TechNet-21 - Forum

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  1. Larry Schlussler
  2. Cold chain equipment
  3. Tuesday, 11 January 2011

In solar powered vaccine storage systems high quality wet cell batteries have the potential of lasting longer than sealed batteries. However, they periodically need the addition of distilled water. Distilled water can be hard to obtain in remote areas.

Sun Frost has developed a method using waste heat from the condenser or compressor to distill small quantities of water needed to make up for water loss in batteries.

If there is sufficient interest and support we could develop the concept into a commercial product.

If interested please contact Sun Frost.

Larry Schlussler Accepted Answer
If a wet cell battery is not filled with distilled water, its life will be substantially reduced. In developing countries, it is often difficult to obtain distilled water. We recently investigated a number of methods distilling the small quantity of water needed for batteries. These included solar and fuel-based systems, as well as using waste heat from the condenser on our refrigerators. We eliminated using waste heat from the refrigerator’s cooling system because of the cost of modifying the refrigerator and the low rate of production. Solar Distillation The equipment needed for both the solar and fuel based methods is essentially the same, see Figure 1 below. For the solar application, we used a large diameter, relatively shallow pot with a glass cover. The cover was inverted so water condensed on the inside of the cover, ran toward the center of the pot and dripped down into a small cup. Water was added on top of the inverted lid to lower the temperature of the condensing surface and increase the efficiency of the still. The still will produce about 8 oz (200ml) per day. The walls of the pot were insulated to reduce heat loss. When using a 12 inch (30 cm) diameter pot, a typical sunny day in the tropics will produce about 6 ounces (180 mL) of distilled water. The pot was filled with about 18 ounces (530 mL) of water. Enough water should be added to the pot to cover daily production and keep the entire bottom covered with water all day. If too much water is added, it will take longer to heat up and the cup may float to the side. http://www.technet21.org/components/com_agora/img/members/3149/mini_Figure-1.png Figure 1: Configuration for either solar or fuel based distillation. The pot cover would be glass for solar distillation. If a glass covered pot is not available, a simple solar still can be made by placing a black open-topped can inside of a jar as seen in Figure 2. The can is filled with water. Water then evaporates and condenses inside the jar. The lid of the jar should be lightly insulated to prevent water from condensing on the lid and dripping into the open topped can. Sitting this jar on a reflector will increase distillation capacity. With a reflector, about 1 ounce (30 mL) could be produced per day. Production per day will decrease as the can empties. The can should be refilled when it is half empty. http://www.technet21.org/components/com_agora/img/members/3149/mini_Figure-2.png Figure 2: Simple Solar Still Fuel Distillation A pot could also be used as a still for a fuel-based system, however the lid of the pot need not be glass. The lid would be inverted and filled with water as with the solar application. Filling the lid more than doubles the efficiency of distillation. Using wood as a heat source, about 0.5 kg of wood will produce about 0.5 L of distilled water. If a load shedding charge controller was incorporated into a solar power system, excess electricity could be used to power an electrical hot plate. About 0.5 kWh would be required to distill 0.5 L of water. Production with a fuel-based system could be as high as 0.5 L per hour. Perhaps the simplest method of distillation is using a conventional pot with an inverted lid. The lid need not be glass. Any fuel could be used to heat the pot and enough water to fill a battery could probably be generated in less than one hour. For the batteries of a vaccine storage system, the water consumption can be quite variable depending primarily on the voltage setting. However, it will almost always be less than 0.5 L per month.
  1. more than a month ago
  2. Cold chain equipment
  3. # 1
James Cheyne Accepted Answer
Has anyone developed a locally manufactured solar water still? This should be pretty easy. A plastic tray about one metre square covered with a dome or peaked transparent cover that has channels round inside at the base where it fits the tray. This channel would collect the water that was distilled on the inside surface of the cover. If the tray and its cover were placed at the slight angle the distilled water could run into a locally procured plastic bottle (previous rinsed with distilled water, of course). Just a thought.
  1. more than a month ago
  2. Cold chain equipment
  3. # 2
Alejo Bejemino Accepted Answer
Water in the distiller could help cool both the refrigerant compressor and the air cooled condenser. Based on what I have observed the refrigerant compressor for solar powered vaccine refrigerator runs at long time at start up but once it reach the cut off point temperature as set by the thermostat, it then runs at short intervals to maintain the correct vaccine storage temperature. I wonder if the heat generated by the compressor and condenser is sufficient to produce distilled water for the battery. For health facility with limited staff it is better that distilled water be delivered from the central level at certain period as the wet cell solar batteries do not need distilled water more often This could be arranged during collection and delivery of vaccines from the vaccine storage facility. Solar powered vaccine refrigerator with no battery and charge regulator could be one of the best option.
  1. more than a month ago
  2. Cold chain equipment
  3. # 3
Larry Schlussler Accepted Answer
Most of our vaccine storage refrigerators are at locations far from a garage and no distilled water would be readily available.
