Hi,
Here is an interesting geothermal project:
In the summer solar thermal collectors are used to heat the ground, and in the winter the heat is extracted from the ground:
"The temperature of the earth will reach 80 degrees Celsius by the end of each summer."
cheers, Jamie
Interesting. They only give the barest of details on how much energy they expect to provide to the homes. I believe they said the homes are construc ted to use 30% less energy and the solar heating system is expected to prov ide 90% of that. I believe they mentioned a total power output of the gara ges, 1.5 MW. They don't say how many homes/garages that is for. Google ma ps show 52 homes, so 29 kW per home. Obviously that's a peak number, I wond er what the factor is to get an average energy use per home?
The most interesting part is the seasonal storage of heat in the borehole s torage system. I'm surprised that can work efficiently over the winter. T hey don't talk at all about the storage capacity. Still, interesting claim s.
The homes have to be oriented to the sun, so rectilinear layout. They stan d out in a larger community with the typical curved streets and varied orie ntations.
-- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
The efficiency should go up with the effective volume (and storage capacity) of the thermal battery, as there would be a smaller fraction of heat lost (volume to surface area ratio).
One problem could be underground water flow, which could take a lot of heat out of the thermal battery. Putting the battery in a place that has a low year round water table would be necessary I guess.
Having deeper bore holes might be a way to reduce the required insulation on the surface, ie since the surface is only about 1/6th of the surface area of the thermal battery, there is not a lot to be gained by insulating the surface rather than just increasing the depth of the boreholes and depth of the thermal battery.
Also the type of solar collectors could be different, maybe it is cheaper to use mirrors and a heating tower etc.
cheers, Jamie
That's an insane amount of hardware to heat 52 homes. I wonder who is paying for this "energy showcase."
-- John Larkin Highland Technology, Inc The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
Apparently the Federal government of Canada paid for it through NRCan.
If you visit alberta you can compare this amount of hardware to the oilsands hardware for context.
cheers, Jamie
le storage system. I'm surprised that can work efficiently over the winter . They don't talk at all about the storage capacity. Still, interesting c laims.
That goes without saying, but even so, I'm surprised this could store heat from summer to winter. That's a lot of heat and a lot of time.
Sure, again that goes without saying. 100 foot wide and 115 feet deep. Th at's a lot of thermal mass. I'm just surprised it is large enough to store heat for a winter. But I'm sure they've done their homework.
I would expect that unless there is a limit on land used, they would try to minimize the surface area by keeping the volume close to round. Notice th ey cut the corners from the bore hole pattern. I'm sure they insulated the surface rather than just burying the whole thing in more dirt because that is the most economical.
It's a community. Aesthetics!
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What so special about this ? There are a lot ground loop heat pump installation, in which a large ground loop is installed 1-2 m below ground in the garden. While some people call this "geothermal" but it is just seasonal storage. The ground is heated in the summer and that heath energy is extracted in the winter. The snow cover in the winter reduces the heat loss directly from the ground.
If the garden is too small and too much heat is extracted from the ground, the ground temperature may fall below 0 C, in the spring freezing the ground and nothing will grow in the garden during the early summer. Some house owners dump air condition heat in the summer into the ground loop, melting the garden soil and enabling plant growth. If a solar thermal collector is added to the system, it can be used to heat the house earlier in the spring and also earlier dump some heat into the ground loop, making it possible to start the growing season earlier.
With a larger garden loop, there is not even a risk for freezing the ground towards the spring.
That is insane. If dumped into the soil, it dry up the soil completely. If some wells drilled into the ground water that would be a very bad idea, since the heat would flow away and may be illegal if ground water is used for drinking water in the area.
,
This is probably the solar collector (800 of them for 52 houses, about
15 panels per house) used:They are flat plate collectors, not the evacuated tube type.
cheers, Jamie
Hi,
The thermal battery with solar collectors doesn't require a heat pump as long as the thermal battery temperature is high enough, 80 Celcius max temperature at the start of winter, and maybe the thermal battery is at
30Celcius by the end of winter.cheers, Jamie
I've never heard anyone say heat pump geothermal is intended to store energ y in the ground. Rather it uses the ground as a heat sink which is at a be tter temperature than the air which improves the efficiency of the heat pum p. If the ground temperature changes much it would defeat the advantages o f the constant temperature heat sink.
I also don't think the few feet of earth on top would be adequate insulatio n for seasons.
Why would the ground be frozen in the summer??? Around here the garden is growing earlier than the heat is turned off.
Don't you think they've considered water???
-- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
hole storage system. I'm surprised that can work efficiently over the wint er. They don't talk at all about the storage capacity. Still, interesting claims.
eat from summer to winter. That's a lot of heat and a lot of time.
That's a lot of thermal mass. I'm just surprised it is large enough to s tore heat for a winter. But I'm sure they've done their homework.
ed
y to minimize the surface area by keeping the volume close to round. Notic e they cut the corners from the bore hole pattern. I'm sure they insulated the surface rather than just burying the whole thing in more dirt because that is the most economical.
I get a 26 foot sphere. Divide 100 feet by the cube root of 52 or 3.7.
There is going to be more loss for a smaller sphere no matter what. But wh y would you think this is a good solution for a single home? I expect this only works if you can apply an economy of scale.
