Abstract:
A system is provided to recover unutilized energy as electric power in hydraulic turbine power generation. The system includes a heat storage tank, a pump for pumping water from the heat storage tank and to air conditioning loads, a first water feed pipe connected between an outlet of the storage pump and the air conditioning loads, and a second water feed pipe for returning the water discharged from the air-conditioning loads. A hydraulic turbine driven generator is provided on a lower portion of the second water feed pipe at such a position as to recover the potential energy of the water discharged from the air conditioning loads.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the technique of recovering unutilized energy of water used, for example, in an air-conditioning load in a building, by a hydraulic turbine power generation or the like. 
     2. Related Art 
     As an air-conditioning system in a building, there has been extensively used a regenerative heat air-conditioning system in which a heat source machine is operated, utilizing inexpensive midnight power, and the produced heat is stored in a heat storage tank, and in the daytime when an air-conditioning load develops, the stored heat is pumped out, and is fed to an air-conditioner (load), thereby effecting the air-conditioning. 
       FIG. 16  is a schematic diagram of an open-loop regenerative heat air-conditioning system given as a reference example. 
     Referring to the construction of a primary system of the regenerative heat air-conditioning system of  FIG. 16 , reference numeral  16  denotes a water lift pump for pumping water from a heat storage tank  16  and for feeding the water to a heat source machine  4  via a water feed pipe  17 , reference numeral  2  an electric motor for driving the water lift pump  1 , reference numeral  17  the water feed pipe connecting the water lift pump  1  to the heat source machine  4 , reference numeral  3  a commercial power source, reference numeral  5  a two-way valve for adjusting the amount of heat produced by the heat source machine  4 , reference numeral  18  a water feed pipe for returning the water, discharged from the heat source machine  4 , to the heat storage tank  16 , and reference numeral  6  an expansion tank provided on the water feed pipe  18 . Reference numeral  29  denotes a float valve, reference numeral  25  a gate valve, and reference numeral  27  a check valve. 
     Referring to a secondary system of the regenerative heat air-conditioning system of  FIG. 16 , reference numeral  7  denotes a water lift pump for pumping water (heat) from the heat storage tank  16  and for feeding the water to a group of air-conditioning loads  10  (for example, a plurality of air-conditioning apparatuses such as an air handling unit  10   a  and a fan coil  10   b ) via a water feed pipe  19 , and reference numeral  8  a double-shaft electric motor which is directly connected at its one end to the water lift pump  7  through a coupling  14  to drive this water lift pump. The other end thereof is connected to a hydraulic turbine  9  via a clutch  13 . The hydraulic turbine  9  is located at such a position as to recover the potential energy of water discharged from the group of air-conditioning apparatuses  10 . Reference numeral  15  denotes a commercial power source (which may be the commercial source  3 ). Reference numeral  11  denotes a two-way valve for adjusting the load amount of the group of air-conditioning loads  10 , reference numeral  20  a water feed pipe for returning the pumping water, used in the group of air-conditioning apparatuses  10 , to the heat storage tank  16 , and reference numeral  12  an expansion tank which is provided on the water feed pipe  20 , and serves to destroy a siphoning effect so as to exert a head of the fed water (the potential energy of the fed water) on the hydraulic turbine. In some cases, instead of the expansion tank  12 , a vacuum breaker is used. Reference numeral  24  denotes a water feed pipe for returning the water, discharged from the hydraulic turbine  9 , to the heat storage tank  16 . Reference numeral  22  denotes a water feed pipe bypassing the hydraulic turbine  9 . Gate valves  21  to  23  are provided on these water feed pipes. Namely, the pumping water, fed to the group of air-conditioning apparatuses  10  by the water lift pump  7 , and is used there, and then is fed to the hydraulic turbine  9 . The hydraulic turbine  9  is operated by the potential energy of the pumping water to produce power, and transmits this power to the double-shaft electric motor  8 . A load of the double-shaft electric motor  8  is made smaller than a load of the water lift pump  7  by this amount. Then, the pumping water, discharged from the hydraulic turbine  9 , returns to the heat storage tank  16 . Reference numeral  26  denotes a gate valve, reference numeral  28  a check valve, and reference numeral  30  a float valve. 
       FIG. 17  is a diagram showing operation characteristics of the pump and hydraulic turbine of the reference example. H(m) at an upper portion of an ordinate axis of the diagram represents a total pump head in the case of the pump, and represents an effective head in the case of the hydraulic turbine. P(kw) at a lower portion of the ordinate axis of the diagram represents power for both. An abscissa axis of the diagram represents the water quantity Q. A curve A represents a Q-H performance curve of the pump, and a curve C represents a shaft power curve obtained when the hydraulic turbine is not operated. In the water feed system of  FIG. 16 , the total pump head H 0  is required for feeding the amount Q 0  of water by operating only the storage pump  7 , and an operating point at this time is a point O 4  on the curve A. Power, consumed at this time, is L 1  representing the pump shaft power, and an operating point is O 1  on the curve C. A curve B represents the effective head (the pressure head difference between the inlet and outlet sides of the hydraulic turbine) of the hydraulic turbine  9 , and it means that when the amount Q 0  of water is flowed, a pressure difference head (effective head) H 1  develops between the inlet and outlet sides of the hydraulic turbine  9 , and the hydraulic turbine absorbs this potential energy to produce power L 3  described below. 
