WO2020208188A2

WO2020208188A2 - Optimization of energy utilization in solar powered freezer or cooler system

Info

Publication number: WO2020208188A2
Application number: PCT/EP2020/060256
Authority: WO
Inventors: Peter William Dale Bishop
Original assignee: Société des Produits Nestlé S.A.
Priority date: 2019-04-12
Filing date: 2020-04-09
Publication date: 2020-10-15
Also published as: WO2020208188A3

Abstract

The present invention relates to an apparatus configured to manage energy consumption of a freezer or cooler to match available solar energy, the apparatus comprising a controller connectable to associated components in the freezer or cooler, said controller comprising a measuring logic configured to measure parameters selected from the group consisting of current from a solar array, ambient temperature, freezer temperature and battery temperatures, battery voltage and battery current, and availability of an external power supply or a combination thereof, a calculating logic configured to determine availability of excess solar energy beyond that required to maintain the freezer or cooler at its normal set temperature, a memory having the ability to store values and external inputs values, and wherein said controller is configured to control the temperature set point of the freezer or cooler, to utilise solar energy that is available in excess of that required to maintain normal operation of the freezer or cooler in order to lower the temperature set point of the freezer or cooler. The invention also relates to methods of managing energy consumption of a freezer or cooler to match available solar energy.

Description

OPTIMIZATION OF ENERGY UTILIZATION IN SOLAR POWERED FREEZER

OR COOLER SYSTEM

Field of the invention

The present invention relates to an apparatus and method configured to manage energy consumption of a freezer or cooler to match available solar energy.

Background

The majority of freezers and coolers for food and beverages require electrical power to operate. Typically, this power is provided by connection to an electrical grid, or in cases where this is not available, connection to a standalone generator. More recently, power generated from renewable sources such as photovoltaic (PV) arrays or wind turbines may be used as an alternative to generators for locations without a grid connection .

While this offers considerable advantages in operational costs over a fossil-fuelled generator, the performance of photovoltaic (PV) arrays is highly dependent on the prevailing weather conditions and energy storage is required to provide a reserve for periods of low renewable energy generation and in the case of PV, during night time operation. A limitation with these systems is that in order to provide a high availability power source for reliable operation of freezers and coolers to maintain the desired internal temperature, product shelf life and prevent degradation of the products within, the storage capacity of the battery has to be considerably increased over that of a system that is not required to provide continuous power. The higher storage capacity a battery has the more expensive it is likely to be. Furthermore, if the usage of the battery is not managed well the life of the battery diminishes and it will need to be replaced more frequently.

Due to the variable nature of the energy available from the renewable sources there may be occasions when the battery and loads may not be able to utilise all the energy available and a surplus energy condition may exist.

Prior art refrigeration control systems do not have an optimal usage of surplus energy.

Neither do existing systems permit a use of surplus energy available in the system.

Thus, there is a need for an energy management, which addresses one or more inefficiency issues. There is also a need for optimal utilization of surplus energy available in the system.

Object of the invention

It is thus the object of present invention to provide energy management and optimisation of a refrigeration system to use surplus solar energy and / or extend the life of a battery. In particular, it is an object to provide such a solution for freezers or coolers.

Summary of the invention

In a first aspect, the invention relates to an apparatus configured to manage energy consumption of a freezer or cooler to match available solar energy, the apparatus comprising a controller connectable to associated components in the freezer or cooler, said controller comprising a measuring logic configured to measure parameters selected from the group consisting of current from a solar array, ambient temperature, freezer temperature and battery temperatures, battery voltage and battery current, and availability of an external power supply or a combination thereof,

a calculating logic configured to determine availability of excess solar energy beyond that required to maintain the freezer or cooler at its normal set temperature,

a memory having the ability to store values and external inputs values, and wherein

said controller is configured to control the temperature set point of the freezer or cooler, to utilise solar energy that is available in excess of that required to maintain normal operation of the freezer or cooler in order to lower the temperature set point of the freezer or cooler.

The measuring logic may advantageously, also be configured to measure the parameters time of day and/or date.

The present invention allows reducing the size of battery needed or extending the life of the battery, by reducing the lower level of discharge it is subjected to. This is possible due to the detection of that surplus energy conditions and releasing of sensible heat stored, in preference to using chemical (electrical) energy stored in the battery. Furthermore, by lowering the temperature set point the invention allows for the storing of more energy into the freezer or cooler.

