Author(s)

C. KONRAD, J. STRITTMATTER, A. GRUNERT, M. BRULE, M. ROTH, M. HERTER, G. GÖTTLICHER, R. BIEHL & A. BOTT

Abstract

In the German electric energy market, the share of regional and decentralized power generation based on renewables has become more and more significant. The following study describes the initiative of the energy and utilities company ‘EnBW Energie Baden-Württemberg AG’ (EnBW) in Germany to investigate regional energy concepts based on agricultural biomass. The study focuses on two aspects: the development of more sustainable approaches for energy crops cultivation and the efficient use of cogeneration heat produced by bioenergy-driven power plants in rural areas. For the development of concepts and tools, a study area including two counties in the South-West of Germany were chosen. This article focuses on the work done on the county of Ravensburg.Geographic information system (GIS) tools are used to collect data about current land use practices related to energy crops. Subsequently, the suitability of new and more sustainable energy crops for biogas production based on current production regimes is investigated by following a modeling approach. The approach followed includes the screening of new agricultural substrates as substitutes for maize, which is currently the dominant energy crop for biogas production in Germany, the modeling of new substrate mixtures, and the measurement of the methane potential of energy crop samples in a biogas laboratory. Bioenergy-driven power plants are usually implemented nearby high biomass potentials—in rural areas, where heat demand is scarce. Optimizing heat use in combined heat and power (CHP) generators is a major issue for the future of bioenergy. The efficient utilization of residual heat is one of the targets of the upcoming update of the German Renewable Energy Sources Act in 2012. Therefore, the profitable operation of biogas plants increasingly depends on the level of heat use which can be reached. The possibilities for heat supply to potential consumers in rural areas have been investigated using a GIS methodology on an object-based level for residential and tertiary/industry sectors. Building age and type have been used as parameters to estimate the annual heat consumption. Scenarios illustrating a renovation rate of the investigated objects (buildings) have been calculated. For the purpose of verification and calibration, measurements of the heat demand of more than 3,000 houses have been used. Furthermore, on the basis of existing biogas plants, a techno-economic comparison of heat networks with micro gas networks for the distribution of renewable energy to demand sites have been performed.

Keywords

biodiversity, biogas, biomass potential, building, district heating, GIS, heat demand, heat sinks, micro gas grid, substrate