DESC:TECHNICAL FIELD

This invention relates generally to power plants, and more particularly, to an improved system providing integration of solar energy in a fossil fired power plant for producing either higher power output for same coal consumption or lower coal consumption for same power output or a combination of both and thereby reducing the CO2 Intensity.

BACKGROUND

The hybridization of fossil fired power plant with solar thermal is an excellent mean to harness the benefits of solar thermal technology with simultaneous mitigation of concerns pertaining to stand alone solar thermal power plant. It also results in higher solar energy to electricity conversion efficiency and thereby greater saving of fossil fuel and thus abatement of CO2 emission.

The integration of renewable energy source i.e., bio-mass, solar etc with power plant has wide reference. However, there are only limited instances of hybridization of solar thermal with a fossil fired power plant.

The prior-art document US7640746 is based on ‘Method and system integrating solar heat into regenerative rankine steam cycle’. The method invented here is to integrate solar thermal energy in a series into the feed water (HP side) system of a Rankine cycle power plant. The novelty of the invention consist of closed loop, single phase fluid system to collect both the solar heat and to provide the heat input into the feed water stream of a regenerative Rankine cycle. In other words, all feed water passed through solar block which is attached in a series with HP heater in Rankine cycle based power plant. In one embodiment of this method mentioned that integrated system allows for automatic balancing of the steam extraction flows from turbine without changing the temperature of the feed-water to the boiler. The concept, used to produce incremental capacity and energy that is powered by solar thermal energy or gives saving of fossil fuel as well. The shortfall of concept is that system become quite dependent on solar block as solar energy is intermittent in nature. To maintain the feed water temperature stability an extra solar field need to be placed for lean or no solar period.

The prior-art document US426248481 titled ‘Gas turbine engine power plant using solar energy as a heat source’ teaches the working medium of a gas turbine engine power plant is heated indirectly by energy derived by solar radiation, the power plant comprising radiant energy collecting means, radiant energy receiving means, radiant energy heat transfer means, a relatively large capacity pressurized heat store and a gas turbine engine in which the compressed air is heated by heat energy in the heat store. Here the disclosed invention is different compare with this invention in terms of thermodynamic cycle and heat transfer fluid as well. Here the hot air is used which is different in disclosed case where oil is used.

The prior-art document US6941759 titled ‘Solar power enhanced combustion turbine power plants and methods’ in which air is cooled using solar energy and supplied to an air inlet of the power plant to support combustion. Also, combustion turbine power plants and methods of operating the same are provided in which steam is produced using solar energy and injected into a turbine of the power plant. Two parallel heating and cooling processes makes system quite complicated and more dependent on intermittent source of energy.

The prior-art document US5727379 teaches that solar heat is used to evaporate the feed-water prior to boiler entrance. This method would then require an expensive solar boiler and is not applicable to rankine cycle using regenerative heating.

The prior-art document US4069674 teaches that the feed-water is bifurcated immediately at the condenser hot well resulting in high temperature solar being used to heat relatively cold feed-water resulting in high entropic losses. Thermodynamically, it is always preferable to add heat at the highest possible temperature. In addition, current technology being explored uses solar heat to evaporate water into steam which is then used to directly provide energy to feed-water heater. This type of technology result in complex and costly equipment when compared to the novelty proposed.

In the year 2009 a US based company has deployed solar thermal power collector system (4.5 MWth) to augment steam production at the ‘Liddell Coal-Fired Power Station’, Australia. But the outcome is that this hybrid system has faced lot many problems in control & instrumentation side.

While all these methods provide some sort of value addition, they are all handicapped by operational limitation, control intricacies or thermodynamic restrictions. In view of the available products and their drawbacks the present inventors after doing an extensive research and experimentations have found that there remains space for developments of new and improved system that has simplified controls and thermodynamically compatible compared to any of the previously studied integration methods. It also poses less operational risk to the existing regenerative steam cycle power plant.

In the view of above mentioned drawbacks and limitations of the existing systems and methods there exists a need to provide an improved and efficient system that provides integration of solar energy in a fossil fired power plant for producing either higher power output for same coal consumption or lower coal consumption for same power output or a combination of both and thereby reducing the CO2 Intensity.

SUMMARY

This summary is provided to introduce concepts related to a system and method therefor providing integration of solar energy in fossil fired power plant and the concepts are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.

