Development of Small-Scale CHP Plant with a Wood Powder-Fueled Stirling Engine

Abstract

Small-scale biomass CHP (combined heat and power) plants are in demand for environmental reasons -particularly systems fueled by wood waste, which are simple to operate and require no maintenance while having high thermal efficiency similar to oil-fired units. A 55kWe Stirling engine CHP system, combined with a simplified biomass combustion process that uses pulverized wood powder has been developed to meet these requirements. Wood powder of less than 500 µm was mainly used in these tests, and a combustion chamber length of 3 m was applied. Under these conditions, the air ratio can be reduced to 1.1 without increasing CO emissions by less than 10 ppm, and with combustion efficiency of 99.9%. Under the same conditions, NOx emissions are estimated to be less than 120 ppm (on the basis of 6% O 2 ). Wood powder was confirmed to have excellent properties as a fuel for Stirling engines. The 55 kWe Stirling engine performance test was carried out to optimize the operating condition of wood powder burners. The status of Stirling engine operation at a full load with 55 kWe was stable, and start-up and shut -down operations were easy to perform. Operational status was evaluated as being excellent, except for an ash fouling problem in the Stirling engine heater tubes. Ash fouling characteristics were considered in the final stage of the demonstration test. This paper summarizes the wood powder combustion test and Stirling engine performance test. Furthermore, the ash fouling data is shown and the mechanism of ash fouling in heater tubes is discussed.

Numerical simulation for the design analysis of kinematic Stirling engines

“…In this sense, different prototypes suitable for CHP applications have been recently developed. Some examples correspond to the prototypes developed by Sato [30], Nishiyama [42],Biederman [43], Zeiler [44], Li [33] and Obara [45]. In addition, some field tests were reported by Thomas [5] and Klemes [6].…”

“…Few integration studies presented some approaches. For example the works of Lombardi [29], Sato [30], Entchev [31], Pålsson [32], and Li [33]. However, these are limited by the use of empirical and first order models that do not reflect the thermodynamics of the engine.…”

CO₂-Neutral Generation of Heat and Power in Smart Homes by Organic Rankine Cycle Powered Combined Heat and Power Micro Plants

“…Stirling engines require a high temperature to start. This leads to two problems: Since the combustion gases can only be partially used, a large proportion of low temperature heat is not exploitable [10]. Additionally, the necessary high combustion temperatures are critical.…”

Thermodynamic analysis of a gamma type Stirling engine in an energy recovery system

“…An evaluation was carried out by Kuosa et al [17] on the numerical evaluation of an alpha Stirling engine using the fouling factor to determine the effect of heat exchangers on Stirling engines for CHP application; the analysis considered the brake efficiency, output power and heat recovery to optimise the cleaning interval of the heat transfer surfaces when the cost model is combined with the performance model. Sato et al [18] conducted a study on the use of a 55 kW e Stirling engine in a CHP unit powered by wood powder. The combustion and inlet gas temperature were optimised to develop a cleaning process for hot ash, due to the ash fouling that was observed in the heat exchangers of the engine.…”