Home-use fuel cell system

• US 7,091,625 B2
• Filed: 04/07/2004
• Issued: 08/15/2006
• Est. Priority Date: 10/11/2001
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Chino, Kouichi, Kahara, Toshiki, Okusawa, Tsutomu, Takahashi, Shin, Yokomizo, Osamu, Mizukami, Takaaki
• Primary Examiner(s): Schuberg, Darren
• Assistant Examiner(s): Cuevas, Pedro J.
• Application Number:
  US10/819,159
• Publication Number:
  US 20040212194A1
• Time in Patent Office: 860 Days
• Field of Search: 290/1.R, 290/44, 320/104, 320/116, 320/118, 320/136
• US Class Current: 290/1.00R
• 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 for supplying a base power portion as an output thereof; and

a power storage device having a capacitor and a secondary battery, said capacitor and said secondary battery each being electrically connected to said fuel cell to receive and be charged by a charging power portion of said fuel cell output equivalent to the difference between the base power portion and an actual current power demand of said home-use fuel cell system, when said actual current power demand is less than said base power portion;

wherein said capacitor and said secondary battery of said power storage device are connected to discharge a charge therein corresponding to a peak power portion of said actual current power demand equivalent to the difference between the base power portion and the actual current power demand of said home-use fuel cell system, when said actual current power demand is greater than said base power portion;

wherein, when the output of the fuel cell is represented by P [W], the capacity of the power storage device is represented by Q [Wh], and the discharqe depth of the power storage device is represented by x [%], the following relationships are satisfied;

250≦

P≦

1000; and

1000/x×

10≦

Q≦

2600/x×

10.

2. The home-use fuel cell system according to claim 1, wherein the following relationships are satisfied:

(0.0085P²−

7.2P+4600)/x×

10≦

Q≦

(0.0085×

P²−

7.2P+7080)/x×

10.

3. The home-use fuel cell system according to claim 1,

further comprising a protection mechanism for protecting the secondary battery so that the discharge depth thereof does not exceed a predetermined value;

wherein the protection mechanism comprises interrupting means for interrupting a charging operation or a discharging operation of the secondary battery in accordance with a voltage of the secondary battery.

4. The home-use fuel cell system according to claim 1, further comprising a natural force power-generating mechanism as an auxiliary power supply.