HRP20080132A2 - Photovoltaic power plant - Google Patents

Abstract

Solar hydro is a new power plant consisting of a modified reversible hydroelectric power plant (3-10) coupled to a photovoltaic power plant (1). Such a power plant, called Solar Hydro Power, is based on the use of solar energy as the only input for solar and hydropower production. In doing so, water accumulation (6) serves for day and seasonal energy storage, thus essentially solving the biggest problem of widespread use of solar energy, namely its storage. The presented Solar Hydroelectric Power Plant is, for the time being, the only permanently sustainable energy source that can continually supply electricity to some consumers, using only natural and renewable energy sources without damaging the environment.

Description

FIELD TO WHICH THE INVENTION RELETS

This invention relates to a new self-sustaining source of electricity which is composed of a solar power plant and a hydroelectric power plant (hence the name solar hydroelectric power plant) for the purpose of continuously supplying electricity to a consumer (house, village, city, island, region, factory, etc.) from renewable energy sources. In this way, a new source of energy, which uses exclusively renewable energy sources, could significantly contribute to the participation in the energy balances of individual countries.

2) TECHNICAL PROBLEM

(for the solution of which a patent application is requested)

Today, the problem of securing ever-increasing amounts of energy necessary for the economic development of every country is evident. On the other hand, over 70% of atmospheric pollution with carbon dioxide (and other greenhouse gases) comes precisely from the energy sector, whereby this pollution has incalculable negative consequences for the Earth's climate (global warming, etc.).

Of all renewable energy sources, solar energy has the greatest potential for use, and the conversion of solar energy into electricity, the so-called, is interesting for this invention. solar photovoltaic systems, i.e. photovoltaic generators.

However, the problems of greater use of solar energy are, on the one hand, related to the relatively high cost of solar plants, and on the other, to the intermittency of solar radiation. And while the prices of solar photovoltaic systems are decreasing day by day (especially with the increase in production and technological progress), the biggest problem still remains the problem of its storage for periods when there is not enough solar energy. Namely, today's solar photovoltaic power plants cannot independently supply any consumption, but they work by only handing over electricity to the power system when solar energy is available.

Therefore, the problem of finding such a technical-technological solution that would use renewable energy sources for the purpose of continuously supplying consumers with electricity is evident. At the same time, consumption can mean not only one residential unit (house), but also smaller or larger settlements, factories, islands, cities, and even the complete supply of the entire country with electricity from renewable energy sources.

3) STATE OF THE ART

(presentation and analysis of known solutions to a defined technical problem)

Until now, there was no technical solution to the same problem. There are solar photovoltaic power plants and there are reversible hydropower plants.

In this patent application, they are combined in an original way into a unique entity called Solar hydroelectric power plant, which, unlike the above (only solar photovoltaic and only reversible hydroelectric power plants), can independently and continuously supply some consumer with electricity and power.

4) PRESENTATION OF THE ESSENCE OF THE INVENTION

(so that the technical problem and its solution can be understood and the indication of technical innovation in relation to the previous state of the art)

The basic concept of the proposed sustainable power plant is a reversible hydroelectric power plant that, instead of electricity from the grid, uses a photovoltaic power plant 1 to run the pumps 4, and which, instead of one, has two separate pipelines, one for pumping 5 and the other for supplying water to the turbine 7 Namely, the photovoltaic power plant converts solar energy into electricity, with which water is then pumped from the available water source 10 to the reservoir 6 located at higher elevations. The water from that reservoir 6 is then used in hydroelectric power plants 8 and 9 for the production of electricity.

On the other hand, the water in the reservoir 6 is accumulated for periods when there is no solar radiation in order to produce electricity from it in that period on the turbines 8, which is then handed over to the electricity distribution network of a settlement or local consumer. In this way, the accumulation 6 is used for daily and seasonal storage of energy obtained during sunny weather by the photovoltaic power plant 1, and this essentially solves the biggest problem of the wider use of solar energy, namely its storage.

The operation of this system implies the achievement of complete independence of the supply of a user with electricity, which is basically obtained from solar energy. The proposed power plant-system is sustainable in every locality and without harmful impact on the environment because it is based exclusively on the use of renewable energy sources and the use of water as the main resource for generating continuous energy production. The formed reservoir 6 and the hydroelectric power plants 8 and 9 belonging to it are very flexible in their operation and energy production and are therefore easily adapted to the needs of users, in contrast to the photovoltaic power plant 1, whose operation and energy production is dependent on solar radiation. The combination of these two power plants results in a new type of power plant suitable for permanent production of electricity. The essential characteristic of this new solar power plant is that it is not limited by size, so it can be used from the smallest to the largest units, i.e. from powering a residential unit of the order of several kilowatts to powerful power plants of the order of dozens or even hundreds of megawatts.

