Geography based bi-facial cell design for low LCoE

Abstract

The Levelized Cost of Electricity (LCoE) produced by PV systems is determined by yield (kWh) and cost of the system. Reducing the LCoE of the solar power can be achieved either by increasing the yield or by reducing the cost. The yield of bi-facial PV systems is promoted by high efficiency and a high bi-faciality factor.

Yield due to the front efficiency depends on the parameters ($V_{oc}$ ,$I_{sc}$ and $FF$) that contribute to that efficiency. It was found that the different parameter helped maximize the yield in each climatic condition. For low irradiation and low operating temperature zones, yield improved when the product $I_{sc} \times V_{oc} $ was increased at the cost of the $FF$. While at equatorial tropical climates with fairly high temperatures, yiele improved when $V_{oc}$ was increased at cost of $I_{sc}$ and $FF$. For high irradiance and high temperature desert climates, yield improved when the product $ V_{oc} \times FF $ increased at the cost of $I_{sc}$. Designing cells to suit the operating conditions of the region improved yield per $W_{p}$ thereby reducing the LCoE.

A large part of the cell processing cost is in the metal (silver) used on the cell. The amount of silver is usually optimized for the cell efficiency (i.e. power in W) delivered under standard test conditions, i.e. a solar irradiance of 1000 W/m2. When the metal patterns were optimized for the yield at a climatic zone, results showed that up to 50\% of silver per cell could be saved (From a reference cell considered). Up to 5\% LCoE improvement was theorized.

The irradiance on the bi-facial modules varies with different system orientations (Equator facing, East west tilted, East West Vertical ). The metal patterns were also optimized for the different system orientation at a climatic condition. The results showed metal patterns can be made more thin when designed for vertical systems.

Advanced c-Si cell concepts try to reach the theoretical efficiency by employing different passivation technologies, grid patterns, etc. Each cell technology will have advantage over the other. This makes it interesting to study if we can attribute a cell concept to a climatic condition where it will outperform other cell concepts.