مزایای زیست محیطی از تولید پراکنده با و بدون انتشار تجارت

The need for improving energy efficiency and reducing CO2 emissions and other pollutants, as well as the restructuring of energy markets has favoured the increase of distributed energy resources (DER). The co-ordinated control of these sources comprising renewable energy sources (RES) and distributed generators (DG) characterised by higher efficiencies and lower emissions compared to central thermal generation, when based on coal or oil provide several environmental benefits. These benefits can be quantified based on DER participation in the CO2 emission trading market. This paper provides a method to calculate emissions savings achieved by the marginal operation of DER in liberalised market conditions using available emissions data. The participation of DER in emissions trading markets is also studied, with respect to profits, pollutants decrease and change in operating schedules. It is shown that the operation of DER can significantly reduce pollutants, provided sufficient remuneration from CO2 emission trading market participation is provided. Moreover, it is shown that using average emissions values to calculate the environmental benefits of DER might provide misleading results.

Development of environmental friendly (renewable energy sources (RES)) and highly efficient power generation (combined heat and power (CHP) production) has attracted significant attention around the world. This is due to the increased awareness of the detrimental effects of the emissions from hydrocarbon based power stations on the environment, which has led to the commitment of many countries to comply with the Kyoto protocol (Kyoto, 1997) and reduce their green house gas (GHG) emissions. In line with the Kyoto protocol, emission trading has become a reality in several EU countries (EEX, 2006). Moreover, recent studies have been presented in literature about clean development mechanism (CDM), related either to the sustainable development of developing countries (Winkler et al., 2002), or to the emissions reduction for developed countries like Japan (Kosugi, 2005) and Canada (Potvin, 2006). At the same time, the deregulated energy environment, among other effects, has favoured a gradual increase in distributed energy resources (DER) connected at the medium voltage (MV) or low voltage (LV) side of the distribution network (Lasseter, 2002). DER like micro turbines (MT) and fuel cells (FC), either in CHP mode or purely for electricity production, are installed in the distribution network, even within consumer dwellings (Bauen, 2004). RES, like photovoltaics (PV), small wind turbines (WT) and small hydro units, are also expected to increase their share in the coming years (EREC, 2006). Co-ordinated operation and control of DER is essential to obtain full benefits from their operation. The technical challenges of controlling a multitude of small units with perhaps conflicting interests are huge, and thus considerable research is devoted in the USA (Lasseter, 2002), EU (MICROGRIDS, 2002), (MORE MICROGRIDS, 2005), Japan(Tanaka,2004) and Australia(Jones, 2005) to develop centralised and decentralised control (Dimeas, 2005), (Hatziargyriou, 2005) approaches of DER-dominated MV and LV distribution networks. A microgrid, is defined as a DER-dominated LV network that operates mostly interconnected to the MV distribution network, but can be also operated in island mode, in case of faults in the upstream network (MICROGRIDS, 2002). The installation of DER close to loads reduces flows in transmission and distribution circuits and thus losses. Moreover, the increased efficiency of DER, especially CHP, and the operation of RES reduces emissions. Preliminary studies (Microgrids, 2005a) report that reduction of losses by 1% in the UK system reduces emissions by 2 million tonnes of CO2 per year. Moreover, in the UK, reduction by 1 GWh from hydrocarbon can reduce emissions up to 400 000 tonnes per year. In selected Portuguese networks of various types, ranging from rural LV networks to HV ones, 20% penetration of DER reduces CO2 emissions by 2.07–4.85% (Microgrids 2005b). A significant impact of increased efficiency in the domestic utilisation of gas and electricity on the reduction of CO2 emissions is claimed in (Pudjianto, 2006). It is demonstrated that on European scale, 65 million tones of CO2 per annum can be saved by 50 million installations of domestic CHP units. Next to the potential environmental benefits of DER, their economic evaluation is critically influenced by the developing CO2 emissions trading markets (Laurikaa, 2006), which also affect production costs of electricity generated by thermal (hydrocarbon) units (Microgrids 2005a). This paper investigates the environmental benefits of the co-ordinated operation of DER under two different optimisation objectives, namely minimising operating costs and minimising emissions, when DER are marginally deployed. Moreover, the potential benefits from the participation of DER in the CO2 emission trading markets are calculated. Emissions estimations from average emissions of the upstream network and from analysis based on marginal units data are compared. The structure of the paper is as follows: The method adopted for the estimation of the environmental impact from the co-ordinated operation of DG sources is presented in Section 2. In Section 3, data for a typical LV microgrid interconnected at an actual MV network, used as a case study, are provided. Section 4 presents the change in pollutants, CO2, SO2, NOX and particulate matter (PM-10), under two optimisation objectives and the potential benefits obtained by DER participation in the emissions trading markets. Conclusions are drawn in Section 5.

In this paper, the capabilities of co-ordinated operation of DER to reduce the pollutant emissions of a power network are investigated. Optimal economic operation and optimalenvironmental operation are studied together with the effect of participation in CO 2 emissions trading, both with respect to emissions reduction and increase of earnings. Application of the developed method, depends on the available informa- tion regarding emissions of the operating units. For marginal DER deployment, more accurate results are obtained when the emissions and operating intervals of the marginal units are available. On the other hand, average annual or monthly emissions from the central units, may lead in misleading conclusions about the DER environmental impact. Although the goal of DER operation may be minimisa- tion of CO 2 , the error in the estimation of pollutants may not lead to achieving it, due to the fact that the average emission level leads to operation of DER during hours that are not actually environmentally better than the central units they displace. Additionally, this error may lead to revenue reduction. Moreover, for power systems with low average CO 2 emission level, information on marginal units operation would lead to operation of DER during the hours that they can actually reduce emissions. Otherwise, it is possible that DER may not be committed at all. Operation aiming at maximum emissions savings may reduce DER earnings and thus can be unattractive for DER, unless sufficient remuneration for the emissions avoided is provided. Participation of DER in the CO 2 emissions trading can offset the reduction of DE R earnings while reducing CO 2 emissions. For the case studied here, it is shown that aiming to maximise the earnings from combined participation in energy and CO 2 emissions market provides higher environ- mental and economic benefits compared to maximising the earnings from participatin gonlyinenergymarketand considering the CO 2 remuneration as an additional income