RU2615678C2 - Near-surface soil heat use method - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: extra heating of soil is carried out by applying the solar radiation, as an outside heat source, inside the array of soil, by absorption of concentrated solar radiation in the receiver of solar radiation and heat transfer to the amount of gravel-water heat exchanger-accumulator which is in heat contact with soil. Throughout the year, selection of low-grade heat and its transformation using a heat pump cycle to a higher level, that meets the requirements of heating and hot water supply system, is carried out by transmission of heat through a heat exchanger connected to the contour of heat pump evaporator.

EFFECT: invention can improve energetic efficiency of processes of heat exchange, expand the scope and reduce the complexity of method.

3 cl, 2 dwg

Description

The invention relates to a power system and can be used in heat supply systems of buildings and structures for various purposes with the use of heat pumps for heating, heating the supply ventilation air and the production of domestic hot water.

Heat pump systems of heat supply (TST) of buildings are known that use low-potential heat of the surface layers of the Earth, the source of which is heat exchange processes at the “earth surface – atmosphere” boundary under conditions of absorption of solar radiation energy. The absorbed heat in the form of a temperature wave propagates deep into the earth's surface. The soil of the Earth’s surface layers is actually a heat accumulator of unlimited capacity, the thermal regime of which is formed under the influence of solar radiation and the flux of radiogenic heat coming from the bowels of the earth. Solar radiation incident on the earth's surface and seasonal changes in its intensity affect the temperature regime of soil layers occurring at depths of 10–20 meters. The temperature regime of soil layers located below the penetration depths of solar radiation heat is formed only under the influence of thermal energy coming from the bowels of the Earth, and practically does not depend on seasonal, and even more daily changes in the parameters of the external climate. The soil of the surface layers of the Earth, due to its widespread availability and a sufficiently high temperature potential, is the most promising source of low-potential thermal energy for heat pump installations.

There is a method of using the heat-accumulating properties of the soil, which consists in cooling the soil mass, selecting low-grade heat from thermal wells, through which the coolant previously cooled in the heat pump circulates, which selects heat energy from the soil and converts it using heat pumps to a higher level for heat supply. In this case, the selection of thermal energy from the soil can be realized by installing two types of closed TST heat exchangers located in the soil mass, using the heat of the soil and ground water using pipelines that form a closed system filled with a working fluid in the form of a liquid and its vapor: horizontal soil heat exchangers representing separate pipes located in previously dug trenches, laid relatively tightly and connected to each other in series or in parallel, and having a limited scope due to the need to use large areas of the earth’s surface for their construction, and vertical ground heat exchangers, which are separate pipes located in wells drilled in the earth’s crust, also interconnected in series and parallel, the use of which is associated with high construction costs and the inability to service (Fedyanin V.Ya., Karpov M.K. Use of soil heat exchangers in heat supply systems / V.Ya. Fedyanin, M.K. Karpov // Polzunovsky Bulletin. - 2006. - No. 4. - S. 98-103).

The disadvantages of this method are the large inertia and low energy efficiency of heat transfer of solar radiation absorbed at the boundary “earth's surface - atmosphere” to the deep layers of the soil, where the TST soil heat exchanger is installed, as well as low heat extraction efficiency for hot water supply of objects in the warm season, when the temperature of the soil mass adjacent to the soil heat exchanger significantly decreases due to the intense heat removal from the soil to the previous heating period.

The closest to the proposed invention in terms of technical nature and the achieved result (prototype) is a method for seasonally using low-grade heat of near-surface soil, including additional heating of the soil with an external heat source, throughout the year selection of low-grade heat using thermal wells and converting it using a heat pump cycle to more high level, satisfying the requirements of heating systems and hot water supply, in the inter-heating period Sat grew into the soil of the utilized thermal energy of ventilation blowouts for additional heat storage in the soil. In this case, additional soil heating is carried out by a third-party heat source, in which the utilized low-grade heat of ventilation emissions is used. Heating is carried out by supplying a liquid coolant through the soil layers using closed-type heat exchangers. In the inter-heating period, they switch to accumulation of external thermal discharges in the soil, transferring the supply of the heat carrier through the soil layers to an additional closed circulation system with an intermediate heat exchanger TST installed in its composition for the utilization of thermal discharges. In the transition from heat removal to accumulation of thermal discharges, the depth of the coolant supply through the soil layers is changed from the level of intersection of the vertical contours of one or more aquifers to the level above the roof of the upper aquifer. For this, a part of the circuits used for heat extraction from the soil is used when taking heat and accumulating heat discharges according to a shortened version, by installing these circuits as part of an additional circulation system with a length corresponding to the second of the indicated levels. In this case, the remaining circuits are installed in the main circulation system with a length corresponding to the first level. The seasonal change of levels is decided either by using known structural designs with wells of different depths as part of the circuits, or based on a downhole heat exchanger that implements the method (patent RU 2483255 C1, F24J 3/08 (2006/01), F24D 11/02 (2006 / 01)).

