal energy

hybrid-molecular-storage-material-and-localized-phase-change-material-hg.jpg

It addresses some of the issues that have stalled wider-scale adoption of solar power, suggesting an avenue for using solar energy around-the-clock, despite limited sunlight hours, cloudy days and other constraints. The researchers report a harvesting efficiency of 73% at small-scale operation and as high as 90% at large-scale operation.

Up to 80% of stored energy was recovered at night, and the researchers said daytime recovery was even higher.
"During the day, the solar thermal energy can be harvested at temperatures as high as 120 degrees centigrade (about 248 Fahrenheit),"

Research papaer


HKU team invents Direct Thermal Charging Cell for converting waste heat to electricity

Low grade heat is abundantly available in industrial processes (80 to 150C), as well as in the environment, living things, solar-thermal (50 to 60C) and geothermal energy. Over 60% of the world's primary energy input, whether it is in the industrial process or domestic energy consumption, is wasted as heat. A majority of this loss as waste heat is regarded as low-grade heat.

The newly designed DTCC is a game-changing electrochemical technology which can open new horizons for applications to convert low-grade heat to electricity efficiently. It is a simple system with the basic unit sized only 1.5 sq.cm and thickness 1 to 1.5 mm. The cell is bendable, stackable and low cost.
The new thermal charging cell uses asymmetric electrodes: a graphene oxide/platinum (GO/Pt) cathode and a polyaniline (PANI) anode in Fe2+/Fe3+ redox electrolyte via isothermal heating operation without building thermal gradient or thermal cycle.

When heated, the cell generates voltage via a thermo-pseudocapacitive effect of GO and then discharges continuously by oxidizing the PANI anode and reducing Fe3+ to Fe2+ under isothermal heating on cathode side till Fe3+ depletion. The energy conversion works continuously under isothermal heating during the entire charge and discharge process. The system can be self-regenerated when cooled down. This synergistic chemical regeneration mechanism allows the device cyclability.

Research paper

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#2 2019-11-23 11:12:49

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,030
Website

Re: Thermal heat storage

Solar heat can be captured in water,  and used for space heating.  That's all low grade heat,  with a low-grade heat end use.  No conversion losses to speak of.  Not a waste of high-grade energy,  either. 

But I must say,  generating electricity from low grade heat has always been a very low-efficiency process heretofore (thermionic converters).  This might well be a breakthrough of sorts.  A 200-250 F range of heated fluid temperatures is achievable (see below).

In order to get solar-heated hot water temperatures over about 180-190 F here on Earth requires a modestly-concentrating collector,  meaning a simple flat plate collector with modest-sized adjacent mirror surfaces.  On Mars,  the mirrors need to be larger to overcome the 2:1 intensity deficiency.  That's still easily doable. 

But you still need to plan on what else to do when the sun doesn't shine,  be it night or dust storm.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#3 2019-11-23 14:43:12

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,222

Re: Thermal heat storage

The quantity since it can be increased with isolated tanks of all sizes allow for a flexible storage of temperature for the input from the collector. The reflective surface can be made from a mylar plastice matial that can be rolled out, then anchored to the frame that holds it in position for making the level of collected energy higher and so will the temperature of the working fluid dependant on the flow rate.

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#4 2019-11-25 06:41:42

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 478

Re: Thermal heat storage

The huge diurnal temperature fluctuations on Mars make this idea more workable there than it would be on Earth.  Assuming a daytime average temperature of zero Celsius and a night-time panel temperature of -50C, say, Carnot efficiency for a vapour cycle would be 18.3%.  A practical heat engine can get between half and two-thirds Carnot efficiency.  So a flat plate solar thermal power plant would get ~10% efficiency on Mars.