As an alternative or in addition to using a proportion of the surplus energy to cool the freezer or cooler to below an operation set point, the surplus energy may be used to cool the batteries below the external ambient temperature thus extending their operating life. In a preferred embodiment of the invention, the controller comprises means for switching and controlling electrical power in response to the logics decisions in order to receive and send instructions to control of the temperature set point of the freezer or cooler. The benefit of this is to make use of surplus energy by storing it as sensible energy in the freezer or cooler.

It has surprisingly been found that the effect obtained allowed for an increased life of the battery by reducing the average daily lower levels of discharge of the battery and preventing deep discharge and enabling more frequent full recharge and equalisation to be performed.

In a second aspect, the invention relates to a method of managing energy consumption of a freezer or cooler to match available solar energy, the method comprising

a) providing an apparatus according to claims 1 to 13, b) determining if the freezer or cooler is connected to an external power supply,

c) determining if the time is within a configured time of day window for lowering the freezer or cooler set point or initiating battery cooling operation, d) determining if the battery, is charging at a high state of charge, from the battery voltage and current,

e) determining if an external power supply is connected or not, and if the battery is in absorption charge, and the time of day is within the configured window, f) controlling the freezer or cooler set point to lower the freezer temperature , and wherein g) steps b to f are repeated and if the conditions of b to f are no longer valid, restoring the freezer or cooler set point to its normal setting. Brief description of the drawings

Embodiments of the present invention will now be described further, with reference to the drawings, in which:

Figure 1 illustrates schematically the main functional components of the apparatus according to the invention configured to manage energy consumption of a freezer or cooler to match available solar energy,

Figure 2 illustrates schematically a solar powered system comprising an apparatus according to the invention.

Figure 3 illustrates schematically available solar power and temperature of the freezer or cooler, including a reduction of the freezer or cooler set point.

Figure 4, is a freezer or cooler set booster control flow chart for the change of the freezer or cooler set point.

Figure 5, illustrate schematically a cooled battery compartment including vents to allow venting of the compartment.

Detailed Description of the Invention

The invention relates to an apparatus configured to manage energy consumption of a freezer or cooler to match available solar energy and extending the life of a battery used in the freezer or cooler.

The apparatus comprises a controller connectable to associated components in the freezer or cooler. The associated components may be selected from a group consisting of freezer temperature set point, freezer compressor speed, battery cooling device, fans, electrically actuated ventilation flaps or grills, and a combination thereof.

The controller comprises a measuring logic is configured to measure parameters selected from the group consisting of current from a solar array, ambient temperature, freezer temperature and battery temperatures, battery voltage and battery current, and availability of an external power supply or a combination thereof. The group from which the parameters are selected may also comprise time of day and/or date.

The calculating logic configured to determine availability of excess solar energy beyond that required to maintain the freezer or cooler at its normal set temperature.

The controller further comprises a memory having the ability to store values and external inputs values, like amount of current from a solar array, ambient temperature, freezer temperature and battery temperatures, battery voltage and battery current, and availability of an external power supply, time of day and date, weather forecasts for use by the calculating logic.

The present invention provides the possibility to determine and utilize the surplus energy of the solar energy that is in excess of that required to maintain normal operation of the freezer and control the freezer or cooler set point in order to cool the freezer or cooler to a lower temperature. The advantage of having a lower temperature in the freezer or cooler is that the mass of the internal elements of the freezer and its contents act as an additional energy store, storing energy as sensible heat. Once the freezer or cooler set point is restored to its normal setting this sensible heat is slowly released but will maintain the temperature below the normal setpoint for some time without additional external energy input thus extending the time until its necessary to draw energy from other sources such as the battery .

If the apparatus according to the invention only provides a cooling of the freezer below normal operation set point and not cooling of the battery by means of the surplus energy of the solar array then the measuring logic is preferably configured to measure at least the current from the solar power array, the battery voltage and the battery current. Optionally, the time of the day and/or optionally, external supply of energy may be parameter which the measuring logic measure.

