US20190078809A1

US20190078809A1 - Solar collector arrangement

Info

Publication number: US20190078809A1
Application number: US15/704,306
Authority: US
Inventors: Mats Manderbacka; Timo Sivula
Original assignee: Double M Properties AB
Current assignee: Double M Properties AB
Priority date: 2017-09-14
Filing date: 2017-09-14
Publication date: 2019-03-14
Also published as: WO2019053332A1; EP3682172A1; EP3682172A4

Abstract

A solar collector arrangement comprises at least two solar collectors, each solar collector comprising at least one collector element with at least one flow channel for receiving heat transfer medium to be heated in the solar collector. The at least two solar collectors are arranged in parallel connection relative to each other and the heat transfer medium to be heated in the solar collectors and the heat transfer medium heated in the solar collectors are arranged to flow into the solar collectors and out of the solar collectors in turns one or some solar collectors of the solar collector arrangement at a time.

Description

FIELD OF THE INVENTION

The present invention relates to solar energy and particularly to a solar collector arrangement to be used for collecting solar energy.

BACKGROUND OF THE INVENTION

One type of solar collectors is a solar collector, wherein solar heat energy received by the solar collector is conducted to heat transfer medium flowing in flow channels in the solar collector. The solar collectors of that kind are often arranged to form a group of solar collectors, or a solar collector arrangement, wherein a number of originally separate solar collectors are connected in series so that the heat transfer medium is arranged to flow through all the solar collectors forming the solar collector arrangement.

BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is to provide a novel solar collector arrangement for collecting solar energy.
The invention is characterized by the features of the independent claims.
A solar collector arrangement comprises at least two solar collectors, each solar collector comprising at least one collector element with at least one flow channel for receiving heat transfer medium to be heated in the solar collector, at least one inflow passage for allowing a flow of the heat transfer medium to be heated into the at least one flow channel and at least one outflow passage for allowing a flow of heat transfer medium heated in the solar collector out of the at least one flow channel. The at least two solar collectors in the arrangement are arranged in parallel connection relative to each other and the heat transfer medium to be heated in the solar collectors and the heat transfer medium heated in the solar collectors are arranged to flow into the solar collectors and out of the solar collectors in turns in a part of the solar collectors at a time.
An advantage of the invention is that the heat transfer medium heated in the solar collectors may be collected out of the solar collectors only one or some solar collectors at a time. The operation of the solar collector arrangement may thus be controlled only one solar collector or some solar collectors at a time. There is thus no need to wait until the heat transfer medium in each and every solar collector in the solar collector arrangement has reached a specific target temperature before collecting the heat transfer medium out of the solar collectors. By draining the solar collectors in sequence each solar collector spends a large time in a no-flow state, when heating is accelerated. This way the output temperature of the whole collector group is higher than it would be in the case of constant flow.
Some embodiments of the invention are disclosed in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which

FIG. 1 shows schematically a top view of a solar collector arrangement;

FIG. 2 shows schematically an internal assembly and operation of a control unit of the solar collector arrangement; and

FIG. 3 shows schematically a temperature comparison table.

