Alternative Fake News Facts
- Category: Solar
After several discussions recently with customers contemplating adding solar to their electrically powered vessels, there is still a lot of confusion about exactly how much power can be realistically expected from solar panels. I have an inkling that these customers are so honed in to watts and kilowatts from their dealings with propulsion that they assume that all watts are equal.
But solar watts are a different animal.
The watt is a measure of power and is normally derived electrically from multiplying volts times amps (W = V x A), or amps squared times resistance (W = I² x R).
So, using simple math, if we have a 5,000 watt (5 kilowatt, or 5kW) DC electric propulsion motor running on 100 volts, we would expect it to be drawing 50 amps at full load. If the same sized motor was designed to run at 50 volts then the current draw would be double that at 100 amps.
For reasons of wire sizing and cost of ancillary equipment we’d want to keep the amps as low as possible, so the higher the voltage the better (except for having highly lethal voltages in damp environments). As you can see, the numbers are all very simply calculated and it’s all cut and dried, and it had better stay very dry indeed!
Solar watts are different, and I’m referring here to the wattage rating of the panel(s).
Blinded by (ignoring the) Science
- Category: Ramblings
In the wake of the recent celebrations of science and scientists, I could not let the occasion go without a mention of the late Richard Feynman. For those of you not familiar with the name, Feynman, as well as being a brilliant scientist, was also a fascinating human being and a bit of a maverick who delighted in upending normal thinking and throwing the occasional curve-ball.
In his second book “What Do You Care What Other People Think: Further Adventures of a Curious Character?”, Feynman describes how he was once intrigued at how the brain tracks time, and was curious to see how accurately he could gauge one minute by counting.
- Category: Refrigeration
Are you, or is anyone you know, a Temperature Control Freak? You know the type; constantly fiddling with air conditioning and refrigerator controls and reporting on them to anyone within earshot. Well, I have such a friend.
TCF, as we will call him, has a digital temperature controller/thermostat and tells me that 39.2°F is the perfect temperature for his fridge. How he comes to this conclusion is beyond me, and quite honestly I don’t want to ask. Suffice to say that he’s happy with that after several months of laborious experimentation. And then there is the freezer ...
Now a fridge can only be between a narrow band of temperatures; too cold and it’s a freezer, too warm and it’s not a fridge. But a freezer can be kept at any temperature below freezing; from marginally frosty to cryogenic. It’s all down to how you intend to use it.
Foodstuffs will be preserved as long as they are frozen, but the appearance and edibility when thawed will differ with different temperatures and time. In Europe there is a star rating system for freezers as follows:
The Price is Right!
- Category: Ramblings
I once read in a sailing magazine something like the following: “It’s boat show time, so let’s take a look at some of the products they are trying to foist on us poor unsuspecting boaters”. As a marine vendor I was incensed to read that, and vowed never to advertise in that publication. I never did, and eventually it folded. Go figure ....
There has long been a feeling that stuff sold for boats was generally overpriced simply because it has a “marine” tag. This seemed to be more prevalent in the 80’s and 90’s, so maybe back then there were indeed a plethora of cheap and tacky items labeled as marine that would have been better suited for the kiddies backyard camping or a day at the beach.
Or maybe it’s because nowadays the internet is playing devil’s advocate and unscrupulous manufacturers just can’t get away with things like they once could. Today’s efficient means of communication ensure that when even minor issues are reported, they require a good customer service oriented response.
Now that replacement parts can be easily sent to remote locations seemingly beyond the edge of beyond, a worthwhile warranty is also increasingly important. Imagine a business getting a call from a customer on a satellite phone in mid-ocean, fretting that his fridge is running longer than it used to. “We’ve got ourselves another fridge-fretting sat-phoner” is the common cry. Oh yeah, it happens.
At Coastal we see and hear many tales of woe