Renewable Energy Technology Assessments - Kauai Island Utility ...

Kaua’i Island Utility Cooperative
Renewable Energy Technology Assessments
3.0 Renewable Energy Technology
Options
Kauai Outlook
As discussed in the previous section, there are a large variety of potential biomass
fuels on the island that could be used to supplement coal. However, the outlook for
cofiring biomass with coal clearly depends on the development of a new coal-fired power
plant on the island. Without coal or any near term plans for coal, cofiring is not a viable
option. The last Kauai Electric Integrated Resource Plan (1997) identified a potential
24 MW coal capacity addition in 2014. Biomass could be a meaningful and cost
effective contributor to the fuel mix for this plant. It is likely that up to 25 percent of the
heat input could be feasibly (technically and economically) provided by biomass. This
would generate about 40 GWh/yr assuming an 80 percent capacity factor. Considering
this addition, the developable potential for biomass cofiring is summarized in the
following table.
Year Energy,
GWh
Table 3-5. Developable Potential from Biomass Cofiring.
Capacity,
MW
3 0 0
5 0 0
Notes
Potential is not limited by resource, but coal capacity.
Last IRP called for 24 MW of coal capacity in 2014.
10 42 6 Assumes cofiring biomass at 25 percent of 24 MW coal
plant at 80 percent capacity factor.
20 84 12 Assumes another 24 MW unit is added, with similar
cofiring.
3.2 Biogas
The biogas technology characterization generally pertains to the products of
anaerobic digestion of manure and gas produced from landfills. The following sections
detail the formation of these fuels and how each can be used to produce useful energy.
3.2.1 Anaerobic Digestion
Anaerobic digestion is the naturally occurring process that occurs when bacteria
decompose organic materials in the absence of oxygen. The byproduct gas has 50 to 80
percent methane content. The most common applications of anaerobic digestion use
industrial wastewater, animal manure, or human sewage. According to the European
Network of Energy Agencies’ ATLAS Project, the world wide deployment of anaerobic
digestion in 1995 was approximately 6,300 MWth for agricultural and municipal wastes.
21 March 2005 3-14 Black & Veatch