Ground Source Heating

[steveR]

If your pond water is only 1 degree, you are going to need circulating water at minus 3 to get any real pick up and preferably minus 5-6 .
Heat transfer is grossly affected by heat gradient.

Interesting facts.

I think it would be very interesting to drop a thermometer in our pond, fed by lands drains, and see what the temps look like through a winter at the base depth. Experience is that even in very cold weather, the water remains fluid and moving under a thin layer of top ice....

 

[suffolksmallholder]

Does not sound a lot to me 4 of 50m, it’s only 200m of pipe unless your in a bog with practically running water in the ground!!

It's a lot more than 200m! Last place a 2 bed cottage needed 2x40m ground loop place before that was air source c1987 and before that similar c1978 and worked for 30 years. These older units backed up 28 sec Potterton boilers. and saved approx a 500 gal tank each year.

I'm sure the folk who do this for a living have some redundancy built in and IMO there's about 6m of pipe in every metre of run. Trenches are 1.2wide to allow for a 1.0m diameter slinkie and 1.2 deep. I will scrape off 300mm first and keep this separate then do the actual dig. Yes 'food grade' glycol in the system. Heat transfer and all that.
13Kw Kensa unit with accumulator in a purpose-built plant room. The machinery should not be in a house as it buzzes like living in a kitchen/utility room with the fridge freezer
Just upgraded the machines QH with a Harford unit so no wobbly buckets now and I reckon to get one 50m trench out in a days work with lots of tea breaks.
SS

 

[Exfarmer]

Interesting facts.

I think it would be very interesting to drop a thermometer in our pond, fed by lands drains, and see what the temps look like through a winter at the base depth. Experience is that even in very cold weather, the water remains fluid and moving under a thin layer of top ice....

But were not on about 1 degree. Even if the surface of the pond is frozen the temperature below the surface is many degrees above freezing. You have been watching to many episodes of ice road truckers. We just dont get in the UK that duration of cold temperatures to freeze water at depth. The op is talking of a mill pond continually being filled with running water so it will never be as low as 1 degree.

The only figures I have come across are for the Avon at Trowbridge, indicating an average around 2.5C for December.
I would suggest January and February are likely to be lower.
Of course many factors are at play but this is when you are going to be asking for Max demand

 

[Mur Huwcun]

It's a lot more than 200m! Last place a 2 bed cottage needed 2x40m ground loop place before that was air source c1987 and before that similar c1978 and worked for 30 years. These older units backed up 28 sec Potterton boilers. and saved approx a 500 gal tank each year.

I'm sure the folk who do this for a living have some redundancy built in and IMO there's about 6m of pipe in every metre of run. Trenches are 1.2wide to allow for a 1.0m diameter slinkie and 1.2 deep. I will scrape off 300mm first and keep this separate then do the actual dig. Yes 'food grade' glycol in the system. Heat transfer and all that.
13Kw Kensa unit with accumulator in a purpose-built plant room. The machinery should not be in a house as it buzzes like living in a kitchen/utility room with the fridge freezer
Just upgraded the machines QH with a Harford unit so no wobbly buckets now and I reckon to get one 50m trench out in a days work with lots of tea breaks.
SS

We didn’t bother with slinkies as longer runs gives better ground contact area.Just dig them with a 4 foot bucket, top soil and turf on one side of trench, spoil on other side. Saves having to scrape top soil first. We dug ours out before lunch on day 1, mix of clay, soil and unfortunately some sandy gravel!!

 

[chickens and wheat]

Thats how mine were dug, 1m bucket 100m length 200m pipe up and down trench, subsoil back in topsoil back over, 40 trenches two mainfolds
Sept Oct 2019, rain nearly everyday ,very sticky wet subsoil ,boots heavy with it

 

[renewablejohn]

The only figures I have come across are for the Avon at Trowbridge, indicating an average around 2.5C for December.
I would suggest January and February are likely to be lower.
Of course many factors are at play but this is when you are going to be asking for Max demand

River temperature is easily available from Environ agency. Just picked this at random.

Photo Page/4 Pictures

 

[Exfarmer]

River temperature is easily available from Environ agency. Just picked this at random.

