Should you keep your ice box full to save energy?
- Category: Refrigeration
Here's a fact: Heat travels in one direction only; from warm to cold. So if a temperature difference exists between two items, the warmer item will lose heat to the cooler item; so the warmer item gets colder, the colder item gets warmer.
Simply put, when we put warm beers into a cooler of ice, we don't actually cool down the beer as much as warm up the ice! When heat leaves the beer for the ice, the beer gets colder as a result, and soon the contents are all at a wonderfully refreshing 32F temperature. And thanks to the laws of science and beerology, everything will stay that way until all the ice has melted and the beer has been consumed.
And now here's a conundrum: Should you endeavor to keep your fridge and freezer as full as possible in an effort to save power usage?
Cracked solar cells and heat damage
- Category: Solar
Did you know that there is an official measurement for a hairs breadth? Well, according to my conversion tables:
one hairs breadth = 100 microns (micrometers, millionths of a meter)
So the thickness of a regular silicon solar cell, at around 200 microns, or 2 hairs breadths, is pretty darn thin! And when you consider that the SunPower® back-contact cells that are used by Solara and Solbian are even thinner, at about 1.5 hairs breadth, and that these cells are essentially glass in nature, you will no doubt appreciate that they will need careful handling.
The SunPower® cells used in Solbian flexible panels are high grade cells that are purchased guaranteed free from physical defects, but careless handling in storage, shipping or on site, together with improper installation, can initiate cracks in the cells which will be invisible to the naked eye.
In the majority of applications these cracks will be comparatively harmless and may not cause any problems other than a small loss of power, but
How to Kill a Battery
- Category: Battery
We spend considerable time and effort trying to help boat operators understand how to look after their batteries, but we still hear of way too many premature deaths. So in an effort to get the message across from a different angle, we offer the following advice on how to inflict serious harm and punishment on expensive batteries without really trying.
Simply put, there are three main types of abuse you can employ to kill or maim your batteries:
- Excessive heat
- Physical damage (including vibration), and
- Poor charging routines
The first two I hope to be self explanatory, but the third requires some detailed explanation.
Flooded lead acid batteries, including AGM's, don't like being left for extended periods in a partially charged state. Doing so allows some of the lead sulfate crystals that form naturally on the negative plate during the discharge process to harden to the point where they can't then be dissolved the next time the battery is charged. This is known as sulfation which leads to an increasing loss of useable capacity as more and more crystals harden.
Variable Speed Refrigeration and Air Conditioning Compressors
- Category: Refrigeration
I recently had an air conditioning system replaced at my house. Out went the old energy hog with a noisy, fixed speed compressor, and in came a high efficiency unit with a quiet compressor and fan, both of which run at variable speeds. So, today’s question is: Why does varying the compressor speed increase efficiency, and how is that achieved?
Golden Rule: The longer and slower a compressor can run, the more efficient it will be
Efficiency in refrigeration and air conditioning systems is measured as a ratio of power out to power in, and can be in several forms. The Energy Efficiency Ratio (EER) is the ratio of output cooling energy in Btu’s to input electrical energy in watts under certain fixed conditions. So a system with an EER rating of 10 will produce 10 Btu’s of cooling for every watt of power consumed under the specified conditions. The Seasonal Energy Efficiency Ratio (SEER) that is used in commercial and residential equipment is similar to the EER, but is assessed over time and under varying conditions.
When a fixed speed compressor is operating under light-load conditions, i.e. nighttime, cool weather, etc., a fixed-speed compressor will be running for short spurts and do a lot of cooling in a hurry, which is inherently very inefficient. If we were to be able to slow the compressor down during periods of light load, the system would run longer and be more efficient overall, but would still have the required capacity available for high heat-load conditions.