For the sake of clarity, the figures show some embodiments of the invention in a simplified manner. Like reference numerals identify like elements in the figures.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows schematically a top view of a solar collector arrangement 1. The solar collector arrangement 1 comprises a number N of solar collectors 2, FIG. 1 disclosing solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _N. The solar collectors 2 of FIG. 1 comprise a number of adjacent collector elements 3 between which there may be free spaces 4. The collector elements 3 are intended to receive the solar heat energy and to conduct it to heat transfer medium that is arranged to flow inside the collector elements 3. The collector elements 3 thus form or provide internal flow channels for the heat transfer medium in the solar collectors 2 and the heat transfer medium receives the heat energy collected by the collector elements 3 and conveys it forward. Because the collector elements 3 are arranged to form flow channels for the heat transfer medium in the solar collectors 2, the same reference sign 3 may be used in this specification when it is referred either to the collector element in the solar collector 2 or to the flow channel provided by the collector element 3. The heat transfer medium may for example be water or a mixture of water and glycol.
Alternatively to the embodiment shown in FIG. 1 the solar collectors 2 and the collector elements 3 therein may be arranged to provide a single uniform solar collector arrangement structure in view of its mechanic structure, but wherein solar collectors 2 being operationally separate from each other are provided by valves intended to control the flow of the heat transfer medium in the solar collector arrangement 1.
The solar collector 2 comprises an inflow passage 5. The inflow passages 5 of the solar collectors 2 are connected to a feeding channel 9 of the solar collector arrangement 1. The feeding channel 9 is intended to feed cool heat transfer medium to be heated into the solar collectors 2 through the inflow passages 5 in the solar collectors 2. A direction of the flow of the heat transfer medium in the feeding channel 9 is shown in FIG. 1 schematically with an arrow IF. The feeding channel 9 is connected to a circulation pump 11 that is intended to circulate the heat transfer medium in the solar collector arrangement 1.
The solar collector 2 comprises an outflow passage 6. The outflow passages 6 of the solar collectors 2 are connected to a discharge channel 10 of the solar collector arrangement 1. The discharge channel 10 is intended to receive the heat transfer medium heated in the solar collectors 2 through the outflow passages 6 in the solar collectors 2 and to forward the heated heat transfer medium to a heat recovery element 12. A direction of the flow of the heat transfer medium in the discharge channel 10 is shown in FIG. 1 schematically with an arrow OF.
The solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nare typically positioned in somewhat slanted position so that upper ends of the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nconnected to the discharge channel 10 are on a higher position than lower ends of the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nconnected to the feeding channel 9.
The heat recovery element 12 represents a device or a location at which the heat energy collected by the solar collectors 2 and conducted into the heat transfer medium is either stored for later use or is transferred to another system. The heat recovery element 12 may thus be or comprise a heat reservoir or a heat exchanger, for example. The heat recovery element 12 is not part of the solar collector arrangement 1 but the solar collector arrangement 1 is connected to the heat recovery element 12 via the feeding channel 9 and the discharge channel 10.
Each solar collector 2 comprises in the outflow passage 6 a flow control valve 7. An opening of the flow control valve 7 determines a rate of flow of the heated heat transfer medium out of the respective solar collector 2. An operation of the flow control valve 7, i.e. the opening of the flow control valve 7, is controlled by a respective pilot motor 8. The pilot motors 8 of the solar collectors 2 are connected to a control unit 13 through a control bus CO8, whereby the pilot motors 8 control the opening of the flow control valves 7 in response to respective control commands received from the control unit 13. The control unit 13 provides a control unit of the solar collector arrangement 1.
In the solar collector arrangement 1 of FIG. 1 the solar collectors 2 are arranged in parallel connection relative to each other so that a single portion of the heat transfer medium is arranged to become supplied and flown through only a single solar collector in the solar collector arrangement 1, whereby different portions of the heat transfer medium are arranged to become supplied and flown through different solar collectors 2 in the solar collector arrangement 1. In other words the inflow passages 5 of the solar collectors 2 are arranged in parallel connection relative to each other and the outflow passages 6 of the solar collectors 2 are arranged in parallel connection relative to each other.
When the flow control valve 7 of a specific solar collector 2 is opened, the portion of the heat transfer medium heated in the solar collector 2 flows out of the solar collector 2 to the discharge channel 10 through the outflow passage 6 in the respective solar collector 2.
The flow of the heat transfer medium out of the solar collector 2 takes place by the pressure effect provided by the circulation pump 11. The circulation pump 11 starts to pump cool heat transfer medium to be heated into the solar collector 2 through the respective inflow passage 5 as soon as the heat transfer medium already heated in the solar collector 2 is started to be collected out of the solar collector 2. This means that cool heat transfer medium to be supplied into the solar collector 2 forces or pushes the heat transfer medium already being in the solar collector 2 and heated therein out of the solar collector 2 when the flow control valve 7 of the respective solar collector 2 is opened. Cool heat transfer medium is supplied into the solar collector 2 as long as the flow control valve 7 is open but is interrupted when the flow control valve 7 is closed. Therefore a separate flow control valve in the inflow passage 5 of the solar collector 2 is not necessarily needed. Different possible operation modes of the circulation pump 11 and the solar collector arrangement 1 are explained in more detail later.