-- Rick C. -+ Get 1,000 miles of free Supercharging -+ Tesla referral code - https://ts.la/richard11209
Oops, that sounds correct, I forgot I was using radius.
What thermal loss would the 26 foot sphere have compared to a 100 foot sphere? If it is within 2x or 3x, it is still interesting to consider possibly, although a standard geothermal heat pump would be simpler and cheaper.
For a single house maybe instead of 15 panels, 30 panels would be required to account for larger thermal battery losses in a 26 foot sphere. That is a large up front cost, but has some advantages by not having a heat pump, also the solar collector panels could be cheaper (molded plastic types) in the future or integrated into roof.
Also for a single home, having the thermal battery under the basement of the house might increase the overall efficiency etc.
cheers, Jamie
>
Another way to do a single house more efficiently could be to lower the thermal battery temperature and make it larger, ie instead of a 80 Celcius max, 26 foot diameter, it could be 50 Celcius max, ~35+ foot diameter. This has a more shallow temperature gradient and also would make the roof solar collectors more efficient to operate at a lower temperature, so more heat could be pumped into the thermal battery.
The working fluid pump rate would have to be increased for winter heating as the fluid temperature is lower, but as long as it stays above 30C or so it should work.
cheers, Jamie
d
rgy in the ground. Rather it uses the ground as a heat sink which is at a better temperature than the air which improves the efficiency of the heat p ump. If the ground temperature changes much it would defeat the advantages of the constant temperature heat sink.
ion for seasons.
If I remember rightly, the temperature 45cm below the surface lags the seas ons by six months (or 180 degrees) which is exactly what you want.
A few feet of earth would be a bit more than that ...
A shallow-rooted plants would grow fine.
s growing earlier than the heat is turned off.
Finland is a chilly place.
Depends where the water table is. Getting the soil dry would be a neat tric k in a lot of places - the water vapour would move down as well as up.
Bore water comes from quite a bit further down.
-- Bill Sloman, Sydney
Rick C wrote in news: snipped-for-privacy@googlegroups.com:
Geothermal is great except for being on unstable ground in most cases.
I think a better choice for a heat boost to a steam system would be the interior of a huge salt dome. They are very hot, and very stable. It is like a huge golf tee the size of Everest buried in the ground. Within its heart is a hot core.
Also, I suggested this nearly twenty years ago.
as
t why would you think this is a good solution for a single home? I expect this only works if you can apply an economy of scale.
The thermal loss would be proportionally 3.7 times larger than the 100 foot sphere assuming all losses are relative to the surface area.
A geothermal heat pump will save money, but it won't reduce the energy cons umption by 90%. That's an impressive number. With the emphasis on reducin g the carbon footprint it's ironic that they burn gas as the backup heat fo r the 10%. I'm not sure if a geothermal unit will even cut your electric u se by 50%. It is supposed to pay for itself.
I don't know how expensive the thermal collection panels are. I have alway s heard that solar hot water is a better financial proposition than solar P V, but that likely has been mitigated by the relatively recent reductions i n cost of solar PV.
Not if you ever need to dig it up for repair!
I think to get seasonal storage of energy it would require both more solar collectors and a larger size of the bore hole storage system. Double the c ollectors and you likely need to double the capacity of the storage, or 25% larger diameter than we figured before, 34 feet now.
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and
nergy in the ground. Rather it uses the ground as a heat sink which is at a better temperature than the air which improves the efficiency of the heat pump. If the ground temperature changes much it would defeat the advantag es of the constant temperature heat sink.
ation for seasons.
asons by six months (or 180 degrees) which is exactly what you want.
Not really. It is an irrelevant statistic. The issue at hand is heat loss . The fact that the thermal losses in winter cause the temperature to turn around in mid winter is not the important aspect. Consider the amount of insulation that will cause that effect, then add more insulation and you ha ve a better storage system even though the temperature peak is now a differ ent time.
And a better insulator.
is growing earlier than the heat is turned off.
Non sequitur. Now you sound like JL.
-- Rick C. ++ Get 1,000 miles of free Supercharging ++ Tesla referral code - https://ts.la/richard11209
80 C does seem crazy, I wonder if it comes close in practice? I would like to see some analysis, but storing energy as heat looks inefficient to me... why not PV and run heat pumps from the 50 F/ 10 C ground temperature (water?) to heat in winter and cool in summer. (You'd need batteries for the PV's.)
George H.
It talks about heavy insulation. I can't imagine that dumping heat into the ground would be very efficient (over the span of seasons) unless you had very good insulation to keep the heat from flowing away.
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energy in the ground. Rather it uses the ground as a heat sink which is a t a better temperature than the air which improves the efficiency of the he at pump. If the ground temperature changes much it would defeat the advant ages of the constant temperature heat sink.
ulation for seasons.
seasons by six months (or 180 degrees) which is exactly what you want.
ss. The fact that the thermal losses in winter cause the temperature to tu rn around in mid winter is not the important aspect. Consider the amount o f insulation that will cause that effect, then add more insulation and you have a better storage system even though the temperature peak is now a diff erent time.
The point is that the earth is both a thermal mass and an insulator. The po int about the six month thermal lag 45 cm below the surface references both aspects, even if you haven't noticed this.
Upside@downunder lives in Finland, which I happen to know, even if you don' t.
You would have had to read a few of the posts with that header to notice, w hich I've done, even if you haven't.
-- Bill Sloman, Sydney
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