The Martian atmosphere is so thin that convective heat losses from panels will be negligible.  No cover glass would be needed.  Panels could be slabs made from concrete or clay with plastic pipes running through them.  A practical heat transfer fluid would be brine, containing concentrated chlorate salts.  The heat exchanger could also be made from thermoplastics and would consist of essentially a coiled hosepipe within a large tank of water or brine.  During the day, lightly salted ice-water would be melted in one tank by heat flowing from the panels at about zero C.  This tank will provide a hot source.  At night, a second tank containing concentrated brine would have heat removed through the panels and would freeze at -50C.  Insulation for both tanks would be provided by regolith.  The tanks could be nothing more complex than excavated holes lined with polyethylene sheeting.

A vapour generation cycle would run between the two tanks continuously, providing base load power.  Compressed CO2 would make a workable secondary power-cycle fluid.  Alternatively, there is SO2, ammonia, ethane, propane or various fluorocarbon compounds.

To cover outages resulting from dust storms, the tanks would need to be oversized to provide several weeks worth of storage.  There will be capital cost implications to this.  Overall, the system will be large but relatively low tech.  It will need valves and pumps on the primary (brine) side and valves, pumps, turbines, generators and liquid-vapour separators on the secondary CO2 vapour cycle side.  Lots of carbon steel on the secondary side; plastics on the primary side.

Power density will be limited by the amount of heat that the panels can dump into the Martian night.  Assuming a -50C working temperature for panel radiating as a black body, gives a panel thermal power density of 140watts.  The panel can only radiate at night, so time average thermal power density is 70w/m2.  Assuming a 10% electrical conversion efficiency gives a panel electrical power density of 7W/m2.  This is poor by most standards, but begins to look much better if panels can be made from clay and storage tanks are nothing more elaborate than polythene lined holes in the ground.  A 1MWe power plant would cover 143,000m2 or 36 acres.

To store 4 weeks worth of power, would require some 6720MWh (24million MJ) of thermal heat storage in each tank.  1 litre of water has latent heat of freezing of about 400KJ.  So each tank would need a volume of 60,000 cubic metres - a cube 39m aside.  That is a lot.  Especially considering that sourcing water from buried glaciers on Mars, will take about that same amount of energy as concrete manufacture on Earth.  Heat could be stored in solid rock by drilling bore holes.

Last edited by Calliban (2019-11-25 07:15:29)


Interested in space science, engineering and technology.

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#5 2019-11-25 07:30:03

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,854

Re: Thermal heat storage

Interesting ideas on an established theme.

I think manufacturing methane and oxygen when you have an energy surplus  is probably a quicker and better route to energy storage, since we will already be producing methane and oxygen for fuel-propellant. Methane and oxygen can be used directly for heating, for electricity generation or for transport power.

That said, the use of basic materials makes your proposal an attractive one.


Calliban wrote:

The huge diurnal temperature fluctuations on Mars make this idea more workable there than it would be on Earth.  Assuming a daytime average temperature of zero Celsius and a night-time panel temperature of -50C, say, Carnot efficiency for a vapour cycle would be 18.3%.  A practical heat engine can get between half and two-thirds Carnot efficiency.  So a flat plate solar thermal power plant would get ~10% efficiency on Mars.

The Martian atmosphere is so thin that convective heat losses from panels will be negligible.  No cover glass would be needed.  Panels could be slabs made from concrete or clay with plastic pipes running through them.  A practical heat transfer fluid would be brine, containing concentrated chlorate salts.  The heat exchanger could also be made from thermoplastics and would consist of essentially a coiled hosepipe within a large tank of water or brine.  During the day, lightly salted ice-water would be melted in one tank by heat flowing from the panels at about zero C.  This tank will provide a hot source.  At night, a second tank containing concentrated brine would have heat removed through the panels and would freeze at -50C.  Insulation for both tanks would be provided by regolith.  The tanks could be nothing more complex than excavated holes lined with polyethylene sheeting.

