GB2504568A

GB2504568A - Venturi heat exchanger for power plant condenser

Info

Publication number: GB2504568A
Application number: GB1307714.4A
Authority: GB
Inventors: James Corbishley
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-07-31
Filing date: 2013-04-29
Publication date: 2014-02-05
Anticipated expiration: 2033-04-29
Also published as: GB201307714D0; GB201213695D0; GB2504568B

Abstract

A condenser for a thermal power plant uses a gas 3 flowing through a restricted passage to lower its pressure and temperature due to the venturi effect. The reduced temperature gas extracts an increased amount of heat from the working fluid. When the cooling gas recovers its pressure and temperature in the divergent section 5, it can itself drive a turbine 7. The cooling fluid may be oxygen derived from electrolysis and stored under hydrostatic pressure, possibly in a disused mine 9. The (heated) oxygen and hydrogen may be supplied to a gas turbine engine of the thermal power plant (figure 3).

Description

TITLE: A method of condensing and energy recovery using the Venturi effect, and a method of energy storage using that method in a hydrogen oxygen combusting turbine.

BACKGROUND

Various methods of energy storage have been investigated in order to help integrate intermittent or invariant generating methods into electricity supply grids. Wind energy in particular, can require substantial backup and storage technologies to facilitate widespread use. Even with a relatively small proportion of wind energy, some capacity will be wasted when demand is low, and there are corresponding periods of higher demand but insufficient supply where backup generation must be used. The situation can be exacerbated as the proportion of wind energy increases. Supply and demand mismatch with wind can occur seasonally as well as in daily cycles, which creates a particular opportunity for storage systems with large generation duration times. Many large scale grid energy storage systems have found it difficult to compete with conventional gas turbines for load levelling variable energy sources, partly due to high capital costs, a shortage of potential sites, long build times, and energy losses due to various system inefficiencies.

Compressed air energy storage is well established in prior art. Such systems use air that has been compressed and stored during off peak periods to generate electricity on peak. The energy content of a quantity of compressed air is determined both by its pressure and its temperature, which temperature will increase with pressure. Adiabatic storage methods attempt to retain the heat of compression for recovery on expansion to increase efficiency levels, whereas simpler diabatic methods have no mechanism for retaining this heat. Storing compressed air in large underground formations, within pressure vessels, and under hydrostatic pressure is prior art. Methods of increasing power output by pre-heating the air with a waste heat source at a useable temperature, or by removing, storing, and then returning the heat of compression have also been investigated.

The comparatively rapid response times possible with compressed air energy storage is particularly relevant to its ability to provide a back up generation source for wind.

The most common methods of electrical generation from a thermal energy source use turbo machinery to extract mechanical work, which mechanical work is used to drive a generator. The most common turbine cycles are the Brayton, Rankine, and combined cycles. The turbine's working fluid remains in gaseous form throughout in the Brayton cycle, where it is first compressed, then provided with a heat source (usually combustion), and then expanded through a turbine to recover energy. The working fluid is not usually re-circulated within the Brayton cycle although such closed cycles would still fit within the definition. In contrast, the Rankine cycle continuously re-circulates its working fluid, which is present in both liquid and gaseous form at different stages in the cycle. The fluid in gaseous form, which has been expanded through the turbine to extract work, is condensed back to liquid to create a vacuum and flow in the turbine. That condensed liquid is then extracted from the condenser, re-pressurised, and introduced to a heat source where it is vaporized and supplied back to the turbine in gaseous form. The working fluid to be condensed is typically steam, and the fluid used to condense is typically air or water. Typical pressures within a steam condenser are sub-atmospheric at around 0.05 bar (5000 Pa). The significant amount of waste heat from condensing is dispersed as the temperatures involved are too low to be practicable for further energy recovery. The efficiency levels in terms of electrical recovery are up to 40% for both cycles.

Combined cycle arrangements use both the Brayton and Rankine cycles, where the Rankine cycle extracts heat from the exhaust of the Brayton cycle to achieve an aggregate 60% electrical efficiency levels.

