Titolo della tesi: An integrated approach to decentralised renewable energy systems planning for developing countries
Title: An integrated approach to decentralised renewable energy systems planning for developing countries
This thesis focuses on the problem of global access to energy for developing countries and provides a thorough analysis of renewable-based mini-grid systems as a solution.
In the first section an intensive literature review shows current energy trends and challenges, with a special outlook on Sub-Saharan Africa. The energy forecast situation is assessed by combining data about electric consumptions patterns with an analysis based on the energy indicators for sustainable development issued by International Agencies. A proven methodology for the energy need assessment of rural communities is presented, aiming at obtaining reliable input data for the mini-grid development. This helps in reducing both the financial challenges by mitigating the uncertainties in electricity demand and the technical challenges by contributing to adequately size off-grid power generation systems, with a view to boost toward a common overall objective of mini-grid’s optimization methods and tools.
Based on methodology outputs an integrated approach for system design and planning is developed, taking into account techno-economic trade-off and system reliability and flexibility.
Design process optimization is carried out through simulation of different combination of generation (PV, Wind, Hydro, multi-source) and storage systems (lead-acid, lithium, vanadium flow, flywheel). Distribution grid constraints have been addressed as well, including last-mile connections and users’ wiring, in order to have an holistic vision in the design phase. Such integrated approach requires to adopt appropriate operation strategies to face real time power quality (voltage and frequency) fluctuations along with an effective capability to meet off-takers demand. Dump loads, device controllers and management options are discussed for both supply-side and demand-side.
The thorough analysis looks at economic aspects, therefore different operating strategies are investigated, and business performance has been deeply analysed and discussed. On a view to a global evaluation impact assessment, last part of the thesis focuses on sustainability analysis: beyond economic impact, other direct/indirect effects of mini-grids on environment and target communities are outlined. The tool used for Monitoring and evaluation of mini-grid is the Social Return on Investment ( SROI), by adding a wide set of key indicators to measure monetized effects on education, health, security, environment and economy.
The combination of all methodologies and strategies aims at improving the systems design and operation, helping reduce capital expenditures and operating costs, thus allowing for a lower Levelized Cost of Energy over project’s entire lifecycle
Chapter 1: Research Statement
Introduction on research aim, methodology, outcomes, and novelty contribution
Chapter 2: Global access to energy
This chapter introduces the theme of energy access within a global perspective and in particular reference to developing countries (DCs).
This chapter depicts the current energy trends and challenge, with a special outlook on Sub-Saharan Africa. The energy current and forecast situation is assessed by combining data about consumptions patterns and electric sector with an analysis based on the Energy Indicators for Sustainable Development issued by International Agencies.
In particular, emphasis is given to the issue of electrification which is pivotal in promoting local development and it is the focus of the following chapters.
This chapter sources information from literature review, as listed in the Bibliography.
Chapter 3: Demand analysis
This chapter describes the development, implementation and application of a new procedure to address end-uses load profile estimate in rural areas. The procedure allows having a tool which is a support to develop the proper input data required by the most advanced off-grid systems sizing methods and software tools.
Thus, the approach for applying a proven methodology for the energy need assessment of rural communities aims at obtaining reliable input data for the mini-grid development. This helps in reducing both the financial challenges by mitigating the uncertainties in electricity demand and the technical challenges by contributing to adequately size off-grid power generation systems, with a view to boost toward a common overall objective of mini-grid’s optimization methods and tools.
Hence, taken in consideration that target communities differ in terms of needs and context conditions, this chapter describes an inclusive methodology that can be adapted case-by-case. It provides an effective applied solution the lack of proven guidelines from project developers or literature, giving priority to data collection methods able to achieve a large sample representative of the market, with high accuracy in estimating the energy consumptions from electricity substitutes.
The implementation of the procedure is also presented and finally, the procedure has been applied in forecasting the average load profile and sizing of 3 off-grid PV-battery-diesel systems in rural Rwanda.
This chapter is based on the paper PA-1: Methodology for the Energy Need Assessment to Effectively Design and Deploy Mini-Grids for Rural Electrification. Gambino V., Del Citto R., Cherubini P., Tacconelli C., Micangeli A., Giglioli R. Energies 2019, 12(3), 574; doi.org/10.3390/en12030574
Chapter 4: Technology integration
This chapter focuses on off-grid small-scale power systems which represent one of the most appropriate energy strategies to address rural electrification. Specifically, the chapter introduces the architecture of renewable energy-based mini-grids, describes the main features of generation and storage systems components and technical specification.
The main aim is to explore opportunities for different technologies combination, with benefits and drawbacks; on this purpose an analysis of potential hybridization of storage technologies is deeply investigated, by simulating an enhanced mechanical and electrochemical ESS within an operating advanced mini-grid. The case study is the Kitobo Island power plant in Uganda, equipped with vanadium flow battery systems, on which the author’s field work mainly was focused along this research period.
Above mentioned analysis will be the basis, in the following chapters, for the development of methods and models which address more specifically the system design process.
This chapter is based on the paper PA-2: How hybridization of energy storage technologies can provide additional flexibility and competitiveness to microgrids in the context of developing countries. Barelli, L.; Bidini, G.; Cherubini, P.; Micangeli, A.; Pelosi, D.; Tacconelli, Carlo. Energies 12:16(2019), p. 3138. doi.org/10.3390/en12163138.
Chapter 5: System Design
This chapter deals with a first step development, implementation and application of a new approach to perform a system capacity planning. Particular features of the procedure are the capability to address more available renewable energy sources to be employed in the system planning.
