Saturday 7 September 2013

Saving energy, new fridge design based on a freshness sensor

Sometimes the best inventions come when we forced to a deadline or threat. A Microsoft manager used to say to me, if a "gun was placed to my head", how would I solve the problem, (in one hour). This worked very well in focusing the mind when I worked there.
 Moving on to 2013, I was approached last week with a 2 day deadline  on grant application (£50k) for "Green" issues, reducing carbon footprints,  and saving power in the home, a perennial problem with many people seeking solutions. Could I design something?  There are numerous government grant offers for solving these problems. The incentive is getting a grant to design some useful technology for society, getting it manufactured  and get paid for delivering a  result, e.g. a working prototype.

I have some research experience in smell research as here.
I am also fascinated by the sense of smell of our cats and dogs.
So this blog is an excuse for a picture of my cat Dot's nose after her mouth surgery in Feb 2013. More here about the cat's Jacobson's organ.

Click to enlarge

One idea of  interest is saving power in the home, with appliances that are switched on for 24 hours per day, e.g. our fridge. The fridge design needs a rethink to save power. Why do we have a fridge? It is not just for cold beer and chilled wine !
We need our fridge to preserve fresh food food, stop bacteria growing, and to stop food poisoning. We are advised to set our fridge to 4 Centigrade (40 Fahrenheit)  for these reasons. However this low temperature can kill  the taste of, for example fruit,  a top chef told me not to store tomatoes in a fridge, so I have not for many years. We can test for food passed it's best buy date by smelling it.(Don't trust me on this). What if you are a vegetarian, you may not have animal produce, do you need a setting of 4C ?   So we could design a fridge with a gas sensor to detect freshness,  rather than temperature sensing and maybe fridge temperature a bit higher and so save electricity? The modern  gas sensors can detect gas  to 1 Part Per Million (ppm) the start of  decaying food by measuring the ammonia, hydrogen sulphide, methane etc of food that is starting to putrefy. Enjoy this Wikipedia article on decaying food. There are new optical gas sensors but also the low cost traditional gas sensors.
The sensing of imminent decay can be used to control the temperature. A microcontroller can measure the gas level and provide an audio link or control to an external mains controller for the fridge.
The food obviously needs to be unwrapped for the gas sensor to work, but this is fine as sometimes the forgotten piece of unwrapped food in the back of the fridge is the culprit.
Some people do not have a sense of smell and this sense also fails as people get older.
Re the power saving, if we can keep our fridge at 12C (perfect temperature for some white wines?) and our vegetable retains some flavour, this all contributes to saving power in our fridges.

My warm salad, smoked salmon, olives, and tomatoes 

The engineering design with a microcontroller should be routine, gas sensor samples every hour or so so an AA battery should  last a year. We can add temperature measurement. We can measure how full the fridge is by an ultrasonic echo sounder, (full fridge, but not overloaded is more economical). An audio alarm for when the fridge door has been open too long for viewing?  I feel the call of programming an Arduino again...

And yes, radio signals (to the mains controller if needed) do work transmitted into and out of a fridge, I tested it on my mobile phone.

This may be more of a research project, a possible grant application, but feedback and shows stoppers welcome. If a 20% reduction in power consumption on the fridge can be achieved that is a start.

Useful to know,  preferred storage temperatures:

Champagne temperature 10-15C

Chicken 4C more here

Tomatoes 13C

Eggs varies from 4C ?

Wine storage

Lyndsay Williams

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