WO2011032978A1

WO2011032978A1 - Water extraction unit

Info

Publication number: WO2011032978A1
Application number: PCT/EP2010/063537
Authority: WO
Inventors: Kjartan Kramer; Adel Farouk Ali El-Mowafi; Ola Barkved; Tor Kristian Eskeland
Original assignee: Aquasolair As
Priority date: 2009-09-15
Filing date: 2010-09-15
Publication date: 2011-03-24
Also published as: NO20093003A1

Abstract

This invention relates to a unit for extracting water from air, comprising an air inlet comprising a first section leading the air in an at least partially downward direction to a second section containing a chosen volume of air and a third section leading the air out of the second section in an at least partially upward direction to an air outlet, the first section including a cooling device adapted to condensate humidity in the air and the third section including a heating device, the air thus being moved through the unit by the resulting differential air temperature and density through the system, and the water being extracted by condensation in the first section, and wherein the cooling device is operated by a solar heat collector.

Description

WATER EXTRACTION UNIT

The present invention relates to a unit for extracting water from the surrounding air, without external power infrastructure needed, as the unit operates on energy from the sun (mainly solar heat).

Providing clean water is a problem in large parts of the world, especially in areas with a warm and dry climate. In these areas solar heat is abundant and normally the warm air carries quite a large amount of water - thus it is possible to extract this water. However the areas where such a device is needed often lack the infrastructure for supplying the required energy necessary for driving the water extraction process- as is required by US7000410, US6336957 and US7373787 where the latter describes a solution that uses a portable generator or solar charged batteries. In US2008/178617 and CH 606644 systems are described that partially use solar energy in a water or ammonia cooling system. Both describe complex systems requiring external power sources and are not easily transported to areas without or with limited infrastructure. Thus there is a need for a unit being able to extract the water from humid air without the need for power supplies or large and heavy external equipment. This has been tried several times, such as the solution shown in US58462396, but without providing a solution that works in practice.

A solution described in US7293420 uses gravity for providing a continuous air flow through the device using a TEC or Peltier element having a cooling side and a heater side where the weight difference between cool and hot air gives rise to the air movement down into and out of the unit. The TEC/Peltier elements are, however, power demanding and thus external power supply.

The object of the invention is to provide a system that enables production of drinking water from the surrounding air by utilizing solar heat as the main driving force in a simple and transportable system. This is obtained as characterized in the accompanying claims. With the present invention a portable water extracting unit is obtained with low or preferably no power consumption thus being able to produce water in any environment, also far from external power supplies. This is obtained using a solar heat driven cooling device, e.g. a thermal refrigeration device or heat pump such as described in eg.

WO2005/066555 and WO2008/046120 and also by allowing the density (weight) difference between the warm and cold air drive the air circulation through the system so as to avoid the use of fans etc.

Thus an essentially passive solution is provided for airflow based on differential density through the system.

The invention will be described more in detail below with reference to the

accompanying drawing, where figure 1 illustrates the preferred embodiment of the invention.

As is illustrated in figure 1 the invention is constitute by a first section 1 including a cooling device 4. The cooling device 4 increases the density of the air and gives condensation, and both move down into the second section 2 which includes a water collection chamber. The cool air replaces the air already present in the chamber which is not as cold and is driven up to the third section 3 and out into the environment. In order to improve the efficiency of the unit the third section may be provided with a heating device 5 to heat the air in side the third section 3 and thus the air circulation through the unit.