A basic object of the present invention is to overcome the disadvantages / drawbacks of the known art.

Another object of the present invention is to provide for the use of solar energy in fossil fired plant for producing either higher power output for same coal consumption or lower coal consumption for same power output or a combination of both and thereby reducing the CO2 Intensity.

Other object of the present invention is to provide for higher efficiency in solar energy to electricity conversion and thereby greater saving of fossil fuel and thus abatement of CO2 emission.

Other object of the present invention is to provide for a simple and cost effective integrated system.

In one implementation, there is provided a system and method for use of solar energy in fossil fired plant for producing either higher power output for same coal consumption or lower coal consumption for same power output or a combination of both and thereby reducing the CO2 Intensity.

According to one aspect of the present invention, there is provided a system that integrate a solar heat exchanger in the feed water circuit parallel to the last regenerative feed water heat exchanger of a fossil fired power plant. A portion of feed water shall be tapped between last and penultimate regenerative feed water heat exchanger and diverted to solar heat exchanger. The heated feed water from solar heat exchanger shall be brought back and mixed with the feed water exiting from the last regenerative feed water heat exchanger. The net effect is that less coal is used to generate a given amount of electricity which in turn also results in reduced carbon dioxide emissions.

Accordingly, in one implementation, a method for generating power by integrating thermal energy derived from solar thermal field across regenerative feed water heater of a fossil fired power plant is disclosed. The method comprises of tapping feed water (102) between three portions, a first portion (105) of said feed water is given to a last regenerative feed water heat exchanger a HP Heater 6 (9), a second portion of said feed water is given to a penultimate regenerative feed water heat exchanger from a HP heater 5 (8), and a third portion (103) of said feed water is diverted to at least one solar heat exchanger (16); heating said third portion (103) of said feed water diverted to said solar heat exchanger (16) by utilizing solar thermal energy to obtain processed feed water; and integrating said processed feed water (104) to a balanced feed water (105’).

In one implementation, a system for generating power by integrating thermal energy derived from solar thermal field across regenerative feed water heater of a fossil fired power plant is disclosed. The system comprises of a HP turbine (2), an HP heater 5 (8); an HP heater 6 (9); and a solar heat exchanger (16. A feed water (102) going to said HP Heater 6 (9) is tapped between three portions, a first portion (105) of said feed water (102) is given to said HP Heater 6 (9), a second portion of said feed water (102) is from said HP heater 5 (8) to a penultimate regenerative feed water heat exchanger, and a third portion (103) of said feed water (102) is diverted to at least one solar heat exchanger (16).
BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.

The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

Figure 1 illustrates the Block diagram of sun radiation utilization system for reduction of the fossil fuel consumption in thermal power plant.

Figure 2 illustrates the Schematic of proposed invention of sun radiation utilization system for reduction of the fossil fuel consumption in thermal power plant.
Figure 3 illustrates the configuration-1 where Solar Heat Exchanger (16).is integrated in parallel with HP heater 6 (9).

Figure 4 illustrates the configuration-2 where Solar Heat Exchanger (16).is integrated in parallel with HP heater 5 (8).

Figure 5 illustrates the configuration-3 where Solar Heat Exchanger (16).is integrated in parallel with LP heater 3 (5).

Figure 6 illustrates the configuration-4 where Solar Heat Exchanger (16).is integrated in parallel with LP heater 2 (4).

Figure 7 illustrates the configuration-5 where Solar Heat Exchanger (16).is integrated in parallel with LP heater 1 (3).

DETAILED DESCRIPTION

The following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are merely a part rather than all of the embodiments of the present invention.

According to one aspect of the present invention, there is provided a system that integrate a solar heat exchanger in the feed water circuit parallel to the last regenerative feed water heat exchanger of a fossil fired power plant. A portion of feed water shall be tapped between last and penultimate regenerative feed water heat exchanger and diverted to solar heat exchanger. The heated feed water from solar heat exchanger shall be brought back and mixed with the feed water exiting from the last regenerative feed water heat exchanger. The net effect is that less coal is used to generate a given amount of electricity which in turn also results in reduced carbon dioxide emissions.

In one implementation, said balanced feed water (105’) is received from said HP Heater 6 (9), wherein balanced feed water (105’) is obtained by treating said first portion (105) of said feed water with steam extracted from said a HP turbine (2).
In one implementation, said solar thermal energy is stored in a concentrated solar block (7) and said solar heat exchanger (16) is configured to transfer said solar thermal energy from concentrated solar block (7) to fossil fired power plant cycle.

