Carbon emission reduction for chiller / heat pump systems through transition temperature setpoints

Abstract

The invention relates to carbon emission reduction of a chiller / heat pump system by transforming temperature setpoints, and specifically, a building chiller / heat pump system includes a chiller / water pump system for supplying a conditioned fluid to vary the temperature of air delivered into a building. The cooler / heat pump system is provided with controls to achieve a desired setpoint of air delivered into the building. The control is programmed to receive a prediction of an expected emission level in energy to be delivered to drive the chiller / heat pump system. The control is programmed to change the setpoint such that the energy level required to operate the chiller / heat pump system to achieve the setpoint will drop when the expected emission level increases, while the setpoint will be adjusted in the opposite direction when the expected emission drops. A method is also disclosed.

Description

Technical Field

[0001] The present application relates to a method and control operable to vary a building chiller / heat pump system temperature set point based on the relative "dirty / clean" nature of the available electricity. Dirty or clean refers to the emissions associated with the production of such electricity, including the level of carbon dioxide release or other pollutants. Background Art

[0002] Most modern buildings are equipped with a chiller / heat pump system. A chiller / heat pump system can be operated to cool the ambient air during hot times and to provide heat during cooler times. One such system is a so-called chiller or heat pump. In a chiller / heat pump system, water is heated or cooled by a refrigerant cycle and supplied through a radiator to heat or cool the air in the building.

[0003] Currently, buildings account for approximately 33% of the world’s annual carbon emissions. In a typical commercial building, chiller / heat pump systems account for 30-50% of this total.

[0004] New buildings could be equipped with more energy-efficient chiller / heat pump systems. However, retrofitting existing chiller / heat pump systems in a similar manner would be prohibitively expensive. Summary of the invention

[0005] In a characteristic embodiment, a building chiller / heat pump system includes one or more chillers / heat pumps for supplying conditioned fluid to change the temperature of air delivered to a building. The chiller / heat pump system is provided with controls to achieve a desired set point for the air delivered to the building. The controls are programmed to receive a forecast of grid power expected to be generated and an emissions level embedded in that power to be delivered to drive the chiller / heat pump system. The controls are programmed to change the water temperature set point so that when the expected emissions level increases, the energy level required to operate the chiller / heat pump system to achieve the set point will decrease, and when the expected emissions level decreases, adjust the set point in the opposite direction while maintaining the temperature comfort level in the conditioned building or zone within predetermined boundaries.

[0006] In another embodiment according to the previous embodiment, when the available energy is relatively dirty and the chiller / heat pump system is operated in cooling mode, the water temperature set point is increased for a period of time, and if the chiller / heat pump is operated in heating mode, the set point is decreased for a period of time.

[0007] In another embodiment according to any of the preceding embodiments, when the water temperature set point is changed in the opposite direction, it is changed to an amount that exceeds the actual desired set point at that time.

[0008] In another embodiment according to any of the preceding embodiments, the prediction is a prediction of emissions per unit of energy.

[0009] In another embodiment according to any of the previous embodiments, the chiller / heat pump system is a system of one or more water chillers or heat pump devices, and the control varies the temperature of the water leaving the chillers or heat pumps to achieve a desired temperature within the building.

[0010] In another embodiment according to any of the previous embodiments, the change in the water temperature set point occurs across multiple cycles during the extended period of relatively dirty power.

[0011] In another embodiment according to any of the preceding embodiments, when the water temperature set point is changed in the opposite direction, it is changed to an amount that exceeds the actual desired set point at that time.

[0012] In another embodiment according to any of the preceding embodiments, the prediction is a prediction of an emissions quantum to be used by the system to deliver an acceptable level of comfort.

[0013] In another embodiment according to any of the previous embodiments, the chiller / heat pump system is a water chiller and the control varies the temperature of the water to achieve a desired set point for air delivered to the building.

[0014] In another embodiment according to any of the previous embodiments, the change in the water temperature set point occurs across multiple cycles during the extended period of relatively dirty power.

