ES2436646A2 - Central tower receiver system. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

A central tower receiver system having a central tower receiver (30), a cold storage tank (10), a hot storage tank (20) at the base of the receiver tower, a downspout (6 ) from the receiver (30) and a riser pipe (7) to the receiver (30). The central tower receiver system has a potential energy recovery system located at the base of the tower configured in such a way that it recovers part of the mechanical energy from the heat transfer fluid and uses it in pumping the working fluid towards the receiver ( 30) and / or supplying power to other equipment of the solar plant in any type of energy.

Description

Field of the Invention This invention is related to solar power generation systems. Specifically, this invention is applied in central tower receiver plants, with central cylindrical receiver or cavity receiver.

BACKGROUND OF THE INVENTION The growing interest in renewable energies and the increase in energy demand have produced a great expansion of electricity generation through solar energy.

The concept of central receiver is based on a field of mirrors with individual solar tracking systems called heliostats, which reflect the incident solar radiation towards the central receiver located at the top of a tower, usually located in the center of the heliostat field. , the central receiver can be either cylindrical or cavity. In this way, direct solar radiation is concentrated in the effective area of the receiver allowing to reach high levels of radiation in it.

All the central receiver configurations are located at the top of the tower, where they are heated with the radiation reflected by the heliostats. Heliostats concentrate radiation and redirect it to the receptor. Normally 80-90 percent of the reflected energy is absorbed and transferred to the working fluid, which is pumped from the base of the tower to the receiver. Central receiver systems typically include two storage tanks, one cold and one hot, located at the bottom of the tower, which provide and store the working fluid that goes to / from the receiver. This technology also consists of a heat energy to electrical energy converter system, consisting of a steam generator, a steam turbine and an electric generator.

The heat transfer fluid can be any medium capable of properly absorbing and transferring heat energy, such as molten salts or high temperature synthetic thermal oils below 750˚C.

The heat transfer fluid is pumped from the cold tank to the top of the tower,

where it circulates through the receiver. At the exit of the receiver, the heat transfer fluid has great

mechanical energy, sum of its kinetic energy (originated by the speed given by the pumps) and its potential energy (as a result of the great height at which the receiver is located).

After leaving the receiver, the working fluid goes down the tower until it reaches the hot tank, where it is stored. Due to the large kinetic energy accumulated at the exit of the tower, it is necessary to dissipate a large part of the energy to avoid problems and possible damage to the storage system. For this reason, a plate system has traditionally been used that produces sufficient pressure loss to remove excess energy in the pipes.

The percentage of energy dissipated in the pressure drop system is important and is not recovered. The invention developed in this document shows various alternatives that can recover about 70 percent of the energy wasted on dissipation.

At the same time, the recovered energy can be used in the pumping of the fluid towards the receiver, thus decreasing the plant's self-consumption. This leads to an improvement in the yield and benefits of the plant.

The concept of this invention and its usefulness have been developed after having a high knowledge of the operation of the central receiver plant.

DESCRIPTION OF THE INVENTION This invention relates to a tower-type solar plant, composed of a central solar receiver located on top of the tower, a cold and a hot storage tank, located at the bottom of the tower, and a system of recovery of potential energy that recovers part of the mechanical energy of the heat transfer fluid that comes down from the tower and then uses that energy recovered in the pumping of the working fluid towards the receiver.

The potential energy recovery system is configured to operate in parallel to the central receiving system - tanks, so it can be coupled or decoupled from the traditional system at any time, in cases of damage to the system or in low-performance processes and under certain circumstances.

On the one hand, for a tower solar plant under normal operation, a set

of valves will communicate the potential energy recovery system with the rest of the circuit. On the other hand, when the use of the potential energy recovery system is not advantageous, the valves will open and the potential energy recovery system will be isolated from the rest of the installation so that the plant works as it currently does.

A central receiver solar plant may have more than one potential energy recovery system operating in parallel.

The potential energy recovery system will generally be located at the bottom of the tower, connected to the receiver's hot fluid drop pipe. It could also be placed anywhere between the receiver and the hot storage tank, or even in more complex configurations between the receiver and the cold storage tank.

The receiver is located in the highest part of the tower, providing the thermal fluid that circulates through it with great potential energy. The objective of the potential energy recovery system is to recover as much of the potential energy from the heat transfer fluid as possible.

The energy recovery system may include: -At least one axial or radial turbine or at least one piston that recovers energy

potential from one fluid to another.

Additionally it can include: -At least one pump that can propel the heat transfer fluid from the cold tank to the

receiver.

In this case, the pump will be mechanically connected, through a clutch and gears, to the turbine, if they are placed relatively close to each other, it will be avoided to use mechanical transmission systems that are too complex. A perfect arrangement to carry out this mechanical connection, or any other, can be just where the hot and cold thermal fluid ducts separate at the bottom of the tower.

The potential energy recovery system must be located at the bottom of the tower

at a point prior to the discharge of the hot fluid, from the receiver, into the tank.

In the case of a magnetic / electrical connection, the potential energy recovery system may include an electric generator capable of transmitting the mechanical energy generated in the turbine / s or the piston / s, to any other component of the system the solar plant

In the case of direct fluid dynamic operation, the potential energy recovery system will be composed of a variety of pistons located between the lowering and the rising ducts configured in such a way that the heat transfer fluid of the lowering duct (hot duct) moves the pistons directly transferring their energy to the working fluid (cold duct) which is pumped into the receiver. In this case the distance between the hot and cold ducts will not be a problem because the potential energy recovery system may include auxiliary ducts that communicate said system with the main ducts.