In one implementation, a mass flow of said third portion (103) of said feed water to solar heat exchanger is controlled in a manner so that a temperature of said processed feed water (104) and said balanced feed water (105’) are within a prescribed temperature band for different direct solar insolation (DNI) level.
In one implementation, said processed feed water (104) is single phase or phase change media.

Accordingly, in one implementation, a method for generating power by integrating thermal energy derived from solar thermal field across regenerative feed water heater of a fossil fired power plant is disclosed. The method comprises of tapping feed water (102) between three portions, a first portion (105) of said feed water is given to a last regenerative feed water heat exchanger a HP Heater 6 (9), a second portion of said feed water is given to a penultimate regenerative feed water heat exchanger from HP heater 5 (8), and a third portion (103) of said feed water is diverted to at least one solar heat exchanger (16); heating said third portion (103) of said feed water diverted to said solar heat exchanger (16) by utilizing solar thermal energy to obtain processed feed water; and integrating said processed feed water (104) to a balanced feed water (105’).

In one implementation, the system further comprises of a concentrated solar block (7) configured for heating said third portion (103) of said feed water diverted to said solar heat exchanger (16) by utilizing solar thermal energy stored in it to obtain a processed feed water (104).

In one implementation, balanced feed water (105’) is received from said HP Heater 6 (9), wherein balanced feed water (105’) is obtained by treating said first portion (105) of said feed water (102) given to HP Heater 6 (9) with steam extracted from said a HP turbine (2).

In one implementation, the system integrates said processed feed water (104) to said balanced feed water (105’).

In one implementation, said concentrated solar block (7) is configured to receive third portion (103) of said feed water (102), pass through it (201, 202) and heat said third portion (103) of said feed water (102) by utilizing solar thermal energy stored in it to obtain said processed feed water (104) and thereby provides said processed feed water (104) to said solar heat exchanger (16).

In one implementation, said concentrated solar block (7) is parabolic trough, linear Fresnel reflector, heliostat or solar dish

Accordingly in the present invention, a solar thermal hybrid Plant comprises of 2 loops. First loop comprises of solar thermal block, thermic fluid pump, thermal energy storage and necessary pipe and valve work. Second loop comprises of a thermic fluid to feed water solar heat exchanger, control valve and pipe work. The interface point for both the loop is solar heat exchanger. A part of feed water from last regenerative feed water heater inlet is diverted to the solar thermal block where it is heated. This heated feed water is mixed with the balance feed water flowing thru the regenerative feed water heater. Regenerative feed water heater of power plants are of demand flow type. Therefore decrease in the mass flow rate of feed water entering the regenerative feed water heater leads to lower extraction steam flow. This, in turn, reflects in either higher power output for same coal consumption or lower coal consumption for same power output or a combination of both.

The present invention integrate a solar heat exchanger in the feed water circuit parallel to the last regenerative feed water heat exchanger of a fossil fired power plant. A portion of feed water shall be tapped between last and penultimate regenerative feed water heat exchanger and diverted to solar heat exchanger. The heated feed water from solar heat exchanger shall be brought back and mixed with the feed water exiting from the last regenerative feed water heat exchanger. The net effect is that less coal is used to generate a given amount of electricity which in turn also results in reduced carbon dioxide emissions.

Referring now to figure 1 is a block diagram of the proposed invention a certain amount of feed water going to the HP Heater 6, is diverted to and heated in a heat exchanger with hot fluid coming from solar field to a temperature equal to actual HPH-6 outlet temperature at that instant. A maximum variation of 2°C is tolerable between the mixing streams ahead of HPH -6.

In one implementation, figure 1 shows steam extraction from HP turbine (101); feed water from HP heater 5 (102); partial amount of feed water to solar heat exchanger (103); heated feed water from solar heat exchanger (104); feed water in and out with same mass with different enthalpy (105, 105’); heat transfer fluid in to solar field (201); heat transfer fluid out of solar field (202).

