The tradeoff between electricity cost and CO2 emission in the optimization of photovoltaic-battery systems for buildings

Abstract

Photovoltaic-battery systems for buildings are increasingly implemented to reduce electricity cost and carbon emission. However, two primary objectives of such systems, namely cost and CO2 minimization, are contradictory goals that cannot be optimized simultaneously. This paper formalizes photovoltaic-battery systems using the multi-objective mixed integer linear programming approach, optimizing the battery installed capacity and operation strategy based on the hourly electricity price and carbon emission factor. The investigation on a commercial building identifies that pursuing cost minimization can partially decrease emission, while minimizing CO2 even causes additional cost. The tradeoff between cost and CO2 diminishes when the grid becomes more volatile, and the incorporation of rooftop photovoltaics can further enhance the battery's effectiveness. As a result, a nearly zero-carbon building is economically realized through 60% renewable penetration in the grid and 50% rooftop photovoltaics, with an electricity cost of 0.05 $/kWh and a CO2 emission of 0.07 kg/kWh, respectively. Moreover, implementing a demand-side carbon tax can be facilitated with intense grid volatility. The novel approach assists buildings in adopting the most cost-effective investment and operation strategy of photovoltaic-battery systems towards zero carbon under various grid conditions.