DE102020132200A1 - Method for consumption control of an electrical heat generator coupled with a photovoltaic system and a thermal storage unit - Google Patents

Abstract

Method for controlling the consumption of an electrical heat generator (13) coupled with a photovoltaic system (11) and a thermal storage device (12), wherein: - for a future observation period, weather data for the location of the photovoltaic system (11) are obtained via the Internet, which at least one yield forecast value contain for the expected solar radiation and a control unit (15) controls the power of a heat generator so that the power introduced into the thermal storage is dependent on the transmitted yield forecast value.

Description

The invention relates to a method for controlling the consumption of an electrical heat generator coupled to a photovoltaic system and a thermal storage unit.

Methods for controlling self-consumption in a local network with at least one photovoltaic system are known, which work with direct feedback of the generated or excess photovoltaic electricity. These control the devices connected to the local grid in such a way that excess electricity generated locally via the photovoltaic system is not fed into a public grid, but locally, i. H. consumed in the vicinity of generation. The difficulty lies in the fact that the yield of a photovoltaic system fluctuates greatly depending on the time of day and the season.

DE 10 2012 003 227 A1 describes a method for operating a system for providing heat, the system having a heat generator and a heat accumulator with a measuring device for determining the temperature at a point in the heat accumulator or in a pipeline connected thereto. The method includes determining an amount of energy introduced into the heat accumulator by the heat generator, determining a time course of an amount of energy removed from the heat accumulator at a withdrawal point, and determining a state of charge of the heat accumulator. A prognosis of a time course of a future energy extraction at the extraction point and an operating plan for the heat generator are created based on at least one of the parameters temperature, state of charge and predicted energy extraction. A corresponding system that can be controlled using the method described is also disclosed.

In order to be able to use excess power from a photovoltaic system in the home more easily, systems are known on the market that store electrical energy thermally, i.e. to heat water or other matter in a heat storage tank with electricity and use it at a later point in time for hot water supply or room heating use. In the course of the day, with increasing solar radiation, heating elements are activated, which serve to charge the thermal storage, and later deactivated again. The electrical energy is thus converted into thermal energy and stored with very little loss. This type of self-consumption is much easier to carry out than a constant comparison between locally generated electricity, mains electricity and current local consumption.

Methods are also known on the market in which a physical measurement of the self-generated electrical energy, such as a photovoltaic current, is carried out using measuring instruments.

The object of the present invention is therefore to further simplify a method for controlling consumption in a thermal storage device coupled to a photovoltaic system.

As a solution, the invention proposes a method for controlling the consumption of an electrical heat generator coupled to a photovoltaic system and a thermal storage unit, having the features of claim 1 .

According to the invention, there is no need for a complex recording and coordination of the electrical energy generated with the photovoltaic system and the instantaneous consumption in the local network. Preferably, the actually generated energy is not even transmitted to the public grid at all and the power is provided directly on the basis of a yield forecast for the installation site.

The particular advantage is that the loading of the thermal storage tank can be controlled by including a yield forecast and the loading is minimized by drawing electrical power from the public supply network, and this with a significantly reduced installation effort compared to solutions in which a measurement or The actually existing overcurrent supply is calculated.

In particular, following a discharge, e.g. As a result of hot water consumption in the evening or heating in the early morning, a new loading cycle is not automatically carried out using electricity drawn from the public grid. Such loading only takes place in exceptional cases if the minimum comfort level defined by the user is not reached.

Example 1:

A very simple embodiment of the invention relates to a hot water undersink device. This is electrically connected to a domestic installation in which electricity is fed from a photovoltaic system, which is preferably referred to as photovoltaic electricity.

The hot water undersink device has a small control unit for imaging the method according to the invention, which z. B. is equipped with a radio modem to access a location via WLAN from the local network or via mobile communications access the related irradiation forecast. From this, a switch-on and a switch-off threshold are defined, from which the electrical heating device in the under-sink hot water device is switched on or off.

Since the yield forecast gives a certain probability that the storage tank can be heated during this period using locally generated electricity from the PV system, no feedback is required with other system parts, so that no complex electrical installation is required beyond establishing Internet access is. The under-sink hot water device can be assembled like any conventional one by plumbing professionals, which involves a single acting person. With the advantage of the simple construction, installation and low error rate of an autonomous unit, it is accepted that in individual cases, due to a change in the weather, heating does not take place via photovoltaic electricity.

