Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 401

7.3.8 Redesign

To achieve the net-zero energy target, the following redesign options have
been considered (Cellura et al. , 2011a):

1. Replacement of the PV panels with more efficient ones (19% module
efficiency, electrical properties are listed in Table 7.9 );
2. Replacement of the GHP with a more efficient model;

3. Elimination of the GHP heat exchanger and direct connection with the
main pipeline of the fluid heated/cooled;

4. Modification of the composition of the roof in order to get a smaller U
value (0.15 W/m 2 K);
5. Different volume of the main storage tank to evaluate effects on GHP
consumption;
6. Integration of a night setback on the PID temperature setup;
7. Addition of blinds, on the south-oriented windows, working in the
hottest hours during summer season, if occupancy schedules are set to
0.

Table 7.9 PV modules electrical properties

On-site Redesign

P max [W] 175 240

V mp [V] 36.40 43.70

I mp [A] 4.67 5.51

OPEN circuit V [V] 43.50 52.40

Short circuit I [A] 5.20 5.85

The simulations yielded the following results (also summarized in Table
7.10 ) :

1. Substitution of PV panels with a 19% efficiency model, the forecasted
energy yield (TRNSYS simulation) would be about 38MWh. This
solution would allow the electrical loads to be completely met;
2. The design COP value of the GHP was 4.6, but the monitored data
showed a smaller value. This is due to the inefficiency of the plant and