WO2014170800A1

WO2014170800A1 - Solar power system

Info

Publication number: WO2014170800A1
Application number: PCT/IB2014/060599
Authority: WO
Inventors: Lei Feng; Hong Chen; Shiquan Wang
Original assignee: Koninklijke Philips N.V.
Priority date: 2013-04-19
Filing date: 2014-04-10
Publication date: 2014-10-23

Abstract

The invention relates to a solar power system (1) like a solar lighting system comprising a rechargeable battery (4), a conversion unit (3) like a solar panel for converting sunlight into electrical power for charging the battery (4), a load (5) like a lighting device to be powered by the battery (4), a shading determination unit (9) for determining a shading status of the conversion unit and a control unit (8) for controlling the charging of the battery (4) and/or the powering of the load (5) depending on the determined shading status of the conversion unit. Considering the shading status allows for an optimized control such that the lifetime of the battery can be increased. The control unit preferentially uses further information like the charge status of the battery and information about the weather for controlling the charging of the battery and/or the powering of the load.

Description

Solar power system

FIELD OF THE INVENTION

The invention relates to a solar power system. The invention relates further to a control apparatus, a control method and a control computer program for controlling the solar power system.

BACKGROUND OF THE INVENTION

A solar power system comprises a conversion unit like a solar panel for converting sunlight into electrical power. The electrical power is often used for charging a battery, wherein the battery is used for powering a load like a light source. For instance, especially if the solar power system is a solar lighting system, during the day the battery may be charged by converting sunlight into electrical power, wherein during the night the charged battery can power the light source. The charging and powering processes are generally not optimized, which leads to a reduced performance of the solar power system. For example, known solar power systems often have the problem that the battery provides less electrical power than required by the load, because due to the non-optimized charging process not enough electrical power has been used for charging the battery or the battery is not fully chargeable anymore.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a solar power system having an improved control of charging and/or powering processes. It is a further object of the present invention to provide a control apparatus, a control method and a control computer program providing the improved control.

In a first aspect of the present invention a solar power system is presented, wherein the solar power system comprises:

a rechargeable battery,

a conversion unit for converting sunlight into electrical power for charging the battery, a load to be powered by the battery,

a shading determination unit for determining a shading status of the conversion unit, and

a control unit for controlling the charging of the battery and/or the powering of the load depending on the determined shading status of the conversion unit.

Since the shading determination unit determines a shading status of the conversion unit and since the control unit controls the charging of the battery and/or the powering of the load depending on the determined shading status, the control unit can consider a shading of the conversion unit during the control of the charging process and/or of the powering process. Since these processes depend on the charge status of the battery and since the charge status of the battery depends on the electrical power provided by the conversion unit, which in turn depends on the shading of the conversion unit, by considering the shading of the conversion unit while controlling the charging and/or powering processes the quality of these processes can be improved.

The conversion unit is preferentially a solar panel. The shading determination unit is preferentially adapted to determine a shading status caused by physical objects, which may be located on the ground in the proximity of the solar power system, like a building. The load is preferentially a light source to be used during the night such that the battery can be charged during the day and the light source can be powered during the night by using the charged battery. The solar power system is therefore preferentially a solar lighting system.

The shading status can be indicative of whether the conversion unit is shaded or not. However, the shading status can also be indicative of whether the conversion unit is partially shaded. In particular, the shading determination unit can be adapted to determine a degree of shading as the shading status, i.e. the shading determination unit may be adapted to determine a degree of shading of the conversion unit, wherein the control unit may be adapted to control the charging of the battery and/or the powering of the load depending on the determined degree of shading.

It is preferred that the solar power system further comprises an electrical parameter measuring unit for measuring an electrical parameter of the conversion unit, wherein the shading determination unit is adapted to determine the shading status of the conversion unit depending on the measured electrical parameter. This allows determining the shading of the conversion unit in a technically relatively simple way, in particular, without necessarily requiring further information. The electrical parameter measured by the electrical parameter measuring unit is preferentially the output current of the conversion unit. In this case, the electrical parameter measuring unit can also be regarded as being an output current measuring unit, wherein the shading determination unit determines the shading status of the conversion unit depending on the measured output current. However, the electrical parameter measuring unit can also be adapted measure another electrical parameter of the conversion unit like the electrical power, the electrical voltage, et cetera, wherein the shading

determination unit can be adapted to determine the shading status of the conversion unit depending on this measured electrical parameter. The shading determination unit can be adapted to determine that the conversion unit is shaded, if the measured electrical parameter has a value being smaller than a predefined threshold, and to determine that the conversion unit is not shaded, if the measured electrical parameter has a value being not smaller than the predefined threshold value. The threshold can depend on the time of the day, i.e. for different times of the day different thresholds can be provided. This allows considering the effect that during the day the intensity of the sun light changes, which leads to changes in the measured electrical parameter, even if the shading status of the conversion unit does not change.

If the shading status of the conversion unit is determined depending on the measured electrical parameter, the determination of the shading status of the conversion unit can consider also a shading caused by non-permanent objects in the surrounding of the conversion unit, which cause a temporally relatively short shading of temporary nature, like emergency communication vehicles, mobile toilets, et cetera.

