By Josh Perry, Editor [email protected]
Institution of Mechanical Engineers (IMechE) fellow Michael Reid recently published an article on the institution website explaining his process for developing a prototype refrigerator that runs on solar heat and will assist people who live off the electrical grid.
The solar fridge. (Michael Reid/IMechE)
Reid was focused primarily on India, where more than a billion people live but more than 600 million live in cities far away from crops are being grown. Unlike in other locations with consistent electricity where crops that have been harvested can be refrigerated to preserve freshness during travel to market, Reid explained that as much as 50 percent of crops is wasted before it gets to the cities.
The design starts with a gas flame system that has a closed system of steel pipes. The water inside includes a solution of ammonia. When heated to a certain level, the ammonia boils out and is condensed in a cooler area with a hydrogen atmosphere.
“The law of partial pressures says that, if you introduce one gas into the presence of another, it will behave as if the other gas is not there,” Reid explained. “It boils away – and when ammonia boils in a vacuum it goes down as far as -38°C. That’s where the cooling goes on. You end up with a mixture of ammonia and hydrogen gas, and you reintroduce that to the water, which reabsorbs the ammonia and purifies the gas mixture into pure hydrogen.”
Read the full article at http://www.imeche.org/news/news-article/how-i-built-a-fridge-powered-by-solar-heat.
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