U.S. patent application number 12/947342 was filed with the patent office on 2011-05-19 for optimizing the efficiency and energy usage of a geothermal multiple heat pump system.
Invention is credited to John Siegenthaler.
Application Number | 20110114284 12/947342 |
Document ID | / |
Family ID | 44010415 |
Filed Date | 2011-05-19 |
United States Patent
Application |
20110114284 |
Kind Code |
A1 |
Siegenthaler; John |
May 19, 2011 |
OPTIMIZING THE EFFICIENCY AND ENERGY USAGE OF A GEOTHERMAL MULTIPLE
HEAT PUMP SYSTEM
Abstract
A system and a method for operating the system is provided to
optimize heat exchange between a geothermal loop and a heat pump
load loop for heating and cooling a structure. In the method, the
flow rate through the earth loop is adjusted based on current
thermal demand of a heat pump array, so as to reduce the electrical
demand of the earth loop circulator when thermal demand from the
heat pump loop is low. The method adjusts the speed of the
earthloop circulator as required for the operating conditions of
the heat pumps and earth loop, thereby permitting efficient laminar
flow whenever possible, as long as thermal demand is met. The
system of this invention provides a compact module containing a
suitable digital data receiver and controller programmed to receive
temperature and flow data and to calculate the needed flow in each
loop to meet the thermal demand of the heat pump or pumps, and to
signal the earthloop pump, and optionally a load loop pump, to
operate at the necessary flow speed. Specifically, if flow in the
earth loop transitions from turbulent to laminar, this method
insures that the current thermal demand of the heat pumps is met,
and if not, increasing the earth loop circulator speed to deliver
the current thermal demand of the heat pumps.
Inventors: |
Siegenthaler; John; (Holland
Patent, NY) |
Family ID: |
44010415 |
Appl. No.: |
12/947342 |
Filed: |
November 16, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61262030 |
Nov 17, 2009 |
|
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Current U.S.
Class: |
165/45 |
Current CPC
Class: |
F24T 10/00 20180501;
Y02E 10/10 20130101; F24D 11/004 20130101; Y02B 30/70 20130101;
F24T 10/10 20180501; F28F 27/00 20130101; F25B 2500/19 20130101;
F25B 2700/13 20130101; F25B 30/06 20130101; F25B 2600/13 20130101;
F24T 2010/56 20180501 |
Class at
Publication: |
165/45 |
International
Class: |
F24J 3/08 20060101
F24J003/08 |
Claims
1. A method for efficiently operating a geothermal heat pump
system, the geothermal heat pump system comprising a geothermal
flow loop including an earth loop circulator and a heat pump load
flow loop, containing a load loop circulator, the two flow loop
systems being interconnected for fluid flow and direct heat
exchange at a flow interface; two temperature sensors and a flow
sensor at the entrance to and exit from each of the two loops, each
of the sensors providing a signal output; a watt transducer
operably connected to the circulators and providing a signal output
indicating amount of total power usage; and a data
receiver/controller operably connected to the sensors and watt
transducer to receive the data and provide control to the
circulators; the method comprising measuring fluid flow and inlet
and outlet temperatures at the flow interface in each of the two
flow loop systems, and measuring the total input wattage to the
load loop heat pump (Whp), and to the earth loop circulator
(Wcirc), calculating the instantaneous rate of heat transfer for
the earth flow loop as follows:
Q.sub.earthloop=(8.01.times.D.sub.earthloop.times.c.sub.earthloop).times.-
f.sub.earthloopin.times.(T.sub.earthloopin-T.sub.earthloopout)
Q.sub.load=instantaneous rate of heat transfer to load side of
hydraulic separator (Btu/hr) Q.sub.earthloop=instantaneous rate of
heat transfer on earth loop side of hydraulic separator (Btu/hr) D
is the density of the fluid flowing through the loops
(lb/ft.sup.3); c is specific heat of the fluid in the loops
(Btu/lb/.degree. F.); f is the fluid flow rate in the indicated
loop (gallons/minute); T is the temperature (.degree. F.) at the
inlet to, or the outlet from, the hydraulic separator in the
indicated loop; and 8.01 is a units constant. And calculating the
instantaneous rate of ea transfer for the heat pump load flow loop
as follows:
Q.sub.loadloop=(8.01.times.D.sub.loadloop.times.c.sub.loadloop)-
.times.f.sub.loadloop.times.(T.sub.loadloopin-T.sub.loadloopout)
Q.sub.loadloop=instantaneous rate of heat transfer to load side of
hydraulic separator (Btu/hr) D is the density of the fluid flowing
through the loops (1b/ft.sup.3); c is the specific heat of the
fluid in the loops (Btu/lb/.degree. F.); f.sub.loadloop is the
fluid flow rate in the load loop (gallons/minute); T is the
temperature (.degree. F.) at the inlet to, or the outlet from, the
hydraulic separator in the load loop; and 8.01 is a units constant;
balancing the equality of Q.sub.loadloop and Q.sub.earthloop, by
raising and lowering the flow through the earth loop, inverse to
the value of Q.sub.earthloop relative to the value of
Q1.sub.loadloop
2. The method of claim 1 further comprising determining and
optimizing the Coefficient of Performance ("COP") of the system
consisting of the earth loop plus the heat pump loop, in the
heating mode, in accordance with the following equation:
COP.sub.heating=(Q.sub.earthloop+(W.sub.circ+W.sub.hp).times.3.413)/((W.s-
ub.circ+W.sub.hp).times.3.413); when the heat pumps are in the
heating mode, or determining the COP of the "system" consisting of
the earth loop circulator plus heat pump, when the heat pumps are
in the cooling mode, in accordance with the following equation:
COP.sub.cooling=(Q.sub.earthloop-(W.sub.circ+W.sub.hp).times.3.413/((W.su-
b.circW.sub.hp).times.3.413); incrementally reducing the earth loop
circulator speed and again determining the system COP; if the
system COP is higher than before, repeating the incremental
reduction of earth loop circulator speed, each time calculating the
new system COP; if an incremental reduction in earth loop
circulator speed results in a drop in system COP, incrementally
increasing the earth loop circulator speed and again determining
the system COP; changing the earth loop circulator speed in the
direction that continually maximizes the system COP.
