Field of the Invention
The present invention relates to an energy management
system which manages electric power generated by an electric
power generation apparatus for generating electric power
using natural energy and electric power supplied to loads,
i.e., electric appliances, and a power feed control device
which is used by the energy management system.
Background of the Invention
Conventionally, there is known a system which supplies
electric power generated by solar cells to the electric
appliances first and sell the surplus electric power of the
generated electric power to an electric power company. A
price advantage obtained by selling the surplus electric
power has acted as an incentive to introduce solar cells.
From the viewpoint of the price advantage and the reduction
of CO2 (saving of CO2) , it is expected that the price of
electric power to be sold rises in the future, so that the
introduction of solar cells will be promoted. The price
advantage is greatly affected by the price of power to be
sold which is set over time by an electric power company.
As a conventional system to which solar cells are
introduced, Japanese Patent Application Publication No.
2008-158701 (JP2008-158701A) discloses a system for

supplying information which is useful for selecting an
appropriate electricity rate design from various types of
price designs supplied by an electric power company. The
system disclosed in JP2008-158701A provides useful
information to select the appropriate electricity rate
design by collecting information about the amounts of
electric power generated by solar cells, the amounts of
electric power consumption of electric appliances, and the
amounts of electric power transacted with an electric power
company and selecting the appropriate price design.
Furthermore, Japanese Patent Application Publication
No. 2002-369381 discloses a system for minimizing loss
resulting from the difference in price over time when the
surplus self-generated electric power is sold. Japanese
Patent Application Publication No. 2005-287211 discloses a
system for operating a cogeneration apparatus which drives
an electric power generation apparatus using a gas engine in
order to reduce the price obtained from calculation based on
the time-based prices of electric power to be sold to an
electric power company and the time-based prices of electric
power to be purchased from the electric power company.
Moreover, conventional systems to which solar cells
are introduced include a system provided with an electric
power storage device which is used to store electric power
generated by solar cells. According to this system, it is
possible to determine whether to sell electric power,

generated by solar cells, to an electric power company or to
store the electric power in the electric power storage
device. That is, the system can select the destination of
the electric power generated by the solar cells.
Summary of the Invention
However, the system to which the solar cells and the
electric power storage device are introduced is requested to
produce a greater price advantage by automatically
controlling a destination of the electric power, generated
by the solar cells, in response to the price of electric
power to be sold, which is changed over time.
The system disclosed in JP2008-158701A provides
information to be used by users to select an appropriate
electricity rate design from a plurality of predetermined
electricity rate designs. However, the above system is not
provided with means for automatically determining a
destination to which the electric power generated by the
solar cells is supplied in order to actually maximize the
price advantage.
Further, although the system disclosed in JP2002-
369381A can effectively change a time span in which electric
power is sold, the system is not provided with means for
automatically determining a destination to which electric
power generated by the solar cells is supplied. That is,

the system cannot determine whether to sell or store the
electric power generated by the solar cells.
Furthermore, the cogeneration apparatus can be
operated to reduce a cost by controlling the supply of
gaseous fuel as in the system disclosed in JP2005-287211A.
However, the electric power, generated by the solar cells
which generate electric power using solar energy, cannot be
adjusted.
As described above, the conventional systems cannot
automatically determine the destination to which the
generated electric power is supplied such that the price
advantage is maximized in the state in which the electric
power generation apparatus for generating electric power
using natural energy and the energy storage device for
storing the generated electric power are introduced.
In view of above, the present invention provides an
energy management system which can improve cost
effectiveness when using electric power generated by an
electric power generation apparatus for generating electric
power using natural energy, and a power feed control device
which is used by the energy management system.
In accordance with one aspect of the present invention,
there is provided an energy management system for managing
electric power generated by an electric power generation
apparatus for generating the electric power by using natural
energy and electric power to be supplied to an electric

appliance as a load, the energy management system including:
a controller for determining one of destinations to which
surplus electric power of the generated electric power is
supplied; and a storage unit storing one or more rules
regarding use of electric power that is set with a priority
order of candidates of the destinations to which the surplus
electric power is supplied; wherein the controller
determines the destination based on the rules stored in the
storage unit, and information about a price of electric
power to be sold.
Further, it is preferred that the energy management
system may further include a path switching unit for
supplying the electric power generated by the electric power
generation apparatus to the electric appliance and switching
the destination to which the surplus electric power is
supplied; and an information acquisition unit for acquiring
the information about the price of electric power to be sold
to an electric power company, wherein the candidates include
the electric power company to which the surplus electric
power is sold, and an energy storage device which is capable
of storing energy corresponding to the surplus electric
power, wherein the priority order of candidates in the rules
is set corresponding to the price of electric power to be
sold, and wherein the controller determines the priority
order by referring to the information about the price of
electric power to be sold, and controls the path switching

