Patent Application
20200324247
Increased demand for clean power generation from free renewable energy sources in order to ease the “global greenhouse effect”, led to the development and commercialization of cost effective solar panels and small wind turbines, which could supply free power off grid in needy places on Earth. The application of renewable energy sources for desalination and water treatment should enable low cost potable water supplies to a large fraction of the growing global population (˜7.2 billions) in islands, coastal regions and inland locations of scarce water supplies where local grid doesn't exist or provides expensive electricity. If 25-50-100 liter/day/person potable water consumption are considered low-medium-high standard, respectively, small desalination units of 5, 10, 25, 50, and 100 m3/day capacity operated with free solar/wind power should enable supply of quality water free of contamination to communities of 200-100-50; 400-200-100; 1,000-500-259 and 2,000-1,00-500 residents, respectively. Water consumption takes place mostly during day time and therefore, desalination units operated only by solar power should meet all daily water needs during the 6-8 hours of effective day light; whereas, desalination units operated by wind power are unrestricted to day light and the night production stored for use during the day.
The solar power (PS) availability on Earth surface can be expressed by (1) as defined from the solar constant in space (1.353 kW/m2) and accounting for the fraction of solar radiation lost in the atmosphere (δ) which is approximately 50% in clear sky and more in cases of clouds and/or fog. If the efficiency of DC current production by solar panels is expressed by φ and that of DC→AC power conversion factor expressed by Ω, the AC power made available from solar radiation on Earth can be expressed by (2). Solar radiation on a flat surface area on Earth varies during the day and defined by cos(α); where, α is the angle between the incident radiation and the normal to the flat surface area, and this implies maximum power deposition in midday, low power depositions in the morning and late afternoon, and a confined number daily hours of effective power deposition. Annual solar energy deposition per surface area (kWh/m2/year) in several global regions and their translation to DC energy assuming φ=0.22 (in parenthesis) revealed: 1,000 (200) in central Europe, Asia and Canada; 1,500 (330) in central USA; 1,750 (385) around the Mediterranean; and 2,200 (484) in Equatorial Africa as well as in the desert regions in the Middle east, Australia, Africa and America. The cited figures already take account of large summer/winter seasonal variations with estimated 25% lower values from the average in mid-winter and 25% higher values in mid-summer. Accordingly, a desert region of 484 kWh/m2/year average annual DC energy deposition should experience seasonal variations in the range of 363-605 kWh/m2/year which translate to a daily average range of 0.99→1.66 kWh/m2/day. Assuming an average of 6-8 hours of daily effective solar radiation in desert regions during the winter and summer seasons, respectively, the above cited figures translate to an average of 165→207 Wh/m2 or 13.7→17.2 Ampere-hour/m2 current input to a 12 Volt battery per square meter of a solar panel and this figures per 30 m2 solar panels translate to 29.7→49.8 kWh/day during the winter and summer seasons, respectively.
P
S(kW/m2)=1.353*(1−δ) (1)
P
S(kW/m2)=1.353*(1−δ)*φ*Ω (2)
Wind turbine power (Pw) is expressed by (3); wherein, η stands for a power coefficient of 16/27(59.26%) theoretical maximum, d for air density, R for rotor's radius and v for wind velocity. The wind power equation takes the form of (4) in kW when d=1.2* 10−3 kg/m3, R expressed in meter and v in m/s. It should be pointed out that the power coefficient depends on the tip-speed-ratio (λ) expressed by (4); wherein, u stands for the tip-speed velocity of the rotor and φ for its rotational speed (RPM). Windmill rotors are made by design to operate in the high power coefficient range (0.35-0.45) at the nominal wind velocity frequency which is of band of the highest energy content.
P
W=(½)*η*d*(π*R2)*v3 (3)
P
W(kW)=1.884*10−3*η*R2*v3 (4)
λ=u/v=(2*π*Rφ)/v (4)
Wind regimes can be rated according to their average annual natural wind energy availability per unit area perpendicular to the sweep of the rotor (kWh/m2/year) such as excellent for 3,250±250 (8.90±0.68); very-good for 2,750±250 (7.53±0.68); good for 2,250±250 (6.16±0.68); medium for 1,750±250 (4.79±0.68); and poor under 1,250 (3.42); wherein, the data in parenthesis is that of a daily average (kWh/m2/day). Wind power can be experienced over 24 hours a day with an average power output for the respective cited regimes expressed by 370±28; 313±28; 257±28; 199±28; and 142±28 Wh/m2 which translate to 30.7; 26.1; 21.4; 16.5; and 11.8 ampere-hour/m2 current input to a 12 Volt battery per square rotor sweep. Since wind velocity variations are common and depend on frequencies, effective wind turbines should be able to operate efficiently also above the nominal wind velocity, the frequency of the highest energy content.
