| |
CHP
plant at Kahoku town
 |
|
Kahoku Town is located in Kochi Prefecture, at southern part of
Shikoku Island and its forestry area is 84%. Therefore, abundant wood resources
are utilized in Kochi Prefecture. Further, high performance machines such as
processors are actively induced. Kahoku Town has the area of 130 km2,
population of 5,758 and four public facilities. Since there are many sawmills
and wood markets around Kahoku Town, it is easy to gather biomass fuels from
nearby towns.
|
|
Description
Financial resources / Economic Benefits
Results
 Energy
production
Contact
Description
Figure 1 shows a system flow of model. Three cases of
co-generation systems were considered. In the case 1, a gas turbine of 250 kW
runs 10 hours a day. All the electricity and heat production is utilized in
four public facilities. In the cases 2 and 3, a gas turbine of 500 kW (case 2)
and a steam turbine of 1,000 kW (case 3) continuously run. Their heat
production is supplied to the public facilities, but all electricity produced
is sold. Therefore, the public facilities bought electricity from grid.
Figure 1 System flow of model
Financial resources / Economic Benefits
Table 1 shows costs of the biomass feedstock used. Two kinds of
the feedstock, sawmill waste (most of that is bark) and the forestry waste, are
utilized. Available amounts of sawmill and forestry wastes are 12,056 Gcal/y
and 44,872 Gcal/y, respectively. Since the cost of sawmill waste is much
cheaper than that of forestry waste, all cases precede use of sawmill waste. In
the case 3, since large amount of feedstock is needed, the rate of expensive
forestry waste is higher than that of sawmill waste, and total cost of the case
3 is higher than that of the others.
Table 1 Cost of biomass feedstock
| |
Available amount 1000 Mcal / year |
Unit cost
/ Mcal
|
Amount (1000 Mcal/y) and ratio (%) |
| Case 1 |
Case 2 |
Case 3 |
| Wastes from sawmills (mainly bark) |
12,056 |
0.7
|
4,019 |
88% |
12,056 |
72% |
12,056 |
32% |
| Forestry waste (tree top, branch and leaf etc). |
44,872 |
4.33
|
558 |
12% |
4,382 |
28% |
25,162 |
88% |
| Total |
56,929 |
|
4,576 |
|
16,741 |
|
37,688 |
|
| Total unit cost (\ / Mcal)
|
1.14 |
|
1.72 |
|
3.17 |
|
Table 2 shows results of economical analysis of the case 1. The
equipment cost includes the co-generation installation, the absorption type
refrigerator to cool in summer season and the thermal supply pipe arrangement.
Since the distinct heat system is not popularized in Japan, the cost unit of
the thermal supply pipe is very high and its cost accounts for more than 50% of
the equipment cost.
Table 2 Economical analysis (Case 1)
| Equipment cost |
Co-generation installation |
250,000 k\ |
1 million \ / kW |
| absorption type refrigerator |
20,000 k\ |
120 USRT |
| Thermal supply pipe arrangement |
300,000 k\ |
300 k\ / m |
| Total |
570,000 k\ |
|
| Electric output |
Total electricity produced |
1,004 MWh/y |
|
| Self-consumption in the facilities |
709 MWh/y |
|
| Bought electricity |
413 MWh/y |
At night |
| Sold electricity |
295 MWh/y |
In the daytime |
| Selling cost unit |
4 \/kWh |
|
| Income by selling |
1,181 k\/y |
|
| Thermal supply |
Total heat production |
2,379,627 Mcal/y |
|
| Available capacity in the facilities |
1,562,889 Mcal/y |
|
| Thermal utilization efficiency |
51% |
|
| Thermal supply income |
13,597 k\/y |
8.7 \/Mcal |
| Running cost |
Labour cost |
12,000 k\/y
|
2 employees
6 million\/y |
| Maintenance and utility cost
|
1,506 k\/y |
10% of facilities depreciation |
| Feedstock cost |
5,217 k\/y |
|
| Total |
18,723 k\/y |
|
| Expense per year |
Facilities depreciation (except for thermal supply pipe)
|
21,006 k\/y
|
Interest: 2%
Durable year: 15
Expense rate: 7.76%
|
| Facilities depreciation (only thermal supply pipe) |
10,980 k\/y |
Interest: 2%
Durable year: 40
Expense rate: 3.66% |
| Running cost |
18,723 k\/y |
|
| Ash treatment cost |
854 k\/y |
|
| Buying electricity cost |
5,033 k\/y |
21.2 \/kWh |
| Selling electricity income |
-1,181 k\/y |
|
| Thermal supply income |
-13,597 k\/y |
|
| Total expense per year |
41,817 k\/y |
|
| Total cost unit |
|
37.28 \/kWh |
|
Results
Energy production
Table 3 shows energy balance of each case. In the case 1, most
of electricity produced is utilized in the facilities and about 30% of excess
production is sold. But at night, it is needed to buy about 400 MWh of
electricity. For thermal utilization, all cases produce excess amount of heat
compared with the total available capacities of four facilities. Therefore, the
heat utilization efficiencies are very low.
Table 3: Energy balance
| |
|
|
Case 1 |
Case 2 |
Case 3 |
| Rating efficiency
|
Electric power |
% |
22.5 |
22.5 |
22.0 |
| Thermal recovery |
% |
56.0 |
56.0 |
60.0 |
| Electric power output |
Self-consumption |
MWh/y |
700 |
0 |
0 |
| Buying output |
MWh/y |
413 |
0 |
0 |
| Selling output |
MWh/y |
295 |
4,380 |
8,760 |
| Total |
MWh/y |
1,004 |
4,380 |
8,760 |
| Thermal utilization |
Total heat exhaust |
Gcal/y |
2,480 |
8,705 |
22,601 |
| Efficient utilization |
Gcal/y |
1,563 |
1,563 |
1,563 |
| Actual efficiency |
Generator Loading |
% |
100 |
100 |
100 |
| Heat exhaust utilization |
% |
50.6 |
18.0 |
8.8 |
| Total co-generation efficiency |
% |
50.8 |
32.6 |
28.3 |
In the daytime, the surplus of electricity (295 MWh/y) is sold.
However, there is no incentive to bioenergy and the selling cost unit is very
cheap. Since the cogeneration system run between 8 am and 6 pm, electricity of
413 MWh/y needed after 6 pm has to be bought. Thus, the co-generation system
can not supply all electricity used in the public facilities, while total heat
production from the co-generation system largely exceeds the available capacity
in the facilities.
Contact
|
|
expert login