This invention explains the new concept of using solar and hydropower in an original way that respects the advantages of each of them. Hydropower plants 6 and 9 are used for permanent energy production, and solar energy is primarily used for creating hydro potential, i.e. storing water for hydropower production. Solar energy (photovoltaic generator 1) is used to pump water from a lower level 10 (reservoirs, aquifers, seas, lakes, rivers) to a higher level where it is stored in reservoir 6. The stored water is used to produce hydropower in accordance with formed by the hydropotential (height difference) on the turbine 8 from which the water is discharged into the water resource, and from which it was pumped by pumps 4 driven by the photovoltaic generator 1 (picture 1). In this way, it is possible to permanently use the same water that circulates within an artificially created and closed hydrological cycle. The available upper accumulation 6 is actually stored solar energy available for permanent use on the turbine 8 (day and night) in accordance with the needs of consumers.

The proposed power plant is a local source of energy that can be built right next to the place of consumption if all the prerequisites are in place, which is very advantageous because the energy does not need to be transported. The prerequisite for the operation of this power plant is occasional insolation, water and the height difference between the lower and burning water, on which the action of gravity-hydropotential force is exploited. Hydropotential can be formed in accordance with the topographic features of the terrain wherever there is a height difference between the terrain and the hill. However, an artificial hydro potential can be built anywhere by creating an appropriate building structure with a height difference between the lower and upper water. This means that a smaller or larger hydro potential can be created anywhere, with of course different costs. In addition to the necessary height difference where the action of gravity can be used, water is also necessary to start the turbines.

The system can be smaller or larger, open (picture 1) or closed (picture 2), or with smaller or larger water losses. The transport part of systems 5 and 7 is always closed. These are the pressure pipes for transporting water from the lower level to the upper level 5, and the pressure pipeline of the hydroelectric power plant 7. The reservoirs can be closed or open. As a rule, all large systems are open, while small systems can be built as closed. Theoretically, water is only necessary to fill the system and compensate for water losses from the system. The best situation is if recharge and replenishment of losses can be achieved from natural resources, by rain or using rain from the local catchment area, or water from local watercourses, groundwater and the sea. Losses refer to evaporation and seepage of water from the reservoir (upper 6 and lower 10). With appropriate engineering measures, evaporation, and especially leakage from reservoirs, can be significantly reduced or eliminated.

Local natural features, climate, water resources, topography, geology and others are the framework for the realization of the power plant and its productivity. What is important to emphasize is that the power plant is sustainable and as long as there is solar radiation and the force of gravity, the power plant can produce electricity. The price of energy depends on a whole range of elements, and profitability depends on the price of competitive classical sources. At the present moment, it is still to be expected that classic sources of energy (thermal power plants and nuclear power plants) are more competitive, regardless of whether it is clean and renewable energy. However, in the long term, it is to be expected that conventional sources will be more and more expensive, so that the proposed power plant will probably be more and more competitive and profitable. In the case where the long-term sustainability of energy production is sought exclusively with the use of renewable, clean natural resources, the proposed Solar hydroelectric power plant has no competition.

It is very important that the power of photovoltaic generator 1, whose price is the highest, is correctly determined at the Solar Hydropower Plant. The main role in this is played by the upper reservoir 6 (reservoir). The upper reservoir 6 enables the accumulation of water for a longer period of time and thus the production of hydropower, which enables the bridging of the time period when the input of the photovoltaic generator 1 is less or absent. In this way, the photovoltaic generator 1 is selected in accordance with the critical one-year period from a series of years, so that its minimum and maximum powers necessary to ensure the continuity of hydropower production in the critical period (required volume of water) and the selected level of operational safety (additional volume of water in reservoir for incident or unforeseen situations). If there is water upstream of the upper reservoir 6 that can be used, that is, diverted into the reservoir, then the system is more efficient because the water filling of the reservoir 6 takes place naturally and not only with pumps, so the capacity of the solar photovoltaic power plant 1 would be smaller by the corresponding amount. The system will be more efficient if part of the produced solar energy in periods of strong solar radiation is directly used by the user, because then the volume of reservoir 6, the capacity of pumping system 3 and 4 and photovoltaic generator 1 will be smaller.

The total cost of construction is also affected by the costs of building the reservoir (top 6 and bottom 10). Various combinations are possible. It is most favorable when the lower reservoir 10 does not need to be built separately, which is present in the case when the capacity of water resources, which is used for capturing water, is greater than the needs (e.g. when the lower reservoir 10 is represented by the sea, a large river or an aquifer) and when the construction of the upper reservoir 6 is simple and cheap, or if such a reservoir-lake already exists. Hydropower plants 8 and 9 are in principle more economical the higher the available drop (potential energy). However, then a higher power of the photovoltaic generators 1 is needed to pump the water into the reservoir 6.