     A curve D is a power curve obtained when the storage pump  7  and the hydraulic turbine  9  are operated. Power, produced by the hydraulic turbine  9  when the amount Q 0  of water flows, is L 3 . In this case, the power recovery (L 3 /L 1 ) is about 20% to about 30%. The operating point at this time is O 2  on the curve D, and the consumed power is reduced by L 3  relative to L 1 , and becomes L 2  representing the pump shaft power. Energy, corresponding to this power L 2 , is supplied as electric power from the commercial power source  15 . 
     In the case where a large amount of water flows into the hydraulic turbine, the plurality of apparatuses, described above, are operated in a parallel manner. 
     There has been proposed another reference example in which a similar system for recovering potential energy of pumping water, passed past a heat source machine, is provided also in a primary system of a regenerative heat air-conditioning system, and this system has been efficiently utilized. Namely, in  FIG. 16 , the electric motor  2  for driving the water lift pump  1  is modified into the double-shaft type, and the hydraulic turbine  9  is connected to that side of the electric motor  2 , which is not connected to the pump, and water, discharged from the heat source machine  4 , is received by the hydraulic turbine, and the hydraulic turbine is operated by this pressure head, and a torque, produced by the hydraulic turbine, is transmitted to the electric motor  2 , thereby reducing the load (the storage pump  1  in this case) of the electric motor  2 . Such conventional examples are disclosed, for example, in JP-A-50-128801 (power recovery pump apparatus) and JP-A-50-49701 (power recovery pump apparatus). A reference example of a hydraulic turbine power-generating system for generating electric power by a hydraulic turbine, provided in a water channel such as a dam and a paddy field, is disclosed in JP-A-5-10245 (outer ring-driving-type hydraulic turbine power-generating apparatus). 
     In the above reference techniques, however, the clutch is used for connecting the electric motor and the hydraulic turbine together, and a problem to be solved is to improve its transmission efficiency. And besides, there has been encountered another problem that the energy, recovered by the hydraulic turbine, is mechanical power, and therefore can not be used in other loads in a building because of the structure. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of this invention to recover unutilized energy as electric power by the hydraulic turbine power generation so as to reuse it. 
     It is not rational that such apparatuses are designed and produced individually in accordance with a height of a building (a pressure head of a hydraulic turbine) and an air-conditioning load (flow rate) in the building. Generally, a plurality of general-purpose apparatuses are beforehand prepared, and a required number of (plurality of) apparatuses are operated in a parallel manner in accordance with the building specification or the load facility specification. 
     Another object of the invention is to provide a method of serial operation and parallel operation of a plurality of hydraulic turbine power-generating apparatuses, in which a plurality of general-purpose hydraulic power-generating apparatuses are installed serially or in parallel in accordance with the specification of a facility (hydraulic turbine specification) such as a building, a dam and a river, and are operated at low costs, and also to provide a control apparatus for such method. 
     According to the present invention, there is provided an energy recovery apparatus comprising a heat storage tank provided at a lower portion of a building; a secondary system-side water lift pump for pumping water from the heat storage tank and for feeding it to a group of air-conditioning loads; a first water feed pipe provided between an outlet port of the storage pump and the air-conditioning load group; a second water feed pipe for returning the water, discharged from an outlet port of the air-conditioning load group, to the heat storage tank; an expansion tank or a vacuum breaker provided at an uppermost portion of the second water feed pipe; a hydraulic turbine, which is provided on a lower portion of the second water feed pipe, and is located at such a position as to recover the potential energy of the water discharged from the air-conditioning load group; a generator driven to be rotated by a torque of the hydraulic turbine to produce electric power; an inverter connected to an output terminal of the generator so as to produce DC power; and a system connecting device which receives the DC power from the inverter, and converts it into AC power, and supplies it to an electric motor for driving the secondary system-side storage pump. 
     The apparatus of the present invention has the above construction, and is operated as follows. 
     1) Before the operation, inlet and outlet valves of the hydraulic turbine and a hydraulic turbine-bypassing valve are closed. First, the secondary system-side storage pump is powered. 
     2) Next, an operation demand signal is fed from the air-conditioning load group to the storage pump. 
     3) Upon reception of the operation demand signal from the air-conditioning load group, the storage pump is operated, and at the same time it feeds an operation answer signal to the generator. 
     4) The inlet and outlet valves of the hydraulic turbine are opened a predetermined time after the operation answer signal is received. As a result, the hydraulic turbine and the inverter are operated. The rotational speed of the hydraulic turbine gradually increases, so that the generator begins to operation. 
     5) The generated electric power is supplied to the load (for example, the storage pump-driving electric motor and so on) via the inverter. 
     6) The inverter inputs the electric power, generated by the generator, thereinto, and converts it into AC power, and feed it to the system connecting device (regenerating converter). The system connecting device (regenerating converter) converts the DC power, inputted thereinto, into AC power, and feeds it back to the power source. 
     7) The expansion valve or the vacuum breaker is provided at the upper portion of the water feed pipe, and has a portion open to the atmosphere, or has an equivalent function, and prevents the expansion of the water, and discharges the air within the pipe or introduces the ambient air to break the vacuum so as to assist the fed water in falling to the hydraulic turbine. In another embodiment, a pressure sensor, provided in the vicinity of the hydraulic turbine, detects a pressure of this portion, and when this water pressure exceeds a predetermined value, the automatic valves, provided in the vicinity of the hydraulic turbine, are opened. 
