Design of a 800 kJ HTS SMES

In the context of a DGA (Delegation Generale pour l´Armement) project, we have designed and are going to build a 800 kJ SMES. It is based on Bi-2212 PIT tapes from Nexans operating at 20 K. Their engineering current densities exceed 300 MA/m² at 20 K and 5 T making them excellent candidates. The coil consists in 26 stacked pancakes (O = 814 mm; h = 182 mm). The conductor is made of 4 soldered tapes or 3 soldered tapes + one stainless steel tape depending on its location inside the coil. The stainless steel significantly reinforces the conductor. The conductor is insulated by Kapton. To make the cryogenics very transparent and easy for the SMES user, the coil is conduction cooled using a large capacity Gifford-McMahon cycle cryocooler. The SMES design is presented as well as some qualification tests (critical stresses, connections, etc.) for the key issues of the project.