Environmental Engineering Reference
In-Depth Information
Micro−CHP efficiencies
100
Electrical vs Capacity
Thermal vs Capacity
90
80
70
60
50
40
30
20
10
0
10
20
30
40
50
60
70
80
90
100
Electrical power capacity (kW
el
)
Figure 4.11
Electrical and thermal power efficiencies of available micro-CHP
systems [76]
the dispatch strategies these dispersed generators adopt. Hence, some factors involved
in making CHP operating decisions include [93]:
Electrical and thermal power demand of the dwelling;
●
Efficiency and capacity of the CHP unit and the availability of storage;
●
Cost of energy prices, feed-in tariff schemes and other market characteristics.
●
A dispatch strategy or mode of operation is characterised by the criteria on which
the adjustment of electric and thermal power production of a CHP system is based
upon. Today there are various operation strategies commonly practised, serving as
a reference for the TCOPF criteria employed in its modelling scenarios; the most
popular are [88]:
Heat-led strategy
: The useful thermal output of a CHP system tries to be for
most of the time equal to the thermal load (without exceeding the capacity). If
the heat capacity of the system is exceeded, an auxiliary boiler or thermal energy
storage (TES) system can be used. Now, if the generated electricity is higher
than the load, excess electricity is exported and sold to the grid; if it is lower,
supplementary electricity is imported and purchased from the grid. In general,
this operation strategy results in the highest primary energy savings.
●
Electricity-led strategy
: The generated electricity tries to be for most of the time
equal to the electrical load (naturally within its capacity limits). If the cogenerated
heat is lower than the thermal load, an auxiliary boiler or TES covers the deficit;
●
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