unit such that the destination, to which the surplus
electric power is supplied, is sequentially switched
according to the priority order of the candidates.
With such configuration, when the price of electric
power to be sold is changed, the priority order of the
candidates of the plurality of destinations of the surplus
electric power of the electric power generation apparatus is
determined using the information about the price of electric
power to be sold and the rules regarding the use of electric
power, and the surplus electric power is sequentially
supplied to the destination in the order of the candidates
of the destinations having higher priorities, so that the
price performance can be improved when the electric power
generated by the electric power generation apparatus is used.
Furthermore, the energy storage device is included in
the destinations, so that the priorities of electric power
sale and electric power storage can be selected based on the
information about the price of electric power to be sold,
thereby more effectively using the electric power generated
by the electric power generation apparatus.
Preferably, the information acquisition unit may
acquire information about a price of electric power to be
purchased from the electric power company as well as the
information about the price of electric power to be sold,
the priority order of candidates in the rules is set
corresponding to the price of electric power to be sold and

the price of electric power to be purchased, and the
controller determines the priority order by referring to the
information about the price of electric power to be sold and
the information about the price of electric power to be
purchased.
Therefore, the controller can determine the priority
of each of the plurality of destinations using the
information about the price of electric power to be sold, so
that the cost effectiveness can be improved.
Preferably, the energy management system may further
include a computation unit for calculating a balance of an
electricity price by using a load pattern indicative of a
temporal change in electric power that is supplied to the
electric appliance, an electric power generation pattern
indicative of a temporal change in electric power that is
generated by the electric power generation apparatus, and
the information about the price of electric power to be sold
and the information about the price of electric power to be
purchased, wherein the priority order of candidates in the
rules is set by using a result obtained from the computation
unit.
Therefore, the balance of the electricity price is
calculated when the rules regarding the use of electric
power are set, so that the effective rules regarding the use
of electric power can be accurately set.
Preferably, the energy storage device may include an

electric power storage device for storing the surplus
electric power, and a heat storage device for storing heat
corresponding to the surplus electric power.
With such configuration, the electric power storage
and the heat storage can be selected as means for storing
the surplus electric power of the solar cells, so that it is
possible to change a criteria for determining whether to
store the surplus electric power or heat corresponding to
the surplus electric power depending on, for example,
temperature in the rules regarding the use of electric power.
Preferably, a time span in which the energy storage
device is used may be set; and the controller may determine
the priority order of candidates in the rules by referring
to the information about the price of electric power to be
purchased during the time span.
Further, when settings are made such that the energy
storage device is operated (stored energy is consumed using
the energy storage device) during a specific time span (for
example, during the night), the value of the generation of
electric power using the electric power generation apparatus
is evaluated during the specific time span, so that the cost
effectiveness can be accurately evaluated.
Preferably, the energy management system may further
include a selection unit for selecting one of the rules,
wherein the storage unit stores the rules being set
differently, and wherein the selection unit selects one of

the rules stored in the storage unit based on predetermined
conditions.
Therefore, one of the rules regarding the use of
electric power can be selected, so that a user can select
appropriate rules regarding the use of electric power
depending on the situation.
Preferably, one of the rules may be set such that the
energy storage device has a higher priority order than that
of the electric power company in terms of the priority order
of candidates.
With such configuration, the rules regarding the use
of electric power prescribing that the energy storage device
has priority over the electric power company are stored, so
that the rules regarding the use of electric power can be
selected based on the desires of the user, thereby actively
supplying as much electric power generated by the electric
power generation apparatus using natural energy to the
electric appliance is possible by storing the generated
electric power in the energy storage device. In the case of
the electric power generated using natural energy, an amount
of Co2 generated from any one of a primary energy
consumption source group is almost 0, so that the electric
power generated by the electric power generation apparatus
is sold as little as possible and is consumed, thereby
reducing the burden upon the environment.
In accordance with another aspect of the present

invention, there is provided a power feed control device for
use in the energy management system of the one aspect of the
present invention, including: the controller; the
information acquisition unit; and the storage unit.
Brief Description of the Drawings
The object and features of the present invention will
be apparent from the following description of embodiments
when taken in conjunction with the accompanying drawings, in
which:
Fig. 1 is a block diagram illustrating the
configuration of a first embodiment;
Fig. 2 is a view illustrating the patterns of the
priority order of destinations;
Fig. 3 is a view illustrating a load pattern and an
electric power generation pattern for a day;
Fig. 4 is a flowchart illustrating the operation of a
related energy management system;
Fig. 5 is a view illustrating a decision line that is
used to determine whether to sell or store the surplus
electric power of solar cells in the energy management
system;
Figs. 6A and 6B are views illustrating decision lines
that are used to determine whether to store the surplus
electric power of the solar cells or to store heat

corresponding to the surplus electric power in the energy
management system, wherein Fig. 6A is a view illustrating
the characteristics of respective seasons in the same region,
and Fig. 6B is a view illustrating the characteristics of
respective regions in the same season;
Fig. 7A is a view illustrating a case where a price of
electric power to be sold is ¥25/kWh, and Fig. 7B is a view
illustrating a case where the price of electric power to be
sold is ¥40/kWh in the relationships between a price of
electric power to be purchased and an annual heating and
lighting price in the energy management system shown in Fig.
6;
Fig. 8 is a view illustrating the patterns of the
priority order of destinations in accordance with a second
embodiment; and
Fig. 9 is a flowchart illustrating the operation of a
related energy management system.
Detailed Description of the Preferred Embodiments
Embodiments of the present invention will be described
in detail below with reference to the accompanying drawings
that constitute a part hereof. The same reference numerals
will be assigned to the same or similar components
throughout the drawings, and redundant descriptions thereof
will be omitted.

