Energy system analysis of a pilot net-zero exergy district

Abstract

The Rational Exergy Management Model (REMM) provides an analytical model to curb primary energy spending and CO2 emissions by means of considering the level of match between the grade/quality of energy resources (exergy) on the supply and demand sides. This model is useful for developing forward-looking concepts with an energy systems perspective. One concept is net-zero exergy districts, which produce as much energy at the same grade or quality as consumed on an annual basis. This paper analyzes the district of Östra Sala backe in Uppsala Municipality in Sweden as a pilot, near net-zero exergy district. The district is planned to host 20,000 people at the end of four phases. The measures that are considered include an extension of the combined heat and power based district heating and cooling network, heat pumps driven on renewable energy, district heating driven white goods, smart home automation, efficient lighting, and bioelectricity driven public transport. A REMM Analysis Tool for net-zero exergy districts is developed and used to analyze 5 scenarios based on a Net-Zero Exergy District Option Index. According to the results, a pilot concept for the first phase of the project is proposed. This integrates a mix of 8 measures considering an annual electricity load of 46.0GWhe and annual thermal load of 67.0GWht. The exergy that is produced on-site with renewable energy sources is 49.7GWh and the annual exergy consumed is 54.3GWh. The average value of the level of match between the demand and supply of exergy is 0.84. The paper concludes with advice for a more efficient usage of energy resources in the energy systems of net-zero exergy districts of the future.