Abstract. Wind farm sites in complex terrain are subject to local wind phenomena, which have a relevant impact on a wind turbine's annual energy production. To reduce investment risk, an extensive site evaluation is therefore mandatory. Stationary long-term measurements are supplemented by computational fluid dynamics (CFD) simulations, which are a commonly used tool to analyse and understand the three-dimensional wind flow above complex terrain. Though under intensive research, such simulations still show a high sensitivity to various input parameters like terrain, atmosphere and numerical setup. In this paper, a different approach aims to measure instead of simulate wind speed deviations above complex terrain by using a flexible, airborne measurement system. An unmanned aerial vehicle is equipped with a standard ultrasonic anemometer. The uncertainty in the system is evaluated against stationary anemometer data at different heights and shows very good agreement, especially in mean wind speed (< 0.12 m s−1) and mean direction (< 2.4∘) estimation. A test measurement was conducted above a forested and hilly site to analyse the spatial and temporal variability in the wind situation. A position-dependent difference in wind speed increase of up to 30 % compared to a stationary anemometer is detected.

To reduce emissions in the energy sector and reach worldwide climate goals, further expansion of renewable energy sources (RES) is inevitable. Local opposition has increased in recent years, resulting in the need for more consideration of acceptance issues in the planning process of RES projects. To fill this gap, a method is introduced to consider the dimension of social acceptance in a holistic approach and at an early project stage. In a two-step procedure, a municipal interest profile is created, followed by an examination of possible expansion projects based on the municipal profile. Both hard and soft characteristics of a given project are assessed in combination. Using the example of two potential scenarios for biomass expansion in a given municipality in Germany, the methodology is put to the test. The results show that with the new method House of municipal Energy (HomE), the interest profile of a municipality can be quantified in a comprehensible and transparent way. It is further shown that, depending on the initial objective function of the municipality, different expansion scenarios can be advantageous. In the examined case, the larger biogas plant achieves a higher utility value, since a clearly higher local added value can be generated. A smaller plant, which is only operated with waste materials, is preferable with regard to the required area and lower environmental impact. However, the advantages of the larger plant outweigh those of the smaller plant for the investigated example.

The pressure on the energy sector to reduce greenhouse gas emissions is increasing. In the light of current greenhouse gas emissions in the energy sector, further expansion of renewable energy sources (RES) is inevitable to reduce emissions and reach the climate goals. This study aims at investigating structural characteristics of German counties regarding advantages for self-sufficient power systems based on RES. The modelling of the power sector based on RES is coupled with a cluster analysis in order to draw a large-scale conclusion on structural characteristics beneficial or obstructive for municipal energy systems. Ten clusters are identified with the Ward algorithm in a hierarchical-agglomerative method. The results underline a further need for RES expansion projects in order to close the gap between supply and demand. Only then, bioenergy can effectively balance the offset and support a truly self-sufficient local energy system. While the model results indicate that the majority of the counties are suitable for further expansion, this suitability is to be questioned in cluster 10. High population density is a critical characteristic, because with it come both a high demand and limited sites for further RES expansion projects.

Abstract. Wind farm sites within complex terrain are subject to local wind phenomena, which have a huge impact on a wind turbine's annual energy production. To reduce investment risk, an extensive site evaluation is therefore mandatory. Stationary long-term measurements are supplemented by CFD simulations, which are a commonly used tool to analyse and understand the three-dimensional wind flows above complex terrain. Though being under heavy research, such simulations still show a huge sensitivity for various input parameters like terrain, atmosphere and numerical setup. Within this paper, a different approach aims to measure instead of simulate wind speed deviations above complex terrain by using a flexible, airborne measurement system. An unmanned aerial vehicle is equipped with a standard ultrasonic anemometer. The uncertainty of the system is evaluated against stationary anemometer at different heights and shows very good agreement, especially in mean wind speed (

Abstract. Uncoordinated extension of renewable energy sources (RES) disregarding local demand structures leads to increased loads on the transmission grid and overall economic losses. One approach to solve this problem is to support the local power consumption by local power generation without making use of the transmission network. Therefore, the actual physical coverage of local demand with local supply is to be investigated instead of a yearly net power balance. Rural municipalities are an ideal starting point to establish such self-sufficient power supply systems on the basis of RES as they have a high RES potential in combination with low demand loads. Fluctuating feed-in of wind and solar power and peaks in demand loads can be balanced by bioenergy as flexible power generation capacity. In contrast to highly resource dependent wind and solar power, biomass can be stored and power generation from biomass can be controlled flexibly. To assess the potential of electricity from biomass, this study analyses the agricultural structure of the rural municipalities. The objective of this study is to assess what kind of agricultural structure might be advantageous for flexible power generation from bioenergy, hence balancing fluctuation RES feed-in and power demand. The results from this structural assessment of rural municipalities can help for analysing further municipalities to identify potentials at first sight without costly individual analysis. Heat and fuel sectors are neglected. A methodology is introduced to model time series of wind, PV and biomass power with a 15-minute resolution. It is evaluated to which degree it is possible to cover the local demand in power supply with bioenergy as flexible power generation capacity in the identified clusters. The results indicate that bioenergy is generally suitable to cover the gap between local power demand and supply. Waste products from animal farming are far more effective for biomass power production than from agricultural farming. Low population densities raise the potential for self-sufficiency in the power sector because of low demand loads. Further improvement of the model is needed concerning the clustering approach and for the approximation of installed wind and PV power capacities.