     At the time of stopping the operation: 
     8) The inlet and outlet valves of the hydraulic turbine are closed, and the hydraulic turbine is stopped, and the inverter is stopped, and the system connecting device is stopped. 
     9) The supply of the generated power is stopped, and the supply of the power to the load, such as the secondary system-side storage pump-driving electric motor, is stopped. 
     10) A stop demand signal is fed from the generator to the secondary system-side storage pump. 
     11) The stop demand signal is received, and the secondary system-side storage pump-driving electric motor is stopped, and a stop answer signal is fed to the generator. 
     In the power system of the energy recovery apparatus having a plurality of loads, an inverter is provided at the output of the generator for recovering the unutilized energy, and a system connecting device is provided between the inverter and the power source so as to feed the generated power of the generator back to the power source so that the plurality of loads can use the generated power of the generator. Alternatively, a control apparatus for effecting such operation control is provided. 
     In the power system of the energy recovery apparatus having a plurality of loads, a plurality of inverters are provided at the outputs of the generators for recovering the unutilized energy, and a common system connecting device is provided between the plurality of inverters and the power source so as to feed the generated power of the generators back to the power source so that the plurality of loads can use the generated power of the generators. Alternatively, a control apparatus for effecting such operation control is provided. 
     According to another aspect of the invention, there is provided the following construction. 
     This energy recovery apparatus comprises a heat storage tank provided at a lower portion of a building; a secondary system-side storage pump for pumping water from the heat storage tank and for feeding it to a group of air-conditioning loads; a first water feed pipe provided between an outlet port of the storage pump and the air-conditioning load group; a second water feed pipe for returning the water, discharged from an outlet port of the air-conditioning load group, to the heat storage tank; an expansion tank or a vacuum breaker provided at an uppermost portion of the second water feed pipe; a hydraulic turbine generator, which is provided on a lower portion of the second water feed pipe, and is located at such a position as to recover the potential energy of the water discharged from the air-conditioning load group; an inverter connected to an output terminal of the hydraulic turbine generator so as to produce DC power; and a system connecting device which receives the DC power from the inverter, and coverts it into AC power, and supplies it to an electric motor for driving the secondary system-side storage pump, and a plurality of hydraulic turbine generators are provided, and are installed serially or in parallel, and this energy recovery apparatus is operated. 
     In this construction, when the plurality of hydraulic turbine generators are installed serially or in parallel, the installation is effected in the following. 
     A water quantity of a facility is Q, and a head thereof is H, and a water quantity of the hydraulic turbine power-generating apparatus is Q 0 , and an effective head thereof is H 0 , and the facility head H is divided by the effective head H 0  of the hydraulic turbine power-generating apparatus, thereby finding the quotient n, and if the remainder develops at this time, and the generation of electric power is possible with a head, corresponding to this remainder, n is defined as (n+1), and if the power generation is impossible, n is defined as n, so that the hydraulic turbine power-generating apparatuses whose number is n are installed serially. 
     Alternatively, a water quantity of a facility is Q, and a head thereof is H, and a water quantity of the hydraulic turbine power-generating apparatus is Q 0 , and an effective head thereof is H 0 , and the facility water quantity Q is divided by the water quantity Q 0  of the hydraulic turbine power-generating apparatus, thereby finding the quotient n, and if the remainder develops at this time, and the generation of electric power is possible with a water quantity, corresponding to this remainder, n is defined as (n+1), and if the power generation is impossible, n is defined as n, so that the hydraulic turbine power-generating apparatuses whose number is n are installed in parallel. 
     The energy recovery apparatus of the invention has this construction, and is operated as follows. 
     1) When the plurality of hydraulic turbine generators, connected serially or in parallel, are operated, these generators produce electric power in accordance with the points of use of them. 
     2) Each of the generator-side inverters converts the generated power of the generator into DC power, and feed back or supply the DC power to the system connecting device via a cable. 
     3) The system connecting device converts the DC power, fed back or supplied from each inverter, into AC power acceptable by the power source, and feeds it back to the power source. 
     For controlling the plurality of hydraulic turbine power-generating apparatuses, the inverters are provided for the plurality of hydraulic turbine power-generating apparatuses, respectively, and the system connecting device is provided at the power source-sides of the inverters, and a DC voltage terminal P of each inverter is connected to a DC voltage terminal P of the system connecting device while a DC voltage terminal N of each inverter is connected to a DC voltage terminal P of the system connecting device, and the control is effected so that the generated power can be fed back to the power source. Alternatively, a control apparatus for effecting such control is provided. 
     Alternatively, the plurality of hydraulic turbine power-generating apparatuses are located respectively at such positions as to recover the potential energy of the water discharged from the air-conditioning load group, and the plurality of inverters are provided for the plurality of hydraulic turbine power-generating apparatuses, respectively, and the system connecting device is provided at the power source-sides of the inverters, and a DC voltage terminal P of each inverter is connected to a DC voltage terminal P of the system connecting device while a DC voltage terminal N of each inverter is connected to a DC voltage terminal P of the system connecting device, and the control apparatus is so constructed that the generated power can be fed back to the power source. 
     The control apparatus has such a construction that the plurality of inverters and the system connecting device are contained in a common control panel. 
     Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing a first embodiment of the present invention. 
         FIG. 2  is a diagram showing operation characteristics of a pump and hydraulic turbine according to the first embodiment. 
