Trends in Cooling Degree Days for Building Energy Estimation in Latvia

Abstract

Calculation of cooling degree days (CDDs) and hours (CDHs) is one of the simplest methods to describe the effect of outside air temperature on building cooling energy consumption. Calculations of CDD numbers and analysis of trends were performed using 10-year data of outdoor temperature, measured at the meteorological station in Riga (Latvia). Values of CDDs and CDHs for seven base temperatures (from 19.0°C to 26.0°C) are provided in a tabular form. Results showed an increase in CDDs by the year 2020. Findings of this study could be further used for energy management in Riga region. I. INTRODUCTION Nowadays the building sector in member states of the European Union accounts for about 40% of final energy consumption and about a third of greenhouse gas emissions, of which about two-thirds are ascribed to residential and one- third to commercial buildings (1). Even though most of energy in eastern European buildings is used for space heating, e.g., about 70% in Latvian households (2), special attention should also be directed towards space cooling, since the energy consumption it accounts for (mostly electrical energy) is growing rapidly. It is expected that energy demand for cooling will increase even more in the future due to global warming, higher demands for quality of life and comfort, an increased use of glazing in architecture, increased number of electric appliances etc. and generally due to economic growth (3). Heating and cooling energy consumption in buildings is mostly affected by outdoor temperature changes (4; 5), where spatial and temporal considerations also play an important role. Several methods are available for energy analysis and estimation of energy demands. These methods differ in complexity, in amount of ambient condition data that needs to be taken into account, time increment used for calculations, detail of description of the building geometry and its characteristics etc. (6). Degree day method is currently the simplest and well-established technique for energy analysis, providing adequate results for simple systems and applications. It is appropriate in cases when the use of building, efficiency of HVAC equipment, indoor temperature and internal gains are relatively constant. Degree day method allows for the comparison of building current and past energy performance, as well as the comparison of buildings in different climate zones. In (7) cooling degree day data for 171 countries was summarized, where Mali and Nigeria were ranked 1 st and 2 nd for having the highest number of cooling