| Abstract | Small distributed combined heat and power (CHP) plants constitute a not insignificant share of the power production in Denmark, particularly the western part of the country. Since January 1st, 2005 these plants have been required to act on market terms, i.e. sell the power produced on the spot market, rather than at the fixed feed-in tariff previously used.
Many versions of the unit commitment problem have been discussed in the literature, from the so-called
economic dispatch (the task of dispatching the entire system at least cost given a certain demand) to optimal bidding to an electricity spot market in various shades. However, CHP is rarely touched upon and then mainly from the system point of view. This paper considers a local CHP plant faced with bidding into the spot market while taking into account assorted physical limitations.
As prices thus are unknown at the time of production planning, a simple stochastic model is utilised to construct an optimal plan under uncertainty. In the model, the CHP unit is segmented and with it all the parameters (cost, electricity to heat ratio, etc.) connected to it. This enables taking into account varying efficiency and production costs as well as enabling the handling of pollutant emissions, the extent of which depend in various ways on the level at which production takes place.
A case study is conducted using data from a typical local CHP plant and the years 2003 through 2006 are simulated to assess the accuracy of the stochastic model compared to the deterministic case. |