The proposed power plant has its great advantages because it is a local source of electricity that does not require any supply of raw materials or significant energy transmission to consumers. This means that energy can be produced and consumed in remote locations isolated from traffic and supply routes (islands and the like). In this way, the costs of building transmission systems and the energy losses that occur due to energy transmission are lower. In these locations, the power plant can already be competitive with classic energy sources, because it does not require construction and operating costs related to transportation, nor energy, nor raw materials for energy production. A power plant can be built in all locations where there are water resources, but not adequate hydro potential. By using the photovoltaic generator 1 and the local topography of the terrain, this potential can be artificially created.

This type of power plant is particularly advantageous for the supply of special consumers such as isolated military bases, important strategic facilities in isolated locations and the like because it is completely sustainable locally.

For now, the Solar Hydroelectric Power Plant is the only permanently sustainable energy source that can continuously supply a consumer with electricity, while using only natural and renewable energy sources without harmful impact on the environment.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included in the description and form part of the description of the invention, illustrate the best mode of carrying out the invention thus far considered and help to explain the basic principles of the invention.

Sl. 1. Scheme of the Solar hydroelectric power plant (open type).

Sl. 2. Scheme of the Solar hydroelectric power plant (closed type).

DETAILED DESCRIPTION OF AT LEAST ONE OF THE METHODS OF IMPLEMENTING THE INVENTION

In this part, we will refer to the details of this assumed embodiment of the invention, the basic example of which is illustrated in the attached drawing.

The solar hydropower plant consists of the following elements:

1) Solar photovoltaic power plant (photovoltaic generators),

2) Inverters (direct current to alternating current converters combined with so-called maximum power trackers),

3) Electric motor,

4) Pump,

5) Pipeline through which water rises from the upper level of the lower water to the upper reservoir,

6) Upper reservoir,

7) The pipeline through which the water from the upper reservoir descends towards the upper level of the lower water,

8) Turbine,

9) Generator,

10) Lower reservoir (sea, large river, aquifer, etc.),

The solar hydropower plant works in such a way that solar energy is converted with the help of solar photovoltaic generators 1 into the electricity needed to power the electric motor 3. However, if that electric motor is alternating current, then the direct current electricity from the photovoltaic power plant is converted into alternating current via the inverter 2. As part of inverter 2, the so-called the maximum power tracker, which adjusts the power of the load (electric motor 3) to the power of the photovoltaic power plant 1. The electric motor 3 drives the pump 4, which pumps water from the upper level of the lower water to the upper level of the upper reservoir 6. This transport takes place using the pipeline 5. The water from the upper reservoir through the pipeline 7, it is transported to the turbine 8, which drives the generator 9. After the turbines 8, the water is discharged towards the lower reservoir 10, i.e. the sea, a large river, an aquifer, etc.

Two elements of the proposed solution are the most important, namely: photovoltaic generator 1, because without it there is no generation of hydro potential, and reservoir - accumulation 6, in which water is stored - solar energy for hydropower production when photovoltaic generator 1 is out of order. At the same time, the most expensive element is still the photovoltaic generator 1, and the interest is to reduce its size to the minimum possible. Therefore, in addition to the technological solution of the Solar Hydroelectric Power Plant, it is very important to correctly dimension the system so that it fully meets the needs of consumers for electricity throughout the year. In this sense, it is necessary to use the calculations as follows.

A) Electric power of hydropower plants 8 and 9

Hydro energy generated by a reservoir can be calculated according to:

[image] (J, Ws) (1)

and hydroaccumulation power:

[image] (J/s, W) (2)

where V (m3) is the volume of water in the reservoir, H (m) is the height difference between the lower and upper water, g (m/s2) is the acceleration of gravity, ρ (kg/m3) is the water density, and Q (m3/s) is the flow .

Therefore, the accumulated water, i.e. the size of the accumulation V (m3) and the available height difference H(m) determine the size of the energy production, and the installed capacity of the turbine Q (m3/s) the power. The greater the accumulation and the greater the fall, the greater the energy production. Local conditions related to the construction of the reservoir (volume and height position) will determine which combination of height difference H and water volume V is a better solution for the planned satisfaction of consumer needs - energy production. In addition, the selected drop H and flow rate Q will determine which type of turbine is most efficient. The net electricity that will be produced by the hydroelectric plant is:

[image] (J, Ws) (3)

where Hn is the net available drop, and ηT is the total useful effect of the turbine and generator (0.75 – 0.92).

