CA2691140A1 - Integrated ocean desalination, ice slurry creation and thermal cogeneration system for existing thermal plants - Google Patents

Description

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Integrated Ocean Desalination, Ice Slurry Creation and Thermal Cogeneration System for Existing Thermal Plants Abstract The proposed system consists of an offshore deep-water pump, seawater desalination system, and ice-water slurry creation system, a tube carrying freshwater to the shore and a thermal cogeneration power plant on the shore adjacent to existing power plants. The objective is to provide a large amount of cooling in a reduced amount of coolant flow while respecting strict new environmental directives. The system will increase the efficiency of existing power and desalination plants. The system will result in low-cost electricity production and provide fresh water for sale on utilities markets. A first model describing system operation is presented in detail, and parameters leading to system optimization are discussed, along with recommendations on the next steps that need to be taken to advance the project.

1. Introduction Traditionally, thermal power plants have built near the ocean shore, enabling power plant designers to use the large cooling potential available due to the ocean's thermal inertia.
However, public concerns regarding the marine ecosystem have given way to new regulations in certain states, forcing thermal plant and desalinating plant administrators to re-evaluate their cooling techniques. Simply rejecting hot, salty brine into the sea is no longer acceptable; new approaches to the problem must be found.

In certain parts of the world, a secondary need exists simultaneously, that of providing fresh water in the region. Therefore, an inter-linked system which could potentially answer both requirements simultaneously would become very interesting.

The system described in this paper was designed by EH2solar Technologies and was created in order to achieve those objectives. A description of the system is presented, followed by a mathematical model describing the system, conclusions and recommendations for future work.

2. System Description The system presented on Figure 1 includes an operational platform located offshore on which a reverse osmosis desalination system and an ice slurry creation system are operated. This platform draws cold seawater from a certain depth with a submerged vertical pipe, and sends cold, fresh ice-water slurry to thermal plants located near the shore.
Mote Desalination 0,15 MPa Power Ice Creation Generation (Butane) MW

Lp La,o.y T= 5 C 1 /

Figure 1 : Offshore Desalination, Ice-water Slurry and Onshore Cogeneration System Water temperatures in the sea generally vary with depth. Water at the surface is heated by the sun and other climatic factors, is therefore less dense and tends to remain at the surface.
Colder, denser water is naturally found at greater depths. This phenomenon leads to natural temperature stratifications, otherwise known as thermoclines. It can therefore be demonstrated that it would be advantageous to raise this cold water to the surface in order to use it as a way to discard energy from processes located at the surface.

In this system, a pipe with a suggested length of 1000 meters brings deep water directly to the surface in a thermally insulated pipe and protected from intrusions from marine life and other residues.

Once the cold seawater is on the platform, it is introduced in a reverse osmosis desalination system. The shape of this system is based on the system described by Gilau &
Small [1 ], as seen in Figure 2. Their model demonstrates that it is possible to attain very advantageous energy costs of 2.33 kWh/m3 of desalinated water, with a reliable and relatively simple system.

The desalinated water is sent to an ice-water slurry creation l st stage system. The concentrate which Low pressure membranes is rejected from the SYstem Feed water pump P Q5 Po't t ~. Treatment salty water brine which is still Qi L___J
cold, is also sent to the ice l're~rco-,unen, Rx creation system, where it will Q~ r'r_ "`' b Qi m~mhi ancs pressuee act as coolant. Kith Pu,,.i,(Booster) RFZ ~' The ice slurry creation system is similar to the system used in rx Ql P,4 Product!
the experiments described by C'oncenrr<,te P"rneate Energy water Bellas, Tassou & Chaer [2]. The Recovery cost of ice slurry creation has TLnb;ne been directly evaluated in terms Figure 2: Reverse Osmosis Desalination System of the efficiency of an ammonia refrigeration system for the moment. Since the temperature difference between the evaporator and the condenser in this system is relatively low, ice can be created at very little cost.

The system is cooled by the brine from the previous system mixed with a secondary cold water flow raised from ocean depths. This mix, which has already reduced the saline concentration in the discarded water, is then rejected at a shallow depth, at a considerable distance from the ocean floor. The salt in the brine spreads itself in the ocean over great distances, avoiding any issues with marine life at the bottom.