On the other hand if the apparatus according to the invention provides a cooling of the freezer below normal operation set point and cooling of the battery by means of the surplus energy of the solar array then the measuring logic is preferably configured to measure at least the current from the solar power array, the temperature of the freezer, battery temperature, and available external power supply. Optionally, the measuring logic may measure the ambient temperature at the freezer or cooler location .

In the present context, a measuring logic is an analog and digital circuitry interfaced to sensors and external inputs to measure and store values associated with measured parameters on a continuous or periodic basis.

In the present context, a calculating logic is a software operational on a computer or microprocessor to perform calculations and algorithms using the measured and stored values and external inputs to calculate the values of the measured. In the present context, the state of charge of a battery is referring to the percentage of the battery being charged. A high stage of charge means that the battery is at least 90% charged.

The controller may comprise means for switching and controlling electrical power in response to the logic decisions. These means may be in the form of hardware or software switches or analog control for example variable voltage, current, resistance, or pulse width modulation.

In a preferred embodiment of the invention, the controller comprises a processor for running software associated with the measuring and calculating logics. This allows the functions to be performed in software. The controller may also be implemented hardware in discrete logic gates, a field programmable gate array (FPGA), a programmable Interface Controller or similar electronic circuity.

Advantageously, the instruction from the controller relates to the operation of freezer or cooler associated components selected from a group consisting of freezer temperature set point, freezer compressor speed, battery cooling device, fans, electrically actuated ventilation flaps or grills, and a combination thereof.

In a preferred embodiment of the invention, the calculating logic is configured to lower the freezer or cooler temperature set point enabling the storage of additional energy as sensible heat in the freezer body and contents.

As will be known to the skilled person sensible heat is heat exchanged by a body or thermodynamic system in which the exchange of heat changes the temperature of the body or system, and some macroscopic variables of the body or system, but leaves unchanged certain other macroscopic variables of the body or system, such as volume or pressure. The other type of heat is latent heat. Latent and sensible heat are types of energy released or absorbed. Latent heat is related to changes in phase between liquids, gases, and solids. Sensible heat is related to changes in temperature of a gas or object with no change in phase.

In a particular preferred embodiment of the invention the apparatus comprises a battery cooling logic configured to determine the battery temperature to assess if an opportunity for battery cooling exists.

For the cooling of the battery the apparatus according to the invention may comprise a battery compartment and controlling means for lowering the temperature in the battery compartment. The cooling may e.g. be done by using the cold circuit from the compressor to cool down the battery compartment.

Alternatively or additionally, the lowering of the temperature in the battery compartment is done by the controlling means controlling an opening and closing of vents and or operating fans in the freezer to allow external ambient air to circulate through the battery compartment.

Cooling with external air may be done when the ambient air is colder than battery temperature. For example, if the freezer is in direct sun and the battery has a temperature of 60°C, the ambient temperature may still be 25 to 35°C and be able to cool the battery if ventilated through the battery compartment.

Thus, in a preferred embodiment of the invention the apparatus comprises controlling means for controlling, opening and closing of vents and or operating fans in the freezer or cooler to allow air from the internal freezer or cooler compartment to circulate through the battery compartment.

Additionally, battery cooling may be achieved by utilising solar energy that is available in excess of that required to maintain normal operation of the freezer or cooler to operate an additional compressor or cooling device to circulate cool air within the battery compartment.

Preferably, the controller logic is configured to lower the battery temperature enabling the storage of additional energy as sensible heat in the battery mass to optimise the battery energy storage and extend battery life.

Alternatively or additionally, the freezer or cooler boost cooling or battery cooling operation is combined with eutectic or phase changing materials to store heat energy as latent heat in addition to sensible heat.

In a preferred embodiment of the invention the apparatus according to the invention the calculating logics are configured to periodically recalculate the prediction ( s ) . This allows a periodic check of the validity and accuracy of the values, which form the basis for the controller operation. For example, there may be surplus energy, then a big storm cloud comes in. Periodic checking also allows for the system to stabilise and not be disrupted by short duration effects, like a bird casting a shadow over the array for a few seconds.