A vapour generation cycle would run between the two tanks continuously, providing base load power.  Compressed CO2 would make a workable secondary power-cycle fluid.  Alternatively, there is SO2, ammonia, ethane, propane or various fluorocarbon compounds.

To cover outages resulting from dust storms, the tanks would need to be oversized to provide several weeks worth of storage.  There will be capital cost implications to this.  Overall, the system will be large but relatively low tech.  It will need valves and pumps on the primary (brine) side and valves, pumps, turbines, generators and liquid-vapour separators on the secondary CO2 vapour cycle side.  Lots of carbon steel on the secondary side; plastics on the primary side.

Power density will be limited by the amount of heat that the panels can dump into the Martian night.  Assuming a -50C working temperature for panel radiating as a black body, gives a panel thermal power density of 140watts.  The panel can only radiate at night, so time average thermal power density is 70w/m2.  Assuming a 10% electrical conversion efficiency gives a panel electrical power density of 7W/m2.  This is poor by most standards, but begins to look much better if panels can be made from clay and storage tanks are nothing more elaborate than polythene lined holes in the ground.  A 1MWe power plant would cover 143,000m2 or 36 acres.

To store 4 weeks worth of power, would require some 6720MWh (24million MJ) of thermal heat storage in each tank.  1 litre of water has latent heat of freezing of about 400KJ.  So each tank would need a volume of 60,000 cubic metres - a cube 39m aside.  That is a lot.  Especially considering that sourcing water from buried glaciers on Mars, will take about that same amount of energy as concrete manufacture on Earth.  Heat could be stored in solid rock by drilling bore holes.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#6 2019-11-25 09:19:27

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 478

Re: Thermal heat storage

louis wrote:

Interesting ideas on an established theme.

I think manufacturing methane and oxygen when you have an energy surplus  is probably a quicker and better route to energy storage, since we will already be producing methane and oxygen for fuel-propellant. Methane and oxygen can be used directly for heating, for electricity generation or for transport power.

That said, the use of basic materials makes your proposal an attractive one.

Methane-oxygen synthesis for power production has extremely low cycle efficiency – about 5%.  I examined this in a previous thread.

Assuming that the intention is to provide small amounts of power only very occasionally – say 10% of baseload power, for a dust storm lasting a couple of months occurring once every two years; then it might be an affordable expense, especially if it can be tailed onto the existing propellant production process.  But it is wasteful in the extreme.  Like everything else, these sorts of decisions will be made on the basis of cost benefit analysis.

Long-term energy storage is always problematic, because it requires large amounts of energy storage that is utilised very poorly.  This has a terrible effect on the marginal cost of each kWh.  This is why renewable energy is proving so poorly effective at replacing fossil fuels for power generation here on Earth.  We can build pumped storage plants that balance supply over a period of hours, but it will never be affordable to store even 1 week of spare power in this way.  I suspect that the 'solution' to this problem will have more to do with going without; or maybe just finding an energy source that doesn't fluctuate with the weather.  Can anyone think of one?


Interested in space science, engineering and technology.

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#7 2019-11-25 10:55:14

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,854

Re: Thermal heat storage

Well I would envisage meth-ox production being tailored to a PV power approach. In those circumstances for things like agricultural and propellant production, probably the two biggest calls on power, you would "make hay while the sun shines" as the old proverb goes which means you don't attempt to maintain production levels when solar radiation dips to very low levels. In such circumstances you would cut back on production of food and propellant. That means two things: (a) you need to have a large food store to see you through major dust storms (not likely to be much of a problem in the early stages of colony development) and (b) you need a larger propellant production facility than you would with nuclear.

You'd probably only be looking to use maybe 10% of your average energy use through meth-ox production. Estimates of how much energy is required to sustain life and basic services vary but 10KwEs per person seems a popular figure (probably an overestimate in my view).  For a 10 person colony producing enough propellant to return to Earth in one Starship that would mean 100KwE or 10% of the total energy supply (1MwE).

