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Swarm Electrification
Swarm electrification is a decentralized electrification approach where individual solar home systems (SHS) are linked together to form a DC microgrid.Swarm electrification uses existing SHS in a community and links them with smart electricity meters (swarm meters) to control power flow and allows excess energy trading between individuals. The swarm microgrid is scalable in capacity as it is DC based and has decentralized generation. If more SHS are linked to the swarm microgrid, the system increases in robustness and availability of power capacity. Households without SHS can gain energy access by purchasing a swarm meter for their batteries to connect to the swarm microgrid and then can purchase excess energy from their neighbours. The strategy of swarm electrification is to transition populations with low tier energy access to a higher tier with increased energy security.

History of Development The term “swarm electricity” was first introduced by the German company Lichblick as the energy for the future. The same concept, although not coined as swarm electrification, came up in an Institute of Electrical and Electronics Engineers (IEEE) contribution in 2012 in Montreal. In 2013, a non-academic publishing of an overview on swarm electrification was completed by Microenergy systems (MES) research group from TU Berlin. The idea of swarm electrification was developed from the observation of the growing number of stand-alone, small-scale energy systems for non-electrified rural populations in developing countries but the populations were still constrained by energy availability limitations. Limitations like decreasing efficiency of SHS caused by the individual use of the system such as not fully utilizing the electricity stored in their batteries resulting in full batteries by midday limiting the generation potential of their systems. For example, Bangladesh is the fastest growing SHS market in the world with approximately 3 million SHS installed in Bangladesh through microcredit schemes implemented by Partner Organizations (POs) selling at a rate of 45,000–70,000 systems per month. Despite the large number of rural off-grid households that have a SHS, many do not fully utilize their electricity or in contrast, require electricity beyond what their energy systems can supply. This group has been referred to as the “temporarily on/off-grid sector” and was identified as ideal for energy excess sharing using swarm electrification. “This approach can be linked to the concept of swarm intelligence, where each individual node brings independent input to create a conglomerate of value even greater than the sum of its parts”.

Swarm Electrification Techniques and Technology Evolutionary Electrification To implement swarm electrification, it is important to build on existing resources such as previously purchased SHS, diesel generators, batteries or other small-scale energy devices, to include all stakeholders that may possess some type of electrical equipment, as well as to ensure their commitment and acceptance. In addition, since a wide variety of electricity sources might be used, they have to be compatible with the intelligent control units (e.g. biomass gasification, liquid fuel generators, micro-hydro, small-scale wind, etc.). For these reasons, the swarm electrification is the transitional phase of an evolutionary electrification approach that is presented in three phases: going from a small-scale distributed generation, interconnecting this into a micro-grid, to eventually connect the micro-grid to a centralized grid. Figure 1 outlines main steps of the evolutionary bottom-up electrification process.

Figure1. Evolutionary Electrification Strategy

Initial Phase – Isolated small-scale distributed generation In the first phase is defined by households having stand-alone generation systems such as Pico PV and SHS. Approximately, 200Wh daily capacity (Tier 2 energy access) can be achieved with a the stand-alone SHS or PicoPV at each household. The advantages of small-scale energy system are their low complexity and thus their dissemination to rural households can take place more rapidly and affordably when combined with end-user micro-financing. Approximately, 200Wh daily capacity (Tier 2 energy access) can be achieved with a the stand-alone SHS or PicoPV at each household.

Swarm Electrification – Autonomous Microgrid In the swarm electrification phase, the individual household systems are connected step-by-step to form scalable DC microgrids. The individual household systems are connected with a smart electricity meter that facilitate peer-to-peer electricity trade which reduces excess energy and gives users the opportunity to earn money real-time. Swarm microgrids do not increase generation capacity but utilizes surplus energy production not used by individual households. As the swarm DC microgrid increases in number of SHS connections the excess energy increases power availability to the users connected as well as the networks robustness. The swarm network increases usage flexibility and reliability  productive and efficient use of energy by allowing users to easily access to small productive power appliances, such as a water pump or a fridge. The swarm grid can not only grow from a single SHS to a village based micro-grid but extend to other villages and thereby create bottom-up regional or even countrywide energy networks.

Final Phase – Connection to Centralized Grid Once the autonomous swarm micro-grid has grown in size and in demand, it can be connected to the main national grid. The last step of the swarm electrification process not only benefits rural electrified householders by connecting them to the main grid, preventing overloading risks, but it can also benefit national utility companies. Implementation of Phase 3 means connecting a medium to large number of users with a comparatively low investment.

Selling Excess Energy Swarm controllers facilitate the purchasing and selling of excess energy in a swarm microgrid. This allows productive use of the electricity by giving the users opportunity to gain income from selling their positive balance of energy. Participants in a swarm grid can buy electricity as they need it through the swarm controller. The opportunity to make direct income from selling excess electricity encourages efficient energy use because as a user’s consumption decreases the more excess energy them have to sell. The latter element expands the pay-as-you-go (PAYG) model by a cash-in-as-you-go (CAYG) element.

Subsystem of Swarm Microgrid Swarm electrification of a system is based on the existing SHS in the field presently which includes PV panel, a charge controller, battery and the connected loads. A swarm controller would be retrofitted to the existing SHS which would then link the participate to the swarm grid. The swarm controller allows for bidirectional power flow for the DC system by regulating two DC/DC converters through the measuring of voltages and currents on either side of the controller. This allows for the supply or drain of power from the grid as illustrated in figure 2.

Figure 2. Example of households being interconnected to create a swarm microgrid The meshed grid topology generally does not need to be planned as every participant can have as many as three interconnections to other participants. This characteristic enforces the concept of "bottom-up"  electrification. Power flow regulation is implemented using Droop-control, SoC-based Droop Control or other control algorithms. Limitations The swarm electrification model has limitations compared to a standard microgrid design when reviewing the ability to power larger electrical loads. Typically, microgrids during pre-design are calculated and sized to increase power use beyond SHS capacity. Microgrids are designed for increase energy demand over time and in addition, handle larger instantaneous power draw for large applications such as milling. A swarm electrified system is dependent on the existing SHS cabling and voltage thresholds, thereby limiting the instantaneous power draw to the SHS parameters. The dependence on existing connections for a swarm electrified grid would limit that overall energy availability and system performance overall. References