The schematic in figure 2 shows embodiment of the desired system used for Rankine cycle based power plant. A location of complete set-up of Concentrated Solar block (7) and solar heat exchanger (16) is clearly shown in fig 2. In a conventional process of feed water heater, water goes to HP heater 5 (8) from Deaerator (6). Then it goes to HP heater 6 (9), where it gets heated by absorbing an enthalpy from steam extracted (2) from HP turbine. Now the invention disclosed here has installed a Solar Heat Exchanger (16) for increasing the feed water temperature coming from HP heater 5 (8) which results the partial reduction of the extraction of the steam from HP turbine. Here the Solar Heat exchanger (16) runs on Concentrated Solar Block (7).

Referring to figure 2, Solar thermal heat is collected trough concentrated solar Power Technology (7). Here the Cold Solar Thermal Fluid (15) heated up in solar block (7). Thermal energy storage could also be envisaged in the system as a small buffer to avoid thermal losses during lean or no solar duration for small interval of time.

In one implementation, figure 2 shows main steam from boiler (1), turbine extraction (2), LP heater 1 (3), LP heater 2 (4), LP heater 3 (5), Deaerator (6), Concentrated solar block (7), HP heater 5 (8), HP heater 6 (9), Generator (10), Condenser (11), Partial feed water flow from HP heater 5 (12), heated feed water (13), Hot Solar thermic Fluid (14), cold solar thermic Fluid (15), solar heat exchanger (16).

Now, a solar heat exchanger is attached to the system parallel to hp heater 6 (9). The hot solar thermal fluid (14) is then transferred to solar heat exchanger (16). This is typical shell & tube type heat exchanger. Here partial feed water flows through hp heater (5) or say upstream of hp heater 6 (9). Since the feed water (12) is at high pressure, it runs at tube side and hot solar fluid (14) runs on shell side of the heat exchanger. In this solar heat exchanger (16), solar thermal energy stored in solar thermic fluid (14) raises the enthalpy of the feed water temperature (12). This heated feed water (13) goes to main line of the feed water and then enters to boiler.

In the feed water side, feed water (12) flow diverted to the Solar Heat exchanger (16) needs to be controlled to match the final temperature of water coming out of the exchanger (13) equal to that of the temperature of water coming out of the HPH 6 at all loads.

In case, for ‘steam / water based Solar Thermal Fluid’ the extraction steam from turbine (2) is at a pressure of x bar, and the corresponding saturation temperature is y°C. To heat-up the bypassed feed water (12) through Solar Heat exchanger (16) to y°C, the steam generated from the concentrated solar block (7) is to be approximately at x bar. If it is less, then the saturation temperature reduces and Feed water (13) cannot be brought to y°C. Hence the pressure of steam generation needs to be controlled accordingly. In case oil based solar thermal fluid is used, only flow of water (12) to the secondary Solar heat exchanger (16) is to be controlled to match the temperature of water (13) coming out of the solar heat exchanger (16). This gives direction to control the extraction of the steam from turbine (2). The reduction of extraction impacts directly on cola consumption and power generation of the plant. The Controls in the solar block can be designed such that they match the temperature of feed water (13) after Solar Heat Exchanger with the feed water coming out from the HP heater-6 (9) within + 2°C tolerance.

The present invention therefore provides a method for generating power by integrating thermal energy derived from solar thermal field across regenerative feed water heater of a fossil fired power plant. The integration of thermal energy is achieved by taking a tap off of feed water from upstream of last regenerative feed water heater, heating it by utilizing solar thermal energy and mixing it back on the downstream side of regenerative feed water heater. The transfer of thermal energy from solar thermal field to fossil fired power plant cycle is thru a solar heat exchanger. The mass flow of feed water to solar heat exchanger is controlled in a manner so that the temperature of feed water heater at the exit of solar heat exchanger and regenerative feed water heater are within a prescribed temperature band for different direct solar insolation (DNI) level. The process fluid of solar thermal field is single phase or phase change media. The solar thermal concentrator is optionally a parabolic trough, linear Fresnel reflector, heliostat or solar dish.

