Swarm Electrification - A Paradigm Change: Building a Micro-Grid from the Bottom-up
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Why Swarm Electrification?
Imagine a Beach party in central Africa far away from the big cities: flashing lights, loud music, laughter. The scene we saw was made possible by a mini grid - a single photovoltaic module feeding one battery had not made it possible.
In Germany there is a 100% electrical grid connection which amounts to 0.8 billion people - but according to the United Nations Foundation worldwide 1.3 billion people lack that access. In India the percentage of people who lack access to electricity amounted to 34% in 2009.[1] Another billion of those who are electrified are only provided poor quality: electricity comes only limited time of the day and short cuts are experienced regularly.
For the research team of “Microenergy-Systems” at the Technical University (TU) of Berlin this seems like a huge market for innovative approaches. Especially because the experts from the International Energy Agency (IEA) expect in their “Energy for All Case” that 70% of the non-electrified rural areas cannot be reached with centralized grids but with mini-grids or stand-alone off-grid solutions.
Energy access in developing countries can be classified in three categories:
- In urban regions people could be classified as temporarily on-grid. So even if energy prices in for example India are much lower than in Germany this still means no advantage when this electricity comes with much poorer quality.
- In suburban areas poor people can live insight of electrical land lines but without having there own connection. The needed transformer station is what provides a lot of costs – an official program would be needed to subsidize the electrification. From a new perspective people living here could be called close-to-grid. For these Solar Home Systems (SHS) would seem like the second best solution.
- But the topic here is yet another. It is about rural population being classified as off-grid. To change these peoples life to the better a new perspective can be helpful. Calling them people far-from-grid.
But waiting for political policies to change facing the task of connecting far rural areas doesn’t seem to be satisfying. By installing SHS, diesel generators and other electricity producing systems and connecting them to form mini grids rural population could experience a proactive way.
What is Swarm Electrification?
The approach sees households and small businesses in rural undeveloped areas as the basis for the development of a micro empowerment from the buttom-up. The implementation of this new technological approach is end-user financed by providing micro loans according to the example of the Grameen Bank.
A premise to install a swarm grid is an off-grid village with some installed generators. Usually that would be Solar Home Systems which operate according to the presented slides with
- 20 to 85 Wp photovoltaic panels
- Lead acid batteries
- Efficient 12 V direct current (DC) loads (e.g. LED lights)
These systems generally have a payback period of one to three years and can guarantee three days of electricity autonomy in case of cloudy conditions.
The idea of the Swarm Electrification Team consisting of Daniel Philipp, Hannes Kirchhoff, Brian Edlefsen and Joseph Theune is to build up a grid in three phases:
- Phase 1: Households with SHS get connected to each other to be able to use each others battery capacities
- Phase 2: Connecting neighbour swarm grids to a regional grid
- Phase 3: Getting connected to the national grid
Why would the big utilities go that last step?
Utilities are driven by politicians that are interested in high electrification rates which they could easily augment with one step. The main reason for short cuts is overload which could be minimized by a bigger grid. Utilities could cut off that part of the grid if they realize that the frequency in the grid is unstable. Additionally the investment for the utility is comparatively low because the power meters are already there and with one step they could connect thousands.
What problems remain to be solved?
Four main questions were tackled: AC or DC, mesh or bus, role of Information and Communication Technology (ICT) and the
Group 1: AC or DC? About safety, appliances and flexibility.
Supervised by Daniel
In the industrialized world it is standard to use alternating current (AC) to transport electricity but many appliances work on direct current (DC):
- lamps,
- cell phones,
- laptops,
- and many others.
In the historical Europe, Edison and Tesla were fighting about what technology to use for electricity transportation. At that time technology for transformation of voltage levels was not as developed as today and so Tesla and his AC technology won the contest. Nowadays, switches for DC voltages are possible and there are even applications in which only DC transmission is possible. The AC transformators work with induction: as the current flow constantly changes direction it induces a magnetical field in the transformers magnetic core which in its turn induces an alternating current flow in the windings of the attached transmission line. That is why todays transmission cables through the oceans cannot work with alternating current but use high-voltage direct current (HVDC) cables instead.
