閉ループ地熱システムの実行可能性をモデル化する新しいツール(New tool models viability of closed-loop geothermal systems)

2023-11-15

2023-11-14 サンディア国立研究所(SNL)

◆ジオサーマル発電は再生可能エネルギー源として注目されていますが、米国での普及には課題があります。サンディア国立研究所の研究者は閉ループ地熱システムのコンピュータモデルを使用し、その経済的実現可能性を評価しました。岩から十分な熱を抽出するためには掘削コストの大幅な削減が必要であり、2035年までにメガワット時当たり45ドルの発電コスト目標を達成するには掘削コストの急激な削減が必要とされています。

＜関連情報＞

地熱貯留層における閉ループ地熱システムの数値的検討 Numerical investigation of closed-loop geothermal systems in deep geothermal reservoirs

Mark White, Yaroslav Vasyliv, Koenraad Beckers, Mario Martinez, Paolo Balestra, Carlo Parisi, Chad Augustine, Gabriela Bran-Anleu, Roland Horne, Laura Pauley, Giorgia Bettin, Theron Marshall, Anastasia Bernat
Geothermics Available online:3 November 2023
OOI:https://doi.org/10.1016/j.geothermics.2023.102852

Highlights

•Techno-economic results of 2.5 million system designs are publicly accessible on the GDR (https://gdr.openei.org/submissions/1473).
•At $100/m drilling costs, LCOEs for 30-km single-lateral closed-loop geothermal in western U.S. HDR do not meet the 2035 DOE $45/MWh_{_e} goal for EGSs.
•Computationally inexpensive 2D axisymmetric models accurately simulated coaxial and u-shaped designs for hot-dry-rock closed-loop systems.
•Our results indicate competitive LCOH can be achieved; but competitive LCOE cannot be achieved without significant reductions in drilling costs.

Abstract

Closed-loop geothermal systems (CLGSs) rely on circulation of a heat transfer fluid in a closed-loop design without penetrating the reservoir to extract subsurface heat and bring it to the surface. We developed and applied numerical models to study u-shaped and coaxial CLGSs in hot-dry-rock over a more comprehensive parameter space than has been studied before, including water and supercritical CO₂ (sCO₂) as working fluids. An economic analysis of each realization was performed to evaluate the levelized cost of heat (LCOH) for direct heating application and levelized cost of electricity (LCOE) for electrical power generation. The results of the parameter study, composed of 2.5 million simulations, combined with a plant and economic model comprise the backbone of a publicly accessible web application that can be used to query, analyze, and plot outlet states, thermal and mechanical power output, and LCOH/LCOE, thereby facilitating feasibility studies led by potential developers, geothermal scientists, or the general public (https://gdr.openei.org/submissions/1473). Our results indicate competitive LCOH can be achieved; however, competitive LCOE cannot be achieved without significant reductions in drilling costs. We also present a site-based case study for multi-lateral systems and discuss how our comprehensive single-lateral analyses can be applied to approximate multi-lateral CLGSs. Looking beyond hot-dry-rock, we detail CLGS studies in permeable wet rock, albeit for a more limited parameter space, indicating that reservoir permeability of greater than 250 mD is necessary to significantly improve CLGS power production, and that reservoir temperatures greater than 200 °C, achieved by going to greater depths (∼3–4 km), may significantly enhance power production.