B) Electric power of photovoltaic power station 1

The selected volume of the reservoir 6 (required energy), height difference (manometric height of water rise) and available time for pumping water into the reservoir 6 determines the required power of the photovoltaic generator 1.

By including the water density ρ and the gravity constant g in equation (1), then converting the units and instead of the volume V by using the symbol QPV, as well as HTE instead of the manometric height H, the total daily hydraulic energy that the photovoltaic power plant 1 can produce at the output of the pumping station can be obtained aggregates:

[image] (kWh) (4)

in which QPV is the mean value of the water volume flow (m3/day) that is pumped from the lower to the upper reservoir, and HTE is the mean manometric height of the water rise (the difference in height from the water level in the upper and lower reservoir + losses) (m).

Initial equation for calculating the required power of photovoltaic generator 1, Pel expressed in (W), under reference conditions (Standard Test Condition STC - intensity of solar radiation 1000 W/m2, relative optical air mass AM1.5 and temperature of photovoltaic generator 250C), which establishes the relationship between output hydraulic energy and aerated solar energy, based on Kenna and Gillett, 1985, has the form:

[image] (W) (5)

where EH (kWh/day) is the output hydraulic energy from the photovoltaic pumping system (1-4), Eel (kWh/day) is the electrical energy at the input to the pumping unit, fm is the load mismatch coefficient to the characteristics of the photovoltaic generator, αc is the efficiency change coefficient with temperature ( 0C-1), T0 reference temperature of the photovoltaic generator (1) (250 C), efficiency of the pump unit (3 and 4) ηMP.

So, the nominal electric power of photovoltaic generator 1 is calculated on the basis of the known demand for hydraulic energy EH and the available value of aerated solar energy ES in the critical period and the known efficiency of the pumping unit (3 and 4) ηMP under the reference conditions of operation, where it is taken in consideration and influence of external temperature on the efficiency of the photovoltaic generator 1.

By inserting equation (4) into equation (5), the expression for the electric power of photovoltaic generator 1 is obtained:

[image] (W) (6)

and which will be used in this patent solution to calculate the electric power of photovoltaic power plant 1.

C) Water and energy balance

The volume of accumulation and production of hydropower and the power of photovoltaic generator 1 and hydropower plants 8 and 9 are determined on the one hand by the natural features of the terrain, and on the other by the needs of energy consumers. Everything is built to meet the needs of some consumer, so the energy consumption regime is a key variable for the sizing and operation of the Solar Hydroelectric Power Plant system. In this invention, the problem in question is solved at the level of the system as a technological unit that includes equally all parts of the system, including natural ones (climate, hydrology, reservoir 6, hydrogen generators 9 and photovoltaic generators 1), the needs of energy consumers, and processes in the system throughout period of system operation.

This means that the system is analyzed as a whole and dynamically throughout the entire period of operation, taking into account all the changes that occur in relation to the available resources (capacity and needs) and energy production needs.

The key components that determine water resources are climate and hydrology. The climate determines, on the one hand, the input of water in the hydroaccumulation 6, and on the other hand, the availability of solar energy. Climatic inputs are of a stochastic character and therefore need to be treated appropriately throughout the period.

Figure 1 shows all inputs (QNAT(i), R(i), QPV(i) and INF(i),) and all water outputs (INF(i), EV(i) and QTG(i)) from the upper accumulation 6 volume V(i), then the air temperature Ta(i), the maximum height of the upper accumulation 6 HU(i), the difference between the lower level of the upper accumulation 6 and the upper level of the lower accumulation 10 (sea) HDIF(i) and the total height on which the photovoltaic plant 1 should raise water to the upper reservoir 6 HTE(s).

Water balance and energy balance are characteristic of the system.

C1) Blanca water

The water balance in the system that has only the upper reservoir 6 for a certain period of time is:

Vin = Vout + Vlosses (7)

where Vin is the volume of water entering the upper reservoir 6, Vout is the volume of water leaving the reservoir 6, and Vlosses represents the total water losses in the upper reservoir 6.

The goal is to reduce losses as much as possible, because this affects the efficiency of the system, that is, the required power of photovoltaic power plant 1.

In the case when the lower reservoir 10 is also used, then water losses in the lower reservoir 10 must also be taken into account, so the water balance in the system is:

Vin - Vlosses, intake = Vout + Vlosses, accumulation (8)

where Vlosses, intake are water losses during water intake, and Vlosses, accumulation are water losses in the upper accumulation 6.

If it is a circulation system with open reservoirs 6 and 10, then in the considered period t it is necessary to compensate the amount of water from:

Vlosses = Vlosses, intake + Vlosses, accumulation (9)

In the case of limited water resources, losses should be reduced to a minimum. In the case of a closed system, the following applies: Vlosses ≈ 0.