(First Embodiment)
An energy management system 1 in accordance with a
first embodiment manages electric power generated by solar
cells PV and electric power supplied to a load, i.e., an
electric appliance L1 which is provided in a facility H, as
shown in Fig. 1. The solar cells PV are an electric power
generation apparatus for generating electric power using
solar energy, which is natural energy. The energy
management system 1 includes an electric power distribution
board 2, a power feed control device 3, a first setting
manipulation unit 4, and a second setting manipulation unit
5. In Fig. 1, thick arrows indicate the flows of electric
power supply, thin arrows indicate the flows of signals, and
a dotted arrow indicates the flow of thermal supply.
In the present invention, the electric power
generation apparatus refers to solar cells which generate
electric power using solar energy and a wind power
generation apparatus which generates electric power using
wind energy. Furthermore, an energy storage device in
accordance with the present invention refers to an electric
power storage device which stores surplus electric power or
a heat storage device which stores thermal energy
corresponding to the surplus electric power.
In the present embodiment, the electric power
distribution board 2 supplies electric power supplied from
an electric power company AC or electric power generated by

the solar cells PV to the electric appliance L1, and, at the
same time, changes a destination to which the surplus
electric power of the generated electric power is supplied
and provides the surplus electric power to the destination.
The electric power distribution board 2 corresponds to a
path switching unit of the present invention. Furthermore,
direct current (DC)/alternating current (AC) conversion is
appropriately performed on the electric power which is
supplied from the solar cells PV to the electric appliance
L1 or the destination.
The destination includes the electric power company AC
to which the surplus electric power is sold, the electric
power storage device (storage battery) SB which stores the
surplus electric power, and the heat storage device HP which
stores thermal energy corresponding to the surplus electric
power. The electric power storage device SB can supply
electric power to the electric appliance L1 via the electric
power distribution board 2. In the electric power storage
device SB, the upper and lower limits of an electric power
storage rate and electric power storage speed (for example,
1kW/h) are set and charge and discharge losses occur. The
heat storage device HP operates hot-water supply load
equipment L2 by providing thermal energy to the hot-water
supply load equipment L2. In the heat storage device HP,
the upper and lower limits of a heat storage rate are
previously set and heat discharge loss occurs. In each of

the electric power storage device SB and the heat storage
device HP, a main time span for use is set. In the present
embodiment, settings are made such that the electric power
storage device SB is mainly used during the daytime and the
heat storage device HP is mainly used during the nighttime.
The electric power storage device SB and the heat storage
device HP correspond to the energy storage device of the
present invention.
The power feed control device 3 includes an
information acquisition unit 31, an information transmission
unit 32, a load information acquisition unit 33, a storage
unit 34, a computation unit 35, a controller (destination
derivation unit) 36, and a destination setting unit 37.
The information acquisition unit 31 has a function of
receiving information from a center server S over a network
N. The information acquisition unit 31 receives and
acquires information about the price of electric power to be
sold to the electric power company AC, and information about
the price of electric power to be purchased from the
electric power company AC from the center server S in real
time. Furthermore, the information acquisition unit 31 can
acquire the information about the price of electric power to
be sold and the information about the price of electric
power to be purchased in such a way that a user manipulates
the setting of the first setting manipulation unit 4.
Therefore, even when the information acquisition unit 31 is

not connected to the center server S, the information
acquisition unit 31 can acquire the information about the
price of electric power to be sold and information about the
price of electric power to be purchased.
The information transmission unit 32 has a function of
transmitting information to the center server S via the
network N. The information transmission unit 32 transmits
information, received from the second setting manipulation
unit 5 which is manipulated by the user, to the center
server S. The information includes regional information
(electric power company information) or an electric power
contract form.
The load information acquisition unit 33 acquires the
load information of the electric appliance L1 and the hot-
water supply load equipment L2.
The storage unit 34 stores the information about the
price of electric power to be sold and the information about
the price of electric power to be purchased which are
acquired by the information acquisition unit 31, and stores
rules regarding the use of electric power. In the rules
regarding the use of electric power, the priority order of
the plurality of destinations (the electric power company AC,
the electric power storage device SB, and the heat storage
device HP) of the surplus electric power of the solar cells
PV is set in conjunction with the price of electric power to
be sold and the price of electric power to be purchased.

The priority order of the plurality of destinations includes
six control patterns (first to sixth control patterns), as
shown in Fig. 2. For example, in the first control pattern,
first priory is given to electric power sale and the surplus
electric power of the solar cells PV is sold to the electric
power company AC. When all of the surplus electric power
cannot be sold to the electric power company AC, subsequent
priority is given to electric power storage and the surplus
electric power is stored in the electric power storage
device SB. Thereafter, when the surplus electric power is
still left over, priority is given to heat storage and heat
corresponding to the surplus electric power is stored in the
heat storage device HP.
In the rules regarding the use of electric power, the
priority order of the plurality of destinations is set based
on the results of calculation performed by the computation
unit 35. The computation unit 35 calculates the balance of
an electricity price using a load pattern indicative of the
temporal change of the load electric power of the electric
appliance L1, an electric power generation pattern
indicative of the temporal change of the electric power
generated by the solar cells PV, the information about the
price of electric power to be sold, and the information
about the price of electric power to be purchased, which are
acquired by the information acquisition unit 31.
Furthermore, the load pattern and the electric power