The electrical parameter measuring unit can also be adapted to measure several electrical parameters of the conversion unit, wherein the shading determination unit can be adapted to determine the shading status of the conversion unit depending on the several measured electrical parameters. For instance, the several electrical parameters can be combined to a combined parameter, wherein the shading determination unit can be adapted to determine that the conversion unit is shaded, if the combined parameter has a value being smaller than a predefined threshold, and to determine that the conversion unit is not shaded, if the combined parameter has a value being not smaller than the predefined threshold value.

In an embodiment the solar power system comprises a spatial information providing unit for providing spatial information about the conversion unit and about the surrounding of the conversion unit, wherein the shading determination unit is adapted to determine the shading status of the conversion unit depending on the provided spatial information. The spatial information includes preferentially geographic information like the longitude and the latitude of the position of the conversion unit and/or of the position of objects in the surrounding of the conversion unit like buildings, trees, et cetera. The spatial information preferentially further includes the dimensions, in particular, the height, width and/or length, of the conversion unit and/or of the objects in the surrounding of the conversion unit. The shading determination unit is preferentially adapted to use further information for determining the shading status of the conversion unit like the incidence angle of the sun light. The incidence angle of the sun light depends on the season, particularly on the day of the year, and the time of the day. Thus, the shading determination unit can be adapted to determine the incidence angle of the sun light depending on the season, particularly on the day of the year, and on the time of the day and depending on incidence angle information being indicative of the dependence of the incidence angle of the sun light on the season, particularly on the day of the year, and on the time of the day.

In an embodiment the shading determination unit is adapted to determine the shading status for different times of a day and to determine a shading profile being indicative of the shading status during a day depending on the shading status determined for the different times of the day, wherein the control unit is adapted to control the charging of the battery and/or the powering of the load depending on the determined shading profile. Since it can be assumed that the shading profile determined for a certain day is also indicative of the shading status at different times on the next day, if non-permanent objects have not been placed in the surrounding of the conversion unit in the meantime, by controlling the powering of the load during the night depending on the shading profile determined for the previous day the powering of the load during the night can be regarded as being controlled depending on the shading profile being indicative of the shading during the next day. The control unit can therefore control the powering of the load during the night such that the battery is discharged to a level only, which allows charging the battery again to a desired level, in particular, completely, during the next day. If the shading and optionally also the weather forecast are not considered, the battery may be discharged deeply, because during the day it cannot be sufficiently charged, which can lead to a bad condition of the battery, which in turn may impact its lifetime.

Thus, the control unit may be adapted to control the powering of the load during the night depending on the shading profile being indicative of the shading status during the next day, i.e. indirectly depending on the determined shading status, whereas during the day the control unit may control the charging of the battery directly depending on the actual shading status, i.e. based on the real time shading status. In particular, the control unit can be adapted to charge the battery only, if the shading status determined for the conversion unit indicates that the conversion unit is not shaded. Moreover, in an embodiment the control unit may comprise assignments between the shading status and charging levels, wherein the control unit can be adapted to control the charging process depending on the actual shading status and these assignments. The assignments can also consider further parameters like the left energy of the battery. For instance, in an embodiment the control unit may comprise assignments between a) the degree of shading and the left energy of the battery and b) the charging level. For instance, the assignments can define that, if the degree of shading is 30 percent and the left energy of the battery is 70 percent, the conversion unit should be switched off, and that, if the degree of shading is 70 percent and the left energy of the battery is 20 percent, the conversion unit should be on for charging the battery. The control unit can also comprise assignments between a) shading profiles or output current values, which have been determined from the shading profiles and which are indicative of the expected output current of the conversion unit during a day, and b) levels of powering the load, wherein during the night the load can be powered depending on the shading profile being indicative of the shading statuses during the next day and these assignments.

The control unit may be adapted to switch the conversion unit off, if the determined shading status indicates that the conversion unit is shaded. Particularly if the conversion unit comprises several photovoltaic cells arranged as strings in a photovoltaic panel being, in this example, the conversion unit, shaded photovoltaic cells will limit the photovoltaic output and act as a load instead of a generator. The shaded photovoltaic cells will generate heat, which might cause reliability issues. By knowing the time, when the conversion unit is shaded, the conversion unit can be switched off during the shading period, in order to increase the reliability of the solar power system.

In an embodiment the solar power system further comprises a weather information providing unit for providing weather information being indicative of the weather at the location of the solar power system, wherein the control unit is adapted to control the charging of the battery and/or the powering of the load also depending on the provided weather information. The weather information providing unit is preferentially adapted to provide weather forecast information as the weather information, wherein the control unit is adapted to control the charging of the battery and/or the powering of the load also depending on the provided weather forecast information. Additionally considering the weather information, in particular, the weather forecast information, while controlling the charging and/or powering processes can further improve the quality of these processes.

The solar power system preferentially comprises several solar power subunits, wherein each solar power subunit comprises a conversion unit, a rechargeable battery unit and a load, wherein the shading determination unit is adapted to determine the shading status of the conversion unit of the respective solar power subunit and wherein the control unit is adapted to control the charging of the battery of the respective solar power subunit by using the electrical power provided by the conversion unit of the respective solar power subunit and/or the powering of the load of the respective solar power subunit depending on the determined shading status of the conversion unit of the respective solar power subunit. Thus, the solar power subunits can be individually addressable such that each solar power subunit can be controlled depending on its specific shading situation, thereby further improving the control of solar power system.

