by Vivek Bhandari
Power cuts are rare occurrences in some parts of the world and they are a daily occurrence in others. Throughout the world, people would like to avoid these power cuts and have reliable, secure and clean electricity. Micro-grids¹ are emerging as a simple and flexible technology that will help to improve power systems – increasing reliability in electricity distribution allowing the incorporation of renewable sources.
As the size of the human population increases so does the demand for electricity. While generation sources have increased along with this increasing demand, the capacity of supporting infrastructure like transmission lines, storage devices, and smart-meters has tended to lag behind. Although one might instantly think that technical advancement is the biggest impediment to improving power systems, there is actually very little deficiency in technical know-how. The main impediments to improving power infrastructure in developed countries are social and political in nature, including overcoming negative public sentiments such as a ‘Not in My BackYard‘ attitude, addressing the desire to transition to clean energy, and addressing concerns over radiation and privacy. In developing countries, additional challenges exist: many parts of these countries are yet to be electrified. So, initially, electrification is the primary challenge in developing countries and requires substantial investment.
Micro-grids may provide a solution to many of these challenges. The idea behind micro-grids is simple: micro-grids are essentially smaller footprints of a traditional power grid (i.e. a network composed of electricity generation, transmission and distribution infrastructure) that may work independently from it. Mostly because of their smaller size, modern control features and local ownership, micro-grids offer many advantages over traditional power grids. The flexible of working with or without a traditional large power grid makes micro-grids more adaptable and reliable. One option is a hybrid mode, where part of a micro-grid is powered by an external power-grid and part is powered by its own generators, which further improves reliability. Micro-grids can make power systems more secure by employing modern communication and control techniques.
Micro-grid technology is beginning to receive a lot of interest and investment and is being adopted throughout the world. Examples of functional micro-grids can be found in Fiji, Africa, Nepal, Denmark and the United States. Here, I present two examples of micro-grids: one in Nepal and one in the USA. While electricity generation and usage in these countries are drastically different – for example, an average person in the USA uses about 100 times more power than an average person in Nepal2 – micro-grids solve problems related to power in both places.
Baglung micro-grid, Nepal: Nepal is a small mountainous country with abundant hydropower potential (around 42 GW). But, due to costs associated with harnessing hydropower and unstable government, it has only been able to generate around 0.6 GW. In simple terms, this is not enough power to meet the population’s demands. So, on average, Nepalese cities that are powered by the national grid have a scheduled power outage of 12 to 18 hours per day.
The situation is a little bit different in the villages of Nepal. They have distributed energy sources like roof-top solar and micro-hydro power to fulfill their energy needs. Currently some of these generators generate surplus energy whereas the others generate insufficient energy to meet the villagers’ requirements. If such generators could be interconnected in a region to form a micro-grid, that region’s power needs may be better met. People in Baglung district have taken a step toward this. They have connected seven of their micro-hydro power plants together to form 107 kW, 11 kV micro-grid that supplies power to around 1,700 households and small industries. With this interconnection, surplus generation from one power plant can be used to meet the demand of the neighboring load. As a result, the power supply is more reliable and there are no outages. Additionally, this has led to cheaper electricity (because the locals were able to fix electricity prices by themselves), new entrepreneurial activities (due to surplus power), and improvements in health and education (due to reliable electricity).
Princeton micro-grid, USA: Unlike Nepal, the USA has no scheduled power outages, but natural disasters can sometimes cause outages (see figure below). For example, Hurricane Sandy caused a power outage in New York and surrounding areas. When New York was in darkness, Princeton University was not. Princeton usually gets power from the utility grid supplying that area and it also has two 26 kV micro-grids (that can be interconnected), supplied by a 15 kW gas turbine generator (in a “Combined Heat and Power” configuration). During Hurricane Sandy, power from the main utility grid was disrupted due to transmission line failure. To continue with their regular activities, they switched onto their micro-grid. What might have been a significant disruption was therefore averted.
Given the advantages of micro-grids, we might immediately think of implementing them everywhere. But there are still challenges for seeing abundant, fully functional micro-grids. These challenges are mostly social and political in nature, rather than technological. To overcome these challenges, micro-grids should be developed and implemented step by step. As a short-term goal, developed countries could opt for developing micro-grids in areas where reliable power is most crucial, such as in hospitals, army barracks and universities. At the same time, developing countries could connect existing isolated power generators, such as solar, micro-hydro, and bio-fuel generators to form micro-grids. Over the short term, the deployment of a limited number of micro-grids is likely to increase awareness of their potential benefits (reliability and security) and help to address negative public perceptions. In the longer-term, developing and developed countries may even choose to sidestep the traditional power-grid in favor of micro-grids. With increased investment by both governmental and non-governmental sectors in micro-grids, I personally foresee this technology to dominate the power industry in the coming decades.
¹ When these micro-grids are made to act “smart”, they are sometimes referred as smart-micro-grids. As most infrastructure in today’s electricity industry is inherently “smart”, I use the term micro-grid, instead of smart-micro-grid.
2 PNepal = generation/population = 22 W/person; Nepal generates around 0.6 GW and its population is 27 million. PUSA = generation/population = 3185 W/person; USA generates around 1,000 GW and its population is 313.9 million.
Vivek Bhandari is a 2012 fellow of the Fulbright Science and Technology Award program, from Nepal, and is a graduate student in Electrical Engineering at the University of Minnesota.