generation pattern are stored in the storage unit 34 in
advance.
Fig. 3 illustrates a load pattern WL and an electric
power generation pattern WPV which are stored in the storage
unit 34. First, the balance of the electricity price is
expressed by Equation 1 when the surplus electric power of
electric power generated by the solar cells PV, which is
left behind after the electric power has been supplied to
the load equipment, is not stored in the electric power
storage device SB and all of the surplus electric power is
sold to the electric power company AC. Furthermore, the
balance of the electricity price is expressed by Equation 2
when heat corresponding to the surplus electric power of the
solar cells PV is not stored in the heat storage device HP
and all of the surplus electric power is sold to the
electric power company AC:
(Wsell + WSB) ×CSeI- (Wpur,d×dpur,Cl + Wpur,n×dpur,n) (1)
(Wsel2 + WHP)×csel-(Wpur,d×dpur,d+ Wpur,n×dpur,n) (2)
where "csel" is the price of electric power to be sold,
"dpUr.d" is the electric power sale price during the day,
"dpUr.n" is the electric power sale price during the night,
"Wsell" is electric power obtained by excluding the amount of
electric power supplied to the electric power storage device
SB from the surplus electric power of the solar cells PV
when electric power is stored, "Wsel2" is electric power
obtained by excluding the amount of electric power supplied

to the heat storage device HP from the surplus electric
power of the solar cells PV when heat is stored, "WSB" is
the amount of electric power supplied to the electric power
storage device when electric power is stored, "WHp" is the
amount of electric power supplied to the heat storage device
when heat is stored, "Wpur.d" is the amount of electric power
to be sold during the day, and "Wpur.n" is the amount of
electric power to be sold during the night.
Meanwhile, when priority is given to store the surplus
electric power in the electric power storage device SB and
some of the surplus electric power is left after performing
the electric power storage, the balance of the electricity
price is expressed by Equation 3. Furthermore, when
priority is given to store the heat to the heat storage
device HP and some of the surplus electric power is left
after performing the heat storage, the balance of the
electricity price is expressed by Equation 4:

where is the efficiency of the electric power storage
device SB (including electric power charge efficiency and
electric power discharge efficiency), and is the
efficiency of the heat storage device HP (including heat
radiation efficiency).
Here, when a case where a priority is given to the
electric power sale is compared with a case where a priority

is given to the electric power storage (in this case, the
case that the priority is given to the electric power sale
refers to the case where all of the electric power is sold
without being stored as in Equation 1; the same hereinafter),
Equation 1 is compared with Equation 3. When a value
obtained using Equation 1 is greater than a value obtained
using Equation 3, the case where the priority is given to
the electric power sale is more economical than the case
where the priority is given to the electric power storage.
When the value obtained using Equation 1 is less than the
value obtained using Equation 3, the case where the priority
is given to the electric power storage is more economical
than the case where the priority is given to the electric
power sale.
Equation 1 - Equation 3

According to Equation 5, if it is assumed that the
efficiency of the electric power storage device SB is
almost constant, the priority order of the electric power
sale and the electric power storage is determined by the
price of electric power to be sold "csel" and the price of
electric power to be purchased during the day "dpur,d".
When a case where a priority is given to the electric
power sale is compared with a case where a priority is given

to a heat storage (in this case, the case where the priority
is given to the electric power sale refers to the case where
entire electric power is sold without being stored, as in
F.quation 2; the same hereinafter), Equation 2 is compared
with Equation 4. When a value obtained using Equation 2 is
greater than a value obtained using Equation 4, the case
where the priority is given to the electric power sale is
more economical than the case where the priority is given to
the heat storage. When the value obtained using Equation 2
is less than the value obtained using Equation 4, the case
where the priority is given to the heat storage is more
economical than the case where the priority is given to the
electric power sale.
Equation 2 - Equation 4

According to Equation 6, if it is assumed that the
efficiency of the heat storage device HP is almost
constant, the priority order of the electric power sale and
the heat storage is determined by the price of electric
power to be sold "csel" and the price of electric power to be
purchased during the night
When the case where a priority is given to the
electric power storage is compared with the case where a
priority is given to the heat storage, Equation 3 is

compared with Equation 4. When the value obtained using
Equation 3 is greater than the value obtained using Equation
4, the case where the priority is given to the electric
power storage is more economical than the case where the
priority is given to the heat storage. When the value
obtained using Equation 3 is less than the value obtained
using Equation 4, the case where the priority is given to
the heat storage is more economical than the case where the
priority is given to the electric power storage.
Equation 3 - Equation 4

