Posts Tagged ‘mine subsidence risk’

Solar Farms Over Mined-Out Areas

FIGURE 1

There are vast areas of undeveloped land which exist over underground abandoned coal mining that can be potentially used for solar farm development (see Figure 1). These land use areas can be economically feasible for this purpose even when accounting for any future land subsidence resulting from mine collapse. Therefore, prudent due diligence requires an expert analysis on how much damage could occur.

It is MEA’s experience from previous project investigations that even solar development was viable with the identified subsidence risk and predicted damage.

The economics of subsidence damage depends on the predicted number of subsidence events which would result over the lifespan of the farm and the amount of associated damage to the farm infrastructure and whether the damaged element is repairable. Therefore important elements of the economic feasibility of the farm against mine subsidence are:
  • The resistance of the mine structure to collapse across the project site (i.e., more resistant leads to less collapse over time).
  • Severity and extent of the surface subsidence across the project site.
  • The damage thresholds of the various farm infrastructure to those subsidence movements. For example, a significant part of this subsidence damage analysis is assessing the subsidence interaction of the tracker whose piers would be exposed to a range of horizontal and vertical movements.

    FIGURE 2 A SKETCH ILLUSTRATING INDUCED TRACKER BEHAVIOR FROM A SINGLE SAG EVENT OVET AN ABANDONED MINE

    This is illustrated in Figure 2 when sag subsidence is expected.
  • The extent and intensity of the damaged farm areas across the project site.
Moreover, based on the site specific conditions, the economics can be improved through Kaizen analysis and mitigation measures taken to reduce the expected level of damage. To understand more about mine subsidence risk see Engineering Update #14 – Establishing Mine Subsidence Risk.