634
N. Nakatsuka et al.
unused woody biomass, have been used sparingly as an energy source due to high
transport costs. However, they offer a highly promising energy resource, particularly
in mountainous areas (Meier et al. 2019; Rosillo-Calle 2000; Bracmort 2016). To
promote the utilization of unused biomass, combined heat and power (CHP) systems
have been used to generate both electricity and heat from woody biomass. A gasification CHP system is considered to be one of the more effective technologies because
of its high energy conversion efficiency in small-scale applications (Yoshikawa and
Moritsuka 2006; Heidenreich and Foscolo 2015a, b; Rovas and Zabaniotou 2015;
Hasler and Nussbaumer 2016; Molino et al. 2016; Park et al. 2018).
Although there are a number of methods to evaluate the environmental and
economic performance of woody biomass utilization, there remains the challenge
of designing a sustainable configuration of energy conversion systems (e.g., CHP
system) for woody biomass that takes into account both the daily fluctuations in
heat demand and the effects of long-term social changes. The purpose of this study
is to propose a method to conduct dynamic simulations of woody biomass energy
conversion systems considering time-varying heat demand. To enable such a dynamic
simulation, an energy conversion system is modeled as a sequence of processes
by means of life cycle simulation (LCS) (Umeda et al. 2000). LCS was originally
designed to simulate product life cycle flows using discrete event simulation. This
approach enables the quantitative evaluation of a product life cycle from both environmental and economic viewpoints. In this paper, annual cost and annual CO 2 emissions are used as indicators of economic and environmental performance. Alternative
scenarios are created to allow a comparative analysis of different configurations of
energy conversion systems. The case study presented here centers on a Japanese hot
bath facility in Gojo City, Nara Prefecture. Given the location of the subject facility,
the availability of a woody biomass supply from the surrounding area can be easily
assumed. Moreover, a certain amount of demand for heat and power exists.
42.2 Literature Review
Considerable research on small-scale biomass CHP systems has been conducted,
primarily from a techno-economic point of view. For example, von Doderer and
Kleynhans (2014) conducted a life cycle assessment and showed that the most
viable and sustainable bioenergy system for the Worcester biomass procurement
area region is a lignocellulosic bioenergy system composed of a feller buncher for
harvesting, a forwarder for biomass extraction, mobile comminution at the roadside, secondary transport in truck-container-trailer combinations, and an integrated
gasification system for conversion into electricity. Cleary et al. (2015) estimated
the nominal electricity generation and greenhouse gas (GHG) mitigation costs of
using harvest residue from a hardwood forest in Ontario, Canada to fuel (1) a smallscale (250 kWe) CHP woodchip gasification unit and (2) a large-scale (211 MWe)
coal-fired generating station retrofitted to combust wood pellets. Under favorable
operational and regulatory conditions, the generation costs were found to be similar.
N. Nakatsuka et al.
unused woody biomass, have been used sparingly as an energy source due to high
transport costs. However, they offer a highly promising energy resource, particularly
in mountainous areas (Meier et al. 2019; Rosillo-Calle 2000; Bracmort 2016). To
promote the utilization of unused biomass, combined heat and power (CHP) systems
have been used to generate both electricity and heat from woody biomass. A gasification CHP system is considered to be one of the more effective technologies because
of its high energy conversion efficiency in small-scale applications (Yoshikawa and
Moritsuka 2006; Heidenreich and Foscolo 2015a, b; Rovas and Zabaniotou 2015;
Hasler and Nussbaumer 2016; Molino et al. 2016; Park et al. 2018).
Although there are a number of methods to evaluate the environmental and
economic performance of woody biomass utilization, there remains the challenge
of designing a sustainable configuration of energy conversion systems (e.g., CHP
system) for woody biomass that takes into account both the daily fluctuations in
heat demand and the effects of long-term social changes. The purpose of this study
is to propose a method to conduct dynamic simulations of woody biomass energy
conversion systems considering time-varying heat demand. To enable such a dynamic
simulation, an energy conversion system is modeled as a sequence of processes
by means of life cycle simulation (LCS) (Umeda et al. 2000). LCS was originally
designed to simulate product life cycle flows using discrete event simulation. This
approach enables the quantitative evaluation of a product life cycle from both environmental and economic viewpoints. In this paper, annual cost and annual CO 2 emissions are used as indicators of economic and environmental performance. Alternative
scenarios are created to allow a comparative analysis of different configurations of
energy conversion systems. The case study presented here centers on a Japanese hot
bath facility in Gojo City, Nara Prefecture. Given the location of the subject facility,
the availability of a woody biomass supply from the surrounding area can be easily
assumed. Moreover, a certain amount of demand for heat and power exists.
42.2 Literature Review
Considerable research on small-scale biomass CHP systems has been conducted,
primarily from a techno-economic point of view. For example, von Doderer and
Kleynhans (2014) conducted a life cycle assessment and showed that the most
viable and sustainable bioenergy system for the Worcester biomass procurement
area region is a lignocellulosic bioenergy system composed of a feller buncher for
harvesting, a forwarder for biomass extraction, mobile comminution at the roadside, secondary transport in truck-container-trailer combinations, and an integrated
gasification system for conversion into electricity. Cleary et al. (2015) estimated
the nominal electricity generation and greenhouse gas (GHG) mitigation costs of
using harvest residue from a hardwood forest in Ontario, Canada to fuel (1) a smallscale (250 kWe) CHP woodchip gasification unit and (2) a large-scale (211 MWe)
coal-fired generating station retrofitted to combust wood pellets. Under favorable
operational and regulatory conditions, the generation costs were found to be similar.