In a preferred embodiment of the invention where both the freezer or cooler boost cooling and battery cooling operation are configured, and the surplus energy is insufficient to both boost cool the freezer or cooler and cool the batteries simultaneously the control logic may compare the absolute battery temperature to a preferred battery temperature and if the temperature difference is greater than a configured threshold, prioritise battery cooling operation over freezer or cooler boost cooling. This embodiment of the invention a sharing of the energy between the boost cooling of the freezer or cooler and the cooling of the battery or batteries is possible.

The apparatus may comprise sensors capable of detecting one or more parameters selected from the group consisting of; battery voltage and battery current, availability of a grid supply, external ambient temperature, freezer internal temperature, battery temperature, solar current and time of day.

The apparatus according to the invention may also comprises a battery logic configured to determine if an opportunity for battery absorption or equalisation exists and assess need from cell balance and state of charge history. This allows the keeping of a log of battery usage and makes it is possible to look for opportunities to perform absorption and equalisation charges based on the predicted energy flows. A result of this is an extended life of the battery.

The invention also relates to a method of managing energy consumption of a freezer or cooler to match available solar energy, the method comprising

c) determining if the time is within a configured time of day window for lowering the freezer or cooler set point or initiating battery cooling operation, d) determining if the battery, is charging at a high state of charge, from the battery voltage and current, e) determining if an external power supply is connected or not, and if the battery is in absorption charge, and the time of day is within the configured window, f) controlling the freezer or cooler set point to lower the freezer temperature , and wherein g) steps b to f are repeated and if the conditions of b to f are no longer valid, restoring the freezer or cooler set point to its normal setting.

The battery may have a battery management system supporting communication, by interrogating the battery management system to report the state of charge.

In another embodiment the invention relates to a method of managing energy consumption of a freezer or cooler to match available solar energy, the method comprising

h) providing an apparatus according to claims 1 to 13, i) determining if the freezer or cooler is connected to an external power supply,

j) determining if the time is within a configured time of day window for freezer boost or battery cooling operation,

k) determining if the battery is charging in a bulk charge state from the battery voltage and current l) determining if an external power supply is not connected, the battery is in absorption charge, the time of day is within the configured window, and if the battery temperature is higher or lower than the external ambient temperature, controlling motorised flaps, fans or additional cooling equipment to lower the temperature of the batteries in the battery compartment, and wherein steps h to i are repeated and if the conditions of h to i are no longer valid, closing the motorised flaps and switching off any fans or additional battery cooling equipment.

In a preferred embodiment of the invention, the apparatus and method the solar freezer or cooler is operated off the grid. However, the apparatus and method of the invention the solar freezer or cooler may be operating on a grid supply on a temporary basis before it is deployed off grid into solar only operation, for a period before it is disconnected from the grid supply, a boost function may be implement. This could be for just boosting the freezer or cooler, or for the boosting and battery cooling functions combined. This function advantageously enable once the battery is "substantially" recharged and for sufficient time before the grid supply is disconnected to allow the boost cooling to reach the new set point (and recharge Eutectic material if present) . Advantageously, this boost cooling may be up to two hours or longer.

When the freezer or cooler is be operated on a grid supply on a temporary basis before it is deployed off grid into solar only operation, the method according to the invention is preferably a method of managing energy consumption of a solar freezer or cooler, wherein the method comprising

c) determining if the battery, is charging at a high state of charge, from the battery voltage and current, or other means to estimate battery state of Charge

d) determining if an input request to enable boost operation has being received, e) optionally determining if the time is within a configured time of day window for lowering the freezer or cooler set point or initiating battery cooling operation,

f) controlling the freezer or cooler set point to lower the freezer temperature , and wherein g) steps b to e are repeated and if the conditions of b to e are no longer valid, restoring the freezer or cooler set point to its normal setting.

The above-described method may also be combined with the methods of claims 15, 16 or 17.

The apparatus according to the invention may furthermore comprise a defrosting logic configured to predict the need for a defrost cycle and inform an operator and/or a retail operation centre accordingly to avoid freezer or cooler efficiency degradation. The defrosting of the freezer or cooler when required improves its efficiency and reduces its energy consumption .

Examples

Fig. 1 illustrates schematically the main functional components of the apparatus according to the invention. The apparatus is configured to manage energy consumption of a freezer or cooler to match available solar energy,

In Fig. 1 the controller is a software enabled system controller which is connected to associated components and has a measuring logic measuring parameters of time, date, availability of grid or external power supply, current from a solar array, battery voltage and battery current, ambient temperature, freezer temperature and battery temperatures. The controller has a calculating logic configured determining availability of excess solar energy beyond that required to maintain the freezer or cooler at its normal set temperature. The controller also has a memory having the ability to store values and external inputs values.