The percentage of ice in the slurry will be optimized with respect to the amount of additional cooling available for processes versus additional pumping costs brought on by an increase in apparent viscosity due to the presence of slurry in the pipes.
~s k The mix is sent to the shore in a large, ITJ
insulated pipe either running horizontally 30 meters below the surface, or on the bottom N
of the sea floor. The depth of the first pipe is such that it does not inhibit maritime traffic }
or present an eyesore near the coast. This pipe can be attached to buoys which are kept in place by deep water cables. Figure 3: Ice-water Slurry Installations such as these exist in other systems in the world and can be studied in order to adopt them in the system.
The technology for the second proposal for a water pipe, which runs on the ocean floor, can be directly borrowed from gas pipeline technology currently in use today.

Once the ice-water mix arrives on the shore, it is sent to an on-shore thermal plant, acting as coolant for a secondary cogeneration Rankin cycle running on butane or ammonia, using

3 discarded thermal energy from the plant as a heat source for the boiler. The use of the ice-water mix allows the condensation pressure to be lowered down to 0 C, reducing the pressure exiting the turbine and therefore increasing the efficiency of the cycle.
Also, once the ice is melted and sensible cooling takes place, the higher heat capacity of fresh water automatically increases the heat transfer in the condenser, reducing the required flow for equivalent seawater cooling.

The cogeneration power cycle creates a considerable amount of electrical energy which can be transmitted to the desalination, ice slurry creation or transport processes, and remaining quantities of energy can be sold to the local power grid. Once the freshwater slurry has melted in the condenser, it can then be sold to local water markets.

3. Use of an iced seawater centrifugal desalination system and potential benefits to the overall system.

A newer form of desalination is currently being explored, namely the use of centrifugal desalination of sea ice. This technology is gaining interest in population centres located in northern latitudes, and could become a viable alternative for desalination in the years to come.
An overview of the quality and economic benefits of sea ice desalination was made by Xie &
al. [3]. In their paper, they compare results between experiments with centrifugal, slight-melting and reverse osmosis desalination.

When seawater is exposed to temperatures below the freezing point and turned to ice, most salt ionic species contained in the seawater are so large that they are not easily incorporated in the ice crystal lattice. For this reason, most salts are transferred into the underlying ocean and only parts of them are retained in the volume of ice in so-called brine pockets.

Centrifugal desalination consists in harvesting sea ice and submitting it to centrifugal forces, effectively draining the brine from the ice. The brine is therefore separated from the ice, which is melted into fresh water. Results show that this method of desalination can reduce the salinity of sea ice salinity of 3%-8% to 0.2%-2% at reasonable costs.

Since ice creation is already included in the ice-slurry cooling system described in the first part of this text, a combination of both technologies could potentially be used, in which the freshwater ice collected from the centrifugal desalination system can be sent directly into the pipes leading to the shore. A percentage of fresh water required for the transportation of the fresh ice-water slurry can either be partially redirected from the shore (exiting from the cogeneration plant) or desalinated on the platform from additional seawater with a supplementary reverse osmosis system.

As discussed in this text, many different desalination and cooling options exist to provide solutions to the problems described above. Many variations on the proposed solutions can be undertaken in order to design an optimal solution and achieve these goals in a feasible and cost-effective manner, respecting all environmental and social regulations.

4 4. System Model As discussed above, the proposed system includes deep seawater pumping, a desalination system and ice-water slurry creation system on an ocean platform, a slurry transport pipe between the platform and the shore and a cogeneration system adjacent to existing thermal power plants. The energy source driving the system is saturated vapour exiting the existing plants at 120 C and 0.15 MPa.

For the time being, all values have been calculated without operational isenthalpic or isentropic losses (pumps, compressors), meaning all efficiencies are theoretical. Future evaluations will include realistic losses.

4.1 Deep Seawater Pump Since the seawater pipe is submerged vertically in the ocean, the only energy which needs to be provided would be used to counter the effects of wall friction inside the pipe. Therefore, the Bernoulli equation regulating pipe flow is reduced to the following equation:

y, WP '1 mp,19 Where, hp,1 head loss in this first pipe (m), Wp,1 pumping power required to overcome this loss (W), mm,1 seawater flow in the pipe (kg/s), g gravitational acceleration, 9.81 (m/s2).

