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DESIGN OF A LOW COST ABSORPTION REFRIGERATOR ENERGY ACCESS | LPG CYLINDER PRIZE WINNING SOLUTION (3/7)
SEPTEMBER 2017
ABOUT IDEAS TO IMPACT Ideas to Impact is an action-research programme designing, implementing and testing innovation prizes, to induce innovative solutions to development challenges in Climate Change Adaptation, Energy Access and WASH. A five year, £10.9m programme, funded by the Department for International Development (Dfid) that supports research and development in climate change, energy and WASH through a variety of innovation prizes. The prizes are designed to stimulate and incentivise development of technologies for low income consumers that will improve poor people’s access to affordable clean energy, safe drinking water and resilience to climate change.
ABOUT THE ENERGY ACCESS: LPG CYLINDER PRIZE As part of the Ideas to Impact the Energy Access: LPG Cylinder Prize launched on July 7, 2015, focused on inducing innovations for recycling liquid petroleum gas (LPG) cylinders across sub- Saharan Africa. Applications were received from more than 180 solvers, from over 40 countries, proposing solutions to address the problem of how to maximise the value of large numbers of aging and unsafe LPG cylinders that might need to be retired in the event of market reforms. No readily available solution which could be implemented at scale was identified. However, seven winners were selected, who offered solutions which in the view of the judges had potential to address the challenge subject to further research and development. Here we share one of these winning solutions.
ACKNOWLEDGEMENTS The Energy Access prize is led by Simon Collings at Energy 4 Impact, and collaboratively designed with Jonathan Slater from The Blue Globe. Ideas to Impact is managed by IMC Worldwide Ltd. With special thanks to the independent panel of judges who judged the winning solution.
8 LPG CYLINDER PRIZE - EVALUATION REPORT SUMMARY
Novel uses for removed gas cylinders: Design of a low cost absorption refrigerator
The need for low cost absorption refrigerators in Sub-Saharan Africa countries Fifty percent of Africa is rural with no access to electricity. Africa generates 47 GW of electricity, less than 0.6% of the global market share. Many Sub-Saharan countries are affected by power shortages [1].
The lack of electricity or its low reliability impedes the conservation of food for long periods, thus fresh or perishable food like fruits, meat, fish or many vegetables need to be eaten immediately, or it will go to waste, or cause serious risks for human health. The main problem is stated very clear but its consequences are huger. The Rockefeller Foundation analysed in a 2013 report [2] the spoilage of food that affects all the chain from the farm, markets to homes, causing loss of incomes for farmers and shortcomings in food supply. Therefore, the means for food conservation are critical and represent a massive effect on economies as well as an improvement of public health and food accessibility.
Let us analyse the current solutions proposed by other inventors and entrepreneurs. The Rolex awards gave a prize to the Nigerian teacher Mohammed Bah Abba in 2001, for the invention of an evaporator refrigeration system called pot-in-pot refrigerator.
Pot-in-pot refrigerator Source: Wikipedia
The working principle of such kind of refrigerators are explained in Wikipedia [3] but basically it is a system formed by two ceramic pots which includes sand and water between. The evaporation of water draws the heat from the inner pot. Abba’s invention generated huge positive additional effects on the rural Nigerian population:
. Increased profits from food sales: As there is no rush to sell food to avoid spoilage, farmers are able to sell their produce on demand and can command higher prices. . Increased opportunities for women: Women can sell food directly from their homes, decreasing their dependence on their husbands as sole providers. Also, because girls traditionally take food to market to sell, and because food in the refrigerator stays fresh long enough that they can go to market once a week rather than once a day, there is more time for them to attend school. . Rural employment opportunities: Farmers are able to support themselves with their increased profits at market, slowing the move into cities. In addition, the creation of the pots themselves generates job opportunities. . Increased diet variety: Food is available for longer into the year. . Others: The ability to store vaccines and medicines that would otherwise be unavailable in areas without refrigeration facilities
Another awarded inventor from United Kingdom, Emily Cummins developed in 2009 the same concept but with a little more sophistication [4].
Emily Cummins’ concept
Although Mohammed and Emily’s refrigerators generated important advances in Nigeria and Namibia respectively, their inventions have very limited refrigerating capacities as well as little food storage potential. In particular, Emily’s invention seems to be better suited for transporting vaccines and/or medicines than for food storage. On the other hand, the two inventions have a difficult practical use because the inventions do not allow the organization of contained food. Therefore, if one needs to extract a tomato from the bottom of the fridge, he or she must first extract the upper vegetables. In addition, the weight of the vegetables can crush the bottom vegetables and this is not convenient. I propose to develop a new design for a refrigerator which can be build using the retired gas cylinders and that will allow increased cooling capacities and a better capacity and organization for food storage.
Low cost absorption refrigerator Two vessels and two liquids integrate the most basic variant of absorption refrigerator, one liquid is a refrigerant with a low boiling point and the other is the absorbent in which the refrigerant can be dissolved.