In Equation 7, the priority order of the electric
power storage and the heat storage cannot be determined by
only the price of electric power to be sold "csel" and the
prices of electric power to be purchased "dpur,d" and "dpur,n",
but is changed based on the amounts of electric power to be
sold "Wsell" and "Wse12" the amount of electric power to be
supplied to the electric power storage device "WSB", and the
amount of electric power to be supplied to the heat storage
device "WHp".
The rules regarding the use of electric power in
accordance with the present embodiment are set such that the
case where the priority is given to the electric power sale
is compared with the case where the priority is given to the

heat storage using Equation 6 first, the case where the
priority is given to the electric power sale is compared
with the case where the priority is given to the electric
power storage priority using Equation 5 subsequently, and
then the case where the priority is given to the electric
power storage is compared with the case where the priority
is given to the heat storage using Equation 7 finally.
The controller 36 shown in Fig. 1 controls the
electric power distribution board 2 such that the electric
power generated by the solar cells PV is supplied to the
electric appliance L1 first. The controller 36, which
performed the above-described control, selects a destination,
to which the surplus electric power of the solar cells PV is
supplied, from a plurality of destination candidates. The
plurality of destination candidates are the electric power
company AC, the electric power storage device SB, and the
heat storage device HP. The controller 36 refers to the
rules regarding the use of electric power for the
information about the price of electric power to be sold and
the information about the price of electric power to be
purchased, which are acquired by the information acquisition
unit 31, and then determines the priority order of the
plurality of destinations. The controller 36, which
determined the priority order, controls the electric power
distribution board 2 such that the surplus electric power is
sequentially provided to a corresponding destination

according to the determined priority order. Information
about destinations determined by the controller 36 is
transmitted to the electric power distribution board 2 by
the destination setting unit 37.
Next, the operation of the energy management system 1
in accordance with the present embodiment will be described
with reference to Fig. 4. First, when the information
acquisition unit 31 of the power feed control device 3
acquires new information about the price of electric power
to be sold or new information about the price of electric
power to be purchased (at step S1 in Fig. 4), the controller
36 refers to rules regarding the use of electric power for
the information about the price of electric power to be sold
and the information about the price of electric power to be
purchased, and then determines the priority order of the
plurality of destinations (the electric power company AC,
the electric power storage device SB, and the heat storage
device HP) . Here, first, the controller 36 compares the
price advantage of the case where the priority is given to
the electric power sale with the price advantage of the case
where the priority is given to the heat storage (at step S2).
When the price advantage of the case where the priority is
given to the electric power sale is greater than the price
advantage of the case where the priority is given to the
heat storage, the price advantage of the case where the
priority is given to the electric power storage is compared

with the price advantage of the case where the priority is
given to the electric power sale (at step S3) . When the
price advantage of the case where the priority is given to
the electric power storage is greater than the price
advantage of the case where the priority is given to the
electric power sale, the controller 36 sets the control
pattern of the surplus electric power of the solar cells PV
as the third control pattern (see Fig. 2). When the price
advantage of the case where the priority is given to the
electric power storage is less than the price advantage of
the case where the priority is given to the electric power
sale, the price advantage of the case where the priority is
given to the electric power storage is compared with the
price advantage of the case where the priority is given to
the heat storage (at step S4). When the price advantage of
the case where the priority is given to the electric power
storage is greater than the price advantage of the case
where the priority is given to the heat storage, the
controller 36 sets the control pattern of the surplus
electric power of the solar cells PV as the first control
pattern (see Fig. 2). When the price advantage of the case
where the priority is given to the electric power storage is
less than the price advantage of the case where the priority
is given to the heat storage, the controller 36 sets the
control pattern of the surplus electric power of the solar
cells PV as the second control pattern (see Fig. 2).

Meanwhile, when the price advantage of the case where
the priority is given to the electric power sale is less
than the price advantage of the case where the priority is
given to the heat storage at step S2, the price advantage of
the case where the priority is given to the electric power
sale is compared with the price advantage of the case where
the priority is given to the electric power storage (at step
35) . When the price advantage of the case where the
priority is given to the electric power sale is greater than
the price advantage of the case where the priority is given
to the electric power storage, the controller 36 sets the
control pattern of the surplus electric power of the solar
cells PV as the fifth control pattern (refer to Fig. 2) .
When the price advantage of the case where the priority is
given to the electric power sale is less than the price
advantage of the case where the priority is given to the
electric power storage, the price advantage of the case
where the priority is given to the electric power storage is
compared with the price advantage of the case where the
priority is given to the heat storage (at step S6) . When
the price advantage of the case where the priority is given
to the electric power storage is greater than the price
advantage of the case where the priority is given to the
heat storage, the controller 36 sets the control pattern of
the surplus electric power of the solar cells PV as the
fourth control pattern (see Fig. 2). When the price

advantage of the case where the priority is given to the
electric power storage is less than the price advantage of
the case where the priority is given to the heat storage,
the controller 36 sets the control pattern of the surplus
electric power of the solar cells PV as the sixth control
pattern (see Fig. 2) .
Fig. 5 illustrates an example of a decision line that
is used to determine whether to sell or store the surplus
electric power of the solar cells PV. When the decision
line shown in Fig. 5 is used and if the price of electric
power to be purchased is ¥25/kWh, the controller 36 selects
the electric power sale even in the case where the price of
electric power to be sold is ¥25/kWh or ¥40/kWh. Meanwhile,
if the price of electric power to be purchased is ¥35/kWh,
the controller 36 selects the electric power sale in the
case where the price of electric power to be sold is ¥40/kWh.
However, if the price of electric power to be sold is
¥25/kWh, the controller 36 does not select the electric
power sale.
Figs. 6A and 6B illustrate examples of decision lines
that are used to determine whether to store the surplus
electric power of the solar cells PV or store heat
corresponding to the surplus electric power. Fig. 6A
illustrates the characteristics of the respective seasons in
the same region. In Fig. 6A, "A" is the decision line of
summer, "B" is the decision line of an intermediate period

