The 4th edition of the Wind Energy Workshops “National Power System balancing in the context of increased system share of variable sources” was held on 15 October in Warsaw.
The first paper, “RES balancing in the Polish and European law”, was presented by attorney-in-law Karol Lasocki. Among others, the paper discussed balancing reasons as premises for connection refusals as well as commercial balancing and RES energy purchase obligation in terms of European regulations. Furthermore, conclusions stemming from the European Commission’s Guidelines on State Aid for Environmental Protection and Energy 2014 – 2020 and the Commission Regulation (EU) No 651/2014 of 17 June 2014 declaring certain categories of aid compatible with the internal market as well as the Directive of the European Parliament and of the Council 2009/72/EC concerning common rules for the internal market in electricity were also presented.
After that the floor was taken by Professor Józef Paska from Department of Power Plants and Power Management, Warsaw University of Technology, who presented a paper on reliability of RES operation in the National Power System. Professor Paska, discussuing energy security, stressed that the problem of consumer electricity supply quality may be dividied into three issues: quality of supplied electricity (voltage quality), reliability of electricity supply (reliability of supply) and consumer (customer) service quality. It is assumed that the power system comprises three functional zones: production, transmission and distribution. The structure continues to properly reflect the essence of power system operation; however, two new aspects shall be considered today: (i) the often-encountered division of production and distribution among a certain number of independent companies, and (ii) the increased use of renewable energy sources (RES) and small-scale sources in the distribution system, which create distributed generation. Reliability of wind farms shall be considered in the context of two categories, as structural and technological reliability stemming from the design, construction and configuration of devices comprising a wind farm and its grid connection, and as production reliability stemming from random variability of production capacity (resulting from wind speed or solar radiation intensity).
Another subject, pertaining to wind farm electricity production forecasting, was presented by M. Sc. Zenon Grzenda from Warsaw University of Technology, who discussed the main factors affecting commercial balancing of a wind farm: wind speed, wind direction, air density and land roughness. He stressed the changes in electricity sales settlement as seen by electricity producers and trading companies.
Next the floor was taken by Leszek Strojek – Director of System Balancing Department in Polskie Sieci Elektroenergetyczne, whose daily tasks include daily and mid-term (up to 3 years’ perspective) balancing of the National Power System. His paper, pertaining to technical balancing of variable sources in the National Power System, discussed issues related to mid-term and daily planning, and specified wind energy development threshold from the transmission system operator’s perspective. For the presented day with 5 000 MW of planned wind generation the required range between minimum and maximum capacity amounts to approximately 11 200 MW. In accordance with PSE such capacity may be ensured only by combined reduction of power output of operating thermal units (maximum effect: approximately 6000 MW) and the use of pumped-storage power plants (maximum effect: approximately 3000 MW) as well as additional measures (required effect: approximately 2200 MW). Potential additional measures include optional night shutdown of thermal units wiht previously decreased power output (up to 20 units) or periodical curtailment of wind farm power output (maximum by 2200 MW).
In his paper Jacek Grzyb from TAURON Polska Energia S.A. discussed in detail the commercial balancing scheme, the definitions of a Balancing Market Area as well as a Balancing Market Unit, and possible Balancing Market participation methods. In the second part of the presentation he discussed a tool supporting trade, notification and settlements.
The Workshops presented the entire commercial balancing procedure during a single trading day, materials describing the WIRE system, and template documents generated by the transmission system operator.
During the discussion Professor Paska stated that from the power system reliability point of view the appearance of new RES generating units close to consumers is good. The additional sources may provide supply during power shortages or local power grid failures. However, from the reliability point of view, the flaws of the technology include the use of usually unstable primary energy sources, where power output is highly random. Participants of the debate also stressed that our regulations preclude the pricing and provision of system services by wind farms. From the investors’ and the National Power System point of view the issue shall be addressed. A representative of PSE stated that currently renewable and distributed generation balancing and modelling in the National Power System is more complicated than in the case of classic generating units. Currently, detailed National Power System analyses require processing vast amounts of data. This requires increased efforts of the transmission grid operator to balance the current energy demand with its supply in the National Power System while ensuring the quality and reliability of electricity supply.
Other voices during the discussion expressed doubts concerning the operation of the balancing market and the legitimacy of establishment of balancing groups, and raised questions if competition on the market is possible at all given its current design.