3. A method for operating a geothermal heat pump system so as to
optimize the coefficient of performance of the overall system, the
geothermal heat pump system of claim 1, wherein the interface
between the two loops is a hydraulic separator, which allows for
independently changing the flow in each loop.
4. A geothermal heat pump system comprising an earth loop and a
heat pump load loop for fluid flow, a compact module for providing
flow connection between the earth loop and the heat pump load loop
and for providing automated control of the fluid flow in each loop,
providing for optimization of operation and energy usage, the
compact module comprising: conduit connections for connecting each
of an earth loop flow system and a load loop flow system to an
inlet to and an outlet from the compact module, so that the two
loop flow systems can be interconnected for fluid flow and thereby
allowing direct heat exchange between the two loops; an
electronically controllable variable flow rate geothermal
circulator in fluid flow connection between the connections to the
two loops, and a ground loop flow system; and a data collecting,
controller system comprising a pair of temperature sensors in the
conduits leading to each of the conduit connections, a flow sensor
in a conduit located between the two loops, a watt transducer for
measuring the total electrical power used by the geothermal
circulator; and an electronic data collecting/controller in
operational connection with the temperature and flow sensors and
watt transducers to receive data and be capable of computing the
instantaneous heat transfer rate from the geothermal fluid flow
loop and from the load loop, and of computing the coefficient of
performance of the overall system when the module is connected
between a ground loop and a heat pump load loop; the electronic
data collecting/controller also being in operational connection
with the geothermal circulator to control the circulator and thus
the fluid flow through the ground loop conduit system, based upon
the computation of the optimum coefficient of performance for the
entire system and the instantaneous heat transfer rate between the
two loops.
5. The compact modular package for operating a geothermal heat pump
system in accordance with claim 4, the modular package further
comprising a hydraulic separator having two pairs of inlets and
outlets, the electronically controllable variable flow geothermal
circulator being in fluid flow connection with a first inlet to the
hydraulic separator and including a fluid flow connection for
connecting to a ground loop conduit system; a load loop circulator
in fluid flow connection with the second inlet to the hydraulic
separator and including a fluid flow connection for connecting to a
load loop conduit system which system is intended to include a
plurality of heat pumps; and a data collecting and controller
system comprising a pair of temperature sensors in conduits
intended to be in fluid flow connections to the ground loop conduit
system, one located adjacent to each of the inlet to and outlet
from the hydraulic separator, a flow sensor in the fluid flow
connection to a ground loop conduit system, and a watt transducer
for measuring the electrical power used by each of the earth loop
and load loop circulators; and an electronic data
collecting/controller in operational connection with the watt
transducers and temperature and flow sensors to receive data and
determine the instantaneous heat transfer rate from the ground loop
conduit system, and the coefficient of performance for the overall
system, and the electronic data collecting/controller also being in
operational connection with the geothermal circulator for
controlling the fluid flow through the ground loop conduit system
so as to maximize the coefficient of performance of the overall
system.
6. A method for efficiently operating a geothermal heat pump system
by optimizing the Coefficient of Performance ("COP") of the system
consisting of an earth loop and a heat pump loop, the geothermal
heat pump system comprising a geothermal flow loop including an
earth loop circulator, and a heat pump load flow loop, the two flow
loop systems being interconnected for fluid flow and direct heat
exchange at a flow interface; a temperature sensor and a flow
sensor at each of the entrance to and exit from the heat pump load
flow loop, each of the sensors providing a signal output; a watt
transducer operably connected to the earth loop circulator and
providing a signal output; and a data receiver/controller operably
connected to the sensors and watt transducer to receive the signal
outputs containing the temperature, flow and power usage data, and
to provide control to the earth loop circulator in accordance with
an algorithm for optimizing COP; the method comprising: calculating
the Coefficient of Performance ("COP") of the system consisting of
the earth loop plus the heat pump loop, in the heating mode, in
accordance with the following equation:
COP.sub.heating=(Q.sub.earthloop+(W.sub.circ+W.sub.hp).times.3.413)/((W.s-
ub.circ+W.sub.bp).times.3.413); or calculating the COP of the
"system" consisting of the earth loop plus the heat pump loop, when
the heat pumps are in the cooling mode, in accordance with the
following equation:
COP.sub.cooling=(Q.sub.earthloop-(W.sub.circ+W.sub.hp).times.3.413/((W.su-
b.circ+W.sub.hp).times.3.413); incrementally reducing the earth
loop circulator speed and recalculating the system COP; if the
system COP is higher than before, repeat the incremental reduction
of earth loop circulator speed, each time recalculating the new
system COP; if an incremental reduction in earth loop circulator
speed results in a drop in system COP, incrementally increasing the
earth loop circulator speed and recalculating the system COP;
changing the earth loop circulator speed in the direction that
continually maximizes the system COP.