Meanwhile, head losses for fully developed incompressible flows in a pipe are calculated with the Darcy-Weisbach equation:

_ 1 V2 hp'1 = f d 2g Where, f friction factor, I pipe length (m) V seawater velocity (m/s), d pipe diameter (m).

Since the pipe has a circular diameter, the term for seawater velocity can be rearranged as a function of flow:

47 (m V=A= Pnd2 \S~

In turbulent flows, the friction factor (f) can be approximated by Haalands [4] approximation of the Colebrook equation, which isolates f and avoids using circular iteration loops:

f - 1.11 E 1d) 9 -1.81og 3.7 + Re Where, e pipe roughness, 4.5 x 10"5 for commercial steel (m), Re Reynolds number, equal to:

Re = pVd - 4rhp,i rrd For regular seawater, p density, 1024 (kg/m3), ,u viscosity, 1.68 x 10"3 (Pa=s).

Combining all the above equations leads to a general equation for pipe flow under these conditions as a function of seawater flow and pipe diameter and length:

- - l (th ,1ll ~W ) p.1 - E 0.2 25 pZd52 log [()1.h1 + 1.7m5 >zd p,l 4.2 Desalinisation In the article describing their desalination system, Gilau & Small [1] mention potential global reverse osmosis desalination energy costs at 2.33 kWh/m3 of desalinated water.
With the objective of using a similar system, this value is used in this evaluation.
Converting to kJ/kg of fresh water:

kWh s 1 m3 kJ
Wdesal = 2.33 ;w3- X 3600 h X 998 k = 8.4 k In their article, the authors roughly figure that 40% of the initial seawater flow is desalted, and the remaining water is rejected as brine.

lhw = 0.4 inp,l rim = (1 - 0.4) in.p,l Where, mw desalinated water flow (kg/s), mb brine flow (kg/s), Replacing, desalination power can be calculated in function of pumped seawater.
Wdesai = 8.4 rn.w = 3.36 inp,1 (W) 4.3 Ice-water Slurry Creation The newly desalinated water is sent to an ammonia refrigeration system, transforming the water into ice-water slurry that will be sent to the shore. The refrigeration cycle has been drawn with respect to condensing temperatures available with cold brine and seawater cooling. The system is represented on the Mollier chart in Appendix 1.

The ammonia refrigeration system is shown in the in Figure 4, with temperature, pressure and enthalpy shown at specific points in the system.

Desalinated Water mw = rn kg/s Tw,2 = 0 'C
T,, = 5 'C xw.2 = 25 % ice EVAPORATOR
P2 = 0.35 Mpa P4 = 0.35 Mpa T, = -5 'C T4 = -5 'C
h, = 490 kJ/kg h4= -725 kJ/kg AMMONIA

Wcom ressar = 6.42 * ma, kW COMP

P2 = 0.6 Mpa P3 = 0.6 Mpa T2 = 30 'C T3 = 10 'C
h2 = 565 kJ/kg h3 = -725 kJ/kg CONDENSER
T5,2 = 10 'C sea water Ts,' = 5 'C
m, = (mb+ mp,2) kg/s Figure 4: Ammonia Ice Slurry Creation System Heat rejected from the ammonia in the condenser is gained by the seawater, whose flows include the brine from the desalination system and additional cold water from the sea.
Theoretical equations for heat transfer and mass flows in the condenser are the following:

7Yts = (m.b + mp,2) gcond = mam(h2 - h3) = 7it5Cps(Ts,2 - TS,1) (kW) mam(565 - (-725)) = Tits = 3.85(10 - 5) Tits mar 33.5 The desalinated water is turned into an ice-water mixture. The amount of thermal energy gained by the evaporating ammonia depends on the water flow and the desired fraction of ice (x) exiting the evaporator.

Qevap = mam(hi - h4) = mw[Cpw(Tw,1 - Tw,2) + xhf9 ] (kW) 7itam(490 - (-725)) = mw[4.181(5 - 0) + X = 333 ]
11tam = ?hw(0.274x + 0.0172) The compressor power is calculated as a function of the flow of ammonia in the system, which can be calculated as a function of other flows with the equations which are written above.
Wcomp = roam(h2 - hl) Wcomp = [mw(0.274x + 0.0172)1(565 - 490) Wcomp = mw(20.55x + 1.29) (kW) 4.4 Ice Transport in Horizontal Pipe The ice-water slurry created in the ammonia system is transported to the shore in a submerged, horizontal pipe. The equations are similar to those used in the vertical pipe, with the exception that the apparent viscosity is modified due to the presence of ice in the system.
Hirochi [5] has created correlations which adjust the pressure losses due to such flows.

