Long-term capacity adequacy in electricity markets : reliability contracts vs capacity obligations

In this paper, we study the problem of long-term capacity adequacy in electricity markets. Two investment incentive mechanisms – Capacity obligations and Reliability contracts – are analyzed and compared to the benchmark design, the energy-only market. We use the dynamic programming method and real option theory to develop two dynamic models that enable one to assess the optimal market design for ensuring sufficient generation capacity to meet future demand at efficient cost (the deterministic model) and to analyze the optimal timing of investments when uncertainties in future load and fuel prices are considered (the stochastic model). The effects of different factors on investment strategies, such as the pricing of CO2 and differences between construction delays and cost structures of the new technologies, are also analyzed. The numerical results show that: (1) the reliability contract scheme would be the more cost-efficient mechanism, ensuring the long term system adequacy and encouraging earlier and adequate new investments in the system, compared to the capacity obligation method which would result in over-investment and price manipulations; (2) short lead time technology would be preferred with the capacity obligation design, while cost competitive technology would be chosen with the reliability contract scheme; (3) the pricing of CO2 and the taking into account of uncertainties would affect investment strategies but would have no impact on the effectiveness of the reliability contracts scheme.