         FIG. 3  is a view showing a second embodiment of the invention. 
         FIG. 4  is a view showing a third embodiment of the invention. 
         FIG. 5  is a view showing a fourth embodiment of the invention. 
         FIG. 6  is a schematic diagram of a portion of the fifth embodiment of the invention. 
         FIG. 7  is a schematic diagram showing the fifth embodiment of the invention. 
         FIG. 8  is a view showing one example of connection of various equipments according to the invention. 
         FIG. 9  is a flow chart showing the operation procedure and control procedure for a sixth embodiment of the invention. 
         FIG. 10  is a flow chart showing the operation procedure and control procedure for a seventh embodiment of the invention. 
         FIG. 11  is a view showing an eighth embodiment of the invention. 
         FIG. 12  is a circuit diagram explanatory of the control apparatus related to the schematic diagram of the eighth embodiment. 
         FIG. 13  is a diagram showing operation characteristics of the eighth embodiment of the invention. 
         FIG. 14  is a view showing a ninth embodiment of the invention. 
         FIG. 15  is a diagram showing operation characteristics of the ninth embodiment of the invention. 
         FIG. 16  is a view showing a regenerative heat air-conditioning system given as a reference example. 
         FIG. 17  is a diagram showing operation characteristics of a pump and hydraulic turbine of the regenerative air-conditioning system of the reference example. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of the present invention will now be described first with reference to  FIGS. 1 to 10 . 
       FIG. 1  is a diagram of a first embodiment of the present invention. A system of  FIG. 1  differs from the secondary system of the regenerative heat air-conditioning system of  FIG. 16  (showing the reference example) in that the double-shaft electric motor  8  is replaced by an ordinary electric motor  31  (non-double-shaft electric motor), so that a water lift pump  7  and a hydraulic turbine  9  are separated from each other, and a generator  34  is mounted on this hydraulic turbine  9  (which may be of the integral type containing such generator), and that an inverter  35  is connected to an output terminal of the generator  34 . A system connecting device  36  (regenerating converter device) is provided, and the inverter  35  and the system connecting device  36  are connected to the electric motor  31  via cables  40  and  41 , that is to say, to a point  33  between the electric motor  31  (for driving the storage pump  7 ) and a commercial power source  15  (which may be a commercial source  3 ). Further, a positive DC terminal P and a negative DC terminal N of the inverter  35  are connected respectively to a positive DC terminal P and a negative DC terminal N of the system connecting device  36  via respective cables  38  and  39 . Electric power, generated by the generator  34 , is converted into a direct current by the inverter  35 , and is converted into an alternating current by the system connecting device  36 , and is fed back to the commercial power source  15 . Reference numerals  32  and  37  denote electric energy meters, respectively. 
     When the hydraulic turbine  9  is not operated, the electric motor  31  for driving the water lift pump in the secondary system is supplied with electric power from the commercial power source  15 . When the electric power, generated by the generator  34 , is not sufficient during the operation of the hydraulic turbine  9 , this electric power and the electric power from the commercial power source  15  are used in combination. When the generated electric power is in surplus, the surplus electric power is fed back to the commercial power source  15  via the terminals P and N of the inverter  35  and further via the system connecting device  36 . 
     Identical reference numerals to those of  FIG. 16  denote identical equipments or devices, and therefore explanation thereof will be omitted.  FIG. 1  shows the secondary system, and the showing of a primary system is omitted. 
       FIG. 2  is a diagram showing operation characteristics of the pump and hydraulic turbine of the first embodiment of the invention. Identical reference characters to those of  FIG. 17  have identical meanings, and therefore explanation thereof is omitted. In the first embodiment of the invention, when a shaft power L 1 , required for flowing the amount Q 0  of water by the storage pump  7 , is to be obtained, generated power L 3 , regenerated via the hydraulic turbine  9 , the generator  34 , the inverter  35  and the system connecting device  36 , and electric power L 2  from the commercial power source are used to provide this shaft power L 1 . Naturally, when a two-way valve  11  is throttled, so that the load of the storage pump  7  is reduced, the driving power of the electric motor  31 , becomes, in some cases, smaller than the power produced by the hydraulic turbine  9 . In this case, power is fed back to the commercial power source  15  via a path (the hydraulic turbine  9 -the generator  34 -the inverter  35 -the system connecting device  36 -the commercial power source  15 ). In this embodiment, the power recovery (L 3 /L 1 ) is about 40% to about 60%, and is higher than the energy recovery of the conventional system. 
     A second embodiment of the invention will be described with reference to  FIG. 3 . Identical reference numerals to those of  FIGS. 1 and 16  have identical meanings, and therefore explanation thereof is omitted. In  FIG. 3 , only a secondary system is shown, and the showing of a primary system is omitted. This embodiment differs from the first embodiment in that regenerated power from a generator is applied not to a storage pump-driving electric motor  31  but to a group of air-conditioning apparatuses  10 . As shown in  FIG. 3 , an inverter  35  and a system connecting device  36  (regenerating converter device) are connected between the group of air-conditioning apparatuses  10  and a commercial power source  42  (which may be a commercial source  3 ,  15 ) via cables  40  and  41 . Further, DC terminals P and N of the inverter are connected respectively to DC terminals P and N of the system connecting device via respective cables  38  and  39 . 