Changes in the system are described by the equation of state of the system. The equation of state of the system for the upper reservoir 6 is:

V(i) = V(i-l) +Q PV(i) +Q NAT(i) + R(i) – Q TG(i) + INF (i) (10)

in which the increment i takes the values i=1 to N (N represents the total number of time steps – eg months, decades or days); V(i-1) and V(i) are the volumes of accumulation 6 in the (i-1)-th and i-th periods, respectively (m3); QPV(i) water pumped out by photovoltaic power plant 1 in the i-th time period (m3/day); R(i) total precipitation that reaches the accumulation in the i-th period; QNAT(i) natural inflow from the associated basin in the i-th period; EV(i) amount of water used for evaporation from reservoir 6 in the i-th period (m3); QTG(i) water that is discharged from the upper reservoir 6 towards the turbine/generator plant 8 and 9 for the production of electricity in the i-th period (m3/day) and INF(i) infiltration in the i-th period (m3).

The equation of state at the water catchment is:

W(i) = W(i-1) – QPV(i) – V(losses,intake)(i) + Qinflow (i) (11)

where W(i-1) and W(i) are the water volumes of the lower reservoir 10 in periods i-1 and i respectively, V(losses,intake)(i) are all losses in the intake of water 10 in the i-th period, and Qinflow( i) all inflows lead to intervention 10 in the i-th period. Which variables will describe these processes depends on the type and characteristics of the intervention. In the case of, say, sea capture of 10, both of these variables, as well as volume changes, are negligible. However, in the case of using accumulation 10, the equation is the same as for accumulation 6 above.

The total water balance in the system also includes water in pipelines 5 and 7, which is in principle very small compared to the volume of water in reservoir 6.

C2) Energy balance

On the basis of the above, the total energy balance for a certain period (e.g. a year) in the Solar hydropower plant system can be shown by formulas (a) to (i), i.e.:

(a) The total electrical energy, which is produced in the photovoltaic power plant 1 from irradiated solar energy, can be calculated according to the formula:

[image] (12)

where ηc is the efficiency of photovoltaic generator 1, ηI is the efficiency of inverter 2 (as well as the complete electronic system for adjusting the power of photovoltaic power plant 1 to the power of the load), Ac is the surface of photovoltaic generator 1 and ES is the irradiated solar energy.

(b) This electrical energy is divided into:

[image] (13)

where Eel(PV) is the total electrical energy produced by photovoltaic power plant 1, Eel(MP) is the electrical energy that goes to drive the pump aggregates 3 and 4, and Eel(overhead) is the excess electrical energy that is delivered to the electrical grid if the system is Solarna hydroelectric power plant connected to it. Of course, this surplus of electricity is not necessary to achieve the energy independence of a consumer, but it arises because it is not possible to choose such a size of the photovoltaic power plant 1 that will provide exactly as much energy as that consumer needs in all time periods, but it will necessarily happen that in some periods these surpluses will appear, which cannot be accommodated by the above accumulation 1.

(c) The total available hydraulic energy EH(accumulation) in the upper reservoir 6 is:

[image] (14)

where EH(MP) is the hydraulic energy from pump units 3 and 4 (motor/pump), EH(IN) represents the hydraulic energy of the water inflow, and EH(losses) indicates the losses of hydraulic energy in the system, which can be calculated according to the equation:

EH(losses) = EH(losses, intake) + EH(losses, accumulation) (15)

where EH(losses, intake) represent losses of hydraulic energy during water intake, and EH(losses, accumulation) represent losses of hydraulic energy in the upper accumulation 6.

(d) The connection between the hydraulic and electrical energy of pump units 3 and 4 can be written:

[image] (16)

where ηMP is the efficiency of the pump unit (motor/pump 3 and 4).

(e) The relationship between the electrical and hydraulic energy of the turbine/generator assembly 8 and 9 can be written as:

[image] (17)

where ηTG is the efficiency of the turbine/generator assembly 8 and 9, and Eel(HE) is the total electrical energy produced by the hydroelectric plant 8 and 9.

(f) If first Eel(MP) from sub.(13) is expressed explicitly and then included in sub.(16), we get:

[image] (18)

(g) If unit (18) is included in unit (14), we get:

[image] (19)

(h) And if this unit (19) is included in unit (17), we get:

[image] (20)

(i) By including unit (12) in equation (20) finally yields:

[image] (21)

If it is a closed system (Figure 2), in which energy losses can be ignored, then if the Solar Hydropower Plant is not connected to the external power grid, but only ensures the complete energy independence of a local consumer and if there is no water flow into the upper reservoir 6, then the equation reduces only to the relation:

[image] (22)

in which ηS represents the efficiency of solar energy utilization by pump units 3 and 4, which must be introduced if the amount of energy delivered to the grid is ignored (ie, for Eel(overhead)=0).