Photo Page/4 Pictures

Interesting, I would guess that there is a lot of variation across rivers with temp dependent on location flow and speed etc.
The winter 2019/2020 was of course the warmest on record, but certainly those figures would suggest you would have no issues

 

[renewablejohn]

Interesting, I would guess that there is a lot of variation across rivers with temp dependent on location flow and speed etc.
The winter 2019/2020 was of course the warmest on record, but certainly those figures would suggest you would have no issues

Click on the dates at the top and you have data for every year back to 2006. It really is an undervalued renewable heat source.

 

[suffolksmallholder]

We didn’t bother with slinkies as longer runs gives better ground contact area.Just dig them with a 4 foot bucket, top soil and turf on one side of trench, spoil on other side. Saves having to scrape top soil first. We dug ours out before lunch on day 1, mix of clay, soil and unfortunately some sandy gravel!!

I need to be careful of my land-drainage already in place hence the shorter wider system.
SS

 

[chickens and wheat]

We skimmed the top of the pretty old land drains, had to mend them in a few places

 

[Wisconsonian]

But were not on about 1 degree. Even if the surface of the pond is frozen the temperature below the surface is many degrees above freezing. You have been watching to many episodes of ice road truckers. We just dont get in the UK that duration of cold temperatures to freeze water at depth. The op is talking of a mill pond continually being filled with running water so it will never be as low as 1 degree.

Yes it will be "many degrees above freezing" if there is ground water moving through. Max 39 degrees F though, 3.98C, so if you can operate a heat pump on straight water with a freezestat at that, then I want to know what model of freezestat you recommend.

That is the inversion temperature of water, so any water warmer than that will rise up to the surface and prevent ice from forming. Below that temperature, water gets LESS dense down to the freezing point, where it's much less dense as ice. Without that peculiarity, lakes and oceans would melt from the top down, and there likely would be no life on earth, minor inconvenience.

Doesn't matter much whether the air temp is 0 or -40, if there's any ground water flow higher than the inversion temp, then there will be springs and dangerous ice in spots, and the deep water will be within a degree of that temperature.

 

[renewablejohn]

Yes it will be "many degrees above freezing" if there is ground water moving through. Max 39 degrees F though, 3.98C, so if you can operate a heat pump on straight water with a freezestat at that, then I want to know what model of freezestat you recommend.

That is the inversion temperature of water, so any water warmer than that will rise up to the surface and prevent ice from forming. Below that temperature, water gets LESS dense down to the freezing point, where it's much less dense as ice. Without that peculiarity, lakes and oceans would melt from the top down, and there likely would be no life on earth, minor inconvenience.

Doesn't matter much whether the air temp is 0 or -40, if there's any ground water flow higher than the inversion temp, then there will be springs and dangerous ice in spots, and the deep water will be within a degree of that temperature.

Totally irrelevant to the UK market, we do not have rivers that freeze over for weeks at a time. If you look at the river temperatures for a typical uk river (post 46) then there is always heat available for a heatpump. Not a heatpump engineer so cannot comment on your freezrstat comment just know of actual systems that have been in for over a decade with no freezing problems even when we had the beast from the east which was probably the coldest sustained period in the last decade.

 

[chickens and wheat]

Whats needed is a hydro turbine, generating leccy, running a heat pump using the flowing water as a heat source. All in one system runing 24/7.

 

[Wisconsonian]

Totally irrelevant to the UK market, we do not have rivers that freeze over for weeks at a time. If you look at the river temperatures for a typical uk river (post 46) then there is always heat available for a heatpump. Not a heatpump engineer so cannot comment on your freezrstat comment just know of actual systems that have been in for over a decade with no freezing problems even when we had the beast from the east which was probably the coldest sustained period in the last decade.

Plenty of smaller spring fed streams in this part of the northern US that would have enough heat to run a heat pump without antifreeze. maybe they do it with lakes also, I don't know. Pump and dump is just tolerated, anything to do with a water body would not get approval if you ask, so not a lot of info. 39F/4C is marginal in my mind without antifreeze.

I thought the question was about a small pond, not very deep. A relatively small flow through the pond will meet the load with a small temperature drop. No flow will freeze the pond and system up fast in freezing weather.