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Abstract: A clear consensus exists in German society that renewable energy resources have to play a dominant role in the future German energy supply system. However, many questions are still under discussion; for instance the relevance of the different technologies such as photovoltaic systems and wind energy converters installed offshore in the North Sea and the Baltic Sea. Concerns also exist about the cost of a future energy system mainly based on renewable energy. In the work presented here we tried to answer some of those questions. Guiding questions for this study were: (1) is it possible to meet the German energy demand with 100% renewable energy, considering the available technical potential of the main renewable energy resources? (2) what is the overall annual cost of such an energy system once it has been implemented? (3) what is the best combination of renewable energy converters, storage units, energy converters and energy-saving measures? In order to answer these questions, we carried out many simulation calculations using REMod-D, a model we developed for this purpose. This model is described in Part I of this publication. To date this model covers only part of the energy system, namely the electricity and heat sectors, which correspond to about 62% of Germany's current energy demand. The main findings of our work indicate that it is possible to meet the total electricity and heat demand (space heating, hot water) of the entire building sector with 100% renewable energy within the given technical limits. This is based on the assumption that the heat demand of the building sector is significantly reduced by at least 60% or more compared to today's demand. Another major result of our analysis shows that – once the transformation of the energy system has been completed – supplying electricity and heat only from renewables is no more expensive than the existing energy supply. [Copyright &y& Elsevier]

Abstract: A clear consensus exists in the German society that renewable energies have to play a dominant role in the future German energy supply system. However, many questions are still under discussion; for instance the relevance of the different technologies such as photovoltaic systems and wind energy converters installed offshore in the North Sea and the Baltic Sea. Also concerns exist about the cost of a future energy system mainly based on renewable energies. In order to be able to address the raised issues on a scientifically sound basis we have set up a new simulation model REMod-D (Renewable Energy Model-Deutschland) that models the energy balance of the electricity and heat sector including all renewable energy converters, storage components and loads for a future German energy system for a whole year based on an hourly energy balance. The target energy systems modeled use a high fraction up to 100% of renewable energies to cover the electricity and heat demand (heating and hot water). The model includes also energy retrofit of buildings as a measure to reduce future heat loads of the building sector. A mathematical–numerical optimizer is applied in order to identify system configurations with minimal overall annual cost. In this first part of a two-paper series we describe the methodology of the REMod-D model and discuss cost and performance values of all included components and in the second part we will discuss the results. [Copyright &y& Elsevier]

Abstract: Summer air conditioning represents a growing market in buildings worldwide, with a particularly significant growth rate observed in European commercial and residential buildings. Heat-driven cooling technologies are available, which can be used in combination with solar thermal collectors to alleviate the burden caused by air conditioning on the electric utilities and the environment. Solar air conditioning has progressed considerably over the past years as a result of efforts toward environmental protection and new developments in components and systems, and significant experience has been gained from demonstration projects. The main obstacles for large scale application, beside the high first cost, are the lack of practical experience and acquaintance among architects, builders and planners with the design, control and operation of these systems. This paper describes the main results of the EU project SACE (Solar Air Conditioning in Europe), aimed to assess the state-of-the-art, future needs and overall prospects of solar cooling in Europe. A group of researchers from five countries has surveyed and analyzed over 50 solar-powered cooling projects in different climatic zones. The paper presents a short overview on the state-of-the-art and potential of solar-assisted cooling and air conditioning technologies. The results of the study, including a database of the surveyed projects, an evaluation of these projects on a uniform basis, an economic analysis tool, user guidelines and a multimedia tool—are presented. The potential energy savings and limitations of solar thermal air conditioning in comparison to conventional technologies are illustrated and discussed. [Copyright &y& Elsevier]