[0015] In another feature embodiment, a method of operating a chiller / heat pump system provides a conditioned fluid to change the temperature of air delivered to a building. The chiller / heat pump system is provided with a control to achieve a desired set point for the air delivered to the building. The control receives a prediction of an expected level of emissions in the energy to be delivered to drive the chiller / heat pump system. The control changes the water temperature set point so that when the emissions level increases, the energy level required to operate the chiller / heat pump system to achieve the set point will decrease, and when the expected emissions level decreases, the set point is adjusted in the opposite direction.

[0016] In another embodiment according to any of the previous embodiments, when available energy is dirty and the chiller / heat pump system is operating in cooling mode, the water temperature set point is increased for a period of time, and if the chiller / heat pump is operating in heating mode, the set point is decreased for a period of time.

[0017] In another embodiment according to any of the preceding embodiments, when the water temperature set point is changed in the opposite direction, it is changed to an amount that exceeds the actual desired set point at that time.

[0018] In another embodiment according to any of the preceding embodiments, the prediction is a prediction of an emissions rating per unit of energy.

[0019] In another embodiment according to any of the previous embodiments, the chiller / heat pump system is a water chiller and the control varies the temperature of the water to achieve a desired set point for air delivered to the building.

[0020] In another embodiment according to any of the previous embodiments, the change in the water temperature set point occurs across multiple cycles during the extended period of relatively dirty power.

[0021] In another embodiment according to any of the preceding embodiments, when the water temperature set point is changed in the opposite direction, it is changed to an amount that exceeds the actual desired set point at that time.

[0022] In another embodiment according to any of the preceding embodiments, the prediction is a prediction of an emissions rating per unit of energy.

[0023] In another embodiment according to any of the previous embodiments, the chiller / heat pump system is a water chiller and the control varies the temperature of the water to achieve a desired temperature of the air delivered to the building.

[0024] In another embodiment according to any of the previous embodiments, the change in the water temperature set point occurs across multiple cycles during the extended period of relatively dirty power.

[0025] The various features and advantages of at least one disclosed example embodiment will become apparent to those skilled in the art from the following detailed description.The drawings that accompany the detailed description can be briefly described as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A chiller / heat pump system is shown schematically.

[0027] Figure 2 A projection of the marginal operating emission rate is shown.

[0028] Figure 3A The disclosed control is illustrated using energy projection rate.

[0029] Figure 3B Similar to Figure 3A , but shows a similar situation when the chiller / heat pump system is operated in heating mode.

[0030] Figure 3C Yet another situation during cooling mode is shown.

[0031] Figure 4 is a flow chart according to the present disclosure.

[0032] Figure 5 is a block diagram of the model predictive control component. DETAILED DESCRIPTION

[0033] Figure 1 A building chiller / heat pump system 20 is schematically shown. A building 21 is schematically shown as receiving the system 20. Of course, as is known, much of the system 20 may actually be located outside of the building 21. The system 20 has a heat exchanger 22 through which water passes to exchange heat with air at 24 to be delivered into the building 21. In the disclosed embodiment, the chiller / heat pump system 20 is a water chiller, and water is the working fluid in the heat exchanger 22.

[0034] If the chiller / heat pump system 20 is operating in a cooling mode, the water passing through the heat exchanger 22 is relatively cool and it cools the air delivered to the building 21 at 24. Alternatively, during heating operation, the water delivered to the heat exchanger 22 is relatively hot. The details of the water chiller and its operation in heating and cooling modes may be as known and do not form part of the present disclosure.

[0035] The second heat exchanger 26 is associated with a refrigerant system 27 to heat or cool the water before it is delivered to exchange heat with the air at the element 24. The refrigerant system 27 includes a compressor 28, a heat exchanger 26, an expansion device 30, and a second heat exchanger 32. A fluid line 34 selectively delivers fluid to heat or cool the refrigerant in the heat exchanger 32. The control 19 is schematically shown and controls the refrigerant system in such a way that the temperature of the water delivered to the heat exchanger 22 is at a desired "set point" for the air delivered through the element 24 into the building 21.

[0036] Again, the operation of such a system is known.