(spring or fall), and "C" is the decision line of winter.
According to Fig. 6A, the decision lines are changed
seasonally. Fig. 6B illustrates the characteristics of the
respective regions in the same season (winter in the example
of the drawing) . In Fig. 6B, "A" is the decision line of
the hottest region, "B" is the decision line of the
intermediate region, and "C" is the decision line of the
coldest region. According to Fig. 6B, the decision lines
arc changed depending on regions. In the above-description,
the energy management system 1 in accordance with the
present embodiment can change the decision lines depending
on the temperature.
Furthermore, Figs. 7A and 7B illustrate the
relationships of the price of electric power to be purchased
and the annual heating and lighting price in the cases where
the priorities are given to the electric power sale, the
electric power storage and the heat storage for a specific
region. In Figs. 7A and 7B, "A" is the characteristic in
the case where the priority is given to the electric power
sale, "B" is the characteristic in the case where the
priority is given to the electric power storage, and "C" is
the characteristic in the case where the priority is given
to the heat storage. Fig. 7A shows the case where the price
of electric power to be sold is ¥25/kWh, and Fig. 7B shows
the case where the price of electric power to be sold is
¥40/kWh. In Figs. 7A and 7B, the annual heating and

lighting price of the case where the priority is given to
the electric power sale is cheaper than that of the case
where the priority is given to the heat storage regardless
of the price of electric power to be sold and the price of
electric power to be purchased. The reason for this is that
the heat storage device HP is a load leveling device and the
price of electric power to be purchased "dpur,n" is cheap
during the time span in which the heat storage device HP is
mainly operated (night).
As described above, in accordance with the present
embodiment, when the price of electric power to be sold
(information about the price of electric power to be sold)
or the price of electric power to be purchased (information
about the price of electric power to be purchased) is
changed, the priority order of the plurality of destination
candidates (the electric power company AC, the electric
power storage device SB, and the heat storage device HP) of
the surplus electric power of the solar cells PV is
determined using the information about the price of electric
power to be sold, the information about the price of
electric power to be purchased, and the rules regarding the
use of electric power. Further, the surplus electric power
is sequentially provided to a corresponding destination
candidate according to the priority order, so that cost
effectiveness can be achieved with respect to the use of the
electric power generated by the solar cells PV.

Furthermore, in accordance with the present embodiment,
the electric power storage device SB and the heat storage
device HP (energy storage devices) are included in the
aestinations. Therefore, the priority between selling the
surplus electric power and purchasing the surplus electric
power can be selected based on electric power sale and
purchase price information, so that the electric power
generated by the solar cells PV can be more effectively used.
Furthermore, in accordance with the present embodiment,
when the rules regarding the use of electric power are set
up, each balance of the electricity prices in the cases
where the priority is given to the electric power sale, the
electric power storage, and the heat storage, respectively,
is calculated, so that the effective rules regarding the use
cf electric power can be set up accurately.
Furthermore, in accordance with the present embodiment,
it is possible to set the electric power storage and the
heat storage as means for storing the surplus electric power
of the solar cells PV. Thus, in the rules regarding the use
of electric power, the criteria for determining whether to
store the surplus electric power as an electric power or a
heat can be changed depending on the temperature.
Furthermore, in accordance with the present embodiment,
when settings are made such that each of the electric power
storage device SB and the heat storage device HP is operated
(the electric power storage device SB and the heat storage

device HP consume stored energy) during a specific time span,
the value of the generation of the electric power of the
solar cells PV is evaluated for the specific time span, so
that the cost effectiveness can be evaluated accurately.
(Second embodiment)
An energy management system 1 in accordance with a
second embodiment is different from the energy management
system 1 in accordance with the first embodiment in that the
energy management system 1 stores a plurality of rules
regarding the use of electric power. Furthermore, the
configuration of the system in accordance with the present
embodiment is the same as the configuration of the system in
accordance with the first embodiment.
The storage unit 34 in accordance with the present
embodiment stores rules regarding the use of electric power
(hereinafter referred to as "first rules regarding the use
of electric power") as in the first embodiment, and also
stores rules regarding the use of electric power
(hereinafter referred to as "second rules regarding the use
of electric power") in which the settings thereof are
different from those of the first rules.
Settings are made such that the second rules regarding
the use of electric power include three control patterns.
Firstly, the case where the priority is given to the
electric power storage is compared with the case where the
priority is given to the electric power sale. Thereafter,

the case where the priority is given to the electric power
storage is compared with the case where the priority is
given to the heat storage, as shown in Fig. 8.
The controller 36 in accordance with the present
embodiment has a selection function of selecting rules
regarding the use of electric power, which are applied when
determining the priority order of a plurality of
destinations. The controller 36 selects rules regarding the
use of electric power, which are applied when the priority
order is determined, from a plurality of sets of rules
regarding the use of electric power (first and second rules
regarding the use of electric power) stored in the storage
unit 34 based on predetermined conditions. The
predetermined conditions include, for example, a condition
regarding whether the price of electric power to be
purchased is cheaper than the price of electric power to be
sold. For example, when the price of electric power to be
purchased during the night is cheaper than the price of
electric power to be sold, as in a home electrification
contract, the second rules regarding the use of electric
power are used. The controller 36 in accordance with the
present embodiment corresponds to the controller and
selection unit of the present invention.
Next, an operation that is performed when the second
rule regarding the use of electric power is used in the
energy management system 1 in accordance with the present