Preferentially, each solar power subunit comprises an electrical parameter measuring unit for measuring an electrical parameter of the conversion unit of the respective solar power subunit, wherein the shading determination unit is preferentially adapted to determine the shading status of the conversion unit of the respective solar power subunit depending on the electrical parameter measured for this conversion unit. Preferentially, the shading determination unit is adapted to compare the electrical parameter measured for the respective conversion unit with a threshold, in order to determine whether the respective conversion unit is shaded or not. This threshold may be determined depending on electrical parameters measured by electrical parameter measuring units associated with reference conversion units, wherein the reference conversion units are conversion units that are supposed to be not shaded. For instance, a number of conversion units can be determined, for which electrical parameters have been measured indicating the highest sunlight intensities, as the reference conversion units. Preferentially, a fixed number, which may be three or another number, of conversion units, for which electrical parameters have been measured indicating the highest sunlight intensities, are determined as the reference conversion units. The threshold can then be determined by, for example, averaging the electrical parameter values measured for the reference conversion units or by selecting from the electrical parameter values measured for the reference conversion units the smallest one. For instance, if the electrical parameter is the output current,a predefined number of conversion units like three conversion units having the highest output currents can be determined as being the reference conversion units, wherein the output currents of these reference conversion units can be averaged for calculating an average output current, which can be used to decide which conversion units are shaded and which conversion units are not shaded by comparing this average output current with the output currents of the respective conversion units. This allows determining which solar power subunits are shaded and which solar power subunits are not shaded in a technically relatively simple way, without necessarily requiring further technical means. In particular, for different times of the day it can be determined which solar power subunits, i.e. which corresponding conversion units, are shaded and which solar power subunits are not shaded, wherein this shading information acquired over the day can be used to determine for each solar power subunit a shading profile, in order to allow the control unit to control each solar power subunit individually depending on the respective individual shading profile.

The solar power system may further comprise a similar performance providing unit for providing batteries having similar performances. For instance, the similar

performance providing unit can be adapted to select batteries having a similar performance depending on the output currents measured by the respective output current measuring units, in order to provide batteries having similar performances. However, it is preferred that the similar performance providing unit is adapted to request the control unit to completely charge or discharge all batteries, in order to provide batteries having the same performance.

The output current of the respective conversion unit may depend on the charge status of the respective battery. If this is the case, different charge statuses for different batteries would lead to different output currents, even if the corresponding conversion units are shaded in the same way or are not shaded, which in turn could lead to a reduced quality of the control of the solar power system. Thus, by ensuring that the batteries of the controlled solar system subunits have the same performance, the control of the solar power system depending on the shading can be further improved.

It is further preferred that the similar performance providing unit is adapted to request the control unit to completely discharge batteries, which are associated with conversion units, for which the shading determination unit has determined that they are not shaded, in order to provide batteries having the same performance. In particular, the similar performance providing unit can be adapted to request the control unit to completely discharge all batteries, if the shading determination unit has determined that all respective conversion units are not shaded. This discharging step is preferentially performed at least one time immediately after the installation of the solar power system, because at the beginning of operating the solar power system the performance of the batteries is the best.

If the solar power system further comprises a weather information providing unit for providing weather information being indicative of the weather at the location of the solar power subunits, the similar performance providing unit is preferentially adapted to request the control unit to completely discharge the batteries, if the weather information is indicative of a sunny day, in order to provide batteries having the same performance.

Preferentially, the similar performance providing unit is adapted to request the control unit to completely discharge all batteries, if the corresponding conversion units are not shaded and the weather information is indicative of a sunny day. This can ensure that the batteries are only discharged completely, if enough sunlight is present, which allows charging the batteries again.

The control unit is preferentially further adapted to control the charging and/or the powering of the battery also depending on the charge status of the battery. Thus, preferentially the control unit is adapted to control the charging of the battery and/or the powering of the load depending on the shading status of the conversion unit and additionally depending on the charge status of the battery, i.e. depending on the remaining energy in the battery. Optionally, as explained above, the control unit can be adapted to control the charging and/or the powering of the battery also depending on further information like weather information, in particular, weather forecast information. The control unit can comprise assignments between a) the level of charging and/or the level of powering of the battery and b) the determined shading status, the charge status of the battery and optionally further parameters like the weather information, wherein the control unit can be adapted to control the charging and/or the powering of the battery based on these assignments and the determined shading status, the charge status of the battery and the optional further parameters.

In a further aspect of the present invention a control apparatus for controlling a solar power system is presented, wherein the control apparatus comprises:

a shading determination unit for determining a shading status of a conversion unit for converting sunlight into electrical power, and

- a control unit for controlling a charging of a rechargeable battery, which is charged by using the electrical power, and/or a powering of a load, which is powered by the battery, depending on the determined shading status of the conversion unit.

In another aspect of the present invention a control method for controlling a solar power system is presented, wherein the control method comprises:

- determining a shading status of a conversion unit for converting sunlight into electrical power by a shading determination unit, and

controlling a charging of a rechargeable battery, which is charged by using the electrical power, and/or a powering of a load, which is powered by the battery, by a control unit depending on the determined shading status of the conversion unit. In a further aspect of the present invention a control computer program for controlling a solar power system is presented, wherein the control computer program comprises program code means for causing a control apparatus as defined in claim 12 to carry out the steps of the control method as defined in claim 14, when the control computer program is run on a computer controlling the control apparatus.