Even the severest dust storms do not stop solar radiation entirely, so PV will still keep working, albeit at a reduced level. From what I have read, you are maybe getting an average 40% of normal or thereabouts over the life of a dust storm.

The reality is there are unlikely to be any periods when your PV system could not cover the emergency baseload figure. But of course, you need to plan for calamity, so you would need to arrive with a large meth-ox supply and begin building up your reserve. Meth-ox production is a bit like a savings account - you only have to have a slight surplus and the account will build and build until you have a very large surplus available.  A reasonable compromise would be to look to build an energy reserve of 245,000 KweHs per ten people  comprising meth-ox, chemical batteries and maybe pumped storage - enough to maintain 100 Kwes over 100 sols.   

I think on Mars we have an opportunity to explore the possibility of storing methane as clathrates. Could we create those and bury them on Mars in a shadowed area?

https://en.wikipedia.org/wiki/Methane_c … ercial_use




Calliban wrote:
louis wrote:

Interesting ideas on an established theme.

I think manufacturing methane and oxygen when you have an energy surplus  is probably a quicker and better route to energy storage, since we will already be producing methane and oxygen for fuel-propellant. Methane and oxygen can be used directly for heating, for electricity generation or for transport power.

That said, the use of basic materials makes your proposal an attractive one.

Methane-oxygen synthesis for power production has extremely low cycle efficiency – about 5%.  I examined this in a previous thread.

Assuming that the intention is to provide small amounts of power only very occasionally – say 10% of baseload power, for a dust storm lasting a couple of months occurring once every two years; then it might be an affordable expense, especially if it can be tailed onto the existing propellant production process.  But it is wasteful in the extreme.  Like everything else, these sorts of decisions will be made on the basis of cost benefit analysis.

Long-term energy storage is always problematic, because it requires large amounts of energy storage that is utilised very poorly.  This has a terrible effect on the marginal cost of each kWh.  This is why renewable energy is proving so poorly effective at replacing fossil fuels for power generation here on Earth.  We can build pumped storage plants that balance supply over a period of hours, but it will never be affordable to store even 1 week of spare power in this way.  I suspect that the 'solution' to this problem will have more to do with going without; or maybe just finding an energy source that doesn't fluctuate with the weather.  Can anyone think of one?


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#8 2019-11-25 17:01:29

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,222

Re: Thermal heat storage

Argue the methanol solar in the other backup topic, as thats not thermal storage....

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#9 2019-11-25 17:47:12

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,854

Re: Thermal heat storage

Fair enough! I know it's annoying when people drag your topic away from the thread focus. That said, I was responding to the idea that
a temperature range engine would be the best approach to energy storage. That I very much doubt. But I can see it would be better on Mars than on Earth. 

SpaceNut wrote:

Argue the methanol solar in the other backup topic, as thats not thermal storage....


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#10 2019-11-25 19:17:19

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,222

Re: Thermal heat storage

Trying to work numbers for if its going to work for mars.

https://science.howstuffworks.com/envir … -power.htm

Another method to concentrate the heat to be stored

xdish_receivers.gif.pagespeed.ic.BDWTYtghwn.jpg

Something else that we can do with heat
https://www.machinedesign.com/energy/in … nditioning

Here is the Methane backup not nuclear vs solar

This is the topic that void had put forth for Highly Transparent Aerogel/Getting more heat out of sunlight

We have lots of uses for mars heat once we generate it, collect it, store it...
Generation and Use of Thermal Energy in the U.S. Industrial Sector and Opportunities to Reduce its Carbon Emissions

https://www.eia.gov/energyexplained/sol … plants.php

https://energy.gov/eere/energybasics/ar … tem-basics

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#11 2019-11-26 18:14:25

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,222

Re: Thermal heat storage

To give louis an apology and a point back, that no matter what we choose to use for primary power there is always going to be a need for multiple backups for expansion and for a failed supply system.

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