The solar collectors 2 in the solar collector arrangement 1 of FIG. 1 may be operated so that portion of the heat transfer medium being in the collector elements 3 of different solar collectors 2 and heated therein are collected out of the solar collectors 2 in turns one solar collector 2 or some solar collectors 2 of the solar collector arrangement 1 at a time. In other words, when a portion of the heat transfer medium being in the collector elements 3 of a specific solar collector 2 or of specific solar collectors 2 and heated therein is collected out of that specific solar collector 2 or the specific solar collectors 2, the portions of the heat transfer medium being in the collector elements 3 of any other solar collector 2 still remains in the solar collector 2 and is prevented to come out of the solar collector 2. This means that when the flow control valve 7 of the specific solar collector 2 or of the specific solar collectors 2 is/are open, the portion of the heat transfer medium being in the specific solar collector 2 or in the specific solar collectors 2 and heated therein is allowed to flow out of the specific solar collector 2 or out of the specific solar collectors 2, whereas the flow control valves 7 of other solar collectors 2 are closed, whereby the portions of the heat transfer medium being in the other solar collectors 2 are prevented from flowing out of the other solar collectors 2.
When the solar collector arrangement 1 of FIG. 1 is introduced, the flow control valves 7 of each solar collector 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nare closed and the circulation pump 11 is turned on and is operated for supplying cool heat transfer medium to the solar collector arrangement 1 as long as a heat transfer circuit provided by all the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _N, the feeding channel 9, the discharge channel 10 and appropriate parts in the heat recovery element 12 are full of the heat transfer medium.
According to an embodiment the circulation pump 11 and the solar collector arrangement 1 are operated intermittently, either between fixed or adjustable time periods. In this embodiment, when a certain period of time has elapsed after introducing the solar collector arrangement 1 as disclosed in the preceding paragraph, the portions of the heat transfer medium heated in the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nare started to be collected out of the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _None solar collector or some solar collectors at a time. This means, for example, that the flow control valve 7 in the outflow passage 6 of the first solar collector 2 ₁is opened as controlled by the control unit 13 through the control bus CO8 and the respective pilot motor 8. At the same time the control unit 13 controls, through a control line CL11, the circulation pump 11 to turn on and start to operate, whereby the portion of the heat transfer medium being in the first solar collector 2 ₁and heated therein starts to flow out of the first solar collector 2 ₁to the discharge channel 10 through the respective outflow passage 6 and a portion of cool heat transfer medium to be heated is supplied from the feeding channel 9 to the first solar collector 2 ₁through the respective inflow passage 5. After all of the portion of the heat transfer medium heated in the first solar collector 2 ₁has been collected out of the first solar collector 2 ₁, the flow control valve 7 in the outflow passage 6 of the first solar collector 2 ₁is closed as controlled by the control unit 13 through the control bus CO8 and the respective pilot motor 8. The circulation pump 11 may be on all the time but the pressure provided by the circulation pump 11 is dimensioned such that it does not cause the flow of the heat transfer medium out of the solar collector 2 unless the flow control valve 7 is opened.
For verifying that all of the portion of the heat transfer medium heated in the first solar collector 2 ₁has been collected out of the first solar collector 2 ₁, there is in the feeding channel 9 a flow indicator 14 for indicating an amount or a measure V_MEASof the heat transfer medium supplied by the circulation pump 11, which measure VM_EASis compared in the control unit 13 to a calculated or determined heat transfer medium volume V_SETof the first solar collector 2 ₁. Generally the heat transfer medium volume V_SETis a set value for the above mentioned volume comparison indicating the volume of the heat transfer medium in a specific solar collector 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nand it may vary if the volumes of the solar collectors in the solar collector arrangement 1 vary. When the measure V_MEASof the heat transfer medium supplied by the circulation pump 11 corresponds to the heat transfer medium volume V_SETof the first solar collector 2 ₁, the flow control valve 7 in the outflow passage 6 of the first solar collector 2 ₁is closed as controlled by the control unit 13 through the control bus CO8 and the respective pilot motor 8.
Next, the portion of the heat transfer medium being in the second solar collector 2 ₂and heated therein is started to be collected out of the second solar collector 2 ₂. This may take place immediately after the portion of the heat transfer medium being in the first solar collector 2 ₁and heated therein is collected out of the first solar collector 2 ₁, or after a certain or an adjustable time period from that. For doing that the flow control valve 7 in the outflow passage 6 of the second solar collector 2 ₂is opened as controlled by the control unit 13 through the control bus CO8 and the respective pilot motor 8, whereby the portion of the heat transfer medium being in the second solar collector 2 ₂and heated therein starts to flow out of the second solar collector 2 ₂to the discharge channel 10 through the respective outflow passage 6 and a portion of the heat transfer medium to be heated is supplied from the feeding channel 9 to the second solar collector 2 ₂through the respective inflow passage 5. After all of the portion of the heat transfer medium heated in the second solar collector 2 ₂has been collected out of the second solar collector 2 ₂, the flow control valve 7 in the outflow passage 6 of the second solar collector 2 ₂is closed as controlled by the control unit 13 through the control bus CO8 and the respective pilot motor 8. Similarly as above, when the measure V_MEASof the heat transfer medium supplied by the circulation pump 11 corresponds to the heat transfer medium volume V_SETof the second solar collector 2 ₂, the flow control valve 7 in the outflow passage 6 of the second solar collector 2 ₂is closed as controlled by the control unit 13 through the control bus CO8 and the respective pilot motor 8.
The procedure disclosed above is repeated as long as the portion of the heat transfer medium being in the last solar collector 2 _Nof the solar collector arrangement 1 and heated therein has been collected out of the last solar collector 2 _Nand replaced with cool portion of the heat transfer medium to be heated in the last solar collector 2 _N. After that the whole procedure for collecting the heat transfer medium out of each solar collector 2 ₁, 2 ₂, . . . , 2 ^N-1, 2 _Nis repeated again, either immediately or after a predetermined or an adjustable time period after the portion of the heat transfer medium being in the last solar collector 2 _Nof the solar collector arrangement 1 has been collected out of the last solar collector 2 _N.
