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Distributed Generation 

Power path: from the power stations through your home​





Large-scale electric power production (P) takes place in power stations: hydroelectric (water source); thermoelectric (coal, oil, natural gas, nuclear, biomass and geothermal); wind farms; solar plants (photovoltaic and solar thermal). In order to transport the power through long distances and reduce losses, the power goes through a transformer (T) where its tension is modified (risen). From there on, electric power goes to the cities or places of consumption, through transmission limes (LT). Voltage of those systems may range from 13.800 V through 750.000 V (13.8-750 kV). When it arrives in the cities, the electricity goes through a transformer that reduces the voltage from transmission level to distribution level, when distribution networks are used (RD) (13.8 kV and 34.5 kV). When it arrives at the consumption locations (C), voltage needs to be adjusted to the equipment’s level of consumption that in Brazil ranges from 127 through 380 V. Then, electricity goes through, again, a transformer, which adjusts the voltage and provides the consumer with the power. Currently, small-sized technologies are available, which allow the consumer to produce his/her own power. These are the motor generators, solar panels, among others. Since 2012, the law [REN482/2012 y REN 687/2015, from Agência Nacional de Energia Elétrica (ANEEL)] allows this kind of connection, known as micro and mini distributed generation (DG).

Distributed Generation: Concept

Distributed generation features by the spatial and geographic dispersion, compared to large power stations and it is preferably located close, or even, in, the place of consumption. Typically, such features lead this kind of generation, to the small size, exploring sources like wind and solar power, i.e., those that form the panel of renewable energy. DG also aggregates in terms of power efficiency in that it reduces losses in the power system and leads the way and possibilities to Smart Networks.

The future: SMART GRID and SMART CITY

Distributed generation path transforms the relationship between society and electric power in that consumer can turn themselves into power producers and active change agents and power system evolutions, as well  PROSUMERS. Distributed generation calls for more complex systems for its control. Massive instrumentation of the power network, along with the need of Technologies of Information and Communication (TIC) for its automation, bidirectional flow of power and communication (either system – consumer or consumer system) and a diversity of technologies (generation, storage systems, electrical vehicles) lead to Smart Networks or Smart Grids. These systems are those that supply the society of the future with power. Increasingly, one observes that all these issues are interrelated: residues, power, mobility, services, new services Internet of Things - IoT. This is the convergence of issues everyone will have to think about and decide the actions to be taken. It is the return to basics about the relationship among humanity, environment and power. The society of the future will have to elaborate an integrated planning among its cities Smart Cities, where the issues we currently see as problem, would be solved.  A Smart City demands a Smart Grid.

DG benefits:

Typically, the presence of small generators, close to loads, may result in several benefits to the power system and concessionaires, among which, we list: 

• Postponement of investments in the expansion of distribution and transmission systems; 
• Low environmental impact; improvement in the network voltage level, over the heavy load period;
• Increase of source power efficiency, thanks to the reduction in production losses and electricity transmission;
• Diversification of the power matrix 
• Encouragement to create new business models, applicable to the power sector.

On the other hand, there are several improvement opportunities, associated to the number of small generators spread across the distribution network, such as, for instance: the network’s operation complexity and stability; difficulty to charge the use of the power system; eventual incidence of taxes, and need to change distributor’s procedures to operate, control and protect their networks.

Technologies applicable to distributed generation:

The characteristic of the spatial spread of electricity production leads to small-sized and of renewable nature technologies. Typically, technologies applicable to this segment can be understood according to the list here below:

• Motor generator (diesel, oil, ethanol, natural gas, and biogas);
• Micro-turbines;
• Small-sized aero-generators (horizontal and vertical);
• Small and micro hydroelectric plants;
• Combustible cells;
• Photovoltaic solar panels.

Due to a series of reasons (location availability, investment cost, benefits, regulation and laws, among others), at this point, solar power-associated technologies (photovoltaic panels) represent a significant vector of distributed generation deployment increase.

About power compensation:

Since April 17th, 2012, when ANEEL created the Electric Power Compensation System, Brazilian consumers are authorized to generate their own electric power (at their own risk) from renewable sources or qualified cogeneration and even, provide the distribution network of his/her community with the exceeding power, by means of a compensation system. CEMIG, aligned to technology development, has connected the first unit of electric power micro generation in Brazil, in September, 2012. Since then, it is the leader in the distributed generation connection market, in the country. 

More details about the ruling and adhesion process to the power compensation system are available
here.


In March 2017 (03/08), CEMIG had 1831 DG units of connected consumers, totalizing an installed capacity of 19.3 MW. It represents about 0.2% of the installed power. In Brazil, there are 8801 power stations, representing an installed capacity equivalent to 99 MW, in that the photovoltaic solar source is present in 8704 power stations (98,8% del total), what corresponds to 66 MW (67% of the total capacity). The other available technologies are the following:

Type

Quantity

Installed power (kW)

Hydrological

11

7.115,00

Wind

48

10.168,80

Photovoltaic

8.704

66.755,25

Thermoelectric

38

15.077,00

Total

8.801

99.116,05

These figures have varied quite dynamically and updated values can be accessed 


Research and Development Projects 

As defined by Act No. 9.991/2000, CEMIG invests in research and technological development projects (R&D). ANEEL rules this program. 
Taking into account that, typically, distributed generation-associated technologies are available, either when it comes to small size or renewable power plants, we would like you to see the Figure here below: a panel of projects associated to DG. One can observe the diversity of technology and possibilities.



 
Each number is associated to a R&D project. To know the summary description of each project, access the Project List and input the corresponding number 

The book: Uma Reflexão sobre Energia Renovável, in its chapter 2​ presents a summary of the projects related to power alternatives, associated to distributed generation. An interesting observation one can make is that it is still an open matter, filled of questions that should be answered and need to be defined, namely: commercial consolidation of technologies, cost reduction, need of regulatory, legal and tax changes, in order to widen the possibilities of this model to produce electricity.

To learn more about:

Chapter about DG (cap. 15, pg. 205) of the book: Alternativas Energéticas: Uma Visão Cemig
Handbook on DG – Appendix of the book: Uma Reflexão sobre Energia Renovável​
Access management of micro and mini-distributed generation
​​Distributed mini and micro-generation – Compensation System

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