If one (22) wants to express depending on the total electrical energy provided by photovoltaic power plant 1, we get:

[image] (23)

In this approximation, equation (22) indicates that the electrical energy Eel (HE) produced by the Solar Hydroelectric Power Plant and handed over to local consumers for the purpose of their complete supply of electrical energy in a certain period of time is directly dependent on the total radiated solar energy ES in the same period of time. period. Eq. (23) shows the dependence of the produced electricity of hydroelectric power plants 8 and 9 on the total electricity produced in photovoltaic power plant 1.

D) Total manometric height of water rise

It is desirable that the net available drop of the hydroelectric power plant 8 and 9 Hn is greater than the manometric head of the pumping unit 3 and 4 of the photovoltaic power plant 1, HTE (Hn > HTE), of course if local conditions allow it. It is obvious that the positive difference between the net available drop of the hydroelectric power plant 8 and 9 and the manometric height of the lifting of the photovoltaic pumping unit 3 and 4, ΔH (ΔH = Hn – HTE), most directly affects the reduction of the power of the photovoltaic power plant 1. Therefore, a good choice of the water intake location 10 and hydropower plants 8 and 9 can significantly reduce the construction costs of the Solar Hydropower Plant, and especially the photovoltaic power plant 1. Normally, this means that the discharged water from the hydropower plants 8 and 9 is not used for pumping into the upper reservoir 6, but is used for these purposes by another water catchment located at higher elevations of the terrain. If the same intake of water 10 is used, then it is always:

[image] (24)

As the total manometric height of the water rise in the reservoir 6 HTE(i) depends on the amount of water QPV(i) that is supplied from the lower reservoir 10 (sea, aquifer, watercourse, etc.), then the amount of water that is drained to the turbines (8 ) QTG(s) and the volume (ie water level) of the upper accumulation 6 V(s), the dependence can be defined:

[image] (25)

which basically represents a functional limitation, which can be approximately written in the form:

[image] (26)

where HU(V(i-1)) and HU(V(i)) are the elevations of the upper water as a function of the water volume of the upper reservoir 6, respectively, and HL(W(i-1)) and HL(W(i)) are the elevations of the upper of water as a function of water volume (W(i-1) and W(i)) of lower reservoir 10 respectively, and HF represents linear and local hydrodynamic losses in system 5 and 7.

E) Determination of the nominal electric power of the photovoltaic power plant 1

In a systematic approach to the problem of determining the optimal nominal electrical power of photovoltaic power plant 1, it is necessary to reformulate Eq. (5) in Eq. (6), in order to express the direct dependence on the amount of water being pumped. However, in order to connect and include the characteristics of other components in the system, it is necessary to first include equation (26) in Eq. (6), then instead of the non-adjustment factor fm in Eq. (6) can use the efficiency of the inverter 2, ηI , which can include the efficiency of the complete electronic system for adapting the load power to the characteristics of the photovoltaic generator 1, and by combining that efficiency with the efficiency of the pump unit 3 i ), ηMP , into one efficiency ηMPI and including it in equation (6), the final relation can be obtained for the calculation of the nominal electric power of photovoltaic power plant 1:

[image] (27)

in which all sizes are already described.

In this approach, for given water output quantities QPV(i) (discretized values of the control variable), the nominal electric power values are calculated using equation (27).

In the above way, the need for water (electricity) in those periods when there is not enough of it in the reservoir 6 and the possibility their coverage by photovoltaic power station 1. Namely, QPV(i) is connected by the water balance equation (10) for the upper reservoir 6 to the characteristics of reservoir 6, the state of the water volume V(i) and V(i-1) and the elements of the local climate (inflow QNAT (i) , precipitation R(i) and evaporation EV(i) and infiltration INF(i)) which determine water deficits in reservoir 6 and which should then be covered by photovoltaic power plant 1.

F) Mathematical model

The calculation methodology is based on dynamic programming, where the complex function of minimizing the maximum electrical power of photovoltaic power plant 1 is used.