7. A method for operating a geothermal heat pump system in
accordance with claim 6, so as to insure the heat transfer rates
between the two loops is in balance, the system further comprising
multiple heat pumps in the load loop, and flow connection means
between the earth loop and the load loop to provide direct heat
exchange and to allow for wide differences in flow rates between
the two loops; the method comprising in addition measuring fluid
flow and temperatures at the inlet and outlet to the load loop; and
calculating the instantaneous rate of heat transfer for the earth
flow loop as follows:
Q.sub.earthloop=(8.01.times.D.sub.earthloop.times.c.sub.earthloop).times.-
f.sub.earthloop.times.(T.sub.earthloopin-T.sub.earthloopout)
Q.sub.load instantaneous rate of heat transfer to load side of
hydraulic separator (Btu/hr) Q.sub.earthloop=instantaneous rate of
heat transfer on earth loop side of hydraulic separator (Btu/hr) D
is the density of the fluid flowing through the loops
(lb/ft.sup.3); c is specific heat of the fluid in the loops
(Btu/lb/.degree. F.); f is the fluid flow rate in the indicated
loop (gallons/minute); T is the temperature (.degree. F.) at the
inlet to, or the outlet from, the hydraulic separator in the
indicated loop; and 8.01 is a units constant; and calculating the
instantaneous rate of heat transfer for the heat pump load flow
loop as follows:
Q.sub.loadloop=(8.01.times.D.sub.loadloop.times.c.sub.loadloop)-
.times.f.sub.loadloop.times.(T.sub.loadloopin-T.sub.loadloopout)
Q.sub.loadloop=instantaneous rate of heat transfer to load side of
hydraulic separator (Btu/hr) D is the density of the fluid flowing
through the loops (lb/ft.sup.3); c is the specific heat of the
fluid in the loops (Btu/lb/.degree. F.); f.sub.loadloop is the
fluid flow rate in the load loop (gallons/minute); T is the
temperature (.degree. F.) at the inlet to, or the outlet from, the
hydraulic separator in the load loop; and 8.01 is a units constant;
balancing the equality of Q.sub.loadloop and Q.sub.earthloop, by
raising and lowering the flow through the earth loop, inverse to
the value of Q.sub.earthloop relative to the value of
Q1.sub.loadloop
8. The method of claim 7, wherein the system comprises a hydraulic
separator as the flow connection means between the earth loop and
the load loop.
Description
[0001] The priority of copending provisional application No.
61/262030, filed on Nov. 17, 2009, is hereby claimed and the
specification and description is hereby incorporated by reference
as if fully repeated herein.
BACKGROUND OF THE INVENTION
[0002] It is well-known to provide geothermal sources for systems
of heat pumps for the heating or cooling of residential, commercial
or industrial buildings. It has generally been assumed that the
ground loop circulation remains constant even when used with
multiple heat pump systems, where there can be widely varying
energy requirements depending upon the number of heat pumps
operating at any given time. For example, many office buildings are
substantially empty overnight, so that the heat pumps maintained in
operation during that period may vary by as much as a factor of 5,
or more, as compared to the heat pumps operated during a business
day. At times of low heat pump operation, the operation of the
geothermal loop was inefficient in the sense that unnecessary
energy was being expended in maintaining constant flow through the
geothermal loop. The prior art believed either that it was
necessary to maintain a high flow through the ground loop in order
to maintain turbulent flow; although some workers believed that the
primary limiting parameter for geothermal heat flow was the low
heat transfer rate through the plastic piping usually used.
Therefore, existing geothermal multiple heat pump systems provide
no means of reducing the electrical demand of the earth loop
circulator when a multiple heat pump array is operating at less
than full capacity.
BRIEF SUMMARY OF THE INVENTION
[0003] The present invention broadly provides an operating
geothermal heat pump system that allows the operator to optimize
the efficiency of the overall system by allowing variation of the
earth loop flow rate depending upon the load requirements of, e.g.,
a single variable heat pump system or a multiple heat pump load
loop, while optimizing circulator speed control in a multiple
geothermal heat pump system. The system controlled in accordance
with this invention avoids any problems that may be caused by
slowing the circulators so that laminar flow results in the
geothermal, or earth loop. The present invention comprises a
system, and a method of operating the system, that allows for the
optimization of the Coefficient of Performance of the system by
permitting continuous variation of the earth loop flow rate as
needed to balance the load requirement from the heat pump loop side
of the system. Furthermore, where the flow rates for each of the
two loops can be varied independently of each other as conditions
change, i.e., where there are separate circulators for each of the
earth loop and the heat pump loop. This invention provides a system
that avoids any problem that may arise from low instantaneous heat
transfer rate during laminar flow in the earth loop.
[0004] In accordance with the present invention, an efficiently
arranged automated, hardware system, programmed to follow an
operating algorithm for controlling the hardware system, is
provided which allows for the optimization of earth loop circulator
speed control in a geothermal heat pump system. One preferred
embodiment of the hardware of the system includes a direct heat
exchanger providing the interface separating the two loops, where
the load loop most preferably includes multiple heat pumps,
including a separate circulator on the load side. An indirect heat
exchanger could be used, in order to keep the fluid in the two
loops completely separate, when necessary due to the sensitivity
usually in the load, e.g., heat pump, loop with respect to the
fluid the earth loop. However, direct heat exchange as provided by,
e.g., a hydraulic separator, is preferred.
