Innovative Direct-Current Microgrids to Solve India’s Power Woes – IEEE Spectrum article tells that a group at the Indian Institute of Technology (IIT) Madras in conjunction with industrial partners, relies on solar-powered direct-current (DC) microgrids. For homes not connected to the grid, a 125-watt microgrid can serve as the sole source of electricity. For connected households, the microgrid acts as a backup power supply to let lighting, fans, TV sets, and cellphone chargers continue operating even during brownouts (about 10 percent of the typical household load).
This microgrid relies on DC because PV panels and batteries as well as consumer electronics, LED lighting, and a growing range of appliances all work with direct current. In that way it is possible to avoid the losses that come with converting back and forth between AC and DC. This micrgrid system is entirely DC system that uses a 48-volt DC line.
The selection of 48V DC is somewhat on sweet spot of being high enough not to cause very high lossses on short distances, is still relatively safe and this voltage level is already quite widely used in many applications (telecom infrastructure, data centers, power over Ethernet, vehicles, industrial applications, phantom power in audio systems).
This 48V DC system is not the only DC microgrid system that is being researched. Schneider Electric has higher power DC micro grid uses array of solar panel connected in series to generate power at 230 V DC. This 230 V DC can be transmitted over distance of 1-2km similar to 230V, AC distribution line using a 2 core cable and supporting poles.The micro grid charge controller installed in each house steps down 230V, DC to 14V, DC which is used to charge the storage battery and power the energy efficient DC loads in house.
For some other DC distribution ideas being considered on other countries, read DC distribution and power electronics applications in Smart Grids document.
4 Comments
Tomi Engdahl says:
Tying a microgrid to the smart grid
http://www.csemag.com/single-article/tying-a-microgrid-to-the-smart-grid/dd9d6996ff69696ba2e634821ebc25ad.html?OCVALIDATE&[email protected]&ocid=101781
Building owners frequently integrate the utility’s smart grid into their buildings to reduce electricity use and increase energy efficiency. Microgrids can further lower costs and raise reliability for owners and the surrounding communities.
The need to transform the nation’s aging electrical grid to enhance reliability and sustainability is increasingly imperative as the existing grid becomes outdated and unable to support or withstand current needs and risks. The fundamental concepts behind microgrids do not vary much from typical campus-scale power-production models that proliferated throughout the mid-20th century, which include paralleled local and utility generation with the ability for local generation to sustain a portion of a campus. However, the drivers for their application and the smart technologies available to support them continue to evolve.
Smart grid and microgrid defined
The terms “smart grid” and “microgrid” often become interchanged, inviting a variety of different understandings. Defining these systems by scale and function will help navigate their interrelation and set a basis for how to apply them.
A smart grid is an intelligent and integrated system of interregionally connected electric utilities, consumers, and distributed-energy resources (DERs). This evolving form of electrical transmission uses advanced metering, monitoring, management, automation, and communication technologies to provide reliable two-way delivery and consumption of electric power. Real-time flow of essential information among grid components assures effective, efficient operation for generators, distribution system operators, and end users. A smart grid optimizes two-way traffic on the grid.
A “microgrid” is a localized electrical network that allows campuses and other similar-sized districts to generate and store power from various DERs including renewable electrical generation sources, such as wind and solar, providing the ability for end users to function in isolation from the grid. Balancing supply-and-demand resources-including thermal and electrical loads-within its defined boundaries, a microgrid system provides resiliency
Campuses, municipalities, and other similarly sized regional areas choose to develop a microgrid for a variety of reasons, including resiliency, economics, flexibility, sustainability, and reputation. At the beginning of each project, it is important to discuss and determine the drivers that influence implementing a microgrid in a specific region.
Tomi Engdahl says:
Tying a microgrid to the smart grid
http://www.csemag.com/single-article/tying-a-microgrid-to-the-smart-grid/dd9d6996ff69696ba2e634821ebc25ad.html
Building owners frequently integrate the utility’s smart grid into their buildings to reduce electricity use and increase energy efficiency. Microgrids can further lower costs and raise reliability for owners and the surrounding communities.
Smart grid and microgrid defined
The terms “smart grid” and “microgrid” often become interchanged, inviting a variety of different understandings. Defining these systems by scale and function will help navigate their interrelation and set a basis for how to apply them.
A smart grid is an intelligent and integrated system of interregionally connected electric utilities, consumers, and distributed-energy resources (DERs). This evolving form of electrical transmission uses advanced metering, monitoring, management, automation, and communication technologies to provide reliable two-way delivery and consumption of electric power. Real-time flow of essential information among grid components assures effective, efficient operation for generators, distribution system operators, and end users. A smart grid optimizes two-way traffic on the grid.
