**4. Result and discussion**

The measured parameters as well as calculated parameters such as number of He moles emanating per second (n), the total number of He atoms emanating per second (*NHe*), the contributed relative concentration of 232Th (*CTh*), 238U (*CU*�238) and 235U (*CU*�235) including the energy contributed due to decay of 232Th, *ETh*�232, 238U, *EU*�<sup>238</sup> and 235U, *EU*�<sup>235</sup> etc. are listed in **Table 2**. The Table reflects that the heat energy generated per unit second by the radioactive decay of 232Th, 238U and 235U inside the reservoir are 31.58 MW, 6.3585 MW and 0.0467 MW respectively and together contributed as approximately 38 MW [radiogenic source, *ER Total* ð Þ]. Considering the concept of [46], as mentioned above, total heat energy [*ETotal*] related to the radiogenic source [*ER Total* ð Þ] and the primordial source [*EP Total* ð Þ] is expected to be 76 MW. Moreover, the values would be likely increased whenever the He emanations through the others hot springs (where He emanation is comparably less than that of Agni Kunda) and the vast surface area (soil gas) at Bakreswar would be included in this estimation. However, this was a little bit difficult as well as complicated due to the technical coerces and geographical constraints. It is notable that Kalina cycle based binary power plant using ammonia–water mixture as working fluid (thermal efficiency: 13–53%) [47], is already proposed to be


#### **Table 2.**

*Experimental and calculated parameters.*

#### *Quantitative Approximation of Geothermal Potential of Bakreswar Geothermal Area… DOI: http://dx.doi.org/10.5772/intechopen.96367*

installed at the spring site [48]. Accordingly, if such type of power plant is supposed to be installed, for say, the plant would be capable of delivering the power of 4.94 MW (minimum thermal efficiency 13%) to 20.13 MW (maximum thermal efficiency 53%) only considering the radiogenic heat source. These values are changed to 9.88 MW and 40.26 MW, respectively, when the primordial heat source is comprised of the radiogenic heat source.

Recently, the reservoir temperature [*θr*] of the Bakreswar geothermal system was estimated to be 126–130 °C by [40] by means of silica geothermometry. The average ambient temperature [*θa*] of the study area was recorded to be 26 °C. Our estimation using the mathematical relation [Eq. (18)] shows that the geothermal reservoir at the area is expected to be located at about [x=] 1,111 to 1,155 m beneath the surface. Moreover, the results of audio magnetotelluric (AMT) studies collected from [41] revealed the existence of a deep heat reservoir in the N–W part of Bakreswar. Observation sites 000, 001, 003, 005, 007, 008, 103, 105, 110, as marked in **Figure 3**, show low resistivity profile, and these are more favourable sites for deep drilling.

It is notable that no such work has been carried out to figure out the potential of Bakreswar geothermal region in terms of power harnessing capability. However, [42] estimated the geo-heat of the site to be 1158 KW-hr (=416.88<sup>10</sup><sup>7</sup> Joule) by means of considering total water discharge through Agni Kunda hot spring and difference between the spring temperature and mean ambient temperature. Further, another approach may be considered here to get a comparative view in this regard. In this connection, the water discharges from the Agni Kunda and Khar Kunda hot spring were measured to be 790 L/min (790 kg/min) and 680 L/min (680 kg/min) respectively. The amount of the heat energy carried out (per second) by the hot water through these springs would be 10.29–10.70 MJ (equivalent to 10.29–10.70 MW in terms of power). However, the energy carried out by other springs is not included herewith due to technical difficulties. Furthermore, the energy carried out by the gaseous phase of the hot springs and the heat loss through the soil of the vast region is out of scope to be counted.

## **5. Conclusion**

Using a simple technique by means of He exploration study at the field site, the probable energy generated inside the reservoir was estimated here. Considering the combined source of heat generation inside the reservoir system, the energy was expected to be generated from the source of power of 38 to 76 MW using the appropriate technology. The utilization of proper technology for power generation could facilitate to build a Kalina cycle based geothermal power plant (using ammonia–water mixture as working fluid) of power harnessing capability of 9.88 MW to 40.26 MW at the study area. Moreover, the values would be likely increased whenever, the He emanations through the others hot springs (where He emanation is comparably less than that of Agni kunda) and through the vast surface area (soil gas) at Bakreswar would be included in this estimation. However, this was a little bit difficult as well as complicated due to the technical coerces and geographical constraints. Furthermore, the deep drilling (production & injection well) of the proposed power plant to be rooted upto a depth of approximately 1,100 m at a location near to the hot spring area as indicated in the **Figure 3**. However, a detail geophysical survey may also be required for selecting the appropriate and exact location for drilling as well as the measurement of the horizontal (length & widthwise) and vertical (depth-wise) dimension of the geothermal reservoir at the area.

The same would be subjected to accurately calculate the possible capacity of the power plant to be installed at the site.