embodiment will be described with reference to Fig. 9.
First, when the information acquisition unit 31 of the power
feed control device 3 acquires new information about the
price of electric power to be sold or new information about
the price of electric power to be purchased (at step Sll of
Fig. 9), the controller 36 refers to the second rule
regarding the use of electric power for the information
about the price of electric power to be sold and information
about the price of electric power to be purchased, and then
determines the priority order of the plurality of
destinations (the electric power company AC, the electric
power storage device SB, and heat storage device HP). Here,
first, the price advantage of the electric power storage
priority is compared with the price advantage of the
electric power sale priority (at step S12). When the price
advantage of the case where the priority is given to the
electric power storage is greater than the price advantage
of the case where the priority is given to the electric
power sale, the controller 36 sets the control pattern of
the surplus electric power of the solar cells PV as the
third control pattern (see Fig. 8). When the price
advantage of the case where the priority is given to the
electric power storage is less than the price advantage of
the case where the priority is given to the electric power
sale, the price advantage of the case where the priority is
given to the electric power storage is compared with the

price advantage of the case where the priority is given to
the heat storage (at step S13) .
When the price advantage of the case where the
priority is given to the electric power storage is greater
than the price advantage of the case where the priority is
given to the heat storage, the controller 36 sets the
control pattern of the surplus electric power of the solar
cells PV as the first control pattern (see Fig. 8). When
the price advantage of the case where the priority is given
to the electric power storage is less than the price
advantage of the case where the priority is given to the
heat storage, the controller 36 sets the control pattern of
the surplus electric power of the solar cells PV as the
second control pattern (see Fig. 8).
Hereinbefore, in accordance with the present
embodiment, it is possible to select one from the plurality
of sets of rules regarding the use of electric power (first
and second rules regarding the use of electric power), so
that a user can select appropriate rules regarding the use
of electric power depending on the situation.
(Third embodiment)
An energy management system 1 in accordance with a
third embodiment is different from the energy management
system 1 in accordance with the second embodiment in that
the energy management system 1 stores third rules regarding
the use of electric power with the priority on environment,

together with the first and second rules regarding the use
of electric power. Furthermore, the configuration of the
system in accordance with the present embodiment is the same
as the configuration of the system in accordance with the
second embodiment.
The third rules regarding the use of electric power
are set up such that electric power storage to the electric
power storage device SB and heat storage to the heat storage
device HP always have priority over the electric power sale
to the electric power company AC. The third rules regarding
the use of electric power are stored in the storage unit 34,
together with the first and second rules regarding the use
of electric power.
The controller 36 in accordance with the present
embodiment selects a rule, which is applied when the
priority order of the destination is determined, from the
plurality of sets of rules regarding the use of electric
power (the first to third rules regarding the use of
electric power) which have been stored in the storage unit
34 according to a user's intention. For example, when the
user has high environmental awareness, the third rule
regarding the use of electric power is selected by the user
through the first setting manipulation unit 4.
As described above, in accordance with the present
embodiment, the third rule regarding the use of electric
power in which the priorities of the electric power storage

device SB and the heat storage device HP are always higher
than the electric power company AC is further stored. Thus,
it is possible to select a rule from the first and second
rules with the priority on cost effectiveness and the third
rules with the priority on the environment according to the
user's intention. When the third rule is selected, the
energy management system 1 in accordance with the present
embodiment can supply the electric power generated by the
solar cells PV to the electric appliance L1 within the
facility H as actively as possible by storing electric power
in the electric power storage device SB or storing heat in
the heat storage device HP. In the case of electric power
generation using solar energy, an amount of CO2 generated
from any one of a primary energy consumption source group is
almost 0. Therefore, in accordance with the present
embodiment, the electric power generated by the solar cells
PV is sold as little as possible and is consumed, thus
reducing the burden upon the environment.
Furthermore, as a modification of the third embodiment,
when the price of electric power to be sold is cheaper than
a preset reference price, the third rules regarding the use
of electric power may be set up such that the electric power
storage to the electric power storage device SB and the heat
storage to the heat storage device HP always have priority
over the electric power sale to the electric power company
AC. That is, when the third rule regarding the use of

electric power in accordance with the modification is used,
the energy management system 1 can determine the destination
of the electric power generated by the solar cells PV such
that environmental priority is realized when the price of
electric power to be sold is cheap and that price priority
is realized when the price of electric power to be sold is
high.
Furthermore, as modifications of the first to third
embodiments, the controller 36 may determine the priority
order of a plurality of destinations using only information
about the price of electric power to be sold without using
the information about the price of electric power to be
purchased. In the case of this modification, the priority
of the electric power company AC becomes high when the price
of electric power to be sold is high with respect to a
specific index, and the priority of the electric power
company AC becomes low when the price of electric power to
be sold is low with respect to the specific index.
Furthermore, although the case where the electric
power generation apparatus, which generates electric power
using natural energy, corresponds to the solar cells PV has
been described in the first to third embodiments, the
electric power generation apparatus is not necessarily the
solar cells PV and may be an apparatus which generates
electric power using natural energy when the present
invention is put to practical use. In the above description,

