Energy Efficient Lighting in Plant Factories: Addressing Utilance

Jens Balasus,Janis Blank,Tran Quoc Khanh,Tim Hegemann,Sebastian Babilon

doi:10.3390/agronomy11122570

Abstract

Vertical farming is considered to play a crucial role in future food supply. Until today, the high amount of electrical energy required for artificial lighting has been problematic in this context. Various possibilities for increasing efficiency through adapted lighting conditions have been and are being investigated. However, comparably little attention is paid to increasing utilance, i.e., the amount of photons that can effectively be used by the plant. In this work, a novel targeted lighting strategy is therefore proposed that allows for a dynamic adaptation of the luminaires’ light distribution to match the effective crop size at each stage of plant growth in a fully-automated manner. It is shown that the resulting utilance can significantly be increased compared to standard full-coverage lighting. Moreover, it is found that the proposed strategy is likely to consume less than half of the electrical energy usually required for the latter. An additional increase in system efficiency can be prognosticated and the potential energy savings are estimated based on assumptions of future LED generations derived from literature.

Highlights

Ryong JeongVertical indoor farming comes along with a lot of benefits ranging from a stable year-round production, high productivity, and crop quality to higher yields per land area and less impact on the environment due to the development of water, fertilizer, and pesticide-saving cultivation methods [1,2,3,4,5]
The reported amounts of electrical energy typically needed for horticultural lighting in plant factories vary between studies and range from 52 % up to 80 % [12] of the total energy required for an optimal plant growth
A novel, fully-automated lighting strategy has been proposed to adapt the light distribution of the horticultural luminaire to match the effective leaf surface area at each stage of plant growth in order to minimize the wasting of optical radiation throughout the growing process

Summary

Introduction

Ryong JeongVertical indoor farming comes along with a lot of benefits ranging from a stable year-round production, high productivity, and crop quality to higher yields per land area and less impact on the environment due to the development of water-, fertilizer-, and pesticide-saving cultivation methods [1,2,3,4,5]. The cultivation of crops in such closed environments allows for the explicit and optimal control of environmental parameters affecting plant growth [6], but at the same time requires natural daylight to be replaced by artificial light sources to drive the process of photosynthesis [7,8,9], which considerably increases the demand for (electrical) energy. Even though modern LED packages and chip-on-board (COB) modules with high efficiencies are used as light sources, the amount of electrical energy needed for production is often stated to be the limiting factor for a broad scale application of vertical and indoor farming technologies. The reported amounts of electrical energy typically needed for horticultural lighting in plant factories vary between studies and range from 52 % (calculated with data from [11]) up to 80 % [12] of the total energy required for an optimal plant growth

Objectives

Methods

Results

Conclusion