[0005] The hydraulic separator interconnects fluid flow through the
two loops, but allows for separate independent, unlimited fluid
flow adjustments of the ground loop flow and the heat pump, or
load, loop flow, in order to accommodate large changes in the heat
exchange rate required for the load loop while maintaining complete
and effective heat exchange between the two loops; for example,
where multiple heat pumps are provided in a single building or
group of buildings, and all or only one of the heat pumps may be
operating at any given time; depending upon the needs of the
building's occupants, the heat requirement of the load loop may be
20% or less than that required at full operation. The hydraulic
separator provides a volume for mixing and heat exchange of the
liquid flowing through the two loops with minimal pressure loss,
while permitting independently setting the flow rate through each
loop. The hydraulic separator also provides the added benefit of
optimally providing for the removal of air bubbles and any
suspended particulate material, and thus prevent buildup of these
impurities, which could compromise the efficient, long term
operation of the heat pump system.
[0006] In another preferred embodiment, especially useful where
only a single heat pump is present, there can be direct flow
through the two loops, without any intermediate interface. However,
in this circumstance, the automated system provides for the
optimization of the entire system, based upon the energy usage of,
or input to, the earthioop circulator and the energy output from
the heat pump system.
[0007] Many suppliers manufacture specially arranged hydraulic
separators, which also may contain coalescing medium to assist in
the removal of air microbubbles and suspended solid particles,
Alternatively, a similar effect is obtainable by the use of a wide
diameter vertical header, having centrally located along the length
of the header a pair of closely spaced T's.
[0008] The present invention also provides for a compact,
pre-packaged control and heat exchange module, that can be attached
between an earth loop and a heat pump load loop, by readily
available commercial pipe connections. The compact hardware package
of this invention preferably comprises an inter loop-direct heat
exchanger, such as the preferred hydraulic separator; piping
connections for connecting the two sides of the, e.g., hydraulic
separator, to the loops; a. ground loop variable flow circulator,
operatively connected to and controllable by a data controller, and
in fluid flow connection with the inlet or outlet from the ground
loop side of the inter loop-direct heat exchanger, e.g., the
hydraulic separator. Optionally, a load loop circulator, in fluid
flow connection with the inlet or outlet from the load loop side of
the inter loop-heat exchanger, can be especially useful where there
are a plurality of heat pumps in the load loop. A digital data
controller for the monitoring and controlling of the operation of
the geothermal heat pump system is provided, along with two sets of
temperature sensors, operatively connected to the data controller,
one set of temperature sensors being operatively connected to each
of the inlet to and outlet from the an interloop direct heat
exchanger, e.g., a hydraulic separator, for each of the earthloop
flow system and the load loop flow system, respectively, for
measuring the temperature of the fluid in the loops at each
location. There are also provided two flow rate sensors, such as
flow rate transducers, one located immediately upstream or
downstream from the hydraulic separator in the connections to each
of the load loop and ground loop, respectively, for measuring the
flow of fluid through each loop, and watt transducers for
continually measuring the power being used by the two loop
circulators and the heat pumps, all of these sensors and monitors
being operatively connected to the data controller, provide their
respective data to the data controller on a continual, real time
basis.
[0009] This compact package can efficiently and effectively monitor
and control the two loops and optimize the efficiency of the system
in accordance with the method of the present invention. The data
controller continuously receives temperature and flow rate data
from each of the temperature sensors and flow rate transducers, and
power usage from each watt transducer, to compute the instantaneous
heat exchange rate for each loop, and the power usage of the
system, and thus the Coefficient of Performance ("COP") of the
system. By varying the speed of the ground loop circulator in
accordance with the heat flow requirements of the load loop fluid,
it can maintain the required temperatures in the load loop system
while optimizing the energy use efficiency (COP) of the overall
system.
[0010] By measuring the electric usage of the heat pumps and the
heat pump circulator(s) and of the ground loop circulator(s), the
data controller can determine the power usage efficiency of the
overall operation of the system, as the heat pump load varies
during the day or in accordance with changing external factors.
[0011] In accordance with the method of this invention, the digital
data controller is programmed to use the data provided by the
several sensors and transducers to operate the geothermal heat pump
system in accordance with the algorithm of this invention, so as to
optimize the Coefficient of Performance ("COP") of the overall
system, and to optimize the respective flow rates of each of the
ground loop and load loop to achieve the most effective heat
exchange rates and operating conditions. By allowing for the
operation of the ground loop at laminar flow conditions, even for
short periods of time, the total energy usage by the circulators,
and therefore the overall efficiency of the system is improved.
[0012] The method of this invention is represented by algorithms
programmed into the data controller. The method of this invention
provides for balancing the instantaneous heat exchange rate between
the two loops by varying the speed of the ground loop circulator in
response to changes in the required instantaneous heat exchange
rate for the load loop so as to control the fluid flow rates of the
ground loop in order to optimize the overall efficiency; by
modifying the energy usages of the two loops so as to reduce the
total energy usage, overall efficiency is improved.