The controller is configured to control the temperature set point of the freezer or cooler, to utilise solar energy that is available in excess of that required to maintain normal operation of the freezer or cooler in order to lower the temperature set point of the freezer or cooler. Based on the calculation of the calculating logic, the controller sends instructions to the operation of freezer or cooler associated components about freezer temperature set point, freezer compressor speed. Furthermore, for the cooling of the battery the controller sends instructions to operation of battery cooling circuits or fans e.g. electrically actuated ventilation flaps or grills.

Figure 2 illustrates schematically a solar powered system comprising an apparatus according to the invention. The PV panels convert light to Direct Current (DC) electrical power. This is fed to the charge controller which is a DC to DC converter that converts the variable input voltage form the PV array to the voltage necessary to charge the battery and supply the refrigeration compressor and other loads. The freezer or cooler system passes compressed gas through a condenser and evaporator in a manner that will be familiar by those skilled in the art. The microprocessor controls the duty cycle and speed of the compressor in response to the inputs from various sensors to achieve the desired level of cooling and toe maintain the temperature in the freezer or cooler compartment at the desired level Figure 3 illustrates schematically available solar power and temperature of the freezer or cooler, including a reduction of the freezer or cooler set point.

The PV array converts light into DC electricity using semiconductors that exhibit the photovoltaic effect. Multiple semiconductor elements are combined in series and parallel combinations to produce higher voltages and currents. The power available for the array is dependant on the light levels, temperature, efficiency and load levels, in order to maximise power under any given environmental conditions the array is typically connected to a maximum power point tracking converter

Surplus energy is available, when the PV input power exceeds the power needed to charge the battery and operate the freezer. Note that battery charge acceptance typically falls off at high states of charge of the battery so that the battery is still slowly charging during this time. The present invention preferably starts to make use of the surplus energy from the PV input when the battery is 90% charged.

Figure 4, is a freezer or cooler boost control flow chart for the change of the freezer or cooler temperature set point. The flow chart shows the method of managing a freezer or cooler to match available solar energy.

The chart follows the steps of

a) determining if the freezer or cooler is connected to an external power supply,

b) determining if the time is within a configured time of day window for lowering the freeze or cooler set point or initiating battery cooling operation,

c) determining if the battery, is charging at a high state of charge, from the battery voltage and current, d) determining if an external power supply is connected or not, and if the battery is in absorption charge, and the time of day is within the configured window, if confirmed

e) controlling the freezer or cooler set point to lower the freezer temperature ,

f) steps a) to e) are repeated and if the conditions of a) to e) are no longer valid, restoring the freezer or cooler set point to its normal setting. Figure 5, illustrates schematically a cooled battery compartment including vents to allow venting of the compartment.

It should be understood that there are various changes and modifications to the presently preferred embodiments described herein which will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims .

Claims

1. Apparatus configured to manage energy consumption of a freezer or cooler to match available solar energy, the apparatus comprising

a controller connectable to associated components in the freezer or cooler, said controller comprising a measuring logic configured to measure parameters selected from the group consisting of current from a solar array, ambient temperature, freezer temperature and battery temperatures, battery voltage and battery current, and availability of an external power supply or a combination thereof, a calculating logic configured to determine availability of excess solar energy beyond that required to maintain the freezer or cooler at its normal set temperature, a memory having the ability to store values and external inputs values, and wherein said controller is configured to control the temperature set point of the freezer or cooler, to utilise solar energy that is available in excess of that required to maintain normal operation of the freezer or cooler in order to lower the temperature set point of the freezer or cooler .

2. Apparatus according to claim 1, wherein the controller comprises means for switching and controlling electrical power in response to the logic decisions in order to receive and send instructions to control the temperature set point of the freezer or cooler.

3. Apparatus according to claims 1 or 2, wherein the controller comprises a processor for running software associated with the measuring and predicting logics.

