Combined Electrical Power Generation using Solar and Wind

Licentiate thesis, 2017

The need for systems for renewable electrical power production is enormous worldwide.This applies to systems of varying size and capacity. From small systems for household purposes up to large systems for regional purposes. If possible, all systems should be linked in a common power grid. From an efficiency perspective, it is also an advantage if a specific power system can be designed for so-called island operation. This means that the present system has the capacity to provide power to its nearest surroundings. An important benefit of island operation is the increased possibility of, by appropriate supervision, evenly distributing the joint production to the overall power grid. It increases the ability to avoid overloading in some power systems. An island system can be equipped with an energy storage or an auxiliary device in the form of for example a diesel generator. This thesis deals with the analysis of a combined electrical power system for production of wind power and solar power. The total system consists of solar- and wind power generators, energy storage, power back-up and power grids in the form of a local grid and utility grid. The utility grid can be used for export of excess energy or import of deficit energy. The analysis is based on simulation using statistical models regarding solar radiation, wind speed and electrical loads. The solar radiation is calculated as a result of atmospheric transmission, geographic location, time of year and time of day. The atmospheric transmittance has been calculated using the “extinction coefficient”, a parameter which is a function of absorbing molecules and aerosols in the atmosphere. It has been demonstrated that this parameter is a powerful tool in connection with the analysis of the power system that utilizes solar energy. This parameter has in this work a central function in all calculations of solar radiation. The extinction coefficients in existing simulation model is based on performed measurements. However, these parameters can easily be calculated by special software. In this case with atmospheric parameters as input parameters. This has been demonstrated in the work. In the same way the statistical models of wind speed and electrical loads are results of performed measurements. The outputs from simulations are given in the form of statistical parameters. This means that simulation results are presented in statistical form regarding the combination of wind generators, solar generators, energy storage, power back-up and electrical loads. The current work has touched on several key issues relating to analysis of power generation using wind and sun. A number of interesting observations made have been noted. As an example of these are the use of the above-mentioned "extinction coefficient" parameter. The work has contributed to the availability of an effective  tool for statistical analysis of various combined power systems with a wide range of applications. The calculation routine used for calculating the effective solar radiation that drives solar power plants has proven to be well established in both practice and theory. The calculation routine in question allows excellent opportunities for detailed analysis regarding the planning of future solar systems. The simulation model has been applied in the work to a large number of cases.