Geothermal
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Ground source heat pumps (GSHP) are an increasingly popular option for delivering low-carbon space heating (and cooling) for commercial, public and domestic buildings.
The principle of ground source heat pump technology is long-established and is based on the same process as the common domestic refrigerator. A quantity of thermal energy is removed from one source and transferred to another. In the case of a refrigerator, the energy is removed from the inside of the appliance (cooling the air inside as a consequence) and transferred to the heat dissipation coils on the back of the cabinet. In the case of GSHP, the energy is removed from the ground and transferred into the interior of a building. In both cases the energy source becomes chilled, and the energy sink is warmed.
Which system to choose?
There are two principal methods for supplying thermal energy to the source-side loop in GSHP applications:
(a) Closed loop systems, in which the source-side loop is long, and is buried in the earth, either: i. as coils of HDPE pipework to depths of > 1.5m in cut-and-fill trenches, or ii. suspended in vertical boreholes.
(b) Open loop systems, in which the source-side loop is covered in pumped groundwater, which is typically re-pumped to the subsurface via another borehole well after passing through the heat pump.
In both cases, the energy source generally approximates to the local average annual air temperature, which in the lowland UK is typically between 10°C and 12°C. The fluid in the source-side loop will typically be chilled to around 6°C after passing through the heat exchanger. The exchanger typically delivers heat at around 55°C. The system can be coupled to closed circuits of water pipes supplying conventional 'wet' radiators or underfloor heating systems. The under floor heating been the system far better suited to ground source heat pump applications.
Open Loop Geothermal Systems
An Open Loop System involves pumping water from an existing source, perhaps a river or a lake, but more often via boreholes that are drilled to access water sources below ground for efficiency
The water either travels directly to the integral Heat Pump or more commonly via a Plate Heat Exchanger.
An Open Loop System involves pumping water from an existing source, perhaps a river or a lake, but more often via boreholes that are drilled to access water sources below ground for efficiency.
The water either travels directly to the integral Heat Pump or more commonly via a Plate Heat Exchanger.
All Open Loop Systems using over 20m3 of groundwater per day are subject to lengthy and complex Environmental Agency (EA) Regulations. The EA are reasonably relaxed about Open Loop Groundwater Systems if spent water is returned to the aquifer from which it was taken, meaning that net permanent consumption is relatively small.
It must be demonstrated to the EA that the System is not going to affect an existing user of groundwater in the vicinity of the Project and that it offers no potential threat to the environment.
WELLTHERM® Designers, Project Managers, Hydrogeologists, Groundwater Modellers and Supervising Engineers work very closely with EA officers to ensure that the Scheme will operate within EA guidelines and just as importantly, we will demonstrate the sustainability of the System.
Closed Loop Geothermal Systems
Closed Loop Systems utilise, as the name suggests, a system of plastic pipes which simply circulates fluid (water and environmentally friendly anti-freeze) through the ground absorbing heat (heating) or rejecting heat (cooling). The Heat Pump either increases the temperature for heating or decreases it for cooling, dependant upon the needs of the building.
In a currently unregulated industry in the UK (unlike the USA), there are unqualified people from all walks of life designing and installing fairly sizeable Closed Loop Systems. Closed Loop Systems need to be designed by people trained and qualified to do so. There are so many Schemes being installed based on ‘rule of thumb’ criteria that can be massively misleading. A common assumption is the dreaded 5kW from a 100m deep borehole and borehole centres of 5-6m apart. In reality, borehole depths generally range from 40m to 200m and the ‘output’ or ‘input’ capacity of a borehole could vary by a factor of ten. Whilst it is acceptable to use generalised estimations for initial concept work, this should be left behind once at Stage B and this is where a company such as WELLTHERM® Drilling should drive the project forward in an informed way.
Even a badly designed Closed Loop System may work initially! It may take many months or even years for the ground loop to overheat or freeze. The System may continue to work, however, it will be inefficient and unsustainable and any carbon reduction targets would be missed. At worst, the System could fail altogether.
In simplistic terms, think of it like the following analogy.
Imagine the ground is a rechargeable battery always on ‘trickle’ charge from the geothermal decay (heat source). If you are taking energy out (heating) at a greater rate than the ‘battery’ is being charged, it will go flat, or in this case the ground temperature will drop to unacceptably low temperatures. The System would therefore be unsustainable. The reverse is also true.
If you are rejecting heat (cooling) to the ground at a rate that is greater than can be accepted, you are effectively over-charging the ‘battery’. In this instance, the ground temperature would become too high, again, making the System unsustainable. This can be overcome by using a qualified and skilled Loopfield Designer to size the ‘battery’ to ensure it is sufficient to sustain your System. Getting the loopfield designed correctly is also more likely to save the team money. A specialised Loopfield Designer can accurately determine the required amount of loop in the ground cutting out unnecessary, expensive drilling (a common occurrence). Uncertainty can lead to over-design and boreholes can be expensive.
We have just completed on behalf of Geowarmth, one of the largest close loop borehole fields in the North East of England, (52 boreholes to 125m ). Which we completed 21 days ahead of schedule.