[0037] Recently, third-party data providers are providing information known as the Marginal Operating Emissions Rate (“MOER”). Figure 2 An example of what a MOER might look like is shown. Shown is a graph of emissions quotas over time. It is known that throughout the day, and across different seasons, the electricity supply system will rely on fossil fuels ("dirty") in a certain proportion and on more renewable or green energy ("clean") when available. For example, wind, nuclear or solar power is used to supplement fossil fuels.

[0038] However, the proportion of “clean” energy will vary depending on the availability of, for example, wind, nuclear, and solar power. Figure 2As shown in Figure 1, the quota at point X (midnight) may be relatively high. By noon the next day, the value at point Y may have dropped. By point Z, the value has increased again.

[0039] As shown at 1, the graph varies with time, season, etc., and further varies with the weather on a particular day. That is, as shown at 1, it is not always simply variable by hour of the day.

[0040] The present disclosure includes a control 19 that is programmed to respond to predicted high emission levels and adjust the set point of air delivered to the building 21. The control 19 is provided such as Figure 2 , which projects emissions over time.

[0041] Now, if Figure 3A As shown in FIG. 4 , the MOER at 40 is shown with a "dirty" growth spike at 42. The chilled water temperature set point 48 is increased at 49 to reduce the amount of dirty energy used. As it passes through point 42, the chilled water temperature set point is controlled to decrease at 50 to help the temperature in the building recover. When the set point initially changes in the opposite direction, it may change to a magnitude that exceeds the actual desired set point at the time. Once the MOER returns to its normal value 43, the chilled water temperature set point is increased at 51 back to the actual desired level.

[0042] By doing so, the overall carbon emissions from the chiller / heat pump system 20 are reduced. The reduction may not be huge, but over time, even a small reduction is valuable.

[0043] It will be appreciated that there is a great deal of thermal inertia in a chiller / heat pump system such as system 20, and therefore the air will not necessarily immediately become too warm even if the water temperature set point is increased at 49. Likewise, the increase need not be large.

[0044] It should be understood that Figure 3A The system 20 is shown operating in a cooling mode. It is also shown that the renewable power line 44 will include a dip at 46 to coincide with the spike 42.

[0045] Figure 3B It is shown how the control 19 is programmed to control the chiller / heat pump system 20 when operating in the heating mode. Now, when the spike 42 occurs, the water temperature set point 48 is decreased at 60, and when the MOER returns to its normal level at 43, or when the building temperature becomes unacceptable, the water temperature set point 48 is increased at 62. The increase 62 allows the building temperature to recover quickly. After a period of time, the set point then moves downward from point 62 to the actual desired set point 63.

[0046] Furthermore, it can be seen that the electrical power 44 has a drop 46 coinciding with the spike 42 , followed by an increase 64 .

[0047] Figure 3C Another control mode is shown. Here, the MOER 40 has a long spike 42. The water temperature set point line 48 then increases for a period of time at 149, then decreases at 150, and then moves cyclically between 149 and 150 until it returns to the desired level at 151. In this way, the occupants of the building 21 will not feel uncomfortable with the temperature in the ambient air when a long spike is expected. Note that Figure 3C Operation in cooling mode is shown, but the same occurs in heating mode.

[0048] Figure 4 is a flow chart of the disclosed method. In step 100, a chiller is operated.

[0049] At step 101, the times of clean and dirty energy are identified, such as from the MOER. Then, at step 102, the temperature set point is adjusted based on the relative clean and dirty energy over time.

[0050] Figure 5 200 is a block diagram of a model predictive control. Output 202 goes to the control 90 for the chiller / heat pump system. Predictor 204 receives the MOER information at 206. The predictor also receives the output and is able to calculate the carbon emissions and the actual room temperature that will be experienced in the building. Input 216 can be a reference temperature such as from the building.

[0051] The optimizer 208 is programmed to make decisions and operate the method as disclosed above. The optimizer 208 is provided with cost function information 210 and constraints (at 212). The constraints may be, for example, limits on how far a control may move a temperature from a desired temperature to a target temperature, and for how long. A building field or model 214 is also provided.

[0052] Although the system 200 is shown here as being separate from the control 19 , it may of course be built into the control 19 .