A “microgrid” is a localized electrical network that allows campuses and other similar-sized districts to generate and store power from various DERs including renewable electrical generation sources, such as wind and solar, providing the ability for end users to function in isolation from the grid. Balancing supply-and-demand resources-including thermal and electrical loads-within its defined boundaries, a microgrid system provides resiliency
A microgrid can operate as an “island” or independently from the larger utility grid as required
Experience with microgrid projects has shown the areas essential to successful analysis, planning, and implementation to include:
Identifying needs and drivers
Developing functional requirements
Developing system topology and operation
Considering technical, regulatory, and financial outlooks
Proper commissioning, start-up, and operation.
Many cities and regions see microgrids as a possibility to create economic growth or better maintain financial stability.
Advances in renewable energy integration allow broader deployment of renewable energy sources and storage technologies as part of a microgrid strategy.
As the development of a microgrid concept advances, it is critical to identify various possible operational modes of the given system.
Potential modes or configurations of microgrid operation include:
Grid mode-local generation is connected to the utility grid and operates in parallel
Intentional island mode-local generation is deliberately disconnected from the utility grid and can operate independently. Generation is typically sized to support the total load of the microgrid.
Emergency island mode-local generation is disconnected from the utility grid following a grid outage and can operate independently. Generation may or may not be sized to support the total load of the microgrid. Load shed may be required.
Load-shed mode-turning off load/demand response to prevent failure of a system when demand exceeds available generation
Power-purchase-only mode-all loads are being supplied completely by power purchased from the utility. No local generation is operating.
Power purchase and self-generation mode-loads are being supplied by a mix of power purchased from the utility and local generation
Power-export mode-loads are being supplied completely by local generation, and there is excess power from local generation being sent back to the utility grid
Micro-renewable generation-microgrid installations comprised of less than 50-kW electrical or less than 45-kW thermal resources
Multiple versus single utility feed-system is considered single or redundant utility feeds for resiliency
Varying self-generation dispatch-local generation is turned on or off, or power output is adjusted based on a number of factors that may include load matching, optimized source selection, economics, or redundancy
Storage dispatch-local energy-storage devices are placed in energy-collection, generation, or idle mode based on whether there is an excess or shortage of local or utility generation.
Distributed generation (DG) that uses a microgrid allows any combination of local fuel-based or renewable energy sources, such as natural gas generators, microturbines, fuel cells, solar photovoltaic (PV), distributed wind, and combined heat and power (CHP) cogeneration systems, to serve the loads of a facility, campus, city, or another defined district.
Smart buildings can improve the operation of a microgrid by which they are served. As load centers in a given locality, buildings that are technologically enabled to monitor their own energy consumption can be further enabled to reschedule certain power usage to off-peak hours, improving the overall efficiency of a microgrid.
Tying a microgrid to the smart grid
Advanced power electronics and communication technologies increasingly enable large numbers of DG sources to link to the grid through highly controllable power processors, allowing efficient and reliable distributed power delivery during regular grid operation and powering specific islands in case of faults and contingencies
The IEEE 1547.4-2011 utility interconnection standards were specifically updated to accommodate microgrids and their unique frequency stability issues along with synchronization requirements.
Tomi Engdahl says:
That Decentralised Low Voltage Local DC Power Grid, How Did It Do?
https://hackaday.com/2017/09/08/that-decentralised-low-voltage-local-dc-power-grid-how-did-it-do/
Early on in the year, Hackaday published one of its short daily pieces about plans from the people behind altpwr.net for a low voltage DC power grid slated for the summer’s SHACamp 2017 hacker camp in the Netherlands. At the time when it was being written in the chill of a Northern Hemisphere January the event seemed so far away, but as the summer fades away along with the deep tan many SHACamp attendees gained in the Dutch sunlight it’s worth going back and revisiting the project. Did they manage it, and how did they do? This isn’t really part of our coverage of SHACamp itself, merely an incidental story that happens to have the hacker camp as its theatre.
A Bold Experiment In A Decentralised Low Voltage Local DC Power Grid
https://hackaday.com/2017/01/18/a-bold-experiment-in-a-decentralised-low-voltage-local-dc-power-grid/
Tomi Engdahl says:
Modular Power Blocks Snap Together to Scale Up Energy Needs in Remote Areas
https://spectrum.ieee.org/energywise/energy/renewables/modular-power-blocks-snap-together-to-scale-up-energy-needs-in-remote-areas
More than 1 billion people in the world live without electricity. The challenge of bringing it to them is somewhat analogous to the desire decades ago to install fixed telephone lines in impoverished communities. The need was there, but the money wasn’t.
Enter Power-Blox. This distributed energy system is made of 1.2-kilowatt battery cubes that store solar or wind energy. They snap together LEGO-like to save and provide more power. Software that uses a swarm intelligence-based algorithm balances energy fluctuations between connected units, even if one of them malfunctions or is unplugged. One unit can serve the needs of a few people, while several units can work together to create a modular microgrid, powering an entire village.
The microgrid consists of five PowerHubs—secured metal sheds about 1-meter square and 2 meters tall—each topped with a solar panel. Inside, the space can accommodate up to eight Power-Blox units, which can be installed without any special technical knowledge.
“Once you have power there, businesses start and demand gets bigger,” said Medici.