Cold Climate Solar Heating system - Long term Thermal Storage

[peakbagger]

Forget our puny 1000 gallon storage tanks

792352_DSHWhitepaper_111920 (netdna-ssl.com)

Its sort of like a solar assisted geothermal system. My guess is the initial capital cost would need to be compared to a conventional geothermal system tied to a low temperature emitter system like radiant or the Euro emitters.

I have seen attempts in the past to do this with cooling where a large block of ice is formed in an insulated pit using natural convection of refrigerants in cold weather. The coils outside are higher than the buried tank so whenever the outdoors is colder than the interior of the tank the refrigerant circulates by convection to form a huge block of ice. Then when there is cooling demand there are coils at the base of block with antifreeze in them that get pumped up to an air handler.

 

[clancey]

My My now they are using earth to store energy in as well as having cold air in the heat---I would hate to have that repair bill and could it be made for small houses and would not it be better to place under the soil somewhere else besides under a building and with insulation transfer it to the living space....Future coming...thanks clancey

 

[peakbagger]

Long term thermal storage was incorporated in many low energy buildings in the eighties. Few systems worked as intended. Many became liabilities in Northern New England as the thermal storage frequent was coarse crushed rock or concrete, both sources of radon direct to the interior of the home.

 

[blades]

Radon was never a particular problem till we started to seal up our homes. Maybe those big old leaky places went so far of the mark.

 

[begreen]

Radon was never a particular problem till we started to seal up our homes. Maybe those big old leaky places went so far of the mark.

Radon was in homes long before it was first noticed and likely was the cause of many cancers. This is a fairly recent discovery and it was found by accident.

The Story of How Radon was Discovered in Homes

Who is Radio Active Stanely? In January of 1984, Stanely Watras and his young family moved into their new home in Boyerstown, Pennsylvania. Stanely began

www.brickkicker.com

 

[ABMax24]

I might have posted this before, but there was a system setup in Alberta in 2007 for a 52 house subdivision to be heated year round with solar heating, storing the heat down a series of boreholes.

Capturing the Solar Thermal Energy: DLSC

www.dlsc.ca

 

[tom in maine]

Cal MacCracken was a solar innovator who eventually started Calmac. They make cold storage systems using off peak energy in urban cooling climates. He was at a trade show in 1990 and came up to me to ask about liners. I thought he was trying to pirate our tanks until I saw his nametag. I had read a paper on a passive cold storage system he did in Illinois. He dug a hole, did not insulate it and put a liner in the ground, backfilling with tubing. He had a radiator of sorts in the cold winter air which would allow heat to come out of the ground and freeze the backfill. They used it for cooling except the liner leaked and rain water got in and melted the ice prematurely.
The concept seems valid if one has a backhoe (HEY, I just got one!!) and some time to run some numbers. Not sure it is worth the time and investment, but digging holes in the yard is a manly art and seems worthy of one's consideration. And the storage numbers do make sense.

 

[peakbagger]

Commercial ice storage is viable technology for covering day to day and even several days of cooling but the units of cooling gives a hint that it takes a lot of water to store not so much cooling. One standard unit of cooling is tons of cooling. Its should actually be Tons per hour but the hour is usually assumed. This is 12,000 BTUs/hr of cooling or the btus stored in ton 2000#s of ice if it melts in an hour. That is roughly a 3' cube of ice. Figure out how many tons of cooling needed for an entire cooling season and that is lot of ice. Its actually far worse for heating. Most of the energy in ice is stored in the latent heat of fusion 144 btus/lb. This is hidden cooling, its the energy required for the solid ice to turn to water. Then there is a relatively trivial amount of heat stored from the difference of the ice temp and the temp of the space being cooled which is 1 btu/lb per degree F. In the case of storing heat with water, there is no easy equivalent to the latent heat of fusion as the next state of water of liquid water is steam. The latent heat of vaporization of steam is around 1000 btus per pound but storing steam long term is not cheap or easy. The energy in the latent heat of fusion was the predominant means of powering society for the last couple of hundred years and even standard design nuclear power plants still use the approach.

In the case of geothermal the trick is the ground is huge mass and if there is enough surface area to the means of collecting heat, the heat will flow into of out of the coil at a constant temp. Go cheap with the coil and undersize it and the ground around the field will slowly heat up or cool down over the course of heating and cooling season.

Ideally the best heating and cooling is the heating and cooling not needed to have because of good insulation and the careful use of thermal mass and solar radiation.

 

[ABMax24]

Ton is measured over a 24hr period.

ie a 12,000BTU AC unit operating for 24 hrs is the equivalent of melting 2000lb of ice.

 

[peakbagger]

https://en.wikipedia.org/wiki/Ton_of_refrigeration

I was half right ;( AC ton is 12,000 Btu per hour but its based on a ton of ice melting over 24 hours so my volume is off by 1/24