Pressure loss data from Hirochi's experiments were plotted against the flows' Froude number, a dimensionless number comparing inertia and gravitational forces, which is defined by the following equation:

Fr = 9d11 - Pice/
Pw I

The pressure loss coefficient is defined by the following:
= (tmix - tw) xlw Where, im;X pressure drop per unit length for the mixture flow, iW is the pressure drop per unit length for water flow.

Finally, plotting one against the other results in the following correlation:
0 = -0.5 + 23Fr-0.82 The head loss due to the presence of ice in the flow is then adjusted:
hl.mix = hl,w(1 + Ox) (m) The required pressure needed to carry the slurry in the pipe is calculated along with the required pumping power:

Ptransp = 1 exit + p9 (TV
+ hl.mix Ptransp - Pamb Wtransp = mu, (W) P
4.5 Cogeneration Cycle Once the ice-water slurry from the previous system has reached the shore in the pipe, it is sent to a butane cogeneration cycle for cooling. The heat source in this cycle is hot vapour at 120 C
and 0.15 MPa which is rejected from a thermal power plant located near the ocean. The cycle is represented on a pressure-enthalpy diagram in Appendix 2 and is detailed in Figure 5.

Plant waste water m = mt. kg/s T41 = 120 C Tst,2 = 5 C
Ps1,1= 0.15 Mpa hst,2 = 50 ki/kg hst,1= 2725 kJ/kg BOILER
P3= 2.1 Mpa P2= 2.1 Mpa T3 = 118 C T2 = 0 C
h3= 840 kI/kg h2 = 290 kJ/kg BUTANE
turbine = 631.8 * m,team kw TURBINE = 623.3 0 msteean kW p W um = 8.5 *
m,testn kw BINE (4__ P4 = 0.105 Mpa P1= 0.105 Mpa T4 = 22 'C T1= 0 'C
h4 = 710 k!/kg h1= 290 kJ/kg CONDENSER
ice-water slurry Tw,2 = 10 'C T.,1= 0 C
X= 25 % ice M= m, kg/s Figure 5: Butane Cogeneration System The condenser exchanges heat between the condensing butane and the ice-water slurry.
Mass flows are calculated with the following heat transfer equations:

9cond = mbut(h4 - h1) = mw[CPw(Tw,2 - T1,1) + xhfg ] (kW) mbut(710 - 290) = th [4.181(10 - 0) + 333x]
mbut = mw(0.1 + 0.79x) The process in which the steam relinquishes energy to the evaporator is described on the water pressure-enthalpy chart in Appendix 3. As seen on the chart and Figure

5, since the fluids used in the boiler and the condenser are the same and have the same heat capacity, the temperature of the plant waste water exiting the boiler can be considerably reduced, exiting the system at temperatures which are not harmful to the marine environment. The equations for the boiler are the following:

gboil = mbut(h3 - h2) = msteam(hsteam,2 - hsteam,i) (kW) mbut(840 - 290) = rhsteam(2725 - 50) mbut = 4.861itsteam The energy consumed by the pump is defined by:

mbut Wpump = (P2 - P1) Pbut 4.86 titsteam (2.1 X 106 - 1.05 X 106) Wpump - 600 1000 Wpump = 8.5 msteam (kW) The energy drawn from the turbine is calculated with the following:
Wturb = mbut (h2 - hi) Wturb = 4.86 msteam(840 - 710) Wturb = 631.8 msteam (kW) The net theoretical power produced by the cogeneration cycle is therefore:
Wcogen = Wturb - Wpump = 623.3 msteam (kW) 4.6 Mass Flows and Total Power Usage The ice-water slurry mass flow corresponding to the flow of steam in this system can be found by placing combining two of equations from the cogeneration cycle, and other mass flows can be written as a function of steam flow:

m,but = rhw(0.1 + 0.79x) = 4.86 msteam 48.6 msteam m"' (1 + 7.9x) m 1 = 0.4 m = 19.4msteam (1 + 7.9x) The power consumption and yields from various components in the system are written as a function of the steam flow:

Wnet = Wcogen - Wtransp - Wcomp-Wdesai - Wp,l - Wp,2 Wcogen, = 623.3 msteam Pransp - Pamb 48.6 tilsteam(Ptransp - Pamb) Wtransp = mw P - p(1 + 7.9x) 48.611steam 998.7x + 62.7) Wcomp = ritw(20.55x + 1.29) = 1 + 7.9x (20.55x + 1.29) = msteam (998 1 + 7.9x 48.6 msteam = 408.24 msteam Wdesai=8.4mu,=8.4 1+7.9x 1+7.9x Combining and rearranging, the desalination, ice creation and cogeneration components are written in relation to each other.