In the embodiment disclosed above the heat transfer medium being in the solar collectors 2 and heated therein is collected out of the solar collectors 2 one single solar collector 2 at a time. As already indicated above, the heat transfer medium being in the solar collectors 2 and heated therein may also be collected out of the solar collectors 2 from more than one single solar collector 2 at a time, for example from some of the solar collectors 2 of the solar collector arrangement 1 at a time. This embodiment may be used for example in operating conditions wherein the amount of the solar collector energy to be collected is high and therefore the temperature of the heat transfer medium in the solar collectors 2 increases rapidly.
According to an embodiment the circulation pump 11 and the solar collector arrangement 1 are operated continuously. This means that immediately after the portion of the heat transfer medium being in a solar collector 2 or in some solar collectors 2 and heated therein has/have been collected out of the solar collector 2 and replaced with cool heat transfer medium, the portion of the heat transfer medium being in the following solar collector 2 or in some following solar collectors 2 and heated therein will be collected out of that following solar collector 2 or following solar collectors 2 and replaced with cool heat transfer medium. After the portion of the heat transfer medium being in the last solar collector 2 _Nand heated therein has been collected out of the last solar collector 2 _Nand replaced with cool heat transfer medium, the procedure for collecting the heated heat transfer medium is started from the beginning again. In this embodiment the control unit 13 is arranged to control the operation of the flow control valves 7 and the circulation pump 11 such that the supply flow of the heat transfer medium towards the solar collectors 2 is preferably adjusted to such an amount that the portion/portions of the heat transfer medium to be supplied to the first solar collector 2 ₁and to possibly some other solar collectors 2 possibly providing a group of solar collectors 2 operating together with the first solar collector 2 ₁, as disclosed above, has/have enough time to heat up to a maximum achievable temperature by the time the portion/portions of the heat transfer medium being in the last solar collector 2 _Nand possibly in some other solar collectors 2 possibly providing a group of solar collectors 2 operating together with the last solar collector 2 _N, has been collected out of the last solar collector 2 _N.
An advantage of the latter embodiment of usage of the solar collector arrangement 1 over the former embodiment of usage is that heated heat transfer medium is supplied constantly to the heat recovery element 12.
The procedures disclosed above are repeated as long as the sun is shining or other circumstances provide that a value of the collected solar heat energy is more than operational expenses of the solar collector arrangement 1.
In the embodiments disclosed above, the portions of the heat transfer medium being in the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nand heated therein are collected out of the solar collectors 2 in turns one solar collector 2 or some solar collectors 2 at a time in a predetermined order. Alternatively, as disclosed in the following embodiments, the portions of the heat transfer medium being in the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nand heated therein is to be collected out of the solar collectors 2 on a basis of the temperature T_HTMof the heat transfer medium in the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _N.
For that purpose each solar collector 2 of the solar collector arrangement 1 may comprise at least one temperature sensor in at least one collector element 3 for measuring the temperature T_HTMof the heat transfer medium in the respective solar collector 2. In this further embodiment, which is schematically disclosed also in FIG. 1, each solar collector 2 comprises two temperature sensors 15U, 15L arranged in the same collector element 3. In its minimum there may be only one temperature sensor in a single solar collector 2 and in its maximum there may be several temperature sensors, i.e. more than two temperature sensors, in each and every collector element 3 of each solar collector 2 ₁, 2 ₂, . . . , 2 _N. 1, 2 _Nalong a longitudinal direction of the collector element 3.
The temperature sensors 15U in upper parts of the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nare connected to a temperature measurement bus TMU which is further connected to the control unit 13 for transferring the measured temperature information in the upper parts of the solar collectors 2 to the control unit 13. The temperature sensors 15L in lower parts of the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nare connected to a temperature measurement bus TML which is further connected to the control unit 13 for transferring the measured temperature information in the lower parts of the solar collectors 2 to the control unit 13.
According to an embodiment the portions of the heat transfer medium being in the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nare collected out of the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _None solar collector 2 at a time or some solar collectors 2 at a time in an order determined by the temperatures T_HTMof the portions of the heat transfer medium in the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _N. In this embodiment it is set into the control unit 13 a target value T_SETfor the temperatures T_HTMof the portions of the heat transfer medium in the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nso that after the temperature T_HTMof the portion of the heat transfer medium in the solar collector 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nhas reached the set target value T_SETin a specific solar collector 2 or in some collectors 2, the portion/portions of the heat transfer medium is collected out of that specific solar collector 2 or out of the specific solar collectors 2 and replaced by a portion of cool heat transfer medium supplied into that specific solar collector 2 or the specific solar collectors 2. The temperature T_HTMof the portion of the heat transfer medium to be compared with the set target value T_SETmay for example be the highest single value of the measured temperatures of the portion of the heat transfer medium provided by the temperature sensors 15U, 15L, or the lowest single value of the measured temperatures of the portion of the heat transfer medium provided by the temperature sensors 15U, 15L or an average value of the temperatures of the portion of the heat transfer medium provided by the temperature sensors 15U, 15L. The target value T_SETmay be set according to known operating characteristics of the solar collectors 2, for example.