Preferably the cooling device is a solar driven refrigeration machine 6 of one of the types mentioned in relation to WO2005/066555 and WO2008/046120 or similar coupled to the cooling device 4 as well as a solar heat collector 7,8 including a solar heat collector 7 and a heat storage 8,. The solar heat collector is preferably liquid/water based, but electrical units may also be considered. More in detail the main pieces of equipment according to the preferred embodiment of the invention is as follows;

1. Solar heat collectors (flat panel or vacuum pipe) 7

2. Heat storage (hot water buffer tank) 8

3. Ammonia absorption refrigeration system (designed for "low" temperatures

<100°C) 6

4. Air-flow unit 1 ,2,3 with water collection system - cooling/ condensation 4 and heating 5.

5. Water cleaning system to ensure clean and safe drinking water (not shown) The air circulation unit should circulate air without motor driven fans etc. - ie utilizing temperature differences and thus density differentials of the air, as the driving force, and possibly additional wind assisted air-flow. To prove the principle of air circulation and condensation of water without motor driven fans a test rig has been designed. The test rig design also enables extension of the rig with both refrigeration equipment and solar heat collectors to develop the system into a fully operational test rig to demonstrate all aspects of the system.

The test rig is used to demonstrate the air-flow and moisture condensation principle in real life, and develop design criteria for the final design. Later on the test rig will be further developed into a fully operational rig to generate design criteria for all systems working together.

The test rig was designed to investigate the real dimensioning criteria for a water machine where the main driving force for air-flow is temperature differences/ density differentials. The final machine will run on a solar heat driven refrigeration machine preferably of the "ammonia absorption" type - but the testrig has been operated with cold tap water as the chiller media, and hot water from an electrically heated tank as the heater medium.

The test rig consists of the following parts/ sections.

Air inlet 1 with simple bag filter for initial cleaning of the circulating air; to avoid contamination of the water reservoir with pollen, insects, etc. For the initial testing the bag-filter part of the inlet was omitted, running without any cleaning device before condensation. Further testing is needed to optimize inlet conditions.

Chiller 4 water/ air heat exchanger for cooling of the inlet air; fincoil type copper pipes with epoxy coated aluminum fins. Cold water from any source may be circulated to provide the chilling effect or possibly an integrated thermal chiller may be provided in the final design. During the test this chiller was operated on cold tap water to simplify setup. Water temperatures was around 7 °C - which is a bit higher than the final refrigeration equipment will be designed for -; this leads to somewhat lower water production capacity especially at the lower temperatures and humidities.

Water collection chamber 2 when cold water circulates in the chiller, the air in contact with the fins will be chilled - and when temperature gets lower than the current dew point of the air, condensation will occur. At the same time air density will increase during cooling - i.e. air gets heavier - and sink trough the heat exchanger 4 into the condensation chamber where the water will be collected. Air chilling will be operated downwards (by gravity) whereas heating will be operated upwards. The heating of the air will decrease density to make the air flow upwards trough the heater 5. These three effects (cooling, condensation, heating) in collaboration will generate the required air circulation - with the addition of potential wind assist if surrounding conditions admit.. Heater 5 water/ air heat exchanger to heat the air. Heated air gets less dens and thus will rise up trough the heat exchanger. In a fully operational machine this heat will be drawn from the "back cooling" side of the refrigeration machine 6, however in the test rig this heat (hot water) was generated in an electrically heated tank, and supplied to the heat exchanger by a 12 Volt mag-drive circulation pump that could potentially be operated by a solar panel system (PV elements).

The air outlet 3 is constructed as a square-to-circular transition piece and an insulated piece of duct to enhance the rising force of the air trough the water collector. However, for the initial testing the ducting part of the outlet was omitted for practical reasons. Further testing will be needed to optimize outlet design. The initial test of the rig was a one week set-up in a greenhouse to optimize airflow conditions, and get some data for later design criteria. Water collection was done once a day - and measured by volume. Airflow was measured trough secondary measures as measurement of very low velocities (below 0,25m/s) is difficult. No instrument was applied to measure this factor directly.

Measurement of temperature before and after the heat exchanger and the heat effect delivered to the air in the heat exchanger will give an indication of the approximate airflow trough the heat exchanger. In addition the water collection from the machine will also give input to reverse calculations of airflow and heat-exchange - and thus airflow. Back calculation of heat delivered to the heat exchanger was done by timing the on/ off function (thermostat) of the electric heater (stop watch and a light bulb in parallel with the heater). Temperature and humidity of the surrounding air was done by a thermometer and a hair-hygrometer, as well as heat-couples for the various temperatures.

