European renewable energy developments have so far focussed on electricity generation, with relatively modest progress in renewable heating. Partly this is due to the temporal mismatch between solar irradiation availability and residential heating demand profiles. Seasonal thermal energy storage (STES) has been proven in several pilot projects and is market ready, albeit not currently economical. This paper sets out to assess the potential contribution of STES to increasing the renewable heating fraction in residential buildings. An existing mixed integer linear program (MILP) is extended to consider STES and applied to optimize the energy supply system for a typical residential district with efficient new-build apartment buildings, in the context of five contrasting scenarios. Achieving 100% renewable heat supply requires significant capacities of seasonal storages and is associated with substantially (14%) higher cost than in the reference scenario. To achieve a 60% renewable heat supply fraction under today's framework conditions, the cost increase compared to the reference scenario is only marginal (1%). The results in three future scenarios reflecting possible conditions in 2030 demonstrate that even higher levels of renewable heat supply could soon become economical. Overall the recommendation is to aim for renewable heat supply levels of around 60–80% combined with demand side measures such as improved insulation. Further work should focus on more systematically exploring the relationship between the grid renewable electricity fraction, available solar collector area and the optimal renewable heat integration strategy.

The residential building sector has an important role to play in the energy transition due to a high share of final energy consumed and a considerable amount of CO2 emitted. Ambitious targets in Germany relate amongst other things to a primary energy reduction of 80% and an increased usage of renewable energy sources in heat supply to 60% in 2050. Existing research in this area both lacks detail in modelling decentralised heat supply in residential buildings and fails to adequately quantitatively analyse this target achievement for Germany. In order to overcome these limitations, a novel model-based approach is presented in which the developed TIMES-HEAT-POWER optimisation model is coupled with a decentralised energy system optimisation model to determine optimal and realistic technology configurations, and a building stock simulation model to adequately and consistently project the evolution of the building stock in Germany. This novel configuration of models is then used to investigate the evolution of the electricity system and the residential heat system in Germany in the context of key energy-political targets up to 2050. The national goals related to primary energy reduction and the share of renewable energy sources in final energy demand in the residential heat sector are missed in the Reference Scenario. On the other hand, target achievement requires deep insulation measures and a supply-side technology shift away from gas and oil boilers towards heat pumps and solar thermal. The scenario analysis reveals a significant sensitivity of the deployment of micro-Combined heat and power technologies (μCHP) and heat pumps to, amongst other things, the evolution of fuel prices, renewable electricity technologies, heat and electricity demand as well as technological progress. Further model extension can be identified inter alia in broadening the system boundaries to integrate further sectors (tertiary, industrial) or incorporating different user categories and decision rationales.

In optimisation models, the characteristic features of capacity investment and dispatch planning of supply technologies are well explored for electricity systems. Little attention to date has been paid to exploring these features in an adequate manner for heat systems. This paper discusses the implementation of decentralised residential heat supply in optimising energy system models and presents an application in TIMES, an energy system model with broad application. It is shown that standard TIMES does not allow for an appropriate implementation of residential heat systems. Consequently a two-part solution procedure is presented. A special integrated TIMES feature is explored and a tailor-made methodological extension of the TIMES standard code developed. Mixed integer programming is employed to accurately model the capacity planning of residential heat supply systems. Model results yielded by the new approach comply with the realistic capacity planning of heat supply systems in a shortened computation time. A case study for selected residential heat demand categories yields contrasting results for the mixed integer programme and the standard linear programme. The model’s extension to cover larger, centralised combined heat and power plants and district heating networks remains for further work; the lower solution times encountered seem promising in this respect.

Against the background of the ambitious German targets for renewable energy and energy efficiency, this paper investigates the economic potential for thermal load management with virtual power plants consisting of micro-cogeneration plants, heat pumps and thermal storage within the residential sector. An optimising energy system model of the electricity and residential heat supply in Germany is developed in the TIMES (The Integrated MARKAL EFOM System) modelling framework and used to determine capacity developments and dispatch of electricity and residential heat generation technologies until 2050. The analysed scenarios differ with respect to the rate of technological development of heat and power devices, fuel and CO2 prices as well as renewable electricity expansion. Results show that high fuel prices and a high renewable electricity expansion favour heat pumps and insulation measures over micro-cogeneration, whereas lower fuel prices and lower renewable electricity expansion relatively favour the expansion of micro-cogeneration. In the former case heat pump capacities increase to around 67 GWel, whereas in the latter case the total capacity of micro-cogeneration reaches 8 GWel. With the aid of thermal storage, this provides considerable flexibility for electrical load shifting through heat pumps and electricity generation from micro-cogeneration in residential applications, needed for the integration of fluctuating renewable electricity technologies.

Shaping our energy system – combining European modelling expertise : Case studies of the European energy system in 2050

This paper assesses the practicability of meeting the German federal government's energy-political targets for the residential sector by analysing the potential future development of this sector in an aggregated bottom-up model. The domestic building stock is considered in terms of the likely developments in the housing market, as well as the energetic characteristics of current and future buildings. The employed method is based on deterministic projections of demand floor space and demolition/refurbishment rates. The key novelty lies in the focus on developments in this sector in Germany; existing studies have not had this focus and have therefore employed a more rudimentary methodology, for example with static refurbishment rates, shorter time horizons or no spatial differentiation. The total resulting final heating demand of domestic buildings of about 500 TWh lies above that of other studies in 2050, which is mainly due to the conservative assumptions regarding renovation activity and new build made in the present case. Hence in the reference scenario the target for 2020 is not met, suggesting that further political intervention is required. In another scenario, it is shown that a drastic increase of the renovation rate is required in order to meet the 2020 target, especially amongst existing single family buildings. The supply side is only indirectly considered due to the aggregated nature of the model, which could be improved for further work, but the presented method nevertheless represents a good compromise between using solely freely available data and obtaining superior degree of precision to previous studies. (C) 2013 Elsevier Ltd. All rights reserved.

Paper production is an energy-intensive process and accounted for about 9% of industrial energy demand in Germany in 2008. There have only been slow improvements in energy efficiency in the paper industry over the past twenty years. Policies can accelerate the progress made, but knowledge about the remaining efficiency potentials and their costs is a prerequisite for their success.