It shall be understood that the solar power system of claim 1, the control apparatus of claim 13, the control method of claim 14, and the control computer program of claim 15 have similar and/or identical preferred embodiments, in particular, as defined in the dependent claims.

It shall be understood that a preferred embodiment of the invention can also be any combination of the dependent claims or above embodiments with the respective independent claim.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following drawings:

Fig. 1 shows schematically and exemplarily an embodiment of a solar power system,

Fig. 2 schematically and exemplarily illustrates a shading of solar power subunits of the solar power system shown in Fig. 1,

Fig.3 shows a flowchart exemplarily illustrating an embodiment of a control method for controlling the solar power system shown in Fig. 1, and

Fig. 4 exemplarily and schematically shows different strings of a photovoltaic panel of the solar power system shown in Fig. 1.

DETAILED DESCRIPTION OF EMBODFMENTS

Fig. 1 shows schematically and exemplarily an embodiment of a solar power system. The solar power system 1 comprises several solar power subunits 6, wherein each solar power subunit 6 comprises a rechargeable battery 4, a conversion unit 3 for converting sunlight 2 into electrical power for charging the battery 4 and a load 5 to be powered by the battery 4. In this embodiment the conversion unit 3 is a solar panel and the load 5 is a light source to be used during the night such that the respective battery 4 can be charged during the day and the respective light source 5 can be powered during the night by using the charged respective battery 4.

The solar power subunits 6 are connected with a control apparatus 14 via a wired or wireless data connection 7. Preferentially, the solar power subunits 6 and the control apparatus 14 are adapted to communicate with each other via the Internet. The control apparatus 14 comprises a shading determination unit 9 for determining a shading, i.e. a shading status, of the conversion units 3 of the solar system subunits 6 and a control unit 8 for controlling a charging of the batteries 4 and a powering of the loads 5 depending on the determined shading of the conversion units 3. The shading determination unit 9 is

preferentially adapted to determine a shading of the conversion units 3 caused by physical objects, which are located on the ground in the proximity of the solar power subunits, like one or several buildings.

The solar power system 1 further comprises output current measuring units 10 for measuring the output currents of the conversion units 3. In this embodiment several output current measuring units 10 are associated with the respective conversion units 3 for measuring the output currents. The shading determination unit 9 is adapted to determine the shading of the respective conversion unit 3 depending on the respective measured output current. In particular, the shading determination unit 9 is adapted to determine the shading for different times of a day for the individual conversion units 3 and to determine for each conversion unit 3 a shading profile being indicative of the shading during a day depending on the shading determined for the different times of the day for the respective conversion unit 3, wherein the control unit 8 is adapted to control the charging of the respective battery 4 and/ or the powering of the respective load 5 depending on the shading profile individually determined for the respective conversion unit 3. Preferentially, the control unit 8 is adapted to control the powering of the respective load 5 during the night depending on the respective individual shading profile, which can be assumed as being indicative of the shading during the next day, if generally possible random disturbances caused by, for instance, emergency communication vehicles, mobile toilets, et cetera can be ignored.

For determining which conversion units 3 are shaded and which conversion units 3 are not shaded at a time of the day the shading determination unit 9 can be adapted to determine several reference conversion units 3, which are not shaded, depending on their respective output current and to determine whether the other conversion units 3 are shaded or not by comparing their respective output current with a threshold which is determined depending on the the output currents of the reference conversion units, wherein, if the respective output current is smaller than the threshold, the respective conversion unit 3 is regarded as being shaded and, if the respective output current is not smaller than the threshold, the respective conversion unit 3 is regarded as being non shaded. In particular, the shading determination unit 9 is adapted to a) determine several conversion units 3, for which the highest output currents have been measured, as the reference conversion units, b) calculate the threshold by averaging the output currents measured for the reference conversion units or by determing the smallest output current measured for the reference conversion units, and c) determine whether the conversion units 3 are shaded or non-shaded by comparing the respective measured output current with the threshold. For instance, a predefined number of conversion units like three conversion units having the highest output currents can be determined as being the reference conversion units, wherein the output currents of these reference conversion units can be averaged for calculating an average output current as the threshold, which can be used to decide which conversion units are shaded and which conversion units are not shaded by comparing this threshold with the output currents of the respective conversion units. The control unit 8 is adapted to switch a conversion unit 3 off, if the determined shading status indicates that the respective conversion unit 3 is shaded.

Moreover, the control unit 8 is preferentially adapted to control the charging of the batteries 4 and/or the powering of the loads 5 depending on weather information, in particular, depending on weather forecast information, provided by a weather information providing unit 11. The weather information providing unit 11 can have an Internet connection for receiving the weather information via the Internet. However, the weather information providing unit 11 can also be connected via a wired or wireless data connection to another unit providing the weather information, without using the Internet. The weather forecast information can be used to control, for instance, the powering of a load during the night, wherein this control is performed such that the thereby discharged battery can be charged again during the next day by electrical power which is expected during the next day. For example, if the weather forecast information indicates that the next day will not be a sunny day, the control unit 8 may control the powering of the loads 5 such that they consume less power, whereas, if the weather forecast information indicates that the next day will be a sunny day, the control unit 8 may control the powering of the loads 5 such that they consume more power. Regarding the shading profiles the control unit 8 can be adapted such that a load associated with a conversion unit, which will be shaded during a longer time during the next day, receives less power during the night and a load associated with a conversion unit, which will be shaded over a shorter time during the next day, receives more power from the battery during the night.

