Thesis On Storage Heaters (& Other Storage Technologies)
Posted 16 August 2015 - 08:59 PM
"ELECTRICAL STORAGE HEATER IN THE CONTEXT OF STORAGE TECHNOLOGIES. Author: Ignacio Becerril Romero"
I found it very interesting. Maybe some others might too?
Posted 16 August 2015 - 09:45 PM
Posted 17 August 2015 - 01:08 PM
Posted 17 August 2015 - 01:46 PM
Density SHC Thermal Density
kg/m3 J/K.kg J/K.m3
Brick 2000 840 1680000
Concrete 2400 880 2112000
Plaster and plasterboard 2700 1080 2916000
Water 1000 4200 4200000
Structural softwood 550 1700 935000
Typical hardwood 700 1700 1190000
Granite 2700 790 2133000
Brick 1800 840 1512000
Magnetite 5177 752 3893104
The table looks perfect in the editor (Font: Courier New), but as soon as I post the formatting is lost - looks a proportional font?
Is there a better way of posting tables on this Forum than selecting a non-proportional font? I tried "Post from Word" (actually from LibreOffice) which looked encouraging but after posting lost all formatting & I tried BB code, but that wasn't recognised. I tried CODE, but that also seemed to use a proportional font. I didn't try raw html.
Maybe it's just the Firefox in Ubuntu that I'm using & others see it okay?
Edited by DavidWright, 17 August 2015 - 01:51 PM.
Posted 17 August 2015 - 02:35 PM
Not read the article, do we know what they are made from?
Posted 17 August 2015 - 05:11 PM
From the thesis (N.B. I think "TES" is an abbreviation for "Thermal Energy Storage", I haven't noticed it being defined, but that makes sense across a wide range of uses in the Thesis):
used to talk about high density ceramic magnetite (Fe3O4).
Magnetite is frequently used for TES applications due to its high volumetric heat
capacity and good thermal stability at high temperatures (Gronvol and Sveen, 1974;
Otero and Álvarez, 1994). Further materials employed in heat storage applications are
other iron oxides, magnesia (MgO), alumina (Al2O3) and silica (SiO2). However,
because of the lower cost of raw materials and their superior thermal properties, iron
oxides and magnesia are the best candidates for the fabrication of thermal storage bricks
Posted 18 August 2015 - 08:37 AM
I had a quick look around and it seem that the SHC is 103.9 J/mol·K, and I think that works out at about 3.2kJ/kg (I may have misunderstood the conversion though).
So almost as good as water and don't change phase (melt) until it is 1500°C
Posted 18 August 2015 - 09:21 AM
Last year we used 3MWh of gas, ie ~1E10J, for space and water heating.
So at 3893104 J/K.m^3 and (say) at least a 1000C temperature delta (shall I buy shares in Aspen Aerogel now?) that gives me 3.9E9J/m^3 or somewhat under 3m^3 of magnetite to hold the energy for a seasonal store.
Somewhat less of a size issue than a buried water-filled milk tanker or three on my small plot, but ripe with its own health-and-safety issues.
And we don't really have 3MWh of electricity to spare (we generated just under 4MWh last year and used about 1.7MWh as electricity) but not utterly implausible. Nominally with a heat pump the exported electricity would cover our low-grade heat requirements over the year.
Could it be done?
Have I made some horrible order-of-magnitude error?
PS. And at those high temperatures would the store be worth tapping for a little electrical energy, eg for lighting at night, with a Seebeck device?
Edited by joiner, 18 August 2015 - 11:03 AM.
"mind" for "might"
Posted 18 August 2015 - 11:05 AM
The study looks at using domestic "smart" storage heaters within their design spec. (and quite possibly in places where electric heating might be being used anyway - not all are on the gas grid & not all think that burning stuff is a sensible way of generating heat).
From the abstract of the thesis...
in small isolated grids with significant wind generation. The charging periods of the
heater can be scheduled by the utility provider based on wind output and demand
Big efficient batteries would be great for storing excess electricity, but they aren't here yet...
Edit: Tweak the 1st para.
Edited by DavidWright, 18 August 2015 - 01:18 PM.
Posted 18 August 2015 - 03:30 PM
Edited by joiner, 18 August 2015 - 03:50 PM.
Posted 18 August 2015 - 04:25 PM
There's no gas grid up here & optimising use of the energy produced in the area across the day means reduced transmission losses compared to pushing excess hydro (& nowadays, wind) down the country during the day & pulling (mainly) non-renewable E7 back over night.
Edited by DavidWright, 18 August 2015 - 04:26 PM.
Posted 18 August 2015 - 04:31 PM
The astonishing thing for me is that the magnetite starts to get into the seasonal storage arena. I'd completely failed to realise that its extended temperature range compared to water means that it may be possibly to store several times more for a given weight and volume.
Posted 18 August 2015 - 09:09 PM
Posted 18 August 2015 - 09:20 PM
Seebeck devices are such a wonderful idea. It's just a shame they're so inefficient.
I did see something a while back about a device that looked like giving three or four times the typical efficiency (edited to add: found it: http://www.gizmag.co...material/24210/).
I'd love to see cheap, efficient Seebeck films that could be used anywhere there's waste heat. The back of solar panels is one application: panel cooling that improves PV efficiency while producing its own energy!
Edit: link + added to final sentence
Edited by notnickclegg, 18 August 2015 - 09:31 PM.
Posted 18 August 2015 - 09:30 PM
No sure how hot an electrical element can get (could always strike and arc I guess). But you could use a sterling engine with a large enough high temperature heat store. Or a small steam turbine.
It may be worth looking at the fluctuation in electrical energy demand and seeing how well that count be matched to domestic thermal energy demand (thermal can be times-hifted quite well in my opinion).
I think they could do more with the radio signal, but they want to reinvent the wheel with smart meters (all gone a bit quite on the roll out recently).
Posted 19 August 2015 - 03:18 PM
More about RTS/Teleswitch: https://en.wikipedia...adio_teleswitch
N.B. The bit about "Transmitter Obsolescence"!