[0013] Most significantly, when operating a multiple heat pump
system in a single building, sharp changes in energy requirements
often occur in the operation of the system, such as when one or
more of the heat pumps in the loop will change status, i.e.,
between being on and being off, in response to conditions or
requirements in the building.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 depicts an example of suitable system hardware for
carrying out a preferred method of the present invention for a
single heat pump system;
[0015] FIG. 2 depicts an example of suitable system hardware for
carrying out a preferred method of the present invention for a
multi-heat pump system;
[0016] FIGS. 3-5 depict operation of an exemplary hydraulic
separator under different relative flows through the Primary
(ground) loop and Secondary (load loop);
[0017] FIG. 6 depicts a flow chart for the algorithm representing
the operation of, and the flow through, the system in accordance
with this invention where it is desired to optimize COP, in either
a single or multiple heat pump system; and
[0018] FIG. 7 depicts a flow chart for the algorithm representing
the operation of, and the flow through, the system in accordance
with this invention where it is desired to optimize heat exchange
and flow rate through each of the two loops, in a heat pump system
where the two loops are separated by an interloop direct heat
exchanger.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The operation of systems of this invention, in accordance
with the general depictions of FIGS. 1 and 2, is preferably carried
out using a digital controller 9, programmed in accordance with the
algorithms represented by the flow charts of FIGS. 6 and 7,
respectively. The program comprises a series of mathematical
equations that are used to calculate the various parameters of the
system, based upon data received by the controller 9 from the
several sensors, and pre-entered information, such as the known
properties of the circulating fluid, e.g., its specific heat and
density. The data received provide the bases for controlling the
earth loop circulator 8, by optimizing the flow through the earth
loop 101, which tends to enhance the coefficient of performance
(COP) of the overall system, and to maintain the instantaneous rate
of heat transfer (Q.sub.earthloop) on the earth, or Source, loop
side 101 of the hydraulic separator 1, at a value not less than the
heat transfer (Q.sub.output) for the load loop side 100. The
central compact system for achieving these results is exemplified
by the portion of each of FIGS. 1 and 2, outlined by the broken
lines, and designated by the numerals 210, 110, respectively.
[0020] The preferred compact, pre-packaged control and heat
exchange module, of the present invention, as depicted in FIG. 2,
preferably comprises a hydraulic separator, designated generally by
the numeral 1, most preferably including an air separator vent 21
and a coalescing medium, such as Pall rings, in the body of the
separator. The use of a coalescing medium reduces the potential for
gaseous cavitation by the elimination of air microbubbles from the
liquid in the two loops as the liquid passes through the hydraulic
separator, and by helping to remove micro particles of solids that
might create blockages elsewhere in the system, if not removed.
[0021] The hydraulic separator 1 also preferably provides at the
opposite, lower, end a trap 22 for the removal of coalesced solid
material passing through the hydraulic separator 1. This is
especially important in the system of the type shown in FIGS. 1 and
2, where the same liquid is passed through the source loop 101 and
through the heat pump load loop 100. Useful coalescing media
include such commercially available materials as Pall rings, in an
available Taco 4900 hydraulic separator, or the coalescing
media-contained in the 5900 FlexBalance and 5900 FlexBalancePlus
hydraulic separators, all from Taco, Inc.
[0022] The compact control and heat exchange module 210 further
includes the variable flow ground loop circulator 8 and the heat
pump loop circulator 13, and all necessary piping, valving, and
control components, as well as the necessary fluid flow line
connection points for the external portions of each loop,
including, for example, to the ground loop and the heat pump load
loop, as well as to any expansion tank and fluid feeder, on the
ground loop side of the hydraulic separator. Such a module, which
can be packaged by a manufacturer, eliminates any onsite problems
of circulator sizing, sensor placement, wiring, and pipe sizing, as
such a pre-fabricated module can be specified by the design
engineer as the complete interface between the earth loop mains and
the mains of the heat pump load loop. The pre-fabricated module
would be manufactured for a specific performance range, dependent
upon the requirements of the load loop.
[0023] Most preferably, the hydraulic separator is sized, in
conformity with its anticipated use and the capacity of the
circulators, so that the maximum flow speed through the hydraulic
separator body is not greater than about 4 ft/sec.
[0024] As shown in FIG. 2, this modular system further includes the
data controller 9, the temperature sensors 3, 4, 6 and 7, the flow
rate sensors 2 and 5 and one or two watt transducers 31 and 32, for
measuring the power to the ground loop circulator and the primary
heat pump circulator, respectively; all of these sensors and data
providers usually being transducers. The sensors and transducers
preferably report the data digitally, either through wired
connections, especially in the packaged module, or wirelessly,
using for example, Bluetooth technology. A suitable data compiler
and controller is the iWorx platform, from Taco, Inc., which is
networkable, and can thus be used to operate and balance several
systems in different building locations. This can be significant
where it is desired to save overall electrical usage, especially in
locations where the total amount of electricity available to an
enterprise may be limited in high use times, by increased utility
rates. It can also be effective where there are several different
systems operating in the same building with competing or
complementary effects.
[0025] In addition, FIG. 2 includes a representation (in dotted
lines) of the wiring connections, identified by the numeral 15,
between the sensors and the data controller 9, and the control line
10 from the data controller 9, for controlling the earth loop
circulator in accordance with the algorithms of this invention. It
should be understood that the operating connections between the
sensors and the earth loop circulator and the data controller can
be wireless, for example using Bluetooth technology. However, when
the system is manufactured as a prefabricated compact module,
wireless connections would likely be an unnecessary added expense,
except if it is desired to also control the load side controller,
which can be hard-wired or connected wirelessly by, e.g.,
bluetooth.
[0026] In accordance with the algorithm of this invention, and as
shown in the flow chart of FIG. 6, when the data controller 9
receives a signal that the building requires heating or cooling the
heat pump circulator 13 and the earth loop circulator 8 are
started. The earth loop circulator 8 is preferably initially
started at 50% speed, and the data from the several data collecting
devices, i.e., the four temperature sensors 3,4,6,7, the two flow
rate transducers 2,5, and the energy usage of the circulators 8,13,
from the watt transducers 31,32, are received by the data
controller 9 (which can be, for example, a Taco iWorx networkable
monitoring and controller platform).