Example 2

An electrically heated storage tank has two charging temperatures. A low temperature (comfort temperature) defines the minimum comfort value, e.g. B. 50 °C. The heating is always regulated to this temperature so that the minimum comfort requirements of the user are satisfied. A higher storage charging temperature (storage charging temperature) is used to store additional electrical energy in the form of thermal energy in the storage.

A location-specific irradiation forecast is sent to the system via the Internet. This is converted into an electrical yield forecast using the installation parameters of the local photovoltaic system specified by at least one person or the users.

By observing and comparing with the real income, this conversion can be optimized by the person with a correction factor. Corresponding forecast data is displayed to the person.

The person now uses a threshold value to determine when the system switches to the higher storage tank charging temperature and thus activates charging. With this threshold value, the person takes into account the electricity demand to be expected in the house. The power requirement of the system is displayed to the person.

The person can optionally exclude certain times from charging via a time program, e.g. times when high consumption is to be expected in the building, during which the potential surplus is also limited.

The system uses and stores energy preferably at times when an excess of photovoltaic power is to be expected.

The reliance on pure forecast data may result in weather changes that occur leading to a reduction rather than an increase in the amount of usable energy, because if bad weather is expected, charging is not carried out at all, even if the actual weather conditions deviate from the forecast later develop better than expected. On the other hand, it can happen that the photovoltaic system should charge the heat generator in a time interval determined as suitable according to the forecast, although the real solar radiation is much lower than expected.

However, this system-related disadvantage is offset by the fact that, according to the invention, the effort involved in installing the system is significantly reduced and the advantage of simple control during operation, which is much easier to handle for manual installation companies such as homeowners than a complex control strategy in which measurement data is recorded and evaluated in real time and performance adjustments are made be made .

For the purpose of charging the thermal store, the heating output can be controlled in stages or steplessly.

The usable thermal storage capacity can be optimized via a higher temperature setpoint.

The higher temperature setpoint allows the thermal storage tank to be loaded beyond the normally set flow or hot water temperatures. When delivering hot water from the storage tank, it may be necessary to mix it directly with cold water before it is fed into the domestic water distribution system, e.g. B. exclude a risk of scalding.

With the time requirement specification, the energy requirement of the can be planned more precisely in a future reference period, especially if events that cannot be foreseen in terms of the system occur and are caused by the residents. Examples include a total absence of the person or occupants for vacation, or a scheduled heating of a pool or hot tub.

When operating the control unit, the person can enter parameters for the photovoltaic system and information about their consumption profile. This information can be used to determine the lei Adaptation of the heat generator to the expected photovoltaic surplus.

• 1 ein Ablaufdiagramm für das Verfahren nach der Erfindung an
• 2 ein Gebäude mit einer Fotovoltaik-Anlage und einem Speicher in schematischer Ansicht; und
• 3 Schaltzeiten und Sonneneinstrahlung über der Zeit aufgetragen;
• 4 Schaltzeiten und variierende Sonneneinstrahlung über der Zeit.

The method is described below using an exemplary embodiment and with reference to the drawings. The drawings show:

• 1 a flowchart for the method according to the invention
• 2 a building with a photovoltaic system and a storage device in a schematic view; and
• 3 Switching times and solar radiation plotted over time;
• 4 Switching times and varying solar radiation over time.

1 is a flow chart for the method according to the invention, in which a very simple device is heated with a thermal storage, such as the already described under-sink hot water device.

Steps F-a 201 and VW-a 202 are only carried out as part of a start sequence after initial installation or after the energy management has been shut down. In step 201 F-a, parameters of the photovoltaic system are read in, in order to adapt prognosis data, which can only be called up generally from public sources for the system location, to special circumstances of the local installation. For example, obstacles in the vicinity can lead to shading of the collectors with a certain constellation of azimuth and direction of the solar radiation.

A following step AW-e 203 represents the beginning in a repeating sequence of steps 203...207 of the method. In step AW-e 203 weather forecast data is obtained from the Internet. In a procedure at step FAW204, a predicted photovoltaic system output is calculated using the forecast data and the parameters of the own system.

At least two points in time are determined from the system output in steps FAE 205, FAA 206 by comparison with a switch-on threshold and with a switch-off threshold, at which the heat storage is activated according to block Wa 210 or deactivated according to block Wd ₁₁ 211. In the case of the under-counter water heater, this is done simply by raising or lowering the set temperature, causing the electric heating element to switch on and off at the times specified in advance, without the need for a check with the actual system capacity at those times. is provided.

