Life cycle assessment of concentrated solar power (CSP) and the influence of hybridising with natural gas

Abstract

Purpose Concentrating Solar Power (CSP) plants based on parabolic troughs utilize auxiliary fuels (usually natural gas) to facilitate start-up operations, avoid freezing of HTF and increase power output. This practice has a significant effect on the environmental performance of the technology. The aim of this paper is to quantify the sustainability of CSP and to analyse how this is affected by hybridisation with different natural gas (NG) inputs.Methods A complete Life Cycle (LC) inventory was gathered for a commercial wet-cooled 50 MWe CSP plant based on parabolic troughs. A sensitivity analysis was conducted to evaluate the environmental performance of the plant operating with different NG inputs (between 0 and 35% of gross electricity generation). ReCiPe Europe (H) was used as LCA methodology. CML 2 baseline 2000 World and ReCiPe Europe E were used for comparative purposes. Cumulative Energy Demands (CED) and Energy Payback Times (EPT) were also determined for each scenario.Results and discussion Operation of CSP using solar energy only produced the following environmental profile: climate change 26.6 kg CO2 eq/KWh, human toxicity 13.1 kg 1,4-DB eq/KWh, marine ecotoxicity 276 g 1,4-DB eq/KWh, natural land transformation 0.005 m 2 /KWh, eutrophication 10.1 g P eq/KWh, acidification 166 g SO2 eq/KWh. Most of these impacts are associated with extraction of raw materials and manufacturing of plant components. The utilization NG transformed the environmental profile of the technology, placing increasing weight on impacts related to its operation and maintenance. Significantly higher impacts were observed on categories like climate change (311 kg CO2 eq/MWh when using 35 % NG), natural land transformation, terrestrial acidification and fossil depletion. Despite its fossil nature, the use of NG had a beneficial effect on other impact categories (human and marine toxicity, freshwater eutrophication and natural land transformation) due to the higher electricity output achieved. The overall environmental performance of CSP significantly deteriorated with the use of NG (single score 3.52 pt in solar only operation compared to 36.1 pt when using 35 % NG). Other sustainability parameters like EPT and CED also increased substantially as a result of higher NG inputs. Quasilinear second-degree polynomial relationships were calculated between various environmental performance parameters and NG contributions.Conclusions Energy input from auxiliary NG determines the environmental profile of the CSP plant. Aggregated analysis shows a deleterious effect on the overall environmental performance of the technology as a result of NG utilization. This is due primarily to higher impacts on environmental categories like climate change, natural land transformation, fossil fuel depletion and terrestrial acidification. NG may be used in a more sustainable and costeffective manner in combined cycle power plants, which achieve higher energy conversion efficiencies.

Interpretation of comparative LCAs: external normalization and a method of mutual differences

“…Impact categories most salient in EU and World references replicate across the four LCA applications indicating the possibility of a systematic bias in the normalization approach. With the exception of Kasah (2014), this same pattern in ReCiPe externally normalized results was found in recent LCA applications such as concentrated solar power (Corona et al 2014), structural beams (Ibbotson and Kara 2013), industrial cleaning products (Kapur et al 2012), diapers (Mirabella et al 2013), laundry detergents (Prado-Lopez et al 2014), energy recovery from rice husks (Prasara-A and Grant 2011), and dishwashing soap (Van Hoof et al 2013).…”

Life Cycle Assessment of a HYSOL Concentrated Solar Power Plant: Analyzing the Effect of Geographic Location

“…On the contrary, the environmental impact of the HYSOL plant increases significantly when it is operated with natural gas as the auxiliary fuel. Still, the carbon footprint of the HYSOL configuration operating with 55% of natural gas hybridization resulted to be 294 kg CO 2 eq/MWh, which is lower than the 311 kg CO 2 eq/MWh obtained for a conventional hybrid parabolic trough CSP plant hybridized with only 35% of natural gas and also lower than conventional power plants based on the combustion of natural gas using combined cycle technology (365-425 kg CO 2 eq/MWh) [18,28,29].…”

“…Life Cycle Assessment (LCA) is an appropriate methodology to evaluate the environmental performance of renewable technologies, as has been proven in scientific literature [7][8][9]. The environmental impacts of conventional CSP plants have been previously evaluated by the scientific community [10][11][12][13][14][15][16][17][18][19][20]. These analyses are all based on LCA methodology, and evaluate the environmental performance of CSP plants of varying capacity, operating with different technologies (parabolic trough/Fresnel reflectors, central tower, Stirling dish), including specific component characteristics (air/wet cooling, thermal storage technology) and hybridization with different fuels.…”

Prospective Analysis of Life-Cycle Indicators through Endogenous Integration into a National Power Generation Model

“…Then, Data acquisition is required to quantify the input and output flows associated with the power generation technologies listed in Table 1. Inventory data for the new technologies, i.e., those potentially participating in the electricity production mix according to the optimisation of each scenario, are based on specific literature: coal thermal power plants with/without capture [37][38][39], NGCC with/without capture [40,41], nuclear fission (III and IV generation) [42,43], nuclear fusion [44], cogeneration [45], hydropower dam and run-of-river plants [46], wind farms [47,48], tidal power [49], wave power [50], photovoltaics (open-ground and rooftop systems) [51], concentrated solar power plant with/without storage [52,53], geothermal (binary cycle) power plants [54], bioresource technology (biomass integrated gasification combined cycle, biogas and waste-to-energy plants) [55][56][57], PEMFC [58], and SOFC [59]. Finally, data for both existing technologies and background processes are retrieved from the ecoinvent database [60].…”