This method of seasonal use of low-grade heat of the near-surface soil has low energy efficiency due to the low specific heat removal per unit length of the thermal well during “thermal charging” of the soil mass, limited by the field of application due to the requirement of having its own source of utilized thermal energy, that is, having sufficient power of these sources and the presence of a waste heat collection system at the heat supply facility, for example, for most residential buildings Ki there is no possibility of creating such systems. In addition, the complexity of the work on the implementation of the described method associated with the creation and periodic maintenance during operation of the TST soil heat exchanger is high due to the low energy efficiency of heat transfer processes at the boundary “surface of the thermal well - soil”, which leads to the need to increase the area of the heat exchange surface thermal wells and, as a result, to a general increase in the volume of seasonal use of low-grade heat of near-surface soil.

The proposed technical solution is aimed at increasing the energy efficiency of heat transfer processes, expanding the scope and reducing the complexity of the implementation of the method.

To solve the problem in a method of using heat from surface soil, including additional heating of the soil with an external heat source, throughout the year the selection of low-grade heat and its conversion using the heat pump cycle to a higher level that meets the requirements of heating systems and hot water supply. According to the invention, additional soil heating is carried out by supplying a third-party heat source, which uses solar radiation, into the soil array, absorbing concentrated solar radiation in the solar radiation receiver, and transferring heat to the volume of the pebble-water heat exchanger-storage device in thermal contact with the soil, and the selection and conversion of low-grade heat from the soil to a higher temperature level is carried out by transferring heat through a closed heat exchanger type connected to the heat pump evaporator circuit.

The supply of solar radiation into the soil mass can be carried out by focusing it with mirror reflectors with curved, in particular parabolic, or rectilinear working surfaces.

Heat transfer to the volume of a pebble-water heat exchanger-accumulator in thermal contact with the soil from the receiver-absorber of solar radiation can be carried out by a single-phase convective flow of a liquid coolant due to thermosiphon circulation.

The increase in the energy efficiency of heat transfer processes is due to the high efficiency of using solar radiation incident on the boundary “earth's surface - atmosphere” due to the exclusion of losses from reflection from the surface and the loss of absorbed heat of heated soil with infrared radiation into the atmosphere. So, the total energy loss from the open surface of the soil is very significant and, for example, for the flat territories of the Altai Territory they make up 43 ÷ 66% of the annual amount of solar radiation (Fedyanin V.Ya., Meshcheryakov V.A. Innovative Technologies for Altai Energy / V I. Ya. Fedyanin, V. A. Meshcheryakov. - Barnaul: AAEP, 2010. - P. 62. ISBN 978-5-8349-0126-6).

The expansion of the scope of the method is due to the possibility of creating on its basis energy-efficient heat pump heat supply systems for any facilities, including facilities that do not have sufficient power sources of thermal discharges.

The decrease in the complexity of the implementation of the method is due to the simplicity of devices for concentrating and transferring energy of solar radiation to the TST system heat exchangers, higher energy efficiency of heat transfer processes to the consumer due to the higher operating temperature of the pebble-water heat exchanger-storage device than the array of adjacent soil and, as a result lower material consumption of heat exchangers of the TST system, less labor costs during their creation and operation than when implementing well-known technical solutions Nij.

The proposed method is illustrated in the drawing, where in FIG. 1 is a diagram of its implementation, and in FIG. 2 is a view A of FIG. one.

The method of using the heat of surface soil is realized using a solar radiation concentrator 1, which allows using both direct and reflected solar radiation, having a thermal insulation layer 2, vertical orientation device 3 of the solar radiation concentrator on the Sun, TST 4 heat exchanger, solar radiation receiver 5, gravel - water heat exchanger-storage 6.

The solar radiation concentrator 1 is provided with mirror reflectors with curvilinear, in particular parabolic, working surfaces of a conical or wedge-shaped configuration or rectilinear working surfaces. Reflectors with parabolic work surfaces, called focons, i.e. focusing cones, and foclines, i.e. focusing wedges, are currently used in solar energy.