Hydrogen combusting gas turbines are also prior art. These turbines may be air breathing and produce the pollutant NOx, or combust hydrogen and oxygen gas in stoichiometric ratios, producing only steam. By way of example, a recuperating hydrogen oxygen combusting gas turbine has been disclosed in US Pat No W097/31184 issued to Westinghouse Electric Corporation, where the waste heat from the steam is recuperated into the hydrogen fuel and oxygen. The arrangement described does not use the Venturi effect to provide a condensing mechanism, and although the hydrogen and oxygen may be supplied as cryogenic liquid, the method of cooling these fluids to cryogenic level is not specified. An energy storage method using a hydrogen oxygen combusting gas turbine with submerged water electrolysis and hydrostatically pressurised fuel and oxidiser storage is disclosed in French Pat No FR2286891 issued to Imberteche in 1976, which system does not specify a method of recovering the latent heat of vaporisation of the steam.

A peaking power system of an air breathing gas turbine using a compressed air storage system is disclosed by Flynt, in US Patent no 3,831,373 published in 1974. The gas turbine disclosed can either operate conventionally, or the compressor of that turbine can be powered by off-peak electricity and used to compress air for storage, and on peak, the stored air can be released through the combustor and turbine in place of the compressor for increased generation output. Because the gas turbine is air breathing, its components can in effect be used simultaneously as part of the compressed air system. The air is stored under hydrostatic pressure in this system. In one embodiment, the system includes a method of using the heat of compression produced during storage by using a flow of water in a heat exchanger to produce steam, which steam is then expanded through the turbine and the rotational energy used to supplement the compressor.

The method of using the Venturi effect for both cooling and heating has been disclosed in US Pat US3,200,607 issued to Williams in 1965 whose space conditioning apparatus can be operated to provide either cooling or heating, and US Pat US2,441,279 issued to McColIum in 1942 whose Venturi system can simultaneously be used for cooling aircraft components and the heat extracted can be used for air conditioning. The method of using the Venturi effect within a heat exchanger to exchange heat between two mass flows is also disclosed in Patent Specification GB1,419,490 by Cowans in 1971. A further description of heat transfer using the Venturi effect is described in US Patent Application US2009/0223650 filed by Williams, which considers the possibility of using heat from a Venturi heat exchanger for power generation without elaborating as to any methodology.

Although that document discusses exploiting the thermodynamic phase changes by the Bernoulli heat pump and notes the high energy content available due to such a phase change, that document does not disclose any mechanism or methodology for utilising that phase change.

BRIEF DESCRIPTION

Figure 1 shows a schematic representation of a Venturi condenser within a thermal power plant with a hydrostatically pressurised stored gas flow.

Figure 2 shows a schematic diagram of a hydrogen oxygen electrolysis and gas turbine generation system with hydrostatically pressurised fuel, oxygen, and air storage.

Figure 3 shows an example configuration of a hydrogen oxygen electrolysis and compressed air system within a former coal mine.

DETAILED DESCRIPTION

The following embodiments are shown by way of example only. More complex arrangements may be preferred which will be further embodiments of this invention. By way of example such embodiments may include any turbine generating arrangement which includes the condensing mechanism as shown, a plurality or combined use of any of the components shown, or additional components which supplement the components and methodology shown. Examples of additional components are parallel gas flows and fins on the tubular sections within the Venturi condenser, electrical control and ancillary equipment, and various valves and nozzles to control, adjust, or maintain the gas flow. The working fluid to be condensed is typically steam, and the gas used to condense that working fluid is typically air, or parallel flows of air and pure oxygen, although other working fluids and or gasses might be used where appropriate.

Referring to Figure 1, there is shown a schematic diagram of a system in which a hydrostatically powered condenser using the Venturi effect extracts energy from a thermal power plant turbine.