The control unit 8 is further adapted to control the charging and/or the powering of the battery 4 also depending on the charge status of the battery 4, i.e. depending on the energy left in the battery 4. For instance, the control unit 8 can be adapted to decrease the powering of the load, if the energy left in the battery 4 is low, in particular, smaller than a predefined threshold. Regarding the charging of the battery, the control unit 8 can be adapted to charge the battery with the maximum charging current that the conversion unit can provide, if the charge status, i.e. the remaining energy in the battery, is smaller than a predefined threshold, for instance, if only 20 percent of the energy remained.

The control unit 8 is preferentially adapted to determine a battery charge value being indicative of the charge status of the battery, wherein the charging and/or powering of the battery is controlled depending on the determined battery charge status value. The battery charge status value is, for example, a voltage measured at the battery. The battery charge status value can also be a battery capacitance, which may be determined based on a known charging curve of the battery, which relates a measured voltage to the battery capacitance, and a voltage measured at the battery.

In an embodiment the control unit 8 is adapted to control the charging of the battery 4 and/or the powering of the load 5 depending on the determined shading of the conversion unit and the provided weather information. For example, the control unit 8 can be adapted such that the battery is charged, even if the conversion unit 3 is shaded, if the provided weather information indicates that today and/or the coming next several days the weather is cloudy, in particular, rainy. Moreover, the control unit 8 may be adapted to control the powering of the load 5 depending on the shading profile, if the conversion unit 3 is shaded and if the weather information indicates a sunny day. For instance, the control unit 8 may be adapted such that on sunny days the conversion unit 3 may be switched on or switched off depending on the shading profile, if the conversion unit 3 is shaded.

In a further embodiment the control unit 8 can be adapted to control the charging of the battery 4 and/or the powering of the load 5 depending on the determined shading and the respective time of the day. For instance, the control unit 8 can be adapted to switch off the conversion unit 3, if the conversion unit 3 is shaded in the morning.

Furthermore, the control unit 8 can be adapted to control the charging of the battery 4 such that the battery 4 is charged, if the conversion unit 3 is shaded in the afternoon or close to the evening. The control unit 8 may be further adapted to also consider the left capacity of the battery and/or the weather information. Thus, the control unit 8 can be adapted to control the charging of the battery 4 and/or the powering of the load 5 depending on the determined shading, the time of the day and the left capacity and/or the weather information.

In a further embodiment the control unit 8 can be adapted to control the charging of the battery 4 and/or the powering of the load 5 depending on the determined shading, the weather information, the capacity status and the shading profile, wherein the shading profile may be used in combination with the time of the day.

In particular, the control unit 8 may be adapted to consider any combination of the mentioned factors for controlling the charging of the battery 4 and/or the powering of the load 5, especially if the conversion unit 3 is shaded.

The solar power system 1 further comprises a similar performance providing unit 12 for providing batteries 4 having similar performances. In particular, the similar performance unit 12 is adapted to adjust or calibrate the batteries 4 such that they have substantially similar performances. In this embodiment the similar performance providing unit 12 is adapted to request the control unit 8 to completely charge or discharge the batteries 4 at one or several times during their lifetime, in order to adjust or calibrate the batteries such that they have substantially the same performance. Preferentially, the similar performance providing unit 12 is adapted to request the control unit 8 to completely discharge all batteries 4, if the shading determination unit 9 has determined that all conversion units 3 are not shaded and if the weather information indicates a sunny day. This complete discharging of all batteries 4 is preferentially performed immediately after the solar power system 1 has been installed, because at the beginning of operating the solar power system 1 the performance of the batteries 4 is the best. Moreover, the similar performance providing unit 12 can be adapted to request the control unit 8 to completely charge or discharge the batteries 4 at certain time intervals, for instance, per week, per day, several times a day, in particular, per hour, et cetera.