     When a hydraulic turbine  9  is not operated, power is supplied from the commercial power source  42  to the group of air-conditioning apparatuses  10 . During the operation of the hydraulic turbine  9 , when electric power, generated by the generator  34 , is insufficient, depending on a load condition of the air-conditioning apparatus group  10 , this electric power and the electric power from the commercial power source  42  are used in combination. When the electric power, generated by the generator  34 , is in surplus, the surplus electric power is fed back to the commercial power source  42  via the terminals P and N of the inverter  35  and further via the system connecting device  36 . Reference numeral  43  denotes an electric energy meter. 
     A third embodiment of the invention will be described with reference to  FIG. 4 . Identical reference numerals to those of  FIGS. 1 ,  3  and  16  have identical meanings, and therefore explanation thereof is omitted. In  FIG. 4 , only a secondary system is shown, and the showing of a primary system is omitted. In this embodiment, electric power, generated by a hydraulic turbine  9 , is supplied to a group of loads such as illumination equipments in a building. In  FIG. 4 , reference numeral  46  denotes the group of loads such as illumination equipments in the building. Reference numeral  45  denotes power system switching means. When this power system switching means  45  is switched into such a condition that its contacts c and a are connected together, the load group  46  is connected to a commercial power source  44  (which may be a commercial power source  3 ,  15 ,  42 ). When this switching means is switched into such a condition that its contacts c and b are connected together, the load group  46  is connected to the generator  34 . Namely, during the operation of the hydraulic turbine  9 , when electric power, generated by the generator  34 , is sufficient for a load condition of the group of loads  46 , the contacts c and b of the power system switching means  45  are connected together so as to supply the electric power of the generator to the group of loads. When the generated electric power is insufficient, the power system switching means  45  is switched so as to connect the contacts c and a together, thereby supplying electric power of the commercial power source  44  to the group of loads  46 . 
     A fourth embodiment of the invention will be described with reference to  FIG. 5 . Identical reference numerals to those of  FIGS. 1 ,  3 ,  4  and  16  have identical meanings, and therefore explanation thereof is omitted. In  FIG. 5 , only a secondary system is shown, and the showing of a primary system is omitted. This embodiment is an improvement over the third embodiment. When a load amount of a group of loads  46  is so large that electric power, generated by a generator  34 , is insufficient, the electric power from the generator  34  and electric power from a commercial power source  47  (which may be a commercial source  3 ,  15 ,  42 ,  44 ) are used in combination. In  FIG. 5 , electric power can be applied to the group of loads  46  (as in  FIG. 4 ) from both of the generator  34  and the commercial power source  47 , and an inverter  35  is connected to the generator  34 , and a system connecting device  36  (which receives DC electric power from the inverter  35 , and coverts it into AC electric power, and feeds it back to the power source) is connected between the commercial power source  47  and the inverter  35 . DC terminals P and N of the system connecting device  36  are connected respectively to DC terminals P and N of the inverter  35  via respective cables  38  and  39 . In this construction, when electric power, generated by the generator  34 , is insufficient, this electric power and the electric power from the commercial power source  47  are supplied to the group of loads. 
     A fifth embodiment of the invention will be described with reference to  FIG. 6 . In this embodiment, the invention is applied to a primary system of a regenerative heat air-conditioning system. A hydraulic turbine  9  is provided on an intermediate portion of a water feed pipe  18 , and gate valves  21  and  23  are provided respectively at inlet and outlet sides of the hydraulic turbine  9 , and a bypass pipe  48  and a gate valve  49  are provided in bypassing relation to these. A pressure gauge  50  and a pressure sensor  51  are provided at the inlet side of the hydraulic turbine  9 , and a pressure gauge  52  and a pressure sensor  53  are provided at the outlet side of the hydraulic turbine  9 . When the maintenance of the hydraulic turbine  9 , generator  34  and their associated equipments is to be effected, the gate valves  21  and  23  are closed while the gate valve  49  is opened, so that the fed water, passed past a heat source machine  4 , is returned to a heat storage tank  16  sequentially via a hydraulic turbine-upstream side portion of the water feed pipe  18 , the bypass pipe  48 , the gate valve  49  and a hydraulic turbine-downstream side portion of the water feed pipe  18 . By doing so, the heat source machine  4  can be operated even when the maintenance of the hydraulic turbine  9 , generator  34  and their associated equipments is effected. Similarly, this arrangement can be applied to a secondary system, and in this case, a group of air-conditioning apparatuses  10  can be operated even when the maintenance of a hydraulic turbine  9 , generator  34  and their associated equipments is effected.  FIG. 7  is a schematic view showing this arrangement. In this Figure, the showing of pressure gauges, pressure sensors, an inverter, a system connecting device and so on is omitted. Sign “- 1 ”, added to reference numerals  9 ,  21 ,  23 ,  34 ,  48  and  49 , indicates that these devices and equipments are provided at the primary system, and sign “- 2 ”, added to these reference numerals, indicates that these devices and equipments are provided at the secondary system. 
       FIG. 8  is a power system diagram showing one example of connection of various equipments. Reference characters ELB 1  to ELB 7  denote earth leakage breakers, and reference numerals  54 - 2  to  54 - 6  and  55 - 2  to  55 - 6  denote magnet contacts each with a thermal breaker. Reference numeral  34 - 1  denotes a generator of a primary system, reference numeral  34 - 2  a generator of a secondary system, reference numeral  35 - 1  an inverter of the primary system, and reference numeral  35 - 2  an inverter of the secondary system. In  FIG. 8 , the generators and inverters are provided in two pairs as described for  FIG. 7 , and terminals P and N of each of the inverters are connected respectively to terminals P and N of a system connecting device  36 . Identical reference numerals to those of  FIGS. 1 to 7  and  16  have identical meanings, and therefore explanation thereof is omitted. 
