WO2018073466A1

WO2018073466A1 - System and method for geothermal hybrid climate control

Info

Publication number: WO2018073466A1
Application number: PCT/ES2017/070637
Authority: WO
Inventors: Victor Aitor ALVAREZ GONZALEZ; Oscar ALVAREZ GALLARDO; Miguel Angel BONILLA JAIME; Bartolomé QUIÑONERO MARTÍNEZ; David VEREA GIL
Original assignee: Sociedad Española De Montajes Industriales, S.A..; Arial Proyectos E Instalaciones Energéticas, S.L..
Priority date: 2016-10-18
Filing date: 2017-09-27
Publication date: 2018-04-26
Also published as: ES2671973A1; ES2671973B1

Abstract

The invention relates to a geothermal hybrid climate control system comprising a geothermal exchanger (1) with one or more tanks connected to a coil (2) or similar in an air circulation circuit of a cooler in which is also disposed a circuit (4) of refrigerant fluid from a main refrigeration exchanger (3). The method for controlling the climate of an installation during a demand time (tds) in which climate control with outdoor air (free cooling) is insufficient, comprises activating a refrigeration circuit with a geothermal exchanger (1) during a maximum set time, but allowing that time to be increased if the estimation of the temperature increase until the end of the demand time (tds) is lower than a pre-set operating temperature (To) plus a pre-defined margin.

Description

DESCRIPTION

System and method of geothermal hybrid air conditioning SECTOR OF THE TECHNIQUE

The present invention relates to a low enthalpy geothermal hybridization system and method for compact air conditioning equipment by direct expansion. STATE OF THE TECHNIQUE

The reliability of electronic equipment depends strongly on the temperatures at which they are maintained. In a computer or desktop computer it is not difficult to have simple cooling means to reduce its temperature. For example a fan.

When electronic equipment is grouped, as in a server room, it is convenient to install refrigeration equipment. Another solution is that of WO2014039212 or US201 1247348, where electronic equipment is placed underground to take advantage of its temperature or groundwater. This system however or does not produce the necessary cooling, or quickly depletes the geothermal potential.

Other systems offer the use of geothermal energy to improve the coefficient of operability (COP). In these systems, geothermal-cooled fluid is used within the thermodynamic cycle of the cooling fluid.

In remote installations, such as a telephone antenna, a television repeater, etc. Outside an urban core, the power required for refrigeration is a relevant technical conditioner, which even forces to define high temperature conditions, resulting in a greater number of failures.

The applicant does not know a solution similar to the invention.

BRIEF EXPLANATION OF THE INVENTION The invention consists of a system and a method of geothermal hybrid air conditioning according to the claims.

The object is to obtain a passive cooling system of very low consumption with low enthalpy geothermal (closed-loop) use, and maximum setpoint temperatures for industrial uses. All this, under a system of "system logic" that minimizes the material and simplifies the installation, by means of a comparative enthalpy geothermal system. As a basic idea of the system, the type of cooling change is based on time, instead of the well temperature, the geothermal fluid or the installation temperature. In this way the recovery of the temperature of the well and the fluids is optimized (reset) and it is not necessary to install sensors in the well, with the complication that implies maintenance.

It is a system of support and efficient improvement of consumption in those cases where technical requirements and environmental conditions do not allow the active air conditioner (air conditioning) to be eliminated by a simple system based on freecooling.

It involves considerable energy savings, and always greater than 85%, being able to reach values greater than 95% in a very high percentage of cases. It is possible to complement the installation with solar panels to even eliminate the need to make connections to the power grid, which is very favorable in remote installations.

In the text of this report, the use of the singular when naming the elements ("a coil", "an exchanger", etc.) does not exclude the possibility of having several similar elements in series or parallel. That is, the coil can correspond to several serpentines in series or parallel, etc.

The system of the invention is a geothermal hybrid air conditioning system comprising:

A geothermal exchanger with one or more wells connected to a coil or similar through which water or brine circulates. The circuit can be opened or closed with the known advantages of each type.

A main cooling exchanger (condenser, Peltier cell, ...) of a refrigerant fluid connected to a refrigerant fluid circuit. A cooler of the installation to be heated, which has an air circulation circuit in which the coil or similar and the cooling fluid circuit are arranged to perform the cooling of the air. In standard operation, the cooler has a first mode of operation in which the cold fluid of the cooler is the refrigerant fluid, and a second mode of operation in which the cold fluid of the cooler corresponds to the fluid from the geothermal exchanger. It is possible to use both fluids at the same time, so it is convenient that the coil is arranged upstream of the refrigerant fluid circuit.

