A Solar Cell System for Extension of Battery Run Time in a Moving Actuator Total Artificial Heart

Abstract

An implantable total artificial heart (TAH) system has strong dependence upon the external battery performance for operation. Even under sophisticated battery management control, the usable external battery performance continues to decrease, which limits TAH performance. One of the ways to overcome this energy problem is to use a solar system (SS). An SS can provide electrical power for the partial TAH drive or battery recharge. This article presents a new concept for use of the solar cell for obtaining double external battery performance. To achieve it, numeric simulations were carried out to obtain the proper magnitude of solar parameters. In the TAH used, the battery power for a cardiac output of 4-6 L/min is approximately 17 W/20 min. From simulated results, the optimal power and voltage of the SS were found to be 7 W, Voc = 27 V in the case of the 24 V motor. Each solar cell includes Voc = 0.5 V, Isc = 37 mA/cm2, FF (fill factor) = 0.77, and efficiency = 10%. Based on the simulation, the effect of solar power capacity on battery run time was studied. With use of 6.5 W SS (W 304 x H 245 x D 16 mm, 1.1 kg), battery performance decreased in vitro from 100% (fully charged) to > 55% vs 0% in the conventional battery system after 20 min operation. However, it dropped to below 20% when using W SS (W 192 x H 192 x D 16 cm, 0.6 kg). The results showed doubled battery run time could be obtained compared with a system without the SS. It was concluded that the proposed SS can be put to practical use as a future energy source for a TAH.