The principle of ground source heat pump technology is long-established and is based on the same process as the common domestic refrigerator. A quantity of thermal energy is removed from one source and transferred to another. In the case of a refrigerator, the energy is removed from the inside of the appliance (cooling the air inside as a consequence) and transferred to the heat dissipation coils on the back of the cabinet. In the case of GSHP, the energy is removed from the ground and transferred into the interior of a building. In both cases the energy source becomes chilled, and the energy sink is warmed.
Which system to choose?
There are two principal methods for supplying thermal energy to the source-side loop in GSHP applications:
(a) Closed loop systems, in which the source-side loop is long, and is buried in the earth, either: i. as coils of HDPE pipework to depths of > 1.5m in cut-and-fill trenches, or ii. suspended in vertical boreholes.
(b) Open loop systems, in which the source-side loop is covered in pumped groundwater, which is typically re-pumped to the subsurface via another borehole well after passing through the heat pump.
In both cases, the energy source generally approximates to the local average annual air temperature, which in the lowland UK is typically between 10°C and 12°C. The fluid in the source-side loop will typically be chilled to around 6°C after passing through the heat exchanger. The exchanger typically delivers heat at around 55°C. The system can be coupled to closed circuits of water pipes supplying conventional 'wet' radiators or underfloor heating systems. The under floor heating been the system far better suited to ground source heat pump applications.
Open Loop Geothermal Systems
An Open Loop System involves pumping water from an existing source, perhaps a river or a lake, but more often via boreholes that are drilled to access water sources below ground for efficiency
The water either travels directly to the integral Heat Pump or more commonly via a Plate Heat Exchanger.
An Open Loop System involves pumping water from an existing source, perhaps a river or a lake, but more often via boreholes that are drilled to access water sources below ground for efficiency.
The water either travels directly to the integral Heat Pump or more commonly via a Plate Heat Exchanger.
All Open Loop Systems using over 20m3 of groundwater per day are subject to lengthy and complex Environmental Agency (EA) Regulations. The EA are reasonably relaxed about Open Loop Groundwater Systems if spent water is returned to the aquifer from which it was taken, meaning that net permanent consumption is relatively small.
It must be demonstrated to the EA that the System is not going to affect an existing user of groundwater in the vicinity of the Project and that it offers no potential threat to the environment.
WELLTHERM® Designers, Project Managers, Hydrogeologists, Groundwater Modellers and Supervising Engineers work very closely with EA officers to ensure that the Scheme will operate within EA guidelines and just as importantly, we will demonstrate the sustainability of the System.
Closed Loop Geothermal Systems
Closed Loop Systems utilise, as the name suggests, a system of plastic pipes which simply circulates fluid (water and environmentally friendly anti-freeze) through the ground absorbing heat (heating) or rejecting heat (cooling). The Heat Pump either increases the temperature for heating or decreases it for cooling, dependant upon the needs of the building.
In a currently unregulated industry in the UK (unlike the USA), there are unqualified people from all walks of life designing and installing fairly sizeable Closed Loop Systems. Closed Loop Systems need to be designed by people trained and qualified to do so. There are so many Schemes being installed based on ‘rule of thumb’ criteria that can be massively misleading. A common assumption is the dreaded 5kW from a 100m deep borehole and borehole centres of 5-6m apart. In reality, borehole depths generally range from 40m to 200m and the ‘output’ or ‘input’ capacity of a borehole could vary by a factor of ten. Whilst it is acceptable to use generalised estimations for initial concept work, this should be left behind once at Stage B and this is where a company such as WELLTHERM® Drilling should drive the project forward in an informed way.
Even a badly designed Closed Loop System may work initially! It may take many months or even years for the ground loop to overheat or freeze. The System may continue to work, however, it will be inefficient and unsustainable and any carbon reduction targets would be missed. At worst, the System could fail altogether.
In simplistic terms, think of it like the following analogy.
Imagine the ground is a rechargeable battery always on ‘trickle’ charge from the geothermal decay (heat source). If you are taking energy out (heating) at a greater rate than the ‘battery’ is being charged, it will go flat, or in this case the ground temperature will drop to unacceptably low temperatures. The System would therefore be unsustainable. The reverse is also true.
If you are rejecting heat (cooling) to the ground at a rate that is greater than can be accepted, you are effectively over-charging the ‘battery’. In this instance, the ground temperature would become too high, again, making the System unsustainable. This can be overcome by using a qualified and skilled Loopfield Designer to size the ‘battery’ to ensure it is sufficient to sustain your System. Getting the loopfield designed correctly is also more likely to save the team money. A specialised Loopfield Designer can accurately determine the required amount of loop in the ground cutting out unnecessary, expensive drilling (a common occurrence). Uncertainty can lead to over-design and boreholes can be expensive.
We have just completed on behalf of Geowarmth, one of the largest close loop borehole fields in the North East of England, (52 boreholes to 125m ). Which we completed 21 days ahead of schedule.