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  • 1.
    Lorenzi, Guido
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Techno-economic analysis and optimization of electrochemical energy storage solutions2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The need to integrate the rapidly growing share of variable renewable energy sources in the power sector requires solutions that are capable of mitigating the intermittent nature of these sources. They are expected to constitute the backbone of the electricity generation system in the coming years in order to reach ambitious goals in terms of energy security and reduction of environmental impact. Energy storage appears a promising solution to improve the capability of variable renewable plants to meet the energy demand at all times, mainly through the re-allocation of the generation surplus.

    Among the several options that can favor the integration of variable renewables, electrochemical storage technologies - batteries and electrolysis cells - constitute the focus of this dissertation. These approaches can be used to defer substantial quantities of energy for medium to long time intervals, are largely location independent, and are considered a strategic part of the decarbonization pathway in the European Union, which represents the geo-political framework under investigation.

    Battery storage systems are analyzed in both small- and large-scale settings to quantify the energetic and economic benefits deriving from a more efficient use of renewable energy. A small-scale battery system connected to a residential PV plant is analyzed and the results are compared to a demand response strategy for load shifting. The integration of a large-scale battery facility in the energy system of an island is also simulated and the results show a much lower level of renewable energy curtailment. In both the situations the projected costs of the battery technologies are used to assess their techno-economic performance.

    Solid oxide electrolysis cells (SOECs) as employed in power-to-gas upgrading of biogas constitute the second electrochemical energy storage pathway that was studied. The upgrading process sought to increase the methane content in the biogas by directly converting the embedded carbon dioxide through high-temperature electrolysis and methanation. This process showed energy conversion efficiencies higher than 80%. However, its economic viability depends on the cost of electricity, the cost of the core components, and the price of natural gas.

  • 2.
    Lorenzi, Guido
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Univ Lisbon, Inst Super Tecn, IN Ctr Innovat Technol & Policy Res, Ave Rovisco Pais 1, P-1049001 Lisbon, Portugal..
    Baptista, Patricia
    Univ Lisbon, Inst Super Tecn, IN Ctr Innovat Technol & Policy Res, Ave Rovisco Pais 1, P-1049001 Lisbon, Portugal..
    Promotion of renewable energy sources in the Portuguese transport sector: A scenario analysis2018In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 186, p. 918-932Article in journal (Refereed)
    Abstract [en]

    Transport is one of the sectors of the energy consumption where the presence of renewable energies is lower and its increase is hard to achieve especially in countries that import all the fuels that they consume. This paper addresses the progress that Portugal is making toward a more sustainable transport sector. A near- and medium-term scenario analysis is performed, based on the energy consumption in the past and on a detailed evaluation of the trends for renewable energy in the transport sector. The near term scenarios aim at portraying the conditions that allow the country to fulfill the target of 10% renewable share in transportation established by the European Union. The medium-term scenarios highlight the implications, in terms of emission reduction and of energy independence, deriving from the use of electric vehicles and natural gas, synthetic and fossil, as alternatives to liquid fuels. The results show that electric vehicles would substantially reduce the total energy consumption and the greenhouse gas emissions, while the promotion of routes for synthetic natural gas would contribute to taking advantage of local resources. The paper also provides some insights about the design of future policies to build a more sustainable transport sector. 

  • 3.
    Lorenzi, Guido
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. IN+, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.
    da Silva Vieira, Ricardo
    MARETEC/LARSYS, Environment and Energy, Scientific Area, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.
    Santos Silva, Carlos Augusto
    IN+, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.
    Martin, Andrew R.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Techno-economic analysis of utility-scale energy storage in island settingsIn: Journal of Energy Storage, E-ISSN 2352-152XArticle in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    The decarbonization of the electricity supply in isolated and remote energy systems is an open challenge in the transition to a sustainable energy system. In this paper, the possibility to increase the penetration of renewable energy sources for electricity generationon the island of Terceira (Azores) is investigated through the installation of a utility-scale energy storage facility. The electric power dispatch on the island is simulated through a unit commitment model of the fossil and renewable power plants that has the objective of minimizing the cost of electricity generation. Battery energy storage is employed to partially decouple production and supply, and to provide spinning reserve in case of sudden generator outage. Two technological options, namely lithium-ion and vanadium flow batteries, are compared in terms of net present value and return on investment, with the aim of supporting the decision-making process of the local utility. The economic evaluation takes also into account the degradation of the battery performance along the years. The results, obtained in a future-price scenario, show that both the technologies entail a positive investment performance. However, vanadium flow batteries have the best results, given that they produce a net present value of up to 242% of the initial capital invested after 20 years, with a return on investment higher than 20%. In this scenario, the renewable share can reachup to 46%, compared to the current 26%.

