standard rules for connection have not been developed (such as in the United States). Distributed generation can also have economic benefits to the distributor, which also need to be taken into account in establishing connection charges. Furthermore, distributed generators can enhance competition in power generation and should have access to networks on similar terms as large central stations. This suggests that a fair charging system should combine the immediate costs of connection (so-called "shallow charges") to be recovered directly from the DG developer. Any additional expenditure made by the distributor to accommodate a distributed generation project should be recovered from both DG and from ali loads in the form of use of system charges. in addition to questions associated with connection, there is an issue about the impact of structure and operation of liberalised electricity markets on distributed generation. The immediate impact of market liberalisation in Western Europe on distributed generation, particularly CHP, has been largely negative, principally as a consequence of a rise in natural gas prices at the same time that electricity prices have fallen. Governments in some countries have increased financial support in response. On the whole, market liberalisation is exposing all power producers to financial risks of the market place. DG producers, like other producers, have to be able to respond. in the long run, current conditions may encourage new DG development to be more efficient and lower cost. However, distributed generation is also underscoring the need to ensure that liberalisation is extended as broadly as possible and that pricing of electricity service be sensitive to location in order to capture an essential part of the value that distributed generation can bring. Thus while the implementation of retail liberalisation may be a necessary condition for development, it is not a sufficient condition to ensure that DG receives nondiscriminatory access to the system. Utilities that continue to own generating capacity or supply customers directly will continue to have an incentive to discriminate against generation using the utility's distribution system. in absence of structural separation, regulatory vigilance will be needed to avoid such discrimination. The design and operation of electricity markets will also affect the future of distributed generation. Market rules do provide a basis under which all market participants can trade. Distributed generation may enjoy an advantage over central generation, particularly in markets where they can avoid charges on transmission that in some systems, central generators have to pay. However, as wholesale markets are designed with principally large central generation in mind, smaller distributed generators may find themselves at a disadvantage because of proportionately higher transaction costs of being a direct market participant. Difficulties in the UK NETA market and the new Dutch market suggest that market rule changes are needed to make it easier for smaller generators to participate. Distributed generation should benefit from the pricing reforms that accompany market liberalisation. Customer exposure of the higher costs of electricity during peak periods encourages the development of distributed generation. The use of time-of-use 22.1 ECOGENERATION WORLD rates in Japan is credited for the installation of cogeneration systems that operate only during peak hours. Price is also the key to the locational value of distributed generation. Electricity distribution losses vary from less than 1 percent to 20 percent or more depending on the voltage and the location of the consumer. The value of distributed generation in deferring transmission expansion, providing ancillary services or relieving distribution congestion is also location dependent. Thus the introduction of more transparent distribution network pricing needs to recognise the value that distributed generation can bring to that network. Environmental protection Distributed generation represents a wide range of technologies with a wide range of emissions. For the fossil-fired distributed technologies, there are two key emissions impacts: the impact on local/regional air quality (particularly through emission of NOx) and the emissions of greenhouse gases. Emissions per kilowatt-hour of NOx from all but diesel-fired distributed generation tend to be lower than emissions from a coal-fired power plant or from a typical utility system with a large proportion of coal. Equally, however, the emissions rate from existing commercial distributed generation (excepting fuel cells and PV) tends to be higher than the "best available" central generation consisting ofa combined cycle gas turbine with advanced emissions control. This can pose a serious limitation on distributed generation in areas where NOx emissions are being rigorously controlled, despite the fact that they may represent a substantial reduction in emissions compared to the generation, which would be displaced (Figure 4). '" '·" 0.27 o.27 - - "' 0.00 NOx Emissions from Various Generating Technologies .... - ,., .... 0,2) 0.18 n n 0.0$ � F ..Tc -: <a .i (lOOS) The story with carbon dioxide emissions is similar. Emissions rates for distributed generation are generally lower than coal plants, but not as low as new combined cycles. However, if the distributed generation is used in combined heat and power mode, there can be significant emissions savings, even compared to the combined cycle power plant. This suggests that measures should be designed so that distributed generators can be encouraged to reduce their emissions. in particular, the use of economic instruments (such as carbon emissions trading) would encourage distributed generation operators to design and
RkJQdWJsaXNoZXIy MTcyMTY=