Problem Statement:
Each year millions of children die from preventable illnesses because they did not have proper access to modern vaccination. The current supply and distribution chain to bring vaccines to children has a big problem with end of the chain refrigeration and overstocking.
In distribution centers, often vaccines are vastly overstocked, leading to the waste of many potentially life-saving vaccines when they need to make room for new ones. In addition, the problem of refrigeration space becomes larger when attempting to bring these vaccines to the end-users. Often expensive, bulky coolers are used, and are transported on the back of motorcycles to the end user.
In the past, kerosene or gas powered refrigerators have been seen as the most reliable option for vaccine refrigeration. These options are often infeasible and difficult to transport. In post disaster scenarios, lack of electricity or gasoline has actually made cold-chain vaccine transportation very challenging/impossible.
Solar powered refrigeration with batteries has existed since the 1980’s, but the batteries would fail often, only last 3-5 years, and are difficult and expensive to maintain. A new technology called “solar direct drive” cuts out controllers and batteries by directly connecting a refrigerator to a solar panel and using water and ice to regulate temperature.
– please define what “solar direct drive” means.
The benefits of solar refrigeration are also not limited to vaccine supply. Similar designs with few cost-reduction modifications can be utilized for cheap, effective food storage for any community.
– This is a good introduction. I think you should have an additional statement about what you’re going to do about it. Then introduce your different options so the person who reads the decision matrix knows what you’re doing. I don’t think that magnetic or magic should be options.
– Please limit your numbers to two significant figures. Shouldn’t a perfect score be 100% not 1000%?
Decision Matrix:
| Criteria | Cost of building | Cost of Use | Transportability | Services Provided | Feasibility | Time to Build | Maintenance | Learning Experience | Impress Others that We’re Cool | Total | Out of Perfect | |
| Weight | 50 | 60 | 20 | 60 | 30 | 5 | 20 | 5 | 5 | 255 | ||
| Absolute Weight | 20% | 24% | 8% | 24% | 12% | 2% | 8% | 2% | 2% | 100% | 1000% | |
| Pot-in-pot | 9 | 8 | 4 | 4 | 10 | 9 | 5 | 0 | 2 | 6.686 | 67% | |
| Peltier cooling | 5 | 10 | 7 | 8 | 7 | 6 | 7 | 10 | 9 | 7.627 | 76% | |
| Central cooler | 8 | 10 | 4 | 7 | 5 | 6 | 7 | 10 | 10 | 7.529 | 75% | |
| Compression refrigeration | 2 | 8 | 2 | 10 | 1 | 5 | 4 | 7 | 0 | 5.450980392 | 55% | |
| Magnetic Cooling | 1 | 10 | 1 | 10 | 1 | 1 | 5 | 10 | 10 | 5.901960784 | 59% | |
| ^^(bonus note: works on magic) | ||||||||||||
– the next two lines should be further down. If you look at the next few paragraphs, they are still introduction in my opinion.
Target Community:
There are a number of target communities that this product could reach.
A more expensive, reliable version would be very appropriate for implementation in rural clinics that need consistent, reliable cooling for medicines and vaccines that is always at 2-6˚C. This version could implement better insulation, such as vacuum insulation and more expensive, reliable PCMs
-please define and describe what this is and give an example.
that can guarantee an exact temperature range. This version could also be modifies to increase its transportability, allowing rural communities to reached by medical care workers.
please be mindful of typos.
There is a significant need for this kind of device. In the past, cold-chain vaccine transportation that relied on gasoline powered refrigeration trucks has failed (Haiti, 2012). While some direct-drive solar refrigeration exists, the current devices are expensive and very bulky.
The refrigeration technology, however, is not limited in cost or scope to just clinics and vaccines. A nearly identical unit that uses cheaper, yet still functional insulation (such as hay) and cheaper vessel components (such as clay pots) could offer very effective refrigeration to any community. This cooler would offer much more reliability than traditional pot-in-pot refrigeration.
– did you already say this above the table?
The World Health Organization conducted three case studies for solar direct-drive vaccine refrigerators and vaccines in Tanzania, Kenya, and Colombia:
Tanzania
- Only 28% of immunization health facilities have access to grid electricity
- 70% of health facilities rely on absorption refrigerators, which often expose vaccines to freezing temperatures and are vulnerable to gas or kerosene supply disruptions
- 12-month pilot project to evaluate three different solar direct drive(SDD) refrigerators in 17 health facilities across five climate diverse regions of the country – thank you for this great reference. Please describe the study a little more. I think they only referred to electric compressors, so using a Peltier is unique. If you’re proposing using a Peltier ThermoElectric Cooling, (TEC), then you might introduce this topic. This reference might go much earlier on your webpage.
- Temperature performance- refrigerators performed reliably without mechanical or electrical problems
- Surveys found higher levels of user satisfaction compared to absorption refrigerator
Colombia
- In northern mountains, it is too costly to operate absorption refrigeration, so some health clinics have no refrigeration at all (or only operate their refrigeration for 1 week/month, limiting immunization opportunities)
- Three years after installation, 6 SDD devices still working well
Kenya
- Several hundred SDD refrigerators have already been installed (starting in 2009)
- Health facility nurses and technicians have expressed satisfaction with the performance of the new SDD refrigerators
- minimal repair and maintenance requirements after installation
Research:
A good amount of research was done into the function and feasibility of current direct-drive refrigeration technology.
This included reviewing current solar refrigeration technologies and implementations that are used in developing communities
(Solar refrigeration for developing countries) – This page has no text.
This included review of supplier information from the following sources (Peltier manufacturer 1) (How peltiers work)
– You should have some short explanation of how a TEC works… not the science behind it, but what it is. And you can then also refer to this document.
Additionally, research into heat pipes was conducted to investigate the feasibility of displacing the heat sink with a oneway/diode heat pipe to reduce cold-loss through the peltier when off. This approach was eventually abandoned due to the considerable size of any one-way heat pipe.
– Did you drop the heat-pipe? I thought you were presenting a heat-pipe/thermosyphon on Wednesday?
Research was also conducted into phase-change materials (PCMs) which could freeze around 2˚C. (PCM research). Preliminary research has indicated that Calcium Chloride hexahydrate is a promising, reasonably priced PCM. Another option may be positive temperature organics, specifically variety organic variety A4. These organics provide better consistency at just above freezing, however, they display poorer thermal conductivity. (http://www.pcmproducts.net/Phase-Change-Material-Solutions.htm)
– I think you’ve done a good job so far. There is considerable information and a reasonable narrative. You’ve also done good work in the shop. Please improve order, organization, and flow. Also, please research the people in at least one of the areas, describing about their lives and how this might make a difference. Explain the technologies a little rather than just providing a link to a document. Also, please put captions beneath each of the figures and refer to the figures in the text. – Pete
Current Design Scheme:
Next Steps in Shop
Create functional unit using two Peltiers to establish a proof of concept. Using heat sink and thermal conductive material (thin metal wire), determine the effectiveness of two peltiers in parallel to cool a PCM (for proof of concept, water).
Team Photo: From left to right: Paige, California Grand Fir (Abies grandis), Nick, Brendan , Marco, Matt
Matt – Sociology major with minors in Biology and Microbiology. Aspiring to be a forever-student by going to medical school next year.