FIELD OF THE INVENTION

The present invention relates to temperature control of battery storage systems, particularly grid connected battery storage systems.

BACKGROUND OF THE INVENTION

Normally when controlling the temperatures within an energy storage system (ESS), such as a battery storage system, a Heating Ventilation and Air Condition (HVAC) system is responsible for the tempering of the container of a battery storage system. In ordinary HVAC systems there is only one temperature sensor within the container and the sensor is often placed close to the air inlet. Based on the temperature measurement of this one sensor, the control of the temperature in the container is operated. With such system, the temperature across the container can not be monitored and the temperature gradient between the high and low points of the container as well as start and end point of the container is often very large. A large temperature gradient is not optimal for securing an efficient and secure battery storage system.

US 2017/365893A1 discloses an energy storage system and a temperature control method for the same. The energy storage system includes a first battery group having a plurality of sections, which respectively have at least one battery module and at least one cooling fan; at least one first slave battery management system (BMS) coupled to the first battery group to monitor a temperature value of battery modules included in the first battery group for each section and generate first temperature information having the monitored temperature value for each section; a master BMS configured to transmit the first temperature information according to a predetermined rule; and a control unit configured to output a first control signal for adjusting a rotation speed of at least one cooling fan provided in at least one of the plurality of sections, based on the first temperature information transmitted from the master BMS.

Whereas US 2017/365893A1 addresses temperature control of battery storage systems, the publication does not satisfactorily solve the problem with temperature gradients. Hence, an improved temperature control method would be advantageous, and in particular, a more efficient and/or reliable temperature control method for a grid connected battery storage system would be advantageous.

OBJECT OF THE INVENTION

It is an object of the invention to provide a method with which the temperature gradients of the battery storage system are minimized.

It is an object of at least some embodiments of the invention to provide a method and an apparatus with which the control of the battery system is a 'distributed control', wherein at least two sensors, at least one heater, air-cooling and/or fans are arranged in the battery storage system in a distributed manner.

It is an object of at least some embodiments of the invention to provide a method and an apparatus with which the battery storage system is complimentary with a HVAC system.

It is a further object of the present invention to provide an alternative to the prior art. In particular, it may be seen as an object of the present invention to provide a battery storage system that solves the above-mentioned problems of the prior art.

SUMMARY OF THE INVENTION

Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a temperature control method for a grid connected battery storage system, the battery storage system comprises one or more battery modules situated in a container, an air conditioning unit, at least one heater and at least two temperature sensors arranged at different locations in the container, the method comprises

- obtaining temperatures from the at least two temperature sensors,

- controlling the at least one heater to generate heat, based on the obtained temperatures, for reducing a temperature difference between the obtained temperatures. By container is meant a structure wherein the battery units are situated. This container could be structures as a shipping container, but it could also be a building, a housing, a holder or an enclosure made for the purpose.

By "grid" is meant an electrical grid. An electrical grid is an electrical power network arranged for transmission of electrical power.

The battery or batteries of the "battery storage system" could be based on any kind of battery; For example, the battery storage system is a lithium ion based battery storage system.

The controlling of the heaters could be achieved with on-off control, feedback control or any other controlling method that is suitable.

The invention is particularly, but not exclusively, advantageous in being able to control the temperature difference and minimize the temperature gradients within the battery storage system, as the plurality of distributed temperature sensors, the one or more heaters or distributed heaters and the at least one air conditioning unit allow a better and more optimal temperature distribution within the battery storage system and thereby enables improved control of the temperature gradient.

By "temperature gradient" is meant the temperatures across and/or through the container e.g. the temperature difference between the high and low point of the container or e.g. the temperature difference between the start-point and the endpoint of the container.

As an example, the battery storage system may be used to support the electric grid, for example when errors occurs in the grid, e.g. when the frequency is dropping or rising.

Also, the invention is particularly, but not exclusively, advantageous for generating a safety, accessible and climate-secured space in a DC-zone of the battery storage system due to the temperature distribution and the control and minimization of the temperature gradient. In addition, the invention is particularly, but not exclusively, advantageous for possibly offering a complete framework for Climate, Safety and Access Management of battery storage systems.

