More than a billion people still lack access to reliable and clean electricity in rural regions throughout the world. To help solving this problem, the OwnWall project proposes to investigate how to build stable, cheap, scalable, robust and renewable energy based electrical installations for rural electrification by using modular, simple and generic elementary building blocks.
Rural electricity access is defined in current literature through a multi-tier framework, ranging from tier 0 (100W max.) to tier 5 (50kW max.). Field feedback shows that high-tier energy needs are provided by complex and expensive electrical installations while lower-tier needs are provided by stand-alone home systems. Neither solution is adapted for user-driven expansion, leading to several issues in current rural electrification programs. Some authors suggest a theoretical missing link between these tiers as a bottom-up electrification approach called “Swarm Electrification”. The tier expansion perspective of Swarm Electrification is illustrated in figure 1, where the level of energy provision and complexity are shown to be linked. A “complexity barrier” represents the difficulties in evolving from low-power, low-voltage stand-alone energy systems to a higher-power, higher-voltage one. The“complexity readiness” represents, qualitatively, the driving factors that must be taken in account to allow tier evolution.
The literature states that swarm electrification requires energy management technology to be user-centered, legacy compatible, multi-tier and adaptive. This assessment has been recently reinforced by IEEE and the World Bank, who stated that a “critical roadblock [to rural electrification] includes the need of an ultra-low-cost communication/control-layer and the need to drive growth through market-pull as opposed to the technology-push models ”.
Rural micro-grids, in the scope of this project, are electric installations composed of an energy architecture that provides an energy strategy. An energy architecture is the interconnection of power converters to connect energy sources, loads and storage elements. An energy strategy is the control provided by some high-level algorithm which determines the energy flow between energy sources, loads and storage elements with the objective of providing services such as uninterrupted energy supply or minimizing the cost of energy. The energy sources studied in this project are photovoltaic generators and small-wind turbines. The loads of interest are either DC or AC.The storage elements which will be used in this work are second-life batteries.
The OwnWall project studies the use of modular power electronics as a means to create a scalable rural micro-grid that can extend itself over time and over a geographical area to connect newly acquired and/or legacy energy sources, loads and storage elements, thus changing tiers. It can provide new services without compromising already existing ones. It has full compatibility between the target ratings of its power converters. It has bi-directional tier compatibility, meaning a scalable rural micro-grid can associate power converters to rise a lower to a higher tier and it can dissociate power converters, going from a higher to a lower tier. All of this at low cost.
The key to this work is to find the appropriate hardware and software that can provide all key functions for different tiers and that can adapt itself to new control constraints and operating conditions. This is where we turn to the TAPAS project. An assessment of requested features has been made by discussing with NGOs and engineers working in power generation for the rural world. Their needs are various as shown in figure 2, but most of them can be performed with the TAPAS three branch architecture. The targeted objective is to develop this configurations using only the TAPAS hardware, while being able to change the power ratings by paralleling several boards. Doing so allows the final user or the local technician to configure and reconfigure the same hardware to fit precise needs. Building a micro-grid would then become a plug-and-play operation, by using always the same individual hardware, but changing their functions on the go.
The enhanced compatibility between the power blocks and their possible combinations provide the versatility needed to deploy a robust energy system relying on several energy sources and storages, constituting as such the first step of a scalable micro-grid while breaking the swarm electrification complexity barrier.
The foreseen set-up will be a direct replication, with TAPAS, from experiments that have already been conducted with similar own-developed hardware that is shown in figure 5, 6 and 7.
Through a funding from the EU smart-grid program ERIGRID, we validated the use of elementary modules to provide:
We are kindly asking four boards to create a micro-grid as shown in Figure 3 by porting our existing algorithms to TAPAS.
We also attach Figure 4 that illustrates functions we seek to validate and where TAPAS could be used in the future.
Luiz Lavado Villa - Associate Professor at the University of Toulouse and Researcher on modular power electronics for bottom-up energy access at the LAAS-CNRS laboratory
Rafael Oliva - Electronics Engineer, master deg in ren.enegy - Teacher at the UNPA, National University of Austral Patagonia - Argentina
Jean Alinei - Mechatronic Engineer graduated from Grenoble INP
Ronan Blanchard - Automatic engineer student at Grenoble INP
Final submission :
Github repo with the code : https://github.com/luizvilla/tapas
Videos playlist showing our progress and presenting the project : https://www.youtube.com/channel/UC-8ZHe8LZpK0sASBeHKvXgA
This idea submission is among the finalists and will be presented at the CKI Conference in Erlangen.