A Study on Reverse Power Flow from Home Co-generation System

Transcription

1 Extended Summary pp A Study on Reverse Power Flow from Home Co-generation System Atsushi Minagata Student Member (Nagoya University, a minaga@nuee.nagoya-u.ac.jp) Takeyoshi Kato Member (Nagoya University, tkato@nuee.nagoya-u.ac.jp) Yasuo Suzuoki Member (Nagoya University, suzuoki@nuee.nagoya-u.ac.jp) Keywords: co-generation system, fuel cell, reverse power flow, surplus power, energy conservation This paper discusses reverse power flow from a home cogeneration system (H-CGS) in terms of energy conservation and influence on electric power systems. Data of actual electricity and hot-water demand observed in a family including 2 adults and 2 children for a year was used as a case study for H-CGS installed in a household with typical family composition. As operation patterns of H-CGS, No Reverse power flow with variable power output operation (NR operation) and Part-time Reverse power with variable and/or constant power output operation (PR operation) were assumed. In PR operation, considering the influence on electric power system, such as voltage rise, economic load dispatching, etc., the reverse power flow from H-CGS to the electric power system is not allowed during mid-night. Figure 1 shows the reduction in monthly primary energy consumption by H-CGS. If the reverse power flow is allowed with PR operation, the reduction in annual primary energy consumption can be increased by about 40% relative to that in NR operation. Figure 2 shows hourly reverse power flow patterns in February, May and August (monthly average). The reverse power flow is large during the daytime in winter-season, because the power output of H-CGS is large for meeting large hot-water demand. The reverse power flow in middle-season is about a half of that in winter, and it is quite small in summer season, suggesting very small contribution of H- CGS with reverse power flow operation as peak power generator in power system. Because the reverse power flow from H-CGS can contribute to the energy conservation, the discussion was conducted with Fulltime Reverse power with constant power output operation (FR operation), anticipating larger energy conservation with more flexible operation. However, the primary energy conservation in FR operation was almost same with that in PR operation, while the reverse power during mid-night was as large as that during daytime in FR operation. Taking the possible influence on electric power, the reverse power during mid-night may not be so attractive. Finally, the economic value of reverse power flow as a measure for reducing CO 2 emission was evaluated. The result shows the economic value of reverse power flow in PR operation corresponds to 23,000 yen/t-c. Fig. 1. Reduction in monthly primary energy consumption Fig. 2. Hourly reverse power flow in PR-operation (monthly average) 4

2 A Study on Reverse Power Flow from Home Co-generation System Atsushi Minagata, Student Member, Takeyoshi Kato, Member, Yasuo Suzuoki,Member This paper discusses reverse power flow from a home co-generation system (H-CGS) in terms of energy conservation and influence on electric power systems. Data of actual electricity and hot-water demand observed in a family including 2 adults and 2 children for a year was used as a case study for a typical installation. When the reverse power flow is allowed with the exception during mid-night, considering the influence on electric power system, the reduction in annual primary energy consumption can be increased by about 40% relative to that in the operation without reverse power. The reverse power flow is large during the daytime in winter-season, because the power output of H-CGS is large for meeting large hot-water demand. Even if the reverse power is allowed throughout a day, the primary energy conservation is almost same with that in part time reverse power operation, while the reverse power during mid-night is as large as that during daytime. Finally, the economic value of reverse power flow as a measure for reducing CO 2 emission was evaluated. The result shows the economic value of reverse power flow in PR operation corresponds to 23,000 yen/t-c. Keywords: co-generation system, fuel cell, reverse power flow, surplus power, energy conservation 1. 1kW H-CGS H-CGS H-CGS H-CGS 1kW H-CGS H-CGS H-CGS Dept. of Electrical Eng. and Computer Sci., Nagoya University Furo, Chikusa-ku, Nagoya H-CGS H-CGS H-CGS 1 H-CGS H-CGS H-CGS H-CGS H-CGS H-CGS H-CGS (1) (2) B

