Seasonal heat storage under existing house

osolemio · 05-21-10, 03:40 AM

In conjunction with my escalating energy and resource renovation of my 30 year old house, I am using the existing mass of clay and dirt under the house as a long term heat storage.

To begin with, this house is not insulated underneath anywhere near 2010 standards. The floating wooden floor is directly attached to the original 3 inch concrete layer. Underneath this is gravel and some pebble called "Leca", they are somewhat insulating but not much, especially in this rather thin layer. There is no insulation at all downwards in the form of rockwool, styrofoam or similar.

I am turning this around, to my advantage here.

A solar power system is often underutilized because most of the heat required is in the range of 110F to 150F. Often, the solar panels will be less than 110F, either because the hot water has been heated enough already, or because the sun is less powerful, being overcast, winter or similar.

In these cases, the remaining solar heat cannot normally be used. All the while, the ground temperature underneath the house is quite stable around 45-55F or so.

Linking these two together means using solar energy which is normally too low grade to be absorbed by traditional means. If the heat could only be exchanged from the solar panels and underneath the house, much more of the excess heat could be stored.

This also solves another problem associated with most solar power installations: Most demand for space heating is during wintertime, while it is in largest supply during summer. Inserting the heat at the right depth, insuring the surrounding area is not infringed by water ores and making sure the sides are insulated and screened against rain water, there is a massive heat capacity. The slow speed of radiating this heat means that heat stored during summer and fall will remain during winter and even partly into the spring. The rate of depletion will depend on many factors, including ambient temperature, insulation of the house and foundation, how much heat is stored during summer, the nature of material underneath the house ... and so on.

Building a new house, this "annual geo solar" principle (See Wiki/Google) can be applied before even building the house. Modifying an existing house is somewhat more difficult, but however part of my solution. Here is what I have done so far ...

Whilst I had dug a hole in front of my house, for a 70 sq feet expansion, I installed three water tanks for short term added heat capacity (days or weeks). The tanks are second hand HDPE pallet tanks, 1050 Litres each (about 290 USG). Before I actually installed these tanks, I had a specialist company install three pipes underneath the house. These pipes are about 3 inch diameter, 30 feet long each, and made for underground piping like water pipes and similar. They are capable of quite high pressure and welded tight.

Since I was not going to dig a hole on the other side of the house, I had the tubes capped off before they were inserted. They shoot an air driven "rocket" underneath the house, then insert the pipes. Inside the 3 inc pipes are a 1 1/4 inch pipe, all the way to the end, and outside, I had them make a special fitting which will split the inner and outer tube into two, so I can pump water in the inner pipe, and it will then return in the outer pipe.

This way I can have circulation inside a "dead end pipe" all the way through. Since I have three of these pipes now, I have a total of 90 feet of 3 inch pipe under the house, at a depth starting at 4 feet, ending around 8 - 10 feet at the other end.

In my solar circuit I now have the ability to further cool down the solar liquid before returning it to the solar panels. I can bypass any heat storage in the system, even the solar panels if I should need to, so I can even transfer heat from the solar panels directly under the house and back. This would be useful on a lazy winter day where the solar panels do not reach sufficient temperatures for water or space heating. During the summer, if all other heat storage is full, I can do the same - route all heat under the house.

The mass is massive, so it takes ages to heat it up, I know ... but what comes in, must come out, slowly, and it will do so. If I got the delay right, I should have most of the heat dissipate upwards during the cold season.

I hope you guys find this interesting.

I am really solving several problems above:

1) Using heat which is normally too low grade to be used at all
2) Removing excess heat from solar panels in the summer
3) Storing heat from summer and fall into the winter and early spring

Daox · 05-21-10, 08:08 AM

It sounds like a good idea to me. I've heard of annual heat storage before and love the idea!

My only concern would be heating the ground under the house might work too fast and heat your house up during summer.

