Topic Tuesday #50 2013/07/02 - "CHARGE!!!"
CHARGing you batteries is not the easiest thing to do some days. It gets especially difficult when you do something unusual. For instance you may have seen the MIT/Wilson Solar Grill.
This implementation is unique in the way is stores energy, which is certainly different from the way a cell phone or laptop stores power. This configuration (which has not actually been constructed to my knowledge) uses a fresnel lens to magnify and focus the rays of the sun to melt a lithium nitrate substrate. The melted lithium nitrate, due to its phase change reaction, is able to release its thermal energy for longer periods of time and at higher temperatures than other methods up to now. Heat is then redistributed through convection, which allows for outdoor cooking and heating homes. This method is referred to as "latent heat storage".
Obviously this is a unique application that requires a specific set of criteria. This could also be used to provide electric power or boil water for steam applications.
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| Peltier element |
Remember any time you have a change of temperature you can utilize that to create power as the heat is exchanged and returns to a neutral state. Peltier coolers use power to create heat, which in turn creates a cold side. With an application such as this, derivatives of that technology can turn a heat source, into power. If done creatively, a refrigerator too.
Batteries, and power sources in general, are complicated things. The design may be simplistic, but usually a power supply is designed to fit an application. Some things to consider:
Capacity (Amp Hours)
Weight
Size (Physical Dimensions)
Discharge Rate (Time to Empty at designed load)
Charge Rate (Time to Charge, when under load and not under load)
Charge Cycles (number of charge/discharge cycles before needing to replace)
Operating temperature range (Affects charge and discharge rates. Batteries can catch fire and explode under the "right" circumstances, like being embedded in a cooking appliance like the solar grill)
Architecture of storage media: Lead-acid? NiCd? NiMH? NiZn? AgZN? NaS? Lithium ion? - and so forth.
Longevity and recyclability:
Obviously what the battery is made of has far reaching implications for the ability to recycle them. Lithium is rare, expensive, and in high demand. Lead Acid (car, marine, UPS batteries) are low cost, high weight, and readily recycled into new batteries given the proper facilities.
So, thank your local engineers for building all this stuff we take for granted all the time, and keep the innovation alive by encouraging our youngsters to... play with electricity, fire, water, light... and anything that interests them. Who knows what problem they might solve.