The environmetal impact of a solar powered CO2 to methanol farm

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Abstract

Zero Emission Fuel (ZEF) has the goal to create affordable high-grade methanol, produced from absorbed carbon dioxide and water from the air. The methanol is produced in a solar methanol (MeOH) farm, consisting of 13225 micro-plants which are powered by PhotoVoltaicsolar panels (PV panels). The solar capacity of the solar MeOH farm is 12 MW and produces 7.8 tons of grade AA methanol per day (grade AA methanol has a purity of 99.8%). One of the main goals of ZEF is to produce methanol with a smaller environmental impact compared to the currently commonly used production methods. A part of the research focuses on an advice for the type of PV panels to use. The main goal of the research is to determine the environmental impact of methanol produced by the solar MeOH farm. The results lead to an advice for ZEF concerning reducing their environmental impact, also the research advises on further research.
To determine the environmental impact a life cycle assessment (LCA) is performed according to ISO 14040 and ISO 14044 standards, using the ReCiPe 2016 method. The midpoint impact categories researched are the global warming potential (GWP), the mineral resource scarcity, and the fossil resource scarcity. The functional unit of the LCA is one ton methanol. A set of assumptions is made concerning the solar MeOH farm, which are tested in the sensitivity analyses. A second LCA is performed, which compares different PV technologies. This LCA focuses on the endpoint impact categories, and the goal of this LCA is to show which PV technologies have the least environmental impact. The PV technology with the smallest environmental impact, polycrystalline silicon PV panels, is used in the LCA concerning the solar MeOH farm. One ton of methanol produced by the solar MeOH farm has a GWP of -835 ± 50 (6.5%) kg CO2 equivalent, proving that the methanol produced by ZEF absorbs CO2. When the end-use of methanol is included, approximately 40% of the methanol produced by ZEF should be used for the production of plastic and chemicals to produce zero-emission methanol. After 7.9 ± 0.8 years of production, the solar MeOH farm has reached the CO2 break-even point. The mineral resource scarcity of one ton methanol produced by the solar MeOH farm is 10.7 ± 0.7 (6.3%) kg Cu equivalent, the fossil resource scarcity is 127 ± 13 (10%) kg oil equivalent, and the energy payback time (EPT) is 6.9 ± 0.7 years of methanol production. The most crucial factor that influences the environmental impact is the amount of equivalent sun hour (ESH), therefore, the solar MeOH farm should operate on a location with a high amount of ESH to decrease the environmental impact. A 1% decrease of micro-plant efficiency increases the environmental impact with more than 1%. The recommendation is to focus on lifetime and efficiency when designing new subsystems, since lifetime is a more important factor than the materials used.