Korea, Democratic People's Republic of

This study aims to reduce greenhouse gas emissions to the atmosphere and effectively utilize wasted resources by converting methane the main component of biogas into hydrogen. Therefore a reactor was developed to decompose methane into carbon and hydrogen using solar thermal sources instead of traditional energy sources such as coal and petroleum. The optical distributions were analyzed using TracePro a Monte Carlo ray-tracing-based program. In addition Fluent a computational fluid dynamics program was used for the heat and mass transfer and chemical reaction. The cylindrical indirect heating reactor rotates at a constant speed to prevent damage by the heat source concentrated at the solar furnace. The inside of the reactor was filled with a porous catalyst for methane decomposition and the outside was surrounded by insulation to reduce heat loss. The performance of the reactor according to the cavity model was calculated when solar heat was concentrated on the reactor surface and methane was supplied into the reactor in an environment with a solar irradiance of 700 W/m2 wind speed of 1 m/s and outdoor temperature of 25 °C. As a result temperature methane mass fraction distribution and heat loss amounts for the two cavities were obtained and it was found that the effect on the conversion rate was largely dependent on a temperature over 1000 °C in the reactor. Moreover the heat loss of the full-cavity model decreased by 12.5% and the methane conversion rate increased by 33.5% compared to the semi-cavity model. In conclusion the high-temperature environment of the reactor has a significant effect on the increase in conversion rate with an additional effect of reducing heat loss.

This paper discusses the economic operation strategy of the energy hub which is being established in South Korea. The energy hub has five energy conversion devices: a turbo expander generator a normal fuel cell a fuel cell with a hydrogen outlet a small-scale combined heat and power device and a photovoltaic device. We are developing the most economically beneficial operation strategy for the operators who own the hub without making any systematic improvements to the energy market. First sixteen conversion efficiency matrices can be achieved by turning each device (except the PV) on or off. Next even the same energy must be divided into different energy flows according to price. The energy flow is controlled to obtain the maximum profit considering the internal load of the energy hub and the price fluctuations of the energy market. Using our operating strategy the return on investment period is approximately 9.9 years which is three years shorter than that without the operating strategy.