Poprawa efektywności energetycznej przy integrowaniu mikrosieci z inteligentnymi sieciami krajowymi

Abstract

Technological development of distribution and transmission grids and building a so called smart grid also enable improving the efficiency of microgrids and microgenerators. Better coordination and scheduling of microgenerators operation make more effective adjustment to local conditions and achieving better overall energy efficiency possible. Due to smart communication interfaces the microgrids and microgenerators can also contribute to ancillary services. DOI: 10.12736/issn.2300-3022.2014405 1. Possible improvements of energy efficiency Small distributed sources are often equated with renewable energy sources and environmentally friendly electricity generation. However, only some of them, based on hydro, solar or wind energy, do not pollute the environment. Other types of small sources generate electricity by burning fossil fuels (coal or gas), and sometimes also agricultural or municipal waste. Combustion always produces CO2, NOx, sulfur compounds, and other pollution. Combustion in small sources is less controlled due to reduction of control systems costs (with respect to the generator cost and the electricity output). In addition, micro-plants are not equipped with exhaust aftertreatment systems. Electricity generation in combustion-based distributed sources produces much more pollution per output MWh than large power plants. Maintaining a certain level of power generation’s environmental impact nation-wide, with increased pollution emissions in some sources, will require reduction of the emissions in other sources. Costs and energy saved in one place will be spent in another place. Current energy policy basically promotes environmentally friendly sources, although in the case of micro-sources to obtain such preferences is almost impossible. It is expected that in the coming years the market will be flooded with inexpensive generation systems suitable to power certain loads (e.g. heating, lighting, or water pumping). An inexpensive generation system is usually devoid of control capabilities, and a significant portion of primary energy (e.g. wind, solar) is lost. But it was not relevant to users, because the primary energy is free, and inexpensive systems were quickly amortized. Microgrids can operate independently, powering specific appliances at households and farms, as well as in high-rise buildings in cities. Due to the national grid’s widespread accessibility it will become an alternative source of energy. The national grid will be used when the supply from a microsource is temporarily unavailable. With the significant increase in the number of microsources, their connecting to and disconnecting from the power system will impact the national power grids’ loads, even if they do not convert electricity, e.g. when heating with the sun or pumping water at a farm with a windmill. Providing individual customers with a control signal, for example the current energy price, will affect their decisions to draw electricity from the national grid. Microsources’ adjustment to electricity input to the grid, and adoption of simple and clear rules for energy purchase will be the microgrids’ natural further development. The next step will be to improve the efficiency of the whole process, starting from better use of primary energy up to optimum distribution of generated energy. Coordination of microsources’ operation in a microgrid, already at the stage of the primary energy’s conversion, allows better use of energy carriers with a lower exergy. Interoperation of several sources improves the microgrid’s overall efficiency. Also significant are energy losses in microgrids’ interconnections with the national grid. In Tab. 1. Primary energy conversion in microsources G. Blajszczak | Acta Energetica 4/21 (2014) | 56–61