In this paper three solutions for small scale energy conversion of
solid biomass are compared from a technical and economical
perspective. A real case study is examined, for which the reference
technology selected by designers is biomass gasification in a direct
downdraft gasifier. Produced syngas is then used in an internal
combustion engine to generate biopower. Alternative technologies
applicable within the power generation capacity range of this case
study are a Rankine cycle steam turbine or an organic fluid Rankine
cycle turbine (ORC).
Profitability and risk analysis for the reference and alternative
technologies are performed for the examined case study with a
quantitative risk analysis approach based on Monte Carlo simulation
by using the commercial software @RISK®. A spreadsheet model
was built to calculate economic performance indicators. A
commercial and literature review was performed to gather data on
input variables (biomass price, low heating value, capital costs,
maintenance costs, systems availability). For most variables, enough
data were collected to fit probability distributions as input of the
Monte Carlo model. Subjective estimates or deterministic values
were used where opportune or where not enough data for objective
estimation could be retrieved. Probability distribution of outcome
variables (biomass quantities, NPV, power costs) were thus obtained
from Monte Carlo simulation.
The probabilistic model thus obtained is used to compare
profitability and risk performance for the examined alternatives and
to assess the examined technologies, especially as to dependence on
biomass demand and uncertainty in market prices and as to
dependence on systems availability and maintenance, highlighting
that a traditional, deterministic analysis sometimes leads to less
realistic (and more optimistic) results.