The data furnished hereinabove enables a to estimate the continuous accumulation of solar and/or wind energy in a fixed voltage battery according to solar radiation regions and wind regimes, as exemplified next for a typical desert region of a medium wind regime characteristics where maximum solar radiation will charge a 12 volt battery at an average annual rate of 15.4 (13.7→17.2) ampere-hour/m2 comparable to a medium wind regime (16.5) and not far removed from that of a poor wind regime (11.8) with area in the former related solar panels and in the latter to a rotor's sweep—under said conditions the solar and wind variable power sources are expected to provide a total average of 39.9 (15.4±16.5) ampere-hour/m2 or 0.958 kWh/m2/day per one square-meter collection area (CA) each, or 9.50 kWh/day per 10 m2 CA; 19.20 per 20 m2 CA; 28.7 per 30 m2 CA; 38.2 per 40 m2; 49.9 per 50 m2 CA.
The application of solar/wind power for desalination by ordinary direct pass RO techniques of fixed pressurized flow at inlet require batteries of large enough energy storage capacity to enable durable a performance. Alternatively, the application of such energy sources for continuous desalination with a small battery capacity can be made possible if permeates' production proceeds under variable flux as function of power availability. The present invention describes systems for closed circuit desalination under variable flux conditions with renewably solar/wind energy sources of variable power characteristics, intended for water supplies to small communities where a local grid doesn't exist or provide expensive electricity.
The inventive system for water desalination with renewable energy sources describes the integration of a batch close circuit desalination (CCD) unit of NMEn configuration (N modules each of n elements) with solar panels and/or wind turbines of variable power output, through a small capacity buffer battery also equipped with a battery load monitor (BLM) and a DC/AC power conversion means.
The inventive system is made to operate continuously, pending a sufficient power availability from the cited natural energy source, by a programmable logic controller (plc) board in said CCD unit based on operational set-points (flux, module recovery and sequence recovery) which enables a periodic flux correction in response to online BLM signals from the storage battery, such that a declined BLM signal due to output>input is periodically responded through the plc board with a flux decline to affect output≤input in the buffer battery; an increased BLM signal due to output<input responded by a flux increase to affect output≤input, and an unchanged BLM signal not affecting flux. A periodic flux correction through the plc is aimed to enable the buffer battery sustain a certain predefine BLM level (e.g., 50%), accordingly, deviation from said level due to change in power availability is responded through the plc by flux adjustments. The plc board is expected to stop the desalination unit at its lowest designated operational flux below a certain predefined minimum (e.g., 10% BLM) for lack of sufficient power availability, or disconnect the energy collecting lines to the battery at a certain predefined maximum BLM value (e.g, 90%) under maximum predefined operational flux conditions in order to avoid damage to the battery due to overcharge.
In contrast with traditional direct-pass RO techniques, CCD is the only method which enables large flux variations without exceeding manufacturers' specifications of elements and this irrespective of the number of element per module and/or the module recovery and/or the batch sequence recovery. The inventive system operations are illustrated with single-element CCD units for seawater desalination of 43.4% recovery in the flux rang 8-28 in Example 1 and for brackish water desalination of 85% recovery in the flux range 10-37 in Example 2.