In the arrangement disclosed in the preceding paragraph the portion of the heat transfer medium in the solar collector 2 is collected out of the solar collector(s) 2 after the temperature T_HTMof the portion of the heat transfer medium in the solar collector(s) 2 has/have reached the set target value T_SET. The portions of the heat transfer medium are collected out of the solar collectors 2 of the solar collector arrangement 1 in that order according to which order the portions of the heat transfer medium in different solar collectors 2 have reached the set target value T_SET, but so that the heat transfer medium is still collected out of only one solar collector or some solar collectors at a time. In an ideal situation, wherein heat conduction properties and environmental characteristics of all the solar collectors 2 in the solar collector arrangement 1 are same, the order the portions of the heat transfer medium are to be collected out of the solar collectors 2 is in practice the same all the time. Also the circulation pump 11 may then be on and being operated continuously, whereby heated heat transfer medium may be supplied continuously to the heat recovery element 12.
According to an embodiment the solar collector arrangement 1 comprises a weather station 16 connected to the control unit 13, the weather station 16 comprising at least one temperature sensor for measuring air temperature T_AMat the location of the solar collector arrangement 1. On the basis of the measured air temperature T_AMat the location of the solar collector arrangement 1 the control unit 13 may determine the settable target value T_SETfor the temperature T_HTMof the heat transfer medium in the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _N. The weather station 16 may also comprise additional sensors for measuring other properties of the air at the location of the solar collector arrangement 1, such as humidity of air and wind velocity, which may also be used when the target value T_SETfor the temperature T_HTMof the heat transfer medium in the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nis to be determined.
According to an embodiment the solar collector arrangement 1 comprises a server unit 17 connected to the control unit 13, the server unit 17 providing a connection to a weather forecast service providing a weather forecast for a region of the location of the solar collector arrangement 1. The weather forecast may provide at least an estimate for air temperature T_AFin the region of the location of the solar collector arrangement 1. On the basis of the forecasted air temperature T_AFat the location of the solar collector arrangement 1 the control unit 13 may determine the settable target value T_SETfor the temperature T_HTMof the heat transfer medium in the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _N. The weather forecast may also comprise additional information about other properties of the air for the location of the solar collector arrangement 1, such as humidity of air and wind velocity, which may also be used when the target value T_SETfor the temperature T_HTMof the heat transfer medium in the solar collectors 2 ₁, 2 ₂, . . . , 2 _N-1, 2 _Nis to be determined.
In the embodiments of the solar collector arrangement 1 comprising either the weather station 16 or the server 17 the settable target value T_SETto be set for the temperature T_HTMof the heat transfer medium in the solar collectors 2 may be set according to the measured air temperature T_AMor the forecasted air temperature T_AFat the location of the solar collector arrangement 1. In this application the control unit 13 may comprise a learning module 13LM for providing a learning phase which determines the dependency between the measured air temperature T_AMat the location of the solar collector arrangement 1 and the achieved temperature T_HTMof the heat transfer medium in the solar collectors 2 or between the forecasted air temperature T_AFat the location of the solar collector arrangement 1 and the achieved temperature T_HTMof the heat transfer medium in the solar collectors 2. The control unit 13 may also comprise an optimization module 13OM for providing an optimization phase which determines a number of, i.e. at least one, control strategies for controlling operation of the flow control valves 7 on the basis of the dependency between the measured air temperature T_AMor the forecasted air temperature T_AFat the location of the solar collector arrangement 1 and the achieved temperature T_HTMof the heat transfer medium in the solar collectors 2, as determined above.
FIG. 2 shows schematically an internal assembly and operation of the control unit 13 of the solar collector arrangement. The control unit 13 comprises a processor unit 13PU which provides necessary calculation, determination and control operations needed for controlling the operation of the solar collector arrangement 1. For providing those operations the processor unit 13PU comprises a dedicated software implementing those operations.
The control unit 13 comprises also the learning module 13LM, which may be internal or external to the processor unit 13PU, in FIG. 2 it is shown to be external to the processor unit 13PU. As said above, the learning module 13LM is arranged to determine the dependency between the measured air temperature T_AMat the location of the solar collector arrangement 1 and the achieved temperature T_HTMof the heat transfer medium in the solar collectors 2 or between the forecasted air temperature T_AFat the location of the solar collector arrangement 1 and the achieved temperature T_HTMof the heat transfer medium in the solar collectors 2.
The learning module 13LM provides the learning phase, whereby the control unit 13 receives the measured air temperature T_AMor the forecasted air temperature T_AFat the location of the solar collector arrangement 1 and stores that temperature to a comparison table disclosed schematically in the left hand side column of FIG. 3. The comparison table may be maintained in the learning module 13LM. The measured T_AMor forecasted T_AFair temperature may be the highest temperature for a day, or the highest temperature for an hour in the day, whereby the comparison table may be determined as a daily basis or an hourly basis, for example.
