Design of monitoring and control systems for geothermal steam gatherings systems - comparison with the existing system for the Miravalles geothermal field

Abstract

Geothermal energy is an important source of electricity production in Costa Rica. Development and management of Miravalles geothermal field has been done by the Costa Rican Institute of Electricity, ICE, for many years. Miravalles activities have spread through a 21 km2 area where five geothermal plants, seven separation stations and 54 geothermal wells have been developed. Therefore, it is necessary to have a good monitoring and control system that acquires, stores and controls the different variables which are involved in the exploitation of the geothermal resource. SCADA (Supervisory Control And Data Acquisition), a monitoring and control system, is currently utilized for the gathering system in Miravalles geothermal field. This system includes all of the operation and production information from separation stations and geothermal wells. However, this is an 11 year old system which has become obsolete and will be upgraded soon. This report first describes how the monitoring and control system is currently utilized for the gathering system in Miravalles geothermal field, its function and identified problems. Then, some design aspects of modern monitoring and control systems in geothermal plants are described, including recent examples from Iceland. The life-time of SCADA systems, their network characteristics and the redundancy of the systems are some of the most important aspects analyzed, as well as a description of general and specific characteristics related to instrumentation and control equipment as a part of the SCADA system. Analysis, comparing this modern design and the current monitoring and control system used by Miravalles has revealed the need for some improvements in Miravalles.