In some embodiments of the invention, the battery storage system comprises two or more heaters arranged at different locations in the container.

The use of two or more heaters may be advantageous for improving heat distribution in the battery storage system and thereby minimizing the temperature gradient of the system.

In some embodiments of the invention the method comprises initiating the controlling of the at least one heater if a temperature condition is satisfied.

This may be advantageous for having a system that, even under a satisfied condition, is prepared for intervening whenever the temperature conditions are not satisfied.

Furthermore, this may be advantageous for allowing several modes of operation to increase system reliability.

In some embodiments of the invention, the temperature condition is satisfied if the temperature difference is below a maximum threshold difference.

Advantageous, the temperature control by use of heating elements is only allowed if the temperature difference is not too great. For temperature differences above the maximum threshold difference, further heating could lead to exceeding a maximum temperature of some of the battery modules. Thus, satisfying the maximum threshold difference is not a condition for starting the temperature control, but a condition for allowing the temperature control. In principle, the temperature control by use of heating elements could be initiated when the temperature difference exceeds a lower temperature difference, such as a difference above zero, e.g. 0.5 degree Celsius. In some embodiments of the invention, the temperature condition is satisfied if a maximum temperature in the container is below a threshold.

Advantageously, the use of heating elements for reducing the temperature gradient is only initiated when the a given temperature is below a maximum temperature threshold to avoid generating to high temperatures at some locations in the container.

In some embodiments of the invention the method comprises reducing a charging or discharging power of the battery storage system if the temperature difference exceeds a threshold.

Advantageous, this may allow the system to enter a de-rated power mode due to e.g. temperature rise or rise in the temperature difference or if entry by a person in the DC side of the battery storage system is needed or if there is any malfunction in the system.

In some embodiments of the invention, the battery storage system comprises at least one ventilation fan arranged to distribute cooled air from the air conditioning unit and/or heated air from the at least one heater, and wherein the method comprises controlling the at least one ventilation fan so as to reduce the temperature difference.

Advantageously, the at least one ventilation fan may allow a better and more optimal temperature distribution within the battery storage system, as the at least one ventilation fan is arranged to distribute the temperature of the plurality of distributed heaters and/or the cooled air from the air conditioning unit. The ventilations fan thereby being able to minimize the temperature gradients within the system due to the temperature control.

Embodiments of the invention may be particularly, but not exclusively, advantageous in that they offer a battery storage system that functions complimentarily with an air conditioning system arranged for overall cooling of the container. In some embodiments of the invention, the battery storage system comprises two or more ventilation fans arranged at different locations in the container.

Advantageous distributed ventilation fans may provide a more optimal temperature distribution within the battery storage system.

In some embodiments of the invention, the plurality of temperature sensors and the plurality of heaters are arranged intermingled in the container.

The intermingled temperature sensors and heaters may be advantageously for minimizing the temperature gradient of every point of the container as the temperature sensors and heaters are distributed and the temperature control unit is thereby provided with temperature data from all areas of the container.

Embodiments of invention may be particularly, but not exclusively, advantageous for implementing a heat control algorithm included in an EMS (Energy Management System) e.g. a battery storage system and thereby to minimize the temperature gradient.

In some embodiments of the invention, the method comprising stopping the controlling of the at least one heater if the temperature difference is less than a minimum threshold difference.

Advantageous, this may allow the system to stop controlling if the temperature gradient is within a range of an acceptable temperature level.

The above-described object and several other objects may also be obtained in a second aspect of the invention by providing a temperature controller for controlling a grid connected battery storage system, wherein the temperature controller comprises a control unit arranged to perform the temperature control method.

In some embodiments of the invention, the temperature control system for controlling a grid connected battery storage system comprises

- a temperature controller - at least one heater, and

- at least two temperature sensors arranged at different locations in the container when installed.

A further aspect of the invention relates to a computer program product comprising software code adapted to control a temperature of a grid connected battery storage system when executed on a data processing system, the computer program product being adapted to perform the method of the first aspect.

