You are a farmer, a rancher or you live in rural areas. You want to accumulate heat from a solar thermal system and not lose this energy transferred to the hot water. Let me tell you about the teapot and the dinosaur.
British have a reputation for knowing how to drink tea: hot. Thus English teapots are the most efficient to keep the tea hot as long as possible. The secret is the sphere, which is the three-dimensional geometric shape with lower external surface related to inside volume.
Compare 1 liter inside an spherical teapot with 1 liter in a very narrow botle. The tea will cool much faster in the bottle because it has very high surfacet loss heat compared to the area of the kettle. Try it.
Why dinosaurs grew so large? Reptiles need to capture solar heat to increase their metabolism and consume the stored heat at night. If they lose too much heat, or weather becomes colder, they can not walk at night. When the carnivorous dinosaurs began to increase in size, they keeped heat better and could hunt at night. Herbivorous dinosaurs were forced to grow also in weight to maintain mobility at night. So, increasing mass, accumulated heat will be directly more preserved. Why?
This is again a relationship between the internal volume and external surface. Larger the volume is, which increases the cube (cm3 or m3), less ratio represents the outer surface, which increases squared (cm2 or m2). Think for a moment in any hot object: Which is cooled faster, the smaller or the largest? Bigger it is, more it keeps the heat.
If we have to maintain heat from the water for a long time, larger is the volume, less there will be heat losses.
Practical application in solar thermal accumulation
Any engineer, solar thermal expert, will say, rightly, that the most suitable form for a solar tank is the cylinder, as it allows the correct stratification between cold water inlet below and hot water outlet on top. Also correctly, the volume has to be appropriate for the solar heating cycles and consumption, for example daily or weekly maximum.
I would like to explore how to heat seasonally, in summer, and store with minimum heat looses for winter use. Only in rural or agricultural activities enough space is available to accumulate large quantities (the dinosaur) with a spherical shape (the teapot).
By the way, have you seen the diplodocus looks like a teapot? It add the two advantages: high volume and sphere form.
One day will develop in greater depth the issue of seasonal heat accumulation. For now, what do you think of this post? I like debate. You know more than me.
- Solar Panel: Photovoltaic Module or Solar Thermal Collector? (albertcampi.me)