WO2009060245A1

WO2009060245A1 - Solar power plant with short diffuser

Info

Publication number: WO2009060245A1
Application number: PCT/HR2007/000037
Authority: WO
Inventors: Neven Ninic; Sandro Nizetic
Original assignee: Neven Ninic; Sandro Nizetic
Priority date: 2007-11-09
Filing date: 2007-11-09
Publication date: 2009-05-14

Abstract

Solar power plant with short solar chimney called diffuser (D) utilises the air's ability to do work after its passing through the solar collector (S). A part of this work is used to power the turbines (10), the rest for maintaining a particular stream structure above the diffuser called gravitational vortex column. This structure maintains lower pressure behind the turbines that it would be achieved by any solid solar chimney, thus producing larger useful power of the turbines. In the diffuser there are fitted special water nozzles (9) that enable starting of the plant and help maintaining its stationary operation.

Description

SOLAR POWER PLANT WITH SHORT DIFFUSER

INVENTION DESCRIPTION

1. FIELD OF APPLICATION

In the International Patent Classification, this patent is by its basic application classified as F 03 G6/00 - Devices for producing mechanical power from the solar energy.

2. TECHNICAL PROBLEM

Solar power plants with high solar chimneys involve high investments per installed kW. Such power plants are of very large dimensions, because the solar radiation is a very "dispersed" source of power. The low-temperature solar radiation heat is collected from a large area of ground with air solar collectors of large diameters, the heat power being concentrated in the form of available part (availability) of air energy in the centre of the collector by means of a very tall solar chimney. The large diameter collector and the solar chimney make very expensive structures, whereas the total degree of efficiency of such a solar power plant is very low - around 1.5%.

The technical problem solved by this invention relates to the solar power plant with a large-diameter solar collector and with a device that will form a high vortex extension of the short solar chimney, to power the turbines. Such a power plant will be less costing and will have a high efficiency degree relative to the existing solar power plants with high solar chimneys. 3. STATE OF THE ART

The basic experiences about solar power plants with solar chimneys have been gathered in a relatively small experimental 50 kW plant in Manzanares (Spain, late 1980s). Their work is based upon air entering peripherally, radially, into the dish- shaped ground solar collector, getting heated in it and entering into the solar chimney in the middle of the collector. At the bottom of the chimney, the air pressure is lower that in the surrounding atmosphere, because the chimney in the stationary operation is full of warm air. This enables fitting of one or more turbines in the bottom of the chimney, powered by the above mentioned difference in pressures.

For several years now, there have been developed projects of commercial power plants of this type. According to such a project, the first large solar power plant with solar chimney is being built in Mildura desert, Australia. Its nominal power is 200 MW, obtained from a 7000 m diameter solar collector. Its solar chimney is 1000 m high and 170 m in diameter, which makes it a financially, technically and in terms of safety, a very significant part of the project (about one half of the total investment).

4. DISCLOSURE OF THE INVENTION

The invention is the solar power plant with short diffuser and low-temperature solar collector through which a stream of warm air flows to the air turbines, where above the diffuser forms a complex vortex stream field, similar to a tornado funnel, here referred to as the gravitational vortex column (GVC). In this column the air from the turbines moves circularly and upward, thus forming a sort of vertical fluid "bottle" inside which, due to the rotation, the pressure is lower than at the same altitude in the atmosphere. The mentioned radial pressure difference is greater at the bottom of the fluid bottle, so that near the ground level - immediately above the turbines - the pressure is significantly lower than the atmospheric one. The above described vortex stream field acts like an extended solar chimney, creating operating conditions for the turbines. 5. ILLUSTRATION DESCRIPTIONS

Figure 1. shows the solar power plant with short diffuser - front view

Figure 2. shows the solar power plant with short diffuser - top view

Figure 3. shows the solar power plant with short diffuser - cross section A-A in the

Figure 2. Figure 4. shows the solar power plant with short diffuser - cross section B-B in the

Figure 1. Figure 5. shows the solar power plant with short diffuser - cross section C-C in the

Figure 1.

