Simulation assessment

The effect of the significantly higher performance levels of COAX 390 (heat insulation and heat transfer ability) has been tested in a simulation in Polysun. The experiment has been carried out for a solar thermal system with COAX 390 as well as two or three flat collectors PLANO 21 (figure 4) in comparison to a conventional tank with the same collectors (cli­mate Wurzburg).

Table 1 shows the different parameters. The values for heat losses of the connected pipes are taken from /1/.

Parameter

Conventional tank

COAX 390

Thickness insulation

100 mm

125 mm

Thermal conductivity insulation

0.049 W/(m K) (PU-foam, soft)

0.033 W/(m K) (LE-EPS + air)

Losses connections boiler supply, boiler return, cold water

10 W/(50°C — 20°C) = 0.33 W/K

0,9 W / (50°C — 20 °C) = 0.03 W/K

Losses connection hot water

15 W / 30K = 0.5 W/K

0.9 W / 30K = 0.03

Without even considering the additional yield through stratification, the COAX-system of­fers with the two tested factors alone a higher solar yield of 8 % or 14 %, respectively.

2. Conclusion

The substantial performance improvements of COAX 390 (achieved by stratification, heat transfer values, insulation) in comparison to the market standard leads to the conclusion that — when using the same collector area — a significantly higher energy yield can be achieved.

On the other hand, the cost for this tank is comparable to high-quality yet technically con­ventional tanks, which should lead to an extremely good price/performance ratio for the complete system.

3. Literature

/1/ Meitner, R., Siegemund, A., Leibfried, U.: Mit Mehrtagesspeichern gegen Warmev — erluste, Moderne Gebaudetechnik 10/2001

Tr_COAX_14_SYMPOS_as. doc