The measurements from the initial testing indicates an air circulation/ front velocity on the heat exchanger inlet of approx 0,2 m/s, which under normal circumstances will be sufficient to generate enough drinking water for a family from a machine of the POP1 size. These results where derived from both water collection capacity and heat capacity measurements in combination with reverse capacity calculations.

l AlrWell Test No Results

Table 1.

Capacity calculations

Test results from the test rig indicate front air velocity at the heat exchanger inlet of approx 0,2 m/s (based on heat exchanger cross section) under the current conditions. Further optimization of air velocities - and possibly wind assisted air flow - has the potential to increase airflow, and thus water production. However, for the initial design and capacity estimates the 0,2 m/s front air velocity trough the heat exchangers has been used in the calculations below. Two capacity estimates has been generated; one with the test conditions on the cold side (i.e. 7,6 grdC condenser temperature), and one with slightly lower condenser temperatures (4-5 grdC) to emulate real temperatures a fully operational rig. The slightly lower condenser temperatures will generate more water especially at the lower temperatures and humidities.

Capacity will vary with chiller temperature at the cold side - condensor in the water machine - especially at lower ambient temperatures. The test rig was operated with circulating water temperatures of 7,5- 8 grdC, which gave an air temperature after the chiller battery of approx 9,5 - 10 grdC. This choice of temperature was regarded as conservative as the known solar heat powered chillers are capable of producing colder water.

With the abovementioned solar heat powered chiller installed lower temperatures for the water machine - in the area of 3 - 4 grdC can be expected. This will give higher capacities especially in the lower ambient temperatures. Max capacity however will not be effected by the minimum chiller temperatures - as this will be given by maximum chiller capacity; in our case in the area of 2,5 kW.

Capacity overview POP1

Capacity in liter water pr day

Table 2 - Estimated capacities from the POP 1 test rig. The measured air velocity of 0,2 m/s has been utilized in the calculations

To summarize the invention thus relates to a unit for extracting water from air, comprising an air inlet comprising a first section 1 leading the air in an at least partially downward direction to a second section 2 containing a chosen volume of air and a third section 3 leading the air out of the second section in an at least partially upward direction to an air outlet. The first section included a cooling device 4 adapted to coole the air sufficiently to obtain condensation and the third section including a heating device5 . The air is thus being moved through the unit by the resulting differential air temperature and density through the system as the cold air and condensation will move downward and the heated air will move upward and give circulation through the system and supply new humid air into the system. The cooling device is operated by a solar heat collector 6,7,8 providing a chilling effect. The heating device is also preferably powered by a heat collector. This may be obtained in many ways such as having a dark colour being positioned in the sun but according to the preferred embodiment of the invention both the cooling device and the heating device is power by a refrigeration machine as discussed in relation to the

abovementioned patent applications WO2005/066555 and WO2008/046120 thus being power by the solar heat collector. The heating device is coupled to the back cooling of the same refrigeration machine, so that both outputs of the cooler is utilized. In order to ensure operation also after sundown the solar heat collector may also include heat storage means such as a hot water tank. For extracting the produced water a tap may be included.

Claims

C l a i m s

1. Unit for extracting water from air, comprising an air inlet comprising a first section leading the air in an at least partially downward direction to a second section containing a chosen volume of air and a third section leading the air out of the second section in an at least partially upward direction to an air outlet, the first section including a cooling device adapted to condensate humidity in the air and the third section including a heating device, the air thus being moved through the unit by the resulting differential air temperature and density through the system, and the water being extracted by condensation in the first section, and wherein the cooling device is operated by a solar heat collector.

2. Unit according to claim 1, wherein the heating device is also operated by a solar heat collector.

3. Unit according to claim 2 wherein cooling device is coupled to a refrigeration machine power by the solar heat collector and the heating device is coupled to the back cooling of the same refrigeration machine, thus utilizing both the cooling effect and heating effect from the machine.

4. Unit according to claim 1, wherein the second section includes a pipe and/or tap for letting the water out.

5. Unit according to claim 1, also comprising means for storing heat collected from the environment.