Comparison of Two LED Spectrum Engineering Approaches for Horticulture Lighting

With the improved efficiency of LED light sources and fast cost reduction in recent years, LED light sources have entered into indoor urban agriculture and vertical farming. At present, LED light sources for horticulture lighting have two main approaches to achieve required light spectra, one is monochromatic LED package and the other LED package with mixed spectra of phosphor converted light. This paper analyzes and compares these two LED spectrum-engineering approaches. The implementation methods and applicable scenarios of plant lighting will also be discussed.

1. Demand Increases for Urban Agriculture

As of year 2016, China's urban population has reached 57.35% (by China National Bureau of Statistics), the world's urban population reached 54.29%, and by 2050, 70% of the world's population will become urban population (United Nations, world population trends). As a result, the demand for urban agriculture will increase significantly. Considered as a typical type of urban agriculture, plant factories now carry out large-scale production of vegetables, seedlings, and Chinese herbs. Taking lettuce as an example, the production efficiency of unit land area is about 200 times in plant factories than in open fields^[1]. Meanwhile plant factory usually has production and sales at same location which greatly reduces transportation cost of the goods, streamlines the sales channel to reduce cost, and ensures the freshness of goods. In near future it might become the primary source of vegetables for urban population.