Home-use fuel cell system

• US 20040212194A1
• Filed: 04/07/2004
• Published: 10/28/2004
• Est. Priority Date: 10/11/2001
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Okusawa, Tsutomu, Takahashi, Shin, Yokomizo, Osamu, Mizukami, Takaaki, Chino, Kouichi, Kahara, Toshiki
• Granted Patent: US 7,091,625 B2
• Time in Patent Office: Days
• US Class Current: 290/1R
• CPC Class Codes: H01M 16/006 of fuel cells with rechargeable batteries
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 3/32 using batteries with converting means
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: Y02B 10/30 Wind power
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

During a time zone where a power demand is smaller than an average value of the entire power demands of homes, an excess portion obtained by subtracting a power demand from a base power portion supplied by PEFC (1) is charged in a capacitor (7) and a lead storage battery (8) in advance; and during a time zone where a power demand is larger than the average value, a peak power portion exceeding this average value is discharged from the capacitor (7) and the lead storage battery (8); thereby enabling the system to sufficiently meet daily home-use demand with requisite minimum equipment while effectively using surplus power. Thus, energy efficiency can be enhanced without wasting energy, and also cost efficiency can be improved.

Claims

1. A home-use fuel cell system for supplying power for power demands of a home, the home-use fuel cell system comprising:

a fuel cell (1) for supplying a base power portion except a short-time peak power portion out of the power demands;

a power storage device (7, 8) having a capacitor (7) and a secondary battery (8), for performing a discharge corresponding to the peak power portion; and

a protection mechanism (11, 12, 15, 18;

20, 21) for protecting the secondary battery (8) so that the discharge depth thereof does not exceed a predetermined value.

2. The home-use fuel cell system according to claim 1, wherein, when the output of the fuel cell (1) is represented by P [W], the capacity of the power storage device (7, 8) is represented by Q [Wh], and the discharge depth of the power storage device (7, 8) is represented by x [%], the following relationships are satisfied:

250≦

P≦

1000 1000/x×

10≦

Q≦

2600/x×

10.

3. The home-use fuel cell system according to claim 2, wherein the following relationships are satisfied:

(0.0085P²−

7.2P+4600)/x×

10≦

Q≦

(0.0085×

P²−

7.2P+7080)/x×

10.

4. The home-use fuel cell system according to claim 12, wherein the protection mechanism (11, 12, 15, 18;

20, 21) comprises interrupting means (18) for interrupting a charging operation or a discharging operation of the secondary battery (8) in accordance with a voltage of the secondary battery.

5. The home-use fuel cell system according to any one of claims 1, 2, 3 and 4, further comprising a natural force power-generating mechanism (27) as an auxiliary power supply.