It's Sunday so I propose a funnier, still "sciency" article for today. We all know that the Internet was created to help disseminate cat pictures by the military at first1 and then its potential was discovered by the civilians, to also disseminate cat pictures AND movies, but further scientific research into cats brought us to the advent of cat studies. One of these studies is what I am trying to cover in depth today.
He has some idea of what is going on, clearly! Source
Cats as renewable energy
The world's supply of cats is close to 600 million small cats, although other estimates are much more generous, as much as close to 10billion felines living. We are only talking of the small, domestic cats as wild cats are not as convenient to live with. As there is a big problem with strays and neutering, and many agencies are proposing a reduction in the number of stray felines, science can only intervene and propose a viable solution to this problem.
Nobody is a fan of cat suffering (apart from a few members that society and psychologists somehow seem to filter out, according to this evidence), so I will not cover the subject of using cats as conventional fuel. But, even without being used as fuel, cats have a high potential energy output, as almost everyone knows that having a cat "monorailed" on top of your belly is an energy rich process.
We will use "The Engineering ToolBox", a website I gave you earlier in my series, to find out that heat emission from animals can be estimated using the formula:
H=6.6 m0.75
where H is the total heat emission (in BTU per hour) and m is the mass of the cat in pounds. So a big fat cat would produce more heat. Cats range usually from 7 to 12 pounds, so we will use 12 in our calculation. Hence we have 45 BTU per hour. This is 1080 BTU per day. For the ones driving on the "right" side of the roads (see what I did there?), that is 0.31 kW on a daily basis from a barely obese 6 kg cat. I am using the same formulas I gave you in the previous article, mind you. This is just heat energy given off by the cat while not engaging in any activity, but we do know that cats are eternal idlers so not much more is expected from them aside from eating, idling and pooping. At least at this point in the calculation.
We know that our simulation needed 8 kW during winter, so in order to heat our energy-efficient house we would thus need
8 kW / 0.31 kW = 25.8 cats.
For noise abatement I would advise 26 cats, since getting that 0.8 of a cat would indeed get very noisy for you, the neighbors and generally, the cat.
Anatomy of a cat, according to Wikipedia:
I trust Wikipedia just as the next person, but my intuition tells me there's more to the anatomy of a cat. After my observations ,this is what I came up with:
Clearly, more work needs to be done before I can claim my findings. If you think you can spot a General Fusion Reactor just sitting there, you can read more about it here.
Calculating efficiency
How much "fuel" does a cat need in order to produce that heat? First of all, an obese cat would need to eat 250-300 calories per day and be sedentary, since an active indoor and normal weight cat eats around 220-250 calories per day and obviously even more if they are outdoor, up to 280-300 calories per day, according to what my vet told me when I checked my barely obese 6 kg cat in for a regular check, last month. Since we don't want to lose any of that energy outside, we can't allow them to be outdoor cats :D so much of the problem is solved. We now just need to feed them sustenance so that they can radiate their heat.
Nutritive values for a cat, according to "Your Cat's Nutritional Needs - A Science-Based Guide for Pet Owners" are like this (100% legit guide, follow the source):
So nursing cats need an unusually large quantity of sustenance. This is something that will really affect the economy of our project so take all cats of the same sex. Plus, this will actually be good for the stray population of cats, don't buy, don't birth new cats, adopt the other strays. Give them a nice and, sic, warm, home. The not-so-little critters (since they would need to be obese) will never know they are being the ones heating up the place and will act like the jerks they are, without having a clue of the real jerks in the scheme.
Assuming an efficiency of 100%, since nobody wants to perform calorimetry on the litter box, according to some forums I previously checked and the fact that the cats don't waste energy through movement (cat movement is generally assumed to be 0, cats being more or less useless - but probably more).
26 cats eating around 300 calories per day would actually mean that the food intake needed would be close to 325 grams of protein and 143 grams of fat. Translated into cat food this turns out to be about 3 kg (6.61 lbs) of premium cat food (probably more if the food is lower quality) and costs around 12$ per day. This sums up to 312$ per month, which is actually only 300% more than what I pay on natural gas to heat the house. This makes me think of ways to reduce cost though.
Using natural food for cats
Growing mice as cat food is the initial idea I had but I have a hunch that mice are even less efficient that cats. Using a website to look for the nutritional value we find that domestic mice ("Mus musculus") weigh about 10 grams out of which 5.5 grams are protein and 2.3 grams are fat. This means that our mice-eating factory would need 65 mice a day to heat our home. We know from Havahart that "In ideal conditions, one pair of mice and their offspring can produce up to 8,000 young in one year", so this might look promising, if you have the means to keep up to 25000 mice and feed them to the cats (poor mice), since the cats are not allowed to engage in hunting or other energy-burning activities.
This is my cat being energetically inefficient while consuming an artificial Proteus from Slovenia. Interesting fact is a Proteus is highly energetically efficient.
Conclusions
- For now, heating your house using cats might not be the best tactic nor very economical, but it is possible nonetheless.
- Don't overfeed your cat. It might limit its range of movements and if it's an outdoor cat, it will prevent it from escaping a dog or fitting through a small hole when fleeing a fight, it makes its bones more susceptible to breaking and all the other problems that obesity causes in humans.
- Don't be afraid to adopt a cat. They are furry and loving and they need a home and love. They can calm you when you are moody and can offer you hours of enjoyment every day. Also, you are contributing toward saving the planet, remember, having less than 26 cats (as per my experiment - your results will vary according to how well insulated your house is) won't probably make you energetically independent, but it clearly takes you closer to that goal.
- For the ones that commented on my last article about heating saying they don't want any more heating due to the fact that they already live in heated areas of the world, I can only advise them to adopt cats and keep them outside, as it will make the outside temperature a little higher and being inside will just feel cooler :)
Sources and Further reading:
1 - no they didn't.
For calculating the R-value of a cat:
https://books.google.ca/books?id=SdJtYtN4wXEC&lpg=PA65&pg=PA65&hl=en#v=onepage&q&f=false - Chapter 4.2.1 "Thermal Resistance Term for the Hollow Cylinder and Chapter 4.3 "Steady-State Heat Conduction in a Slab with Internal Heat Generation". Looks like a simplified definition of a cat.
Engineering forum that calculates the joules output of a domestic cat.