The aspects of the present invention may each be combined with any of the other aspects. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The method and system according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure 1 schematically shows a battery storage system according to an embodiment of the invention.

Figure 2 schematically shows an example of a design of distributed control system with distributed sensors and distributed heaters.

Figure 3 schematically shows an example of temperature gradients within a battery storage system and the placement of a temperature sensor in prior battery storage systems.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a temperature controller TC for controlling a grid G connected battery storage system 100, wherein the temperature controller comprises a control unit arranged to perform a temperature control method. The temperature control system for controlling a grid connected battery storage system shown in figure 1 comprises a temperature controller TC, a plurality of heaters 140, and a plurality temperature sensors 150 arranged at different locations in the container 120 when installed. The container may be a shipping container. Embodiments and examples of the invention may be implemented in any suitable container 120.

Furthermore, a plurality of ventilation fans 130 are arranged within the container providing an illustrated airflow 160 within the container.

FIG. 1 further illustrates the plurality of temperature sensors and the plurality of heaters 140 being arranged intermingled in the container 120. It is a preferred arrangement to intermingle the heater and the temperature sensors 150 as this arrangement provides the most optimal and exact temperature sensing arrangement.

FIG. 1 furthermore illustrates a battery storage system 100 with a temperature control method according to a presently preferred embodiment of the invention. The grid connected battery storage system comprises one or more battery modules 110 situated in a container 120. The container preferably being accessible for e.g. a service man through a door 170 or the alike. Furthermore, the illustrated system comprises at least one air conditioning unit AC and a plurality of fans 130. The air conditioning unit AC provides cooled air to the container and the fans are arranged to distribute the cooled air in the container. In addition, the illustrated system comprises at least one heater 140 and at least two temperature sensors 150 arranged at different locations in the container 120.

Preferably, as shown in figure 1, a plurality of heaters 140 and a plurality of temperature sensors 150 are distributed within the container 120 in a way allowing the system to control the temperature of the battery storage system without the risk of sensing a non-precise temperature, i.e. the distributed temperature sensors are capable of determining a variation of the temperature within the container 120. Figure 1 thereby illustrating a battery control system having a reliably and optimal temperature control due to the optimal sensing of the temperature differences in the container. A preferred method of controlling the temperature within the container comprises at least the step of obtaining temperatures from the at least two temperature sensors 150, preferably from a plurality of distributed temperature sensors. From the sensed temperatures of the plurality of temperature sensors the method comprises a step of controlling of the at least one heater 140 to generate heat, based on the obtained temperatures, for reducing a possible temperature difference AT between the obtained temperatures. For a more optimal temperature system, the system comprises two or more heaters 140 arranged at different locations in the container 120, where the two or more heaters are controlled so as to reduce the temperate difference AT when controlled based on the measured temperatures.

The controlling of the temperature and the heaters of the battery storage system could be anything between a complex and detailed control method to a very simple on-off control or e.g. a feedback control.

A part of the controlling of the battery storage system 100 is preferably initiating the controlling of the at least one heater if a temperature condition is satisfied. Such step of controlling provides a control method that, even under a satisfied condition, is preparing for intervening whenever a temperature condition is satisfied and thereby increasing system reliability, as the temperature control TC indicates when to active or deactivate the relevant fans and heaters/coolers within the system.

Within the temperature control method, the temperature condition is satisfied if the temperature difference AT is below a maximum threshold difference ATmax. Thus, the maximum threshold difference ATmax sets a condition for initiating the temperature control based on the heaters, while other conditions may also have to be met. For example, the maximum temperature threshold difference ATmax may be in the range from 4-15 °C.

