Matching analysis for on-site hybrid renewable energy systems of office buildings with extended indices

The objective of this paper is to close the scientific gap that there is a lack of comprehensive matching analysis for the increasingly complicated on-site hybrid energy systems with a continuously decreased annual primary energy consumption/equivalent CO2 emission. Thus, a thorough matching analysis is conducted for the on-site hybrid systems of two office buildings under distinct climate conditions. Both of the studied buildings are equipped with PV and solar thermal assisted ground source heat pumps (GSHP), which can be controlled by six excess renewable electrical (REe) and one excess renewable thermal (REth) treatments with respect to certain thermal storage recharging and grid exporting strategies. The assessment criteria are six recently defined indices. With the aid of these indices, the key methodology is to conduct parametric analyses from the aspect of matching for solar thermal collector area and connection type, PV panel area, and electrical battery size regarding certain excess REe or REth treatments. The outcomes of matching analyses show the advantages of solar thermal collectors connected in a parallel fashion in meeting office heating demands, the consistency between electrical generation and demand in the daytime in office buildings, the enhancement of on-site heating and cooling by GSHP and free ground cooling, and the battery effect in technically improving electrical matching. Furthermore, the fluctuations of indices in the instantaneous matching analysis clearly reflect the matching situations of on-site renewable energy resources and demand conditions at each time-step, which will be helpful for the detailed investigation of specific system operations and user behaviours. It has been shown that the methodology used in the study can be helpful for aiding the design of increasingly complicated on-site hybrid energy systems.