The increasing integration of wind energy in power systems can be responsible for the occurrence of over-generation, especially during the off-peak periods. This paper presents a dedicated methodology to identify and quantify the occurrence of this over-generation and to evaluate some of the solutions that can be adopted to mitigate this problem. The methodology is applied to the Portuguese power system, in which the wind energy is expected to represent more than 25% of the installed capacity in a near future. The results show that the pumped-hydro units will not provide enough energy storage capacity and, therefore, wind curtailments are expected to occur in the Portuguese system. Additional energy storage devices can be implemented to offset the wind energy curtailments. However, the investment analysis performed show that they are not economically viable, due to the present high capital costs involved.

Electricity markets are systems for effecting the purchase and sale of electricity using supply and demand to set energy prices. Three major market models are often distinguished: pools, bilateral contracts, and hybrid models. This article addresses the challenge of using software agents with negotiation competence to help manage the complexity of electricity markets, particularly the issues associated with the negotiation of bilateral contracts. Specifically, it presents a multi-agent energy market and describes a case study on forward bilateral contracts.