INFORMED

Geothermal Prognosis

Prior to undertaking a geothermal project, a prognosis must take place to assess the ground’s capacity to deliver heat to a heat pump. A prognosis, or ‘geo-report’ generally looks at:

• Geology and ground compositions: the heat transfer capabilities of the ground will vary depending on factors such as soil types, rock formations, and thermal conductivity. It will also identify if there are any drilling hazards or obstructions on your site.
• Ground temperature profile: what is the subsurface temperature at different depths? Higher temperature gradients equals more efficient ground source heating systems.
• Groundwater availability: the depth, volume, flow and quality of groundwater will affect the impact of the ground source heat pump.
• Layout: depending on factors such as the available land area and soil conditions, the layout and length of the system will differ: e.g. horizontal or vertical loop boreholes.

Igne’s geo-reports utilise data from maps, national archives, and databases: all of which are interpreted by a chartered geologist. 

HORIZONTAL OR VERTICAL

Heat Collection Systems

There are two main types of heat collection systems: horizontal and vertical. 

Horizontal heat collection systems involve digging at least 10m of trenches (at a depth of 2m) for each kWh gained. This method of heat collection is expensive and is not recommended by Igne.

Instead, Igne recommends using a vertical heat collection system. Vertical systems are simpler, faster, and more cost-effective, requiring boreholes to be drilled rather than trenches. Additionally, boreholes are much less disruptive to your site and offer better consistency and efficiency in heating. 

There are two types of vertical heat collection systems: 

• Closed loop: these utilise U-shaped pipes with anti-freeze and a heat-conductive grout. The water is circulated through the pipes, to your building, and is subsequently returned to the ground. 
• Open loop: water is collected from the ground and is circulated directly through the heat exchanger/pump system, and can then either be used as a grey-water supply, be discharged to a surface water system, or be routed back underground. 

Igne has extensive experience installing both open and closed-loop vertical systems, and has worked with major clients such as city councils and leisure centres. To learn more about what system is right for you, contact Igne’s team of experts today.