Recursive formulas of the optimization process through dynamic programming, for the case of minimizing the maximum objective function, with forward calculation, because the initial conditions are known, can be presented in the form:

In the specific case of optimizing the rated electric power of the photovoltaic power plant 1 that works with the hydroelectric power plant 8 and 9, in which the state variables are represented by the volumes of water in the reservoir (6) V(i) in step i, or V(i-1) in step i- 1, and the control variables QPV(i) are the mean values of the volume of water pumped by photovoltaic power plant 1 in step i, the recursive formulas can be written in the form:

f(i) (V(i)) = MIN { MAX [Pel(i)( QPV(i)), f(i-1)(V(i-1)) ] } , (28)

QPV(s)

under the condition of the state transformation equation (10), the calculation of the nominal electric power Pel(i) according to the equation (27) which represents the size of the return, and with all the mentioned restrictions and the defined time step i, that is, with the already mentioned conditions:

[image]

The values of the state variable in the observed time steps V(i) and previous time steps V(i-1), and the values of the control variable QPV(i), as well as the returns per individual steps Pel(i), are calculated during the process. As an output result, the optimal value of the electrical power of photovoltaic power plant 1 is obtained, which works together with hydropower plants 8 and 9, thus ensuring the independence of the supply of a certain consumer during the observed period. The set of equations (29) represent a mathematical model for determining the optimal nominal power of the photovoltaic power plant 1 working together with the hydro storage 6.

G) Realization of the invention

For the purpose of a detailed description of the concrete way of realizing this invention of the Solar Hydroelectric Power Plant, the model was applied to the power supply of the Island of Vis and neighboring smaller islands. In doing so, input data on electricity consumption during one year (2007) were used, which were obtained by Elektrodalmacija Split (annual sum is 18047.48 MVAh). The total manometric lifting height was taken in the amount of HTE = 215 m. Also, climatological data was taken, i.e. data on solar radiation ES (kW/m2day), air temperature Ta (0C/day), precipitation R (mm/day ) and evaporation EV (mm/day). All these data were obtained from the Croatian Hydrometeorological Institute, for measurements from 1995 - 2006 (while for precipitation, this data is from 1981). Given that there are no natural inflows of the associated watershed into the reservoir on the island of Vis, this size was not taken into consideration (QNAT=0). Due to the assumption that reservoir 6 will be built with impermeable foils, the size of infiltration is also not taken into account (INF=0).

In addition to the above, the volume of water accumulation 6 is also important. For the purposes of complete energy independence (continuous supply of consumers throughout the year), it is determined on the basis of peak energy consumption and the longest time that photovoltaic power plant 1 is expected to be out of operation. Based on data that the highest (peak) consumption of water (energy) from reservoir 6 could amount to 166,233 m3/day and uninterrupted supply of electricity to consumers for 3 to 4 months, the value of the total volume of reservoir 6 is about 20,000,000 m3 , or 20 hm3. So, in the model, reservoir 6 was calculated with an average surface of 1500x700 m (about 100 ha, which is important information for calculating the amount of precipitation and evaporation) and an average depth of 20 m. It is a shallow reservoir 6 in which changes in the water level do not significantly affect on the size of the water surface.

Also, important information is the total manometric height of the water rise, which in the so-called pumping operation (when the photovoltaic power plant 1 pumps water from the sea or underground water 10 into the reservoir 6), for a specific case it is about 235 m.

Therefore, the Solar hydropower plant for the continuous power supply of the Island of Vis should have a peak power of Pel* = 41 MWp. For the power of the PV power plant of 41 MWp (41×100 kWp), with the efficiency of photovoltaic generator 1 of ηoc=16% in reference conditions, it is necessary to foresee a collector field of 250,000 m2 (≈ 25 ha), i.e. about 1250x200 m2.

METHOD OF APPLICATION OF THE INVENTION

By solving the problem of daily and seasonal energy storage with hydro potential, this invention opens up numerous possibilities for the application of such systems, which could strongly stimulate the industry of photovoltaic generators 1 and significantly contribute to the participation of solar energy in the energy balances of individual countries.

This further means that such self-sustainable systems, which would ensure complete energy independence of the supply of electricity to a consumer, i.e. make maximum use of the available solar energy and hydro potential in a certain location, with as little impact on the environment as possible, could have a secure future.

LIST OF CALL SIGNS AND SYMBOLS

1) Solar photovoltaic power plant (photovoltaic generators),

2) Inverters (direct current to alternating current converters combined with so-called maximum power trackers),

3) Electric motor,

4) Pump,

5) Pipeline through which water rises from the upper level of the lower water to the upper reservoir,

6) Upper reservoir,

7) The pipeline through which the water from the upper reservoir descends towards the upper level of the lower water,

8) Turbine,

9) Generator,

10) Lower reservoir (sea, large river, aquifer, etc.),

LIST OF SYMBOLS

• :Eel(HE) – net electrical energy produced by HE (VAs);

• Eel(MP) – electrical energy that the photovoltaic power plant delivers to the pumping unit (Ws);

• Eel (overhead) – electrical energy that the hydroelectric power plant delivers to the electrical network (Ws);

• Eel(PV) – total electrical energy produced by the photovoltaic power plant (Ws);

