Generation of heat and power from biogas for stationary applications: boilers, gas engines and turbines, combined heat and power (CHP) plants and fuel cells - The Biogas: Science, Production and Applications - page 415

Table 17.5 Advantages and disadvantages of various fuel cell technologies

Fuel cell type Advantages Disadvantages

Polymer
electrolyte
membrane
(PEMFC)

. Solid electrolyte reduces

corrosion & electrolyte
management problems
. Low temperature
. Quick start-up

. Requires expensive catalysts

. High sensitivity to fuel

impurities
. Low-temperature waste heat
. Waste heat temperature not
suitable for combined heat
and power (CHP)

Direct
methanol
(DMFC)

. High energy storage . Low power output

. No reforming needed . Methanol is toxic and

flammable . Easy storage and transport

Alkaline
(AFC)

. Cathode reaction faster in

alkaline electrolyte

. Expensive removal of CO 2

from fuel and air streams
required (CO 2 degrades the
electrolyte)

. Higher performance

. Low-cost components

Phosphoric
acid (PAFC)

. Higher overall efficiency with

CHP

. Requires expensive platinum

catalysts

. Increased tolerance to

impurities in hydrogen

. Low current and power

. Large size/weight

Molten
carbonate
(MCFC)

. High efficiency . High temperature speeds

corrosion and breakdown of
cell components

. Fuel flexibility

. Can use a variety of catalysts

. Suitable for CHP . Complex electrolyte

management

. Slow start-up

Solid oxide
(SOFC)

. High efficiency . High temperature enhances

corrosion and breakdown of
cell components
. Slow start-up
. Brittleness of ceramic
electrolyte with thermal
cycling

. Fuel flexibility

. Can use a variety of catalysts
. Solid electrolyte reduces
electrolyte management
problems
. Suitable for CHP
.

￿ ￿ ￿ ￿ ￿ ￿

Hybrid/gas turbine (GT) cycle

Source: adapted with permission from U.S. Department of Energy (US DOE,
2011); permission granted 10 September 2012.

In a continuous cycle, ambient air is compressed in the compressor and
transmitted to the combustion chamber, where biogas is introduced and
combustion takes place at a maximum temperature of 1200 C (Deublein

and Steinhause, 2008). The produced flue gas is then passed to a turbine,
where it expands and transfers its energy to the turbine. The turbine propels
the compressor on the one hand and the generator on the other hand to
produce power. The exhaust gas leaves the turbine at a temperature of
approximately 400-600

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C (Deublein and Steinhause, 2008). The waste heat
can be used in a steam turbine downstream, for heating purposes, or for pre-

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