[0027] When the system is operating, the hydraulic separator 1
allows for independently variable flow rates through the earth loop
and the load loop, which comprises a multiple heat pump array. In
addition, the hydraulic separator allows for high performance,
continuous microbubble air separation, in both source loop and load
loop, which allows for more efficient circulator operation and
greatly reduces the potential for gaseous cavitation. Conventional
practice in smaller ground source heat pump systems is not to
provide any air separation in the earth loop. Larger commercial
systems may include air separators in the earth loop, but these are
often vortex separators that are not as efficient in gathering
microbubbles as would be a hydraulic separator equipped with
microbubble coalescing media (an example of such hardware is the
Taco 4900 hydraulic separator using Pall ring coalescing media).
The use of Pall rings and other coalescing media is well-known in
the art and by itself does not form part of this invention.
[0028] The hydraulic separator also allows for high performance and
continuous dirt separation in both the earth loop and load loop.
Given that much of the earth loop piping is joined in open
excavations, there is increased potential of dirt getting into
piping during installation. Conventional practice is to "purge"
earth loop piping at initial startup, but this short duration
process may not remove fine particles held in suspension, or those
clinging to inner surfaces of piping. Continuous dirt separation
would eventually capture this foreign material and allow it to be
easily removed from the system. (Again, a suitable example of such
hardware are the Taco 4900 or 5900 hydraulic separator, using Pall
ring or other coalescing media, useful for both gas and solid
coalescence,)
[0029] The load loop side 100 flow sensor 5 and two temperature
sensors 6,7 provide the data needed to calculate the instantaneous
rate of heat transfer required by the current operating condition
of a multiple geothermal heat pump array, for the load side of the
hydraulic separator. Similarly, the earth loop flow sensor 2 and
the two temperature sensors 3,4 provide the data needed to
calculate the instantaneous rate of heat transfer delivered from
the earth loop. Signals from the flow sensors 2,5 and two pairs of
temperature sensors 3,4 and 6,7 are acquired and processed by the
data controller 9, so that the controller 9 can compute the
instructions to the earth loop circulator 8 to speed up or slow
down, depending upon whether the rate of heat transfer on the load
side is greater or less than the rate on the earth loop side. The
load side circulator 13 may be either variable speed or fixed
speed.
[0030] It should be understood that this system can be used for any
large heat source or sink system in addition to an underground heat
exchange loop, such as a lake or other large body of surface
water.
[0031] As an example of hardware suitable to act as the electronic
controller is the Taco iWorx Control Platform, from Taco, Inc.
During operation of the system, the data controller is programmed
to continually compare the instantaneous rate of heat transfer on
the load side of the hydraulic separator to the instantaneous rate
of heat transfer on the earth loop side of the hydraulic
separator.
[0032] In the system of FIG. 2, if the instantaneous rate of heat
transfer on the earth loop side 101 of the hydraulic separator 21
is less than the instantaneous rate of heat transfer on the load
loop side 101 of the hydraulic separator 1, the speed of the earth
loop circulator 2 is increased, incrementally, as necessary, until
these rates of heat transfer are equalized or it is greater on the
earth loop side 100.
[0033] If the instantaneous rate of heat transfer on the earth loop
side 101 of the hydraulic separator 1 is greater than the
instantaneous rate of heat transfer on the load side 100 of the
hydraulic separator 1, the data controller 9 signals the earth loop
circulator 8 to incrementally reduce the flow rate through the
earth loop side 101 until it equalizes these heat transfer
rates.
[0034] By carrying out the algorithm illustrated by FIG. 6, the
system of FIG. 2 can be operated so as to maintain a substantially
equal instantaneous heat flow in the two loops, i.e., on both sides
of the hydraulic separator, and this allows reducing the flow
through the earth loop to the greatest degree feasible, including
dropping down to laminar flow rates, and thus conserving a
significant amount of energy. Although continuously maintaining
exactly equal flow rates may not be practical, by maintaining a
small .+-..DELTA.Q between the two loops, the same result can be
achieved.
[0035] Determine the instantaneous rate of heat transfer from the
earth loop using .DELTA.T and flow rate as follows:
Q.sub.earthloop=(8.01.times.D.sub.earthloop.times.c.sub.earthloop).times-
.f.sub.earthloop.times.(T.sub.earthloopin-T.sub.earthloopout)
[0036] Q.sub.earthloop=instantaneous rate of heat transfer on earth
loop side of hydraulic separator (Btu/hr)
[0037] D is the density of the fluid flowing through the loops
(lb/ft.sup.3);
[0038] c is specific heat of the fluid in the loops
(Btu/lb/.degree. F.);
[0039] f.sub.earthloop is the fluid flow rate in the indicated loop
(gallons/minute);
[0040] T is the temperature (.degree. F.) at the inlet to, or the
outlet from, the hydraulic separator in the indicated loop; and
[0041] 8.01 is a units constant.
[0042] Similarly, the layout as shown in FIG. 2, allows the
operator to determine the instantaneous rate of heat transfer in
the load loop using .DELTA.T and flow rate on the load loop side of
the hydraulic separator, as follows:
Q.sub.loadloop=(8.01.times.D.sub.loadloop.times.c.sub.loadloop).times.f.-
sub.loadloop.times.(T.sub.loadloopin-T.sub.loadloopout)
[0043] Q.sub.loadloop=instantaneous rate of heat transfer to load
side of hydraulic separator (Btu/hr);
[0044] D is the density of the fluid flowing through the loops
(lb/ft.sup.3);
[0045] c is the specific heat of the fluid in the loops
(Btu/lb/.degree. F);
[0046] f.sub.loadloop is the fluid flow rate in the load loop
(gallons/minute); T is the temperature (.degree. F.) at the inlet
to, or the outlet from, the hydraulic separator in the load loop;
and
[0047] 8.01 is a units constant.
