comparison of environmental aspects of geothermal ... - Orkustofnun

Report 17
During implementation of this project,
there was no environmental law for
guidance and no mandatory Environmental
Impact Assessment process
project proposals. The project activities
were however bound by and undertaken
in line with a memorandum of
understanding signed between KenGen
and the Kenya Wildlife Service (KWS),
who are custodians of all national parks
and nature reserves in Kenya. However,
from the early 1990s, most power
projects were subject to the EIA process
which are a mandatory condition by
financiers such as World Bank,
International Monitory Fund (IMF) and
regional financial institutions.
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Mwawughanga
4.2.2 Nesjavellir geothermal electric
power project in Iceland
Nesjavellir power plant is located within
the Nesjavellir geothermal field, which
is along the northern margin of the hightemperature
thermal anomaly associated
with the Hengil central volcano in SW-
Iceland, as shown in Figure 4. The
power plant is operated by Orkuveita
Reykjavíkur (Reykjavík Energy).
Annual precipitation averages 2,780
mm/year and mean annual temperature
is 2.9°C. The project is located FIGURE 3: Location of the Olkaria 1 power plant
southwest of Lake Thingvallavatn
in the East African Rift valley
which is under protection, and activities
of the power project may affect the lake since waste brine is disposed of in an open stream which
disappears underground and emerges as springs at the lake. The vegetation in the area is characterised
by mosses, grasses, shrubs, and woodland in some areas. The vegetation is poor due to over-utilization
in the past and soil erosion rampant in the upper areas due to the sensitivity of the soils.
The depth of production wells for electricity production ranges from 1000 to 2200 m and the temperature
in the production wells is in the range 320-360°C. The electric power plant has an installed capacity of
90 MWe. Prior to the commissioning of the electric power plant in 1998, Nesjavellir produced 200 MWt
of hot water for district heating purposes only for Reykjavík. In 1998, two 30 MWe turbine generators
were installed and modifications made to the thermal plant (Gíslason, 2000). Another 30 MWe turbine
generator was installed in 2000.
The concept of the plant was to co-generate electricity for the national grid, and water for district heating.
Exhaust steam is used to preheat fresh water in condensers. The separated geothermal water is used in
heat exchangers to heat preheated water to the required temperatures. The heated water is then treated in
de-aerators to suit requirements of the distribution system. Thus, water and steam are used in the most
economic way while lowering the temperatures of waste water considerably, reducing thermal impacts
on the environment.