The invention also relates to the geothermal hybrid air conditioning method of an installation during a demand time (tds), which is defined as one in which the air conditioning with free air (freecooling) is not sufficient to keep the installation temperature below of a preset operating temperature (To). For this, the previous system is used through the steps of:

a- Activate the cooler using the fluid from the geothermal exchanger as a cold fluid during an initial setpoint time (tci) to reach the precalculated operating temperature depending on the geothermal, weather and equipment variables.

b- Maintain the use of the geothermal exchanger if the estimated temperature increase (from a calculated temperature gradient) during the remaining time until the end of the demand time (tds) is lower than the operating temperature (To) plus a predefined margin.

c- Otherwise, stop the circulation of the fluid coming from the geothermal exchanger and activate the circulation of the ambient air (freecoling) or of a cooling fluid coming from the main exchanger during a predefined (tr) reset time

d- repeat steps a-c, with a permanent setpoint time (tcp) instead of the initial setpoint time (tci), until the demand time (tds) is reached.

If the outside temperature is low enough, stage c can be performed by freecooling. Likewise, if the installation is sensitive or the operating temperature (To) is already defined in the limit, stage b can be performed with a null predefined margin. DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, the following figures are included.

Figure 1: Scheme of an embodiment of the invention.

Figure 2: Examples of installation temperature graph and the activation of the first mode of operation or cooling over a day. EMBODIMENTS OF THE INVENTION

Next, an embodiment of the invention will be briefly described as an illustrative and non-limiting example thereof. The invention shown in the figures is composed of the following elements:

An open or closed circuit geothermal exchanger (1). The number of wells and depth will depend on the geological conditions and the design needs. Underground geothermal exchanger (1) will circulate groundwater or a brine or saline solution that will cool in the wells for return to the facility.

A main exchanger (3), which cools a cooling fluid in a condenser or other similar system known in the art (Peltier cell, ...) different from the geothermal method (generally non-renewable).

A cooler (5), formed by a traditional air conditioning unit, to which two operating modes are applied:

o A first mode in which the chiller cooler fluid (5) is the coolant fluid of the main exchanger (3) that circulates through a refrigerant fluid circuit (4) disposed within the chiller air circulation circuit (5).

o A second mode in which the chiller cold fluid (5) corresponds to the fluid from the geothermal exchanger (1). This cold fluid circulates through a coil (2) or other similar device within the air circulation circuit of the cooler (5). This coil (2) will be arranged in parallel to the refrigerant fluid circuit (4), so that one or the other can be activated. A controller that performs the start-up and stop of the air conditioning system, and the activation of the different fluid circuits. Preferably with learning capacity and optimization in real time, to establish the set times that optimize consumption.

These elements will be complemented, as is known and usual, with pumps, shut-off or bypass valves, purges, pressure gauges, etc. Likewise, the fluid from each exchanger may pass directly from the exchanger (1, 3) to the cooler (5) or a second intermediate circuit may be installed between them. Likewise, if the fluid used in both exchangers (1, 3) is the same, the coil (2) and the refrigerant fluid circuit (4) can be the same element with bypass valves to select the source of the refrigerant.

Preferably the coil (2) will be upstream of the refrigerant fluid circuit (4), to have the option of pre-cooling if urgent cooling is required in which both the coil (2) and the circuit are activated. of refrigerant fluid (4).

The defined system optimizes the performance of existing air conditioning machines. In the first instance by applying operating logics that minimize the start of the air conditioning compressor. Even if the weather or geothermal conditions are good, you can only start in case of emergency such as breakdowns, heat waves, etc. In the same way, the geothermal exchanger (1) acts as an emergency system in case the industrial active air conditioners fail since, unlike a direct air conditioning ventilation of the outside air (freecooling), which depends on the outside temperatures, the Geothermal exchanger (1) draws on values of constant subsoil temperatures throughout the year. The system design parameters, in terms of operation times of the exchangers (1, 3) are the following:

- Geothermal variables: temperature gradient, water table, ...

- Climatic variables.

- Expected operating temperature (To).

- Equipment: coils, pumping power, main exchanger power (3), installed electrical power, etc. Installation equipment and heat emitted by it.

Depth and number of wells, which can also be defined from the other data. From this data, the chiller operating times are defined in each mode:

Initial setpoint time (tci), which corresponds to the time to reach the operating temperature (To) using only the geothermal exchanger (1) for the first time in the day.

Permanent setpoint time (tcp), which corresponds to the time needed to reach the operating temperature (To) again on successive occasions or instances (once the tci has been exceeded), also with the geothermal exchanger (1).

Reset time (tr), which corresponds to the time during which the first mode of operation of the cooler is entered.

These values allow to define the number of cycles that will be applied during the demand time (tds), or time in which the freecooling is necessary but not available. For example, in summer and in Spain the demand time (tds) will be approximately 12h.

Under ideal conditions, once the operating temperature (To) has been reached, it is not necessary to activate the first mode of the cooler (5). However, this may involve a large number of wells and a great depth so as not to exhaust the geothermal potential. Therefore, the operating temperature (To) and the number of cycles (going through both modes in the cooler) will be defined to produce a high energy saving but with a less expensive installation. If desired, the energy rate can be included as a factor, making more resets during the valley hours.

The following table shows, by way of example, the basic consumption in a demand time (tds) of 12h without geothermal energy (zero cycles) or by applying geothermal energy with a certain number of cycles.