Illustration-1: Dated 30th March: Solar Direct Normal Insolation (DNI) was measured continuously using solar tracker and pyreheliometer and hourly average readings were recorded. The cumulative DNI for the day is 5.491 kWhr/sq.mtr. Total solar thermal energy transferred to feed water works out as 69,247 kWhr. This solar thermal energy results in either additional power generation of 26,321 kWhr or coal saving of 19.26 Tons for the day. Refer Table-1 and Table-2 below:

Illustration-2: Dated 21th April: Cumulative DNI for the day is 4.939 kWhr/sq.mtr. Total solar thermal energy transferred to feed water works out as 66,485 kWhr. This solar thermal energy results in either additional power generation of 25,285 kWhr or coal saving of 18.49 Tons for the day. Refer Table-3 and Table-4 as below:


Illustration-3: Dated 10th Oct: Cumulative DNI for the day is 4.754 kWhr/sq.mtr. Total solar thermal energy transferred to feed water works out as 49,558 kWhr. This solar thermal energy results in either additional power generation of 18,854 kWhr or coal saving of 13.78 Tons for the day. Refer Table-5 and Table-6 as below:

Although the different aspects herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.

Although implementations for a system and method therefor providing integration of solar energy in fossil fired power plant have been described in language specific to structural features and/or methods, it is to be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as examples of implementations for providing integration of solar energy in fossil fired power plant.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.
,CLAIMS:1. A method for generating power by integrating thermal energy derived from solar thermal field across regenerative feed water heater of a fossil fired power plant, said method comprising:
tapping feed water (102) between three portions,
a first portion (105) of said feed water is given to a last regenerative feed water heat exchanger a HP Heater 6 (9);
a second portion of said feed water is drawn from the outlet of penultimate regenerative feed water heat exchanger from HP heater 5 (8); and
a third portion (103) of said feed water is diverted to at least one solar heat exchanger (16);
heating said third portion (103) of said feed water diverted to said solar heat exchanger (16) by utilizing solar thermal energy to obtain processed feed water (104); and
integrating said processed feed water (104) to a balanced feed water (105’).

2. The method as claimed in claim 1, wherein said balanced feed water (105’) is received from said HP Heater 6 (9), wherein balanced feed water (105’) is obtained by treating said first portion (105) of said feed water with steam extracted from said a HP turbine (2).

3. The method as claimed in claim 1 and 2, wherein said solar thermal energy is stored in a concentrated solar block (7) and said solar heat exchanger (16) is configured to transfer said solar thermal energy from concentrated solar block (7) to fossil fired power plant cycle.

4. The method as claimed in claim 1-3, wherein a mass flow of said third portion (103) of said feed water to solar heat exchanger is controlled in a manner so that a temperature of said processed feed water (104) and said balanced feed water (105’) are within a prescribed temperature band for different direct solar insolation (DNI) level.

5. The method as claimed in claim 1-4, wherein third portion (103) of said feed water (102), pass through a heat transfer fluid of solar field (201, 202) and gets heated by utilizing solar thermal energy stored in it to obtain said processed feed water (104), wherein said heat transfer fluid of solar field (201, 202) is single phase or phase change media.

6. A system for generating power by integrating thermal energy derived from solar thermal field across regenerative feed water heater of a fossil fired power plant, said system comprising:
a HP turbine (2);
an HP heater 5 (8);
an HP heater 6 (9); and
a solar heat exchanger (16); wherein,
a feed water (102) going to said HP Heater 6 (9) is tapped between three portions, a first portion (105) of said feed water (102) is given to said HP Heater 6 (9), a second portion of said feed water (102) is drawn from said HP heater 5 (8), and a third portion (103) of said feed water (102) is diverted to at least one solar heat exchanger (16).

7. The system as claimed in claim 6, comprises of a concentrated solar block (7) configured for heating said third portion (103) of said feed water diverted to said solar heat exchanger (16) by utilizing solar thermal energy stored in it to obtain a processed feed water (104).

8. The system as claimed in claims 6 and 7 , wherein a balanced feed water (105’) is received from said HP Heater 6 (9), wherein balanced feed water (105’) is obtained by treating said first portion (105) of said feed water (102) given to said HP Heater 6 (9) with steam extracted from said a HP turbine (2).

9. The system as claimed in claims 6-8 further integrates said processed feed water (104) to said balanced feed water (105’).

10. The system as claimed in claims 6-9, wherein said concentrated solar block (7) is configured to receive third portion (103) of said feed water (102), pass through it (201, 202) and heat said third portion (103) of said feed water (102) by utilizing solar thermal energy stored in it to obtain said processed feed water (104) and thereby provides said processed feed water (104) to said solar heat exchanger (16).

11. The system as claimed in claims 6-9, wherein said concentrated solar block (7) is parabolic trough, linear Fresnel reflector, heliostat or solar dish.