ᐅ Experiences with Ground Source Heat Pumps

Created on: 23 Oct 2015 21:40
S
Saruss
Hello,
here I would like to share some experiences and data regarding my brine heat pump and deep drilling, based in part on the expert’s "questionnaire":

a) What is the soil composition on your property?
Up to 3m (10 feet) silty, fine sandy, clayey soil
Up to 4m (13 feet) slope debris, rock fragments
Then bedrock (mainly limestone)

b) How deep was the drilling?
Drilled twice to a depth of 72m (236 feet)

c) How much did the drilling cost?
€10,400 including double U-probes DN25
Grouting material with 2.0 W/mK thermal conductivity
Permitting process (building permit / planning permission)
Pressure-tight house entry at the basement and underground routing of supply lines (about 25m (82 feet))
Filling/draining equipment, filling, pressure testing, etc. (all inclusive)

d) How much did the system cost?
System: Tecalor TTc 05 with heating output at B0/W35 of 5.8 kW and coefficient of performance (COP) of 4.8
Cost: €9,800

e) Were there any difficulties during installation, if so, what kind?
Because the water used to flush out the drilled material during drilling seeped away, a "small compressor" was needed to blow it out with air. However, it had to be placed on a neighbor’s property who had not yet started building. The machine was the size and approximate weight of a 20-ton truck but was off-road capable. This caused a 2-day delay because the compressor first had to be transported to our site. No additional costs were charged.

f) How is the daily operation?
"Like a refrigerator." Once the parameters on the heating system are correctly set, the only thing that should be done is occasionally reading the information/data such as operating hours and source temperature. Otherwise, it runs "on its own," just like any heating system. When the door is closed, the unit is virtually inaudible. Very discreet since, apart from the cabinet in the utility room, nothing else is visible (all brine pipes are underground).

e) What are the operating costs for which living area?
Currently, a living area of 180sqm (1937 sqft) is heated, plus an additional 65sqm (700 sqft) of cellar space within the insulated thermal envelope (these rooms are around 15-16°C (59-61°F) on the coldest days). From September 2014 to September 2015, 2,000 kWh of electricity was consumed for heating and hot water (2 adults, 1 baby, 1 toddler). The house is a KfW-70 standard building according to the 2009 energy saving regulations, which already met the required technical standards before the central ventilation system with enthalpy heat exchanger was installed (we decided to add this after the initial applications).

f) to be continued ....

Note regarding the comparison of the coefficient of performance (COP):
Since optimizing the heating curve and settings at the end of last year, the system has had a COP of about 5.5. Operating hours are around 1200; the deep borehole was drilled approximately 20% deeper than initially recommended by the companies, at our own request.
L
Legurit
8 Jan 2016 21:08
Either you live on a hot spring, or something is wrong on my end.
The coefficient of performance isn’t that bad.
S
Saruss
8 Jan 2016 21:43
I am sitting on a limestone plateau. There is little surface water here and no hot springs. Possibly, the permeability for water improves the rock’s ability to regenerate, but it was impermeable enough to allow drilling and filling. In my case, with the improved filling (meaning higher thermal conductivity), maybe this affects the cycles – with you, the area near the pipes might regenerate a bit more slowly.

As long as your antifreeze concentration is appropriate and the brine does not continuously drop until it’s no longer viable, it’s still manageable. The heat pump is designed for this temperature range.
L
Legurit
8 Jan 2016 21:55
You may be right – perhaps it is also too early for a judgment.
C
cumpa
19 Feb 2016 01:59
Saruss... how many square meters are you heating in total? And what is the kilowatt rating of your heat pump?
S
Saruss
19 Feb 2016 06:07
... See post no. 1
C
cumpa
19 Feb 2016 08:25
Is the 65sqm (700 sq ft) basement unheated or partially heated? Do you have a door to the basement or is it an open staircase?