[0048] As shown in FIG. 6, by continually testing the equality of
Q.sub.loadloop and Q.sub.earthloop, and raising and lowering the
flow through the earthloop, a highly efficient heat exchange
operation can be carried out.
[0049] The optimum heat pump performance occurs when the ratio of
the desired output (heating or cooling capacity), divided by the
total input power to operate the system is maximized. The ratio is
called the system COP, or Coefficient of Performance. This is most
easily shown in the single heat pump system of FIG. 1. In this
system, the temperature of the fluid flowing into and away from the
heat pump, designated by the numeral 210, is measured by the two
temperature sensors 206,207, and the flow rate is measured by the
flow transducer 216.
[0050] The optimum heat pump performance occurs when the ratio of
the desired output (heating or cooling capacity), divided by the
total input power to operate the system is maximized. The ratio is
called the system COP. The total input power is the electrical
wattage to operate the heat pump(s) and the earth loop
circulator.
[0051] The total input power is the electrical wattage to operate
the earth loop circulator 218 plus the power to operate the heat
pump 202. Heat rate measurement on the earth loop side 201 of the
SINGLE water-to-water or water-to-air heat pump, could be used to
vary the earth loop circulator speed and track the maximum system
COP. This is analogous to maximum power point tracking used by
inverters in photovoltaic systems. The goal is to vary the flow
rate within the earth loop 201, so that maximum system COP is
always maintained, while maintaining the necessary instantaneous
rate of heat transfer on the earth loop side 201.
[0052] I I
[0053] The following computation procedure would apply in the
heating mode for the directly heated system of FIG. 1, following
the algorithm illustrated by FIG. 7:
[0054] To determine the COP of the system, measurements are taken
of the total input wattage to the heat pump (Whp), and to the earth
loop circulator (Wcirc). Depending upon the wiring to the
circulators and compressors, this can require one or more watt
transducers 31,32. Where the heat pumps are used for cooling, it is
necessary to measure the wattage to each circulator
individually,
[0055] The heating output of the heat pump (either water-to-water
or water-to-air) can be calculated by the energy balance:
Q.sub.output=Q.sub.earthloop+(W.sub.hp.times.3.413)
[0056] Where 3.413 is a constant for this type of system.
[0057] The COP of the "system" consisting of the earth loop
circulator loop plus heat pump loop, in the heating mode, can be
calculated as follows:
COP.sub.heating=(Q.sub.earthllop-(W.sub.circ+W.sub.hp).times.3.413)/((W.-
sub.circ+W.sub.hp).times.3.413)
[0058] The COP of the "system" consisting of the earth loop
circulator plus heat pump, in the cooling mode, can be calculated
as follows:
COP.sub.cooling=(Q.sub.earthloop-(W.sub.circ+W.sub.hp).times.3.413)/((W.-
sub.circ+W.sub.hp).times.3.413)
[0059] In both of the above formulae, for Q.sub.earthloop, it is
assumed that the wattage [W.sub.hp] to operate the heat pump is
ultimately converted to heat and dissipated into the heated
space.
[0060] As shown in the flow chart of FIG. 7, when the heat pump
first starts, the earth loop circulator 218 should be operated at
50% of full speed. After a stabilization period of perhaps 1
minute, if readout from the controller 9 of the Q.sub.earthloop is
greater than the Q.sub.loadloop, incrementally reduce the earth
loop circulator speed and recalculate the system COP. If the system
COP is higher than before, repeat the incremental reductions of
earth loop circulator speed, each time calculating the new system
COP. If a drop in system COP occurs upon a drop in circulator
speed, incrementally increase the earth loop circulator 218 speed
and recalculate the system COP. Move the pump speed in the
direction that continually maximizes the system COP. This series of
operations is carried out automatically by the data controller,
which calculates the COP and then controls the earthloop circulator
218 to increase or decrease flow, as required by these
equations.
[0061] Although published performance data make clear that the COP
of the heat pump circulator decreases upon a drop in earth loop
flow rate, a corresponding, or greater, drop in input watts to the
earth loop circulator 8, could result in the system COP remaining
the same or increasing. When desired, the COP of the multi heat
pump system of FIG. 2 can be calculated by the total energy usage
on the load loop side of the, e.g., hydraulic separator.
[0062] The instrumentation shown in FIG. 1, provides the controller
9 (e.g., an iWorx Platform) with data to compute and log the COP of
the heat pump(s) only, as well as the COP of the overall system
(heat pump(s)+earth loop circulator), and to output a speed
regulation signal to the earth loop circulator 218 responsive to
the need to meet the instantaneous rate of heat transfer of the
load loop so as to maximize the system COP. The earth loop
circulator 218 is selected to be one capable of operating at
variable speeds in response to a control signal issued by the
electronic controller 9. A suitable commercially available example
is a Taco 2400-70 High Capacity Circulator, from Taco, Inc.
[0063] The load loop circulator 13, in FIG. 2, can be a pressure
regulated circulator sensitive to the flow requirements of the heat
pumps, i,e., the number of such heat pumps operating and the level
of operation of the operating array, Therefore, the flow on the
load loop side is defined only by the requirements of the operating
heat pumps.
[0064] The hydraulic separator 1 allows independent flow rates
through the earth loop and the hydronic load, i.e., heat pumps,
circuit supplying the multiple heat pump array of FIG. 2, while
maintaining continuing flow through each loop with full direct heat
exchange between the two loops.
[0065] Flow measurement is obtained from a flow sensor 2 at the
earthloop inlet to the hydraulic separator 1 and from a flow sensor
5 at the load loop inlet to the hydraulic separator 1; both flow
sensors 2, 5 measure the instantaneous rate of fluid flow into the
hydraulic separator 1 from its respective flow loop.