3 1kW H-CGS H-CGS 4 1 H-CGS H-CGS H-CGS (3) ,660 kwh 18.3 MJ 4 72% HHV 4,570 kwh 16.5 MJ (4) 4 NHK (5) 3. H-CGS 3 1 H-CGS NEDO (6) 35% LHV 40% LHV 1kW 0.3 kw 1.0 kw 1 50% H-CGS 36.5% HHV BB 72% HHV 80% 70 C 200 L P c H-CGS 14% 10% H-CGS 0.5% H-CGS P E P C P C = P E [kw] (1) 3 2 H-CGS 1 NR kW % kw H-CGS 0.3 kw 24 2 PR P E H ave 23 7 H P E = H ave H η E η H [kw] (2) η E η H H-CGS H-CGS 480 IEEJ Trans. PE, Vol.127, No.3, 2007

4 CGS (a) NR operation Fig Reduction in monthly primary energy consumption. (b) PR operation 1 H-CGS 2005/2/1 Fig. 1. An example of electricity supply pattern by H- CGS and grid (2005/2/1). a NR 0.3 kw 1.0 kw b PR 7 7 1kW H-CGS 80 90% H-CGS 50% PR kW H-CGS 1kW % HHV 72% HHV 71.3GJ 4 E conv H-CGS 2 H-CGS E CGS E grid E RP 0 BB H BB H-CGS E HHV ( ECGS E = E conv + E grid E RP + H ) BB (3) η CGS η grid η BB η CGS H-CGS η grid η BB NR kw 10% 2 PR NR PR % 4 B

5 GJ NR 64.0 GJ 10.3% PR 61.3 GJ 14.1% H-CGS 1.4 H-CGS H-CGS H-CGS 5. Fig Composition of primary energy consumption. Fig. 4. Fig Composition of electricity supply. 5 Composition of hot-water supply. NR PR ,500 kwh H-CGS NR 3,700 kwh 1,660 kwh H-CGS PR 4,500 kwh 1,000 kwh 1,720 kwh NR H-CGS H-CGS H-CGS 1kW H-CGS PR H-CGS PR H-CGS IEEJ Trans. PE, Vol.127, No.3, 2007

6 CGS 6 PR Fig. 6. Hourly reverse power flow in PR-operation (monthly average). 7 FR Fig. 7. Hourly reverse power flow in FR-operation (monthly average). 6 H-CGS H-CGS 5 2 H-CGS PR H-CGS H-CGS 4 1 FR % 90% 100% % FR 7 FR PR FR 8 Fig. 8. Annual reverse power flow. PR 2 FR 0.4 kw 0.1 kw PR FR 8 FR 37% PR 0.3 kw 0.3 kw FR PR 0.09 GJ 60.2 GJ 15.6% PR 1.5% FR 6 PR 7 FR % B

7 H-CGS H-CGS 1.5% 6. CO 2 H-CGS CO 2 H-CGS NR PR FR H-CGS CO2 H-CGS NR PR FR H-CGS (4) CO 2 H-CGS CO 2 V CO2 = C total {(P CGS BB CGS ) k gas (P buy +P RPF(7-23) ) k fired P RPF(23-7) k all } (4) C total P CGS BB CGS P buy P RPF(7-23) 7 23 P RPF(23-7) 23 7 k gas CO 2 [t-c/kwh] k fired CO 2 [t-c/kwh] k all CO 2 [t-c/kwh] NR 71 /m 3 21 /kwh (7) (8) PR FR 35 /m /kwh (9) 2.7 /kwh (10) CO g-c/nm 3 (11) 188 g-c/kwh 98 g-c/kwh (12) H-CGS PR 5,866 PR CO 2 91 kg-c CO 2 23,000 /t-c FR CO 2 CO 2 47,000 /t-c CO 2 60,000 /t-c (13) H-CGS CO H-CGS 1 H-CGS CO 2 23,000 /t-c 5 10% CO 2 H-CGS H-CGS H-CGS H-CGS 17 No IEEJ Trans. PE, Vol.127, No.3, 2007

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