In order to estimate the effects of the meteorological variability on the gross primary production in the Ligurian Sea (NW Mediterranean Sea), a coupling between a hydrodynamic model and a biological one is realized. The one-dimensional version of the GHER hydrodynamic model includes heat and momentum exchanges at the air–sea interface. It is coupled with a simple food-web model from the LEPM. A simulation performed with real meteorological data for the year 1985 reproduces reasonably the seasonal phytoplanktonic dynamics and the distribution between diatoms and flagellates. From this simulation, an annual gross primary production integrated over 200 m of 46.4 g C m−2 year−1 is computed which is representative of an oligotrophic environment. In order to estimate the relative effect on the gross primary production of the meteorological variability on the one hand and of the initial conditions on the other hand, several runs have been performed for the year 1985 with different conditions of light, wind intensity and nitrate initial quantity. The first simulations are performed with daily and monthly mean solar radiation and wind intensity. An averaging of wind intensity yields a decrease in the gross primary production and leads to unrealistic phytoplankton dynamics. It seems then necessary to take into account the 3-hourly variability of the wind intensity in order to simulate the phytoplankton dynamics with relatively good accuracy. On the other hand, an averaging of the solar radiation leads to an increase in the gross primary production. The following simulations are performed with an increase (decrease) in the solar radiation, the wind intensity or the nitrate initial quantity which are representative of the variability observed in a 5-year set of meteorological and hydrobiological data (1984–1988). An increase in the solar radiation is found to reduce the gross primary production, while an increase in the initial nitrate quantity or the wind intensity leads to a higher gross primary production, and the reverse. In the case of variations of the solar radiation (±2%), the simulations give an annual gross primary production integrated over 200 m included between 44.8 and 46.7 g C m−2 year−1, representing a variability of 4%. With the variations of the surface wind intensity (±10%), the runs carry to an annual gross primary production integrated over 200 m from 34.1 to 59.1 g C m−2 year−1, representing a variability of 54%. The variations of the initial nitrate concentration (±50%) lead to an annual gross primary production integrated over 200 m between 20.7 and 69.8 g C m−2 year−1 which represents a variability of 108%. An analysis of the relationship between the total gross primary production and the annual mean depth of the mixed layer has shown that the deeper the mixed layer is, the higher is the total annual gross primary production.
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The decarbonization of the heating sector is crucial for the green transition of the energy mix. This study investigates threefold the economic and environmental performance of deep geothermal heating investments in Northern Belgium First, techno-economic and life cycle assessment (LCA) are performed, followed by a global sensitivity analysis focusing on the geological uncertainty. Lastly, real options analysis (ROA) is employed to investigate the economic and environmental value of the investors’ flexibility. A novel ROA method is proposed that considers the LCA results to calculate development decisions that minimize the expected environmental impact of the investment. The results show that the economic and environmental performance of the investment vary with the energy prices and the electricity mix. The performance of the investment is driven by the plant’s pumping requirements, which are induced by the relatively low rock permeability at the targeted location. Also, the results’ variability mainly originates by uncertainty regarding the permeability value. Nevertheless, the investors’ flexibility adds large economic and environmental value to the investment. However, the development strategies that optimize the economic or the environmental performance of the plant present some trade-offs. This study demonstrates that the economic and environmental performance of deep geothermal heating investments in Northern Belgium can be improved by focusing on the factors that simultaneously drive the costs, environmental impacts, and their variability. It also shows that utilizing the investors’ flexibility to optimize the investment’s economic and environmental performance can add significant value to the investment.
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RBINS Staff Publications 2024
