031. The energy balance

Figure 23. Illustration of the calculated yearly energy balance for our house. The numbers are in kWh/(m²).

In posts 027, 028 and 029 we looked at the heat flow into, and heat flow out of, the house on a monthly basis. The information is then put together for the year to calculate the yearly energy demand of the house. A depiction of this can be seen in figure 23 which is an illustration based on one generated by a software package called NOVA[1] which is what our energy planner used. Note that the diagram is not to scale!

The quantities listed in the diagram are:

- Q_iP is the heat generated by the residents.
- Q_iE is the heat generated by the electrical equipment.
- The total internally generated energy is Q_i = Q_iP + Q_iE.

- Q_S is the heat delivered by the sun.
- The total gain Q_g = Q_i + Q_S.

Only 69%[2] of Q_g can be used by the house:
- Q_g,u = 0.69 Q_g

- Q_V is the energy lost through the ventilation system[3].
- Q_t is the energy lost via transmission through the shell.

The box labelled WRG (Wärmeruckgewinn) represents the heat recovery aspect of the ventilation system. I think the term E_hww represents the electrical energy required to run the heat pump and related equipment that we have planned. Q_r and Q_L must give an indication of the amount of energy that is extracted from the environment (the air in the case of our air source heat pump).

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[1] NOVA is made by → Plancal AG

[2] I don't know how exactly this number is computed.

[3] This number is calculated using an Aussenluftvolumenstrom of 0.37 . I will try to explore this on the blog at some later point.