APPARATUS FOR INDEPENDENT INSTANT PRODUCTION OF FRESHWATER FROM DESALINATION OF SEAWATER ABOARD SEAFARING CRAFT

Technical Field

The invention refers to the technical field of seawater desalination apparatuses, in particular a device for independent, instant production of freshwater aboard seafaring craft.

Large craft (e.g. ferries, cruise ships, fishing vessels) are equipped with reverse osmosis desalination plants, to avoid installing bulky and heavy water storage tanks. Such apparatuses provide for instant freshwater production and are commonly powered by onboard units driven by the craft's propulsion engine. Background Art

Recently, the growing diffusion of pleasure craft has generated an interest in devising desalination devices for smaller vessels, where comfort features— including freshwater availability— are highly prized. However, these plants must be such as to avoid penalizing craft performances, which are also at a premium.

Currently, boats 12-15 m long are generally equipped with reverse osmosis desalination plants powered by an electricity generator. These plants have become highly valued features also onboard smaller vessels.

In fact, an onboard desalination plant provides for instant water production, obviating the need for calling at ports as well as for installing bulky water storage tanks. It also frees valuable space that can be used for other purposes, while avoiding penalizing craft performances compared with similar craft not installing onboard desalination plants.

However, fitting small craft with desalination apparatuses constructed with technology developed for larger vessels involves at least two types of problems. One is that the electricity generator is frequently a source of noise, which in smaller vessels is more intense, thus becoming irritating and fatiguing.

The other is that plant size must be minimal and the device pared down to the essential, to avoid excessive weight. However, such limitation may involve limited, or even insufficient, freshwater production, hence navigation comfort, failing to meet the requirements of medium/long navigation.

Disclosure of the Invention

The aim of the disclosed invention is to overcome such problems by providing a desalination apparatus endowed with a surprisingly high energy efficiency and such as to allow its use also, but not exclusively, aboard small craft.

In line with the invention this aim is achieved by an apparatus having technical characteristics that will be apparent from the appended claims. Brief Description of the Drawings

The advantages of the invention will be clearer from the detailed description that follows, made with reference to attached diagrams, of an embodiment that is reported purely by way of example and is not intended to limit the invention, wherein:

· figure 1 is a block diagram of an apparatus in line with the invention;

• figure 2 is a table reporting the freshwater production capacity per hour provided by the apparatus in relation to the temperature of inlet seawater

Detailed Description of the Preferred Embodiments of the Invention

In figure 1 of the attached diagrams 1 indicates overall an apparatus for independent instant production, aboard seafaring craft 2, of freshwater 3 by desalination of seawater 4.

The apparatus 1 essentially comprises a cogenerator 5 and a desalination unit 9 combined together.

The cogenerator 5 includes a Stirling engine 7, preferably but not necessarily also devoted to the propulsion of the vessel 2, and an electricity generator 10 that is associated with the Stirling engine 7 in such a manner as to receive mechanical energy and be driven by it.

The desalination unit 9 is of the reverse osmosis type and is operatively associated with the Stirling engine 7 in such a way as to receive its exhaust heat 8 and to preheat with it, within a suitable exchanger 11, the seawater 4 drawn from the sea. This, after coursing through a pretreatment section 12 (filtration, bacterial decontamination), enters the desalination unit 9, where is its desalinated according to a known process and then exits as freshwater 3, ready for use.

A pump 13, driven by the electrical energy 6 produced by the generator 10, provides for continuous seawater 4 flow through the desalination unit 9, until its transformation into freshwater 3.

Means to accumulate the electrical energy 14 produced by the generator 10 are envisaged, to store any / the surplus electrical energy 6 left after the requirements of the pump 13 and of the auxiliary organs of the desalination unit 9 have been met.

The type of craft 2 can be indifferently motor or sailing. In either case, operation of the desalination unit 9 during use of the vessel 2 is extremely quiet and comfortable.

In addition, the operative combination of the Stirling engine 7 and the reverse osmosis desalination unit 9 is highly synergistic also in terms of energy efficiency and of the ability to produce freshwater 3.

In fact use of the Stirling engine 7 exhaust heat 8 - which would otherwise be dissipated - to heat the seawater 4 entering the plant reduces its viscosity, improving the production capacity of the apparatus 1, the amount of energy employed for the desalination proper being equal.

This is clearly demonstrated by the data reported in the table of figure 2, showing the freshwater production capacity (expressed as litres/hour) that can be obtained as a function of inlet temperature.

The choice of a Stirling engine 7 makes it possible not only to overcome the noise problem, a strongly felt issue among sailing ship enthusiasts, but also to achieve an exceptionally high freshwater production capacity per hour.

This is explained by the fact that a 1 kWe Stirling engine coupled to a conventional evaporation unit produces about 140 1/day of freshwater, meeting the requirements of a 10-12 m vessel with four passengers.

However, the same Stirling engine coupled to a reverse osmosis desalination unit 9, as in the new and original design of the disclosed invention, results in an increase in daily freshwater 3 production by nearly an order of magnitude, with an electricity consumption that is comparable to that of a conventional apparatus.

The disclosed invention fully achieves the objects of providing large amounts of freshwater by means of an apparatus whose energy efficiency allows a small, compact and light device that is especially suited for small vessels, since it does not penalize their intrinsic performances. The apparatus is also characterized by nearly noiseless operation, which is a positive feature aboard pleasure craft in general, but is highly appreciated aboard sailing boats.

The disclosed invention is clearly appropriate for industrial application. It can also be modified to make variants that will all be encompassed in the concept of the invention; in addition, all elements can be replaced by technically equivalent elements.