Inverse Wind Energy Osmosis

Inverse wind energy osmosis

Introduction.

The panorama regarding water for human consumption is daunting. Almost two million people die a year due to lack of drinking water and it is likely that in 15 years half of the world’s world population in areas where there will be enough water. Our planet contains more than one billion billion liters of water, but little can be taken. More than 97 % of water on Earth is salty and two thirds of fresh water is retained in glaciers and polar ice layers.

On the other hand, population growth and energy needs make an energy saving policy and the search for new sources essential. The development of clean energy is necessary to combat climate change and limit its effects. This project seeks to meet this basic need, providing the most vulnerable neighborhoods in the city of Santa Marta for a 5000 drinking water flow, produced by transforming wind energy to the different types of energy necessary.

The origins of studies about water desalination date back to the 5th century.c. And since then this technology has been perfecting, experiencing a boom during the last decades of the twentieth century. During the Middle Ages, many Arab and Persian alchemists practiced the desalination of sea water using solar energy. The force of the wind has taken advantage of for many centuries. His first and simpler application, for more than 500 years, made by the Egyptians, was the use of sails in navigation.

A process of seawater desalination separates saline sea water into two currents: a current that contains a low concentration of dissolved salts and a concentrated brine current.

Over the years, a variety of desalination technologies has been developed based on thermal distillation, membrane separation, freezing, electrodialysis, etc.

Developing

In 1999, approximately 78% of the global capacity for seawater desalination was formed by Flash distillation plants in multiple stages, while reverse osmosis represented 10% [3]. There are about 21.000 operating desalination plants and most are in the Middle East. The 10 largest desalination plants in the world are presented in riga 1.

There are currently multiple wind farms around the world, without going far, in Colombia is the Jepirachi wind far. Jepírachi is an experimental park, an laboratory to know and learn about clean and renewable energy such as wind, which can be an alternative energy supply for the country in the future. Jepírachi is made up of 15 Nordex N60/250 – 1 wind turbines.3 MW each, for a total of 19.5 MW of installed capacity [5].

Requirements and restrictions.

For the description of the restrictions found for the planning and development of a seawater desalination plant through the use of wind energy, they were divided into restrictions for the use of wind energy and for the purification of seawater. Among the restrictions for the use of wind energy we can find technical restrictions, legal restrictions and environmental restrictions. In 2014, the Congress of the Republic approved Law 1715 of 2014, through which the integration of non -conventional renewable energy into the national energy system is regulated. 

Since the establishment of this law, other decrees and resolutions have emerged to encourage, delimit and regulate the incidents of alternative energies in the country, among these wind. With respect to environmental restrictions, there are visual aspects because the turbines are usually supported by a 40-60 m tower, have three blades and a diameter of 42-48 m, so they suppose an obstruction of the view.

 Similarly, one of the main problems with the installation of wind farms is the impact that causes the fauna of the area, generally, the areas for the establishment of these parks coincide with the areas of steps and habitat of many species of birds of birds, so it is necessary to install an aven alert and deterrence system.

Similarly, for seawater water treatment there are technical, legal, environmental and health restrictions. For the optimization of resources in the initial and operation costs, a plant is required in a geographical area with ease in the collection of seawater. In addition, to prevent saline contamination to other pre -existing polls, we must place the captures at least 50 to 100 meters away near the sea.

Site definition.

After an exhaustive search, it was decided that the plant will be located in the city of Santa Marta, Colombia. It is already well known that in this city when it does not rain, the Piedra and Manzanares rivers run out of water and there is no way for the flow to the inhabitants for the insufficiency in the collection. According to a study by the National Planning Department, Samarios pay the most expensive water in the country. 

The desalination plant and the wind farm will be built in the old lots of Prodeco, near the airport, these properties are infertile for any other type of activity. The land has an area of approximately 32 hectares. As found in literature, a plant with a production 5000 /day needs between 2500-3200, therefore, there is more than space available for wind turbines, offices and others.

Plant capacity.

Research was conducted on the drinking water deficit in Santa Marta to ensure not to produce more than what is needed, it was found that this is 120 l/s which is equivalent to 86.4/day. Then, the average drinking water of an inhabitant in Colombia was investigated. According to the EPM, a person consumes on average 3.8 water per month. The most vulnerable areas of Santa Marta will be supplied to approximately 35700 inhabitants, which requires a minimum flow 135660 m3/month, which is equivalent to 4460 m3/day.

 Use of wind energy

Despite the multiple advantages of wind energy, not everything is what you want. The main disadvantage of this is the inability to control the wind. In Santa Marta, throughout the year, wind speed varies in a range of 1 m/s at 11m/s. However, this range of speeds is not enough information to define in detail the use of wind energy. 