4. Apparatus according to any of the preceding claims, wherein instruction from the controller relates to the operation of freezer or cooler associated components selected from a group consisting of freezer temperature set point, freezer compressor speed, battery cooling device, fans, electrically actuated ventilation flaps or grills, and a combination thereof.

5. Apparatus according to any of the preceding claims, wherein the calculating logic is configured to lower the freezer or cooler temperature set point enabling the storage of additional energy as sensible heat in the freezer body and contents.

6. Apparatus according to any of the preceding claims, wherein the apparatus comprises a battery cooling logic configured to determine the battery temperature to assess if an opportunity for battery cooling exists.

7. Apparatus according to any of the preceding claims wherein the apparatus comprises a battery compartment and controlling means for lowering the temperature in the battery compartment.

8. Apparatus according to claim 7, wherein the lowering of the temperature in the battery compartment is done by the controlling means controlling an opening and closing of vents and or operating fans in the freezer to allow external ambient air to circulate through the battery compartment.

9. Apparatus according to any of the preceding claims, wherein the apparatus comprises controlling means for controlling, opening and closing of vents and or operating fans in the freezer or cooler to allow air from the internal freezer or cooler compartment to circulate through the battery compartment .

10. Apparatus according to any of the preceding claims where battery cooling is achieved by utilising solar energy that is available in excess of that required to maintain normal operation of the freezer or cooler to operate an additional compressor or cooling device to circulate cool air within the battery compartment.

11. Apparatus according to any of the preceding claims, wherein the controller is configured to lower the battery temperature enabling the storage of additional energy as sensible heat in the battery mass to optimise the battery energy storage and extend battery life.

12. Apparatus according to any of the preceding claims where freezer or cooler boost cooling or battery cooling operation is combined with eutectic or phase changing materials to store heat energy as latent heat in addition to sensible heat.

13. Apparatus according to any of the preceding claims, wherein the calculating logics are configured to periodically recalculate the prediction ( s ) .

14. Apparatus according to any of the preceding claims, wherein the apparatus comprises sensors capable of detecting one or more parameters selected from the group consisting of; battery voltage and battery current, availability of a grid supply, external ambient temperature, freezer internal temperature, battery temperature, solar current and time of day.

15. A method of managing energy consumption of a freezer or cooler to match available solar energy, the method comprising

j) determining if the time is within a configured time of day window for lowering the freezer or cooler set point or initiating battery cooling operation, k) determining if the battery, is charging at a high state of charge, from the battery voltage and current,

l) determining if an external power supply is connected or not, and if the battery is in absorption charge, and the time of day is within the configured window, m) controlling the freezer or cooler set point to lower the freezer temperature , and wherein

n) steps b to f are repeated and if the conditions of b to f are no longer valid, restoring the freezer or cooler set point to its normal setting.

16. A method according to claim 15, wherein the battery has a battery management system supporting communication, by interrogating the battery management system to report the state of charge.

17. Method of managing energy consumption of a freezer or cooler to match available solar energy, the method comprising

o) providing an apparatus according to claims 1 to 13, p) determining if the freezer or cooler is connected to an external power supply,

q) determining if the time is within a configured time of day window for freezer boost or battery cooling operation,

r) determining if the battery is charging in a bulk charge state from the battery voltage and current s) determining if an external power supply is not connected, the battery is in absorption charge, the time of day is within the configured window, and if the battery temperature is higher or lower than the external ambient temperature, controlling motorised flaps, fans or additional cooling equipment to lower the temperature of the batteries in the battery compartment, and wherein

steps h) to i) are repeated and if the conditions of h) to i) are no longer valid, closing the motorised flaps and switching off any fans or additional battery cooling equipment .

18. A method of managing energy consumption of a solar freezer or cooler, the method comprising

t) providing an apparatus according to claims 1 to 13, u) determining if the freezer or cooler is connected to an external power supply,

v) determining if the battery, is charging at a high state of charge, from the battery voltage and current, or other means to estimate battery state of Charge w) determining if an input request to enable boost operation has being received,

x) optionally determining if the time is within a configured time of day window for lowering the freezer or cooler set point or initiating battery cooling operation,

y) controlling the freezer or cooler set point to lower the freezer temperature , and wherein

z) steps b to e are repeated and if the conditions of b to e are no longer valid, restoring the freezer or cooler set point to its normal setting.