variable operation costs saved in the system. Three different sets of fuel prices have been used, as expressed by the three different oil prices of US$40, US $68, and US$96/barrel. If the excess electricity produced is not used in CAES systems, one alternative is to sell it on the Nordic electricity market. In Figure 5.38, three different selling prices have been analyzed: 0, 13, and 27 EUR/MWh, respectively.
In Figure 5.38, the annual net operational income is compared to the investment and fixed operational cost per year of 14 million EUR (marked by a dotted line). As shown, variations in the fuel price mean little to the results because CAES stations burn natural gas, and, consequently, fuel savings at the power stations are counterbalanced by fuel costs at the CAES station. The price of excess electricity production is important. However, even if the excess power produced is free, annual net earnings are far from the level of annual investment and fixed operation costs.
The system economic feasibility of CAES stations has been compared to other technologies that may also use excess electricity production and contribute to a better system integration of wind power. All alternative technologies have been designed in such way that they all have the same annual investment and fixed operation costs as explained previously namely, 14 million EUR/year. The cost components are based on Mathiesen and Lund (2009) and explained in Lund and Salgi's (2009) article, and the results are shown in Figure 5.39. The results in Figure 5.39 apply an oil price of US$68/barrel and an excess electricity price of 13 EUR/MWh. However, only minor changes are achieved by applying other price levels, apart from the electric boiler, which is especially sensitive to the price of excess electricity.
It can be seen from Figure 5.39 that CAES stations are not feasible, and other options are significantly more attractive. It must, however, be emphasized that such an analysis is solely concerned with the benefits of better operation, including the integration of wind power. In one important aspect, the ar 40
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.