(998.7x + 62.7) 408.24 Wnet = msteam 1623.3- (1 + 7.9x) (1 + 7.9x) - Wtransp - Wpj - Wp,2 998.7x + 470.9 Wnet = msteam [623.3 - 1 + 7.9x , - Wtransp - Wp l - Wp 2 (kW) In a simple, initial analysis of the term in the brackets, which represent net enthalpy excluding pipe transport energy costs as a function of the ice fraction in the flow, it is immediately apparent that the net enthalpy value is always positive for values of x ranging from 0 to 1.

At first glance, increasing the ice fraction in the flow appears to increase the amount of available enthalpy (as shown in the graph below) and stabilize with higher ice fractions. It is important to note that these values do not include losses due to the increased water flow required to carry the equivalent amount of cooling potential in the pipes.
Also, ice fractions ranging between 0 - 0.1 might incur lower cooling and transport costs, but require much greater mass flows and become difficult to use in the cogeneration system if the desired lower turbine outlet pressure is to be maintained.

450!

.2 -300, ro 4 0.1 0.2. 0.3 0.4 0.5. 0.6. 0:7 tce Fraction: x Figure 6: Net Available Enthalpy Excluding Pipe Transport Energy and Other Losses Therefore, the numbers present in this equation depend on many interrelated factors, such as lower condensing temperatures made possible by the use of ice-water as a coolant and geometrical factors. Such an analysis will be made possible in a fully integrated, interactive computer program, which is currently in development.

However, it can be demonstrated that the system not only provides the necessary cooling to existing thermal plants near the shore, but leads to more efficient use of their heat rejection, turning as much heat as possible into electricity and causing less damage to the environment.
Furthermore, this system produces a steady flow of fresh water, an element of which the local supply is dwindling and is becoming of great concern in nearby population centres.

For these reasons, the system remains highly viable for current-day challenges, and a correct balance between the numerous variables can be found in order to obtain conditions with the highest yields and lowest energy costs.

5. Conclusion The system described in this article consists of many different interrelated systems, all of which are designed with three common goals in mind:

1. To develop new techniques which will provide cooling for existing thermal plants located near the ocean shore while respecting strict environmental regulations regarding heat rejection and on-shore construction, and avoiding the expensive task of relocating plants, 2. To generate additional electricity from these power plants, thereby increasing their efficiency and reducing overall dependence on other fuels, 3. To provide large amounts of desalinated water to local population centres, while respecting strict environmental regulations regarding wastewater disposal.

The goals and methodologies regarding this system have been identified.
EH2solar Technologies therefore proposes the following actions for subsequent work:

1. The collection and analysis of a large amount of information regarding costs, permits, regulations, requirements and other political factors which will inherently guide system design for particular areas, 2. The collection and analysis of thermophysical data in the vicinities affected by this system in order to attain optimal yet environmentally sound operating conditions, 3. The completion of a fully integrated, interactive computer program, adapted to reflect existing thermal plant cooling scenarios in order to determine optimal values for operation and construction, 4. The creation of a first complete design for a system which is adapted to an existing power plant and which falls in line with regulations, 5. After verification and modification from local regulatory authorities, final project approval and construction project launch.

References [1] Gilau & Small, "Designing cost-effective seawater reverse osmosis system under optimal energy options", Renewable Energy 33, (2008): 617-630.

[2] Bellas, Tassou & Chaer, "Studies into the thermal and transport properties of ice slurries for low energy cooling applications in buildings", School of Engineering and Design, Brunel University.

[3] Xie & Co. "Study on sea ice desalination technology', Desalination 245 (2009): 146-154.

