This equation is not intended as a general correlation for packing media, It is presented to stress the fact that the Ergun equation, advanced by several textbooks without restriction to flow range, may not be applicable for values of Re/ (1 -e) greater than about 500.
We present a comparison of solar thermal and solar electric cooling for a typical small office building exposed to two different European climates (Freiburg and Madrid). The investigation is based on load series for heating and cooling obtained previously from annual building simulations in TRNSYS. A conventional compression chiller is used as the reference system against which the solar options are evaluated with respect to primary energy savings and additional cost. A parametric study on collector and storage size is carried out for the solar thermal system to reach achieve the minimal cost per unit of primary energy saved. The simulated solar electric system consists of the reference system, equipped with a grid connected photovoltaic module, which can be varied in size. For cost comparison of the two systems, the electric grid is assumed to function as a cost-free storage. A method to include macroeconomic effects in the comparison is presented and discussed. Within the system parameters and assumptions used here, the grid coupled PV system leads to lower costs of primary energy savings than the solar thermal system at both locations. The presumed macroeconomic advantages of the solar thermal system, due to the non-usage of energy during peak demand, can be confirmed for Madrid
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.