Modeling and performance analysis of solar parabolic trough collectors for hybrid process heat application in Kenya’s tea industry using system advisor model

Abstract

Among the Concentrated Solar Collector (CSC) technologies, Parabolic Trough Collector (PTC) is the most mature and commercialized CSC technology today. Currently, solar PTC technology is mainly used for electricity generation despite its huge potential for heating, especially in industrial process heat (IPH) applications. Though the technology is well-developed and successfully used in many developed countries, there is barely any development in Kenya. This paper studies the techno-economic feasibility of a solar PTC-assisted tea drying process in one tea factory that currently relies on biomass for process heat, in the tea producing area of Kericho, Kenya. The plant integrating parabolic troughs is modelled and a yearly simulation performed using System Advisor Model (SAM) software. The weather data are derived from ground measurements at Kericho meteorological weather station. SAM is used to model the impact of the principal design parameters, i.e., solar multiple (SM), thermal energy storage (TES) and hybridization percentages, on solar–biomass plant configurations, and to reveal the optimum case. The studied impacts are linked to the annual energy production and the optimal size which minimizes the levelized cost of heat (LCOH). Analysis of monthly variations of energy production by the solar PTC reveals that even when the solar system is designed to its maximum capacity (SM of 3 and TES of 24 h), some months will still require hybridisation with biomass to fully meet the energy demand. TES must also be incorporated in the solar PTC design to maximise on energy production. The hybrid solar–biomass plant with TES provides optimal performance when SM is 1.8 and TES is 24 h. This results in LCOH of 1.85 US cents/kWh, which is 25% cheaper than using biomass only as is the current practice. Furthermore, integration of solar PTC has a positive impact on carbon footprint and considerably reduces annual greenhouse gas (GHG) emissions by 9817 tons of CO2-eq, and annual fuel wood consumption by 16,462 m3 (equivalent to 23.51 acres of mature grown trees).