  1. more than a month ago
  2. Cold chain equipment
  3. # 4
prabirkc Accepted Answer
If car batteries need distilled water it will be available at the nearest garage. The problem will occur if the approach to the site does not involve a motor car.
  1. more than a month ago
  2. Cold chain equipment
  3. # 5
Larry Schlussler Accepted Answer
Dear TechNet21, Initially we could incorporate the distiller into the Sun Frost RFVB. This would be fairly easy given the design of the condenser. As you mentioned, it would be much easier to implement on new refrigerators, for both technical and logistical reasons. How much water do you estimate you need per month We will be testing out unit for capacity next week. Larry SchlusslerSun Frost PO Box 1101Arcata, CA 95581 phone (707) 822-9095 fax (707) 822-6213 larry@sunfrost.com http://www.sunfrost.com
  1. more than a month ago
  2. Cold chain equipment
  3. # 6
Toryalai Hart Accepted Answer
If it was integrated with a battery bank and marketed as such (would need different size options), and came with a semi-universal fitting kit for commonly used smaller solar refrigeration units typically installed at PHC's, would solve both the distilled water availability issue as well as the maintenance requirement on behalf of operators. Could start as part and parcel of an integrated kit for the SunFrost RFVB and then be adapted on request. If programs were more thoroughly designed, and maintenance was undertaken by roaming technicians rather than site operators, manual top up of batteries would likely not be such an issue -- and simply producing distilled water on site would be productive. Unfortunately, implementing agency attention and donor funding beyond the initial procurement for programmatic support is rare. The tendency is to hand over management of equipment to beneficiaries rather than include a third party service agreement for maintenance/repair in the initial procurement/installation package, or at the very least cost in a third party roaming technician/supervisor to backstop in country staff. This of course pertains to many more project implementation scenarios than Solar Vaccine Refrigeration, and is unlikely to change anytime soon.
  1. more than a month ago
  2. Cold chain equipment
  3. # 7
Michel Zaffran Accepted Answer
I am hoping that future solution will emerge, indeed. However I am also stressing the fact that what we consider "simple" solutions are often not that simple to implement simply because the motivation does not really exist to maintain the batteries properly. So i doubt there will be motivation to 1) produce the distilled water and 2) maintain the batteries. So this is more of a comment from a managerial perspective rather than from a technical feasibility perspective
  1. more than a month ago
  2. Cold chain equipment
  3. # 8
Larry Schlussler Accepted Answer
It’s fairly simple to make the distilled water on our Sun Frost RFVB-134a; a tube on the refrigerator is filled to the appropriate height, than the distilled water drips into a jar. Even if sealed batteries are initially supplied, they could be replaced by locally available wet cells. Terry’s post noted that on a project he worked on 75% of sites did not have distilled water. Michel seems to be thinking of futuristic solutions. I’m speaking of a device that could be readily implemented now.
  1. more than a month ago
  2. Cold chain equipment
  3. # 9
Michel Zaffran Accepted Answer
I am somehow skeptical. Clearly the use of waste heat to produce distilled water would be a great innovative approach. However i doubt that, in the areas where there is no distilled water, people would actually spend the time required to produce this distilled water they need. I believe that we must strive for simpler, maintenance free (to the extent possible) systems which do not put additional burden on already overworked health workers rather than expect good maintenance , distilled water production, etc.. in places where we are unlikely to find technical expertise Battery free solar refrigerators are one approach. They still need improvement though There may be other ways to simplify the systems for the users : grid connection whenever possible and others we have not started to think of yet.... sorry to have been a bit negative
  1. more than a month ago
  2. Cold chain equipment
  3. # 10
Larry Schlussler Accepted Answer

Distilled Water from Cooling Systems Waste Heat

Thanks for your feedback. We finalized our design for producing distilled water from condenser waste heat on our Sun Frost RFVB-134a. You could also use waste heat from the compressor to distill the water. This would not affect the compressors life or the efficiency of the compressor. The design details would depend on the space available above the compressor. Which brand of refrigerator are you using and how much space do you have on top of the compressor? You mentioned that the water contained sediment, could the water be filtered before putting it into the distiller? You could probably use a piece of material as a filter if something more sophisticated is not available. Putting unfiltered water into the distiller would be OK expect it would have to be periodically washed out. Larry Schlussler PhD.
  1. more than a month ago
  2. Cold chain equipment
  3. # 11
Toryalai Hart Accepted Answer
That would be amazing. A recent assessment of a project revealed that over 75% of sites did not have distilled water available for battery maintenance. Likely that this would also help to keep compressors clean, which is another issue. Do you think that active waste heat recovery could contribute to lengthening compressor life? Would you foresee any effect, positive or negative on refrigerator/freezer power consumption? Water at sites is usually from wells (not always boreholes) and full of sediment - any limitations/constraints there? Would the retrofit be universal or only for SunFrost systems?
  1. more than a month ago
  2. Cold chain equipment
  3. # 12


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