According to some embodiments, a system for RO desalination driven by a clean energy harvesting device from a variable power renewable natural energy source through an energy storage means, includes:
RO desalination proceeding in a batch closed circuit desalination (CCD) unit comprising one or more than one module in parallel, each of one or several membrane elements; a closed circuit concentrate recycling line with a circulation means from outlet(s) to inlet(s) of said module(s); a feed line with pressurizing means to inlet(s) of said module(s); a permeate release line off said module(s); and a line off said concentrate recycling line with actuated valve (AV) and check valve (CV) means to enable a brief periodic brine replacement by feed at low pressure after each batch desalination sequence under fixed flow and variable pressure conditions controlled by operational set-points of flux, module recovery and sequence recovery;
an energy harvesting device for conversion of variable power natural energy to DC (ampere-hour) as function power availability;
an energy storage means referring to a fixed voltage battery of a defined maximum (ampere-hour) capacity wherein said DC (ampere-hour) energy is collected as function power availability of said natural energy source and wherefrom energy is transmitted to said CCD unit through a DC/AC converter as function of its operation flux set-point, with said battery also equipped with a battery load monitor (BLM) which also shows of its remaining energy capacity as results of the input-output balance change;
whereby said system is made to operate continuously, pending a sufficient power availability from said natural energy source, by a programmable logic controller (plc) in said CCD unit with operational set-points of flux, module recovery and sequence recovery which also receives online data from said BLM and affects a periodic change of flux with a declined BLM capacity signal due to output>input responded by a declined flux is said CCD unit to enable output<input into said battery and with an increased BLM capacity signal due to output<input responded by an increased flux is said CCD unit to enable output>input into said battery and the intent of said periodic change of flux procedure is to restore BLM capacity at a desired predefined level (e.g., 50%) while said CCD unit operate, as well as to temporarily disconnect the line from said energy harvesting device to said batter when said CCD unit operates in its maximum defined flux range while the BLM capacity exceeds a maximum defined level (e.g., ≤90%) to avoid overcharge damage to said battery, or stop said CCD unit for lack of sufficient power when said CCD unit operates in its minimum defined flux range while the BLM capacity drops below a defined minimum value (e.g., 10%).
According to some embodiments, the pressurizing means (HP-vfd) is a high pressure pump with variable frequency drive means to enable controlled flow rates.
According to some embodiments, the circulation means (CP-vfd) is a flow circulation pump of a low pressure difference with variable frequency drive means to enable controlled flow rates.
According to some embodiments, the actuated valve means (AV) is a two-way valve of an closed/opened positions controlled by said plc with a closed position experienced during said batch desalination sequences and an opened position during said brief periodic brine replacement by feed at low pressure after each batch desalination sequence; and said check valve (CV) means dictate the flow direction in said concentrate recycling line during said brief periodic brine replacement by feed.
According to some embodiments, the energy harvesting device refers to solar panels for solar radiation conversion to DC (ampere-hour) energy as function solar energy availability.
According to some embodiments, the energy harvesting device refers to a wind turbine with a DC generator for wind power conversion to DC (ampere-hour) energy as function of wind power availability.
According to some embodiments, the energy harvesting device refers to solar panels and wind turbines with DC generators together for continuous generation of DC (ampere-hour) energy as from both said sources simultaneously.
According to some embodiments, the feed water to said system may comprise seawater, or brackish water, or contaminated ground and/or surface water depending on the specific design of said system.
The inventive system of the preferred embodiment described hereinafter comprises a batch closed circuit (CCD) unit with power link to natural clean energy sources of variable power characteristics, such as solar panels and/or wind turbines, through a buffer battery of fixed voltage, for continuous production of permeates with a flux rate proportional to the power availability from the natural sources.
The inventive system of the preferred embodiment for continuous CCD with natural clean energy sources of variable power characteristics; wherein, solar panels (SP) used as the sole energy source is described schematically in
The batch CCD unit in the design (
In the integration of the CCD unit with the variable power clean energy source proceeds by a plc link between the flux (μ) and % PLM (φ) with a declined φ affecting a declinedμ and vice versa. The battery should provide a sufficient buffer for periodic adjustments of flux to enable a continuous desalination process. The inventive system is made to operate continuously, pending a sufficient power availability from the cited natural energy source, by a programmable logic controller (plc) of said CCD unit operational set-points (flux, module recovery and sequence recovery) with a periodic flux correction in response to online data of said BLM signals, such that a declined BLM signal due to output>input is periodically responded through the plc board with a flux decline to affect output≤input in the buffer battery; an increased BLM signal due to output<input responded by a flux increase to affect output≤input, and an unchanged BLM signal leaves the flux unchanged. A periodic flux correction through the plc is aimed to enable the buffer battery sustain a certain predefine BLM level (e.g., 50%), accordingly, deviation from said level due to change in power availability is responded through the plc by flux adjustments. The plc board is designed to stop the desalination unit at its lowest designated operational flux below a certain predefined minimum (e.g., 10% BLM) for lack of sufficient power availability, or disconnect the energy delivery lines to the battery at a certain predefined maximum BLM value (e.g, 90%) under maximum predefined operational flux conditions in order to avoid damage to the battery due to overcharge.
