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Site Visit in Malton, Yorkshire

I have just returned from a site visit in Malton, Yorkshire with my colleague Fergus Wheatly from Smart Power to review a Geothermal closed loop system in a sealed borehole.

The bore hole is a repurposed gas well that is 3.2km in depth, however, to reflect a more typical installation the geothermal pipe was only deployed to a depth of 2km. The temperature at this point is 60°C rather than the 110°C found at the bottom of the well.

For the purposes of the demonstration a plastic HDPE pipe is being used. The pipe is inserted into the centre of the well, which is filled with a saltwater brine. The brine is circulated down the well via a piston pump and returned to the surface via the HDPE pipe. It passes through a heat exchanger before being returned to the well.

It should be noted that the HDPE pipe has poor insulation properties, with the output temperature settling towards 35°C (rather than 60°C), which is a rough average temperature for the well.

The system is currently producing a 100kW with a delta T of 6 degrees. If the Delta T increases the kW output will increase on a pro-rata basis (for example a 12-degree delta T equates to 200kW output).

The footprint of the well is approximately 1 square meter, with the adjacent energy centre contained in a 20ft container.

This system would be a good feed source for a heat pump, however the specialist contractor is finalizing an improvement which consists of insulated steel pipe (to replace the HDPE pipe), which would result in a higher temperature at the surface – this would also further increase the efficiency of heat extraction from the well.

We spoke to their drilling expert, who has extensive well drilling experience throughout Ireland. He stated that the geothermal resource in Ireland is generally much better than the UK.

Generally, Limestone, Sandstone, Mudstone, Clay and Chalk are all easy to drill and give good results.


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