During energy extraction, the exhausted steam or other fluid (1) enters the condenser in a slightly superheated or saturated state, as much of the useful energy has already been extracted during expansion through the turbine (2). A significant proportion of energy remains in fluid (1) at this stage due to its latent heat of vaporisation which cannot be recovered in the turbine. This energy is extracted by a separate gas (3) which is forced under hydrostatic pressure through the condenser via at least one ducted pipe arrangement. This ducted gas passes through a restricted section at or within the condenser, comprising at least one converging (4) and diverging (5) sub-sections and at least one narrowed straight section between these converging and diverging sections. As the ducted gas passes through (4), its pressure drops and is converted into velocity, which effect reduces its temperature allowing significant heat absorption from the turbine working fluid. As the ducted gas extracts thermal energy from the turbine working fluid, this causes a phase change from gas to liquid and consequently a volume reduction in that fluid, creating a vacuum within the condenser (6) and consequently flow through the turbine. When the ducted gas is re-pressurised within diverging section (5), the pressure increase raises its temperature to an elevated level which is higher than the temperature in the condenser, therefore this section is thermally isolated from the condenser to prevent any transmission of heat during this stage. The ducted gas can then be expanded within turbine (7), or other suitable means of energy extraction. The condensed fluid exiting at (8) is now re-circulated in liquid form to a pump where it is re-pressurized, then a heat source where it is vaporized, and then it is used to drive turbine (2) to generate electricity. During energy storage, a gas is compressed and transmitted into a hydrostatically pressurised unit or container (9), typically using off-peak or low demand electricity in compressor (10), which in some embodiments could be the same, or part of the same component, as turbine (7). The hydrostatic pressure maintains the gas at a constant pressure throughout discharge allowing the condensing energy to be stored for later use within the Venturi condenser, avoiding an energy drain during generation to increase the maximum available output.

Referring to Figure 2, there is shown a schematic diagram of a system in which a Venturi condenser powered by a hydrostatically pressurized gas which is used to extract energy from a hydrogen oxygen turbine generation and water electrolysis system. During storage, the water feed (11) used by the electrolyser to produce hydrogen and oxygen gas is supplied under hydrostatic pressure. The water feed shown is taken from the ejected steam from the turbine although it could also be externally sourced, possibly from the surrounding water. A water reservoir is provided to accommodate the different fluid volumes of the electrolyser water feed. The system of electrolysis (12) is supplied with an external source of electricity, typically off peak or low demand electricity, and used to produce hydrogen and oxygen gasses which are allowed to rise through pipe-work into storage units (13), and (14). Air is also compressed during storage by a compressor (15) and transmitted through separate pipe-work into storage unit (16), each storage unit subjecting its gas to a relatively constant hydrostatic pressure. The storage units shown here are flexible membranes contained within rigid ballasting outer structures. On demand, the hydrogen and oxygen gasses are released under hydrostatic pressure and transmitted to the hydrogen oxygen turbine generator (17) where they are combusted in order to generate electricity. The air is transmitted through at least one duct through condenser (18) to provide condensing and heat recovery through the venturi effect before being expanded through air motor or turbine (19). The oxygen gas in this Figure is also transmitted through condenser (18) in this Figure in a duct system parallel to the duct system used by air, where both gasses provide condensing and extracts thermal energy via the Venturi effect, supplying hot oxygen gas to raise the heat of combustion and increase the output of the hydrogen oxygen gas turbine.

Referring to Figure 3, there is shown a system located within an adapted deep coal mine. Two vertical shafts have been converted, shaft (20) contains a means of access to the electrolyser below and also the power supply, and shaft (21) is flooded to provide hydrostatic pressurization of the storage units, and contains pipe-work for the gasses and a separate column of water feed for the electrolyser. This arrangement is by way of example only. Although the electrolyser shown is not submerged, its water feed is hydrostatically pressurised, which pressurization can then directly be transferred to the gasses produced through electrolysis. The electrolyser (22) housed within a part of the mine (23) which is not flooded and is accessible through Shaft (20). Section (24) separates the flooded section from the non-flooded section and contains the pipe-work for transmitting hydrogen and oxygen gasses and water supply. Section (25) is the flooded section subjected to hydrostatic pressure by the water column in (21), and contains the storage units which are shown as flexible membranes (26) containing gaseous hydrogen, oxygen, and air within different rooms in the mine. Any number of discrete units might be used for each of the gasses although only three are shown here. The gasses are supplied to a hydrogen oxygen turbine arrangement (27), a compressed air system (28), and a Venturi condenser (29). Variations in water level of the hydrostatic pressurization fluid which may result from differing levels of gas storage can be accommodated by reservoir (30) which maintains the hydrostatic pressure at a relatively constant level.

