High-Temperature Capacitors for Geothermal Applications

Enhanced Geothermal Systems technology is capable of providing up to 100 billion watts of electricity within 50 years, by utilizing the United States¿ abundant, clean, renewable geothermal resources. In order to exploit this energy in a cost-effective manner, and thereby establish it as economically competitive, diagnostic-while-drilling tools must be used. However, these tools, which must accompany the drill bit, experience very high temperature (~250°C) environments. Unfortunately, electronic components, particularly capacitors, that can operate in this heat are not widely available. To meet the temperature requirement, currently-used capacitors are typically bulky, which makes it extremely difficult to fit the electronic package in a bore hole. In previous work, a novel Type H dielectric, which provided the relatively high dielectric constant needed for making compact capacitors, was developed. In addition, the Type H dielectric provided a flat dielectric response at temperatures up to 250°C. However, its insulation resistance above 200°C was too low. Therefore, this project will develop a controlled doping technique that will increase this resistance at 250°C by trapping charge carriers. In Phase II, an ultra-stable variant of the Type H family will be developed to add flexibility to the designer¿s toolbox. Commercial Applications and other Benefits as described by the awardee:In addition to enabling more efficient and reliable geothermal energy harvesting, the high-temperature compact capacitors should find use in the oil exploration sector. On the military/aerospace side, high-temperature-capable compact capacitors are needed in space-based weapon systems and other orbiting platforms for use in sensing, power, and attitude-control electronics that are exposed to solar radiation for extended periods.