Balancing an Increasing Share of Intermittent Wind Power Production : A comparison between the characteristics of wind power variations in Sweden and the technical flexibility of a major district heating utility

Abstract: Environmental changes caused by human activities are frequently discussed issues andrenewable energy is given increased technological and political attention. The Swedish politicaltarget of a growth of renewable energy has boosted investment in weather dependent wind powerproduction. As a larger share of the energy supply becomes intermittent, the energy system faceschallenges in balancing the grid and maintaining a secure energy supply. Thus, new requirementson regulating capacity will be necessary to drive this transformation. AB Fortum Värme samägtmed Stockholms Stad (Fortum Heat), a district heating company operating in the Stockholmregion, has the potential to adapt its electricity production to market variations. The flexibilityoriginates from a large variation of technologies and fuels used, and the company is both aconsumer and producer of electricity. However, the electrical flexibility is limited by rampingtimes and the heating demand of the market, and inaccurate forecasts complicate the planningprocess. In this report, the historical hourly variations of wind power production from 2011-2015 inSweden were investigated and compared with the technical flexibility of Fortum Heat. Thevariations were found to be in line with the current ramping times of the company’s power plantsbut would in some cases require the plants to be in stand by mode, posing higher economic risksfor the company. The seasonal variations in Fortum Heat’s flexibility were also found tocoincide with the changes of wind power production, with some exceptions. During extremelylow temperatures, Fortum Heat produces heat alone due to liabilities towards the district heatingcustomers. Consequently, as wind power production was lower during these temperatures,Fortum Heat has to decrease its dependency on heat only production in order to enable electricityproduction. Furthermore, wind power production was smaller during higher temperatures, whenFortum Heat’s flexibility is low. Condensing power could be operated during these temperatures,but require that maintenance would have to be planned accordingly.