     A sixth embodiment of the invention will be described with reference to  FIG. 9 . In this embodiment, the procedure of operation of control devices for a group of air-conditioning apparatuses  10 , a secondary system storage pump-driving electric motor  31 , a generator  34 , an inverter  35  and a load equipment (although these are not shown in the drawings), as well as a control procedure thereof, are provided, and these are operated in a coordinated manner.  FIG. 9  is a flow chart showing the operation procedure and the control procedure. Namely, for operating the system, an inlet valve of a hydraulic turbine is opened, and an outlet valve thereof is closed, and a hydraulic turbine-bypass valve is closed (Step  1 ). In Step  2 , power is supplied to the secondary system storage pump-operating electric motor  31 , and in Step  3 , an operation demand signal is fed from the air-conditioning apparatuses group  10  to a storage pump  7  of the secondary system. In Step  4 , the storage pump  7  of the secondary system receives the operation demand signal, and the secondary system storage pump-driving electric motor  31  is operated. Thereafter, an operation answer signal is fed to the generator  34 . In Step  5 , a predetermined time after this operation answer signal is received by the generator, the outlet valve of the hydraulic turbine is opened, and the hydraulic turbine is operated. As a result, the generator is operated to produce electric power. In Step  6 , the electric power, generated by the generator  34 , is supplied to the loads. Next, for stopping the operation, the outlet valve of the hydraulic turbine is closed, and the operation of the hydraulic turbine  9  is stopped (Step  7 ). As a result, the generator  34  is stopped. In Step  8 , the supply of the generated electric power is stopped, and the operation of the inverter  35  is stopped. Then, the supply of electric power to the loads is stopped. In Step  9 , a stop demand signal is fed from the generator  34  to the storage pump  7 , and the storage pump  7  is stopped. Then, a stop answer signal is fed to the generator  34 . In this embodiment, although the load of the generator  34  is the secondary system storage pump-driving electric motor  34 , this load may be the air-conditioning apparatus group  10  or a heat source machine  4 , and may be other load such as illumination equipments in the building. By thus providing the operation procedure and the control procedure, the equipments can be satisfactorily operated in a coordinated manner without any error so that they can perform their performances and functions. Although not shown in the drawings, the operation demand signal, the operation answer signal, the stop answer signal and so on are fed between the control devices for respectively controlling the air-conditioning apparatus group, the water lift pump, the storage pump-driving electric motor, the generator and so on. 
     A seventh embodiment of the invention will be described with reference to  FIG. 10 . This embodiment is an improvement over the sixth embodiment, and in this embodiment, an automatic coordinated operation is carried out. Therefore, gate valves  21 ,  23  and  49  (as in  FIG. 6 ) are formed into the automatic type. The procedure of operation of control devices for a heat source machine  4 , a primary system storage pump-driving electric motor  2 , a generator  34 - 1 , an inverter  35 - 1  and a load equipment (although these are not shown in the drawings), as well as a control procedure thereof, are provided, and these are automatically operated in a coordinated manner.  FIG. 10  is a flow chart showing the operation procedure and the control procedure. Namely, for operating the system, an inlet valve of a hydraulic turbine is opened, and an outlet valve thereof is closed, and a hydraulic turbine-bypass valve is closed (Step  1 ). In order that the automatic running and the automatic operation can be effected at the time of the operation of the system, Step  5 , in which inlet and outlet valves of a hydraulic turbine are opened when the inlet pressure of the hydraulic turbine exceeds a predetermined pressure, is added with respect to the procedure of  FIG. 9 , and by doing so, the hydraulic turbine  9 , the generator  34  and their associated equipments can be automatically operated. At the time of stopping the operation, the inlet and outlet valves of the hydraulic turbine are closed (Step  9 ), thereby automatically stopping the hydraulic turbine  9 , the generator  34  and the associated equipments. The other operations are the same as in  FIG. 9 , and therefore explanation thereof is omitted here. By doing so, the erroneous operation is eliminated, and the control of the operation is easier. 
     As a further improved embodiment, conditions for the opening of the inlet and outlet valves of the hydraulic turbine are that a heat source machine is operated and that the inlet pressure of the hydraulic turbine is above a predetermined value, and when these conditions are satisfied, the control for the valve opening is effected. By doing so, the operation can be carried out more positively, and the overall system can be operated in a coordinated manner. 
     Next, further embodiments of the invention will be described with reference to  FIGS. 11 to 15 . 