For determining the dependency between the measured air temperature T_AMat the location of the solar collector arrangement 1 and the achieved temperature T_HTMof the heat transfer medium in the solar collectors 2 or between the forecasted air temperature T_AFat the location of the solar collector arrangement 1 and the achieved temperature T_HTMof the heat transfer medium in the solar collectors 2, the control unit 13 receives also the achieved measured temperature T_HTMof the heat transfer medium in the solar collectors 2 corresponding to the respective measured air temperature T_AMor the forecasted air temperature T_AFat the location of the solar collector arrangement 1. The control unit 13 stores the measured temperature T_HTM of the heat transfer medium in the solar collectors 2 in the right hand side column in the comparison table at a point corresponding to the respective measured air temperature T_AMor the forecasted air temperature T_AFat the location of the solar collector arrangement 1. The comparison table thus determines or presents the dependency between the measured T_AMor the forecasted T_AFtemperature and the achieved temperature T_HTMof the heat transfer medium in the solar collectors 2. The achieved temperature T_HTMof the heat transfer medium in the solar collectors 2 may be used in the further operation of the solar collector arrangement 1 as target set value T_SETfor the temperature T_HTMof the heat transfer medium in the solar collectors 2 of the solar collector arrangement 1.
The control unit 13 comprises also the optimization module 13OM, which may be internal or external to the processor unit 13PU, in FIG. 2 it is shown to be external to the processor unit 13PU. As said above, the optimization module 13LM is arranged to determine at least one control strategy for controlling operation of the flow control valves 7 on the basis of the dependency between the measured air temperature T_AMor the forecasted air temperature T_AFat the location of the solar collector arrangement 1 and the achieved temperature T_HTMof the heat transfer medium in the solar collectors 2.
In the optimization phase the control unit 13 in co-operation with the learning module 13LM and the optimization module 13OM therein compares the measured temperature T_HTMof the heat transfer medium in the solar collectors 2 to the temperature values presented in the temperature comparison table and controls the operation of the flow control valves 7 accordingly. For example according to an embodiment, if the measured air temperature T_AMor the forecasted air temperature T_AFat the location of the solar collector arrangement 1 is 19 degrees of Celsius and the respective expected temperature T_HTMof the heat transfer medium in the solar collectors 2 is 79 degrees of Celsius, the control unit 13 provides a control operation to open the flow control valve 7 of the solar collector 2 after the temperature sensors 15U, 15L indicate that the temperature T_HTMof the heat transfer medium in that solar collector 2 has reached the value 79 degrees of Celsius. Other kind of control strategies may, however be applied for controlling the operation of the solar collector arrangement 1.
According to an embodiment of the solar collector arrangement 1 comprising the temperature sensors 15U, 15L in the solar collectors 2, the control unit 13 is arranged to determine the second derivative, i.e. the second differential coefficient, d²T_HTM/dt²of the temperature T_HTMof the heat transfer medium in the solar collectors 2. The second derivative d²T_HTM/dt²of the temperature T_HTMof the heat transfer medium indicates the speed of the change of the temperature T_HTMof the heat transfer medium in the solar collector 2 as determined on the basis of at least two successive temperature T_HTMmeasurements of the heat transfer medium. Each solar collector 2 may be considered separately. When the second derivative d²T_HTM/dt²is positive, it means that the heat transfer medium being in the solar collector 2 receives heat with an increasing speed, i.e. more heat in a predetermined time period is received by the heat transfer medium being in the solar collector 2. When the second derivative d²T_HTM/dt²becomes negative, it means that the heat transfer medium being in the solar collector 2 receives heat with a decreasing speed, i.e. less heat in a predetermined time period is received by the heat transfer medium being in the solar collector 2. When the second derivative d²T_HTM/dt²becomes negative, it means that the capability of the heat transfer medium in the solar collector to receive more heat is about to end and it may be more productive in view of the heat collection to collect the heated heat transfer medium out of the solar collector 2 and to fill the solar collector 2 with cool heat transfer medium to be heated although the portion of the heat transfer medium being in the solar collector 2 and heated therein has not yet received the target temperature T_SETset for the temperature T_HTMof heat transfer medium in the solar collector 2.
The determination of the second derivative d²T_HTM/dt²of the temperature T_HTMof the heat transfer medium may be applied in connection with any embodiment disclosed above. FIG. 2 discloses schematically also an operation module for the determination of the second derivative d²T_HTM/dt²of the temperature T_HTMof the heat transfer medium. The operation module for the determination of the second derivative may be internal or external to the processor unit 13PU, in FIG. 2 it is shown to be external to the processor unit 13PU.
In the solution and its embodiments disclosed above the heat transfer medium heated in the solar collectors is collected out of the solar collectors one collector or some solar collectors at a time. This means for example that the portion of the heat transfer medium heated in a single solar collector may be collected out of that solar collector immediately after the heat transfer medium has reached an assumed or a set target temperature for the heated heat transfer medium although the portions of the heat transfer medium in the other solar collectors have not yet reached the target temperature.
According to an embodiment the solar collector arrangement 1 may be used during a winter to melt away snow collected on top of the solar collectors 2. This takes place by feeding warm heat transfer medium from the heat recovery element to the solar collectors 2 through the feeding channel 9, whereby the warm heat transfer medium heats the solar collectors 2 and melts the snow away. A reason for melting the snow away may be to reduce a total weight provided by the snow and the solar collectors 2, thus reducing stresses directed to a structure of a roof. In that embodiment of usage for melting the snow the arrangement is operated only when it is snowing—it does not need to be operated all the time. Another reason for melting the snow away may be to remove the snow early in a spring from the top of the solar collectors so that the solar heat energy may be started to be utilized as soon as the sun will provide enough heat energy after the winter. In that embodiment of usage for melting the snow the arrangement may be operated only once at a time when the snow is intended to be removed from the top of the solar collectors 2. The feed of warm heat transfer medium to the solar collectors 2 for melting the snow may also be utilized in other kind of solar collector arrangement than the solar collector arrangements disclosed above.
It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. A solar collector arrangement comprising

