| Title | Investigating Retrofitting an Existing Geothermal Power Plant with a Biomass Gasifier for Additional Power Generation |
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| Authors | S. Chester, C. Williamson, G. Hooper, Mike Dunstall |
| Year | 2016 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Hybrid Power Generation, Biomass Gasification, Geothermal Power |
| Abstract | This paper investigates different hybrid configurations for integration of biomass gasification into an existing geothermal power plant in order to generate additional power. Gasification is a promising energy technology for New Zealand and a hybrid plant in areas where supplies of wood residue and geothermal resources coexist represents a potentially attractive first step in its utilization. Four hybrid configurations were examined to retrofit a biomass gasifier into the Wairakei Geothermal Field. Each of the configurations were evaluated against operational constraints that exist in the field.. Configuration 1: Superheating of geothermal steam for more efficient power generation. A maximum of 12 MWe additional power generated with a 14 t/hr wet wood input with a wood-electricity energy efficiency (LHV) of 31.4%. Configuration 2: Syngas fired heating used to boil condensate available on site for additional steam generation. A maximum 6.5 MWe of additional power generated with a 16 t/hr wood input with a wood-electricity energy efficiency (LHV) of 15.5%. Configuration 3: Boiling separated geothermal water immediately after the first separation stage. A maximum 7.3 MWe of additional power generated with a 16 t/hr wood input with a wood-electricity energy efficiency (LHV) of 17.5% Configuration 4: Heating of separated geothermal water available at Wairakei to increase power generation at an existing binary power plant. A maximum 1.4 MWe of additional power is generated with a 3.5 t/hr wood input with a wood-electricity energy efficiency (LHV) of 15.4% The resulting electrical efficiencies are generally lower than for gasification gas engine power plants, but are encouraging in suggesting a novel route to the deployment of biomass gasification plant in NZ. The hybrid concepts examined show significant merit in terms of improving current geothermal steam utilization at Wairakei. |