 | Application of Biomass Energy Technologies (HABITAT, 1993, 168 p.) |
 |  | VI. CONVERSION OF BIOMASS INTO ELECTRICITY |
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H. Mali
Chinese-built rice-husk gasifier power plants (160 kWh) were installed in the early 1970s, according to Mahin (1989), at two rice mills at Dogofiri and N'Debougou. These have operated successfully since then with more than 55,000 hours operating experience, although economic analyses of these plants are not easily available. In 1986, with the assistance of GTZ (German Agency for Technical Cooperation), an additional Chinese-built gasifier was installed nearby at the rice mill in Molodo which processes about 20,000 t/yr of rice. The plant produces about 1 kWh for each 2.5 kg of rice husks used in the gasifier. It generates up to 160 kW of power. The total annual operating costs were DM146,877 (or DM0.26/kWh) which is 54 per cent of that of a diesel- engine plant. The GTZ study (Mahin, 1989) indicates the difference in capital cost between the diesel and the gasifier plant. Investment costs of the gasifier power plant could be recovered in less than four years. Table 16 provides a summary of cost of the rice husk-fulled gasifier power plant at Molodo.
Table 15. Gasification of rice husks, Indonesia
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Parameters |
Gasifier I |
Gasifier II | |||
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(a) Typical daily operation data | |||||
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Operating time |
18.00-24.00 |
18.00-24.00 | |||
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04.00-06.00 | |||
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Electricity generated (kVA)(kW) |
12(9.6) |
18(15) | |||
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Diesel fuel consumption (I/day): | | | |||
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100 per cent diesel fuel |
40 |
42 | ||
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dual-fuel operation |
12.0 |
12.6 | ||
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Lubricant oil consumption |
81/60 hr |
81/20 hr | |||
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Rice husk consumption (kg/hr) |
23.3 |
30.0 | |||
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Temperature of outlet gas (K) |
673 |
603 | |||
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Temperature or gas entering the engine (K) |
303 |
308 | |||
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Lower heating value of gas (kJ/m3) |
not measured |
4,300 | |||
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Filter cleaning |
once in 2 weeks |
once in 2 weeks | |||
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Tar in gas at gasifier outlet (g/m3) |
1.7 |
3.8 | |||
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Tar in gas after dry filter (g/m3) |
0.37 |
1.00 | |||
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(b) Parameters relevant to economic analysis |
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Diesel oil replacement (percentage) |
70 |
70 | |||
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Rice husk to electricity energy conversion factor (kg/kWh) |
2.4 |
2.0 | |||
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Lubricating oil cost (Rp/dm3) |
900 |
2,500 | |||
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Rice husk price (Rp/kg) |
7.5 |
7.5 | |||
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Electricity delivered price (Rp/10 W/month) |
2,000 |
1,000 | |||
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Transmitted electrical power (kW) Diesel oil price (on site) (Rp/dm3) |
4.5 250 |
5.0 250 | |||
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Operator salary (Rp/month) |
30,000 |
25,000 | |||
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(c) Economics of generating electricity using dual-fuel and full diesel | |||||
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Dual-fuel |
Full-diesel | |||
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Rupiahs |
Percentage |
Rupiahs |
Percentage | |
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Investment: |
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Gasifier |
5 000 000 |
27 | |
0 |
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Diesel engine |
13 000 000 |
70 |
13 000 000 |
96 |
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Building |
500000 |
3 |
500 000 |
4 |
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Installation |
200000 |
1 | |
0 |
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Total |
8700000 |
100 |
13 500 000 |
100 |
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Operating costs: |
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Labour |
306 000 |
7 |
180000 |
4 |
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Maintenance |
639 840 |
14 |
336 960 |
7 |
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Rice husk |
583 200 |
13 | |
0 |
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Diesel oil |
1 010 880 |
22 |
3 369 600 |
66 |
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Sub-total |
2 539 920 |
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3 886 560 |
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Depreciation |
1 962 500 |
44 |
1 187 500 |
23 | |
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Total expense |
4 502 420 |
100 |
5 074 060 |
100 |
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Production cost (Rp/kWh consum.) |
347 |
392 | |||
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Production cost (Rp/kWh gen) |
116 |
131 | |||
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Sales income (Rp) |
5 404 320 |
5 404 320 | |||
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Cash flow (Rp) |
2 864 400 |
1 517 760 | |||
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Economic variables: |
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Gasfier lifetime (years) |
8 |
8 | |||
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Engine lifetime (years) |
12 |
12 | |||
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Building lifetime (years) |
8 |
8 | |||
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Daily operating hours (hr/day) |
8 |
8 | |||
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Annual operating hours (hours) |
2 592 |
2 592 | |||
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Load level (kW) |
15 |
15 | |||
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Diesel consumption (1/hr) |
2 |
5 | |||
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Husk consumption (kg/hr) |
30 |
33 | |||
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Registered load (kW) |
5 |
5 | |||
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Electricity consumed (kWh/yr) |
12 960 |
12960 | |||
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Electricity generated (kWh/yr) |
38 880 |
38 880 | |||
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Diesel price (Rp/l) |
250 |
250 | |||
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Husk price (Rp/kg) |
8 |
- | |||
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Operator wage (Rp/hr) |
63 |
63 | |||
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Labour wage (Rp/hr) |
44 |
44 | |||
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Load factor |
1 |
1 | |||
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Electricity price (Rp/kWh) |
417 |
417 | |||
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Interest (percentage) |
12 |
12 | |||
Notes: $US1=Rp 1750Capital cost for a gasifier of 15 HP is $US 3000; the price of higher capacities is calculated by:
Capital cost (× HP) = Capital costs (15HP) * (x/15) (10×0.3)
Interest rate is 12 per cent per annum
Gasifier economic life is 7 years
Engine derating due to oil replacement is proportional to the percentage of oil replacement
Mechanical power to run a rice meal is 27 kW per ton of rice milled per hour 250 kg husk is produced per ton of rice, of which only 25 per cent is needed to power the mill
Source: Manning and Beenackrs, 1990.
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