Focons and phoclines with parabolic working surfaces have two main positive properties: they do not require high precision manufacturing of the reflector’s mirror surface and, most importantly, they maintain the initial level of radiation concentration with a low accuracy of the orientation of the reflector axis on the Sun. In stationary conditions, they can work effectively, remaining motionless for several months in relation to the luminary.

The best material for the working surfaces of the reflector is aluminum, which has the highest integrated reflection coefficient in the wavelength range of the solar spectrum. To protect aluminum from external influences, a protective coating must be applied to it, in particular, from a thin polymer film, either from a film of silicon oxide or from a film of aluminum dioxide.

The following basic requirements are imposed on solar radiation concentrators:

- high reflectivity in the wavelength range of the spectrum of solar radiation;

- the minimum specific gravity, that is, the mass per unit area of the reflecting surface;

- compactness in the transport state with the simplicity and reliability of the devices providing assembly;

- the stability of structural elements and optical coatings of reflecting work surfaces to prolonged exposure to environmental factors;

- low cost and ease of manufacture and repair.

The main energy indicator of a solar radiation concentrator is the coefficient, that is, the degree, concentration, or concentrating ability K, which is defined as the ratio of the average density of concentrated radiation to the density of the radiant flux incident on the reflective surface, provided the latter is accurately oriented to the Sun.

The outer surface of the hub 1 to prevent moisture condensation is covered with a layer of effective thermal insulation 2.

The device 3 of the vertical orientation of the solar radiation concentrator on the Sun allows you to adjust the direction of the axis of the concentrator 1 depending on the seasonal change in the trajectory of the visible movement of the Sun.

The TST 4 heat exchanger, which can be made spiral, is designed to transfer heat energy to the heat exchanger-evaporator of the heat pump (not shown in the drawing).

The receiver 5 of solar radiation closed, that is, cavity, type, heat exchanger TST 4 and pebble-water heat exchanger-storage 6 are built into the soil mass.

The method of using the heat of surface soil is as follows.

The soil is additionally heated by supplying an external heat source, which uses solar radiation, into the soil array, through the solar radiation concentrator 1, absorbing concentrated solar radiation through the solar radiation receiver 5 and transferring heat to the volume of the pebble-water heat exchanger-storage device 6 located in thermal contact with the ground. Thus, concentrated solar radiation entering the solar radiation receiver 5 heats the walls of the internal cavity, and the coolant circulating in the jacket of the solar radiation receiver transfers the absorbed heat to the volume of the pebble-water heat exchanger-storage 6.

The selection and conversion of low-grade heat from the soil to a higher temperature level that meets the requirements of heating systems and hot water supply, using the heat pump cycle throughout the year, is carried out by further transfer of heat through the TST 4 heat exchanger connected to the heat pump evaporator circuit.

The solar radiation can be supplied into the soil mass by focusing it with mirror reflectors with curved, in particular parabolic, or rectilinear working surfaces.

Heat transfer to the volume of the pebbly-water heat exchanger-accumulator 6, which is in thermal contact with the soil, can be carried out by a single-phase convective flow of a liquid coolant.

The proposed method of using the heat of surface soil provides high energy efficiency, expanding the scope and reducing the complexity and cost of manufacturing and periodic maintenance of equipment that implements the method.

Claims (3)

1. The method of using the heat of surface soil, including additional soil heating by an external heat source, throughout the year the selection of low-grade heat and converting it using a heat pump cycle to a higher level that meets the requirements of heating systems and hot water supply, characterized in that the additional heating of the soil carried out by supplying an external source of heat, which is used as solar radiation, into the soil mass, absorption of concentrated solar radiation in the receiver of solar radiation and heat transfer to the volume of the pebbly-water heat exchanger-drive in thermal contact with the soil, and the selection and conversion of low-grade heat from the soil to a higher temperature level is carried out by transferring heat through a heat exchanger connected to the evaporator circuit heat pump. 2. The method according to p. 1, characterized in that the supply of solar radiation into the soil mass is carried out by focusing it with mirror reflectors with curved, in particular parabolic, or rectilinear working surfaces. 3. The method according to p. 1, characterized in that the heat transfer to the volume of the pebble-water heat exchanger-drive in thermal contact with the soil is carried out by a single-phase convective flow of a liquid coolant.

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