Optimal Sizing and Siting of PV and Battery Based Space Microgrids Near the Moon’s Shackleton Crater

Abstract

Space mission cost and feasibility depend mainly on the size and mass of the payload. This paper investigates the optimal photovoltaic (PV) array and battery size and mass for an islanded PV-battery powered space microgrid (MG) at the lunar south pole. The PV arrays are considered to be installed on top of towers to increase solar energy harvesting. Considering the dependency of the generated power from PV arrays on the tower height, different tower heights of 10, 50, and 100 m are investigated. The paper presents the methodology to estimate the available power from the PV system using the information of illumination time-series at the location of potential sites with different tower heights. Besides, considering the power demand of several power-consuming units at different operating states, the power demand profile of the lunar base is generated. The optimal sizing of the PV and battery system for a 1-year horizon, without considering battery degradation, results in a total mass of approximately 1.5 × 10 5 kg to 3.5 × 10 5 kg with a tower height of 10 m depending on the solar illumination profiles at different sites. For a 5-year optimization horizon of the same sites with 10 m tower height and considering the battery yearly capacity degradation, total system mass ranges approximately from 2×10 5 kg to 5.5×10 5 kg. Although increasing the tower height may considerably reduce the total size and mass of the battery and PV system, the mass of the PV tower will increase. Thus, a satisfactory trade-off in selecting the site location and tower height is required. In this regard, 15 highly illuminated sites at different locations and with different PV tower heights are assessed in this paper. To improve the reliability and flexibility of the power system, the multi-microgrid (MMG) concept is deployed to distribute the power-consuming units of the base among different MGs having their local energy production and storage systems. Finally, based on the total power demand served at a candidate site and the corresponding total system mass, a criterion, mass-per-unit-load (MPUL), is used to identify the sites that serve the highest power demand with less total system mass.

Power and Energy Management System of a Lunar Microgrid—Part II: Optimal Sizing and Operation of ISRU

“…In this paper, the available power of PV arrays made up of multi-junction (MJ) GaInP/GaAs/Ge PV cells based on III-V semiconductor technology is estimated using the methodology first proposed in [7] and later updated by the authors in [13] as shown in Fig. 2.…”

“…It is worth noticing that the degradation of PV cells due to the particle radiations and low lunar temperatures is not considered in this study. A detailed description of determining the PV power generation profile from the illumination time-series profile is discussed in [13].…”

“…In [7], authors assume either a fixed value or two states for the power demand depending on daytime and nighttime at the considered location. The authors in [13] also propose generating the power demand profile of the base, taking into account the time-of-use of several power-consuming units having two states of power consumption. However, the power demand of a lunar base is largely dependent on the interaction of its subsystems and the number of crew members.…”

“…Furthermore, according to [13], a highly illuminated location might necessitate oversizing the battery to store the extra energy that can be generated by the PV system. An oversized battery increases the cost of the space mission and might render the mission impossible as the mission cost is directly proportional to the payload mass.…”

“…An oversized battery increases the cost of the space mission and might render the mission impossible as the mission cost is directly proportional to the payload mass. Therefore, the extra power generation from the PV system can be shed or utilized for other purposes, for instance, charging alternative kinds of energy storage systems (ESSs) such as regenerative fuel cells (RFCs), charging rovers, scheduling the operation of other necessary power-consuming devices, and so on which were not considered in [13]. Therefore, an efficient power management strategy is needed to optimally plan the power generation profile of the PV system considering the available solar radiation and the power demand of different power-consuming units.…”