For this reason, an analysis was carried out with registered data of wind speeds throughout 2018 through the Commercial Meteorological Information Service. With this, the speeds were analyzed every hour for a typical day of each month of the year, checking how unstable the wind can be in the territory, being February, March and April the months where the highest records of wind speed speed are presented.

Once this analysis was done, it was possible.m. at 6 p. m. To save the moments in which there is not enough wind for wind energy production is essential to support conventional energies.

Energy generation.

WINTER MODEL: The selection of the correct wind turbine will depend on the capacity of absorption of energy or wind potential that each one has, which is based on the density of power, speed, wind direction and area through which the windis happening. The potential of an area is done annually.

According to the information thrown by the weather station located at the Simón Bolívar airport in the city of Santa Marta at a height of 10 m, the speeds and temperatures are analyzed at every hour for a typical day of each month of the year of the year. The weather station also provides wind direction, within the wide range of wind turbines, one capable of automatically orienting to make the most of the kinetic energy of the wind will be chosen.

3 wind turbine alternatives were chosen depending on the range of wind speeds to which the plant must operate to take advantage of its maximum efficiency, being the options evaluated ENAIR 200, Vestas V112 onshore and Enercon E-33/300. Keep in mind that the wind changes speed with the height by the friction caused by the earth’s surface, the corrected speeds that are based on the height on the real location are calculated. This is modeled by the following equation:

Once all the calculations for the three alternatives were made, the Vestas V112 wind turbine was defined as the best option since it turned out to take advantage of its maximum efficiency in the wind speeds experienced by the city of Santa Marta. This wind turbine has an area of sweeping, the height of its tower is 84 meters and its nominal power is 3 MW. Taking into account that the total area available for the plant is, the number of wind turbines must be 2 leaving an area available for the reverse osmosis plant. 

Generation process: It was decided to use a hybrid wind system as a combination of wind energy technology and electric grid in order to optimally integrate both energy sources. If consumption is superior to the energy supplied, the energy that lacks the public network is taken. In the absence of wind it is possible to use energy exclusively from storage or energy can be taken from the public network. This is shown in the scheme below.

Energy storage can be performed by compressed air in a reversible engine, inertia steering wheel or by hydroelectric pumping, for our case the latter will be used, reversible pumping plants are formed by two vertically separated water deposits vertically and connected to each other. This allows a pump to raise the water from the lower tank to the upper one, where it will remain stored until that energy is required.

Desalination technologies.

In a desalination plant the most important process is the one that eliminates water salts. It is important to choose the method to be used based on the characteristics of the plant, the flow rate to be treated, the characteristics of the water, etc. Among these techniques are multiple stages evaporation, inverse osmosis and multietepas distillation. This project is based on the inverse osmosis technique due to its advantages compared to the others, the process consists in applying external pressure greater than the osmotic between the two solutions to achieve the investment of the process, that is, that there is a circulation of the solutionWith less salts to the solution with more salts.

Physical pre-treatment.

In physical pretreatment, 90-99 % of solids are eliminated before entering the reverse osmosis process, it can be performed by means of filters or membranes. The alternatives for the pre-treatment process are: conventional pre-treatment, ultrafiltration and nanofiltration. Conventional pre-treatment by filters offers good membranes protection and lower cost.

The filters, retain the solids found in the fluid by crossing different layers of material. They can be classified mainly according to their operation in pressurized filters or filters by gravity and can have one, two or three layers of material. A pressurized filter is used, because the severity filter speed is very low.

Heat exchange process.

The temperature directly influences the condition of the permeated liquid, this can affect both osmotic pressure and the permeability of water through the membrane. For each ° C of fluid temperature increase, the permeated flow increases around 3%. In the same way, the passage of salts increases at the same rate as the flow, therefore, by increasing the temperature and maintaining a constant flow, the quality of the permeated decreases. 

This is why the implementation of a heat exchanger was evaluated that allows regulating the contribution temperature to the osmosis system and thus control the efficacy of drinking water production. Among the alternatives presented to regulate this factor are heat and shell heat exchangers and plate heat exchangers. 

It was decided to use a tube and shell exchanger because the plates manages work pressures limited by the possibility of achieving a good pond in the joints, in addition, it presents greater pressure losses, which is a critical factor in our design. Because of this, the heat exchanger will be located after the sand filters and before the high pressure pump.

Inverse osmosis process.

In the osmosis process, molecules and water particles are eliminated in order to purify it by means. The possible membranes configurations are: of a single stage, of multiple stages and closed circuit. The employee osmosis process has a single stage of membranes and only apply pressure at the entrance is required.

Energy recovery system.