[4] Haaland, SE. "Simple and Explicit Formulas for the Friction Factor in Turbulent FloW", Journal of Fluids Engineering (ASME) 103 (5), (1983): 89-90.

[5] Hirochi, T., Maeda, Y., Yamada, S., & Shirakashi, M., "Flow Patterns of Ice/Water Slurry in Horizontal Pipes", Transactions of the ASME Journal of Fluids Engineering 126, (2004): 436-441.

Appendix 1: Ammonia Refrigeration Cycle Evolution in Offshore Ice Slurry Creation System 500.
75Q 740 854,k 851 X50 AMMONIA soo 200' R-'~ a5o UePs~~ x204 k9/ii) Y, I f, r It VjY f V1 .~ 04 rz a 10, 4. E

2, +a +n o o' h 4 .i ri vi ro ~' ro ro' O ~O why 0 ~b 1. 5 0 ~

0.4 A:2 4~ m3 01 0 0.3:..
o c ro e' e . o.L
All, "If 114- -7 1 1 i o o M it c V.04 $ IF - m o m < 10 C; I At 0.02 ry n o o ..a: "" ro `0.01 -1200 1000 -800 -600 -400 -200 0 200' 400 600' 800 1000 1200 1400 1600 1800 .
ENTHALPY (kJ/kg) Appendix 2: Butane Rankin Cycle Evolution in Onshore Cogeneration System o o b I~-~. by A Q4~. 3..~ 3.' -IFFLITTITT Pill NORMAL
1a BUTANE y5a R-600 ,oa oN ", 1i .4. o,. qp Kill ~ Qen9it ' ' kQlm .
uJ
T.

a.
(I) o W
I /L1 q Vi Ill 1-4-u ~.

0.1 i 80 V I I 1:,, 1: pa .1 Ill 0.04 N Y o 0 0`0 ;4$
75 14.
0.02 +v v a m Ica-Aar, a N
O =o` d e k o 8 6 o M lrl 0 ` O
d N m' y N' 0.01 0 100 200 300 400 500 600 700 800 500 1000 11100 12.00 1300 1400 1:500 ENTHALPY (kJlkg,) Appendix 3: Waste Steam Evolution in Onshore Cogeneration System .20 WATER

I-ELI

LAM, :2 08 ..

W x.
o 0:2 o v C'7 M .. P b h bi W, k 0 to a 1, o.1 CL
0,04 $ oe 0.02, o w l7:_ ~, . . w 0:03?
o' d k o o - 0..
0.01.

M
u&

0.002 S ~.Ãf 0.001.
0 400 800 1.200, 1600 2000` 2400 2800 3200 X600 4000 4400 4800 ENTH.AL.PY (kJ/kg) Desalinisation Il s'agit d'un proced6 de desalinisation utilisant le principe que la glace ne contient pas de sels mineraux.
En utilisant l'avantage du fait qu'il existe des sources d'eau froide dans 1'oc6an plus nous puisons profondement pour nous approvisionner. Nous alimenterons le condenseur de la thermopompe avec de 1eau la plus froide possible daps le but d'obtenir le coefficient de performance le plus 6leve possible. De cette fagon i1 sera possible d'obtenir un COP elev6 et de produire de la glace ii un cotlt minime. Il sera possible d'obtenir un COP encore meilleur si on d6tend le refrigerant daps turboexpender, un decompresseur de l'inventeur Ralph Morgado US 6739307 B2 May 25, 2004. Lorsque des sources d'eau tres froide en bas de 0'C seront disponible A proximite, it sera possible d'utiliser un circuit ferme contenant de dean avec un degre de salinite inferieur 61'eau de lamer pour obtenir naturellement un melange eau lorsque deau A l'interieur du tuyau atteint une temperature egal ou inferieur it zero. la glace ainsi forme permettra d'obtenir une densite plus basse sur la partie du circuit qui remonte vers 1'installation qui dans ce cas pourra etre install6 sur une plateforme ou sur la terre ferme. Dans le cas ou nous choisirons de produire un melange eau glace sur la plateforme it sera souvent preferable de produire un melange eau salee et glace et de faire la centrifugation de la glace sur la terre ferme.

