NEW TOOLS TO ENCOURAGE ACTIVE DEMAND RESPONSE IN COMPETITIVE ELECTRICITY MARKETS: IMPLEMENTATION AND SETTLEMENT In the new situation where electricity markets are involved nowadays, competition is becoming more and more important for the power sector. In this competitive framework, the different technical and economical mechanisms to achieve an optimal management of electricity systems must be taken into account. For that reason, the active participation of consumers in electricity markets-defined as the ability of a customer to react to energy prices has to be considered as a fundamental objective to make deregulated markets work properly. Some years ago (in the mid 70s), different programs began to be developed in order to increase active participation of demand; the expected results were not achieved though. Some of the explanations behind this fiasco are: from a technical point of view, more accurate systems that permit the acquisition and processing of information were vital; logistically, it is important to show these programs to the customer in a clear detailed and attractive way, as well as the definition of a clear mechanism for an objective payment the customer who provides with this service, based on price signals. This dissertation is aimed at designing and implementation of tools to promote the use of active demand response for the management of electricity systems. In order to achieve this objective, different actions have been performed, including the design and implementation of a system for the control and management of facilities which makes it easier for the active demand response use. Thus, after analyzing the limitations of existing control systems for this purpose, a new system is proposed. It permits one to get in touch with different agents who may be interested in the use of available distributed energy resources. Moreover, this system represents an essential tool to establish a mechanism to measure the actual response of demand in order to facilitate the process of payment to consumers for their participation in operation markets. It is essential to establish an accurate methodology to compare the real consumption during the control action with the energy that the customer would have consumed in case any control action had not been carried out. This means that, on one hand, an accurate measurement of the consumption must be provided by the proposed system and, on the other hand, a reliable and accurate forecast of what the customer would have consumed if no actions had been performed have to be obtained. Due to the low aggregation level in the considered loads, a new prediction method based on artificial neural techniques has been developed. This method is proposed for the prediction of consumptions for each process or end-use of energy. Here, the training of the neural networks is done by using real measurements or simulations obtained by means of physical models for the different processes.