The most basic absorption refrigerator was known as IcyBall [5][6], and widely used in the old rural America (1920 - 1940) without electricity supply. Some of the original 80 years old IcyBalls are still being used by amateur collectors and nostalgic people demonstrating its fully functionality, which means it is a robust and reliable system. I have attached the link of a user manual from its old manufacturer [7].
US patent 1740737 (1929)
IcyBall refrigerating a container with food The principle of operation is very simple; there are two vessels, the “hot vessel” and the “cold vessel”, communicated by a U shape pipe. In the “hot vessel”, there is an initial mixture of water and ammonia, the “cold vessel”, in principle, should not contain anything. For starting its operation, the “cold vessel” is externally submerged in water while the “hot vessel” containing the mixture of water and ammonia is slightly heated. As the temperature rises in the “hot vessel”, the solubility of ammonia in water decreases, the pressure raises and therefore the ammonia boils and pass through the U shape pipe to the “cold vessel” that is externally submerged in water. As a result, the ammonia is condensed inside the “cold vessel”.
When the “cold vessel” is fully charged with liquid ammonia, the device is turned around, placing the “hot vessel” in the water bath. As the “hot vessel” cools, the pressure in the system falls, eventually dropping to the point where the liquid ammonia in the “cold vessel” begins to evaporate, thus, the ammonia returns through the U shaped pipe to the water, and in consequence, the “cold vessel” begins to freeze. Finally, the IcyBall is just placed into a cabined for food refrigeration as showed in the picture above. The system provides refrigeration for approximately one day until the heating process described is repeated again.
In average, an IcyBall using ball shaped vessels of approximately 20 centimetres of diameter, filled with the mixture in a proportion of 57.2% in weight of water and 42.8% in weight of ammonia, should be able to provide a temperature range of 2 to 8 °C in a (approximately) 70 x 40 x 90 centimetres cabinet for at least 24 hours.
Constructive details Before starting with the explanation of the constructive details, it is important to prove that it is possible to build a homemade modern IcyBall using old gas cylinders. According the compatibility tables developed by Air Liquide Corporation, the water – ammonia mixture could be contained in vessels made of aluminium, steels (ferritic, carbon, stainless…) and the plastics PTFE, PCTFE, NYLON, EPDM, PP and IIR without problematic consequences [8]. A quick search reveals that in fact, some inventors built homemade IcyBalls using old propane cylinders in combination with fire extinguishers [9]. In principle, and according the challenge details, such gas cylinders are made of special alloy steel, which means it is a viable vessel for using ammonia. Another feature of the tanks described in the challenge is that they are designed at 34 bar of top pressure that is far enough for our purposes. An IcyBall based on water – ammonia when heated correctly should produce maximum pressures in the range of 14 – 17 bars.
The photo is a home built IcyBall built by an inventor of Florida out of an old propane tank and fire extinguisher for less than $100
As you can see, the basic design is simple. The system should include two vessels made of the removed gas cylinders of a similar size (Or one gas cylinder and another kind of vessel). The upper valve of the gas cylinder is then removed; one of the cylinders should be filled with the mixture water and ammonia. The filling process should proceed carefully because ammonia is a toxic gas. However once the ammonia is properly sealed inside the system, the risks for the users should be similar or lower than the risk in some refrigeration systems in a developed country like USA or Canada or any other country in Europe. In USA, there are IcyBalls that after 80 years still maintain its original mixture (The system does not require special maintenance; in consequence it is most robust and reliable than other refrigeration systems based on compressors and moving parts).
Of course, if the gas cylinder is corroded or in extremely bad conditions it could not be used. However, the cylinders with leaking or damaged valves (which are not necessary for the system), dents and the like could be safely used.
In the place of the removed valves, the U shaped steel pipe should be welded. In the patent picture above, the U-pipe connection is different, but such connection in essence does not affect the system’s function, the two variants are perfectly viable [see patent description 10] [11]. Not all the parts showed in the patent are actually essential.
The inner tubes showed in the “hot vessel” of the patent picture (left vessel) and numerated as 10, 16, 15 and 13 constitute the check valve. The check valve function is to allow the pass of gas ammonia during heating to the “cool vessel” and to bubble the ammonia inside the water during the cooling for a better absorption, this is why we have a submerged tube 10. Without this check valve, the IcyBall would not work properly. I have attached a simpler design and a good explanation about the principle of operation of the check valve [12]. Of course, other variants are possible.
About the heating sources, a simple kerosene flame is a viable solution but again, other variants are possible. For example, one could use solar heat concentrated with lens like in some university projects [8] or use solar panels to generate electricity for heating. When heating it is important to control the process, the control could be done as in old IcyBalls measuring the quantity of kerosene in the heat source (if you use kerosene) or it is possible to install a whistle like in teakettles in order to measure the pressure inside the ball.
The details of the IcyBall design can vary a lot, thus there are many possible variants. Such variants should be specified depending of the resources of the country in which the system is manufactured. For example, it would be possible to look for another non-toxic refrigerant instead of ammonia. Alternatively, it would be possible to develop another way the regenerate the system without moving the vessels inside a water bath, which requires a certain degree of physical strength.
