Trigeneration from renewable energies : based on the example of the biomass plant in Vienna in connection to the Vienna central railway station

Abstract

Over the past centuries, economic growth and technological progress have led to increased prosperity and a higher standard of living. In parallel, energy demand has risen and will continue to do so in the future. Heating, refrigeration and cooling technologies make up a significant part of energy utilization in most countries. Therefore, it is important regularly to analyze and evaluate these energy technologies from an economic and environmental perspective. This thesis examines the economic and environmental feasibility of a trigeneration system, i.e., the simultaneous production of heating, cooling and power (electricity) through a cash-flow analysis, by comparing an absorption chiller to a -traditional- compression chiller. To do so, the author has used a model based on the city of Vienna, Austria, and hypothesizes that the forest biomass power plant (FBPP) in Vienna-Simmering provides, with priority, energy and warmth to the Vienna central railway station. There, the warmth (i.e., waste heat) is converted to district-cooling (i.e., chilled water for air-conditioning) through use of an absorption-chiller. This thesis concludes that absorption cooling, driven by waste heat from the FBPP, is more feasible than compression cooling, driven solely by electricity. The production costs of cold are 33 per cent cheaper in the absorption chiller compared to a compression chiller. The latter furthermore has a 2.8 times higher CO2 emission rate, as absorption chillers do not emit any greenhouse gases. It can therefore be stated that absorption cooling is a promising future technology, as it produces cooling in an environmentally-friendly way, thereby reducing the need to use electricity-intensive compression chillers that have high CO2 emissions. The future to mitigating climate change and reducing greenhouse gas emissions, especially CO2, lies in the efficient re-design of energy systems. Trigeneration is a promising technology with numerous application possibilities, having the benefit of utilizing low-cost heat in summer months that would otherwise go to waste to generate cold in an economic way.