The temperature control method of the system further comprises a step of reducing a charging or discharging power of the battery storage system 100 if the temperature difference AT exceeds a threshold. This de-rated power setting may be initiated to prevent a further increase of the temperature difference. It was found that de-rating of one or more selected battery modules reduced the wear of challenged module considerably while typically allowing to keep a significant part of the battery storage system available online. In other cases, this reduced the likelihood of increasing damage to (other parts of) the battery storage system and hence increased safety of operating the battery storage system. For other cases, it was realized that operating a battery storage system according to predictions or modelling may be useful in many cases, but failure or unexpected incidents (for example an airconditioning access being plugged by an animal) are in nature seldom predictable and can hence usually not be taken into account when operating a heating/ventilating/airconditioning system for a battery system. Introducing one or more of the de-rating method accorting to the invention was found to reduce the risk that smaller incidents would lead to major damage to battery storage systems or significant lifetime reduction. The reduction in charging or discharging power may be for the whole battery storage system 100. The reduction in charging or discharging power may for example be by 10 - 80% of the normal charging or discharging power.

It is preferred that the battery storage system comprises more battery modules 110. When temperature sensors 150 are arranged so temperature difference for individual battery modules may be identified, then reduction in charging or discharging power may be on a battery module level by one (or more) battery modules 110 exhibiting the temperature difference AT exceeding the threshold charging or discharging at reduced power, while other battery modules 110 (with temperature difference AT below the threshold) charging or discharging at nonreduced power. Since the charging or discharging power of the battery storage system 100 is the sum of the charging or discharging power of the battery modules, then reduction of charging or discharging power of one or more battery modules will also reduce the charging or discharging power of the full battery storage system.

In another mode of operating in de-rated power setting, reduction in charging or discharging power for individual battery modules 110 exhibiting the temperature difference AT exceeding the threshold, may be have reduced the charging or discharging power to zero. This reduction in charging or discharging power according to one of the above derated power settings may be temporary (for example until the temperature difference AT does not exceed the threshold), semi-permanently (for example until the battery module 110 has been serviced) or permanently (as a safety precaution).

Within the temperature control method, a further temperature condition is satisfied if a maximum temperature in the container is below a threshold Tmax. This condition secure that the temperature in the container does not excess a maximum temperature and is thereby obtaining a container with a trustworthy secure temperature control system wherein the temperature never excess a temperature level that is not safe and secure and possibly dangerous for a battery storage system 100.

A battery storage system 100 should comprise at least one ventilation fan 130 arranged to distribute cooled air from the air conditioning unit AC and/or heated air from the at least one heater. From FIG 1 it is seen that the battery storage system comprises three ventilation fans 130 and the ventilation fans are arranged at different locations in the container 120. The method of controlling the system within the container may further comprise controlling the at least one ventilation fan so as to reduce the temperature difference AT, as the ventilation fan causes an air flow 160 through the container and thereby mixing the air and temperature in the container generating a minimum temperature gradient within the container.

The battery storage system illustrated in FIG 1 is furthermore connected to a grid.

FIG. 2 schematically illustrates a temperature controller TC for controlling a grid G connected battery storage system 100, wherein the temperature controller comprises a control unit arranged to perform a temperature control method. The temperature control system for controlling a grid connected battery storage system shown in figure 2 comprises a temperature controller, a plurality of heaters 140, and a plurality temperature sensors 150 arranged at different locations in the container 120 when installed. Furthermore, FIG 2 illustrate the plurality of temperature sensors and the plurality of heaters being arranged intermingled in the container. It is a preferred embodiment to intermingle the heater and the temperature sensors as this arrangement provides the most optimal and exact temperature sensing arrangement.

The battery storage system illustrated in FIG 2 is furthermore connected to a grid.

FIG. 3 schematically illustrates some possible temperature gradients across and/or through the container 120 e.g. the temperature difference between the high and low point of the container or e.g. the temperature difference between the start-point and the end-point of the container. The invention disclosed provides a method to control and minimize the temperature gradients within the battery storage system, as the plurality of distributed temperature sensors (not shown), the plurality of distributed heaters (not shown) and the air at least one air conditioning unit (not shown) allow a better and more optimal temperature distribution within the system.

FIG. 3 further illustrates an example of how the sensing of the temperature within the container of the battery storage system could be arranged prior to this invention. Namely with one temperature sensor 150 in one end of the container 120 next to a HVAC system. Sensing the temperature in only one end is clearly not an optimal temperature sensing as is does not provide a correct temperatures for the whole container, but only a temperature of one small isolated area of the container.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. In addition, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.