The solar power system 1 can further comprise a spatial information providing unit 13 for providing spatial information about the conversion unit 3 and about the surrounding of the conversion unit 3, wherein the shading determination unit 9 can be adapted to determine the shading status of the conversion unit 3 depending on the provided spatial information. The spatial information includes geographic information like the longitude and the latitude of the position of the conversion unit 3 and of the position of objects in the surrounding of the conversion unit 3 like buildings, trees, et cetera. The spatial information provided by the spatial information providing unit 13 further includes the dimensions, in particular, the height, width and/or length, of the conversion unit 3 and of the objects in the surrounding of the conversion unit 3. The spatial information particularly includes the height position of the conversion unit above ground, if the conversion unit is arranged above the ground, for instance, mounted on a post. The shading determination unit 9 further uses the incidence angle of the sun light for calculating the shading status of the conversion unit 3. The incidence angle of the sun light depends on the season, particularly on the day of the year, and the time of the day. The shading determination unit 9 is therefore preferentially adapted to determine the incidence angle of the sun light depending on the season, particularly on the day of the year, and the time of the day and on incidence angle information being indicative of the dependence of the incidence angle of the sun light on the season, particularly on the day of the year, and on the time of the day. This incidence angle information, which may also be regarded as being incidence angle assignments, can be stored in the shading determination unit 9. The spatial information about the conversion unit 3 and about the objects in the surrounding of the conversion unit 3 can be stored in the spatial information providing unit 13. The spatial information may have been manually input by a user into the spatial information providing unit 13 or the spatial information may at least partly automatically be determined, wherein this spatial information can be stored in the spatial information providing unit 13, in order to allow the spatial information providing unit 13 to provide this information. For instance, at least a part of the spatial information may be automatically determined by using a GPS device, which may be integrated in the shading information providing unit 13 or in another unit, wherein the spatial relation between the GPS containing unit and the conversion unit 3 is known and stored in the spatial information providing unit. Moreover, the solar power system may comprise measuring units for automatically measuring spatial dimensions of objects in the surrounding of the conversion unit 3 for providing information about, for instance, the height, width and/or length of these objects.

Fig. 2 shows schematically and exemplarily the solar power subunits 6 mounted on posts 18 for providing street light. A sun 16 provides sunlight, wherein a building 15 located on the ground 19 generates a shadow 17 shading some solar power subunits 6. In the situation exemplarily and schematically shown in Fig. 2 the shading determination unit 9 will determine that the two right solar power subunits 6 are shaded, whereas the other solar power subunits 6 are not shaded. During the day the shadow 17 will be modified such that it will also be modified which solar power subunits 6 are shaded and which solar power subunits 6 are not shaded. The shading determination unit 9 can continuously or repeatedly determine which solar power subunits 6 are shaded and which solar power subunits 6 are not shaded during the day, wherein the control unit 8 can control the charging of the batteries of the solar power subunits 6 depending on the determined shading situation. For instance, the control unit 8 can be adapted to control the charging of the batteries of the solar power subunits 6 such that only the batteries are charged, which are electrically connected to conversion units being non-shaded. Since during the day the shading situation changes, it is also changed during the day which batteries are charged. In other words, the charging pattern, which may be defined by the distribution of batteries which are actually charged and batteries which are actually not charged, preferentially follows the shading pattern, i.e. the shading situation.

In the following an embodiment of a control method for controlling a solar power system will exemplarily be described with reference to the flowchart shown in Fig. 3.

In step 101 the shading determination unit 9 determines the shading status of the individual conversion units 3 and in step 102 the control unit 8 controls the charging of the batteries 4 and/or the powering of the loads 5 depending on the determined shading statuses of the conversion units 3. The control can be immediately, i.e., for instance, depending on the current shading status of the conversion units 3 the charging of the batteries 4 can be individually controlled. For example, if a certain conversion unit 3 is shaded, the conversion unit 3 may be switched off and the respective battery 4 may not be charged, whereas, if a conversion unit 3 is not shaded, the battery may be charged. However, the control unit 8 can also be adapted to not immediately respond to an actually determined shading status. For instance, in step 101 the shading determination unit 9 can determine a shading profile being indicative of the changing shading statuses of the several conversion units 3 during the day, and during the night step 102 can be performed for powering the loads 5 depending on the determined shading profile, i.e. indirectly - via the shading profile - depending on the shading statuses determined during the day.

In known solar power systems shading effects significantly reduce the performance of the solar power system, because the charging period for charging the battery is reduced, thereby in turn reducing the electrical power stored in the battery. The battery is a weak point in the solar power system such that the battery usage should be optimized to reduce the deep discharge status fo the battery. In order to optimize the usage of the battery, the solar power system is preferentially adapted to detect the shading status for the individual solar lighting panels, i.e. for the individual conversion unit. The determined shading status can then be used to control the solar power system such that the individual batteries are utilized in a better way such that the performance of the batteries can be improved.

The control apparatus for controlling the solar power system can be regarded as being a backend lighting management system, wherein the individual solar power subunits are individually addressable via the data connection 7, which may be a wireless Internet connection, by using the backend lighting management system. The backend lighting management system can comprise an input unit 20 for allowing an operator to individually control the solar power subunits. The operator can also monitor the individual shading status of the respective conversion unit by using an output unit like a monitor 21.

The shading determination unit can be adapted to filter the output current data, before determining the shading status, in order to not reduce the quality of the shading determination by short, minor, temporary shadings, which may be caused by, for instance, flying birds. This filtering can be, for example, a temporal low-pass filter, in order to filter out temporally short output current variations, which may be caused by, for example, flying birds.

From the measured output currents of a whole day the shading periods can be determined, i.e. it can be determined when which conversion unit was shaded. This information can be used to determine a shading profile, wherein for determining a shading profile data measured over several days and optionally also over different seasons may be used, in order to obtain a very complete and robust picture.

