Energy outputs and emissions of biodiesels as a function of coolant temperature and composition

Strict emission legislation forced engine manufacturers to replace fossil diesel with sustainable biofuels. Biodiesel combustion produced lower thermal efficiency and higher nitric oxide (NO) emissions. The NO gas emissions depend on the saturated fatty acid (SFA) and unsaturated fatty acid (USFA) levels present in the plant oil. To overcome biodiesel combustion challenges, effective utilisation of engine waste heat could help in achieving high thermal efficiency and low emissions. Effects of biodiesel SFA and USFA levels, and engine coolant temperature on four different biodiesel types are studied. Lamb fat biodiesel (LFB), chicken fat biodiesel (CFB), waste cooking oil biodiesel (WCOB), and Karanja biodiesel (KB) were used. LFB and CFB have higher SFA%, whereas WCOB and KB have higher USFA%. The coolant temperature was varied from 65 °C to 85 °C at different engine loads. It was observed that with increased coolant temperatures, the brake thermal efficiency of the engine was increased by 4–5% with LFB and CFB compared to diesel, due to reduced heat losses and better oxy-fuel combustion. The NO and CO2 emissions for high SFA fuel (LFB and CFB) were reduced by 19–22% and 0.2–6%, respectively, as compared to USFA rich fuel (WCOB and KB) and diesel fuel. However, smoke emissions were found to be higher for CFB, WCOB, and KB than diesel, but LFB produced 4–6% less smoke than USFA (WCOB and KB) and diesel fuel. The study concludes that coolant temperature influences engine performance and pollutants, but use of appropriate SFA-level biodiesel could reduce emissions without compromising thermal efficiency

Optimal Parameter Identification of Single-Sensor Fractional Maximum Power Point Tracker for Thermoelectric Generator

A thermoelectric generator (TEG) is used for converting temperature difference and into DC directly to electric energy based on the Seebeck effect. This new technology has attracted researchers of sustainable energy. The energy obtained from the TEG depends on the temperature difference between the two sides of the TEG. A reliable MPP “maximum power point” tracker (MPPT) is mandatory to guarantee that the TEG is working close to the MPP under different operational conditions. There are two common methods that have been widely used to track the MPP: hill climbing (HC) and incremental conductance (INR). The HC method is very fast in tracking the MPP; however, oscillation can occur under a high steady state. On the contrary, the INR method needs more time to track the MPP but does not oscillate around the MPP. To overcome these issues, fractional control is adopted. Furthermore, the proposed MPPT requires only a single current sensor, as opposed to conventional MPPTs, which require at least two sensors: current and voltage sensors. The cost of the control system is reduced when the number of sensors is reduced. Hunger games search optimization is used to estimate the parameters of a single sensor optimized fractional MPPT (OFMPPT). During the optimization process, three parameters were assigned as decision variables: proportional gain, integral gain, and order, with the objective function being the TEG’s energy. The results demonstrated the superiority of OFMPPT in both transient and steady state compared to HC and INR