6. DESCRIPTION OF A POSSIBLE INVENTION EMBODIMENT AND OPERATION

The solar power plant with short diffuser, Figures 1 , 2, 3, 4, 5, comprises: the solar collector S, the spiral canals S conducting warm air to the turbines, the short diffuser D, the diffuser deflector F, the axial air turbines 10, the generators 12, the circulation water pumps 8, the nozzles 9, the canal with air moistening water 13, and the canal collecting rainwater from the collector 14. The solar collector S has the glass cover 1 , mildly inclined towards the outer edge of the collector, positioned above the absorbing ground 2. Between the collector cover 1 and the absorbing ground 2, there are the spiral canals E, with guides 3 guiding the heated air to the air turbines 10. The short diffuser is positioned vertically in the middle of the solar collector S. The short diffuser D has the neck 4 and the body 5 with the opening 6.

The diffuser deflector F makes the central inner part of the short diffuser, and is placed in the lower, narrower, part of the diffuser, lifted above the upper level of the air turbines. The upper surface 7 of the diffuser deflector is concave shaped, to direct atmospheric air cold streams. Between the diffuser deflector and the body 5 of the short diffuser, there is the narrowed inner space of the neck 4, where there are several groups of axial air turbines 10. In the solar power plant with short diffuser, the surrounding air flows between the glass cover 1 of the solar collector and the absorbing ground 2, heats up, accelerates through the spiral canals E and arrives to the turbines 10. Having passed through the turbines, the air current is directed tangentially and upwards through the diffuser neck 4, to the diffuser exit 6 and into the atmosphere 15. The invention is based upon the existence of the atmospheric height energy potential. This is the availability of the warm, ground air, resulting from the air's thermodynamic misbalance relative to the surrounding atmosphere above the plant. More precisely, it is about utilisation of only that part of the availability that relates to the mechanical misbalance, as a part of the total thermodynamic misbalance of the warm air and the atmosphere. This usable part of the availability will be referred to here as "the collector air height potential" or, still shorter, "the potential". If the collector air does not rise freely in the atmosphere, but through the solar chimneys of the height H_c, than the mechanical misbalance, producing the work, is not distributed by the entire height 0 < z < h_c, but concentrates in the chimney bottom, where there is the pressure difference that drives the turbines. The invention differs from the existing solar power plants with high solar chimneys in that pressure in the ground-level turbines is lowered not by a solid solar chimney of the height H₀, but by just a short diffuser, above which is the already described particular vortex stream field, appearing like a tornado funnel, of the total reached height H_max » H_c.

A solar power plant with short diffuser can be calculated to have the largest available height H_max equivalent to as much as the entire troposphere, around 10000 m. Since an important part of the process runs above the short diffuser, that is, outside the solid part of the plant, the operation of the invention also includes the GVC induced in the short diffuser. The GVC structure is described herebelow. In the stationary operating regime, as described hereabove, the air passes through the groups of (in this embodiment) three turbines producing work, and passes through the diffuser neck and the very diffuser at speeds that at the diffuser exit form a rotating air stream 15 of annular cross section that rises as a spiral - theoretically to the top of the troposphere. Inside this rotating updraft of warm air, there is a relatively low pressure, lower that the atmospheric one at the same altitude. Therefore, from the upper parts of the troposphere and through the central part of the GVC descends the relatively cold air 16, to mix with the warm air in the diffuser zone and with it to form the already mentioned rotating rising current above the diffuser. It is this contact and mixing with the cold air that enables the air that has passed through the turbines to regain the total (stagnation) pressure, equal to the atmospheric one.

Cooling and contraction of air volume immediately behind the turbines is essential for operation of the invention.

In the starting stage, before reaching the stationary regime, the effect of air contraction behind the turbines is achieved by water injection and evaporation by means of the nozzles 9 situated behind the turbines 10. Following initiating the descend of the cold air in the central part of the GVC, water injecting may but does not have to be continued.

