Zukünftige Energie- und Industriesysteme
The concept of regime and "flat ontologies" : empirical potential and methodological implications
(2012)
Techno-economic feasibility study of solar and wind based irrigation systems in Northern Colombia
(2014)
Water pumping systems powered by solar and wind energy are a clean, decentralized and economic alternative for the irrigation of crops. The intense droughts experienced in the last years in Northern Colombia due to particularly strong Nino Phenomena have reactivated the need of reliable water pumping irrigation systems in that region. This study aims to assess the techno economic feasibility of solar and wind based pumping irrigation system, taking as case study the Municipality of Piojo in the Atlantico department. In the first stage of the study the irrigation water requirements were determined by using the software CROPWAT based on two different crop patterns that represent existing feasible alternatives for small farmers of the region: i) a common crop pattern, which represent the current average distribution of crops for subsistence farming and ii) a fruit cash crop pattern that comprises crops for which well established markets in the region exist. Solar wind and diesel based pumping systems were sized based on the crop water demands for 1 ha. The unit irrigation costs of the three technologies, the two crop patterns and the three irrigation methods (surface, sprinkler and drip) were calculated and compared. The economical analysis was complemented with a cost-benefit analysis over 20 years. Our results show that both renewable energy based pumping systems (wind and solar) can cover the irrigation water demands of small farmers in the region. The economical analysis shows that windmills are the most cost effective solution followed by the solar pumping system. Diesel pumping system was the less cost effective, even though it does not comprise investment in water storage tank. The cost benefit analysis demonstrates that any irrigation system is financially unfeasible when providing water to a common crop pattern. In case of the fruit cash crop scenario the highest dividends were obtained by the wind pumping system and the lowest dividends by the diesel pumping system. The lowest payback period was obtained by the windmill after 7 years and could be even feasible after the fifth year if the surplus water would be used to irrigate larger areas. Dividends obtained in a fruit cash crop scenario with irrigation after 20 years were in the range of EUR 5200 and EUR 11200 higher than dividends obtained by the same crop pattern but without irrigation.
Innovation and diffusion of car-sharing for sustainable consumption and production of urban mobility
(2008)
In the light of the tremendous challenges facing the energy systems of the Middle East and North Africa (MENA), a number of concepts, roadmaps and scenario studies have emerged, describing potential transformation pathways towards a more sustainable, renewable-based, energy supply future in the region. Our article uses the scientific approach of "transition research" to analyze the most pertinent publications and concepts in this field to identify the key drivers and barriers for the transformation of the regional energy systems. The analysis likewise includes an assessment of possible indicators and indexes that can be used to monitor the sustainability of the transformation process of MENA energy systems.
In recent years, many energy scenario studies have proven that a power supply system based on renewable energies (RE) >90 percent is feasible. However, existing scenarios differ significantly in the composition of generation technologies. Some scenarios focus on wind energy in the northern part of Europe, others base on a large utilisation of solar technologies in the south. Apart from the generation capacities, the needed technical flexibilisation strategies such as grid extension, demand flexibilisation and energy storage are generally known and considered in many scenarios. Yet, the impact of different renewable generation strategies on the local utilisation of flexibility options needs to be further assessed. Based upon the BMBF research project RESTORE2050, analyses have been carried out that focus on these interdependencies. The results of the project show that the local utilisation of flexibilisation options depends to a great extent on the technology focus of the long-term renewable expansion strategy. This applies for the spatial flexibilisation as provided by transnational interconnection capacities, especially the ones connecting regions with a surplus of power generation (e.g. GB, Norway and Spain). Another impact of the renewable scenario is seen on the required temporal flexibilisation of electricity generation and demand. In addition, the available options will compete for high utilisation in a future energy system. The differences in the utilisation of these applications, which base on the varying shares of photovoltaic (PV) and wind energy generation, lead to the conclusion that the decision about longterm RE expansion ought to be made very soon in order to avoid inefficient flexibility pathways. Otherwise, if the future RE structure will be kept open, adequate adoption of new flexibility options will be difficult, especially in case of technologies with long lead and realisation time (e.g. new power grids and large scale energy storage devices).