Evaluating low-temperature heat sources for large-scale heat pump integration: A method using open-source data and indicators

Low temperature (LT) heat sources (HS) below 100 °Ccontain high amounts of renewable energy available in the form of air, water, and ground. If leveraged properly, these heat sourcescan be utilized through large-scale heat pumps and other conversion techniques to supply district heating networks and assist in the energy transition. Therefore, all local municipal heat sources need to be assessed for their potential and availability. Individually assessing each heat source, including air (ambient and exhaust), water (rivers, lakes, oceans, wastewater), and soil (surface and deep geothermal) will contribute to more informed decision-making for municipal energy planners. In this regard, this paper suggests an indicator-based heat source evaluation method using open-source data to analyze potential and availability of local renewable heat sources to support large-scale heat pump implementation into district heating in Germany. The authors present a five-step method that introduces a comprehensive indicator-based procedure: (i) identify heat sources, (ii) evaluate the heat source availability and potential based on technical, economical, ecological and regulatory indicators including an assessment of the quantitative data condition and relevance, (iii) approximate the cost of heat source extraction and supply, (iv) compare the potentials and costs and (v) give recommendations to municipal heat planners. The method is demonstrated in a case study, covering the German city of Fellbach. Following this, insights into promising heat sources are discussed to increase the application and understanding for decision-makers, as well as the risks involved with the temporal uncertainty of heat supply. This article serves as guidance to understand the evaluation of low-temperature renewable heat sources based on a step-by-step indicator calculation.