The alternatives for the energy recovery system are: a press exchanger and a pelton turbine. The Pelton turbine is responsible for using the hydraulic energy of the rejection flow and converting it into mechanical energy that can be used by the equipment with greater consumption, in this case, by the high pressure pump to reduce the use of electricity. Its cost is much lower than the press exchanger.

Post treatment.

Since the reverse osmosis system has great elimination capacity, the water product of the previous stage is not yet suitable for consumption. For this reason it is necessary to add substances to the water through a remineralization process. The CO2 dosage must be made, if possible, against the countercurrent and in descending flow. 

The water speed in the descending pipe should be not higher 0.07m/s to avoid bubble drag. These systems work with the residual pressure of the exit water from the reverse osmosis. The analysis of remineralization techniques demonstrates that the calcite bed technique has lower CO2 consumption and lower process complexity.

Brine spill

Among the options found for the rejection of the brine are the rejection of brine to the sea, reuse of brine spills in shrimp cultivation processes and sale of brine to plants of agri -food process [20] [20]. Contrasting the advantages and disadvantages of each of the methods, it was concluded that the best option is reuse in shrimp cultivation processes in controlled environment ponds. In Colombia, camoniculture is part of a development project that has always sought to implement new techniques that ensure the positioning of the sector in demanding markets.

 Control system

In an osmosis plant, as in any other, there are certain variables that are needed to continue monitoring, among these stand out: flow, temperature, pressure and electricity consumption, these will be monitored as explained below.

• · A flowmeter at the entrance and exit of each equipment.
• · A general accountant of the energy consumption of the installation to identify when it is necessary to use the alternate energy sources to the wind turbines.
• · Thermocouples to control the temperature at the entrance of the reverse osmosis membranes.
• · Manometers at the entrance and exit of each stage of filtration and in the membranes to determine the loss of load in each equipment and proceed to its cleaning if necessary.
• · Signals for opening and closing valves.
• · Level switch on deposits.
• · Low prisoner in the aspiration of the pumps.
• · Alarms: Level alarm in deposits, vacuum alarm in the aspiration of the pumps, temperature alarms.

However, because Santa Marta’s sea water is at the optimal temperature for the osmosis process, it should be carefully evaluated if the increase in efficiency compensates for the costs of implementing a heat exchanger. The ASPEN Exchange Design & Rating Software was used to perform the calculations, in this the mass flow of hot water mustDesired hot fluid, the results of thermal and geometric characteristics are summarized below.

 Flow machines and pipe systems

For our flow of 0.57 m3/s The tower will be 10 m deep;Within the tower you will find the submersible pump of capture in which the seawater collection pipe will be connected, it was decided to use high density polyethylene Pehd-100. Similarly, a water storage tank height was defined approximately 3 meters above sea level.

At the beginning of the pretreatment process is a low pressure pump, the water that will be driven comes from the storage tank and is directed towards the sand and coal filters first through chemical pretreatment, as illustrated in the path in the path. Pressure entrance to sand and coal filters is between 0.35 and 8 bars. An input pressure is then needed to the 4.5 bars sand and coal filters. Pressure losses in physical pretreatment are 0.35 bars, therefore, the input pressure to the high pressure pump is 4,165 bars.

Due to the high pressures needed to overcome the permeated pressure in the osmosis, the pipe material was needed to a more resistant pipe and that had similar qualities. AISI316L stainless steel is ideal for extreme working conditions and in turn widely used in desalination plants worldwide.

As the fluid after the osmosis has a high pressure, since in the osmosis process there was only a pressure drop of 1 bar, a pump is not needed to carry the water by the post treatment and then to the storage tank forIts subsequent supply. Therefore, an AISI316L SCH80 Nominal diameter of 8in will be selected. To recover this energy a pelton turbine is installed. It was considered a storage tank for the flow permeated at a height of 4m above sea level and a 15M pipe.

For the calculation of the pipes, the economic diameter was calculated and calculated, having the sum of the operating and capital costs of the pipe, by meansVEOLIA WATER SOLUTS & TECHNOLOGIES WITH QMAX = 141.4M3/D AND QMIN = 70.7M3/D. After several iterations, it is found that the appropriate filter number is 6, since in case one or two filters are out of operation, the system can follow .

conclusion

The main membranes manufacturers for desalination are Filmtec, Hydranautics, Desco and Toray. Filmtec has a wide range of membranes that meets the requirements. The manufacturer’s membrane type that meets the requirements is SW30xle-400i and the selected pressure tubes are the 80E100 of the Codeline company.

For the calculation of the cost of wind KWH, they were calculated and estimated through literature, economic variables and direct costs linked to the project. By meanspercentage is due to the high investment cost in wind turbines which have a cost of $ 3.261.$ 922.47 each approximately.

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