Quantifying the flexibility of lighting systems by optimal control in commercial buildings: Insight from a case study

Abstract

Lighting systems in commercial buildings can supply flexible services, lower grid stress caused by large peak-valley differences of electricity loads, and use a large share of fluctuating renewable energy. A flexibility quantification framework is necessary to gain a more comprehensive insight into these systems. This study proposes a methodology to quantify lighting demand flexibility and the calculation process of flexibility indicators. The flexibility indicators consist of characteristic parameters that can identify the properties of lighting power adjustments in multiple dimensions as well as performance indicators that can evaluate the capability of modifying a building’s demand profile according to the grid requirements. The proposed method is applied to quantify flexibility under the different occupancy and lighting control systems in an office building. Seasonal differences are also examined by an annual analysis. The results indicate that the average lighting power curtailment is 32.6% (4.8 kW) of peak lighting demand and the duration is about 3800 h annually. When the flexibility is managed to modify a building’s demand profile, the standard variation may decrease by 10% in heating or cooling seasons, and by around half in intermediate seasons. The consistency between flexibility and energy saving is also demonstrated.