RESEARCH ARTICLE Improving clean energy greenhouse heating with solar thermal energy storage and phase change materials Zahra Naghibi | Rupp Carriveau | David S.-K. Ting Turbulence and Energy Laboratory, University of Windsor, Windsor, Ontario, Canada Correspondence Rupp Carriveau, Turbulence and Energy Laboratory, University of Windsor, 401 Sunset Avenue, Windsor, ON, Canada. Email: rupp@uwindsor.ca Funding information Agricultural Adaptation Council Abstract Greenhouses consume a great deal of energy to heat their building envelopes. The strategic integration of solar energy and thermal energy storage (TES) can help to boost energy performance and reduce the carbon emission in the sec- tor. In this paper, the benefits of adding phase change materials (PCM) to the water tank of a solar heating system have been evaluated using the Transient System Simulation (TRNSYS) program. Initially, the hourly heating load of a reference greenhouse was evaluated using TRNSYS software. The results were validated with natural gas consumption data. The validated simulation was then used to investigate the impact of PCM on the performance of a large-scale solar energy system. Four system configurations were evaluated; no PCM materials in the tank, then 20%, 40%, and 60% of the water tank volume occu- pied by PCM. Energy performance improvements of 10% to 14% were observed by increasing the proportion of PCM amounts over the baseline conventional system. Finally, an economic study was conducted to investigate the cost feasi- bility of different PCM concentrations. It was shown that PCM price, cost of natural gas, and carbon tax are the principal influence factors on the payback period. KEYWORDS greenhouse, phase change material (PCM), solar heating system 1 | INTRODUCTION Like other sectors, agriculture is challenged in its pursuit of sustainability. 1 The gap between growing populations and food supply can drive food uncertainty. 2 Climate change, 3 poor water resources, 4 soil degradation, 5 and urban sprawl 6 also contribute to the challenge of meeting the planet's food demand. Greenhouses can be positioned to increase agriculture's sustainability profile through micro-climate control, 7 the insulation from severe weather events, pests, and diseases. These strengths of indoor agriculture do not come without cost. Successful greenhouse operation requires significant investments in capital expenditures, labor, and energy consumption. 8 These are among the most critical inputs to greenhouse operation. 9 Among them, space heating is one of the most significant costs in the greenhouse, 10 particularly in cold climates. A variety of heating solutions are employed in these operations. Conventional solutions are based in fossil fuels. 11 However, limitations on carbon gas emis- sions, fuel price volatility, and concerns over brand Abbreviations: COP, coefficient of performance; CT, carbon tax; CTI, carbon tax inflation; CWEC, Canadian weather for energy calculation; DHWS, domestic hot water system; ITES, ice thermal energy storage; LCS, life cycle savings; NG, natural gas; NGI, natural gas inflation; PBP, payback period; PCM, phase change material; PW, present worth; (S) TES, (solar) thermal energy storage; SF, solar fraction; STR, solar thermal ratio; TRNSYS, Transient System Simulation Program. Received: 18 October 2019 Revised: 29 November 2019 Accepted: 30 November 2019 DOI: 10.1002/est2.116 Energy Storage. 2020;2:e116. wileyonlinelibrary.com/journal/est2 © 2019 John Wiley & Sons, Ltd. 1 of 14 https://doi.org/10.1002/est2.116