Energy flexibility of nearly zero energy buildings and its influence on energy matching and grid interactions

Abstract

In this thesis definitions and indicators for energy flexibility of buildings are reviewed and evaluated in the context of nearly zero energy buildings, energy matching and grid interactions. The thesis approaches energy flexibility of buildings from the building perspective. Focus is set on the evaluation of the flexibility a building system can achieve. Objective of the thesis is to treat the whole building system rather than to focus on single parts of it. Available definitions for energy flexibility of a building are reviewed and a comprehensive definition is framed: “The ability of a building system to change its energy or power characteristics for a certain time period without influencing the designated utilization of the building.” The goal is to collect available flexibility, matching and grid interaction indicators, to categorize and evaluate them and to propose possible developments. Recent research shows that energy matching and grid interaction are not congruent with energy flexibility. Nevertheless the three topics still correlate, as energy flexibility is a suitable tool on the path towards energy matching. Energy matching is not only the goal for the building system itself, but the whole energy market needs matching of demand and generation to achieve highest efficiency. The most suitable indicators are undergoing further investigation. Differences in important parts of the simulation like the reviewed period, the price signal or the demand influence the performance of the indicators and may foil their original meaning. The selected indicators are evaluated based on a TRNSYS simulation of a single family house in Helsinki, Finland. All indicators are calculated based on the same simulation consisting of 18 cases to evaluate their adaptability for a general assessment of energy flexibility of buildings.