[0053] The model predictive control 200 is operable to calculate carbon emissions savings based on the methods and apparatus of the present disclosure. As a simple example, the predicted emissions per BTU of energy can be used, combined with the reduction in BTUs for each reduction over a period of time, to derive a carbon emissions quota saved by the method. Such savings can then be reported to various organizations that value carbon emissions savings. Although a basic algorithm for calculating carbon emissions savings is mentioned above, more improved algorithms can be developed.

[0054] Although a chiller is specifically disclosed, it will be appreciated that the same basic concepts can be extended to other types of chiller / heat pump systems, including, for example, standard air conditioning systems.

[0055] While embodiments of the present disclosure have been shown, those skilled in the art will recognize that modifications will fall within the scope of the present disclosure. For this reason, the following claims should be studied to determine the true scope and content of the present disclosure.

Claims

1. A building chiller / heat pump system comprising: a chiller / heat pump system for supplying a conditioned fluid to change the temperature of air delivered to a building, said chiller / heat pump system being provided with controls to achieve a desired water temperature set point to condition said air delivered to said building; as well as The control is programmed to receive a prediction of expected emissions levels in the energy that will be delivered to drive the chiller / heat pump system, and the control is programmed to vary the set point so that as the expected emissions level increases, the energy level required to operate the chiller / heat pump system to achieve the set point will decrease, and to adjust the set point in the opposite direction as the expected emissions decrease.

2. The system of claim 1, wherein: When the available energy is relatively dirty and the chiller / heat pump system is operating in cooling mode, the set point is increased for a period of time, and if the chiller / heat pump is operating in heating mode, the set point is decreased for a period of time.

3. The system of claim 2, wherein: When the set point is changed in the opposite direction, it is changed to an amount that exceeds the actual desired set point at that time.

4. The system of claim 2, wherein: The forecast is a forecast of emissions per unit of energy.

5. The system of claim 3, wherein: The change in the set point occurs across multiple cycles during an extended period of relatively dirty power.

6. The system of claim 2, wherein: The change in the set point occurs across multiple cycles during an extended period of relatively dirty power.

7. The system of claim 1, wherein: When the set point is changed in the opposite direction, it is changed to an amount that exceeds the actual desired set point at that time.

8. The system of claim 1, wherein: The forecast is a forecast of emissions per unit of energy.

9. The system of claim 1, wherein: The change in the set point occurs across multiple cycles during an extended period of relatively dirty power.

10. The system of claim 1, wherein: The control is programmed to calculate an amount of reduced emissions based on the adjustment of the set point.

11. A method of operating a chiller / heat pump system: operating a chiller / heat pump system for supplying conditioned fluid to change the temperature of air delivered to a building, the chiller / heat pump system being provided with controls to achieve a desired water temperature set point to condition the air delivered to the building; and The control receives a prediction of expected emissions levels in the energy that will be delivered to drive the chiller / heat pump system, and the control varies the set point so that as the emissions level increases, the energy level required to operate the chiller / heat pump system to achieve the set point will decrease, and adjusts the set point in the opposite direction as the expected emissions level decreases.

12. The method of claim 11, wherein: When the available energy is relatively dirty and the chiller / heat pump system is operating in cooling mode, the set point is increased for a period of time, and if the chiller / heat pump is operating in heating mode, the set point is decreased for a period of time.

13. The method of claim 12, wherein: When the set point is changed in the opposite direction, it is changed to an amount that exceeds the actual desired set point at that time.

14. The method of claim 12, wherein: The forecast is a forecast of emissions per unit of energy.

15. The method of claim 14, wherein: The change in the set point occurs across multiple cycles during an extended period of relatively dirty power.

16. The method of claim 12, wherein: The change in the set point occurs across multiple cycles during an extended period of relatively dirty power.

17. The method of claim 11, wherein: When the set point is changed in the opposite direction, it is changed to an amount that exceeds the actual desired set point at that time.

18. The method of claim 11, wherein: The forecast is a forecast of emissions per unit of energy.

19. The method of claim 11, wherein: The change in the set point occurs across multiple cycles during an extended period of relatively dirty power.

20. The method of claim 11, wherein: The control is programmed to calculate an amount of reduced emissions based on the adjustment of the set point.

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