An enhanced method which considers techno-economic trade-off with a strong need of ensuring system reliability and durability, according to the evolution of energy demand over time as forecast in Chapter3.
Specifically, in the chapter it is highlighted that the need as input datum – in the traditional sizing techniques – of the Loss of Load parameter, may lead to un-appropriate sizing in rural areas. Therefore, an appropriate sizing methodology which embraces the new definitions of the Value of Lost Load parameter and of the Levelized Cost of Supplied and Lost Energy objective function is developed and described. Comparisons between the traditional methodologies and the new one are carried out in order to highlight the appropriateness of the latter as regards rural areas. Moreover, the new methodology is applied to perform optimum sizing of a PV-Hydro-BESS mini-grid in DR Congo as reference case for energy balancing simulation.
This chapter is based on the results of the project PR-4: Sustainable energy Services for Idjwi island (Democratic Republic of Congo, 2019-20). 150 kWp hydroelectric and PV solar multi-source mini-grid for 800 customers. Partner: AVSI Foundation and Ministry of Environment of the DRC.
Chapter 6: Distribution
This chapter deals with different options for rural electrification distribution systems. Existing low-cost technologies are reported from literature review, with an eye to the appropriateness and adequacy of selected context.
Users’ connection and metering options are presented in order to highlight the role of energy dispatch and off-takers.
Energy losses may be relevant in the distribution side due to voltage drop, materials inadequacy, incorrect planning, energy theft so an appropriate example of designing and basic engineering process is presented, based on the Idjwi mini-grid project.
This chapter is based on the results of the project PR-4: Sustainable energy Services for Idjwi island (Democratic Republic of Congo, 2019-20). 150 kWp hydroelectric and PV solar multi-source mini-grid with LV distribution network reaching up to 800 customers. Partner: AVSI Foundation and Ministry of Environment of the DRC.
Chapter 7: Operation
This chapter deals with a new approach to allow developing simplified integrated analyses of dispatch strategies and real time power control. In the previous Chapters the discussion over capacity planning and system sizing mainly looked at energy metrics. Nevertheless, during operations there can be power quality issues in small time-steps, which need to be addressed. Voltage and frequency fluctuation are explained and supply technologies (dump loads, flywheel) and management options (demand-side actions, Internet of Things, smart metering) are proposed embracing simplified electrical models of system components in order to address optimal dispatch strategy.
In the reference study, an analysis of wind production data generated from one year of actual wind data is used to test the power smoothing performance of a range of battery systems with various storage and power ratings. Different ramp rates thresholds and the effect on battery durability where also assessed. Wind generation ramp rates end up causing voltage and frequency issues in grids or supply limitations in microgrids, which can effectively be limited using energy storage.
The chapter brings in the case study of the papers PA-3: Ramp rate abatement for wind power plants: A techno-economic analysis. G.F. Frate, P. Cherubini, C. Tacconelli, A. Micangeli, L. Ferrari, U. Desideri. Applied Energy, Volume 254, 2019, 113600, doi.org/10.1016/j.apenergy.2019.113600 and PA-4: Ramp rate abatement for wind energy integration in microgrids. Frate G.F., Cherubini P., Tacconelli C., Micangeli A., Ferrari L., Desideri U., Energy Procedia 159 (2019) 292-297; doi: 10.1016/j.egypro.2019.01.013
Chapter 8: Economic evaluation
In this Chapter the study classifies and analyses business models of 21 mini-grid projects in Sub-Saharan Africa, identified among 32 pre-selected cases on the basis of selection criteria which took into consideration: i) geographic coverage; ii) location; iii) technological solution; iv) services provided; v) system size; vi) source of power; vii) project status.
Process for identification of the most promising business models has gone through the analysis of project techno-economic, social and operational parameters. Four main business models are highlighted as a way to suggest possible integrated approaches, exploring private-led, public-private, private-community as well as private-private models. Each model presents a different integration of productive uses of energy and energy-related services: provision of electrical appliances, agro-business activities, water and irrigation supply, cooling services, storage solutions and complementary activities such as micro-credit and technical assistance.
The chapter is based on the publication PU-1: RE-thinking Access to Energy Business Models. Ways to Walk the Water-Energy-Food Nexus Talk in Sub-Saharan Africa. Gambino V., Tacconelli C., Micangeli A., et al. RES4Africa Foundation, 2019. ISBN 978-88-492-3804-4.
Chapter 9: Sustainability analysis
It this Chapter a thorough impact assessment has been revealed. Beyond economic impact, other direct/indirect effects of mini-grids on environment and target communities are outlined. A possible tool is presented for mini-grids monitoring and evaluation, called Social Return on Investment (SROI), using a wide set of key indicators to measure monetized effects on education, health, security, environment and economy. The research study on SROI regards 2 mini-grid projects in Uganda: Kitobo and Bukasa Islands, where interviews and field surveyed helped to provided substantial data for a first preliminary analysis.
The chapter is based on the ongoing projects PR-5: Energy and training for a sustainable growth in Bukasa island (Uganda, 2017-19). 100 kWp hybrid solar PV and LV distribution smart grid for 500 connections. Partner: Absolute Energy. And PR-6: Sustainable energy services for Kitobo island (Uganda, 2017-19). 228 kWp solar PV with vanadium redox flow battery storage, diesel backup and LV distribution smart grid. Partner: Absolute Energy.
Chapter 10: Conclusions.
A summary of thesis contributions is given, and future research directions are discussed. Recommendations are outlined for projects developers and operators, along with strength and weaknesses of the study outcomes, paving the way for future models’ improvement.