A partial shading of conversion units, which are preferentially photovoltaic panels, can cause a significant performance drop and decrease the reliability of the solar power system. This is especially the case, if the photovoltaic cells are arranged as strings in a photovoltaic panel as schematically and exemplarily shown in Fig. 4. In Fig. 4 two strings 30, 31 are shown, wherein a first string 30 comprises photovoltaic cells 32, 33, 34 and a second string comprises photovoltaic cells 35, 36, 37. If the photovoltaic panel is shaded only partially, only some of the photovoltaic cells 32...37 are shaded. Shaded photovoltaic cells will limit the whole photovoltaic output and act as a load instead of acting as a generator. Moreover, a shaded photovoltaic cell will generate heat, which may cause reliability issues. By knowing the period of shade of the respective conversion unit the control unit can switch off the respective conversion unit during the shading period, in order to increase the reliability of the solar power system.

The battery management strategy performed by the solar power system described above with reference to Figs. 1 and 2 uses the determined shading information for increasing the lifetime of the battery. In particular, if a weather forecast indicates good sunshine in the next several days and if the load is a light source, the light source may be controlled such that the lumen output is increased at night, i.e. that the battery will output more energy and be discharged deeply. Ideally, this works very well, because the battery can recover by being charged with enough electrical power provided by the conversion units in the next sunny days. However, if there is a shading caused by a building and if this shading would not be considered, the output of the conversion unit will be decreased such that the battery, which is in a low energy status due to the deep discharge during the night, cannot be fully charged. The battery may therefore be in a bad condition, which in turn may impact its lifetime. Since, if this shading would not be considered, the electrical power provided by the conversion units will always be less than predicted under consideration of the weather forecast, the battery management strategy will not work properly. For this reason the solar power system described above with reference to Figs. 1 and 2 determines and uses the shading information. By estimating the shading impact and preferentially also considering the weather forecast, the solar power system can optimize the power output at night, in order to balance lumen output and battery lifetime.

Although in above described embodiments the shading determination unit 9 determines whether the conversion unit is shaded or not as shading status, the shading determination unit 9 can also be adapted to determine a degree of shading as the shading status, wherein in this case the control unit 8 can be adapted to control the charging of the battery 4 and/or the powering of the load 5 depending on the determined degree of shading of the conversion unit 3 and optionally depending on further factors like the left battery capacity, the weather information, et cetera. These dependencies can be stored in the control unit 8 in the form of, for instance, tables and/or functions. For instance, the control unit 8 can be adapted to keep charging, if the degree of shading is 25 percent and the left battery capacity is 20 percent, whereas, if the degree of shading is 25 percent and the left battery capacity is 80 percent, the conversion unit 3 may be switched off.

Although in above described embodiments the control unit is located externally from the solar power subunits, in other embodiments the control unit can also be a distributed control unit comprising several control subunits integrated in the solar power subunits. In this case the control subunit of a respective solar power subunit can receive the determined shading status from the shading determination unit and control the charging and/or the powering of the battery of the respective solar power subunit depending on the received shading status, which has been determined for the conversion unit of the respective solar power subunit. Also the shading determination unit can be a distributed unit comprising several shading determination subunits integrated in the solar power subunits. In this case the respective control subunit may receive the determined shading status from the respective shading determination subunit.

Although in above described embodiments the output current measuring units are integrated in the conversion units, they can also be separate from the conversion units. For instance, if the control unit is a distributed control unit comprising several control subunits integrated in the solar power subunits, the output current measuring units can also be integrated in the control subunits.

Although in an above described embodiment a threshold for determining whether a conversion unit is shaded or not shaded is determined by averaging output currents measured for reference conversion units or by selecting from the output currents measured for the reference conversion units the smallest one, the threshold for determining which conversion units are shaded and which conversion units are not shaded can also be determined by using another dependence of the threshold on the output currents measured for the reference conversion units.

Although in accordance with above described embodiments the shading status can be determined based on the output currents of the conversion units, in other embodiments the shading status can also be determined depending on other electrical parameters of the conversion units like the electrical power or the electrical voltage of the conversion units.

Although in accordance with above described embodiments the shading status can be determined based on a single electrical parameter, i.e. the output current, the electrical parameter measuring unit can also be adapted to measure several electrical parameters of the conversion unit, wherein the shading determination unit can be adapted to determine the shading status of the conversion unit depending on the several measured electrical parameters. For instance, the several electrical parameters can be combined to a combined parameter, wherein the shading determination unit can be adapted to determine that the conversion unit is shaded, if the combined parameter has a value being smaller than a predefined threshold, and determine that the conversion unit is not shaded, if the combined parameter has a value being not smaller than the predefined threshold value.

Although in above described embodiments the solar power system is preferentially a solar lighting system, wherein the loads are light sources, in other

embodiments the solar power system can also be used to power other kinds of loads like wireless communication modules. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

A single unit or device may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Processes like the determination of the shading status of conversion units, the provision of weather information, the provision of similar performances of the batteries, the control of the charging of the battery and/or of the powering of the load et cetera performed by one or several units or devices can be performed by any other number of units or devices. For example, steps 101 and 102 can be performed by a single unit or by any other number of different units. These processes, in particular, the control of the solar power system in accordance with the control method, can be implemented as program code means of a computer program and/or as dedicated hardware.

A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Any reference signs in the claims should not be construed as limiting the scope.