  • 4.
    Lorenzi, Guido
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. Department of Energy (DENERG), Politecnico di Torino, Torino, Italy.
    Lanzini, Andrea
    Department of Energy (DENERG), Politecnico di Torino, Torino, Italy.
    Santarelli, Massimo
    Department of Energy (DENERG), Politecnico di Torino, Torino, Italy.
    Digester Gas Upgrading to Synthetic Natural Gas in Solid OxideElectrolysis Cells2015In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 29, no 3, p. 1641-1652Article in journal (Refereed)
    Abstract [en]

    This work focuses on the process design and performance of an innovative plant for digester gas upgrading tosynthetic natural gas (SNG). The differences and advantages over traditional upgrading processes are discussed. The mainstrength of digester gas upgrading via high-temperature electrolysis concerns its higher synthetic natural gas productivity for agiven raw digester gas feed. Electrolysis is performed through a solid oxide electrolysis cell (SOEC) system, which is fed withdemineralized water and purified digester gas (made up of methane and carbon dioxide). Surplus electricity from intermittentrenewable energy sources is used to supply the energy required for the SOEC stacks. The resulting methane-rich syngas isreacted in a series of methanators to yield a high CH4 content output stream. The steam reforming reaction is promoted bymeans of a nickel catalyst in the cathode (fuel) electrode, which reduces the methane fraction: hence, sulfur, which is present inseveral types of digester gas (e.g., from sewage or landfills) in the form of hydrogen sulfide, has been identified as a possibleinhibitor for this reaction. However, it is also well-known that sulfur is responsible for the deterioration of the electrochemicalperformance of a stack. Therefore, its effect on the system has been modeled for different thermodynamic conditions. This studyanalyses the electrochemical and energy performance of the integrated process through which all the carbon contained in digestergas is converted/upgraded to methane-rich gas. The electrochemical dissociation of the CO2 contained in the digester gas to CH4(with the addition of external demineralized water) is one way of cleverly exploiting the carbon content in digester gas when poorquality or limited biological substrates are available for anaerobic digestion. Finally, a comparison with other commercial digestergas upgrading techniques has been made.

  • 5.
    Lorenzi, Guido
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Universidade de Lisboa, Portugal.
    Lanzini, Andrea
    Santarelli, Massimo
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Politecnico di Torino, Italy.
    Martin, Andrew R.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Exergo-economic analysis of a direct biogas upgrading process to synthetic natural gas via integrated high-temperature electrolysis and methanation2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 141, p. 1524-1537Article in journal (Refereed)
    Abstract [en]

    Biogas upgrading to synthetic natural gas (SNG) is a viable and appealing route for power-to-gas because it combines waste management with the use of the surplus electricity that might arise in energy systems having a considerable share of renewable energy sources in their production mix. In this work, the exergo-economic performance of a biogas upgrading process through integrated electrolysis and methanation is assessed in connection with the current market status to test which conditions could make the proposed option economically viable. Two different configurations, which differ mainly for the operating pressure of the electrolyser, are compared. The exergy efficiencies are high (>80%) and exergo-economic costs of the produced bio-SNG in the two analyzed configurations are 5.62 and 4.87 c(sic)/kWh(exergy), for low- and high-pressure respectively. Lower values would be required for the bio-SNG to compete with fossil natural gas. We show how both the input electricity price and the capacity factor have a substantial impact on the economic sustainability of the process. Eventually, the monetary exploitation of the oxygen produced by electrolysis and the participation to the emission trading scheme could contribute further to improve the economic attractiveness of the process.

  • 6.
    Lorenzi, Guido
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. IN+, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.
    Santos Silva, Carlos A.
    IN+, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.
    Techno-economic comparison of storage vs. demand response strategies in distributed generation systems2015In: 2015 12th International Conference on the European Energy Market (EEM), IEEE, 2015Conference paper (Refereed)
    Abstract [en]

    This paper investigates the benefits in terms of energy use and cost reduction of electricity storage using batteries and the implementation of demand response strategies, to mitigate the mismatch between the renewable production and the demand in smart grids. A comparison between the two approaches in a household with micro-generation system is made in order to assess which one is the most feasible for small scale users. The results show that in general the use of demand response has more benefits to the end-user.

  • 7.
    Lorenzi, Guido
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Univ Lisbon, Inst Super Tecn.
    Santos Silva, Carlos Augusto
    Comparing demand response and battery storage to optimize self-consumption in PV systems2016In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 180, p. 524-535Article in journal (Refereed)
    Abstract [en]

    The paper examines and compares the potential of storage in batteries versus demand response strategies for electricity bill reduction in the residential sector, in the context of the new trend of installing PV systems for self-consumption. The performances of the two methodologies are investigated by applying them to the data of a real household which owns a small solar photovoltaic installation. The benefits of storage and demand response are evaluated through an optimization analysis with a linear programming algorithm. The simulations are carried out both for real market prices of the equipment and for reduced ones, to simulate the case of strong technological development and the corresponding price decrease in the coming years. The electricity pricing scheme is a dual tariff regime modeled according to the Portuguese current rules. The results suggest that at the moment, demand response should be preferred with the current market prices of the hardware. However, a significant decrease in the batteries price can make storage an interesting alternative, especially for the cases in which demand response is not easily applicable.

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