sources of energy for geothermal direct heat use - GNS Science

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Figure 6. Two cascade options for an agri-business complex using 130 o C wastewater in Wairakei. Total energyusage for each process is roughly estimated and assumptions are shown above.3.2.2 Parallel usesParallel uses may involve drilling of new wells or using discarded wells for direct heat uses,in a developed power-generating field, e.g., the greenhouse in Mokai and the pulp and papermill in Kawerau.In calculating the potential energy for direct heat uses parallel to power generation, thefollowing are assumed:1. Twenty geothermal systems have been developed for power generation includingWairakei, Mokai, Ohaaki-Broadlands, Mokai, Rotokawa, Kawerau, Rotorua and Ngawha.2. (In geothermal systems with >1 MWe potential (Lawless, 2002) at least two wells arededicated for direct heat use.3. Where direct heat utilisation is already employed such as in Wairakei, Mokai, Ohaaki,Mokai and Kawerau, only one well is assumed (Appendix 1).4. Minimum discharge temperature from the wells dedicated to direct heat use is 180 o C(763 kj/kg) and the flow is at least 5 L/s.A shown in Table 1 the minimum total energy from parallel use of geothermal energy is 2.53PJ.In summary conventional sources of geothermal heat, which include hot spring systems andcascade and parallel uses of geothermal fluids from power-producing systems, have apotential total energy of at least 265 PJ of which only 5% is presently being used.GNS Science Report 2007/16 6
Table 1. Conservative projected energy use, in megawatts thermal (MWt) and petajoules (PJ), of parallel directheat usage in power-producing geothermal systems.AreaPotentialgeneratingcapacity 1Number ofwells forparallel useMWtPJAtiamuri 1 1 3.8 0.12Horohoro 1 1 3.8 0.12Kawerau 350 1 3.8 0.12Ketetahi off limits 0.0 0.00Mangakino 20 2 7.6 0.24Mokai 95 1 3.8 0.12Ngatamariki 90 2 7.6 0.24Ngawha 50 2 7.6 0.24Ohaaki 100 1 3.8 0.12Orakeikorako 90 2 7.6 0.24Reporoa 20 2 7.6 0.24Rotokawa 230 2 7.6 0.24Rotorua 25 1 3.8 0.12Rotoma 28 2 7.6 0.24Tauhara 200 2 7.6 0.24Te Kopia 75 2 7.6 0.24Tikitere 160 2 7.6 0.24Tokaanu 130 2 7.6 0.24Waimangu 180 2 7.6 0.24Waiotapu 250 2 7.6 0.24Wairakei 380 1 3.8 0.12TOTAL 3.961 from Lawless (2002)GNS Science Report 2007/16 7
Page 3 and 4: BIBLIOGRAPHIC REFERENCEReyes, A. G.
Page 5: Figure 11 Location of onshore aband
Page 11: the South Island, however,
Page 15 and 16: Table 2. Specific heat capacity and
Page 17 and 18: eyes 07Figure 8. Map showing areas
Page 19 and 20: eyes 07Figure 10. Estimated constan
Page 21 and 22: Table 5. Estimate of heat reserves
Page 23 and 24: Figure 12. Potential uses of heat f
Page 25 and 26: Table 6. Extractable heat energy fr
Page 27 and 28: Table 7. Present and potential extr
Page 29 and 30: eyes 07Figure 15. Potential energy
Page 31 and 32: 7.0 REFERENCESAllis R G (1979) Heat
Page 33 and 34: APPENDIX 1. WASTE WATER AND STEAM F
Page 35 and 36: APPENDIX 2. WARM GROUNDS AND WATERS
Page 37 and 38: Well NameTotal Depth(m)BHT(C o )MWt

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