FreeFEM software: ready for summer! DIY heat

Energy saving, cooling a house, Passive housing

I’m a total noobie what comes to construction technology. However, my mind is curious one, and I’m open to experimenting.

In this series, we’re going to:

  • get familiar with FreeFEM modeling
  • understand the physics of heat in housing
  • model a house in FreeFEM
  • start measuring actual temperature readings
  • see how changes in ventilation, opening or closing windows changes the inside temperature
  • draw conclusions as to how efficient passive energy houses can be in terms of convenience and energy use

Today I thought: why couldn’t I just start testing around and observing, what happens if I tweak a little bit of here and there. I installed FreeFEM, a finite element modeling toolpack. FreeFEM is a free software, available to all your usual suspect platforms (Windows, Mac, Linux). FreeFEM allows me to first define the structure of a house; then
simulate the heat transfers happening within.

My goal is to

  • first understand how heat behaves in our house
  • second, understand how the temperature can be
    adjusted using passive means; not A/C, but some
    alternative methods
  • third, how much can these passive adjustment
    control the temperature, in, say during heat of the summer!

Simulating the Sun as heat source?

One of the biggest heat sources is the Sun. It behaves
in a way that is dependent on 3 things, basically:

  • surface material, which the sunshine hits
  • time of day
  • time of year

Sunshine hits surfaces, and this surface heat is
transferred mainly via conductive transfer deeper
towards the inner elements of the house. Sunshine through
windows is also a great contributor to heat inside the
house. In both cases there are two factors at play

  • surface material
  • incidence angle of the sun

The energy from sun is approximately 1300 watts per
square meter. 1300 watts is quite a lot! Think of it
this way: microwave oven, at full throttle, gives about
900-1500 watts. A sauna is 4000 – 5000 watts. So you
could say Sun is like a mini, always-ON microwave oven.

Sunshine is approximately “uniform” heat source, however
the incidence angle depends on your place on Earth. On equator,
sunshine is direct, and heats a lot. On poles of the Earth (north and south),
sunshine hits in a very oblique angle, and thus its power
is diminished.

The sun’s behavior as an energy source is well-known, tabulated;
but it’s just that you need to plug it to FreeFEM somehow —
as a function, or use tabulated data.

Next part, let’s get going with modeling a house in FreeFEM!

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