• EH – hydraulic energy (Ws),

• EH(accumulation) – available hydraulic energy in the upper accumulation (Ws);

• EH (gross) – total hydropower generated by some reservoir (Ws);

• EH(IN) – hydraulic energy of water inflow (Ws);

• EH(losses) – losses of hydraulic energy (Ws);

• EH(losses,accumulated) – losses of hydraulic energy in the upper accumulation (Ws);

• EH(losses, intake) – losses of hydraulic energy during water intake (Ws);

• Es(i) – mean values of solar radiation on a horizontal surface in time period i (terrestrial radiation) (kWh/m2);

• EV(i) – evaporation in time period i (mm);

• fm – adjustment factor of the photovoltaic generator to the characteristics of the load;

• g – gravitational constant (9.81 m/s2);

• H – generally height difference between lower and upper water (m);

• HDIF – difference between the lower level of the upper reservoir and the upper level of the lower reservoir (m);

• HF – linear and local hydrodynamic losses in the system (m);

• HL – elevation of the upper water of the lower reservoir (m);

• Hn – net available drop (m);

• HTE – total height (m);

• HU – upper water level (m);

• i – time period (increment);

• INF(i) – infiltration in time stage i (mm);

• N – total number of time stages i;

• nd(i) – number of days in time period i;

• Pel(i) – nominal electric power of the photovoltaic generator, that is, the photovoltaic power plant in time period i (W);

• PH (gross) – total hydroaccumulation power (W);

• Q - general water flow (m3/s);

• Q(inflow) - all water inflows to the intake (m3);

• QMAX – maximum value of water that can be pumped out by the engine/pump plant in a certain period (m3);

• QNAT(i) – natural inflow from the associated watershed in time stage i (m3);

• QPV(i) – water pumped by the photovoltaic power plant into the upper reservoir (decision variable in time period i) (m3);

• QTG(i) – amount of water that is drained to turbines in time stage i (m3);

• R(i) – total precipitation in time period i (mm);

• T0 – reference temperature of photovoltaic cells (generator) (250C);

• Ta(i) – ambient temperature in time period i (0C);

• Tcell(i) – temperature of the photovoltaic generator in time period i (0C);

• V – general volume of water in the reservoir (m3);

• V(i) – volume of the upper reservoir in time period i (m3);

• V(i-1) – upper accumulation volume in time period i-1;

• V(losses) – total water losses in the upper reservoir (m3);

• V(losses,accumulated) – water losses in the upper reservoir (m3);

• V(losses, intake) – water losses during water intake (m3);

• Vin – volume of water entering the upper reservoir (m3);

• VMAX – maximum volume of the upper reservoir (m3);

• VMIN – minimum volume of the upper reservoir (m3);

• VN – volume of the upper reservoir in the last step (m3);

• Vout – volume of water leaving the upper reservoir (m3);

• W(i) – volume of the lower reservoir in time period i (m3);

• W(i-1) – volume of the lower reservoir in time period i-1 (m3);

• αc – temperature coefficient of PV cells (generator) (0C-1);

• ηHE – hydropower plant efficiency (%);

• ηI – inverter efficiency (%);

• ηMP – efficiency of the motor and pump assembly (%);

• ηMPI – motor, pump and inverter efficiency (%);

• ηoc – nominal efficiency of the photovoltaic generator (%);

• ηS - efficiency of solar energy utilization by the pump unit (%);

• ηTG – total efficiency of the turbine and generator assembly (%);

• ρ – density of water (1000 kg/m3);

Claims (6)

1. The solar hydroelectric power plant, characterized by it, consists of a photovoltaic generator (1), an inverter (2), an electric motor (3), a pump (4), one or more water reservoirs (6 and 10), pipelines (5) for water pumping from the lower reservoir (10) to the upper one (6), pipeline (7) through which water is released from the upper (6) to the lower reservoir (10), turbine (8) and generator (9). 2. Solar hydroelectric power plant according to the 1st requirement, characterized by the fact that it serves for the continuous supply of electricity to a consumer. 3. The solar hydropower plant according to requirements 1 and 2, characterized by the fact that it has the upper (6) and lower (10) reservoirs open, represents the so-called open type Solar hydroelectric power plant. 4. The solar hydropower plant according to claim 1 and 2, characterized by the fact that it has the upper (6) and lower (10) closed reservoirs, represents the so-called closed type Solar hydroelectric power plant. 5. The solar hydropower plant according to claim 1 and 2, characterized by having one open (6 or 10) and one closed (6 or 10) reservoir, represents the so-called combined type of Solar hydroelectric power plant. 6. Solar hydroelectric power plant, according to claim 1-5, characterized by the fact that the size of the photovoltaic generator (1) is determined on the basis of the presented mathematical model.