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Biomass combined heat and power plants (CHPPs) can operate target-specifically because of their controllability while supporting decarbonization in district heating. The transition from the German Renewable Energies Act funding, which has promoted biomass CHPPs but is now about to expire, to direct marketing, is a major economic challenge for many biomass-heating grids. To successfully accomplish it, the flexible operation of biomass CHPPs, compared to the previous baseline-operation, is becoming an increasingly important requirement if participation in the electricity markets is to remain profitable. This paper presents a techno-economic assessment of flexible CHPP operation in a modeled district heating system with a CHPP, a peak load boiler and a thermal heat storage. The simulation model compares two cases - a natural gas and a wood-chip gasifier CHPP. The analysis of the results investigates the parameters that need to be adapted to make biomass-fired CHPP heating grids more efficient compared to fossil-fired CHPP heating grids in a flexible operating scenario. It highlights the technical and economic superiority of a fossil-fired CHPP in flexible operation in comparison to the wood gasifier system. The introduction of a CO 2 -tax on natural gas as a fuel, currently under discussion in Germany, would increase the competitiveness of the wood gasifier. • Simulation model of a district heating system. • Model units are wood or natural CHP plant, peakload boiler and heat storage. • Three scenarios for CHP plant dispatch under consideration of electricity prices. • Focus on dynamic differences of the CHP plant operation strategy. • Results show limitations in operational flexibility of the wood gas CHP plant. [ABSTRACT FROM AUTHOR]

• Autumn-sown sugar beet may intercept more PAR due to a faster canopy closure in spring. • Based on a 3 year field trial, a crop growth simulation model for autumn-sown beets has been developed. • It considers specific aspects like leaf losses due to frost, vernalisation and bolting. • The model was able to satisfactorily estimate total and root dry matter. • A 12 year simulation revealed that autumn-sown sugar beet achieved a 29% higher total DM than spring-sown ones. Autumn-sown sugar beets may achieve a faster canopy closure in spring compared to spring-sown sugar beets, thus increasing radiation interception and yield. However, to date yield benefits of autumn-sown beets cannot be quantified, as they start to bolt in spring. Therefore, simulation models for winter beet need to be developed. From 2009 to 2012, field trials in northern Germany were carried out with sugar beets sown in spring (conventional sugar beet) as well as sown in autumn (bolting winter beet). Based on these data, a dynamic simulation model was developed and calibrated for winter beets. The model is based on light use efficiency (LUE) approach and considered winter beet-specific aspects like leaf (area) losses due to frost, vernalisation and bolting. For conventional sugar beets, the validation revealed a RMSE of 164 g m-2 and a model efficiency (EF) of 0.93 for root dry matter. For the total dry matter (DM tot) of bolting winter beets, the validation showed a RMSE of 216 g m-2 and an EF of 0.69. Implemented assumptions regarding the non-bolting winter beets allow the model to simulate this beet type as well. A simulation over 12 years (1998-2010) for the site Hohenschulen estimated 1921 g DM tot m-2, 971 g DM tot m-2 and 2474 g DM tot m-2 for conventional sugar beets, bolting winter beets and non-bolting winter beets, respectively. Our results suggest that developing non-bolting winter beets seems be a promising approach to increase beet yields. [ABSTRACT FROM AUTHOR]