DC Village: Sustainable Energy-Efficient Community of the Future
Thomas Edison’s first electric power system was direct current (DC). Although his DC network had advantages in simplicity, safety, modularity, and direct connectivity to storage batteries, Edison found that increasing the power capability of the DC system was not without limitations. His major difficulty was in boosting up the voltage level to reduce current and power losses. To solve for this, the electric power had to be generated in close proximity to the consumers, forming the basis of a concept that is now known as distributed generation.
A few years later, and more than 100 years ago, Nikola Tesla invented the more complicated alternating current (AC) electrical system and advocated the AC power network of generation, transmission, distribution, and utilization. With the financial support of George Westinghouse, Tesla promoted his AC system as superior to Edison’s DC network. Tesla’s AC system had two critical advantages. First, unlike in DC, transformers could be used in AC to step up or down the voltage. This made it possible to increase the voltage of the generated electricity and transmit the electric power at a higher voltage—allowing for a lower current and less power loss—to the distribution sites and consumers. Therefore, Tesla’s system was more efficient and did not have the power limitations that suffered Edison’s DC system. Second, Tesla had also proved the theory of rotating magnetic field, which resulted in practical AC motors and generators to operate at higher power. Such AC machines were more efficient, needed much less maintenance, and were less expensive. Over time Tesla’s AC system prevailed, and the electric power grid today is three-phase 60/50 Hz AC.
All of this predated power electronics—the technology for conversion and processing of electric power. Power electronic circuits can convert one form of electricity to the other. They can also step up or step down the voltage and current of the system. Power electronic converters include AC/DC rectifiers, DC/AC inverters, AC/AC cycloconverters, and DC/DC choppers. Power electronics provides the basis for a variety of revolutionary electrical power system configurations that allow substantial improvements in efficiency, performance, and flexibility.
Power electronics has emerged as an enabling technology for Edison’s DC system. DC/DC converters are, in fact, advanced electronic transformers, which are more compact and efficient than conventional AC transformers. Advanced electric motor drives, with or without Tesla’s rotating magnetic field, also need a DC supply with power electronic drivers. Therefore, a power electronics-enabled DC system has all the advantages of Edison’s DC without what were its disadvantages more than a century ago. In addition, most renewable energy sources, such as solar cells, produce DC output and therefore need DC to AC interface links to be connected to the grid.
Because of the advantages of DC, advanced high-tech stand-alone electrical systems, such as the International Space Station and electric and hybrid-electric vehicles, are power electronics-intensive DC-based systems with the capability of providing power in both DC and AC forms.
The DC Village project is aimed at developing a model for a sustainable energy-efficient community using innovative solutions enabled by the emerging state-of-the-art power electronics-intensive DC electrical system. Our goal is to develop the next generation of the electrical system by leapfrogging the AC-based system and presenting a more advanced system as a sustainable solution for villages and communities in Africa, Asia, and other developing countries, as well as in remote and rural areas in North America, Northern Europe, and Australia.
This project is designed for implementation in villages and communities where people do not have access to electricity. Renewable energy sources—such as solar, wind, hydro, and geothermal recharging stations—will charge batteries that people can purchase or rent, in much the same way that people purchase propane or natural-gas cylinders for cooking needs. These batteries will store electrical energy in DC form, provide the electrical needs, and power their entire home. When the battery is out of energy, individuals can simply obtain a fully charged replacement battery for a fee. Alternately, renewable energy sources could be connected to homes through a smart grid, which would power the home and allow for onsite charging of the batteries. The batteries are still needed to store energy because of the inherent intermittency of the most promising high-tech renewable energy sources—photovoltaic, solar-thermal, and wind power.
Transportation in DC Village will be entirely electric or human powered and sustainable. Lightweight vehicles such as solar/battery-powered, smart, electric vehicles and bicycles will be used to transport people and goods. Both battery swapping and direct plug-in charging will be utilized.