The invention relates to a solar power system like a solar lighting system comprising a rechargeable battery, a conversion unit like a solar panel for converting sunlight into electrical power for charging the battery, a load like a lighting device to be powered by the battery, a shading determination unit for determining a shading status of the conversion unit and a control unit for controlling the charging of the battery and/or the powering of the load depending on the determined shading status of the conversion unit. Considering the shading status allows for an optimized control such that the lifetime of the battery can be increased. The control unit preferentially uses further information like the charge status of the battery and information about the weather for controlling the charging of the battery and/or the powering of the load.

Claims

CLAIMS:

1. A solar power system comprising:

a rechargeable battery (4),

a conversion unit (3) for converting sunlight into electrical power for charging the battery (4),

a load (5) to be powered by the battery (4),

a shading determination unit (9) for determining a shading status of the conversion unit (3), and

a control unit (8) for controlling the charging of the battery (4) and/or the powering of the load (5) depending on the determined shading status of the conversion unit (3).

2. The solar power system as defined in claim 1, wherein the shading determination unit (9) is adapted to determine a degree of shading as the shading status, wherein the control unit (8) is adapted to control the charging of the battery (4) and/or the powering of the load (5) depending on the determined degree of shading of the conversion unit (3).

3. The solar power system as defined in claim 1, wherein the solar power system (1) further comprises an electrical parameter measuring unit (10) for measuring an electrical parameter of the conversion unit (3), wherein the shading determination unit (9) is adapted to determine the shading status of the conversion unit (3) depending on the measured electrical parameter.

4. The solar power system as defined in claim 1, wherein the solar power system (1) further comprises a spatial information providing unit (13) for providing spatial information about the conversion unit (3) and about the surrounding of the conversion unit (3), wherein the shading determination unit (9) is adapted to determine the shading status of the conversion unit (3) depending on the provided spatial information.

5. The solar power system as defined in claim 1, wherein the shading determination unit (9) is adapted to determine the shading status for different times of a day and to determine a shading profile being indicative of the shading status during a day depending on the shading status determined for the different times of the day, wherein the control unit (8) is adapted to control the charging of the battery (4) and/or the powering of the load (5) depending on the determined shading profile.

6. The solar power system as defined in claim 1, wherein the control unit

(8) is adapted to switch the conversion unit (3) off, if the determined shading status indicates that the conversion unit (3) is shaded.

7. The solar power system as defined in claim 1, wherein the control unit (8) is adapted to control the charging and/or the powering of the battery (4) also depending on the charge status of the battery (4).

8. The solar power system as defined in claim 1, wherein the solar power system (1) further comprises a weather information providing unit (11) for providing weather information being indicative of the weather at the location of the solar power system (1), wherein the control unit (8) is adapted to control the charging of the battery (4) and/or the powering of the load (5) also depending on the provided weather information.

9. The solar power system as defined in claim 1, wherein the solar power system (1) comprises several solar power subunits (6), wherein each solar power subunit (6) comprises a conversion unit (3), a rechargeable battery (4) unit and a load (5), wherein the shading determination unit (9) is adapted to determine the shading status of the conversion unit (3) of the respective solar power subunit (6) and wherein the control unit (8) is adapted to control the charging of the battery (4) of the respective solar power subunit (6) by using the electrical power provided by the conversion unit (3) of the respective solar power subunit (6) and/or the powering of the load (5) of the respective solar power subunit (6) depending on the determined shading status of the conversion unit (3) of the respective solar power subunit (6).

10. The solar power system as defined in claim 9, wherein each solar power subunit (6) comprises an electrical parameter measuring unit (10) for measuring an electrical parameter of the conversion unit (3) of the respective solar power subunit (6), wherein the shading determination unit (9) is adapted to: determine several reference conversion units (3), which are not shaded, depending on the electrical parameters measured by the electrical parameter measuring units (10) of the respective solar power subunits (6),

determine a threshold depending on the electrical parameters measured by the electrical parameter measuring units associated with the reference conversion units

(3) , and

determine the shading status of the conversion units (3) of the other solar power subunits (6) by comparing the electrical parameters measured by the electrical parameter measuring units (10) of the other solar power subunits (6) with the threshold.

11. The solar power system as defined in claim 9, wherein the solar power system (1) further comprises a similar performance providing unit (12) for providing batteries

(4) having similar performances.

12. The solar power system as defined in claim 11, wherein the similar performance providing unit (12) is adapted to request the control unit (8) to completely charge or discharge batteries (4), in order to provide batteries (4) having the same

performance.

13. A control apparatus for controlling a solar power system, the control apparatus (14) comprising:

a shading determination unit (9) for determining a shading status of a conversion unit (3) for converting sunlight into electrical power, and

a control unit (8) for controlling a charging of a rechargeable battery (4), which is charged by using the electrical power, and/or a powering of a load (5), which is powered by the battery (4), depending on the determined shading status of the conversion unit (3).

14. A control method for controlling a solar power system, the control method comprising:

determining a shading status of a conversion unit (3) for converting sunlight into electrical power by a shading determination unit (9), and

controlling a charging of a rechargeable battery (4), which is charged by using the electrical power, and/or a powering of a load (5), which is powered by the battery (4), by a control unit (8) depending on the determined shading status of the conversion unit (3).

15. A control computer program for controlling a solar power system, the control computer program comprising program code means for causing a control apparatus as defined in claim 13 to carry out the steps of the control method as defined in claim 14, when the control computer program is run on a computer controlling the control apparatus.