Energy saving cycles

0 (without geothermal) 0%

1 92%

2 90%

It can be seen that the difference in savings of a system designed at 1 cycle (demanding in terms of investment) of another one of 2 cycles (less demanding) is quite small, the reduction in savings being approximately linear.

During the reset the temperature of the wells is recovered, following a response similar to Newton's cooling law. This same recovery occurs at any time when freecooling can be applied, for example at night. Specifically, the night reset allows the daily starting temperature of the well to be very stable.

During the day, as the outside temperature increases, it may be necessary to activate the air conditioning system, starting the daily cycle with the second mode of the cooler (5) until the operating temperature (To) is reached. If the initial setpoint time (tci) is exceeded, the cooler goes to the first mode of operation, during a reset time (tr), such as ten minutes. From that moment on, if necessary, the activation of the second mode of operation is carried out in periods equal to the permanent setpoint time (tcp) already defined. Schematically, the daily cycle will be as follows:

one . A few hours after dawn, freecooling is no longer operational and the wells have been completely reset.

2. Start the second cooling or geocooling mode until the initial setpoint time (tci) is reached.

3. Once the initial setpoint time (tci) is reached, the management system (controller) performs an immediate calculation to analyze the remaining time until the demand time (tds) is reached. It will estimate if in the remaining time, and for the temperature gradient in the installation, the operating temperature (To) will be exceeded. If it is not to be exceeded, the cycle is avoided by increasing the operating time of the second cooling mode to the demand time (tds). This avoids the use of the first cooling mode, as it would imply high power consumption. If the estimated temperature will exceed the operating temperature (To) by a predefined percentage or range (for example 5% in ^e C), the second cooling mode can also be maintained. 4. If the estimated temperature is higher than the operating temperature (To), even with the optional range, two events are generated:

4.1. Well pumps stop, the secondary circuit is interrupted and the reset is initiated. The ideal (tr) reset time can be calculated or estimated experimentally.

4.2. The first cooling mode of the cooler (5) is activated. If the outside temperature is low enough to allow, during the reduced reset time, to maintain the temperature of the installation below the operating temperature (To) (with or without the margin), freecoling is preferably used. It should be noted that the fact that the outside temperature does not allow freecooling implies that the gradient will be greater than zero, but does not prevent a positive but small value from being acceptable during the reset time (tr). If freecooling is not enough, the main exchanger (3) and the refrigerant fluid circuit (4) will be activated.

5. After the reset time (tr) the second cooling mode starts again.

6. Once the permanent setpoint time (tcp) has been reached, the system returns to point (3), performing the comparison again and repeating points (3), (4) and (5) until the time tds is reached.

In the example of figure 2, three cycles have been represented, so that in the latter the second cooling mode has remained active a little longer than the permanent setpoint time, allowing the installation temperature to slightly exceed the temperature of operation (To) before activating freecooling.

Claims

1 - Geothermal hybrid air conditioning system characterized by comprising:

a geothermal exchanger (1) with one or more wells connected to a coil (2) or the like through which water or brine circulates;

a main exchanger (3) for cooling a refrigerant fluid connected to a refrigerant fluid circuit (4);

a cooler (5) of the installation, which has an air circulation circuit in which the coil (2) and the refrigerant fluid circuit (4) are arranged to cool the air.

2- System according to claim 1, wherein the chiller (5) has a first mode of operation in which the chiller fluid (5) is the refrigerant fluid, and a second mode of operation in which the chiller fluid cooler (5) corresponds to the fluid from the geothermal exchanger (1).

3- System according to claim 1, wherein the coil (2) is disposed within the air circulation circuit upstream of the part of the refrigerant fluid circuit (4) contained in the cooler (5).

4- Geothermal hybrid air conditioning method of an installation during a demand time (tds) in which the air conditioning with free air (freecooling) is not sufficient to maintain the installation temperature below a predetermined operating temperature (To), using the system of claim 1, characterized in that it comprises the steps of:

a- activate a cooler (5) using as a cold fluid the fluid from a cooling circuit with a geothermal exchanger (1) during an initial setpoint time (tci) to reach the operating temperature, precalculated based on geothermal variables , weather and equipment;

b- if the temperature reached plus the estimated temperature increase during the remaining time until the demand time (tds), from the temperature gradient, is lower than the operating temperature (To) plus a predefined range, keep the use of the geothermal exchanger (1);

c- otherwise, stop the circulation of fluid from the geothermal exchanger (1) and activate the circulation of ambient air {freecooling) or of a refrigerant fluid from a main exchanger (3) during a predefined reset time (tr);

d- repeat the ac stages, with a permanent setpoint time (tcp) to reach the precalculated operating temperature again depending on the geothermal, climatological and equipment variables instead of the initial setpoint time (tci) of stage a , until reaching the demand time (tds).

5- Method according to claim 4, whose step c is performed by freecooling. 6- Method according to claim 4, in which step b the predefined margin is null.