The problem with direct current was the drop which the voltage suffered a drop at low voltage levels. But these losses are not important in a swarm grid because the distances between the houses are very short. Another problem was the possibility of transforming voltage levels. On the one hand, areas in which swarm grids should be installed would not need voltage transformations today: from the solar charge controller on the whole system normally works on 12 volts. On the other hand, AC devices as washing machines (which are not installed today in areas of interest) could be designed using a motor working with DC. Another argument against using DC cables is the safety of the system. In AC systems the current builds up in a sine curve and falls down again. Like that in theory if you touch an open AC wiring you will only be exposed to the maximum power ffor a short time and have a chance to get away from the wiring before being seriously harmed. In DC wiring this looks different: both voltage and current are constant. So if you touch an open DC wiring with a comparable power output than the typical western transmission grid you could die from the electrical shock hitting your body. In rural areas with solar home systems designed to light a light bulb and charging your mobile phone, the power in the grid is so low that you cannot die from touching an open wiring even if both current and voltage are stable.
In short:
- Generation in off-grid areas normally is DC as are most important devices.
- The evolution of a grid in those areas makes it possible to design a DC grid right from the start.
- DC transmission is more efficient than AC.
- At voltage levels of up to 24 volts there is no safety problem if someone should touch an open wiring.
Group 2: Mesh or bus? How topology matters.
Supervised by Hannes
Electrical grids can be designed differently according to how stable the grid should be and depending on the money that can be spent for setting the system up.
The two basic types are the mesh design and the bus design. The first one offers the best quality of electricity supply but comes with high costs. Mesh grids look somewhat like a spider net with the house units sitting at the knots between the straight lines and the net circles. Comparatively a lot of cables are needed for this design but if one of the cables get distroyed no house will be diconnected from the grid.
The bus type is the most economical variant but is not resistant to power failures. The houses are interlinked like pearls on an open necklace - one to another. It is obvious how the last houses will be cut off from the grid in case of a cable failure.
In the case of rural areas the aim is to connect the houses of a village with DC cables. But ingenieers have to find the best solutions to make the grid both financable and to provide with a stable network. Additional factors as pointed out above have to be regarded: if there are different voltage levels in the village, AC generation (e.g. diesel generator) or AC consumption (e.g. refrigerator) expansive inverters are needed. Both the number of inverters as the length of the cabling has to be efficiently calculated. The monitoring of the grid has to be made possible and simplified by reducing the number of meters and connections as much as viable.
In Short:
- The grid has to be designed by optimizing stableness and prize.
- Factors rising the costs are: inverters, meters and length of cables.
- The group could not decide on an optimal design and created a nice peace of art instead (see figure).
Group3: Smart swarms? The role of ICTs.
Supervised by Brian According to the Worldbank two thirds of the worlds population has access to communication technology, such as cell phones. Information and communication technology; making money, mobile phone tower – anchor partner 3.5kW (Ancor Business Community concept), leap frog, quantum leap land lines do not exist but mobile towers Presentation: risks and chances (get funding, anchor cell phone tower, base consumption load to connect with small businesses, stabilize by smart metering, provider to manage production, decentralized) with icts; need to collect data who needs to py who, what extend do we need and want; new busness ideas: solar phones; manage by ReMMP
Group 4: Link the interlinked? How to grow the swarm.
Supervised by Joseph
going from step 2 to 3
3 scenarios: Link individual SHS to each other, connect a swarm grid with another swarm grid, from swarm to centralized main
Advantages of interconnection: - Stability (less power cuts) - Lower operation and maintenance (O&M) costs per household - More electrified people - More storage capacity - Higher peak loads possible Differences in the costs: - Connection technology has to be paid - Less O&M costs - Maybe less batteries or less generation is needed in the whole system - Agreement on technical standards would mean to be working with economies of scale