A last step Ea 207 is inserted as a termination criterion. If the automatic energy management is not to be continued after the one-time storage cycle has been run through, the method is ended, advantageously the heat storage is deactivated according to block Wd ₁₂ 212, otherwise it is started again by returning to the procedure at step AW-e 203.

Heat storage is activated in a block Wa 210 and deactivated in blocks Wd ₁₁ 211 and/or Wd ₁₂ 212 . Step 201 Read photovoltaic system parameters (Fa) Step 202 Establish a connection to the weather service (VW-a) Step 203 Import current weather data (AW-e) Step 204 Calculate photovoltaic system performance with weather data and system parameters (FAW) Step 205 Photovoltaic system performance >= switch-on threshold? (FAE) Step 206 Photovoltaic system power < switch-off threshold? (FAA) Step 207 Energy management active? (Ea) block 210 Enable Heat Storage (Wa) block 211 Disable heat storage (Wd ₁₁ ) Block 212 Disable heat storage (Wd ₁₂ )

• - Eine für den Standort des Fotovoltaik-Moduls 11 geltende Ertragsprognose wird internetbasiert von einem Wetterdatendienst bezogen. Dazu ist eine Steuerungseinheit 15 über ein WLAN- oder GSM-Modul 16 mit dem Internet verbindbar.
• - Ggf. sind aufgrund von abweichenden Werten für Azimut und Neigung des Fotovoltaik-Moduls 11 auf dem Gebäudedach im Vergleich zu den normierten Daten der Ertragsprognose Korrekturen vorzunehmen.
• - Der Beobachtungszeitraum wird festgelegt, beispielsweise auf 2 Tage.
• - Der durchschnittliche Eigenbedarf an thermischer Energie wird festgelegt. Als Vorschlag wird die in einem gleich langen vergangenen Bezugszeitraum aus dem Speicher 12 abgerufene Energie zugrunde gelegt. Der Eigenbedarfswert kann vom Benutzer überschrieben werden.

2 shows a possible complex system configuration in which the method can be carried out. A photovoltaic module 11 is mounted on a building 10 and is connected to a local AC voltage network via an inverter 14 . A thermal store in the form of a hot water tank 12 and a heat generator in the form of a heat pump 13 are also installed in the building 10 .

• - A yield forecast applicable to the location of the photovoltaic module 11 is obtained from a weather data service on the internet. For this purpose, a control unit 15 can be connected to the Internet via a WLAN or GSM module 16 .
• - Corrections may have to be made due to deviating values for azimuth and inclination of the photovoltaic module 11 on the building roof compared to the standardized data of the yield forecast.
• - The observation period is set, for example to 2 days.
• - The average internal requirement for thermal energy is determined. As a suggestion the energy retrieved from the memory 12 in a past reference period of the same length is taken as a basis. The self-consumption value can be overwritten by the user.

The control unit 15 controls the power of the heat pump 13 in such a way that the power fed into the thermal store 12 is dependent on the yield forecast transmitted via the Internet access 16 . This means that the heat pump 13 is primarily fed by the photovoltaic system, which consists of the photovoltaic module 11 and the inverter 14, when the forecast indicates a time interval with sufficient solar radiation. The invention primarily does not provide for switching points that are dependent on actual real-time weather conditions.

A line 12.1 leads from the heat pump 13 into the memory 12 and a line 12.2 out of it. A temperature sensor 18 in the store 12 is connected to the control unit 15 in order to be able to determine the degree of loading. In particular, this is an integral sensor unit with several heat sensors in order to be able to precisely determine the degree of loading despite different water layers in the storage tank. In addition, an additional electrical heating element 17 is provided in the reservoir 12 .

3 shows two superimposed diagrams. In the lower diagram, several graphs 1, 2 are shown one above the other, which reflect the performance of the photovoltaic system over the time of day by way of example.

The solid line 1 corresponds to the yield forecast obtained in advance from weather data. Accordingly, on a cloudless day in summer, it can be expected that the solar radiation will increase from sunrise at 5 a.m. to the highest level at noon, reach a maximum there and then decrease again until sunset at just before 10 p.m.

