Comparison of LCA results of low temperature heat plant using electric heat pump, absorption heat pump and gas-fired boiler

• Usage of geothermal heat pump can bring environmental benefits.
• The lowest environmental impact for whole life cycle is obtained for absorption heat pump.
• The value of heat pump COP has a significant influence on environmental impact.
• In case of coal based power generation the damage to human health is significant.

This study compares the life cycle impacts of three heating plant systems which differ in their source of energy and the type of system. The following heating systems are considered: electric water-water heat pump, absorption water-water heat pump and natural gas fired boiler. The heat source for heat pump systems is low temperature geothermal source with temperature below 20 °C and spontaneous outflow 24 m3/h. It is assumed that the heat pumps and boiler are working in monovalent system. The analysis was carried out for heat networks temperature characteristic at 50/40 °C which is changing with outdoor temperature during heating season.The environmental life cycle impact is evaluated within life cycle assessment methodological framework. The method used for life cycle assessment is eco-indicator ‘99. The functional unit is defined as heating plant system with given amount of heat to be delivered to meet local heat demand in assumed average season. The data describing heating plant system is derived from literature and energy analysis of these systems. The data describing the preceding life cycle phases: extraction of raw materials and fuels, production of heating devices and their transportation is taken from Ecoinvent 2.0 life cycle inventory database.The results were analyzed on three levels of indicators: single score indicator, damage category indicators and impact category indicator. The indicators were calculated for characterization, normalization and weighting phases as well. SimaPro 7.3.2 is the software used to model the systems’ life cycle. The study shows that heating plants using a low temperature geothermal source have lower eco-indicator than a gas boiler unit. In comparison of two heat pumps the absorption heat pump has a lower environmental impact rather than electrical heat pump. However, in spite of high level eco-indicator, gas boiler has the lowest damage to human health.