[0066] Similarly, temperature measurements are obtained at both the
inlets to and outlets from the hydraulic separator 1, on each of
the heat pump side and earth loop side of the hydraulic separator 1
utilizing pairs of temperature sensors 3,4 and 6,7.
[0067] Heat transfer calculations for each of the heat pump side
and earth loop side of the hydraulic separator can thus be made and
compared, using the instantaneous flow rate and temperature
difference measurements continually streamed to the electronic
controller 9 from the respective sensors.
[0068] The method and associated hardware of this invention allows
a system designer to design the optimal size earth loop circulator
based upon the maximum requirements of a particular heat pump
array, while allowing for operational optimization of the
circulator as the requirements of the heat pump loop changes to
varying levels below the maximum operational level.
[0069] It must be noted that, in addition to "closed" earth loop
systems, this method can be applied to "open loop" geothermal
systems that use ground water, or water from a lake, pond, or
ocean, as the source water for a multiple heat pump array.
[0070] Similarly, this method can also be applied to regulate flow
and reduce circulator electrical demand in systems using an
atmospheric cooling tower to dissipate heat from a multiple water
source heat pump system, or a boiler or other heat source. However,
because of the difficulties in dealing with a below ground closed
geothermal system, the most effective and preferred use of this
invention is in the context of such a closed geothermal loop
system.
[0071] The method of this invention, measures instantaneous thermal
demand (rate of heat transfer) to a multiple heat pump array and
compares it to instantaneous thermal supply (rate of heat transfer)
from the earth loop. Earth loop circulator speed is continually
adjusted as necessary to ensure that the rate of heat transfer from
the earth loop matches the rate of heat transfer required by the
multiple heat pump array. This method is enhanced and made more
efficient by the inclusion of a hydraulic separator between the
earth loop and load loop piping circuit serving the heat pump. This
is most significant for a multiple heat pump array, where the
demand can vary greatly by operating only some of the heat pumps
during certain periods.
[0072] By monitoring and balancing the rates of thermal energy
transfer across the hydraulic separator, i.e,, between the earth
loop side and the load side, there is assurance that the
instantaneous thermal needs of the load loop are met. This method
compensates for variations in the number of currently active heat
pumps within the load loop, as well as variations in COP
(Coefficient of Performance) and heating or cooling capacity of the
heat pumps if the geothermal temperature and heat pumps load
varies. Most particularly, this method provides stable control if
earth loop flow were to transition from turbulent to laminar as the
flow rate through the earth loop is varied.
[0073] In theory, such a transition would immediately drop the
convective heat transfer rate within the earth loop to
approximately 7 percent of the rate provided by turbulent flow.
This transition would manifest itself as a sudden change in the
temperature of fluid returning to the hydraulic separator from the
earth loop, the direction depending upon the direction of the heat
transfer, ie., whether the heat pumps are in a heating or cooling
mode.
[0074] The electronic controller 9, operating under the control
algorithm of this invention, would respond by causing an increase
in the earth loop flow if necessary to meet the load loop
requirements, or, allowing the earth loop to remain in laminar flow
if the load requirements are being met. There is no inherent
problem with the earth loop remaining in laminar flow provided
sufficient heat transfer is being provided to the load loop. The
head loss and pressure drop of laminar flow is much less than that
produced by turbulent flow, and thus permits very efficient
operation of the earthloop circulator. Thus, provided that the
thermal needs of the load loop are being met, operating the earth
loop with laminar flow greatly reduces electrical energy use by the
earth loop circulator whenever possible, and allows for an increase
in overall system efficiency (COP).
[0075] Conventional engineering practice now maintains the earth
loop flow rate high enough to prevent transition to laminar flow
under all circumstances (e.g. maintains Reynolds numbers above 2500
at worst case conditions on a continuous 24/7/365 day schedule, or
whenever one or more heat pumps are operating. This adds
significantly to pumping power requirements, even though transition
conditions may only occur under extreme conditions (e.g., the
lowest possible earth loop fluid temperature or when only one or
two of many heat pumps are operating, for example overnight in an
office building). The proposed method and system could provide
significant electrical energy savings by compensating for such
conditions as necessary.
[0076] A "smart" control subsystem, such as Taco, Inc.'s iWorx
platform, allows for both basic control and enhanced
monitoring/reporting of the system's performance. By adding watt
transducers to measure the electrical wattage supplied to the
circulators and heat pumps (or single heat pump, as the case may be
in FIG. 1), it is possible using, e.g., the iWorx platform, to
calculate and display the following parameters:
[0077] 1. Instantaneous system heat output
[0078] 2. Instantaneous system COP (Coefficient of Performance)
[0079] 3. Total heat output of multiple heat pump system over a
given time
[0080] 4. Average system COP (Coefficient of Performance) over a
given time
[0081] 5. Instantaneous system chilling capacity
[0082] 6. Instantaneous system EER (Energy Efficiency Ratio)
[0083] 7. Total "ton-hours" cooling supplied by heat pump system
over a given time
[0084] 8. Average system EER (Energy Efficiency Ratio) over a given
time
[0085] These calculated parameters, or indices, could be used to
verify system performance relative to theoretical estimated
performance. This information could also be use to help diagnose
operational (problems. By providing networking, either local or
through the internet, which is possible with this system, even
greater efficiencies are possible.
[0086] The above examples and descriptions are intended to be
exemplary only. It is understood that the full scope of this
invention should be determined only by the scope of the claims set
forth below.
* * * * *