at least two solar collectors, each solar collector comprising at least one collector element with at least one flow channel for receiving heat transfer medium to be heated in the solar collector, at least one inflow passage for allowing a flow of the heat transfer medium to be heated into the at least one flow channel and at least one outflow passage for allowing a flow of heat transfer medium heated in the solar collector out of the at least one flow channel, and in which arrangement

the at least two solar collectors are arranged in parallel connection relative to each other and

the heat transfer medium to be heated in the solar collectors and the heat transfer medium heated in the solar collectors are arranged to flow into the solar collectors and out of the solar collectors in turns one solar collector or some solar collectors of the solar collector arrangement at a time.

2. A solar collector arrangement as claimed in claim 1, wherein

the solar collector arrangement comprises

a feeding channel for feeding the heat transfer medium to be heated into the solar collectors,

a discharge channel for collecting the heat transfer medium heated in the solar collectors out of the solar collectors, and wherein

there is a controllable flow control valve in the outflow passage of each solar collector for controlling the connection of the outflow passage of the solar collector to the discharge channel, and wherein

one flow control valve or some flow control valves is/are arranged to be controlled at a time for controlling the flow of the heat transfer medium to be heated into the solar collectors and the flow of the heat transfer medium heated in the solar collectors out of the solar collectors one solar collector or some solar collectors at a time.

3. A solar collector arrangement as claimed in claim 1, wherein

the solar collector arrangement comprises a control unit configured to control an order of connecting the solar collectors to the discharge channel in turns one solar collector or some solar collectors at a time.

4. A solar collector arrangement as claimed in claim 3, wherein

the control unit is arranged to control the flow control valve of one solar collector or some solar collectors at a time for connecting the outflow passage of one solar collector or some solar collectors to the discharge channel at a time.

5. A solar collector arrangement as claimed in claim 1, wherein

the outflow passages of the solar collectors of the solar collector arrangement are connected to the discharge channel one solar collector or some solar collectors at a time in a predetermined order.

6. A solar collector arrangement as claimed in claim 1, wherein

the solar collector comprises at least one temperature sensor for measuring temperature of the heat transfer medium in the at least one flow channel in the solar collector, and wherein

the solar collectors of the solar collector arrangement are connected to the discharge channel in an order determined on a basis of measured temperatures of the heat transfer medium in the solar collectors.