The solar energy range made available to the CCD unit will depends on the surface area of (A, m2) the solar panels and both the consumed energy (ΣkWh) and generate volume (Σm3) of permeates per sequence define the specific energy (SE) expressed by SE=(ΣkWh)/(Σm3), which is expected to be low since CCD proceeds with a near absolute energy conversion efficiency without need for energy recovery in the absence of pressurized brine flow release during the process. The battery in this process serves only as a buffer of energy input and output and its energy storage capacity should account for the periodic BLM changes between flux adjustments.
The inventive system of the preferred embodiment for continuous CCD with natural clean energy sources of variable power characteristics; wherein, wind power from a wind-turbine (WT) used as the sole energy source is described schematically in
The inventive system of the preferred embodiment for continuous CCD with natural clean energy sources of variable power characteristics; wherein, such sources comprise of both solar panels (SP) and wind-turbines (WT) is described schematically in
If the components in the CCD unit are powered by DC instead of AC, the need for a DC→DC converter displayed in
Although the inventive system of the preferred embodiment is exemplified below with single-element CCD units for seawater (35,000 ppm) desalination (43.9% recovery and average 16.1 m3/day permeates production) in Example 1 and for brackish water (1,000 ppm) desalination (85% recovery and average of 23.5 m3/day) in Example 2, it should be obvious to the skilled in the art that the inventive system is not confined to a single-element configuration and may comprise larger CCD units of many modules connected in parallel, each one or more than one element, for a much greater production of permeates when linked to solar panels and/or wind turbine(s) of a sufficient energy collection area in compliance with the permeates production requirements. The choice of single-element CCD unit illustrations of the inventive system for desalination with renewable clean energy sources was not a coincident, since intended to show the minimum permeates production capacity made possible by this approach and the incentives created for small communities for its adaptation.
It will be also understood to the skilled in the art that the inventive system of the preferred embodiment and its principle actuation modes described hereinabove on the basis of
While the invention has been described hereinabove in respect to particular embodiments, it will be obvious to those versed in the art that changes and modifications may be made without departing from this invention in its broader aspects, therefore, the appended claims are to encompass within their scope and all the changes and modifications as fall within the true spirit of the invention.
The inventive system for CCD desalination comprising a batch CCD-SWRO unit of the design in
The performance simulation results as function of flux in the exemplified inventive system in
The illustrated inventive system described hereinabove for Ocean water (3.5%) may apply to seawater of different salinity such as Mediterranean water (4.0%) in which case the same average permeates production of 16.1 m3/day will require and increased areas of solar panels and rotor sweep area of a wind turbine of ˜15% in order to accommodate for the extra power needs.
Under the annual solar and wind conditions in the location of the exemplified inventive system, the average annual projected daily permeates production is 16.1 m3/day (grater average during the summer and less during the winter seasons) when operated only by solar panels according to the
The application of the inventive system exemplified hereafter demonstrates the use of solar and/or wind clean energy for potable water supplies from contaminated and/or salty surface and/or ground water sources with a single element batch CCD unit of fixed flow and variable pressure operation with long CCD sequence experienced most of the time and brief stops for brine replacement by feed executed between said sequences.
The inventive system for CCD desalination comprising a batch CCD-BWRO unit of the design in
The inventive system is intended for permeate production of 85% recovery with a fixed module recovery of 10% (1.17 av-pf) under variable flux conditions (10→37 lmh) as function of the power availability of the cited natural energy sources. The consecutive sequential batch CCD simulations assumes pumps efficiency of 70% for both HP-vfd and CP-vfd; 2.0 minute intervals of brine replacement by feed at low pressure (0.5 bar) between CCD sequences; and a periodic (e.g., every 30 min.) flux correction as function of % BLM through the plc board, such that the percent change of the battery load expressed by [BLMmonitored−BLM50%/BLM50%] translates to a relative change of flux from its midrange (23.5 lmh) or from a different desired reference level. A declined BLM signal manifests a lower input than output to the buffer battery and this is corrected by a declined operational flux and vice-versa.
The performance simulation results as function of flux in the exemplified inventive system in
Under the annual solar and wind conditions in the location of the exemplified inventive system, the average annual projected daily permeates production is 23.5 m3/day (grater average expected during the summer and lower during the winter seasons) when operated only by solar panels according to the
| Number | Date | Country | Kind |
|---|---|---|---|
| 254725 | Sep 2017 | IL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IL2018/051032 | 9/13/2018 | WO | 00 |