       FIG. 11  is a schematic diagram of an eighth embodiment (serial operation) of the invention. This Figure indicates how many hydraulic turbine power-generating apparatuses should be serially installed and how these apparatuses should be arranged. In this embodiment, there is used an ordinary electric motor  202  (non-double-shaft electric motor) which corresponds to the double-shaft electric motor of  FIG. 16  in the regenerative heat air-conditioning system of the reference example having the energy recovery system incorporated in its primary system, and a storage pump and hydraulic turbines are separated from each other. Here, a water quantity of a facility specification is Q 0 , and a head thereof is H, and the other hand a water quantity of a hydraulic turbine specification is Q 0 , and an effective head thereof is H 0 . Namely, when the head H of the facility is divided by the effective head H 0 , n=2 (the remainder: a) is obtained. This is shown in  FIG. 11 . As will be hereinafter more fully described in  FIG. 13 , a hydraulic turbine effective head a (the remainder a) is not enough to cause a generator to generate a required amount of electric energy, and therefore the number of hydraulic turbines to be installed is two, and the two hydraulic turbines are serially connected. Generators  234 - 1  and  234 - 2  are mounted respectively on these hydraulic turbines  209 - 1  and  209 - 2  (each of which may be of the integral type containing such generator), and inverters  235 - 1  (INV 1 ) and  235 - 2  (INV 2 ) are connected respectively to output terminals of the generators  234 - 1  and  2342  as shown in  FIG. 12  which will be described later. Terminals P and N (DC output terminals) of a DC intermediate circuit of these inverters are connected respectively to terminals P and N of a DC circuit portion of a system connecting device (regenerating converter)  236  which is a higher-level device than these inverters, and is provided between a commercial power source  203  (PW) and these inverters. Here, P and N mean DC voltage, and a positive DC voltage is P, and a negative DC voltage is N. Electric power, produced by the generator  234 - 1 ,  234 - 2 , flows, as regenerating current, via a flywheel diode D of the inverter  235 - 1 ,  235 - 2 , and is stored in a capacitor C (For example, if the generated voltage of the generator is AC 200V, the inverter P-N voltage (DC voltage) is 280V.). When the amount of water, flowing into the hydraulic turbine  209 - 1 ,  209 - 2  varies, so that the amount of electric power, generated by the generator  234 - 1 ,  234 - 2 , changes, for example, the above P-N voltage is detected, and each time this voltage goes below 280V, the inverter frequency is lowered by a PWM processing (although not shown in the drawings), and by doing so the regeneration is damped, so that the P-N voltage increases. 
     Further, the DC voltage terminals N of the inverters  235 - 1  and  235 - 2  and the terminal N of the system connecting device (regenerating converter)  236  are connected together by a cable  238 , while the DC voltage terminals P of these inverter and the terminal P of the system connecting device  236  are connected together by a cable  239  (see  FIG. 12 ). By doing so, the generated electric power is fed as DC power to the system connecting device (the terminals P and N of the regenerating converter  236 ), and then is fed back to the commercial power source  203 . 
       FIG. 12  is a circuit diagram explanatory of the control apparatus related to the schematic diagram of  FIG. 11 . Similar reference numerals to those of  FIG. 16  denote identical equipments or devices, and therefore explanation thereof will be omitted. In this Figure, reference numeral  203  (PW) denotes the commercial source, reference numeral  232 (WH 1 ) an electric energy meter for measuring the amount of electric power to be purchased from an electric power company, and reference numeral  243  (WH 2 ) an electric energy meter for measuring the amount of electric power to be sold to the electric power company. Reference characters ELB 1  to ELB 3  denote leakage breakers, respectively. Reference numeral  255 N denotes an electromagnetic switch for a heat source machine, reference numeral  255 P an electromagnetic switch for the storage pump, reference numeral  254 N a thermal relay for the heat source machine, reference numeral  254 P a thermal relay for the storage pump, and reference numeral  236  the system connecting device (regenerating converter) which is used for converting the regenerating energy, produced at the load side, into AC electric power (which is acceptable by the power source) and for feeding it back to the power source. Reference numeral  235 - 1  (INV 1 ) denotes the No.  1  generator-side inverter, reference numeral  235 - 2  (INV 2 ) the No.  2  generator-side inverter, reference numeral  234 - 1  (G 1 ) the No.  1  generator, and reference numeral  234 - 2  (G 2 ) the No.  2  generator. The load-side terminals P and N of the system connecting device  236  are disposed at a higher lever than the No.  1  and No.  2  generator-side inverters  235 - 1  and  235 - 2 , and the load-side terminal P is connected to the DC voltage terminals P of these inverters while the load-side terminal N is connected to the DC voltage terminals N of these inverters. Namely, electric powers, generated respectively by the No.  1  and No.  2  generators, are converted into DC power by the respective inverters, and the system connecting device  236  coverts this DC power into AC power (acceptable by the power source), and feeds it back to the commercial source  203 . 
     At first, since the hydraulic turbines  209 - 1  and  209 - 2  and the generators  234 - 1  and  234 - 2  are not operated, electric power is not supplied from the DC voltage terminals P and N of the inverters  235 - 1  and  235 - 2 , and the water lift pump  201 , the electric motor  202  and a group of loads, including a heat source machine  204 , are operated only by electric power supplied from the commercial source  203 . When the storage pump  201  is operated, water is fed to the heat source machine  204 , and when the used water is returned to the hydraulic turbines  209 - 1  and  209 - 2 , the hydraulic turbines  209 - 1  and  209 - 2  and the generators  234 - 1  and  234 - 2  are operated, and DC power is supplied from each of the inverters  235 - 1  and  235 - 2  to the DC voltage terminals P and N of the system connecting device  236  via the cable  238 ,  239 . The system connecting device  236  converts the DC power into the predetermined AC power, and feeds it back to the commercial source  203 . Then, the electric energy meter  243  (WH 2 ) measures the amount of the electric power to be fed back to the power source. 