The objective of the potential energy recovery system is to reduce the self-consumption of the plant with the consequent recovery of the potential energy of the fluid, resulting from the high difference in heights existing in this type of technologies. Therefore, the overall efficiency of the plant will increase as a result of the reduction in the consumption of the components. In addition, in the case of mechanical connections with the pumps that propel the fluid from the cold tank to the receiver, the pump requirements will decrease and may be able to operate under low demand regimes, thus increasing their life time.

BRIEF DESCRIPTION OF THE DRAWINGS A series of drawings that help to better understand the invention and that expressly relate to an embodiment of said invention that is presented as a non-limiting example thereof is described very briefly below.

FIG. 1 is a block diagram describing an example of a central tower receiver system with a potential energy recovery system that includes a turbine and a pump.

FIG. 2 is a block diagram describing an example of a central receiver system of

Electric generator.

FIG. 3 is a block diagram describing an example of a central tower receiver system with a potential energy recovery system that includes a set of pistons.

DETAILED DESCRIPTION OF THE INVENTION In the following detailed description, the described configurations are for example purposes only, so other configurations may be used instead of or combined with the described modalities.

EXAMPLE 1

Figure 1 shows a central tower receiver system 30 in which the potential energy recovery system is a turbine 1 located in the lower part of the tower of the lowering duct 6. In this way, the fluid is conducted through an axial or radial turbine 1, extracting the energy contained in the fluid and transforming it into mechanical energy in the axis of the turbine 1. The pressurized fluid passes through the blades of the turbine reducing its energy. At the same time, this energy will be transmitted through an axis connected to the axis of the pump 2 (it could be more than one) that pumps the cold fluid from the tank to the receiver 30.

In addition, the transmission shaft can have coupling means 3 that can allow the system to be coupled and uncoupled, ensuring proper operation in parallel. It could also include a gearbox that adapts the system to the needs.

EXAMPLE 2

Figure 2 shows another configuration of the invention in which the potential energy recovery system includes:

 An axial or radial turbine 1 connected to the descent duct 6 which extracts the

energy contained in the fluid, transforming it into mechanical energy at the exit of the

turbine shaft 1.

An electric generator 4 which transforms the turbine's energy, both systems communicate through an axis.

The generator will produce electricity that can be used to cover the self-consumption of various elements 8 that make up the central tower solar receiver plant. It is preferable to use it to feed the pump that propels the heat transfer fluid towards the top of the tower. In this way, losses will be reduced due to the reduction of transmission losses.

Optionally, the correct arrangement of the elements that make up this configuration may allow the usual operation process to be reversed. In emergency situations, if the pumps fail, the generator can be transformed into a motor, producing enough mechanical energy to pump fluid from the axial or radial turbine (transformed into a motor) into the receiver 30.

The solid line in Figure 2 shows the operation of the system when it generates electricity. This electricity can be injected into the pumps 9 that feed the receiver 30 or other component by feeding it with electricity.

The dashed line in Figure 2 shows the other configuration discussed above, in which the system is inverted and the turbine 1 and the generator 4 are transformed into a pump and motor respectively, allowing the receiver 30 to be fed in emergency situations.

EXAMPLE 3

Figure 3 shows another configuration of the invention in which the potential energy recovery system, which transforms the mechanical energy of the fluid at the exit of the tower into useful energy for pumping to the receiver 30, is a set of tubes , valves and pistons 5 configured to communicate the two ducts 6, 7 of the tower so that the hot fluid directly transfers its mechanical energy to the cold fluid propelled towards the receiver 30.

Thus, through the natural tendency to balance pressures on both sides of the pistons, the cold fluid will be pumped into the receiver 30 due to the high pressure it has.

5 the hot fluid at the exit of the tower. For example, in the simplest configuration, both fluids will be in the same tube, separated only by a piston, which will balance both pressures.

To guarantee the continuity of the pumping, it will be necessary to have several parallel systems 10, which would produce a uniform flow.

Claims (4)

1. A central tower receiver system comprising: 1a) a central tower receiver (30); 1b) a cold storage tank (10) in a base of the receiver tower (30); 1c) a hot storage tank (20) at the base of the receiver tower (30); 1d) a downpipe (6) from the receiver (30); 1e) a riser pipe (7) to the receiver (30); characterized in that it comprises: 1f) a potential energy recovery system located at the base of the tower configured to recover part of a mechanical energy from a heat transfer fluid from One way selected from: 1f1) pumping a heat transfer fluid to the receiver (30); 1f2) providing power to solar plant equipment in any type of Energy; 1f3) and combinations thereof. 2. A central tower receiver system according to claim 1 characterized in that the potential energy recovery system comprises: 2a) a turbine (1) selected between axial and radial configured to be activated by the heat transfer fluid from the receiver (30); 2b) a pump (2) mechanically connected to the turbine (1) through a clutch and a gear system, configured to pump the heat transfer fluid to the receiver (30). 3. A central tower receiver system according to claim 1 characterized in that the potential energy recovery system comprises: parallel with the central tower receiver system.

3rd)

a turbine (1) selected between axial and radial configured to be activated by the

heat transfer fluid from the receiver (30);

3b)

a pump (2) mechanically connected to the turbine (1) through a clutch and a

gear system, configured to pump the heat transfer fluid to the

receiver (30);

3c)

coupling means (3) configured to allow a

coupling / decoupling of the potential energy recovery system,

guaranteeing the operation of the potential energy recovery system in

4. A central tower receiver system according to claim 1 characterized in that the potential energy recovery system comprises: 5 4a) a turbine (1) selected between axial and radial configured to be activated by the heat transfer fluid from the receiver ( 30); 4b) an electric generator (4) to produce electricity connected to the turbine (1) through an axis. A tower central receiver system according to claim 1 characterized in that the potential energy recovery system is a reversible system.