After this predicted course, the switching interval is defined in the control unit 15, in which an electrical connection between the photovoltaic module 11, the inverter 14 and the heat pump 13 is established. As in the top graph 3 in 3 recognizable, which represents the switching time, the switchover takes place in each case at a threshold value P ₁ . This corresponds to an electrical output with which the heat pump 13 can be operated particularly efficiently, plus an expected consumption in the household.

The dashed line 2 corresponds to the real trend on the day for which the forecast was issued. The maximum performance is therefore reached a little later and is also a little lower because, for example, early haze has to clear up first. However, the switching time is not affected by this; it is strictly based on the forecast period. Nevertheless, electrical energy is generated via the photovoltaic module 11 in the switching interval and the storage device 12 is loaded with it after conversion into thermal energy by means of the heat pump 13 .

In the case of volatile solar radiation, the yield forecast to be expected for the performance of the photovoltaic system fluctuates. According to 4 a corresponding graph 4 of the yield forecast to be expected is drawn in, which predicts a volatile course of the power generated by the photovoltaic channel over time. The sun, which is actually most radiant at the zenith, will probably be at least partially covered by clouds and the photovoltaic output will be reduced.

As on the top graph 5 in 4 can be seen, which represents the switching time, the switchover takes place in each case at a threshold value Po. This corresponds to an electrical output with which the heat pump 13 or another household appliance can advantageously be operated. A minimum output for the operation of a speed-controlled heat pump is available from the photovoltaic system. Even if the output drops, the heat pump continues to operate if an increase in output is to be expected afterwards. Advantageously, the heat pump is only switched off when there is no longer any prospect of sufficient output, for example when evening is approaching or clouds mean that sufficient solar radiation can no longer be expected.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102012003227 A1 [0003]

Claims (11)

Method for controlling the consumption of an electrical heat generator (13) coupled to a photovoltaic system (11) and a thermal storage device (12), in which: - For a future observation period, weather data for the location of the photovoltaic system (11) are obtained via the Internet, which contain at least one yield forecast value for the expected solar radiation and - A control unit (15) controls the power of a heat generator in such a way that the power fed into the thermal storage unit is dependent on the transmitted yield forecast value. procedure after claim 1 , characterized in that at least one switch-on time and one switch-off time are determined and stored in the control unit (15) by comparing the time profile of the yield forecast value with a switch-on threshold and a switch-off threshold, and that the heat generator is activated by the control unit (15) at these points in time and be deactivated, the operation of the heat generator with the photovoltaic system (11) generated electricity during the charging intervals is independent of the actual weather data and electricity yields. procedure after claim 1 or 2 , characterized in that parameters for the photovoltaic system (11) that can be changed by a person and/or a consumption profile can be stored in the control unit (15) and that the control unit (15) calculates the yield forecast value obtained from the Internet, taking into account the parameters and/or the Demand profile is adjusted before the switching times are determined. Method according to one of the preceding claims, characterized in that - at least one heat demand value for the store (12) is calculated for the observation period; - that on the basis of the related weather data a weather-dependent yield forecast value for the photovoltaic system (11) is created; - That charging intervals are determined by a comparison of the yield forecast value and the heat requirement value, in which the heat generator (13) for operation with the photovoltaic system (11) generated electricity is provided; and - in the observation period, the heat generator (13) is charged during the previously specified charging intervals via the heat generator fed by the photovoltaic system (11). procedure after claim 4 , characterized in that: - the actual heat requirement in the building (10) and the power achieved with the photovoltaic system (11) are added up over the observation period and compared with the forecast data, - that by comparing the real heat requirement with the forecast Heat demand value and/or a correction factor is formed from the real output of the photovoltaic system (11) to the yield forecast value; - that in at least one subsequent observation period, the yield forecast value and/or the heat demand value are adjusted using the respective correction factor. Method according to one of the preceding claims, characterized in that the distribution of the power consumption is controlled in stages over time. Method according to any of the preceding Claims 1 until 5 , characterized in that the distribution of the power reference is continuously controlled over time. Method according to one of the preceding claims, characterized in that the usable thermal storage capacity is influenced by the person by specifying a time requirement. Method according to one of the preceding claims, characterized in that the usable thermal storage capacity is influenced by temporarily changing the temperature setpoint. Method according to one of the preceding claims, characterized in that one or more of the following devices are used as storage (12): - a hot water storage, - a heat storage heater, - an electric surface heating and/or - a heating buffer storage. Method according to one of the preceding claims, characterized in that as a heat generator: - an electric heating rod and/or - a heat pump (13) is (are) used.

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