7. A solar collector arrangement as claimed in claim 6, wherein

a control unit of the solar collector arrangement comprises at least one settable target value for the temperature of the heat transfer medium in the solar collector, and wherein the heat transfer medium is to be collected out of the solar collector to the discharge channel in response to the temperature of the heat transfer medium in the solar collector receiving the target value set for the temperature of the heat transfer medium in the solar collector.

8. A solar collector arrangement as claimed in claim 7, wherein

the solar collector arrangement comprises at least one server unit arranged in connection with a weather forecast service and that the settable target value for the temperature of the heat transfer medium in the solar collector is set on the basis of the forecasted temperature for a region of a location of the solar collector arrangement.

9. A solar collector arrangement as claimed in claim 8, wherein

the control unit comprises a learning unit for describing a dependency between the forecasted air temperature and the respective temperature of the heat transfer medium to be achieved in the solar collector, and wherein the control unit comprises an optimization unit for controlling the operation of the flow control valves of the solar collectors on the basis of the temperature dependency between the forecasted air temperature and the respective temperature of the heat transfer medium to be achieved in the solar collectors.

10. A solar collector arrangement as claimed in claim 6, wherein

a control unit of the solar collector arrangement is arranged to determine a second derivate of the temperatures of the heat transfer medium in the solar collectors and that the control unit is arranged to control the flow control valves of the solar collectors for collecting the heat transfer medium heated in the solar collectors out of the solar collectors in response to the second derivate of the temperature of the heat transfer medium in the solar collector being negative.

11. A method of operating a solar collector arrangement comprising at least two solar collectors arranged in parallel connection relative to each other, each solar collector comprising at least one collector element with at least one flow channel for receiving heat transfer medium to be heated in the solar collector, at least one inflow passage for allowing a flow of the heat transfer medium to be heated into the at least one flow channel and at least one outflow passage for allowing a flow of heat transfer medium heated in the solar collector out of the at least one flow channel, the method comprising

controlling the flow of the heat transfer medium to be heated in the solar collectors into the solar collectors and the flow of the heat transfer medium heated in the solar collectors out of the solar collectors in turns one solar collector or some solar collectors of the solar collector arrangement at a time.

12. A method as claimed in claim 11, comprising

feeding the heat transfer medium to be heated in the solar collectors into the solar collectors through a feeding channel,

collecting the heat transfer medium heated in the solar collectors out of the solar collectors through a discharge channel, and

controlling controllable flow control valves arranged in the outflow passages of the solar collectors one flow control valve or some flow control valves at a time for controlling the flow of the heat transfer medium to be heated into the solar collectors and the flow of the heat transfer medium heated in the solar collectors out of the solar collectors one solar collector or some solar collectors at a time.

13. A method as claimed in claim 11, comprising

controlling an order of connecting the solar collectors to the discharge channel in turns one solar collector or some solar collectors at a time by a control unit of the solar collector arrangement.

14. A method as claimed in claim 13, comprising

controlling by the control unit the flow control valve of one solar collector or some solar collectors at a time for connecting the outflow passage of one or some solar collectors to the discharge channel at a time.

15. A method as claimed in claim 11, comprising

connecting the outflow passages of the solar collectors to the discharge channel one solar collector or some solar collectors at a time in a predetermined order.

16. A method as claimed in claim 11, comprising

measuring temperature of the heat transfer medium in the at least one flow channel in the solar collector and

connecting the solar collectors of the solar collector arrangement to the discharge channel in an order determined on a basis of measured temperatures of the heat transfer medium in the solar collectors.

17. A method as claimed in claim 16, comprising

setting at least one settable target value for the temperature of the heat transfer medium in the solar collector, and

collecting the heat transfer medium out of the solar collector to the discharge channel in response to the temperature of the heat transfer medium in the solar collector receiving the target value set for the temperature of the heat transfer medium in the solar collector.

18. A method as claimed in claim 17, comprising

arranging the solar collector arrangement in connection with a weather forecast service and

setting the settable target value for the temperature of the heat transfer medium in the solar collector on the basis of the forecasted temperature for a region of a location of the solar collector arrangement.

19. A method as claimed in claim 18, comprising

providing in the control unit a learning unit for describing a dependency between the forecasted air temperature and the respective temperature of the heat transfer medium to be achieved in the solar collector, and

providing in the control unit an optimization unit for controlling the operation of the flow control valves of the solar collectors on the basis of the temperature dependency between the forecasted air temperature and the respective temperature of the heat transfer medium to be achieved in the solar collectors.

20. A method as claimed in claim 16, comprising

determining a second derivate of the temperatures of the heat transfer medium in the solar collectors and

controlling the flow control valve of the solar collector for collecting the heat transfer medium heated in the solar collector out of the solar collector in response to the second derivate of the temperature of the heat transfer medium in the solar collector being negative.