Optimisation des systemes photovoltaYque Dans le but de diminuer le coot par kilowattheure d'electricite it sera utile d'utiliser un tuyau dans lequel nous faisons passer un melange eau glace ou de l'eau tres froide sur lequel nous installerons sur sa surface inf6rieur des cellules photovoltatques. Puisque le rendement de ces cellules diminue lorsque leur temperature augmente et qu'ils sont capable de dormer un rendement optimum it sera possible de concentrer les rayons it 1'aide de systemes Fresnel longitudinaux. Puisque le coot par metre carre des miroirs plat est beaucoup moins dispendieux que celui des cellules photovoltalques nous obtiendrons de cette facon un rendement sup6rieur A moindre coAt par metre carre.

Cogeneration Par la suite it sera possible d'alimenter le condenseur permettant de condenser le refrigerant sortant de la turbine d'un cycle de cogeneration utilisant un refrigerant qui utilise l'energie latente contenue dans la vapeur qui sort d'une centrale thermique permettant d'obtenir plus de 70%
d'6nergie supplementaire en ameliorant la rendement.

Refrigeration Il sera aussi possible d'utiliser le melange eau glace pour alimenter les plus gros edifices en climatisation.
Location Cette technologie peut s'adapter it plusieurs environnements dependamment des temperatures disponibles, de la distance ii parcourir pour s'approvisionner en eau froide. Dans certains ces it sera preferable d'installer tout l'equipement sur la terre ferme lorsque l'eau froide sera suffisamment proche.

OTEC

II s'agit d'une generatrice utilisant I'energie solaire qui est accumule a la surface de ('ocean jumele aux courants froid siue plus profondement pour produire de I'energie mecanique qui pourra servir a generer de I'electricite ou tout autre travail dependamment du besoin.

Cette generatrice est particulierement performante parce qu'elle utilise la difference de densite entre la phase liquide et gazeuse d'un refrigerant. En effet le refrigerant sortant du condenseur, siue pres de la surface, et qui est lui-meme alimente en eau froide provenant des profondeurs de ('ocean descend a I'etat liquide clans un tuyau et produira une pression a cause de sa densite plus eleve permettant de produire de I'energie mecanique a ('aide de la premiere turbine numero 1 qui abaissera suffisamment la pression pour permettre I'evaporation lors de son passage clans I'evaporateur. La.vapeur se dilatera par la suite clans la turbine numero 2 pour produire encore plus d'energie mecanique.

Ce systeme permet d'obtenir une hausse de pression sans devoir depenser de I'energie mecanique clans un systeme de pompage. Au contraire clans ce systeme si nous laissons descendre le refrigerant sous forme liquide sur une distance suffisamment longue nous obtenons une pression additionnelle permettant de produire une energie mecanique supplementaire.

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A melange eau glace flottant K eau pure froide B eau salle froide environ -2'C L condenseur utilisant I'eau froide pour C centrifugeuse condenser le refrigerant G D evaporateur de la thermopompe M colonne de refrigerant liquicle E: condenseur de la thermopompe N evaporateur utilisant I'eau chaude pour F sortie eau cte mer et saumure chaude evaporer le refrigerant G entree eau de merfroide et prefiltration 0 colonise de refrigerantgazeux H circuit de recirculation d'eau P energie mecanique l : melange eau glace flottant R eau chaude J eau pure froide S : Sortie d`eau pure J

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V
A : melange eau glace ftottant K :eau pure froide B, eau salre froide environ -2'C L condenseur utilisant I'eau froide pour C : centrifugeuse condenser le refrigerant D : evaporateur de la thermopompe M r colonrie de refrigerant Irquide E:. condenseurde ta:thermopompe N eva.porateur utilisant 1eau,chaude pour F: eau tigvide evaporer to refrigerant G: entree eau de,merfrofde et prefiitration 0:colonne d~ refrigerantgazeux H : circuit de recirculation d'eau P : energie mecanique i : melange eau glace flottant R : eau chaude J ea.u pure froide S: Sortie ci`eau pure T: melange eau glace U: sortie eau sallee V: eau plus de 3Km environs -2C
' A: condenseur utilisant eau froide provenant du fcxnd de I'eceari pour refroiclir ie refrigerant B evaparateur utilisant I'ea.u chaude provenant de is surfac.e de- t`e~ceant I et ,2 : turbines procluisant de l'ernergie mecanique 3 pampe servant a faire monter I'eau froide 4 p`oiTi R'e servant a faire descendre I'ea u +chaude 51. e'nergte me,canique,

Claims