05-21-10, 03:40 AM	#1
osolemio Hong Kong Join Date: May 2010 Location: Hong Kong Posts: 108 Thanks: 20 Thanked 17 Times in 13 Posts	Seasonal heat storage under existing house In conjunction with my escalating energy and resource renovation of my 30 year old house, I am using the existing mass of clay and dirt under the house as a long term heat storage. To begin with, this house is not insulated underneath anywhere near 2010 standards. The floating wooden floor is directly attached to the original 3 inch concrete layer. Underneath this is gravel and some pebble called "Leca", they are somewhat insulating but not much, especially in this rather thin layer. There is no insulation at all downwards in the form of rockwool, styrofoam or similar. I am turning this around, to my advantage here. A solar power system is often underutilized because most of the heat required is in the range of 110F to 150F. Often, the solar panels will be less than 110F, either because the hot water has been heated enough already, or because the sun is less powerful, being overcast, winter or similar. In these cases, the remaining solar heat cannot normally be used. All the while, the ground temperature underneath the house is quite stable around 45-55F or so. Linking these two together means using solar energy which is normally too low grade to be absorbed by traditional means. If the heat could only be exchanged from the solar panels and underneath the house, much more of the excess heat could be stored. This also solves another problem associated with most solar power installations: Most demand for space heating is during wintertime, while it is in largest supply during summer. Inserting the heat at the right depth, insuring the surrounding area is not infringed by water ores and making sure the sides are insulated and screened against rain water, there is a massive heat capacity. The slow speed of radiating this heat means that heat stored during summer and fall will remain during winter and even partly into the spring. The rate of depletion will depend on many factors, including ambient temperature, insulation of the house and foundation, how much heat is stored during summer, the nature of material underneath the house ... and so on. Building a new house, this "annual geo solar" principle (See Wiki/Google) can be applied before even building the house. Modifying an existing house is somewhat more difficult, but however part of my solution. Here is what I have done so far ... Whilst I had dug a hole in front of my house, for a 70 sq feet expansion, I installed three water tanks for short term added heat capacity (days or weeks). The tanks are second hand HDPE pallet tanks, 1050 Litres each (about 290 USG). Before I actually installed these tanks, I had a specialist company install three pipes underneath the house. These pipes are about 3 inch diameter, 30 feet long each, and made for underground piping like water pipes and similar. They are capable of quite high pressure and welded tight. Since I was not going to dig a hole on the other side of the house, I had the tubes capped off before they were inserted. They shoot an air driven "rocket" underneath the house, then insert the pipes. Inside the 3 inc pipes are a 1 1/4 inch pipe, all the way to the end, and outside, I had them make a special fitting which will split the inner and outer tube into two, so I can pump water in the inner pipe, and it will then return in the outer pipe. This way I can have circulation inside a "dead end pipe" all the way through. Since I have three of these pipes now, I have a total of 90 feet of 3 inch pipe under the house, at a depth starting at 4 feet, ending around 8 - 10 feet at the other end. In my solar circuit I now have the ability to further cool down the solar liquid before returning it to the solar panels. I can bypass any heat storage in the system, even the solar panels if I should need to, so I can even transfer heat from the solar panels directly under the house and back. This would be useful on a lazy winter day where the solar panels do not reach sufficient temperatures for water or space heating. During the summer, if all other heat storage is full, I can do the same - route all heat under the house. The mass is massive, so it takes ages to heat it up, I know ... but what comes in, must come out, slowly, and it will do so. If I got the delay right, I should have most of the heat dissipate upwards during the cold season. I hope you guys find this interesting. I am really solving several problems above: 1) Using heat which is normally too low grade to be used at all 2) Removing excess heat from solar panels in the summer 3) Storing heat from summer and fall into the winter and early spring __________________ Space heating/cooling and water heating by solar, Annual Geo Solar, drainwater heat recovery, Solar PV (to grid), rainwater recovery and more ... Installing all this in a house from 1980, Copenhagen, Denmark. Living in Hong Kong. Main goal: Developing "Diffuse Light Concentration" technology for solar thermal.

05-21-10, 08:08 AM	#2
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	It sounds like a good idea to me. I've heard of annual heat storage before and love the idea! My only concern would be heating the ground under the house might work too fast and heat your house up during summer. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.