| 摘要 | 1. Research Purpose
It appears that there is strong movement for the promotion of distributed generation due to public policy for diffusion of district electricity business and small-scale combined heat and power.
There is strong controversy about whether we continue to support promotion policy for distributed generation. Proponents of distributed generation claim that it provides social benefits in Korea which are similar to other countries. On the other hand, the opponents to distributed generation claim that there is little social benefit in Korea because Korea is not in the same condition as other countries.
Hence, it is necessary to analyze this present dispute before we establish a comprehensive distributed generation policy.
This study puts emphasis on evaluating social benefits of distributed generation, especially congestion relief effect in a metropolitan area. It provides policy directions for the promotion of distributed generation.
2. Summary
This study analyzes congestion relief by introducing distributed generation in the metropolitan area in Korea based on the evaluation of its social benefits and costs. To facilitate the analysis, this study tries to propose the concept of distributed generation.
Summary of this study is as follows. First, there are many terms such as distributed energy resource, distributed resource, demand resource, distributed generation to represent distributed generation. Distributed generation can be defined by taking account of capacity size, location, interconnection to distribution network, demand/supply resource, operation pattern or utilization objective. Even though it is difficult to define distributed generation based on a specific criterion, it would be appropriate to define distributed generation based on electricity market rule, interconnection standard and characteristics of small-scale distributed generation. Hence, it is proposed that distributed generation be defined as resource connected to distribution network 154�� with a capacity of 20�� or less.
This study analyzes social benefits and costs of distributed generation. Social benefits include efficient use of resource, positive environment impact, reduced network cost, reduced generation cost, peak demand reduction, reduced investment risk, improvement of reliability and power quality, national energy security, reduced electricity price, etc. On the other hand, social costs include distributed generation installation costs, indoor emissions, and noise disturbance. This study tries to examine various factors that must be considered in a future cost-benefit analysis by introducing the cost-benefit analysis methodology for distributed generation. Advanced countries such as United States of America pursue to identify analytical procedures of social costs and benefits. US government evaluates and applies its priority in public policy based on derived social costs and benefits, which gives us some lessons in distributed generation policy-making.
This study examines congestion costs, and impact of distributed generation on congestion relief in the seoul metropolitan area. Its results are as follows.
It is expected that reserve margin in the metropolitan area will be 11~14%, below the appropriate level, until 2010, and go up to 15~19%, similar to the appropriate level, after 2011.
This study analyzes the trend and characteristics of congestion cost from 2008 to 2015, and combined heat and power is assumed for distributed generation technology.
The base case assumes that the transmission capacity expansion plan shown in the 3rd electricity demand/supply resource plan will be implemented. In that case, the average congestion cost is estimated at 3.6 won/kWh with the heat-oriented operation mode, but at 5.1 won/kWh with the electricity-oriented operation mode.
On the other hand, the shortage case assumes that the transmission capacity expansion plan shown in the 3rd electricity demand/supply resource plan will not be implemented. In that case, the average congestion cost will be estimated at 8.1 won/kWh with the heat-oriented operation mode, but at 10.7 won/kWh with the electricity-oriented operation mode.
Unexpectedly, more congestion takes place during off-peak hours rather than peak hours. And congestion takes place more in summer than winter, and on holidays than other week-days.
Congestion cost in the base case accounts for at least 5.23% at most 7.40% in the electricity wholesale price. On the other hand, congestion cost in the shortage case accounts for at least 11.76% at most 11.53% in electricity wholesale price. This implies that the congestion cost in the metropolitan area is not small due to its concentrated demand for electricity. Thus, if the transmission expansion is not materialized as planned, considerable congestion costs will be inevitable.
The large congestion cost takes during off-peak hours than peak hours implies that peak shaving effect by distributed generation does not necessarily coincide with congestion relief.
One of limitations of this study is not to cover other distributed generation technologies, when analyzing congestion cost because of diverse technology sources and the lack of data.
3. Research Results and Policy Suggestions
Results of thus study can be put to good use for the formulation of the government policies on distributed generation.
Firstly, the current electricity pricing scheme is a factor against in the desirable promotion of distributed generation. The government may consider to remove cross-subsidy among regions and introduce a locational pricing scheme for the effective diffusion of distributed generation.
Secondly, since congestion takes place in summer, it is desirable for distributed generation to be operated in the season. And, since congestion takes place in the off-peak period, it is desirable for distributed generation to be operated in the period so that it may contribute to mitigate congestion.
Thirdly, congestion in the electric power system is affected by the capability of transferring electricity, it is necessary to monitor whether the long-term transmission expansion plan will be implemented smoothly. If the plan would not be implemented by some external environmental factors, distributed generation would play some role in relieving congestion.
Finally, it is necessary to establish a standard methodology to evaluate social benefits and costs of distributed generation. Some developed countries have made significant advancements in these fields which are a solid basis for policy-making. |