The manufacturing process will require a certain degree of manual skills, but such skills can be teach and learned by any common worker. In principle, it would be required good welding skills and knowledge about ammonia manipulation. Such skills can be mastered by one individual.
The basic list of materials has been explained along the submission, but in general, it would be required water, ammonia, the retired gas cylinders, steel tubes, valves and a cabinet. A detailed description of costs would be difficult but in USA, the price of ammonia is around 4 $/kg, the price of water could be considered free of charge, the price of gas cylinders are assumed to be free in this situation, the piping, valves and welding would be the most expensive and probably 50 $ as much. On the other hand, the cabinet would add some costs in the final product.
In theory, an amateur inventor building a system like the one I described here in USA should invest around 100 $ to 200 $. Of course, if it is possible an industrial production of millions of fridges, the costs will be much lower. In contrast, a pot-in-pot refrigerator in Nigeria costs around 1.30$ but its capacity for storing food and refrigeration is much more limited. A bigger and cooler fridge will allow to increase the food production of the farmers without spoilage problems. As well as conserve more delicate foods like fish. In addition, this system could be used to produce ice that could have other useful applications.
The bigger size of the system proposed holds more subtle advantages, for example like happened in middle ages Europe, two or more families could purchase one tool in order to divide costs, in this case, two families could share one refrigerator.
Project continuation If this solution is selected, I would like to continue working on the project’s details. This proposal could generate a massive impact in Sub-Saharan countries but it requires further specification.
Checklist Irreversibility of the new non-LPG cylinders – proposed solutions must describe a new application that makes it impossible for defective and unsafe cylinders to be returned to use as LPG cylinders. That is, the transformation into non-LPG cylinders must be absolute, one- way, and irreversible. Solutions that additionally address the refurbishment of cylinders (if any) must guarantee that the proposed solution meets safety standards, making sure that there are no possible leakage / noncompliance.
The application is completely new, and when manufactured the gas cylinders cannot be used again as LPG cylinders.
Value – the solution must generate a high-value application for the recycled cylinders. Solutions that lead to high income, as long as other societal benefits (e.g. job creation, reduction of inequalities and poverty, etc) will be preferred. At a minimum, proposed solutions must be more cost-effective than the current solution (i.e. cleaning the cylinders and sending them to the hydraulic press for recycling the steel).
As in the pot-in-pot fridge in Nigeria, this submission has the potential of huge economic and social benefits.
Geographical context – the proposed solution must be adapted to the social, economic and cultural contexts of sub-Saharan African (SSA) countries.
Yes, it is.
Environmental impact – the solution must be environmentally more sustainable than the current solution (i.e. cleaning the cylinders and sending them to the hydraulic press for recycling the steel)
The refrigeration system is very sustainable. In addition, some countries like Ghana use refrigerators (when electricity allows it) based on environmentally harmful CFCs which are banned in developed countries. Capacity and inventory – Country A is used as an example of a target country, but solutions should have the capacity to deal with some degree of uncertainty. With that in mind, your solution must give an answer to the greatest part of the inventory (not specific to a cylinder size, material...). The bigger the capacity to deal with the inventory (approximately 1.5 million old cylinders to be removed from circulation, amongst a pool of 3 million that need to be checked for safety) the higher the solution will be rated in this requirement.
This solution could potentially deal with most of the cylinders. Millions of fridges can be produced.
Local resources – the solution should rely on technical and human resources that are available in SSA and use African countries equipment and labor force (nice to have).
In general, the solutions could be implemented using the resources in such countries. Of course some skills are required by the workforce but should be learned easily.
References [1] Creamer Media. Africa’s energy problems threatens growth, says Nepad CEO 12 November 2009
[2] Rockefeller Foundation. Waste and Spoilage in the food chain. https://www.rockefellerfoundation.org/app/uploads/Waste-and-Spoilage-in-the-Food- Chain.pdf
[3] https://en.wikipedia.org/wiki/Pot-in-pot_refrigerator
[4] http://www.gizmag.com/solar-powered-fridge-emily-cummins/10990/
[5] http://crosleyautoclub.com/IcyBall/crosley_icyball.html
[6] https://en.wikipedia.org/wiki/Icyball
[7] http://crosleyautoclub.com/IcyBall/IB_Manual/operations_manual.html
[8] http://www.solaripedia.com/files/1113.pdf
[9] http://crosleyicyball.com/index_files/Page1030.htm
[10] http://crosleyautoclub.com/IcyBall/IB1740737/IB1740737.html
[11] http://crosleyautoclub.com/IcyBall/IB1811523/IB1811523.html
[12] http://crosleyautoclub.com/IcyBall/HomeBuilt/HallPlans/IB_Directions.html
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To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/legalcode This work was supported by the UK Department for International Development, from the UK government, and the Ideas to Impact programme managed by IMC Worldwide Ltd. [email protected] ideastoimpact.net @ideastoimpact