This study evaluated three types of combustion type CO
2 fertilization systems: The thermal storage type (excess heat energy is stored and used for heating), the heat waste type (excess heat is discharged outdoors), and the diffusion type (excess heat is discharged indoors). We analyzed the validity, energy-conserving, environmental load-reducing, and cost-reducing characteristics of these types, and reached the following conclusions.
1)The excess heat generated by combustion type CO
2 fertilization accounted for several percentages of the daily cumulative solar irradiation during the intermediate period under the standard condition in this study (amount of CO
2 fertilization,48 g (CO
2) m
-2d
-1). The thermal storage type is expected to prevent the aggravation of the thermal/humidity environment in the greenhouse and decrease the efficiency of supplied CO
2.
2)Using the thermal storage type,a maximal energy conservation of 8% and a reduction in CO
2 discharge can be expected in large greenhouses (annual energy consumption in the entire greenhouse, about 3 GWh) under the standard conditions of this study (summer/intermediate period ratio, 0.33; thermal storage/discharge efficiency, 0.8).
3)The unit cost of CO
2 fertilization using this thermal storage type was about 25 yen kg
-1 (during depreciation) and about 12 yen kg
-1 (after depreciation) under the standard conditions of this study (summer/intermediate period ratio, 0.33; price of unit quantity of heat, 5.5 yen kWh
-1; thermal storage/discharge efficiency, 0.8). To reduce the unit cost of CO
2fertilization, improvement in thermal storage/discharge efficiency, a decrease in fuel cost, and an increase in the number of days in operation during the intermediate period are necessary.
抄録全体を表示