       FIG. 13  is a diagram showing operation characteristics of the water lift pump and hydraulic turbines of the eighth embodiment of the invention. Identical reference characters to those of  FIG. 17  have identical meanings, and therefore explanation thereof is omitted. In  FIG. 13 , the water lift pump is operated with the water quantity Q 0  and the total pump head H 3 . With respect to the specification of the hydraulic turbine, the water quantity is Q 0 , and the effective head is H 0 , and a curve F represents this characteristics. Namely, when the water quantity Q 0  and the effective head H 0  are provided for the hydraulic turbine, the hydraulic turbine produces power S 0 . This characteristics are represented by a curve G. When two hydraulic turbines, connected serially, are operated, the effective head is 2H 0 , and a curve E represents this characteristics. When the two hydraulic turbines, serially connected, are operated, the produced power is 2 S 0 , and a curve I represents this characteristics. In this case, the remainder a of the head H of the facility develops as shown in the drawings. When this is indicated on the curve F representing the effective head characteristics obtained at the time of operation of one hydraulic turbine, this is a point Oa representing the water quantity Qa. At this point, the water quantity is so small that the hydraulic turbine will not produce power. This indicates that the number of hydraulic turbines to be installed should be two as shown in this embodiment. 
       FIG. 14  is a schematic diagram of a ninth embodiment (parallel operation) of the invention. This Figure indicates how many hydraulic turbine power-generating apparatuses should be installed in parallel and how these apparatuses should be arranged. In this embodiment, there is used an ordinary electric motor  202  (non-double-shaft electric motor) which corresponds to the double-shaft electric motor of  FIG. 16  in the regenerative heat air-conditioning system of the reference example having the energy recovery system incorporated in its primary system, and a water lift pump and hydraulic turbines are separated from each other. Here, a water quantity of a facility specification is Q, and a head thereof is H 0 , and the other hand a water quantity of a hydraulic turbine specification is Q 0 , and an effective head thereof is H 0 . Namely, when the water quantity Q of the facility is divided by the water quantity Q 0  of the hydraulic turbine specification, n=2 (the remainder: b) is obtained. This is shown in  FIG. 15 . As will be hereinafter more fully described in  FIG. 15 , a water quantity b (the remainder b) of the hydraulic turbine specification is not enough to cause a generator to generate electric power, and therefore the number of hydraulic turbines to be installed is two, and the two hydraulic turbines are connected in parallel. 
       FIG. 15  is a diagram showing operation characteristics of the storage pump and hydraulic turbines of the ninth embodiment of the invention. Identical reference characters to those of  FIG. 17  have identical meanings, and therefore explanation thereof is omitted. In  FIG. 15 , the water lift pump is operated with the water quantity Q 0  and the total pump head H 3 . With respect to the specification of the hydraulic turbine, the water quantity is Q 0 , and the effective head is H 0 , and a curve F represents this characteristics (Q-H). A curve J represents the combined characteristics obtained when the two hydraulic turbines, connected in parallel, are operated. Namely, when the water quantity Q 0  and the effective head H 0  are provided for the hydraulic turbine, the hydraulic turbine produces power S 0 . This characteristics are represented by a curve G. When two hydraulic turbines, connected in parallel, are operated, the water quantity is 2Q 0 , and the effective head is H 0 . This characteristics are represented by a curve G′ with a starting point Q 0 , which is obtained by parallel translation of the curve G. When the curves G and G′ are combined together, there is obtained a curve I with a starting point O 2 , which represents the combined characteristics. This indicates that power, produced when the two hydraulic turbines are operated in parallel, is 2S 0  at a point O 1 . In this case, the remainder b of the water quantity Q of the facility develops as shown in the drawings. When this is indicated on the curve F representing the effective head characteristics obtained at the time of operation of one hydraulic turbine, this is a point Ob representing the water quantity Qb. At this point, the water quantity is so small that the hydraulic turbine will not produce power. This indicates that the number of hydraulic turbines to be installed should be two as shown in this embodiment. 
     In the above embodiments, the electric power, produced by the plurality of generators, is fed as DC power to the system connecting device, in which the power is converted into AC power, and then is fed back to the power source. Therefore, the amount of consumption of electric power can be reduced, and besides any load can be used, and this system can meet with any loads. Furthermore, whether the plurality of hydraulic turbine power-generating apparatuses are installed serially or in parallel, the common control apparatus can be used without the need for changing it. 
     The terminals P of the DC circuits of the inverter and system connecting device, as well as the terminals N of these DC circuits, are connected together by the cable, and when these cables are long, a wiring loss increases. The inverter and the system connecting device can be contained collectively in the same control panel. With this arrangement, the improvement can be achieved. 
     In the above embodiments, although the present invention is applied to the primary system of the regenerative heat air-conditioning system, the invention can be similarly applied to the secondary system. 
     In the above embodiments of the invention, a plurality of general-purpose standardized hydraulic turbine power-generating apparatuses are beforehand prepared for various facility specifications, and the requirement for any facility specification can be met by installing these apparatuses serially or in parallel. Therefore, the time and labor, required for the design, are saved, and the production cost is low, and the installation period is short. 
     As described above, in the present invention, the higher recovery efficiency can be achieved as compared with the conventional unutilized-energy-recovering apparatus employing the hydraulic turbine. And besides, the invention can meet the various loads, and therefore for example, unutilized energy in a building can be reused. 
     It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.