the electric power generation apparatus may be, for example,
a wind power generation apparatus which generates electric
power using wind energy in the modification of the first to
third embodiments. Even when the above-described apparatus
is used as the electric power generation apparatus, this
case does not cause any problem when practicing the present
invention, and achieves the same efficiency as the first to
third embodiments.
Furthermore, although the case where the electric
power storage device SB and the heat storage device HP are
used together as the energy storage device has been
described in the first to third embodiments, it is not
necessary to use the electric power storage device SB and
the heat storage device HP together as the energy storage
devices when the present invention is practiced. In the
above description, any one of the electric power storage
device SB and the heat storage device HP can be used as the
energy storage device in a modification of the first and
second embodiments. This modification does not cause any
problem when practicing the present invention, and achieves
the same efficiency as the first to third embodiments.
Moreover, in a modification of the first to third
embodiments, the power feed control device 3 may not include
the computation unit 35 and may store the rules regarding
the use of electric power, which are previously set by
another device based on simulation using Equations 1 to 7,

in the storage unit 34.
While the invention has been shown and described with
respect to the embodiments, the present invention is not
limited thereto. It will be understood by those skilled in
the art that various changes and modifications may be made
without departing from the scope of the invention as defined
in the following claims.

WE CLAIM:
1. An energy management system for managing electric
power generated by an electric power generation apparatus
for generating the electric power by using natural energy
and electric power to be supplied to an electric appliance
as a load, the energy management system comprising:
a controller for determining one of destinations to
which surplus electric power of the generated electric power
is supplied; and
a storage unit storing one or more rules regarding use
of electric power that is set with a priority order of
candidates of the -destinations to which the surplus electric
power is supplied;
wherein the controller determines the destination
based on the rules stored in the storage unit, and
information about a price of electric power to be sold.
2. The energy management system of claim 1, further
comprising:
a path switching unit for supplying the electric power
generated by the electric power generation apparatus to the
electric appliance and switching the destination to which
the surplus electric power is supplied; and
an information acquisition unit for acquiring the
information about the price of electric power to be sold to

an electric power company,
wherein the candidates include the electric power
company to which the surplus electric power is sold, and an
energy storage device which is capable of storing energy
corresponding to the surplus electric power,
wherein the priority order of candidates in the rules
i s set corresponding to the price of electric power to be
sold, and
wherein the controller determines the priority order
by referring to the information about the price of electric
power to be sold, and controls the path switching unit such
that the destination, to which the surplus electric power is
supplied, is sequentially switched according to the priority
order of the candidates.
3. The energy management system of claim 2, wherein:
the information acquisition unit acquires information
about a price of electric power to be purchased from the
electric power company as well as the information about the
price of electric power to be sold,
the priority order of candidates in the rules is set
corresponding to the price of electric power to be sold and
the price of electric power to be purchased, and
the controller determines the priority order by
referring to the information about the price of electric
power to be sold and the information about the price of

electric power to be purchased.
4. The energy management system of claim 3, further
comprising:
a computation unit for calculating a balance of an
electricity price by using a load pattern indicative of a
temporal change in electric power that is supplied to the
electric appliance, an electric power generation pattern
indicative of a temporal change in electric power that is
generated by the electric power generation apparatus, and
the information about the price of electric power to be sold
and the information about the price of electric power to be
purchased,
wherein the priority order of candidates in the rules
is set by using a result obtained from the computation unit.
5. The energy management system of any one of claims 2 to
4, wherein the energy storage device includes an electric
power storage device for storing the surplus electric power,
and a heat storage device for storing heat corresponding to
the surplus electric power.
6. The energy management system of any one of claims 3 to
5, wherein:
a time span in which the energy storage device is used
is set; and

the controller determines the priority order of
candidates in the rules by referring to the information
about the price of electric power to be purchased during the
time span.
7 . The energy management system of any one of claims 2 to
6, further comprising a selection unit for selecting one of
the rules,
wherein the storage unit stores the rules being set
differently, and
wherein the selection unit selects one of the rules
stored in the storage unit based on predetermined conditions.
8. The energy management system of claim 7, wherein one
of the rules is set such that the energy storage device has
a higher priority order than that of the electric power
company in terms of the priority order of candidates.
9. A power feed control device for use in the energy
management system of any one of claims 2 to 8, comprising:
the controller;
the information acquisition unit; and
the storage unit.

ABSTRACT

An energy management system for managing electric
power generated by an electric power generation apparatus
for generating the electric power by using natural energy
and electric power to be supplied to an electric appliance
as a load, the energy management system includes a
controller for determining one of destinations to which
surplus electric power of the generated electric power is
supplied; and a storage unit storing one or more rules
regarding use of electric power that is set with a priority
order of candidates of the destinations to which the surplus
electric power is supplied. The controller determines the
destination based on the rules stored in the storage unit,
and information about a price of electric power to be sold.