Claims

CLAIMS1. A method of condensing and energy recovery for a thermal power plant where: a. a gaseous fluid is ducted through the condenser of that power plant, which ducted section or sections includes a restricted section in which pressurisation of that ducted gas is converted into velocity via the Venturi effect, the temperature of that first gas reduces which increases the amount of thermal energy which can be absorbed, b. which gaseous fluid absorbs thermal energy from a working fluid of turbine causing a state change within that working fluid, which state change reduces the volume of that working fluid creating a vacuum and consequently flow through the turbine, c. which ducted gas, on exiting the restricted Venturi section, re-pressurizes, the temperature of that first gaseous fluid rising to an elevated level from which useful energy recovery can occur.
2. A method according to Claim 1 where the gas which is ducted through the Venturi condenser during periods of higher electricity demand to provide condensing and energy C') recovery, has been compressed using off peak or lower demand electricity and stored under hydrostatic pressure for release on demand.
3. A method electrical energy storage, where hydrogen and oxygen gasses are produced through water electrolysis and stored under hydrostatic pressure, and combusted in a gas turbine, which turbine working fluid is condensed using a Venturi condenser using the methods of condensing and energy recovery claimed in Claim 1 or Claim 2.
4. A method as claimed in Claim 3 above, where hydrostatically stored oxygen gas produced through water electrolysis is used within a Venturi condenser of a hydrogen oxygen combusting gas turbine using the methods of condensing and energy recovery claimed in Claim 1 or Claim 2.
5. A method according to any or all of the Claims above where the hydrostatically pressurized storage units are located within an adapted deep mine or part of an adapted deep mine, where the hydrostatic pressure is derived from a mineshaft.
6. A method according to Claim 5 above where the system of electrolysis and pressurized storage units are located within an adapted deep mine or part of an adapted deep mine.Amendment to the claims have been filed as followsCLAIMS1. A method of condensing and energy recovery for a thermal power plant where: a. a condenser of the power plant is cooled by a hydrostatically pressurised gaseous fluid, the condenser including at least one section with a reduced cross section such that the gaseous fluid is accelerated and reduces in density and temperature; b. the working fluid changes state in the condenser; c. where useful energy is recovered from the gaseous fluid after it exits the section with a reduced cross section, and; 2. A method according to Claim 1 where the gas which is ducted through the Venturi condenser during periods of higher electricity demand to provide condensing and energy recovery, has been compressed using off peak or lower demand electricity and stored under hydrostatic pressure.3. A method electrical energy storage, where hydrogen and oxygen gasses are produced through (V) water electrolysis and stored under hydrostatic pressure, and combusted in a gas turbine, which turbine working fluid is condensed using a Venturi condenser using the methods of condensing and energy recovery claimed in Claim 1 or Claim 2. r4. A method as claimed in Claim 3 above, where hydrostatically stored oxygen gas produced through water electrolysis is used within a Venturi condenser of a hydrogen oxygen combusting gas turbine using the methods of condensing and energy recovery claimed in Claim 1 or Claim 2.5. A method according to any or all of the Claims above where the hydrostatically pressurized storage units are located within an adapted deep mine or part of an adapted deep mine, where hydrostatic pressure is derived from a water column contained within a mineshaft.6. A method according to Claim 5 above where the system of electrolysis and pressurized storage units are located within an adapted deep mine or part of an adapted deep mine.