Here are explanations of certain embodiment details related to the variant described and shown in the illustrations. Figure 1. shows the front view of the invention, Figure 2. showing its top view. Figure 3. shows the plant cross section A-A in the Figure 2. The GVC flow is illustrated by the arrows 15 and 16. The very plant comprises the transparent, glass, cover 1 and the absorbing ground 2, passing towards its centre into the spiral canals E with air guides 3. In their part in front of the turbines, the canals are bent in order to direct the turbine air tangentially and slightly upward. Figure 4. shows the horizontal cross section B-B, showing the turbines 10, situated practically in the very exit cross section of the canal E. Details of location of the turbines in the exit part of the canal are not essential for functioning of the invention and are not shown in detail in the illustrations. It is important just that all the air passes through the turbines, and that in front of and behind them it is directed tangentially and slightly upward. Figure 5. shows the horizontal cross section C-C, just below the turbines. The spiral canals E are shown only to the radius where they slightly rise above the horizontal level before the entrance into the turbines 10. The three turbines in each canal are the inner (at the smallest radius), the middle and the outer. The turbines drive the electricity generators 12 via the transmission mechanisms 11. From the turbines, in their axes direction, exit air flows with various circular components of velocity (w_ct) relative to the plant axis. The lowest velocities are from the outer turbines, farthest from the plant axis, and the largest from the inner ones, closest to the axis, the product R_tw_ct for all the turbines being equal. This, of course, creates unequal pressures behind the turbines: the largest being after the outer ones, and the smallest behind the inner ones. This forms the air spiral updraft entering from the turbines into the space of the neck 4 after the turbines. The vertical components of velocity are homogenous over the entire diffuser neck cross section. Behind the neck there are the nozzles 9 injecting the liquid, dispersed water, in the direction of the air stream. Other parts of the injection system are the circulation pump 8 and the piping connecting the nozzles 9 and the water canal 13.

A variant of the invention, differing from the above described one, is a plant using as its heat source not the solar radiation but waste heat of a classic or nuclear power plant of any type. This plant would have a special heat and moisture exchanger instead of the collector. In this variant, the invention replaces the large cooling tower with natural circulation of the classic or nuclear power plant. Thereby, it would practically decrease the temperature of its thermal sink from the ground-level atmospheric air temperature to the upper troposphere temperature.

The referral marks used in the invention description and illustrations have the following meanings:

S - solar collector

1 - glass cover

2 - absorbing ground

E - spiral canals

3 - air guides D - short d iff user

4 - d iff user neck

5 - d iff user body

6 - diffuser exit opening

F - diffuser deflector

7 - deflector surface

8 - circulation pumps

9 - nozzles

10 - axial air turbines

11 - transmission mechanism

12 - electricity generators

13 - canal with water moisturising the warm air

14 - rainwater collecting canal

GVC - gravitational vortex column

15 - warm air stream

16 - cold air stream

7. INVENTION APPLICATION

The basic invention application is a solar power plant producing work from heat of a low-temperature air solar collector.

The solar collector's glass cover can also be used for collecting of rainwater, the space under the cover also for agriculture and drying of agricultural products. The plant may also be used without the low-temperature solar collector. In that case the heat source would be the cooling water from any thermal power plant, either in dry or wet contact with the atmospheric air. Dry contact of the cooling water with the atmospheric air, water being injected behind the turbines, would be adequate to the plant starting period, whereas in the stationary drive it would be combined, or possibly with no water injection behind the turbines at all.

Claims

PATENT CLAIMS

1. Solar power plant with short diffuser and with low-temperature solar collector through which air flows to air turbines, wh e re in it comprises: the low- temperature solar collector (S) the glass cover, being positioned inclined relative to the absorbing ground (2), including the short diffuser (D) positioned in the centre of the solar collector, with the upward exit opening (6), including the diffuser deflector (F) forming with the body (5) of the short diffuser (D) the neck (4) housing the turbines (10) into which, through the spiral canals (E) flows the warm air from under the glass cover (1) of the solar collector, so that at the turbine exit, in the diffuser neck (4), it forms a rising vortex annular stream of warm air, into which water is injected and which flows towards the diffuser exit opening (6) so that it, theoretically, reaches the top of the troposphere, forming a rising vortex stream of annular cross section (15) through the centre of which descends a stream of cold atmospheric air (16), mixed in the diffuser zone with the air from the turbines, with it to form the already mentioned vortex updraft.