Civil Engineering Reference
In-Depth Information
From among the CHP technologies presented, the most appropriate for residential
use are the technologies presented in Table
7
. The electric ef
ciency of reciprocating
internal combustion engines is higher compared to micro-turbines and Stirling
engines. On the other hand, fuel cells promise to offer the highest electric ef
ciency
for residential and small-scale cogeneration applications in comparison with the
other technologies, but are challenged by lack of demonstrated performance.
To better understand the potential bene
ts of different micro-CHP technologies,
a comparative study [
19
,
20
] involved a major
field trial of micro-CHP units in
domestic applications, with a corresponding trial of A-rated condensing boilers to
provide a baseline for comparison.
As expected, the measured thermal ef
ciencies for the micro-CHP units are
around 10
15 % lower than for the condensing boilers. This is primarily a con-
sequence of some of the heat generated by the engine being used to generate
electricity.
-
Table 7 Technical features of small-scale CHP Devices [
8
,
10
,
15
,
19
]
Reciprocating
engines
Microturbines
Stirling engines
PEM fuel cells
Electric
power (kW)
10
-
200
25
-
250
2
-
50
2
-
200
Electric
ef
ciency,
full load (%)
24
-
45
25
-
30
15
-
25
40
Electric
efficiency,
half load (%)
23
-
40
20
-
25
25
40
Total
efficiency (%)
75
-
85
75
-
85
75
-
85
75
-
85
Heat/
electrical
power ratio
0.9
-
2
1.6
-
2
3
-
3.3
0.9
-
1.1
Output
temperature
level (
°
C)
85
-
100
85
-
100
60
-
80
60
-
80
Fuel
Natural or
biogas, diesel
fuel oil
Natural or
biogas, diesel,
gasoline,
alcohols
Natural or biogas,
LPG, several
liquid or
solid fuels
Hydrogen, gases,
including hydrogen,
methanol
Interval
between
maintenance
(h)
5,000
-
20,000
20,000
-
30,000
N/A
5,000
Investment
cost ($/kW)
800
-
1,500
900
-
1,500
1,300
-
2,000
2,500
-
3,500
Maintenance
costs ($/kW)
1.2
-
2.0
0.5
-
1.5
1.5
-
2.5
1.0
-
3.0
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